Method of monitoring diving and a system for monitoring or planning a dive

Abstract

The invention concerns a method, device and computer program product for monitoring or planning a dive of a diver. The method includes providing data on the composition of gases breathed by the diver during the dive, providing data on the depth or ambient pressure of the diver, and using a model to provide a safe ascent profile for the diver based on the data on the composition of gases and on the depth or ambient pressure. According to the invention, the method further comprising detecting, based on the data on the composition of gases, a gas composition change which may lead to a deep tissue isobaric counter diffusion situation, and the model comprising means for immediately temporally retarding the ascent profile if such gas composition change is detected. The invention can be used to mitigate the harmful effects of dangerous breathing gas changes during diving.

Claims

1. A method of monitoring or planning a dive of a diver, comprising: providing data on a composition of breathing gases containing helium using a gas composition observation unit; providing data on the diving depth or the ambient pressure of the diver, using a pressure measurement unit; providing an original safe ascent profile for the diver based on the data on the composition of breathing gases and on the depth or ambient pressure; estimating a helium concentration in a tissue of the diver based on the data on the composition of breathing gases and on the depth or ambient pressure; monitoring the composition of gases for an abrupt rise in nitrogen partial pressure of said breathing gases which may lead to a deep tissue isobaric counter diffusion (ICD) situation; and in response to a detected abrupt rise in the nitrogen partial pressure of said breathing gases when the estimated helium concentration in the tissue of the diver is above a predefined level, providing a temporal ascent profile comprising an immediate temporal retardation of said original safe ascent profile.

2. The method according to claim 1, wherein the temporally retarded ascent profile comprises a first period of no ascending immediately following the detection of the abrupt rise in nitrogen partial pressure of the breathing gas when the breathing gas initially contains helium.

3. The method according to claim 2, wherein the first period has a duration of at least one minute.

4. The method according to claim 2, wherein the first period has a duration within the range of 1 to 5 minutes.

5. The method according to claim 2, wherein the temporally retarded ascent profile comprises a second period of slowed down ascent that ends at a time later than a corresponding period of the original ascent profile.

6. The method according to claim 1, wherein the method further comprises determining different gas diffusion parameters for a plurality of different tissue groups, and taking into account gas breathing, depth or ambient pressure history, and gas diffusion parameters to estimate the current concentration of gases in the different tissues.

7. The method according to claim 1, wherein the temporal retarding of the original ascent profile depends on the depth or ambient pressure at the time of the gas composition change.

8. The method according to claim 7, wherein the temporally retarded ascent profile is retarded more at high depths or ambient pressures than at lower depths or ambient pressures.

9. The method according to claim 1, wherein the temporal retarding of the original ascent profile is carried out in real time.

10. The method according to claim 1, wherein the method is carried out during diving in a diving computer for monitoring the dive.

11. The method according to claim 1, wherein the method is carried out in a desktop, laptop or handheld computer for planning the dive.

12. The method according to claim 1, wherein the providing the temporally retarded ascent profile comprises displaying said profile on the display of a dive computer.

13. A diving computer for monitoring a dive of a diver, comprising: a pressure sensing unit; a gas composition observation unit to sense gas composition and output data on the composition of gases breathed by the diver during the dive; a processor operably coupled to the pressure sensing unit and to the gas composition observation unit, the processor configured to receive the data on the composition of gases breathed by the diver during the dive from the gas composition unit, the processor configured to receive data on the depth or ambient pressure of the diver from the pressure sensing unit; an algorithm associated with the processor including a programmed model adapted to provide a safe ascent profile for the diver based on the data on the composition of gases and the depth or ambient pressure; a display configured to provide information on the safe ascent profile to the diver, wherein, the processor is adapted to: estimate a helium concentration in a tissue of the diver based on the data on the composition of breathing gases and on the depth or ambient pressure; detect a deep tissue isobaric counter diffusion (ICD) situation, based on the data on the composition of gases indicating an abrupt rise in nitrogen partial pressure of the breathing gas before the estimation of a helium concentration in the tissue of the diver has decreased to a predefined level, and wherein the processor is configured to immediately form and present on the display a temporally retarded ascent profile in response to the detected ICD situation.

14. The diving computer according to claim 13, wherein the temporally retarded ascent profile comprises a first period of no ascending, and wherein the first period has a duration of at least one minute.

15. The diving computer according to claim 13, wherein the temporally retarded ascent profile comprises a first period of no ascending, and wherein the first period is within the range of 1 to 5 minutes.

