METHOD FOR CORRECTING PULSE WAVETRANSIT TIME ASSOCIATED WITH DIASTOLIC BLOOD PRESSURE OR SYSTOLIC BLOOD PRESSURE

Abstract

The present invention relates to a method for correcting pulse wave transit time associated with diastolic blood pressure and systolic blood pressure, and the correction method can perform adaptive correction of the irregular change of pulse wave transit time caused by blood transfusion and intravenous transfusion, vasoactive drugs, surgical intervention, etc. in a clinical setting. A pulse wave transit time is determined by a time difference of an ear pulse wave and a toe pulse wave in the same cardiac cycle, and a few correction variables are extracted based on the pulse wave features, then a total correction value is acquired to perform correction on the irregular change of pulse wave transit time. The corrected transit time can be used with available mathematical models for continuously measuring diastolic blood pressure and systolic blood pressure in each cardiac cycle in a clinical setting with high accuracy.

Claims

1. A method for correcting pulse wave transit time associated with diastolic blood pressure, characterized in that, comprising the following steps: S1) detecting a pulse wave at an ear in each cardiac cycle in real time and obtaining the following data: the height of an aortic valve closure point on an ear pulse wave denoted as h.sub.sd, the systolic time of the ear pulse wave denoted as t.sub.s, the diastolic time of the ear pulse wave denoted as t.sub.d, and the maximum height of the ear pulse wave denoted as h.sub.max; S2) detecting the pulse wave at a toe in each cardiac cycle in real time and obtaining the following data: the systolic time of a toe pulse wave denoted as t.sub.s-toe, the diastolic time of the toe pulse wave denoted as t.sub.d-toe, the maximum height of the toe pulse wave denoted as h.sub.max-toe, the time interval between the starting point of the toe pulse wave and the midpoint of the systolic peak of the toe pulse wave denoted as t.sub.ch-toe, the time interval between the starting point of the toe pulse wave and the highest point of the systolic peak of the toe pulse wave denoted as t.sub.max-toe, wherein the midpoint of the peak refers to the midpoint of arising edge turning point and a falling edge turning point at the peak; h.sub.sd refers to the amplitude of the aortic valve closure point of the ear pulse wave relative to the starting point in a cardiac cycle; h.sub.max refers to the maximum amplitude of the systolic peak of the ear pulse wave in a cardiac cycle; h.sub.max-toe refers to the maximum amplitude of the systolic peak of the toe pulse wave in a cardiac cycle; t.sub.s (the systolic time of the ear pulse wave) refers to the time difference between the starting point and the aortic valve closure point on the ear pulse wave in a cardiac cycle; t.sub.d (the diastolic time of the ear pulse wave)refers to the time difference between the aortic valve closure point of the ear pulse wave in one cardiac cycle and the starting point of the ear pulse wave in the next cardiac cycle; t.sub.s-toe (the systolic time of the toe pulse wave) refers to the time difference between the starting point and the aortic valve closure point on the toe pulse wave in a cardiac cycle; t.sub.d-toe (the diastolic time of the toe pulse wave) refers to the time difference between the aortic valve closure point of the toe pulse wave in one cardiac cycle and the starting point of the toe pulse wave in the next cardiac cycle; S3) calculating the pulse wave transit time associated with diastolic blood pressure denoted as T.sub.d, wherein T.sub.d refers to time difference between the starting point of the ear pulse wave and the starting point of the toe pulse wave, and h is the amplitude of the ear pulse wave or the toe pulse wave in a longitudinal direction, As for the pulse wave in plane coordinates, the ordinate is amplitude h, the abscissa is time t, and the pulse wave starting point is the coordinate origin, h refers to the height of a specific point on the pulse wave of the ear or toe, not just one of the toe pulse wave or ear pulse wave; h is an unknown quantity, which means the amplitude of the pulse wave at any moment; S4) by using the data in the same cardiac cycle acquired through the step S1 and the step S2, calculating a plurality of correction variables b.sub.1-b.sub.7 in the cardiac cycle; S5) according to the correction variables in the cardiac cycle acquired in the step S4, calculating a total correction value in the cardiac cycle; and S6) continuously acquiring the correction values in a plurality of cardiac cycles, and correcting the Ta acquired in the step S3.

2. The method for correcting pulse wave transit time associated with diastolic blood pressure according to claim 1, characterized in that, the total correction value in the step S5 is $B=\underset{i-1}{\overset{7}{.Math.}}{b}_i;$ where B is the sum of the correction variables b.sub.1-b.sub.7,b.sub.i is the i-th correction variable.

3. The method for correcting pulse wave transit time associated with diastolic blood pressure according to claim 1, characterized in that, in the step S6, the correction values in 8 cardiac cycles are continuously acquired; the corrected value of T.sub.d is T.sub.dmb, which is calculated by T.sub.dmb=T.sub.dm(1−B.sub.m), where T.sub.dm is the average value of T.sub.d for 8 cardiac cycles $T_{dm}=\frac{1}{8}\underset{i=1}{\overset{8}{.Math.}}{T}_{\mathrm{di}},$ T.sub.di is the T.sub.d in the i-th cardiac cycle; B.sub.m is the average of the total correction value of 8 cardiac cycles, B.sub.i is the total correction value under the i-th cardiac cycle, wherein $B_m=\frac{1}{8}\underset{i=1}{\overset{8}{.Math.}}{B}_i,T_{dm}=\frac{1}{8}\underset{i=1}{\overset{8}{.Math.}}{T}_{\mathrm{di}},$ B.sub.i is the total correction value in the i-th cardiac cycle, and T.sub.di is T.sub.d in the i-th cardiac cycle.

4. The method for correcting pulse wave transit time associated with diastolic blood pressure according to claim 1, characterized in that, the first correction variable b.sub.1 is calculated by the following formulas: if d.sub.1-b≤k.sub.sd-m-0≤d.sub.1-2-b, then b.sub.1=(d.sub.1-2-b−k.sub.sd-m-0)×0.4; if k.sub.sd-m-0<d.sub.1-b, then b.sub.1=24×0.4; if k.sub.sd-m-0>d.sub.1-2-b, then b.sub.1=0; wherein d.sub.1-b=74 to 82, d.sub.1-2-b=98 to 106, and $k_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}\mathrm{hdt}}.$

5. The method for correcting pulse wave transit time associated with diastolic blood pressure according to claim 1, characterized in that, the second correction variable b.sub.2 is calculated by the following formulas: if k.sub.sd-m>(d.sub.2-b+(age-14)/15/100), then b.sub.2=(k.sub.sd-m−(d.sub.2-b+(age-14)/15/100))×0.5; if k.sub.sd-m≤(d.sub.2-b+(age-14)/15/100), then b.sub.2=0; wherein d.sub.2-b=1.33 to 1.43, age is age, if |k.sub.sd-m-0−k.sub.sd-m-ts|≥40 and (k.sub.sd-m-0+k.sub.sd-m-ts)/2≥k.sub.sd-m-2, then k.sub.sd-m=2×k.sub.sd-m-2−(k.sub.sd-m-0+k.sub.sd-ts)/2, otherwise k.sub.sd-m=k.sub.sd-m-2; $k_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}\mathrm{hdt}},k_{\mathrm{sd}-m-\mathrm{ts}}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_{t_s}^{2t_s}\mathrm{hdt}},k_{\mathrm{sd}-m-2}=\frac{2t_s{h}_{\mathrm{sd}}}{{\int }_0^{2t_s}\mathrm{hdt}}.$

6. The method for correcting pulse wave transit time associated with diastolic blood pressure according to claim 1, characterized in that, the third correction variable b.sub.3 is calculated by the following formulas: if c.sub.4<k.sub.d-m-a<c.sub.5, then b.sub.3=0; if k.sub.sd-m-0<d.sub.6 or k.sub.sd-m-2>d.sub.7, then b.sub.3=0; if k.sub.sd-m-0≥d.sub.6+0.10, k.sub.sd-m-2≤d.sub.8 and k.sub.d-m-a≤c.sub.4, then b.sub.3=(c.sub.4−k.sub.d-m-a)×67/100; if $\{\begin{array}{c}{d}_6\le k_{\mathrm{sd}-m-0}<d_6+0.1\\ k_{d-m-a}\le c_4\end{array}\mathrm{or}$ $\{\begin{array}{c}{d}_8<k_{\mathrm{sd}-m-2}<d_7\\ k_{d-m-a}\le c_4\end{array},$ then b.sub.3=(c.sub.4−k.sub.d-m-a)×50/100; if k.sub.sd-m-0≥d.sub.6+0.10 and k.sub.sd-m-2≤d.sub.8 and k.sub.d-m-a≥c.sub.5, then b.sub.3=(c.sub.5−k.sub.d-m-a)×62/100; if $\{\begin{array}{c}{d}_6\le k_{\mathrm{sd}-m-0}<d_6+0.1\\ k_{d-m-a}\ge c_5\end{array}\mathrm{or}$ $\{\begin{array}{c}{d}_8<k_{\mathrm{sd}-m-2}<d_7\\ k_{d-m-a}\ge c_5\end{array},$ then b.sub.3=(c.sub.5=k.sub.d-m-a)×45/100; wherein if |k.sub.sd-m-0−k.sub.sd-m-ts|≥40 and (k.sub.sd-m-0+k.sub.sd-m-ts)/2≥k.sub.sd-m-2 and k.sub.sd-m-ts≥d.sub.3-2, then k.sub.d-m-a=(k.sub.d-m-t.sub.d.sub.-1+k.sub.d-m-t.sub.d-toe+(k.sub.sd-m-0+k.sub.sd-m-ts)/2−k.sub.sd-m-2)/2, otherwise k.sub.d-m-a=(k.sub.d-m-t.sub.d.sub.-1+k.sub.d-m-t.sub.d-toe)/2; if k.sub.sd-m-ts≤d.sub.3-2, then k.sub.d-m-t.sub.d.sub.-1=k.sub.d-m-t.sub.d−(d.sub.3-2−k.sub.sd-m-ts)×75/100; if k.sub.d-m-t.sub.d≤d.sub.3, then k.sub.d-m-t.sub.d.sub.-1=d.sub.3; if k.sub.d-m-t.sub.d-toe≤d.sub.3, then k.sub.d-m-t.sub.d-toe=d.sub.3; $k_{d-m-t_d}=\frac{{\int }_{t_s}^{t_s+t_d}\mathrm{hdt}}{t_d{h}_{\max }},k_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}\mathrm{hdt}},k_{\mathrm{sd}-m-2}=\frac{2t_s{h}_{\mathrm{sd}}}{{\int }_0^{2t_s}\mathrm{hdt}},$ $k_{\mathrm{sd}-m-\mathrm{ts}}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_{t_s}^{2t_s}\mathrm{hdt}},k_{d-m-t_{d-\mathrm{toe}}}=\frac{{\int }_{t_{s-\mathrm{toe}}}^{t_{s\mathrm{toe}}+t_{d\mathrm{toe}}}\mathrm{hdt}}{t_{d-\mathrm{toe}}{h}_{\max -\mathrm{toe}}};$ and c.sub.4=(d.sub.4+(age-14)/8)/100, d.sub.4=23 to 35, c.sub.5=(d.sub.5+(age-14)/8)/100, d.sub.5=27 to 39, d.sub.6=0.97 to 1.03, d.sub.7=1.52 to 1.58, d.sub.8=1.42 to 1.48, d.sub.3-2=1.21 to 1.31, d.sub.3=0.02 to 0.14, and age is age.

