US20150151072A1 - Ventilation analysis and monitoring - Google Patents
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- US20150151072A1 US20150151072A1 US14/619,976 US201514619976A US2015151072A1 US 20150151072 A1 US20150151072 A1 US 20150151072A1 US 201514619976 A US201514619976 A US 201514619976A US 2015151072 A1 US2015151072 A1 US 2015151072A1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/10—Preparation of respiratory gases or vapours
- A61M16/1005—Preparation of respiratory gases or vapours with O2 features or with parameter measurement
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/083—Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
- A61B5/0836—Measuring rate of CO2 production
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/087—Measuring breath flow
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0003—Accessories therefor, e.g. sensors, vibrators, negative pressure
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0003—Accessories therefor, e.g. sensors, vibrators, negative pressure
- A61M2016/003—Accessories therefor, e.g. sensors, vibrators, negative pressure with a flowmeter
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/10—Preparation of respiratory gases or vapours
- A61M16/1005—Preparation of respiratory gases or vapours with O2 features or with parameter measurement
- A61M2016/102—Measuring a parameter of the content of the delivered gas
- A61M2016/103—Measuring a parameter of the content of the delivered gas the CO2 concentration
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2205/00—General characteristics of the apparatus
- A61M2205/33—Controlling, regulating or measuring
- A61M2205/3331—Pressure; Flow
- A61M2205/3334—Measuring or controlling the flow rate
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2205/00—General characteristics of the apparatus
- A61M2205/58—Means for facilitating use, e.g. by people with impaired vision
- A61M2205/583—Means for facilitating use, e.g. by people with impaired vision by visual feedback
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2230/00—Measuring parameters of the user
- A61M2230/40—Respiratory characteristics
- A61M2230/43—Composition of exhalation
- A61M2230/432—Composition of exhalation partial CO2 pressure (P-CO2)
Definitions
- Embodiments of the disclosure relate to ventilation analysis and monitoring in patients.
- Capnography is often defined as the measurement of the level of carbon dioxide (CO 2 ) in exhaled and/or inhaled breath. Since infrared light was found to be absorbed particularly well by CO 2 , capnographs usually measure infrared absorption in the breath gasses, which indicates the level of CO 2 in these gasses. Other measurement technologies exist as well.
- the information obtained from a capnographic measurement is sometimes presented as a series of waveforms, representing the partial pressure of CO 2 in the patient's exhaled breath as a function of time.
- Capnography is considered to be a prerequisite for safe intubation and general anesthesia, as well as for correct ventilation management.
- Breath flow dynamics is another ventilation-related factor that is sometimes being measured. Whereas capnography is usually indicative of physiological aspects of ventilation, breath flow dynamics measurement is often indicative of the mechanics of respiration—the inhalation and exhalation activity of patient's lungs.
- a ventilation analysis system comprising: an interface module adapted to receive a carbon dioxide (CO 2 ) signal and a breath flow dynamics signal; and control logic adapted to produce a ventilation indicator, based on a mutual analysis of said CO 2 signal and said breath flow dynamics signal.
- CO 2 carbon dioxide
- a method for ventilation analysis comprising: receiving a CO 2 signal and a breath flow dynamics signal; and mutually analyzing the CO 2 signal and the breath flow dynamics signal, to produce a ventilation indicator.
- said ventilation indicator comprises an estimated CO 2 waveform, an End-Tidal CO 2 (EtCO 2 ) value and/or a minute CO 2 value.
- system further comprises a CO 2 sensor adapted to produce said CO 2 signal.
- said CO 2 sensor comprises a wireless CO 2 sensor.
- said CO 2 sensor comprises a CO 2 sensor having a response time of 100 milliseconds (ms) or more, 500 ms or more and/or 900 ms or more.
- system further comprises a breath flow dynamics sensor adapted to produce said breath flow dynamics signal.
- said breath flow dynamics sensor comprises a wireless breath flow dynamics sensor.
- said breath flow dynamics sensor comprises a flow sensor, an acoustic sensor, a thermal sensor, a chest movement detector, a computer-aided video analyzer and/or a Doppler radar.
- said interface module is further adapted to receive a Saturation of Peripheral Oxygen (SpO 2 ) signal.
- SpO 2 Peripheral Oxygen
- system further comprises an SpO 2 sensor adapted to produce said SpO 2 signal.
- the receiving of the CO 2 signal comprises wirelessly receiving the CO 2 signal.
- the CO 2 signal comprises discrete Partial Pressure CO 2 (PCO 2 ) readings taken every 100 ms or more, every 500 ms or more and/or every 900 ms or more.
- PCO 2 Partial Pressure CO 2
- the receiving of the breath flow dynamics signal comprises wirelessly receiving the breath flow dynamics signal.
- the breath flow dynamics signal comprises a flow measurement, an acoustic measurement, a thermal measurement, a chest movement measurement, a computer-aided video analysis and/or a Doppler radar signal.
