Mechanical Ventilation Cardiac Output Measurement With Pulse Pressure
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Solution Overview
Problem
Existing methods for determining cardiac output and effective pulmonary blood flow in mechanically ventilated patients are inaccurate due to the assumption of constant perfusion during breath sequences, which is often incorrect, leading to errors in CO2 level measurements and subsequent calculations.
Innovation Solution
A method that measures relative variations in cardiac output or effective pulmonary blood flow by incorporating uncalibrated pulse pressure signals into Fick-based techniques, compensating for changes in perfusion by using uncalibrated pulse pressure data to adjust cardiac output or EPBF determinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential Fick techniques are used to determine cardiac output or EPBF from changes in CO2 elimination and partial pressure of CO2, then cardiac output or EPBF can be estimated from measurable changes in ventilation, but the assumption of constant perfusion during the analysed sequence of breaths introduces substantial error in the determination
Solution Approach 1:
The patent incorporates pulse pressure measurements as a feedback mechanism to detect and compensate for perfusion variations during the breath sequence. By continuously monitoring pulse pressure and using it to adjust the cardiac output or EPBF calculation, the system accounts for changes in thoracic pressure and perfusion that occur during prolonged expiration phases, thereby resolving the contradiction between using differential Fick techniques and maintaining the constant perfusion assumption
Solution Approach 2:
The patent introduces pulse pressure as an intermediary parameter that mediates between the ventilation changes and the cardiac output/EPBF determination. The pulse pressure signal serves as an indicator of perfusion status, allowing the system to weight or adjust the Fick-based calculations based on actual perfusion conditions, thus bridging the gap between the theoretical constant perfusion assumption and the actual varying perfusion reality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves the accuracy of cardiac output and EPBF measurements by accounting for variations during breath sequences, reducing the need for complex calibration techniques and equipment, and providing real-time monitoring capabilities.
Implementation Method 1
measuring also a relative variation in cardiac output or effective pulmonary blood flow during the sequence of analysed breaths
Implementation Method 2
Most non-invasive respiratory based methods for determination of cardiac output or EPBF are based on some form of the basic physiological principle known as the Fick principle. According to the Fick equation, the cardiac output of a patient may be determined using the following basic relationship: Q = VCO2 / (CvCO2 - CaCO2)
Data Source
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AI summary
The present disclosure relates to a method for determination of cardiac output or EPBF of a mechanically ventilated subject (3). The method comprises the steps of introducing (S2) a change in the effective ventilation of the subject (3), measuring (S1) expiratory flow and CO2 during a sequence of analysed breaths during which the effective ventilation of the subject (3) varies, and determining (S3) the cardiac output or EPBF of the subject (3) using the flow and CO2 measurements. The method further comprises the steps of measuring (S1) also a relative variation in cardiac output or EPBF during the sequence of analysed breaths, and using the relative variation in the determination (S3) of cardiac output or EPBF.