7. The method for correcting pulse wave transit time associated with diastolic blood pressure according to claim 1, characterized in that, the fourth correction variable b.sub.4 is calculated by the following formulas: if k.sub.s-t-toe>0.8, then b.sub.4=k.sub.s-t-toe−0.8; if k.sub.s-t-toe≤0.8, then b.sub.4=0; wherein if t.sub.max-toe≥t.sub.ch-toe, then $k_{s-t-\mathrm{toe}}=\frac{t_{\max -\mathrm{toe}}+t_{\mathrm{ch}-\mathrm{toe}}+400}{\left(t_{s-\mathrm{toe}}+200\right)\times 2},$ otherwise $k_{s-t-\mathrm{toe}}=\frac{t_{\max -\mathrm{toe}}+200}{t_{s-\mathrm{toe}}+200}.$

8. The method for correcting pulse wave transit time associated with diastolic blood pressure according to claim 1, characterized in that, the fifth correction variable b.sub.5 is calculated by the following formulas: if k.sub.s-m-toe<d.sub.9, then b.sub.5=0; if k.sub.s-m-toe≥d.sub.9 and k.sub.s-t-toe≥0.8, then b.sub.5=k.sub.s-m-toe−d.sub.9; if k.sub.s-m-toe≥d.sub.9 and k.sub.s-t-toe<0.8, then b.sub.5=(k.sub.s-m-toe−d.sub.9)/2; wherein d.sub.9=0.67 to 0.73, and $k_{s-m-\mathrm{toe}}=\frac{{\int }_0^{t_{s-\mathrm{toe}}}h\mathrm{dt}}{t_{s-\mathrm{toe}}{h}_{\max -\mathrm{toe}}}.$

9. The method for correcting pulse wave transit time associated with diastolic blood pressure according to claim 1, characterized in that, the six correction variable b.sub.6 is calculated by the following formulas: if k.sub.s-m-toe-ear<1.0, then b.sub.6=0; when k.sub.s-m-toe-ear>1.08, then c.sub.6=1.08, meantime, if t.sub.s>220 and k.sub.sd-m-0>0.88, then b.sub.6=c.sub.6−1.0, if t.sub.s<160 or k.sub.sd-m-0<0.80, then b.sub.6=(c.sub.6−1.0)×0.34, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then b.sub.6=(c.sub.6−1.0)×0.67; when 1.0≤k.sub.s-m-toe-ear≤1.08, then c.sub.6=k.sub.s-m-toe-ear−1.0, meantime, if t.sub.s>220 and k.sub.sd-m-0≥0.88, then b.sub.6=c.sub.6, if t.sub.s≤160 or k.sub.sd-m-0≤0.80, then b.sub.6=c.sub.6×0.34, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then b.sub.6=c.sub.6×0.67; wherein $k_{s-m-\mathrm{toe}-\mathrm{ear}}=\frac{h_{\max }{\int }_0^{t_{s-\mathrm{toe}}}h\mathrm{dt}+\left(t_s+t_{s-\mathrm{toe}}\right)\times 100}{h_{\max -\mathrm{toe}}{\int }_0^{t_s}h\mathrm{dt}+\left(t_s+t_{s-\mathrm{toe}}\right)\times 100},\mathrm{and}$ $k_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}h\mathrm{dt}}.$

10. The method for correcting pulse wave transit time associated with diastolic blood pressure according to claim 1, characterized in that, the seventh correction variable b.sub.7 is calculated by the following formulas: if k.sub.ts-toe-ear<1.0, then b.sub.7=0; when k.sub.ts-toe-ear>1.08, then c.sub.7=1.08, meantime, if t.sub.s>220 and k.sub.sd-m-0>0.88, then b.sub.7=c.sub.7−1.0, if t.sub.s<160 or k.sub.sd-m-0<0.80, then b.sub.7=(c.sub.7−1.0)×0.34, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then b.sub.7=(c.sub.7−1.0)×0.67; when 1.0≤k.sub.ts-toe-ear≤1.08, then c.sub.7=k.sub.ts-toe-ear−1.0, meantime, if t.sub.s>220 and k.sub.sd-m-0>0.88, then b.sub.7=c.sub.7, if t.sub.s≤160 or k.sub.sd-m-0≤0.80, then b.sub.7=c.sub.7×0.34, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then b.sub.7=c.sub.7×0.67; wherein $k_{\mathrm{ts}-\mathrm{toe}-\mathrm{ear}}=\frac{t_{s-\mathrm{toe}}+825}{t_s+825},\mathrm{and}{k}_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}h\mathrm{dt}}.$

11. A method for correcting pulse wave transit time associated with systolic blood pressure, characterized in that, comprising the following steps: S1) detecting a pulse wave at an ear in each cardiac cycle in real time and obtaining following data: the height of an aortic valve closure point on an ear pulse wave denoted as h.sub.sd, the systolic time of the ear pulse wave denoted as t.sub.s, the diastolic time of the ear pulse wave denoted as t.sub.d, and the maximum height of the ear pulse wave denoted as h.sub.max; S2) detecting the pulse wave at a toe in each cardiac cycle in real time and obtaining the following data: the systolic time of a toe pulse wave denoted as t.sub.s-toe, the diastolic time of the toe pulse wave denoted as t.sub.d-toe, the maximum height of the toe pulse wave denoted as h.sub.max-toe, the time interval between starting point to a midpoint of a peak of the toe pulse wave denoted as t.sub.ch-toe, and the time interval between the starting point to the highest point of the peak of the toe pulse wave denoted as t.sub.max-toe, wherein the midpoint of the peak refers to the midpoint of arising edge turning point and a falling edge turning point at the peak; S3) calculating the pulse wave transit time associated with systolic blood pressure denoted as T.sub.s, wherein T.sub.s refers to a time difference between the aortic valve closure point on the ear pulse wave and the aortic valve closure point on the toe pulse wave, and h is the amplitude of the ear pulse wave or the toe pulse wave in a longitudinal direction; S4) by using the data in the same cardiac cycle acquired through the step S1 and the step S2, calculating a plurality of correction variables a.sub.1-a.sub.7 the cardiac cycle; S5) according to the correction variables in the cardiac cycle acquired in the step S4, calculating a total correction value in the cardiac cycle; and S6) continuously acquiring the correction values in a plurality of cardiac cycles, and correcting the T.sub.s acquired in the step S3.

12. The method for correcting pulse wave transit time associated with systolic blood pressure according to claim 11, characterized in that, the total correction value in the step S5 is $A=\underset{i=1}{\overset{7}{.Math.}}{a}_i,$ where A is the sum of the correction variables a.sub.1-a.sub.7,a.sub.i is the i-th correction variable.

13. The method for correcting pulse wave transit time associated with systolic blood pressure according to claim 11, characterized in that, in the step S6, the correction values in 8 cardiac cycles are continuously acquired; the correction method is: T.sub.sma=T.sub.sm(1−Am); wherein $A_m=\frac{1}{8}\underset{i=1}{\overset{8}{.Math.}}{A}_i,T_{\mathrm{sm}}=\frac{1}{8}\underset{i=1}{\overset{8}{.Math.}}{T}_{\mathrm{si}},$ in which T.sub.sma is the T.sub.s after correction, T.sub.sm is the averaged T.sub.s in 8 cardiac cycles, Amis the averaged A in 8 cardiac cycles, A.sub.i is the total correction value in the i-th cardiac cycle, and T.sub.si is T.sub.s in the i-th cardiac cycle.

14. The method for correcting pulse wave transit time associated with systolic blood pressure according to claim 11, characterized in that, the first correction variable a.sub.1 is calculated by the following formulas: if d.sub.1≤k.sub.sd-m-0≤d.sub.1-2, then a.sub.1=(d.sub.1-2−k.sub.sd-m-0)×0.50; if k.sub.sd-m-0<d.sub.1, then a.sub.1=28×0.50; and if k.sub.sd-m-0>d.sub.1-2, then a.sub.1=0; wherein $k_{\mathrm{sd}=m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}h\mathrm{dt}},$ d.sub.1=76 to 84, and d.sub.1-2=104 to 112.

15. The method for correcting pulse wave transit time associated with systolic blood pressure according to claim 11, characterized in that, the second correction variable a.sub.2 is calculated by the following formulas: if k.sub.sd-m>(d.sub.2+(age-14)/15/100), then a.sub.2=k.sub.sd-m−(d.sub.2+(age-14)/15/100); if k.sub.sd-m≤(d.sub.2+(age-14)/15/100), then a.sub.2=0; wherein if |k.sub.sd-m-0−k.sub.sd-m-ts|≥40 and (k.sub.sd-m-0+k.sub.sd-m-ts)/2≥k.sub.sd-m-2, then k.sub.sd-m=2×k.sub.sd-m-2−(k.sub.sd-m-0+k.sub.sd-m-ts)/2, otherwise k.sub.sd-m=k.sub.sd-m-2; $k_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}h\mathrm{dt}},k_{\mathrm{sd}-m-\mathrm{ts}}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{2t_s}h\mathrm{dt}},$ age is age, and d.sub.2=1.17 to 1.27.