- the method further comprises receiving an SpO 2 signal.
- FIG. 1 schematically shows a block diagram of a ventilation analysis system
- FIG. 2 schematically shows a graph of CO 2 and breath flow dynamics signals
- FIG. 3 schematically shows an estimated CO 2 waveform
- FIG. 4 schematically shows an adult normal capnogram
- FIGS. 5A-C schematically show capnogram patterns.
- An aspect of some embodiments of the disclosure relates to a ventilation analysis and/or monitoring system.
- the system may be adapted to interface with one or more sensors to receive a carbon dioxide (CO 2 ) signal and a breath flow dynamics (hereinafter “BFD”) signal, both pertaining to a patient.
- CO 2 carbon dioxide
- BFD breath flow dynamics
- the received signals may be mutually analyzed, to produce a ventilation indicator that may assist a clinician in assessing the patient's ventilatory condition.
- the CO 2 signal may be received from a CO 2 sensor adapted to operate with a relatively slow response time.
- this may enable the use of a relatively small, power efficient and/or simple sensor, compared to conventional CO 2 sensors commonly used today in conjunction with capnographs.
- Various CO 2 sensors are being constantly introduced to the market, where one of the major improvements these sensors offer is faster and faster response times.
- Response time is often defined as the duration between two consecutive samples taken by the CO 2 sensor. For example, a sensor having a response time of 50 milliseconds (ms), is able to measure (or “read”) momentary breath CO 2 concentration once every 50 ms, which amounts to 20 measurements per second.
- a faster response time means a shorter response time and therefore more measurements per second.
- CO 2 waveform is a graphic representation of the breath CO 2 concentration over time, which is sometimes displayed by capnographs. If more CO 2 readings are available per a unit of time, the resolution of the waveform increases, and so does its accuracy and the amount of meaningful information it may relay to a clinician. Therefore, newly-introduced capnographs often aim to offer faster response times than before. However, there is often a tradeoff between response time and factors like manufacturing complexity, power consumption, physical size and weight, cost and/or the like.
- the ventilation analysis and/or monitoring system is advantageously adapted to provide a clinically-meaningful ventilation indication while utilizing a CO 2 sensor having a relatively slow response time, such as a response time in the range of 100-300 ms, 300-500 ms, 500-700 ms, 700-900 ms, 900-1100 ms or above 1100 ms.
- a CO 2 sensor may nonetheless have a relatively fast response time, such as a response time of below 100 ms.
- the ventilation analysis and/or monitoring system may provide the ventilation indication by pairing a signal received from the CO 2 sensor with a signal received from a BFD sensor.
- BFD which is often indicative of the mechanics of respiration—the inhalation and exhalation activity of patient's lungs, may be measured using various methods known in the art. For example, a flow sensor is sometimes positioned about the patient's nostrils or mouth, directly measuring the dynamics of inward and/or outward gas flow. If the patient is intubated and given artificial respiration, a measurement of the BFD may be provided by the respirator.
- Measurement of BFD may also be performed essentially indirectly, such as using an acoustic sensor sensitive to sound emitted during respiration, a thermal sensor sensitive to temperature changes during respiration, a chest movement detector attached to the patient's body, a microwave Doppler radar system adapted to produce a signal indicative of chest movement and/or a computer-aided video analyzer adapted to visually recognize chest movement.
- BFD may provide information such as a numerical respiration rate value and/or a visual indication of exhalation/inhalation cycles over a time axis.
- a respiration rate is often defined as the number of exhalation/inhalation cycles per minute, and is commonly considered a clinical parameter of great importance.
- a visual indication may include a graph showing the exhalation/inhalation spread over a time axis.
- FIG. 1 shows a block diagram 100 of a ventilation analysis and/or monitoring system (hereinafter “system”) 102 , in accordance with an embodiment.
- System 102 may be essentially what is often referred to as a capnograph, or be incorporated within a capnograph.
- System 102 may include an interface module 104 adapted to interface with a CO 2 sensor 110 and with a BFD sensor 112 , which measure breath CO 2 concentration and BFD, respectively, of a patient.
- the interface with each of CO 2 sensor 110 and BFD sensor 112 may be wired or wireless.
- CO 2 sensor 110 and BFD sensor 112 are enclosed within a single physical unit, which may be referred to as a multi-purpose sensor adapted to sense both CO 2 and BFD.
- Interface module 104 may further be adapted to interface with an SpO 2 sensor (not shown), to receive an SpO 2 signal.
- Interface module 104 may periodically receive a CO 2 signal from CO 2 sensor 110 and a BFD signal from BFD sensor 112 , and make these signals available to a control logic 106 .
- Control logic 106 may mutually analyze the CO 2 and BFD signals, and output (or “produce”) one or more ventilation indicator(s) 114 based on both signals.
- CO 2 waveform 116 An example of a ventilation indicator is a CO 2 waveform 116 .
