# US 12,594,389 B2 · Non-invasive estimation of hemodynamic parameters during mechanical ventilation

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- Number: US 12,594,389 B2
- Document ID: US12594389B2
- Status: Granted
- Kind: B2
- Application number: 17/250,277
- Filed: 2019-06-25
- Published: 2021-08-26
- Granted: 2026-04-07
- Earliest claimed: 2018-07-06
- Assignees: Maquet Critical Care AB
- Applicants: Maquet Critical Care AB
- Inventors: Carl-Erik Troili; Tomas Westerlund
- Web page: https://patentgrep.com/patent/US12594389B2

## CPC

- A61M 16/0003: {Accessories therefor, e.g. sensors, vibrators, negative pressure}
- A61B 5/02007: {Evaluating blood vessel condition, e.g. elasticity, compliance}
- A61B 5/02028: {Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction}
- A61B 5/0205: Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
- A61B 5/02125: {of pulse wave propagation time}
- A61B 5/087: Measuring breath flow
- A61M 16/022: {Control means therefor}
- A61M 2016/0027: {pressure meter}
- A61M 2016/003: {with a flowmeter}
- A61M 2230/30: Blood pressure (A61M2230/04 takes precedence)
- A61M 2230/40: Respiratory characteristics
- A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

The present disclosure relates to a method for non-invasive determination of a hemodynamic parameter of a mechanically ventilated subject (3) based on a point in time (thb) of a heartbeat of the subject and an arrival point in time (tarr_pulm, tarr_sys) at which a blood pressure pulse caused by the heartbeat reaches a point of arrival in the circulatory system of the subject. The method comprises the steps of measuring (S41) a respiratory pressure and/or a respiratory flow, and determining (S43) the point in time (thb) of the heartbeat from a change in the measured respiratory pressure and/or the respiratory flow resulting from a physical impact of the heart on the lungs of the subject (3) during the heartbeat.

## Claims

### Claim 1

A method for non-invasive determination of a hemodynamic parameter of a subject mechanically ventilated via a breathing apparatus based on a point in time (thb) of a heartbeat of the subject and an arrival point in time (tarr_pulm, tarr_sys) at which a blood pressure pulse caused by the heartbeat reaches a point of arrival in a circulatory system of the subject, comprising:
obtaining a respiratory pressure and/or a respiratory flow via one of a pressure sensor and a flow sensor, respectively;
estimating a time window for a heartbeat based on data obtained from a blood oxygen sensor;
determining, within the time window, the point in time (thb) of the heartbeat from a change in the measured respiratory pressure and/or the respiratory flow resulting from a physical impact of the heart on the lungs of the subject during the heartbeat;
determining, via a controller of the breathing apparatus:
a pulmonary pulse transit time, PTTpulm, for the blood pressure pulse based on the point in time of the heartbeat (thb) and a point in time of arrival (tarr_pulm) of the blood pressure pulse to the lungs of the subject; and/or
a systemic pulse transit time, PTTsys, for the blood pressure pulse based on the point in time of the heartbeat (thb) and a point in time of arrival (tarr_sys) of the blood pressure pulse to a point of arrival in the systemic circulatory system of the subject; and
determining, via the controller, the hemodynamic parameter based on PTTpulm and/or PTTsys.

### Claim 2 (depends on 1)

The method of claim 1, wherein the point in time of the heartbeat (thb) is determined from a change in magnitude of the measured respiratory pressure and/or the respiratory flow.

### Claim 3 (depends on 1)

The method of claim 1, wherein the point in time of the heartbeat (thb) is determined from a change in a first and/or second order derivative with respect to time of the measured respiratory pressure and/or the measured respiratory flow.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
estimating a time window (ΔThb(P)) for the heartbeat based on at least one parameter indicative of an approximate point in time of the heartbeat, and
determining the point in time of the heartbeat (thb) based on the respiratory pressure and/or respiratory flow measured during the estimated time window.

### Claim 5 (depends on 4)

The method of claim 4, wherein the time window (ΔThb(P)) is estimated based on any of, or any combination of:
blood oxygenation data relating to oxygenation of blood in a body part at a known or assumable distance from the heart of the subject;
systemic blood pressure data relating to a systemic blood pressure measured in a body part at a known or assumable distance from the heart of the subject;
the determined arrival point in time (tarr_pulm, tarr_sys) of the blood pressure pulse to the lungs of the subject;
the point(s) in time of one or more previous heartbeats, and
the point(s) in time of arrival at the lungs of the subject of one or more previous blood pressure pulses generated by the one or more previous heartbeats.