16. The method for correcting pulse wave transit time associated with systolic blood pressure according to claim 11, characterized in that, the third correction variable a.sub.3 is calculated by the following formulas: if c.sub.4<k.sub.d-m-a<c.sub.5, then a.sub.3=0; if k.sub.sd-m-0<d.sub.6 or k.sub.sd-m-2>d.sub.7, then a.sub.3=0; if k.sub.sd-m-0≥d.sub.6+0.10 and k.sub.sd-m-2≤d.sub.8 and k.sub.d-m-a≤c.sub.4, then a.sub.3=(c.sub.4−k.sub.d-m-a)×67/100; if $\{\begin{array}{c}{d}_6\le k_{\mathrm{sd}-m-0}<d_6+0.1\\ k_{d-m-a}\le c_4\end{array}\mathrm{or}\{\begin{array}{c}{d}_8<k_{\mathrm{sd}-m-2}<d_7\\ k_{d-m-a}\le c_4\end{array},$ then a.sub.3=(c.sub.4-1k.sub.d-m-a)×50/100; if k.sub.sd-m-0≥d.sub.6+0.10 and k.sub.sd-m-2≤d.sub.8 and k.sub.d-m-a≥c.sub.5, then a.sub.3=(c.sub.5−k.sub.d-m-a)×62/100; if $\{\begin{array}{c}{d}_6\le k_{\mathrm{sd}-m-0}<d_6+0.1\\ k_{d-m-a}\ge c_5\end{array}\mathrm{or}\{\begin{array}{c}{d}_8<k_{\mathrm{sd}-m-2}<d_7\\ k_{d-m-a}\ge c_5\end{array},$ then a.sub.3=(c.sub.5k.sub.d-m-a)×45/100; wherein if |k.sup.sd-m-0−k.sub.sd-m-ts|≥40 and (k.sub.sd-m-0+k.sub.sd-m-ts)/2≥k.sub.sd-m-2 and k.sub.sd-m-ts≥d.sub.3-2, then k.sub.d-m-a=(k.sub.d-m-t.sub.d.sub.-1+k.sub.d-m-t.sub.d-toe+(k.sub.sd-m-0+k.sub.sd-m-ts)/2−k.sub.sd-m-2)/2, otherwise k.sub.d-m-a=(k.sub.d-m-t.sub.d.sub.-1+k.sub.d-m-t.sub.d-toe)/2; if k.sub.sd-m-ts≤d.sub.3-2, then k.sub.d-m-t.sub.d.sub.-1=k.sub.d-m-t.sub.d−(d.sub.3-2−k.sub.sd-m-ts)×75/100; if k.sub.d-m-t.sub.d≤d.sub.3, then k.sub.d-m-t.sub.d.sub.-1=d.sub.3; if k.sub.d-m-t.sub.d-toe≤d.sub.3, then k.sub.d-m-t.sub.d-toe=d.sub.3; $k_{d-m-t_d}=\frac{{\int }_{t_s}^{t_s+t_d}\mathrm{hdt}}{t_d{h}_{\max }},k_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}\mathrm{hdt}},k_{\mathrm{sd}-m-2}=\frac{2t_s{h}_{\mathrm{sd}}}{{\int }_0^{2t_s}\mathrm{hdt}},$ $k_{\mathrm{sd}-m-\mathrm{ts}}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_{t_s}^{2t_s}\mathrm{hdt}},k_{d-m-t_{d-\mathrm{toe}}}=\frac{{\int }_{t_{s-\mathrm{toe}}}^{t_{s-\mathrm{toe}}+t_{d-\mathrm{toe}}}\mathrm{hdt}}{t_{d-\mathrm{toe}}{h}_{\max -\mathrm{toe}}};$ and c.sub.4=(d.sub.4+(age-14)/8)/100, d.sub.4=23 to 35, c.sub.5=(d.sub.5+(age-14)/8)/100, d.sub.5=27 to 39, d.sub.6=0.97 to 1.03, d.sub.7=1.52 to 1.58, d.sub.8=1.42 to 1.48, d.sub.3-2=1.21 to 1.31, d.sub.3=0.02 to 0.14, and age is age.

17. The method for correcting pulse wave transit time associated with systolic blood pressure according to claim 11, characterized in that, the fourth correction variable a4 is calculated by the following formulas: if k.sub.s-t-toe>0.8, then a.sub.4=k.sub.s-t-toe-0.8; if k.sub.s-t-toe≤0.8, then a.sub.4=0; wherein if t.sub.max-toe≥t.sub.ch-toe, then $k_{s-t-\mathrm{toe}}=\frac{t_{\max -\mathrm{toe}}+t_{\mathrm{ch}-\mathrm{toe}}+400}{\left(t_{s-\mathrm{toe}}+200\right)\times 2},$ otherwise $k_{s-t-\mathrm{toe}}=\frac{t_{\max -\mathrm{toe}}+200}{t_{s-\mathrm{toe}}+200}.$

18. The method for correcting pulse wave transit time associated with systolic blood pressure according to claim 11, characterized in that, the fifth correction variable as is calculated by the following formulas: if k.sub.s-m-toe<d.sub.9, then a.sub.5=0; if k.sub.s-m-toe≥d.sub.9 and k.sub.s-t-toe≥0.8, then a.sub.5=k.sub.s-m-toe−d.sub.9; if k.sub.s-m-toe≥d.sub.9 and k.sub.s-t-toe<0.8, then a.sub.5=(k.sub.s-m-toe−d.sub.9)/2; wherein d.sub.9=0.67 to 0.73, $k_{s-m-\mathrm{toe}}=\frac{{\int }_0^{t_{s-\mathrm{toe}}}h\mathrm{dt}}{t_{s-\mathrm{toe}}{h}_{\max -\mathrm{toe}}}.$

19. The method for correcting pulse wave transit time associated with systolic blood pressure according to claim 11, characterized in that, the sixth correction variable a.sub.6 is calculated by the following formulas: if k.sub.s-m-toe-ear<1.0, then a.sub.6=0; when k.sub.s-m-toe-ear>1.08, then c.sub.6=1.08, meantime, if t.sub.s>220 and k.sub.sd-m-0>0.88, then a.sub.6=c.sub.6−1.0, if t.sub.s<160 or k.sub.sd-m-0<0.80, then a.sub.6=(c.sub.6−1.0)×0.34, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then a.sub.6=(c.sub.6−1.0)×0.67; when 1.0≤k.sub.s-m-toe-ear≤1.08, then c.sub.6=k.sub.s-m-toe-ear−1.0, meantime, if t.sub.s>220 and k.sub.sd-m-0>0.88, then a.sub.6=c.sub.6, if t.sub.s≤160 or k.sub.sd-m-0≤0.80, then a.sub.6=c.sub.6×0.34, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then a.sub.6=c.sub.6×0.67; wherein $k_{s-m-\mathrm{toe}-\mathrm{ear}}=\frac{h_{\max }{\int }_0^{t_{s-\mathrm{toe}}}h\mathrm{dt}+\left(t_s+t_{s-\mathrm{toe}}\right)\times 100}{h_{\max -\mathrm{toe}}{\int }_0^{t_s}h\mathrm{dt}+\left(t_s+t_{s-\mathrm{toe}}\right)\times 100},$ $k_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}h\mathrm{dt}}.$

20. The method for correcting pulse wave transit time associated with systolic blood pressure according to claim 11, characterized in that, the seventh correction variable a.sub.7 is calculated by the following formulas: if k.sub.ts-toe-ear<1.0, then a.sub.7=0; when k.sub.ts-toe-ear>1.08, then c.sub.7=1.08, meantime, if t.sub.s>220 and k.sub.sd-m-0>0.88, then a.sub.7=c.sub.7−1.0, if t.sub.s<160 or k.sub.sd-m-0<0.80, then a.sub.7=(c.sub.7−1.0)×0.34, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then a.sub.7=(c.sub.7−1.0)×0.67; when 1.0≤k.sub.ts-toe-ear≤1.08, then c.sub.7=k.sub.ts-toe-ear−1.0, meantime, if t.sub.s>220 and k.sub.sd-m-0>0.88, then a.sub.7=c.sub.7, if t.sub.s≤160 or k.sub.sd-m-0≤0.80, then a.sub.7=c.sub.7×0.34, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then c.sub.7=c.sub.7×0.67; wherein $k_{\mathrm{ts}-\mathrm{toe}-\mathrm{ear}}=\frac{t_{s-\mathrm{toe}}+825}{t_s+825},k_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}h\mathrm{dt}}.$

Description

DESCRIPTION OF THE EMBODIMENTS

[0134] The embodiments of the technical solution of the present invention will be described in detail below. The following embodiments are only used for more clearly illustrating the technical solutions of the present invention, and thus are only examples, and not intended to limit the protection scope of the present invention.

[0135] Pulse wave transit time (PTT) changes in perioperative period can be divided into two categories: type I changes: PTT changes caused by changes in blood pressure; and type II changes: unsynchronized changes in PTT and blood pressure (the direction or amount of changes of the two does not conform to a regular function rule). For example, when the blood volume is mildly insufficient, PTT will increase, but due to the adjustment on peripheral resistance of the body, blood pressure may not change much. The use of a hook in thoracoabdominal surgery may seriously affect PTT, but has less effect on blood pressure. Norepinephrine makes small arteries strongly contract and the blood pressure significantly increase, but the effect on the average PTT of the whole body is small.

[0136] When PTT has type I changes, the relationship between PTT and blood pressure can still be expressed by a certain function, and the change in blood pressure can be estimated by a mathematical model. While when PTT has type II changes, using a mathematical model based on a conventional circulatory system to estimate blood pressure will produce large errors. The errors are principle errors in measurement of blood pressure by using PTT and cannot be solved by initial calibration and periodic calibration of mathematical model parameters. The difference in PTT among different individuals and the irregular change of PTT in the same individual are two different types of problems, which need to be solved by different methods. To this end, the present invention extracts various variables based on the features of the pulse wave to identify and adaptively correct various type II changes of the PTT, and overcome the principle errors; the available mathematical models can be combined to form a continuous and non-invasive measurement method of blood pressure with an adaptive calibration function, without the need to rely on conventional methods such as oscillometry for repeated calibration.

[0137] Positions of the human body for detecting the pulse wave are preferably the ear and the toe. The pulse waves of these two parts contain the physiological and pathological information of the aorta and peripheral arteries, and are representative in propagation paths. A sensor for detecting the pulse signal is preferably an infrared photo plethysmograph (PPG).