- conventional capnographs may require a fast-response CO 2 sensor in order to produce a CO 2 waveform of a sufficiently high resolution. Nonetheless, CO 2 waveform 116 may be produced based on the BFD signal and on the CO 2 signal which may be of a slow-response CO 2 sensor. The creation of CO 2 waveform 116 is further discussed below.
- Ventilator(s) 118 may be created from the mutual analysis of the BFD and CO 2 signals.
- a ventilation indicator may be end-tidal CO 2 (EtCO 2 ), minute EtCO 2 and/or the like. These ventilation indicators are further discussed below.
- System 102 may be further adapted to relay to a clinician, visually and/or sonically, SpO 2 values derived from the received SpO 2 signal.
- System 102 may be embodied in a computerized device having input, output and processing abilities to carry out operations of interface module 104 and control logic 106 .
- system 102 may be an essentially stationary computerized device positioned next to a patient's hospital bed or at a central location in the hospital (if remote monitoring of a patient is desired).
- system 102 may be an essentially mobile computerized device adapted to be carried by an emergency clinician, in an ambulance and/or the like.
- a patient whose ventilatory condition is desired to be monitored may be connected to CO 2 sensor 110 and BFD sensor 112 , which transmit their readings to system 102 for analysis.
- the output of system 102 namely—ventilation indicator 114 , may be relayed to the clinician by way of visual display on a monitor, sonic indication and/or the like.
- system 102 may provide a ventilation indicator or different ventilatory status having enhanced reliability.
- the enhanced reliability may be achieved since CO 2 and BFD are two measures of essentially the same system—the body ventilatory system. Each of these measures offers a different perspective of essentially the same bodily system, and therefore these measures complement each other. Monitoring both measures may allow the filtering out of issues such as false or poor readings arriving from one of the two sensors due to a defect or an error, and/or cases in which the patient is talking, eating, coughing and the like and therefore temporarily exhibiting irregular CO 2 and/or BFD signals.
- FIG. 2 shows a graph 200 of exemplary signals that may be transmitted from CO 2 sensor 110 and BFD sensor 112 to interface module 104 ( FIG. 1 ).
- a BFD signal 202 may indicate a respiratory state of the patient, such as whether the patient is currently exhaling or inhaling, and/or the intensity of the exhaling/inhaling at any particular moment.
- a concave shape 202 a of BFD signal 202 may be indicative of inhalation
- a convex shape 202 b of the BFD signal may be indicative of exhalation.
- a partial pressure CO 2 (PCO 2 ) signal shown as discrete PCO 2 readings 204 , may indicate one or more physiological aspects of ventilation. Horizontal distances between PCO 2 readings 204 may be dictated by a response time of the sensor that performed the reading. Since PCO 2 during inhalation is zero, zero readings 204 a may be present during the inhalation. Other readings 204 b, usually higher than zero, may be present during exhalation.
- a PCO 2 average signal 206 may show an average of PCO 2 over time.
- a CO 2 sensor may average PCO 2 readings it performs, producing PCO 2 average signal 206 , by using a capacitor and/or similar electronic means.
- PCO 2 average signal 206 is shown in the figure as a straight line 206 a, for illustrative purposes only.
- a CO 2 sensor may transmit either PCO 2 readings 204 , PCO 2 average signal 206 , or both.
- FIG. 3 shows an exemplary estimated CO 2 waveform 300 , which is optionally the ventilation indicator produced by the ventilation analysis and/or monitoring system.
- the exemplary estimated CO 2 waveform 300 may contain trapezoid-like shapes, such as trapezoid 302 .
- An upsurge curve 302 a of trapezoid 302 indicates a beginning of an exhalation
- a gradually rising curve 302 b indicates a central part of the exhalation
- a drop curve 302 c indicates an ending of the exhalation.
- a zero-value curve 302 d indicates an inhalation.
- estimated CO 2 waveform 300 may be constructed by way of the mutual analysis of the CO 2 and BFD signals, despite the slow response time of the CO 2 sensor. For example, if PCO 2 average signal 206 ( FIG. 1 ) is provided by the CO 2 sensor, it may be possible to calculate what was the PCO 2 during exhalation. For instance, if the average PCO 2 is 20 , and it is known that: (a) during inhalation the PCO 2 is zero; and (b) the duty cycle of the exhalation and inhalation, as apparent from the BFD signal, is 50%—then the average PCO 2 during exhalation is 40 .
- a trapezoid such as trapezoid 302 , may then be constructed according to a mathematical constraint that the trapezoid's average value must be 40 .
- Another mathematical factor that may be helpful in the construction of the trapezoid is that the product of the average PCO 2 during exhalation (in our example, 40 ) and the duration of the exhalation (which may be inferred from the BFD signal) is equal to an area that should be delimited between the constructed trapezoid and the time axis.
