Weaning from ventilation using capnography

Abstract

Devices and systems for monitoring weaning of a subject from a respiratory ventilator including a processing logic configured to characterize distinct patterns in a series of CO.sub.2 waveforms, the distinct patterns indicative of the effectiveness of a weaning process; and to provide an indication relating to the effectiveness of the weaning process.

Claims

1. A device for monitoring effectiveness of weaning subject from a respiratory ventilator, the device comprising: a monitoring unit configured to measure and/or receive measurements of a CO.sub.2 concentration over time in the subject's expired breath and to provide a series of CO.sub.2 waveforms based on the monitored concentration; a processor configured to: identify a distinct pattern in the series of CO.sub.2 waveforms; determine a frequency and/or an extent of the distinct pattern in the series of CO.sub.2 waveforms; and provide an indication relating to the effectiveness of the weaning process, based on the determined frequency and/or extent of the distinct pattern; wherein an increase in the frequency and/or the extent of the distinct pattern, as compared to a baseline, is indicative of a deterioration in the weaning effectiveness.

2. The device of claim 1, wherein said distinct pattern is selected from a group consisting of “sigh events”, “spike events” and “pools”.

3. The device of claim 1, wherein said processor is further configured to determine one or more parameters of the ventilator based on the determined frequency and/or extent of the distinct patterns in the series of CO.sub.2 waveforms.

4. The device of claim 3, wherein the one or more parameters of the ventilator comprises a change in the level of support to the ventilation, allowing the patient to rest from weaning attempts, changing a mode/program of weaning or any combination thereof.

5. The device of claim 3, wherein determining the one or more parameter of the ventilator is further based on one or more additional parameters selected from the group consisting of: age of the subject, medical condition of the subject, medical history of the subject and medications administered to the subject.

6. The device of claim 3, wherein determining the one or more parameter of the ventilator is further based on one or more additional parameters selected from the group consisting of: respiration rate, tidal volumes, minute ventilation (the total lung ventilation per minute), inspiration rate and expiration rate at ambient pressure in the absence of ventilator assistance, ventilator mode and ventilator setup parameters.

7. The device of claim 1, wherein characterizing distinct patterns in a series of CO.sub.2 waveforms comprises segmenting the series of CO.sub.2 waveforms into breaths (waveforms), and calculating for each breath one or more features.

8. The device of claim 7, wherein the one or more features comprise: area under the curve (AUC), breath duration (inhalation, expiration or both), I to E ratio, maximal CO.sub.2 value, minimal CO.sub.2 value or any combination thereof.

9. The device of claim 1, wherein characterizing distinct patterns in the series of CO.sub.2 waveforms comprises determining the ratios between the distinct patterns.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Exemplary embodiments are illustrated in referenced figures. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive. The figures are listed below.

(2) FIGS. 1 A and B show series of CO.sub.2 waveforms in a weaning patient, according to some embodiments of the invention;

(3) FIG. 2 shows a series of CO.sub.2 waveforms in a weaning patient, according to some embodiments of the invention;

(4) FIGS. 3 A and B show series of CO.sub.2 waveforms in a weaning patient, according to some embodiments of the invention;

(5) FIG. 4 shows a series of CO.sub.2 waveforms in different ventilation modes (CPAP, SIMV and VS), according to some embodiments of the invention;

(6) FIG. 5 shows a “zoom-in” series of CO.sub.2 waveforms taken from the CPAP section of FIG. 4, according to some embodiments of the invention;

(7) FIG. 6 shows a “zoom-in” series of CO.sub.2 waveforms taken a few minutes after starting the VS section of FIG. 4, according to some embodiments of the invention; and

(8) FIG. 7 shows a “zoom-in” series of CO.sub.2 waveforms taken from the VS section of FIG. 4, according to some embodiments of the invention.

DETAILED DESCRIPTION

(9) In accordance with some embodiments of the invention, certain types of distinct breathing patterns (characteristics) in data obtained from ventilated patients during weaning process were found and evaluated.

(10) According to some embodiments, the CO.sub.2 signal obtained from expired air of a subject was segmented into breaths (waveforms), and one or more features for each breath were calculated. Example of such features include area under the curve (AUC), breath duration (inhalation, expiration or both), I to E ratio (the ratio between inhalation to expiration in a breath), maximal CO.sub.2 value, minimal CO.sub.2 value, presence of small “dip(s)” in the waveform plateau or in the inhalation part of the breath (a dip in a waveform may be due to breathing effort that the ventilation does not capture), and other features.