[0138] The feature changes of ear and toe pulse waves, and the relative changes in features between the two pulse waves provide rich information for identifying the type II changes in PTT and the changes in blood pressure difference between different sites of the body. The present invention collects the invasive arterial blood pressure, pulse waves of the ears and toes, and PTT of a large number of surgical cases for several years for analysing, extracts various variables according to the feature changes and relative feature changes of the two pulse waves, studies the relationship between different variables and different type II changes of PTT, and defines the application scopes of these variables.

[0139] In clinical application, during continuous measurement of blood pressure using PPT, the pulse waveform is analysed in real time and variables are extracted. Whether the PTT has the type II changes is determined according to whether the variables fall within the application scope, and the nature and extent of the type II changes of the PTT are determined according to the nature of the applicable variables. If a variable is outside the application scope, the corresponding type II changes do not occur in the PTT, then the variable is not applicable. Several applicable variables are fused to calculate the correction amount to correct the PTT. The corrected PTT/PWV is applicable to the available mathematical models to accurately calculate the blood pressure.

[0140] The present invention uses limited variables to express the most important changes of pulse wave form, and studies the relationship between these changes and PTT. As for the pulse wave in plane coordinates, the ordinate is amplitude h, the abscissa is time t, and the pulse wave starting point is the coordinate origin.

Embodiment 1

[0141] A method for correcting PTT associated with diastolic blood pressure, includes the following steps:

[0142] S1) detecting a pulse wave at an ear in each cardiac cycle in real time and obtaining the following data: the height of an aortic valve closure point on an ear pulse wave denoted as h.sub.sd, that is, the height at a junction between the systolic and diastolic phases on the ear pulse wave, the systolic time of the ear pulse wave denoted as t.sub.s, the diastolic time of the ear pulse wave denoted as t.sub.d, and the maximum height of the ear pulse wave denoted as h.sub.max;

[0143] S2) detecting the pulse wave at a toe in each cardiac cycle in real time and obtaining the following data: the systolic time of the toe pulse wave denoted as t.sub.s-toe, the diastolic time of the toe pulse wave denoted as t.sub.d-toe, the maximum height of the toe pulse wave denoted as h.sub.max-toe, the time interval between the starting point to the midpoint of the peak of the toe pulse wave denoted as t.sub.d-toe, and the time interval between the starting point to the peak of the toe pulse wave denoted as t.sub.max-toe, where the midpoint of the peak refers to the midpoint of arising edge turning point and a falling edge turning point at the peak; the definition of the midpoint of the peak can be understood by referring to the literature YAN CHEN, CHANGYUN WEN, GUOCAI TAO, and MIN BI Continuous and Non-invasive Measurement of Systolic and Diastolic Blood Pressure by One Mathematical Model with the Same Model Parameters and Two Separate Pulse Wave Velocities.

[0144] S3) calculating the PTT associated with diastolic blood pressure denoted as T.sub.d, and the definition can be understood by referring to the literature YAN CHEN, CHANGYUN WEN, GUOCAI TAO, and MIN BI Continuous and Non-invasive Measurement of Systolic and Diastolic Blood Pressure by One Mathematical Model with the Same Model Parameters and Two Separate Pulse Wave Velocities; h is the amplitude of the ear pulse wave or the toe pulse wave in a longitudinal direction;

[0145] S4) by using the data in the same cardiac cycle acquired through step S1 and step S2, calculating a few correction variables in the cardiac cycle;

[0146] S5) according to the correction variables in the cardiac cycle acquired in step S4, calculating a total correction value in the cardiac cycle; and

[0147] S6) continuously acquiring the correction values in a plurality of cardiac cycles, and correcting the T.sub.d acquired in the step S3.

[0148] By the method, the PTT associated with diastolic blood pressure is determined by a time difference of an ear pulse wave and a toe pulse wave in the same cardiac cycle, and a few correction variables are extracted based on the pulse wave features, then a total correction value is acquired to perform adaptive correction on the irregular change of pulse wave transit time. The corrected transit time can be used with available mathematical models for continuously and accurately measuring diastolic blood pressure in each cardiac cycle in a clinical setting.

[0149] First correction variable b.sub.1:

[0150] The correction variables obtained in the step S4 include a first correction variable b.sub.1. b.sub.1 is used for correcting the type II changes in T.sub.d in a hypotensive state, the applicable range of b.sub.1 is b.sub.1>0, and if b.sub.1 is larger, the blood pressure is lower.

[00033]$k_{sd-m-0}=\frac{t_s{h}_{sd}}{{\int }_0^{t_s}hdt},$

k.sub.sd-m-0 represents the ratio of h.sub.sd to the average height of the ear pulse wave systole. In some cases, under a hypotensive state, the pulse wave peak appears as a forward-inclined triangle; When h.sub.sd decreases a lot, k.sub.sd-m-0 becomes smaller, indicating that the waveform at the end of the aortic systole is much lower, the continuous power for pushing pulse wave transit is insufficient, and the transit time is prolonged. In this state, the diastolic information is unstable and should not be used.

[0151] d.sub.1-b=74 to 82, preferably is 78. d.sub.1-2-b=98 to 106, preferably is 102.

[0152] When the continuous power for pushing pulse wave transit is insufficient, the transit time T.sub.d is prolonged and needed be corrected by b.sub.1. That is, if d.sub.1-b≤k.sub.sd-m-0≤d.sub.1-2-b, then b.sub.1=(d.sub.1-2-b−k.sub.sd-m-0)×0.4.

[0153] When the continuous power for pushing pulse wave transit is seriously insufficient, the transit time T.sub.d is prolonged a lot, and b.sub.1 takes the upper limit value for correction. That is, if k.sub.sd-m-0<d.sub.1-b, then b.sub.1=24×0.4.

[0154] When the continuous power for pushing pulse wave transit is sufficient, T.sub.d does not need to be corrected, and b.sub.1 is not applicable. That is, if k.sub.sd-m-0>d.sub.1-2-b, then set b.sub.1=0.

[0155] Second correction variable b.sub.2:

[0156] The correction variables obtained in the step S4 also include a second correction variable b.sub.2, b.sub.2 is used for correcting the type II changes in T.sub.d in a hypertensive state, the applicable range of b.sub.2 is b.sub.2>0, and if b.sub.2 is larger, the diastolic blood pressure is higher.

[00034]$k_{\mathrm{sd}-m-\mathrm{ts}}=\frac{t_s{h}_{sd}}{{\int }_{t_s}^{2t_s}hdt},$

k.sub.sd-m-ts represents the ratio of h.sub.sd to the average height of the t.sub.s to 2t.sub.s segments of the ear pulse wave diastole, and is used for determining the irregular change of the pulse wave diastole. For example, in a thoracoabdominal surgery, an upward pulling hook causes the aortic stress to change, so that the amplitude of the ear pulse wave diastole is reduced, and the k.sub.sd-m-ts becomes larger.

[00035]$k_{sd-m-2}=\frac{2t_s{h}_{sd}}{{\int }_0^{2t_s}\mathrm{hdt}},$

k.sub.sd-m-2 represents the ratio of h.sub.sd to the average height of the ear pulse wave 0 to 2t.sub.s segments, includes the information of systolic and partial diastolic waveform, and is mainly used for a hypertensive state, such as increase of heart rate and blood pressure caused by tracheal intubation. In the state of hypertension, the ear pulse wave appears an equilateral triangle or a backward-inclined triangle, h.sub.sd rises a lot, and k.sub.sd-m-2 becomes larger. Compared with the waveform in a normal blood pressure state, the slope of the rising edge of the waveform in the hypertensive state becomes smaller, the power for pushing pulse wave transit is insufficient, and the transit time T.sub.d is prolonged.

[0157] If |k.sub.sd-m-0−k.sub.sd-m-ts|≥40 and (k.sub.sd-m-0+k.sub.sd-m-ts)/2≥k.sub.sd-m-2,

[0158] then k.sub.sd-m=2×k.sub.sd-m-2−(k.sub.sd-m-0+k.sub.sd-m-ts)/2,

[0159] otherwise k.sub.sd-m=k.sub.sd-m-2;

[0160] If the waveform of the ear pulse wave diastole has an irregular change, for example, if the upward pulling hook of the thoracoabdominal surgery causes the aortic stress to change, and the form of the pulse wave diastole changes significantly, k.sub.sd-m is corrected, otherwise k.sub.sd-m=k.sub.sd-m-2.

[0161] d.sub.2-b=1.33 to 1.43, preferably is 1.38.

[0162] If k.sub.sd-m>(d.sub.2-b+(age-14)/15/100), where age is age, the continuous power corresponding to the diastolic pressure is insufficient, the transit time T.sub.d is relatively prolonged, and needed be corrected by b.sub.2, then b.sub.2=(k.sub.sd-m−(d.sub.2-b+(age-14)/15/100))×0.5, the change of b.sub.2 is inversely proportional to the change of the slope of the pulse wave rising edge, where 0.5 is the proportional coefficient.

[0163] If k.sub.sd-m≤(d.sub.2-b+(age-14)/15/100), the continuous power corresponding to the diastolic pressure is sufficient, b.sub.2 is not applicable, then set b.sub.2=0.

[0164] Third correction variable b.sub.3:

[0165] The correction variables obtained in the step S4 further include a third correction variable b.sub.3, which is used for correcting the T.sub.d in a state that the blood volume changes or the body temperature of a sensor placement site changes.

[00036]$k_{d-m-t_d}=\frac{{\int }_{t_s}^{t_s+t_d}hdt}{t_d{h}_{\max }},$

k.sub.d-m-t.sub.d is the ratio of the average height of the ear pulse wave diastole to the maximum height h.sub.max. The blood volume is reduced when a patient fasts and drinks less water before surgery, k.sub.d-m-t.sub.d decreases, and the transit time is prolonged; when the blood volume increases due to blood transfusion and IV transfusion in the operation, k.sub.d-m-t.sub.d increases, and the transit time is shortened.

[0166] If k.sub.sd-m-ts≤d.sub.3-2, indicating that the early diastole of ear pulse wave rises and exceeds a normal range, then k.sub.d-m-t.sub.d needs to be corrected, and the correction result is noted as k.sub.d-m-t.sub.d.sub.-1.