- the BFD signal may provide information pertaining to starting and ending points of the inhalations and exhalations, so that any constructed trapezoids, such as trapezoid 302 , may be synchronized with breath cycles.
- a general shape of a trapezoid may be available through other readings 204 b ( FIG. 2 ).
- One or more methods may be employed in order to fill in the gaps between other readings 204 b and enhance the resolution of the trapezoid.
- other readings 204 b FIG. 2
- other readings 204 b FIG. 2
- a location and an estimated shape of parts like upsurge curve 302 a, gradually rising curve 302 b, drop curve 302 c and zero-value curve 302 d may be determined.
- the ventilation indicator is an EtCO 2 value.
- EtCO 2 is often defined as the partial pressure of CO 2 at a point in time when CO 2 values stop increasing and on the verge of dropping.
- An exemplary EtCO 2 point 304 is shown in FIG. 3 .
- the creation of EtCO 2 indication may be enabled, despite the slow response time of the CO 2 sensor, via mathematical calculation.
- the EtCO 2 may be calculated similar to the way the CO 2 waveform may be created, as discussed above. If an estimated shape of a trapezoid is calculated, EtCO 2 for each trapezoid may also be calculated.
- the ventilation indicator is a minute CO 2 value. Minute CO 2 is commonly referred to as the total production of CO 2 per minute. By correlating the BFD signal with the PCO 2 average or discrete readings, minute CO 2 may be calculated. More specifically, when using a PCO 2 average signal, inhalation and exhalation cycles may be used to determine the PCO 2 average during exhalation alone. This exhalation PCO 2 may then be multiplied by a respiration rate (also obtainable from the BFD signal) to output minute CO 2 .
- a respiration rate also obtainable from the BFD signal
- FIG. 4 shows an adult normal capnogram 400 as known in the art.
- Adult normal capnogram 400 in spontaneously breathing subjects may be characterized by four distinct phases:
- Point 408 which is the intersection of the alveolar plateau and the inspiratory limb, is often referred to as the End-Tidal CO 2 (EtCO 2 ).
- An angle ⁇ which designates the angle between the ascending phase curve and the X axis, is referred to as a “takeoff angle”.
- An angle ⁇ which designates the angle between the alveolar plateau and the X axis, is referred to as an “elevation angle”.
- capnogram 400 An amplitude of capnogram 400 is dependent on EtCO 2 concentration. A width of capnogram 400 is dependent on expiratory time.
- the shape of capnogram 400 is generally rectangular, formed by almost perpendicular ascending phase (indicating absence of lower airway obstruction) and inspiratory limb (no upper airway obstruction).
- FIG. 5A shows a capnogram 500 demonstrating elevated EtCO 2 with a good alveolar plateau.
- a corresponding graph 502 shows a 30-minute trend exhibiting a constant but elevated EtCO 2 .
- Possible causes may be: (a) inadequate minute ventilation or hypoventilation; (b) respiratory depressant drugs; (c) hyperthermia, pain and/or shivering.
- FIG. 5B shows a capnogram 504 demonstrating gradually increasing EtCO 2 .
- a corresponding graph 506 shows a 30-minute trend exhibiting this gradual increase.
- Possible causes may be: (a) hypoventilation; (b) rising body temperature and/or malignant hyperthermia; (c) increased metabolism; (d) partial airway obstruction; (e) absorption of CO 2 from exogenous source.
- FIG. 5C shows a capnogram 508 demonstrating an alveolar cleft.
- a corresponding graph 510 shows a 30-minute trend exhibiting constant EtCO 2 levels. Possible causes may be inadequate neuromuscular blockade and/or emergence from blockade.
- each of the words “comprise” “include” and “have”, and forms thereof, are not necessarily limited to members in a list with which the words may be associated.
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Abstract
A ventilation analysis system comprising an interface module adapted to receive a carbon dioxide (CO2) signal and a breath flow dynamics signal, and control logic adapted to produce a ventilation indicator, based on a mutual analysis of the CO2 signal and the breath flow dynamics signal. The ventilation indicator may be, for example, an estimated CO2 waveform, an End-Tidal CO2 (ETCO2) value, and/or a minute CO2 value.
Description
- This application is a continuation of U.S. patent application Ser. No. 12/999,111 (published as US 2011/0105935), filed Dec. 15, 2010, which is the U.S. National Stage of International Application No. PCT/IL2009/000651, filed Jun. 30, 2009, which claims the benefit of U.S. Provisional Patent Application No. 61/129,474, filed Jun. 30, 2008, the contents of each of which are expressly incorporated herein in their entireties by this reference.
- Embodiments of the disclosure relate to ventilation analysis and monitoring in patients.
- Capnography is often defined as the measurement of the level of carbon dioxide (CO2) in exhaled and/or inhaled breath. Since infrared light was found to be absorbed particularly well by CO2, capnographs usually measure infrared absorption in the breath gasses, which indicates the level of CO2 in these gasses. Other measurement technologies exist as well.