(11) The extent and/or frequency of appearance of these features may, over time, create certain patterns. According to some embodiments, these patterns may be indicative to the effectiveness of a weaning process. Three patterns were determined by their relative value of a feature or values of a set of features (as discussed herein according to some embodiments) compared to a pre-defined base-line or to an average or median feature value before weaning started (for example, when full ventilation was still applied) or to an average or median feature value obtained during a specific time period (for example the last X hours, such as 2-10, 12 to 24). The following three patterns were determined:

(12) 1) Sigh Events: breaths with relatively large AUC (for example, compared to a an average or median AUC value before weaning started or to the average or median AUC value obtained during a specific time period) or relatively high breath duration (for example, compared to an average or median breath duration value before weaning started or to an average or median breath duration value obtained during a specific time period) or any other typical feature.

(13) 2) Spike Events: breaths with very small AUC (for example, compared to a an average or median AUC value before weaning started or to the average or median AUC value obtained during a specific time period) or relatively small breath duration and/or relatively low maximal CO.sub.2 or any other typical feature (for example, compared to the respective feature value before weaning started or to an average or median respective feature value obtained during a specific time period).

(14) 3) Pools: group of breaths with relatively low AUC (for example, compared to a an average or median AUC value before weaning started or to the average or median AUC value obtained during a specific time period) or low maximal CO.sub.2 or low breath duration or any other typical feature (for example, compared to the respective feature value before weaning started or to an average or median respective feature value obtained during a specific time period).

(15) FIGS. 1-3 show series of CO.sub.2 waveforms of weaning patients, according to some embodiments of the invention. In each one of FIGS. 1-3 the distinct patterns (FIG. 1: “sigh events”, FIG. 2. “spike events” and FIG. 3 “pools”) are marked by arrows and can easily be observed among the “regular” breaths.

(16) The patterns appear in different frequencies during weaning, at different modes of ventilation (CPAP, SIMV and VS), as shown in FIG. 4. The arrows indicate the ventilation mode at that time.

(17) FIG. 5 shows a “zoom-in” series of CO.sub.2 waveforms taken from the CPAP section of FIG. 4, according to some embodiments of the invention. The deterioration of the patient's condition with time, during CPAP ventilation can clearly be seen by the higher frequency of “pools” (see arrow).

(18) FIG. 6 shows a “zoom-in” series of CO.sub.2 waveforms taken a few minutes after starting the VS section of FIG. 4, according to some embodiments of the invention. The “sigh events” are marked be arrows.

(19) FIG. 7 shows a “zoom-in” series of CO.sub.2 waveforms taken from the VS section of FIG. 4, according to some embodiments of the invention. The deterioration of the patient's condition with time, during VS can clearly be seen by the higher frequency of “pools” (marked be horizontal arrows) in addition to the “sigh events” (marked be arrows).

(20) It is also noted that the some of the characteristics (for example, the pooling effect) occurred together with changes in the Respiration Rate.

(21) The appearance of the distinct patterns (for example, the “sigh events”, “spike events” and “pools”), their frequencies and extent, could serve as indicators for progress of the weaning process. Of course, the three distinct patterns disclosed herein are merely examples and other distinct patterns (characteristics) that appear in the CO.sub.2 waveforms or waveforms series may also be indicative to the progress and effectiveness of the weaning process.

(22) According to some embodiments, the appearance of CO.sub.2 distinct patterns their frequencies and/or extent, optionally together with additional ventilator parameter (such as ventilation modes, tidal volume, minute ventilation, and PEEP (Positive End-Expiratory Pressure)) may serve as indicators to the progress and effectiveness of the weaning process.

(23) The appearance of the CO.sub.2 distinct patterns, their frequencies and/or extent, together with additional ventilator parameter (such as ventilation modes, tidal volume, minute ventilation and PEEP) may also serve as indicators for ventilation related conditions such as air-leaks, a-synchrony, rebreathing, changes in compliance, obstruction and triggering effort.

(24) Referring to the term “a-synchrony”: During weaning the patient breath spontaneous breaths and the ventilator “helps” by “filling in” and adding flow, for example, or in other ways (depending on the ventilator mode). A-synchrony is when the settings of the ventilator are such that it interferes with the spontaneous breathing. For example, the patient tries to start a new breath in the middle of a ventilator breath.

(25) Referring to the term “Rebreathing”: breathing a new breath without finishing the previous breath.