### Claim 6 (depends on 1)

The method of claim 1, further comprising:
determining the arrival point in time (tarr_pulm, tarr_sys) as a point in time of arrival (tarr_pulm) of the blood pressure pulse to the lungs of the subject from a change in the measured respiratory pressure and/or the respiratory flow resulting from a change in lung volume caused by the arrival of the blood pressure pulse to the lungs of the subject.

### Claim 7 (depends on 6)

The method of claim 6, further comprising:
estimating a time window for the arrival of the blood pressure pulse to the lungs of the subject based on at least one parameter indicative of an approximate point in time of arrival of the blood pressure pulse to the lungs of the subject, and
determining the point in time of arrival (tarr_pulm) based on the respiratory pressure and/or respiratory flow measured during the estimated time window.

### Claim 8 (depends on 6)

The method of claim 6, wherein the time window is estimated based on any of, or any combination of:
the point in time (thb) of the heartbeat;
the point(s) in time of one or more previous heartbeats; and
the point(s) in time of arrival at the lungs of the subject of one or more previous blood pressure pulses generated by the one or more previous heartbeats.

### Claim 9 (depends on 1)

The method of claim 1, further comprising:
determining a pulmonary blood pressure, PBP, of the subject or a pulmonary cardiac output, PCO, of the subject as the hemodynamic parameter, based on PTTpulm.

### Claim 10 (depends on 1)

The method of claim 1, further comprising:
measuring a blood oxygenation at a point of blood oxygenation measurement in the systemic circulatory system of the subject; and
determining the point in time of arrival (tarr_sys) of the blood pressure pulse to a point of arrival in the systemic circulatory system as a point in time of arrival of the blood pressure pulse to the point of blood oxygenation measurement, based on a change in the measured blood oxygenation.

### Claim 11 (depends on 1)

The method of claim 1, further comprising:
determining a systemic blood pressure, SBP, of the subject or a systemic cardiac output, SCO, of the subject as the hemodynamic parameter, based on PTTsys.

### Claim 12 (depends on 1)

The method of claim 1, further comprising:
determining a cardiac shunt of the ventilated subject based on a relationship between a system cardiac output, SCO, and a pulmonary cardiac output, PCT, of the subject, wherein PCO is determined based on PTTpulm and/or SCO is determined based on PTTsys.

### Claim 13 (depends on 1)

A computer program product for non-invasive determination of a hemodynamic parameter of a subject mechanically ventilated via a breathing apparatus based on a point in time (thb) of a heartbeat of the subject and an arrival point in time (tarr_pulm, tarr_sys) at which a blood pressure pulse caused by the heartbeat reaches a point of arrival in a circulatory system of the subject, the computer program product comprising a non-transitory computer-readable data storage medium storing instructions which, when executed by a computer, causes the computer to perform the steps of claim 1.

### Claim 14

A ventilation system for non-invasive determination of a hemodynamic parameter of a mechanically ventilated subject based on a point in time (thb) of a heartbeat of the subject and an arrival point in time (tarr_pulm, tarr_sys) at which a blood pressure pulse caused by the heartbeat reaches a point of arrival in a circulatory system of the subject, the ventilation system comprising:
a breathing apparatus mechanically ventilating the subject;
at least one pressure sensor measuring a respiratory pressure and/or at least one flow sensor measuring a respiratory flow;
a blood oxygen sensor; and
a computer determining the hemodynamic parameter,
wherein the computer is configured to:
estimate a time window for a heartbeat based on data obtained from the blood oxygen sensor;
determine, within the time window, the point in time (thb) of the heartbeat from a change in the measured respiratory pressure and/or the respiratory flow resulting from a physical impact of the heart on the lungs of the subject during the heartbeat;
determine:
a pulmonary pulse transit time, PTTpulm, for the blood pressure pulse based on the point in time of the heartbeat (thb) and a point in time of arrival (tarr_pulm) of the blood pressure pulse to the lungs of the subject; and/or
a systemic pulse transit time, PTTsys, for the blood pressure pulse based on the point in time of the heartbeat (thb) and a point in time of arrival (tarr_sys) of the blood pressure pulse to a point of arrival in the systemic circulatory system of the subject; and
determine the hemodynamic parameter based on PTTpulm and/or PTTsys.