- The information obtained from a capnographic measurement is sometimes presented as a series of waveforms, representing the partial pressure of CO2 in the patient's exhaled breath as a function of time.
- Clinicians commonly use capnography in order to assess a patient's ventilatory status. Respiratory arrest and shunt may be speedily diagnosed, and a whole range of other respiratory problems and conditions may be determined by the capnographic measurement. Capnography is considered to be a prerequisite for safe intubation and general anesthesia, as well as for correct ventilation management.
- Breath flow dynamics is another ventilation-related factor that is sometimes being measured. Whereas capnography is usually indicative of physiological aspects of ventilation, breath flow dynamics measurement is often indicative of the mechanics of respiration—the inhalation and exhalation activity of patient's lungs.
- There is provided, according to embodiment, a ventilation analysis system comprising: an interface module adapted to receive a carbon dioxide (CO2) signal and a breath flow dynamics signal; and control logic adapted to produce a ventilation indicator, based on a mutual analysis of said CO2 signal and said breath flow dynamics signal.
- There is further provided, according to an embodiment, a method for ventilation analysis, the method comprising: receiving a CO2 signal and a breath flow dynamics signal; and mutually analyzing the CO2 signal and the breath flow dynamics signal, to produce a ventilation indicator.
- In some embodiments, said ventilation indicator comprises an estimated CO2 waveform, an End-Tidal CO2 (EtCO2) value and/or a minute CO2 value.
- In some embodiments, the system further comprises a CO2 sensor adapted to produce said CO2 signal.
- In some embodiments, said CO2 sensor comprises a wireless CO2 sensor.
- In some embodiments, said CO2 sensor comprises a CO2 sensor having a response time of 100 milliseconds (ms) or more, 500 ms or more and/or 900 ms or more.
- In some embodiments, the system further comprises a breath flow dynamics sensor adapted to produce said breath flow dynamics signal.
- In some embodiments, said breath flow dynamics sensor comprises a wireless breath flow dynamics sensor.
- In some embodiments, said breath flow dynamics sensor comprises a flow sensor, an acoustic sensor, a thermal sensor, a chest movement detector, a computer-aided video analyzer and/or a Doppler radar.
- In some embodiments, said interface module is further adapted to receive a Saturation of Peripheral Oxygen (SpO2) signal.
- In some embodiments, the system further comprises an SpO2 sensor adapted to produce said SpO2 signal.
- In some embodiments, the receiving of the CO2 signal comprises wirelessly receiving the CO2 signal.
- In some embodiments, the CO2 signal comprises discrete Partial Pressure CO2 (PCO2) readings taken every 100 ms or more, every 500 ms or more and/or every 900 ms or more.
- In some embodiments, the receiving of the breath flow dynamics signal comprises wirelessly receiving the breath flow dynamics signal.
- In some embodiments, the breath flow dynamics signal comprises a flow measurement, an acoustic measurement, a thermal measurement, a chest movement measurement, a computer-aided video analysis and/or a Doppler radar signal.
- In some embodiments, the method further comprises receiving an SpO2 signal.
- In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed description.
- 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.
-
FIG. 1 schematically shows a block diagram of a ventilation analysis system; -
FIG. 2 schematically shows a graph of CO2 and breath flow dynamics signals; -
FIG. 3 schematically shows an estimated CO2 waveform; -
FIG. 4 schematically shows an adult normal capnogram; and -
FIGS. 5A-C schematically show capnogram patterns. - An aspect of some embodiments of the disclosure relates to a ventilation analysis and/or monitoring system. The system may be adapted to interface with one or more sensors to receive a carbon dioxide (CO2) signal and a breath flow dynamics (hereinafter “BFD”) signal, both pertaining to a patient. The received signals may be mutually analyzed, to produce a ventilation indicator that may assist a clinician in assessing the patient's ventilatory condition.
- Advantageously, the CO2 signal may be received from a CO2 sensor adapted to operate with a relatively slow response time. In some embodiments, this may enable the use of a relatively small, power efficient and/or simple sensor, compared to conventional CO2 sensors commonly used today in conjunction with capnographs. Various CO2 sensors are being constantly introduced to the market, where one of the major improvements these sensors offer is faster and faster response times. Response time is often defined as the duration between two consecutive samples taken by the CO2 sensor. For example, a sensor having a response time of 50 milliseconds (ms), is able to measure (or “read”) momentary breath CO2 concentration once every 50 ms, which amounts to 20 measurements per second. A faster response time means a shorter response time and therefore more measurements per second.
- Generally, faster response times enable the creation of a CO2 waveform (or “graph”) having a greater resolution. A CO2 waveform is a graphic representation of the breath CO2 concentration over time, which is sometimes displayed by capnographs. If more CO2 readings are available per a unit of time, the resolution of the waveform increases, and so does its accuracy and the amount of meaningful information it may relay to a clinician. Therefore, newly-introduced capnographs often aim to offer faster response times than before. However, there is often a tradeoff between response time and factors like manufacturing complexity, power consumption, physical size and weight, cost and/or the like.