[0167] k.sub.d-m-t.sub.t.sub.-1=k.sub.d-m-t.sub.d−(d.sub.3-2−k.sub.sd-m-ts)×75/100; if k.sub.d-m-t.sub.d≤d.sub.3, indicated that the ear pulse wave is disturbed, then k.sub.d-m-t.sub.d.sub.-1=d.sub.3. d.sub.3=0.02 to 0.14, preferably is 0.08; d.sub.3-2=1.21 to 1.31, preferably is 1.26.

[00037]$k_{d-m-t_{d-\mathrm{toe}}}=\frac{{\int }_{t_{s-\mathrm{toe}}}^{t_{s-\mathrm{toe}}+t_{d-\mathrm{toe}}}\mathrm{hdt}}{t_{d-toe}{h}_{\max -\mathrm{toe}}},$

k.sub.d-m-t.sub.d-toe is the ratio of the average height of the toe pulse wave diastole to the maximum height h.sub.max-toe, t.sub.s-toe represents the systolic time of the toe pulse wave, and t.sub.d-toe represents the diastolic time of the toe pulse wave. If k.sub.d-m-t.sub.d-toe≤d.sub.3, then k.sub.d-m-t.sub.d-toe=d.sub.3. The properties of k.sub.d-m-t.sub.d-toe and k.sub.d-m-t.sub.d are same.

[0168] k.sub.d-m-a=(k.sub.d-m-t.sub.d.sub.-1+k.sub.d-m-t.sub.d-toe)=/2 two variables from the ear and toe pulse waves with the same property are combined, and the average value is taken as a correction variable; if the pulse wave diastole has an irregular change, the k.sub.d-m-a is corrected.

[0169] If |k.sub.sd-m-0−k.sub.sd-m-ts|≥40 and (k.sub.sd-m-0+k.sub.sd-m-ts)/2≥k.sub.sd-m-2 and k.sub.sd-m-ts≥d.sub.3-2,

[0170] then k.sub.d-m-a=(k.sub.d-m-t.sub.d.sub.-1+k.sub.d-m-t.sub.d-toe+(k.sub.sd-m-0++k.sub.sd-m-ts)/2−k.sub.sd-m-2)/2.

[0171] In the state that the blood volume is normal and the body temperature of the sensor placement site is also normal, b.sub.3 is not applicable. That is, if c.sub.4<k.sub.d-m-a<c.sub.5, then set b.sub.3=0. c.sub.4=(d.sub.4+(age-14)/8)/100, d.sub.4=23 to 35, preferably is 29; c.sub.5=(d.sub.5+(age-14)/8)/100, d.sub.5=27 to 39, preferably is 33.

[0172] In an extremely low or high blood pressure state, the information of diastolic period is unstable, and b.sub.3 is not applicable. That is, if k.sub.sd-m-0<d.sub.6 or k.sub.sd-m-2>d.sub.7, then set b.sub.3=0. d.sub.6=0.97 to 1.03, preferably is 1.00; d.sub.7=1.52 to 1.58, preferably is 1.55.

[0173] In a normal blood pressure state, when the blood volume decreases or the body temperature of the sensor placement site decreases, b.sub.3 takes 67% of a positive value. That is, if k.sub.sd-m-0≥d.sub.6+0.10 and k.sub.sd-m-2≤d.sub.8 and k.sub.d-m-a≤c.sub.4, then b.sub.3=(c.sub.4−k.sub.(d-m-a)×67/100. d.sub.8=1.42 to 1.48, preferably is 1.45.

[0174] In relatively low or high blood pressure states, when the blood volume decreases or the body temperature of the sensor placement site decreases, b.sub.3 takes 50% of a positive value. That is, if

[00038]$\{\begin{array}{c}{d}_6\le k_{\mathrm{sd}-m-0}<d_6+0.1\\ k_{d-m-a}\le c_4\end{array}\mathrm{or}\{\begin{array}{c}{d}_8<k_{\mathrm{sd}-m-2}<d_7\\ k_{d-m-a}\le c_4\end{array},$

then b.sub.3=(c.sub.4k.sub.d-m-a)×50/100;

[0175] In a normal blood pressure state, when the blood volume increases or the body temperature of the sensor placement site rises, b.sub.3 takes 62% of a negative value. That is, if k.sub.sd-m-0≥d.sub.6+0.10 and k.sub.sd-m-2≤d.sub.8 and k.sub.d-m-a≥c.sub.5, then b.sub.3=(c.sub.5k.sub.d-m-a)×62/100;

[0176] In a state of relatively low or high blood pressure, when the blood volume increases or the body temperature of the sensor placement site increases, b.sub.3 takes 45% of the negative value. That is, if

[00039]$\{\begin{array}{c}{d}_6\le k_{\mathrm{sd}-m-0}<d_6+0.1\\ k_{d-m-a}\ge c_5\end{array}\mathrm{or}\{\begin{array}{c}{d}_8<k_{\mathrm{sd}-m-2}<d_7\\ k_{d-m-a}\ge c_5\end{array},$

then b.sub.3=(c.sub.5k.sub.d-m-a)×45/100.

[0177] Fourth correction variable b.sub.4:

[0178] The correction variables obtained in the step S4 further include a fourth correction variable b.sub.4, which is used for correcting T.sub.d in the case that the peripheral blood vessel dilation causes the lower limb blood pressure (relative to the radial artery blood pressure) to decrease. The applicable range of b.sub.4 is b.sub.4>0, and if b.sub.4 is larger, the lower limb blood pressure is much lowered relative to the radial artery blood pressure.

[0179] Contraction and expansion of peripheral blood vessels may cause the peak of the toe pulse wave to move back and forth on a time axis. If t.sub.max-toe≥t.sub.ch-toe, then

[00040]$k_{s-t-toe}=\frac{t_{\max -\mathrm{toe}}+t_{ch-toe}+400}{\left(t_{s-toe}+200\right)⨯2},$

otherwise

[00041]$k_{s-t-\mathrm{toe}}=\frac{t_{\max -\mathrm{toe}}+200}{t_{s-\mathrm{toe}}+200}.$

[0180] k.sub.s-t-toe is the ratio of the time from a start point to a peak of the toe pulse wave to the time of the systole, and 200 is an adjustment coefficient. When the highest point of the peak moves back beyond the midpoint, that is, when t.sub.max-toe≥t.sub.ch-toe, k.sub.s-t-toe is corrected; when the value of k.sub.s-t-toe is large, indicating that the toe blood vessels dilate and the lower limb blood pressure decreases. That is, if k.sub.s-t-toe>0.8, then b.sub.4=k.sub.s-t-toe−0.8. If k.sub.s-t-toe≤0.8, b.sub.4 is not applicable, then set b.sub.4=0.

[0181] Fifth correction variable b.sub.5;

[0182] The correction variables obtained in the step S4 further include a fifth correction variable b.sub.5, the role and property of b.sub.5 are the same as those of the b.sub.4, and b.sub.5 is used for correcting T.sub.d in the case that the lower limb blood pressure decreases relative to the radial artery blood pressure.

[00042]$k_{s-t-\mathrm{toe}}=\frac{{\int }_0^{t_{s-\mathrm{toe}}}\mathrm{hdt}}{t_{s-\mathrm{toe}}{h}_{\max -\mathrm{toe}}},$

[0183] k.sub.s-m-toe is the ratio of the average height of the toe pulse wave systole to the maximum height h.sub.max-toe; if k.sub.s-m-toe is large, indicating that the toe pulse wave peak is broad and flat, suggesting that the toe blood vessels dilate, and the lower limb blood pressure decreases relative to the radial artery.

[0184] When the toe blood vessels do not dilate, b.sub.5 is not applicable. That is, if k.sub.s-m-toe<d.sub.9, then set b.sub.5=0. d.sub.9=0.67 to 0.73, preferably is 0.7.

[0185] When the toe blood vessels dilate and the highest point of the pulse wave peak shifts backwards beyond the midpoint, b.sub.5 takes a positive value. That is, if k.sub.s-m-toe≥d.sub.9 and k.sub.s-t-toe≥0.8, then b.sub.5=k.sub.s-m-toe−d.sub.9.

[0186] When the toe blood vessels dilate and the highest point of the pulse wave peak does not exceed the midpoint, b.sub.5 takes half of the positive value. That is, if k.sub.s-m-toe≥d.sub.9 and k.sub.s-t-toe<0.8, then b.sub.5=(k.sub.s-m-toe−d.sub.9)/2.

[0187] Sixth correction variable b.sub.6;

[0188] The correction variables obtained in the step S4 further include a sixth correction variable b.sub.6, which represents a relative change in the area of two pulse waves, and is used for correcting T.sub.d when the toe blood vessels dilate and the lower limb blood pressure decreases relative to the radial artery blood pressure. The applicable range of b.sub.6 is b.sub.6>0;

[00043]$k_{s-m-\mathrm{toe}-\mathrm{ear}}=\frac{h_{\max }{\int }_0^{t_{s-\mathrm{toe}}}\mathrm{hdt}+\left(t_s+t_{s-\mathrm{toe}}\right)\times 100}{h_{\max -\mathrm{toe}}{\int }_0^{t_s}\mathrm{hdt}+\left(t_s+t_{s-\mathrm{toe}}\right)\times 100},$

k.sub.s-m-toe-ear is the ratio of the area of the toe pulse wave systole to the area of the ear pulse wave systole, and 100 is the adjustment coefficient; k.sub.s-m-toe-ear has the same role and property as those of k.sub.ts-toe-ear.

[0189] When the toe wave area is smaller than the ear wave area, the toe blood vessels have no relative dilation, and b.sub.6 is not applicable. That is, if k.sub.s-m-toe-ear<1.0, then set b.sub.6=0.

[0190] Under the first precondition that the toe area is greatly larger than the ear area, toe blood vessels dilate more, and C.sub.6 takes a constant of 1.08 as the maximum value for use. That is, if k.sub.s-m-toe-ear>1.08, then set c.sub.6=1.08.

[0191] If the shape of the ear pulse wave is normal, b.sub.6 takes the maximum correction value. That is, if t.sub.s>220 and k.sub.sd-m-0>0.88, then b.sub.6=c.sub.6−1.0.

[0192] If the ear pulse wave appears as a very sharp forward-inclined triangle or the waveform is very narrow, representing that the shape of the ear pulse wave is severely irregular. At this time, the relative change between two pulse waves is amplified, the correction value needs to be reduced for use, and b.sub.6 takes ⅓ of the maximum correction value. That is, if t.sub.s<160 or k.sub.sd-m-0<0.80, then b.sub.6=(c.sub.6−1.0)×0.34.