### Claim 15 (depends on 14)

The ventilation system of claim 14, wherein the computer is configured to determine the point in time of the heartbeat (thb) from a change in magnitude of the measured respiratory pressure and/or the respiratory flow.

### Claim 16 (depends on 14)

The ventilation system of claim 14, wherein the computer is configured to determine the point in time of the heartbeat (thb) from a change in a first and/or second order derivative with respect to time of the measured respiratory pressure and/or the measured respiratory flow.

### Claim 17 (depends on 14)

The ventilation system of claim 14, wherein the computer is configured to estimate a time window (ΔThb(P)) for the heartbeat based on at least one parameter indicative of an approximate point in time of the heartbeat, and determining the point in time of the heartbeat (thb) based on the respiratory pressure and/or respiratory flow measured during the estimated time window.

### Claim 18 (depends on 17)

The ventilation system of claim 17, wherein the computer is configured to estimate the time window (ΔThb(P)) based on any of, or any combination of:
blood oxygenation data relating to oxygenation of blood in a body part at a known or assumable distance from the heart of the subject;
systemic blood pressure data relating to a systemic blood pressure measured in a body part at a known or assumable distance from the heart of the subject;
the determined arrival point in time (tarr_pulm, tarr_sys) of the blood pressure pulse to the lungs of the subject;
the point(s) in time of one or more previous heartbeats, and
the point(s) in time of arrival at the lungs of the subject of one or more previous blood pressure pulses generated by the one or more previous heartbeats.

### Claim 19 (depends on 14)

The ventilation system of claim 14, wherein the computer is configured to determine the arrival point in time (tarr_pulm, tarr_sys) as a point in time of arrival (tarr_pulm) of the blood pressure pulse to the lungs of the subject from a change in the measured respiratory pressure and/or the respiratory flow resulting from a change in lung volume caused by the arrival of the blood pressure pulse to the lungs of the subject.

### Claim 20 (depends on 19)

The ventilation system of claim 19, wherein the computer is configured to estimate a time window for the arrival of the blood pressure pulse to the lungs of the subject based on at least one parameter indicative of an approximate point in time of arrival of the blood pressure pulse to the lungs of the subject, and determining the point in time of arrival (tarr_pulm) based on the respiratory pressure and/or respiratory flow measured during the estimated time window.

### Claim 21 (depends on 20)

The ventilation system of claim 20, wherein the computer is configured to estimate the time window based on any of, or any combination of:
the point in time (thb) of the heartbeat;
the point(s) in time of one or more previous heartbeats; and
the point(s) in time of arrival at the lungs of the subject of one or more previous blood pressure pulses generated by the one or more previous heartbeats.

### Claim 22 (depends on 14)

The ventilation system of claim 14, wherein the computer is configured to determine a pulmonary blood pressure, PBP, of the subject or a pulmonary cardiac output, PCO, of the subject as the hemodynamic parameter, based on PTTpulm.

### Claim 23 (depends on 14)

The ventilation system of claim 14, wherein the computer is configured to:
obtain blood oxygenation measurements obtained at a point of blood oxygenation measurement in the systemic circulatory system of the subject, and
determine the point in time of arrival (tarr_sys) of the blood pressure pulse to a point of arrival in the systemic circulatory system as a point in time of arrival of the blood pressure pulse to the point of blood oxygenation measurement, based on a change in the measured blood oxygenation.

### Claim 24 (depends on 14)

The ventilation system of claim 14, wherein the computer is configured to determine a systemic blood pressure, SBP, of the subject or a systemic cardiac output, SCO, of the subject as the hemodynamic parameter, based on PTTsys.

### Claim 25 (depends on 14)

The ventilation system of claim 14, wherein the computer is configured to determine a cardiac shunt of the mechanically ventilated subject based a relationship between a systemic cardiac output, SCO, and a pulmonary cardiac output, PCO, of the subject, wherein the computer is configured to determine PCO based on PTTpulm and/or to determine SCO based on PTTsys.