- Therefore, in an embodiment, the ventilation analysis and/or monitoring system is advantageously adapted to provide a clinically-meaningful ventilation indication while utilizing a CO2 sensor having a relatively slow response time, such as a response time in the range of 100-300 ms, 300-500 ms, 500-700 ms, 700-900 ms, 900-1100 ms or above 1100 ms. This may enable the use of a relatively simple, small, low power, lightweight and/or otherwise more cost-effective CO2 sensor. In other embodiments, a CO2 sensor may nonetheless have a relatively fast response time, such as a response time of below 100 ms.
- The ventilation analysis and/or monitoring system may provide the ventilation indication by pairing a signal received from the CO2 sensor with a signal received from a BFD sensor. BFD, which is often indicative of the mechanics of respiration—the inhalation and exhalation activity of patient's lungs, may be measured using various methods known in the art. For example, a flow sensor is sometimes positioned about the patient's nostrils or mouth, directly measuring the dynamics of inward and/or outward gas flow. If the patient is intubated and given artificial respiration, a measurement of the BFD may be provided by the respirator.
- Measurement of BFD may also be performed essentially indirectly, such as using an acoustic sensor sensitive to sound emitted during respiration, a thermal sensor sensitive to temperature changes during respiration, a chest movement detector attached to the patient's body, a microwave Doppler radar system adapted to produce a signal indicative of chest movement and/or a computer-aided video analyzer adapted to visually recognize chest movement.
- BFD may provide information such as a numerical respiration rate value and/or a visual indication of exhalation/inhalation cycles over a time axis. A respiration rate is often defined as the number of exhalation/inhalation cycles per minute, and is commonly considered a clinical parameter of great importance. A visual indication may include a graph showing the exhalation/inhalation spread over a time axis.
- Reference is now made to
FIG. 1 , which shows a block diagram 100 of a ventilation analysis and/or monitoring system (hereinafter “system”) 102, in accordance with an embodiment.System 102 may be essentially what is often referred to as a capnograph, or be incorporated within a capnograph. -
System 102 may include aninterface module 104 adapted to interface with a CO2 sensor 110 and with aBFD sensor 112, which measure breath CO2 concentration and BFD, respectively, of a patient. The interface with each of CO2 sensor 110 andBFD sensor 112 may be wired or wireless. Optionally, CO2 sensor 110 andBFD sensor 112 are enclosed within a single physical unit, which may be referred to as a multi-purpose sensor adapted to sense both CO2 and BFD. -
Interface module 104 may further be adapted to interface with an SpO2 sensor (not shown), to receive an SpO2 signal. -
Interface module 104 may periodically receive a CO2 signal from CO2 sensor 110 and a BFD signal fromBFD sensor 112, and make these signals available to acontrol logic 106.Control logic 106 may mutually analyze the CO2 and BFD signals, and output (or “produce”) one or more ventilation indicator(s) 114 based on both signals. - An example of a ventilation indicator is a CO2 waveform 116. As mentioned, conventional capnographs may require a fast-response CO2 sensor in order to produce a CO2 waveform of a sufficiently high resolution. Nonetheless, CO2 waveform 116 may be produced based on the BFD signal and on the CO2 signal which may be of a slow-response CO2 sensor. The creation of CO2 waveform 116 is further discussed below.
- In addition to CO2 waveform 116, other ventilation indicator(s) 118 may be created from the mutual analysis of the BFD and CO2 signals. For example, a ventilation indicator may be end-tidal CO2 (EtCO2), minute EtCO2 and/or the like. These ventilation indicators are further discussed below.