[0193] When the irregularity of the shape of the ear pulse wave is not too severe, b.sub.6 takes ⅔ of the maximum correction value. That is, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then b.sub.6=(c.sub.6−1.0)×0.67.

[0194] Under the second precondition that the toe area is larger than the ear area, relative dilatation of the toe blood vessels is not too severe, and c.sub.6 takes a positive variable for use. That is, if 1.0≤k.sub.s-m-toe-ear≤1.08, then c.sub.6=k.sub.s-m-toe-ear−1.0.

[0195] If the shape of the ear pulse wave is normal, b.sub.6 takes a positive variable as the correction value. That is, if t.sub.s>220 and k.sub.sd-m-0>0.88, then b.sub.6=c.sub.6.

[0196] If the shape of the ear pulse wave is severely irregular, the relative change between the two pulse waves is amplified, the correction value needs to be reduced for use, and b.sub.6 takes ⅓ of a positive variable. That is, if t.sub.s≤160 or k.sub.sd-m-0≤0.80, then b.sub.6=c.sub.6×0.34.

[0197] When the irregularity of the ear pulse wave is not too severe, b.sub.6 takes ⅔ of a positive variable. That is, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then b.sub.6=c.sub.6×0.67.

[0198] Seventh correction variable b.sub.7;

[0199] The correction variables obtained in the step S4 further include a seventh correction variable b.sub.7, the role and property of b.sub.7 are the same as those of b.sub.6, and b.sub.7 represents the relative change of the systolic time of two pulse waves.

[00044]$k_{\mathrm{ts}-\mathrm{toe}-\mathrm{ear}}=\frac{t_{s-\mathrm{toe}}+825}{t_s+825},$

[0200] k.sub.ts-toe-ear is the ratio of the time of systole on the toe pulse wave to the time of systole on the ear pulse wave, and 825 is the adjustment coefficient; increase in k.sub.ts-toe-ear suggests that the toe blood vessels dilate, and the lower limb blood pressure decreases relative to the radial artery blood pressure.

[0201] When the toe blood vessels have no relative dilation, b.sub.7 is not applicable. That is, if k.sub.ts-toe-ear<1.0, then set b.sub.7=0.

[0202] Under the first precondition that toe blood vessels have severely relative dilation comparing to radial blood vessels, c.sub.7 takes a constant of 1.08 as the maximum value for use. That is, if k.sub.ts-toe-ear>1.08, then set c.sub.7=1.08.

[0203] If the shape of the ear pulse wave is normal, b.sub.7 takes the maximum correction value. That is, if t.sub.s>220 and k.sub.sd-m-0>0.88, then b.sub.7=c.sub.7−1.0.

[0204] If the shape of the ear pulse wave is severely irregular, the relative change between the two pulse waves is amplified, the correction value needs to be reduced for use, and b.sub.7 takes ⅓ of the maximum correction value. That is, if t.sub.s<160 or k.sub.sd-m-0<0.80, then b.sub.7=(c.sub.7−1.0)×0.34.

[0205] If the irregularity of the shape of the ear pulse wave is not too severe, b.sub.7 takes ⅔ of the maximum correction value. That is, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then b.sub.7=(c.sub.7−1.0)×0.67.

[0206] Under the second precondition that the toe systolic time is greater than the ear systolic time, the relative dilatation of the toe blood vessels is not too severe comparing to that of radial blood vessels, and c.sub.7 takes a positive variable for use. That is, if 1.0≤k.sub.ts-toe-ear≤1.08, then c.sub.7=k.sub.ts-toe-ear−1.0

[0207] If the shape of the ear pulse wave is normal, b.sub.7 takes a positive variable as the correction value. That is, if t.sub.s>220 and k.sub.sd-m-0>0.88, then b.sub.7=c.sub.7.

[0208] If the irregularity of the shape of the ear pulse wave is too severe, b.sub.7 takes ⅓ of a positive variable. That is, if t.sub.s≤160 or k.sub.sd-m-0≤0.80, then b.sub.7=c.sub.7×0.34.

[0209] If the irregularity of the shape of the ear pulse wave is not too severe, b.sub.7 takes ⅔ of the positive variable. That is, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then b.sub.7=c.sub.7×0.67.

[0210] The total correction value in the step S5 is

[00045]$B=\underset{i=1}{\overset{7}{.Math.}}{b}_i.$

Where if b.sub.i=0, indicating that b.sub.i is not applicable. The step S6 is specifically: continuously acquiring the correction values in 8 cardiac cycles, and using the average value of the 8 values to overcome the disturbance of respiratory fluctuation, where the 8 values are selected by recursion, and the oldest matrix is eliminated each time when a new matrix is calculated. A correction method is: T.sub.dmb=T.sub.dm(1−B.sub.m); where

[00046]$B=\frac{1}{8}\underset{i=1}{\overset{8}{.Math.}}{B}_i,T_{dm}=\frac{1}{8}\underset{i=1}{\overset{8}{.Math.}}{T}_{\mathrm{di}},$

B.sub.i is the total correction value in the i-th cardiac cycle, and T.sub.di is T.sub.d in the i-th cardiac cycle.

Embodiment 2

[0211] A method for correcting PTT associated with systolic blood pressure, includes the following steps:

[0212] S1) detecting a pulse wave at an ear in each cardiac cycle in real time and obtaining the following data: the height of an aortic valve closure point on the ear pulse wave denoted as h.sub.sd, that is, the height at a junction between the systolic and diastolic phases on the ear pulse wave, the systolic time of the ear pulse wave denoted as t.sub.s, the diastolic time of the ear pulse wave denoted as t.sub.d, and the maximum height of the ear pulse wave denoted as h.sub.max;

[0213] S2) detecting the pulse wave at a toe in each cardiac cycle in real time and obtaining the following data: the systolic time of the toe pulse wave denoted as t.sub.s-toe, the diastolic time of the toe pulse wave denoted as t.sub.d-toe, the maximum height of the toe pulse wave denoted as h.sub.max-toe, the time interval between the starting point to the midpoint of the peak of the toe pulse wave denoted as t.sub.ch-toe, and the time interval between the starting point to the highest point of the peak of the toe pulse wave denoted as t.sub.max-toe, where the midpoint of the peak refers to the midpoint of arising edge turning point and a falling edge turning point at the peak; the definition of the midpoint of the peak can be understood by referring to the literature YAN CHEN, CHANGYUN WEN, GUOCAI TAO, and MIN BI Continuous and Non-invasive Measurement of Systolic and Diastolic Blood Pressure by One Mathematical Model with the Same Model Parameters and Two Separate Pulse Wave Velocities.

[0214] S3) calculating the PTT associated with systolic blood pressure denoted as T.sub.s, and the definition can be understood by referring to the literature YAN CHEN, CHANGYUN WEN, GUOCAI TAO, and MIN BI Continuous and Non-invasive Measurement of Systolic and Diastolic Blood Pressure by One Mathematical Model with the Same Model Parameters and Two Separate Pulse Wave Velocities; h is the amplitude of the ear pulse wave or the toe pulse wave in a longitudinal direction;

[0215] S4) by using the data in the same cardiac cycle acquired through step S1 and step S2, calculating a few correction variables a.sub.1-win the cardiac cycle;

[0216] S5) according to the correction variables in the cardiac cycle acquired in step S4, calculating a total correction value in the cardiac cycle; and

[0217] S6) continuously acquiring the correction values in a plurality of cardiac cycles, and correcting the T.sub.s acquired in the step S3.

[0218] By the method, the PTT associated with systolic blood pressure is determined by a time difference of an ear pulse wave and a toe pulse wave in the same cardiac cycle, and a few correction variables are extracted based on the pulse wave features, then a total correction value is acquired to perform adaptive correction on the irregular change of pulse wave transit time. The corrected transit time can be used with available mathematical models for continuously and accurately measuring systolic blood pressure in each cardiac cycle in a clinical setting.

[0219] First correction variable a.sub.1:

[0220] The correction variables obtained in the step S4 include a first correction variable a.sub.1, a.sub.1 is used for correcting the type II changes in T.sub.s in a hypotensive state, the applicable range of a.sub.1 is a.sub.1>0, and if a.sub.1 is larger, the blood pressure is lower.

[00047]$k_{\mathrm{sd}-m-0}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_0^{t_s}\mathrm{hdt}},$

[0221] k.sub.sd-m-0 represents the ratio of h.sub.sd to the average height of the ear pulse wave. In some cases, under a hypotensive state, the pulse wave peak appears as a forward-inclined triangle. When h.sub.sd decreases a lot, k.sub.sd-m-0 becomes smaller, indicating that the waveform at the end of the aortic systole is much lower, the continuous power for pushing wave transit is insufficient, and the transit time is prolonged. In this state, the diastolic information is unstable and should not be used. d.sub.1=76 to 84, preferably is 80; d.sub.1-2=104 to 112, preferably is 108.

[0222] When the continuous power for pushing pulse wave transit is insufficient, the transit time T.sub.s is prolonged and needed be corrected by a.sub.1. That is, if d.sub.1≤k.sub.sd-m-0≤d.sub.1-2, then a.sub.1=(d.sub.1-2−k.sub.sd-m-0)×0.50;

[0223] When the continuous power for pushing pulse wave transit is seriously insufficient, the transit time T.sub.s is prolonged a lot, and a.sub.1 takes the upper limit value for correction. That is, if k.sub.sd-m-0<d.sub.1, then a.sub.1=28×0.50;

[0224] When the continuous power for pushing pulse wave transit is sufficient, T.sub.s does not need to be corrected, and a.sub.1 is not applicable. That is, if k.sub.sd-m-0>d.sub.1-2, then a.sub.1=0.

[0225] Second correction variable a.sub.2:

[0226] The correction variables obtained in the step S4 also include a second correction variable a.sub.2, a.sub.2 is used for correcting the type II changes in T.sub.s in a hypertensive state and in a change process from a normotensive state to the hypertensive state, the applicable range of a.sub.2 is a.sub.2>0, and if a.sub.2 is larger, the systolic blood pressure is higher.