16. The diving computer according to claim 14, wherein the temporally retarded ascent profile comprises a second period of slowed down ascending compared with the ascending speed given by the model without the detection of the gas composition change.

17. The diving computer according to claim 13, being adapted to retard the ascent profile depending on the depth or ambient pressure at the time of detection of the gas composition change.

18. A method of monitoring or planning a dive of a diver, comprising: providing data on the composition of gases breathed by the diver during the dive using a gas composition observation unit; providing data on the depth or ambient pressure of the diver using a pressure measurement unit; outputting an original ascent profile to the diver to provide a safe ascent profile for the diver based on the data on the composition of gases and on the depth or ambient pressure; estimating a helium concentration in a tissue of the diver based on the data on the composition of breathing gases and on the depth or ambient pressure; detecting, prior to the estimated helium concentration in the tissue of the diver decreasing to a predefined level, based on the data on the composition of gases, an abrupt rise in nitrogen partial pressure of the breathing gas and a drop in the partial pressure of helium, when the breathing gas initially contains helium which may lead to a deep tissue isobaric counter diffusion (ICD) situation; and computing a temporally retarded ascent profile based on the partial pressures, predefined criteria and the current depth; outputting a temporally retarded ascent profile in response to the detected abrupt rise in nitrogen partial pressure of the breathing gas when the breathing gas initially contains helium, the temporally retarded ascent profile comprising an immediate temporal retardation of the original ascent profile.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates as a flow chart the method according to a preferred embodiment of the present invention.

(2) FIG. 2 illustrates in more detail portion of the method according to another preferred embodiment of the present invention.

(3) FIG. 3a illustrates graphical representations of ascent profiles (depth vs. time) with safe (non-ICD causing) gases and ICD-causing gases calculated using a conventional method.

(4) FIG. 3b illustrates graphical representations of three separate ascent profiles (depth vs. time).

(5) FIG. 4 is a block diagram a diving computer according to another preferred embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(6) With reference to FIG. 1 according to a preferred embodiment, the present method includes in step 11 measuring (during diving) or retrieving programmed data on (during planning) the composition, i.e., partial pressures of components, of the breathing gas at each moment. In addition, ambient pressure is typically measured or estimated at each moment in step 12. This data is used to calculate a safe ascent profile in step 13 according to a pre-programmed decompression model.

(7) As the ICD situation may only occur when changing gas composition, the changes are monitored. When a change is detected in step 14 through measurement of partial pressures of the gases or by other means in step 14, an ICD penalty is sanctioned for the diver in step 15.

(8) With reference to FIG. 2, the Deep Tissue ICD situation detection and ICD penalty decision-making can be carried out in the following way. First, the gas concentration is continuously estimated in different tissues using a suitable decompression model (step 21). Such models are known in the art and the present invention is not limited to any particular decompression model. Preferably, the decompression model utilizes at least 5, typically at least 9 tissue groups having different gas diffusion characteristics to provide sufficient reliability of estimation. At the same time, and in particular during the ascending phase of the dive, the method comprises monitoring changes in nitrogen partial pressure in the breathing gas (step 22). If the change in the partial pressure exceeds predefined criteria, i.e. is high or fast enough (step 23), there is a potential ICD situation and the ascent profile is recalculated (step 24) to comprise an ICD penalty to avoid or mitigate harmful ICD effects in that tissue(s). If no alarming change in the nitrogen partial pressure is detected, the diver may be advised to continue ascending using a previously calculated ascent profile or continuous profile calculation method which is not changed (step 25) without an ICD penalty.

(9) According to one embodiment, the ICD penalty is determined in the following way: 1. The partial pressure of nitrogen is monitored. If the change of the partial pressure rises above a predefined threshold (e.g. 0.5 bar), an ascending stop having a length is sanctioned. 2. The partial pressure of helium is monitored. If a drop the partial pressure of helium is detected and criterion 1 above is fulfilled, the length of the ascending stop is prolonged. 3. If the summed-up change of nitrogen and helium partial pressures exceeds predefined criteria (e.g. total change greater than 0.75 bar), an additional slowed-down ascending profile is sanctioned for the diver.

(10) According to one embodiment, the strength of the ICD penalty is affected by the depth at which the ICD situation occurs. Thus, the ICD penalty determination function or algorithm has the current depth (or ambient pressure) as a parameter. Typically, the ICD penalty is heavier at larger depths than at smaller depths because also the risk for potential physiological harmful effects is proportional to the depth.