-
System 102 may be further adapted to relay to a clinician, visually and/or sonically, SpO2 values derived from the received SpO2 signal. -
System 102 may be embodied in a computerized device having input, output and processing abilities to carry out operations ofinterface module 104 andcontrol logic 106. For example,system 102 may be an essentially stationary computerized device positioned next to a patient's hospital bed or at a central location in the hospital (if remote monitoring of a patient is desired). As another example,system 102 may be an essentially mobile computerized device adapted to be carried by an emergency clinician, in an ambulance and/or the like. A patient whose ventilatory condition is desired to be monitored may be connected to CO2 sensor 110 andBFD sensor 112, which transmit their readings tosystem 102 for analysis. The output ofsystem 102, namely—ventilation indicator 114, may be relayed to the clinician by way of visual display on a monitor, sonic indication and/or the like. - In an embodiment,
system 102, or another system (not shown) adapted to receive CO2 and BFD signals, may provide a ventilation indicator or different ventilatory status having enhanced reliability. The enhanced reliability may be achieved since CO2 and BFD are two measures of essentially the same system—the body ventilatory system. Each of these measures offers a different perspective of essentially the same bodily system, and therefore these measures complement each other. Monitoring both measures may allow the filtering out of issues such as false or poor readings arriving from one of the two sensors due to a defect or an error, and/or cases in which the patient is talking, eating, coughing and the like and therefore temporarily exhibiting irregular CO2 and/or BFD signals. - Reference is now made to
FIG. 2 , which shows agraph 200 of exemplary signals that may be transmitted from CO2 sensor 110 andBFD sensor 112 to interface module 104 (FIG. 1 ). - A
BFD signal 202 may indicate a respiratory state of the patient, such as whether the patient is currently exhaling or inhaling, and/or the intensity of the exhaling/inhaling at any particular moment. For example, aconcave shape 202 a ofBFD signal 202 may be indicative of inhalation, whereas aconvex shape 202 b of the BFD signal may be indicative of exhalation. - A partial pressure CO2 (PCO2) signal, shown as discrete PCO2 readings 204, may indicate one or more physiological aspects of ventilation. Horizontal distances between PCO2 readings 204 may be dictated by a response time of the sensor that performed the reading. Since PCO2 during inhalation is zero, zero
readings 204 a may be present during the inhalation.Other readings 204 b, usually higher than zero, may be present during exhalation. - A PCO2
average signal 206 may show an average of PCO2 over time. A CO2 sensor may average PCO2 readings it performs, producing PCO2average signal 206, by using a capacitor and/or similar electronic means. PCO2average signal 206 is shown in the figure as astraight line 206 a, for illustrative purposes only. - A CO2 sensor may transmit either PCO2 readings 204, PCO2
average signal 206, or both. - Reference is now made to
FIG. 3 , which shows an exemplary estimated CO2 waveform 300, which is optionally the ventilation indicator produced by the ventilation analysis and/or monitoring system. The exemplary estimated CO2 waveform 300, like common CO2 waveforms, may contain trapezoid-like shapes, such astrapezoid 302. Anupsurge curve 302 a oftrapezoid 302 indicates a beginning of an exhalation, a gradually risingcurve 302 b indicates a central part of the exhalation, and adrop curve 302 c indicates an ending of the exhalation. A zero-value curve 302 d indicates an inhalation. - Those of skill in the art will recognize that the shape of the trapezoids usually changes according to the medical condition of the patient, and that estimated CO2 waveform 300 is meant for illustrative purposes only.
- In an embodiment, estimated CO2 waveform 300 may be constructed by way of the mutual analysis of the CO2 and BFD signals, despite the slow response time of the CO2 sensor. For example, if PCO2 average signal 206 (
FIG. 1 ) is provided by the CO2 sensor, it may be possible to calculate what was the PCO2 during exhalation. For instance, if the average PCO2 is 20, and it is known that: (a) during inhalation the PCO2 is zero; and (b) the duty cycle of the exhalation and inhalation, as apparent from the BFD signal, is 50%—then the average PCO2 during exhalation is 40. A trapezoid, such astrapezoid 302, may then be constructed according to a mathematical constraint that the trapezoid's average value must be 40. Another mathematical factor that may be helpful in the construction of the trapezoid is that the product of the average PCO2 during exhalation (in our example, 40) and the duration of the exhalation (which may be inferred from the BFD signal) is equal to an area that should be delimited between the constructed trapezoid and the time axis. - The BFD signal may provide information pertaining to starting and ending points of the inhalations and exhalations, so that any constructed trapezoids, such as
trapezoid 302, may be synchronized with breath cycles. - If discrete PCO2 readings 204 (
FIG. 2 ) are provided by the CO2 sensor, a general shape of a trapezoid may be available throughother readings 204 b (FIG. 2 ). One or more methods may be employed in order to fill in the gaps betweenother readings 204 b and enhance the resolution of the trapezoid. For example,other readings 204 b (FIG. 2 ) may be averaged and then treated similarly to the average PCO2 described above. As another example,other readings 204 b (FIG. 2 ) may be synchronized with breath cycles provided by the BFD signal, so that a location and an estimated shape of parts likeupsurge curve 302 a, gradually risingcurve 302 b,drop curve 302 c and zero-value curve 302 d may be determined. - In an embodiment, the ventilation indicator is an EtCO2 value. EtCO2 is often defined as the partial pressure of CO2 at a point in time when CO2 values stop increasing and on the verge of dropping. An exemplary EtCO2 point 304 is shown in
FIG. 3 . - The creation of EtCO2 indication may be enabled, despite the slow response time of the CO2 sensor, via mathematical calculation. The EtCO2 may be calculated similar to the way the CO2 waveform may be created, as discussed above. If an estimated shape of a trapezoid is calculated, EtCO2 for each trapezoid may also be calculated.