[00048]$k_{\mathrm{sd}-m-\mathrm{ts}}=\frac{t_s{h}_{\mathrm{sd}}}{{\int }_{t_s}^{2t_s}\mathrm{hdt}},$

[0227] k.sub.sd-m-ts represents the ratio of h.sub.sd to the average height of the t.sub.s to 2t.sub.s segments of the ear pulse wave diastole, and is used for determining the irregular change of the pulse wave diastole. For example, in the thoracoabdominal surgery, the upward pulling hook causes the aortic stress to change, so that the amplitude of the ear pulse wave diastole is reduced, and the k.sub.sd-m-ts becomes larger.

[00049]$k_{\mathrm{sd}-m-2}=\frac{2t_s{h}_{\mathrm{sd}}}{{\int }_{t_s}^{2t_s}\mathrm{hdt}},$

[0228] k.sub.sd-m-2 represents the ratio of h.sub.sd to the average height of the ear pulse wave 0 to 2t.sub.s segments, includes the information of systolic and partial diastolic waveform, and is mainly used for a hypertensive state and a change process from a normotensive state to the hypertensive state, such as increase of heart rate and blood pressure caused by tracheal intubation. In the process of change from the normotensive state to the hypertensive state, the peak of the ear pulse wave gradually appears as an equilateral triangle or a backward-inclined triangle, h.sub.sd gradually increases, and k.sub.sd-m-2 gradually becomes larger; in the hypertensive state, the entire ear pulse wave appears as an equilateral triangle or a backward-inclined triangle, h.sub.sd rises a lot, and k.sub.sd-m-2 becomes very large; the peaks (i.e., the maximal blood pressure) of the triangles of the above two waveforms is very short in duration, the continuous power corresponding to the maximal blood pressure is insufficient, and the transit time T.sub.s is relatively prolonged.

[0229] If |k.sub.sd-m-0−k.sub.sd-m-ts|≥40 and (k.sub.sd-m-0+k.sub.sd-m-ts)/2≥k.sub.sd-m-2,

[0230] then k.sub.sd-m=2×k.sub.sd-m-2−(k.sub.sd-m-0+k.sub.sd-m-ts)/2,

[0231] otherwise k.sub.sd-m=k.sub.sd-m-2;

[0232] If the waveform of the ear pulse wave diastole has an irregular change, for example, if the upward pulling hook of the thoracoabdominal surgery causes the aortic stress to change, and the form of the pulse wave diastole changes significantly, the k.sub.sd-m is corrected, otherwise k.sub.sd-m=k.sub.sd-m-2. d.sub.2=1.17 to 1.27, preferably is1.22.

[0233] If k.sub.sd-m>(d.sub.2+(age-14)/15/100), where age is age, age≥14 years old, indicating that the entire ear pulse wave or the peak thereof becomes an equilateral triangle or a backward-inclined triangle, the continuous power corresponding to the maximal blood pressure is insufficient, the transit time T.sub.s is relatively prolonged, and a.sub.2 is needed for correction, then a.sub.2=k.sub.sd-m−(d.sub.2+(age-14)/15/100).

[0234] If k.sub.sd-m≥(d.sub.2+(age-14)/15/100), the peak of the pulse wave is flat, the continuous power corresponding to the maximal blood pressure is sufficient, and a.sub.2 is not needed for correction, then set a.sub.2=0.

[0235] Third correction variable a.sub.3:

[0236] The correction variables obtained in the step S4 further include a third correction variable a.sub.3, which is used for correcting T.sub.s in a state that the blood volume changes or the body temperature of a sensor placement site changes.

[00050]$k_{d-m-t_d}=\frac{{\int }_{t_s}^{t_s+t_d}\mathrm{hdt}}{t_d{h}_{\max }},$

[0237] k.sub.d-m-t.sub.d is the ratio of the average height of the ear pulse wave diastole to the maximum height h.sub.max. The blood volume decreases when a patient fasts and drinks less water before surgery, k.sub.d-m-t.sub.d decreases, the transit time is prolonged, when the blood volume increases due to blood transfusion and IV transfusion in the operation, k.sub.d-m-t.sub.d increases, and the transit time is shortened.

[0238] If k.sub.sd-m-ts≤d.sub.3-2, indicating that the early diastole of the ear pulse wave rises and exceeds a normal range, k.sub.d-m-t.sub.d needs to be corrected, and the correction result is noted as k.sub.d-m-t.sub.d.sub.-1.

[0239] k.sub.d-m-t.sub.d.sub.-1=k.sub.d-m-t.sub.d−(d.sub.3-2−k.sub.sd-m-ts)×75/100; if k.sub.d-m-t.sub.d≤d.sub.3, indicated that the ear pulse wave is disturbed, then k.sub.d-m-t.sub.d=d.sub.3. d.sub.3=0.02 to 0.14, preferably is 0.08; d.sub.3-2=1.21 to 1.31, preferably is 1.26.

[00051]$k_{d-m-t_{d-\mathrm{toe}}}=\frac{{\int }_{t_{s-\mathrm{toe}}}^{t_{s-\mathrm{toe}}+t_{d-\mathrm{toe}}}\mathrm{hdt}}{t_{d-\mathrm{toe}}{h}_{\max -\mathrm{toe}}},$

[0240] k.sub.d-m-t.sub.d-toe is the ratio of the average height of the toe pulse wave diastole to the maximum height h.sub.max-toe, t.sub.s-toe represents the systolic time of the toe pulse wave, and t.sub.d-toe represents the diastolic time of the toe pulse wave. If k.sub.d-m-t.sub.d-toe≤d.sub.3, then k.sub.d-m-t.sub.d-toe=d.sub.3. k.sub.d-m-t.sub.d-toe and k.sub.d-m-t.sub.d have the same role and property.

[0241] k.sub.d-m-a=(k.sub.d-m-t.sub.d.sub.-1+k.sub.d-m-t.sub.d-toe)/2 two variables from the ear and toe pulse waves with the same property are combined, and the average value is taken as the variable for correcting T.sub.s. If the pulse wave diastole has an irregular change, k.sub.d-m-a is corrected.

[0242] If |k.sub.sd-m-0−k.sub.sd-m-ts|≥40 and (k.sub.sd-m-0+k.sub.sd-m-ts)/2≥k.sub.sd-m-2 and k.sub.sd-m-ts≥d.sub.3-2,

[0243] then k.sub.d-m-a=(k.sub.d-m-t.sub.d.sub.-1+k.sub.d-m-t.sub.d-toe+(k.sub.sd-m-0+k.sub.sd-m-ts)/2−k.sub.sd-m-2)/2.

[0244] In the state that the blood volume is normal and the body temperature of the sensor placement site is also normal, a.sub.3 is not applicable. That is, if c.sub.4<k.sub.d-m-a<c.sub.5, then set a.sub.3=0. c.sub.4=(d.sub.4+(age-14)/8)/100, d.sub.4=23 to 35, preferably is 29; c.sub.5=(d.sub.5+(age-14)/8)/100, d.sub.5=27 to 39, preferably is33.

[0245] In extremely low or high blood pressure states, the information of diastolic period is unstable, and a.sub.3 is not applicable. That is, if k.sub.sd-m-0<d.sub.6 or k.sub.sd-m-2>d.sub.7, then set a.sub.3=0. d.sub.6=0.97 to 1.03, preferably is1.00; d.sub.7=1.52 to 1.58, preferably is 1.55.

[0246] In a normal blood pressure state, when the blood volume decreases or the body temperature of the sensor placement site decreases, a.sub.3 takes 67% of a positive value. That is, if k.sub.sd-m-0≥d.sub.6+0.10 and k.sub.sd-m-2≤d.sub.8 and k.sub.d-m-a≤c.sub.4, then a.sub.3=(c.sub.4−k.sub.d-m-a)×67/100. d.sub.8=1.42 to 1.48, preferably is 1.45.

[0247] In relatively low or high blood pressure states, when the blood volume decreases or the body temperature of the sensor placement site decreases, a.sub.3 takes 50% of a positive value. That is, if

[00052]$\{\begin{array}{c}{d}_6\le k_{\mathrm{sd}-m-0}<d_6+0.1\\ k_{d-m-a}\le c_4\end{array}\mathrm{or}$$\{\begin{array}{c}{d}_8\le k_{\mathrm{sd}-m-2}<d_7\\ k_{d-m-a}\le c_4\end{array},$

then a.sub.3=(c.sub.4−k.sub.d-m-a)×50/100;

[0248] In a normal blood pressure state, when the blood volume increases or the body temperature of the sensor placement site increases, a.sub.3 takes 62% of a negative value. That is, if k.sub.sd-m-0≥d.sub.6+0.10 and k.sub.sd-m-2≤d.sub.18 and k.sub.d-m-a≥c.sub.5, then a.sub.3=(c.sub.5−k.sub.d-m-a)×62/100;

[0249] In a state of relatively low or high blood pressure, when the blood volume increases or the body temperature of the sensor placement site increases, a.sub.3 takes 45% of the negative value. That is, if

[00053]$\{\begin{array}{c}{d}_6\le k_{\mathrm{sd}-m-0}<d_6+0.1\\ k_{d-m-a}\ge c_5\end{array}\mathrm{or}$$\{\begin{array}{c}{d}_8<k_{\mathrm{sd}-m-2}<d_7\\ k_{d-m-a}\ge c_5\end{array},$

then a.sub.3=(c.sub.5k.sub.d-m-a)×45/100.

[0250] Fourth correction variable a.sub.4:

[0251] The correction variables obtained in the step S4 further include a fourth correction variable a.sub.4, which is used for correcting T.sub.s in the case that the peripheral blood vessel dilation causes the lower limb blood pressure (relative to the radial artery blood pressure) to decrease. The applicable range of a.sub.4 is a.sub.422 0, and if a.sub.4 is greater, the lower limb blood pressure is much lowered relative to the radial artery blood pressure.

[0252] Contraction and expansion of peripheral blood vessels may cause the peak of the toe pulse wave to move back and forth on a time axis. If t.sub.max-toe≥t.sub.ch-toe, then

[00054]$k_{s-t-\mathrm{toe}}=\frac{t_{\max -\mathrm{toe}}+t_{\mathrm{ch}-\mathrm{toe}}+400}{\left(t_{s-\mathrm{toe}}+200\right)\times 2},$

otherwise

[00055]$k_{s-t-\mathrm{toe}}=\frac{t_{\max -\mathrm{toe}}+200}{t_{s-\mathrm{toe}}+200}.$

[0253] k.sub.s-t-toe is the ratio of the time from the start point to the peak of the toe pulse wave to the time of the systole, and 200 is an adjustment coefficient. When the highest point of the peak moves back beyond the midpoint, that is, when t.sub.max-toe≥t.sub.ch-toe, k.sub.s-t-toe is corrected; when the value of k.sub.s-t-toe is relatively large, indicating that the toe blood vessels dilate and the lower limb blood pressure decreases. That is, if k.sub.s-t-toe>0.8, then a.sub.4=k.sub.s-t-toe-0.8. If k.sub.s-t-toe≤0.8, a.sub.4 is not applicable, then set a.sub.4=0.