(11) The ICD penalty determination described above is given by way of example only and it may be varied to provide an alternatively determined different levels of penalty, depending on the seriousness of the wrong gas change observed based on observing the partial pressures of one or more of the breathing gases during the ascending phase of the dive.

(12) FIG. 3a shows two exemplary ascent profiles calculated using a prior art calculation method. In a first ascent profile 50 of a dive, the ascent profile 50 is made using safe gases, i.e. no dangerous gas exchanges have been made. In a second ascent profile 52, the second ascent profile 52 represents a situation, where a dangerous (ICD-causing) gas change is made at a depth of 40 m. The profile calculation algorithm is the same in both cases. As can be seen, the gas exchange does not cause any retarding of the ascent profile but in fact causes a small immediate rise in the proposed ascent rate. Also the proposed surfacing takes place sooner in the ICD situation than in the safe situation, which can be detrimental for the health of the diver.

(13) FIG. 3b illustrates a similar case with a different calculation method. The middle curve 62 shows an ascent profile made with safe gases. The topmost curve 64 shows as an ascent profile with a dangerous gas change being made at a depth of about 35 m. As can be seen, this method is even more sensitive to the gas change, but again in the wrong direction. The proposed ascending rate of the topmost curve 64 is actually considerably accelerated by the wrong gas change, which is typical to most existing calculation methods.

(14) The undermost curve 60 of FIG. 3b is according to a preferred embodiment of the present invention. In this example, the temporally retarded ascent profile comprises a period of no ascending immediately after the detection of the ICD situation. This period causes the potential harmful effects of the dangerous gas change to be as small as possible. After the ICD penalty, the ascending continues. Now that the ICD effects have been minimized, ascending may continue according to the original model (at the slope of the topmost curve) or at a further slowed-down rate. Due to the penalty and potential further retarding, also the surfacing takes place later than in the two other cases.

(15) The ascending stop preferably has a duration of at least one minute, preferably at least two minutes, and more preferably within the range of 1 to 5 minutes. This ensures that the gas cross diffusion in the tissue has reached a safe level and ascending may continue.

(16) According to one embodiment, the temporally retarded ascent profile comprises, in addition to a full temporary ascending stop, a second period of slowed down ascending. Slowed down ascending means that the ascending speed, i.e. slope of the ascending profile, is smaller compared with the ascending speed given by the model without the detection of the ICD situation.

(17) According to one embodiment, the detection of the ICD situation is carried out by detecting an abrupt rise in nitrogen partial pressure when the breathing gas initially contains helium.

(18) The decompression model typically comprises different gas diffusion parameters for a plurality of different tissue groups. Tissue groups have been formed based on their tendency to allow gas diffusion in/out of the tissue from/to blood circulation, i.e. their gas diffusion parameters. The model also takes into account takes into account gas breathing history and depth or ambient pressure history to estimate the current concentration of gases in the different tissues. The model may also take into account other factors, such as ventilation. The model is run continuously. The safe ascending profile is determined so that in all tissue groups the gas levels and therefore also the gas diffusion rates remain at a predefined safe rate. In an ICD situation caused by the diver's wrong gas change, such safe levels and rates cannot be guaranteed. Undesired consequences and risks can, however, be minimized using the present invention.

(19) According to one embodiment of the invention, the method is carried out during diving in a diving computer for real-time monitoring a dive and real-time guiding of the diver for safe ascending.

(20) FIG. 4 illustrates as a block diagram a diving computer 40 according to one embodiment of the invention. The diving computer 40 comprises a computing unit or processor 43 which is in functional connection with a pressure measurement unit 41 and gas composition observation unit 42. The computing unit runs the decompression model and the ICD detection algorithm discussed above. In addition, there is a display for displaying or communicating information on the ascent profile for the diver and there may be also alerting means for indicating the diver of a detected ICD situation and ICD penalty sanctioned.

(21) In an alternative embodiment the method is carried out in a desktop, laptop or handheld computer, such as a mobile phone or tablet computer, for planning a dive. In such a computer, the pressure measurement unit and gas composition observation unit are replaced with computer-readable data on the pressure and gas composition during the dive planned.

(22) While the preferred embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. One of skill in the art will understand that the invention may also be practiced without many of the details described above. Accordingly, it will be intended to include all such alternatives, modifications and variations set forth within the spirit and scope of the appended claims. Further, some well-known structures or functions may not be shown or described in detail because such structures or functions would be known to one skilled in the art. Unless a term is specifically and overtly defined in this specification, the terminology used in the present specification is intended to be interpreted in its broadest reasonable manner, even though may be used conjunction with the description of certain specific embodiments of the present invention.