- In an embodiment, the ventilation indicator is a minute CO2 value. Minute CO2 is commonly referred to as the total production of CO2 per minute. By correlating the BFD signal with the PCO2 average or discrete readings, minute CO2 may be calculated. More specifically, when using a PCO2 average signal, inhalation and exhalation cycles may be used to determine the PCO2 average during exhalation alone. This exhalation PCO2 may then be multiplied by a respiration rate (also obtainable from the BFD signal) to output minute CO2.
- Reference is now made to
FIG. 4 , which shows an adultnormal capnogram 400 as known in the art. Adultnormal capnogram 400 in spontaneously breathing subjects may be characterized by four distinct phases: -
- 1. Dead space ventilation: Shown between
points - 2. Ascending phase: Shown between
points - 3. Alveolar plateau: Shown between
points - 4. Inspiratory limb: Shown between
points
- 1. Dead space ventilation: Shown between
-
Point 408, which is the intersection of the alveolar plateau and the inspiratory limb, is often referred to as the End-Tidal CO2 (EtCO2). - An angle α, which designates the angle between the ascending phase curve and the X axis, is referred to as a “takeoff angle”. An angle β, which designates the angle between the alveolar plateau and the X axis, is referred to as an “elevation angle”.
- An amplitude of
capnogram 400 is dependent on EtCO2 concentration. A width ofcapnogram 400 is dependent on expiratory time. The shape ofcapnogram 400 is generally rectangular, formed by almost perpendicular ascending phase (indicating absence of lower airway obstruction) and inspiratory limb (no upper airway obstruction). - Reference is now made to
FIGS. 5A , 5B and 5C, which show exemplary capnogram patterns.FIG. 5A shows acapnogram 500 demonstrating elevated EtCO2 with a good alveolar plateau. Acorresponding graph 502 shows a 30-minute trend exhibiting a constant but elevated EtCO2. Possible causes may be: (a) inadequate minute ventilation or hypoventilation; (b) respiratory depressant drugs; (c) hyperthermia, pain and/or shivering. -
FIG. 5B shows acapnogram 504 demonstrating gradually increasing EtCO2. Acorresponding graph 506 shows a 30-minute trend exhibiting this gradual increase. Possible causes may be: (a) hypoventilation; (b) rising body temperature and/or malignant hyperthermia; (c) increased metabolism; (d) partial airway obstruction; (e) absorption of CO2 from exogenous source. -
FIG. 5C shows acapnogram 508 demonstrating an alveolar cleft. Acorresponding graph 510 shows a 30-minute trend exhibiting constant EtCO2 levels. Possible causes may be inadequate neuromuscular blockade and/or emergence from blockade. - While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced be interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.
- In the description and claims of the application, each of the words “comprise” “include” and “have”, and forms thereof, are not necessarily limited to members in a list with which the words may be associated.
Claims (8)
1. A low power, light weight medical device comprising:
a user interface comprising a CO2 sensor configured to measure a CO2 concentration in a subject's breath, said CO2 sensor having a response time below 100 ms;
a control logic configured to produce a ventilation indicator based on CO2 concentration measurements obtained from said CO2 sensor; and
a display configured to display said ventilation indicator and to provide a numerical respiration rate value and/or a visual indication of exhalation and/or inhalation cycles over a time axis.
2. The medical device of claim 1 , wherein said user interface further comprises a breath flow dynamics (BFD) sensor.
3. The medical device of claim 2 , wherein said ventilation indicator is further produced based on BFD measurements obtained from said BFD sensor.
4. The medical device of claim 2 , and wherein said BFD sensor is a flow sensor.
5. The medical device of claim 1 , further configured to provide a visual and/or sonic indication related to said ventilation indicator.
6. The medical device of claim 1 , wherein said ventilation indicator comprises an estimated CO2 waveform, an End-Tidal CO2 (EtCO2) value and/or a minute CO2 value.
7. The medical device of claim 6 , wherein said ventilation indicator comprises an estimated CO2 waveform and an End-Tidal CO2 (EtCO2) value.
8. The medical device of claim 1 , wherein said CO2 sensor has a response time below 50 ms.
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US14/619,976 US20150151072A1 (en) | 2008-06-30 | 2015-02-11 | Ventilation analysis and monitoring |
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US99911110A | 2010-12-15 | 2010-12-15 | |
US14/619,976 US20150151072A1 (en) | 2008-06-30 | 2015-02-11 | Ventilation analysis and monitoring |
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WO2011048536A1 (en) * | 2009-10-22 | 2011-04-28 | Koninklijke Philips Electronics N.V. | Method and apparatus for measuring the concentration of a gas in exhaled air |
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EP2303119A1 (en) | 2011-04-06 |
WO2010001390A1 (en) | 2010-01-07 |
EP2303119B1 (en) | 2018-08-01 |
US9987452B2 (en) | 2018-06-05 |
EP2303119A4 (en) | 2013-10-02 |
US20110105935A1 (en) | 2011-05-05 |
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