Lung Function Quantification via Gas Washout Modeling
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Solution Overview
Problem
Current pulmonary function tests, such as FEV1, are insensitive to early airway disease and fail to account for the heterogeneity of lung function in chronic obstructive pulmonary disease (COPD), requiring large patient cohorts and high cooperation for effective treatment assessment.
Innovation Solution
A method and apparatus that quantify lung function by analyzing respiratory gas patterns across multiple breaths using a parameterized lung model, incorporating alveolar compartments and personal deadspaces, with high temporal resolution gas measurements to fit a mathematical model that provides sensitive and discriminatory lung function measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If forced expiratory volume (FEV1) measurement is used, then the test is inexpensive and simple to measure, but it is extremely insensitive to early airway disease and fails to detect early disease stages
Solution Approach 1:
The lung is segmented into multiple compartments (e.g., fast and slow compartments) based on gas exchange characteristics. This segmentation allows the measurement to capture heterogeneity in lung function that FEV1 misses, thereby improving sensitivity to early disease while maintaining practical measurability through compartmental analysis of gas concentrations.
Solution Approach 2:
The invention changes the measured parameter from simple volume (FEV1) to gas concentration dynamics (e.g., nitrogen, helium, or other inert gases) during breath-hold or washout maneuvers. This parameter change enables detection of subtle functional differences between lung compartments, dramatically improving sensitivity to early airway disease while preserving ease of measurement through non-invasive gas analysis.
2Measurement precision
If large numbers of patients are recruited for Phase II clinical trials to compensate for FEV1 insensitivity, then statistical power is improved, but patient recruitment cost and time increase significantly
Solution Approach 1:
The invention replaces the mechanical/physiological measurement system (FEV1 spirometry) with a gas exchange measurement system that is inherently more sensitive. This substitution provides superior detection capability without requiring increased sample sizes, thereby improving clinical trial efficiency and reducing patient recruitment requirements while maintaining or enhancing statistical power.
3Loss of time
If standard lung function tests are used, then the testing procedure is simple and quick, but they provide limited information about lung heterogeneity and ventilation distribution
Solution Approach 1:
The invention maintains continuous measurement of gas concentrations throughout the breath-hold or washout maneuver, rather than taking single-point measurements. This continuous monitoring captures the dynamic behavior of gas exchange across different lung compartments, providing comprehensive information about ventilation distribution and heterogeneity within a brief testing window, thus preserving speed while dramatically increasing information content.
Data Source
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AI summary
A method and apparatus for non-invasive assessment of lung inhomogeneity by accurate high temporal resolution measurement of respiratory gas flows at the mouth during steady state breathing and inert gas wash-in or wash-out and using these measurements to fit a mathematical model of the inhomogeneous lung. The model of the lung is based on modelling the lung as plural alveolar compartments each having an identical volume at functional residual capacity, but varying in its fractional share of total lung compliance, total pulmonary vascular conductance and total anatomical deadspace. A bivariate log- normal distribution of the lung compliance and pulmonary vascular conductance is used, together with a normal distribution of deadspace fraction. The model is fitted to the measurements using non-linear regression and the distribution of ventilation: perfusion ratios, lung compliance: volume ratios, lung vascular conductance: volume ratios and lung deadspace: volume ratios obtained from the fitted model are indicative of the airway condition and thus lung function of the subject.