[0254] Fifth correction variable a.sub.5;

[0255] The correction variables obtained in the step S4 further include a fifth correction variable a.sub.5, the role and property acts are the same as those of the a.sub.4, and a.sub.5 is used for correcting T.sub.s in the case that the lower limb blood pressure decreases relative to the radial artery blood pressure.

[00056]$k_{s-m-\mathrm{toe}}=\frac{{\int }_0^{t_{s-\mathrm{toe}}}h\mathrm{dt}}{t_{s-\mathrm{toe}}{h}_{\max -\mathrm{toe}}},$

k.sub.s-m-toe is the ratio of the average height of the toe pulse wave systole to the maximum height h.sub.max-toe; if the k.sub.s-m-toe is large, indicating that the toe pulse wave peak is broad and flat, suggesting that the toe blood vessels dilate, and the lower limb blood pressure decreases relative to the radial artery. a.sub.5 has the same action and property as those of a.sub.4.

[0256] When the toe blood vessels do not dilate, as is not applicable. That is, if k.sub.s-m-toe<d.sub.9, then set a.sub.5=0. d.sub.9=0.67 to 0.73, preferably is 0.7.

[0257] When the toe blood vessels dilate and the highest point of the pulse wave peak shifts backward beyond the midpoint, as takes a positive value. That is, if k.sub.s-m-toe≥d.sub.9 and k.sub.s-t-toe≥0.8, then a.sub.5=k.sub.s-m-toe−d.sub.9.

[0258] When the toe blood vessels dilate and the highest point of the pulse wave peak does not exceed the midpoint, as takes half of the positive value. That is, if k.sub.s-m-toe≥d.sub.9 and k.sub.s-t-toe<0.8, then a.sub.5=(k.sub.s-m-toe−d.sub.9)/2.

[0259] Sixth correction variable a.sub.6;

[0260] The correction variables obtained in the step S4 further include a sixth correction variable a.sub.6, which represents a relative change in the area of two pulse waves, and is used for correcting T.sub.s when the toe blood vessels dilate and the lower limb blood pressure decreases relative to the radial artery blood pressure. The applicable range of a.sub.6 is a.sub.6>0.

[00057]$k_{s-m-\mathrm{toe}-\mathrm{ear}}=\frac{h_{\max }{\int }_0^{t_{s-\mathrm{toe}}}h\mathrm{dt}+\left(t_s+t_{s-\mathrm{toe}}\right)\times 100}{h_{\max -\mathrm{toe}}{\int }_0^{t_s}\mathrm{hdt}+\left(t_s+t_{s-\mathrm{toe}}\right)\times 100},$

[0261] k.sub.s-m-toe-ear is the ratio of the area of the toe pulse wave systole to the area of the ear pulse wave systole, and 100 is the adjustment coefficient; k.sub.s-m-toe-ear has the same role and property as those of k.sub.ts-toe-ear.

[0262] When the toe wave area is smaller than the ear wave area, the toe blood vessels have no relative dilation, and a.sub.6 is not applicable. That is, if k.sub.s-m-toe-ear<1.0, then set a.sub.6=0.

[0263] Under the first precondition that the toe area is larger than the ear area, toe blood vessels dilate more, and c.sub.6 takes a constant of 1.08 as the maximum value for use. That is, if k.sub.s-m-toe-ear>1.08, then set c.sub.6=1.08.

[0264] If the shape of the ear pulse wave is normal, a.sub.6 takes the maximum correction value. That is, if t.sub.s>220 and k.sub.sd-m-0>0.88, then a.sub.6=c.sub.6−1.0.

[0265] If the ear pulse wave appears as a very sharp forward-inclined triangle or the waveform is very narrow, indicating that the ear pulse waveform is severely irregular. At this time, the relative change between the two pulse waves is amplified, the correction value needs to be reduced for use, and a.sub.6 takes ⅓ of the maximum correction value. That is, if t.sub.s<160 or k.sub.sd-m-0<0.80, then a.sub.6=(c.sub.6−1.0)×0.34.

[0266] When the irregularity of the shape of the ear pulse wave is not too severe, a.sub.6 takes ⅔ of the maximum correction value. That is, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then a.sub.6=(c.sub.6−1.0)×0.67.

[0267] Under the second precondition that the toe area is larger than the ear area, the relative dilatation of the toe blood vessels is not too severe, and c.sub.6 takes a positive variable for use. That is, if 1.0≤k.sub.s-m-toe-ear≤1.08, then c.sub.6=k.sub.s-m-toe-ear−1.0.

[0268] If the shape of the ear pulse wave is normal, a.sub.6 takes a positive variable as the correction value. That is, if t.sub.s>220 and k.sub.sd-m-0>0.88, then a.sub.6=c.sub.6.

[0269] If the shape of the ear pulse wave is severely irregular, the relative change between the two pulse waves is amplified, the correction value needs to be reduced for use, and a.sub.6 takes ⅓ of the positive variable. That is, if t.sub.s≤160 or k.sub.sd-m-0≤0.80, then a.sub.6=c.sub.6×0.34.

[0270] When the irregularity of the ear pulse wave is not too severe, a.sub.6 takes ⅔ of the positive variable. That is, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then a.sub.6=c.sub.6×0.67.

[0271] Seventh correction variable a.sub.7;

[0272] The correction variables obtained in the step S4 further include a seventh correction variable a.sub.7, the role and property of a.sub.7 are the same as those of a.sub.6, and a.sub.7 represents the relative change of the systolic time of two pulse waves.

[00058]$k_{\mathrm{ts}-\mathrm{toe}-\mathrm{ear}}=\frac{t_{s-\mathrm{toe}}+825}{t_s+825},$

[0273] k.sub.ts-toe-ear is the ratio of the time of systole on the toe pulse wave to the time of the systole on the ear pulse wave, and 825 is an adjustment coefficient; increase in k.sub.ts-toe-ear suggests that the toe blood vessels dilate, and the lower limb blood pressure decreases relative to the radial artery blood pressure.

[0274] When the toe blood vessels have no relative dilation, a.sub.7 is not applicable. That is, if k.sub.ts-toe-ear<1.0, then set a.sub.7=0.

[0275] Under the first precondition that the toe blood vessels have severely relative dilation comparing to radial blood vessels, c.sub.7 takes a constant of 1.08 as the maximum value for use. That is, if k.sub.ts-toe-ear>1.08, then set c.sub.7=1.08.

[0276] If the form of the ear pulse wave is normal, a.sub.7 takes the maximum correction value. That is, if t.sub.s>220 and k.sub.sd-m-0>0.88, then a.sub.7=c.sub.7−1.0.

[0277] If the shape of the ear pulse wave is severely irregular, the relative change between the two pulse waves is amplified, the correction value needs to be reduced for use, and a.sub.7 takes ⅓ of the maximum correction value. That is, if t.sub.s<160 or k.sub.sd-m-0<0.80, then a.sub.7=(c.sub.7−1.0)×0.34.

[0278] If the irregularity of the shape of the ear pulse wave is not too severe, a.sub.7 takes ⅔ of the maximum correction value. That is, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then a.sub.7=(c.sub.7−1.0)×0.67.

[0279] Under the second precondition that the toe systolic time is greater than the ear systolic time, the relative dilatation of the toe blood vessels is not too severe comparing to that of radial blood vessels, and c.sub.7 takes a positive variable for use. That is, if 1.0≤k.sub.ts-toe-ear≤1.08, then c.sub.7=k.sub.ts-toe-ear−1.0.

[0280] If the shape of the ear pulse wave is normal, a.sub.7 takes a positive variable as the correction value. That is, if t.sub.s>220 and k.sub.sd-m-0>0.88, then a.sub.7=c.sub.7.

[0281] If the irregularity of the shape of the ear pulse wave is too severe, a.sub.7 takes ⅓ of the positive variable. That is, if t.sub.s≤160 or k.sub.sd-m-0≤0.80, then a.sub.7=c.sub.7×0.34.

[0282] If the irregularity of the shape of the ear pulse wave is not too severe, a.sub.7 takes ⅔ of the positive variable. That is, if 160<t.sub.s≤220 or 0.80<k.sub.sd-m-0≤0.88, then a.sub.7=c.sub.7×0.67.

[0283] The total correction value in the step S5 is

[00059]$A_m=\frac{1}{8}\underset{i=1}{\overset{8}{.Math.}}{A}_i,T_{\mathrm{sm}}=\frac{1}{8}\underset{i=1}{\overset{8}{.Math.}}{T}_{\mathrm{si}},$

where A is the sum of the correction variables a.sub.1-a.sub.7, where if a.sub.i=0, indicating that a.sub.i is not applicable. The step S6 is specifically: continuously acquiring the correction values in 8 cardiac cycles, and using the average value of the 8 values to overcome the disturbance of respiratory fluctuation, where the 8 values are selected by recursion, and the oldest matrix is eliminated each time when a new matrix is calculated. The correction method is: T.sub.sma=T.sub.sm(1−Am); where

[00060]$A=\underset{i=1}{\overset{7}{.Math.}}{a}_i,$

in which T.sub.sma is the T.sub.s after correction, T.sub.sm is the averaged T.sub.s in 8 cardiac cycles, Amis the averaged A in 8 cardiac cycles, A.sub.i is the total correction value in the i-th cardiac cycle, and T.sub.si is T.sub.s in the i-th cardiac cycle.

[0284] Finally, it should be noted that the above embodiments are only used for illustrating the technical solution of the present invention, rather than limiting the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art will appreciate that the technical solutions described in the foregoing embodiments can still be modified, or some or all the technical features can be equivalently replaced. These modifications or replacement do not make the essence of the corresponding technical solution detract from the scope of the technical solutions of the embodiments of the present invention, and are intended to be included within the scope of the claims and the description of the present invention.