Evaluation of estimates of alveolar gas exchange by using a tidally ventilated nonhomogenous lung model

• Published in: Journal of applied physiology (1985) Vol. 82; no. 6; pp. 1963 - 1971
• Main Authors: Busso, Thierry, Robbins, Peter A.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Physiological Society 01.06.1997
• Subjects: Algorithms; Biological and medical sciences; Blood gas. Hemoglobin. Myoglobin. Hemotissulary gas exchange. Acid-base balance; Capillaries; Computer Simulation; Fundamental and applied biological sciences. Psychology; Humans; Lung - physiology; Models, Biological; Pulmonary Alveoli - physiology; Pulmonary Circulation; Pulmonary Gas Exchange; Respiration; Tidal Volume; Vertebrates: respiratory system; Human; Ventilation perfusion relationship; Pulmonary alveolus; Tidal volume; Gas exchange; Pulmonary ventilation; Respiration; Mathematical model; Respiratory system
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1997.82.6.1963

Busso, Thierry, and Peter A. Robbins. Evaluation of estimates of alveolar gas exchange by using a tidally ventilated nonhomogenous lung model. J. Appl. Physiol. 82(6): 1963–1971, 1997.—The purpose of this study was to evaluate algorithms for estimating O 2 and CO 2 transfer at the pulmonary capillaries by use of a nine-compartment tidally ventilated lung model that incorporated inhomogeneities in ventilation-to-volume and ventilation-to-perfusion ratios. Breath-to-breath O 2 and CO 2 exchange at the capillary level and at the mouth were simulated by using realistic cyclical breathing patterns to drive the model, derived from 40-min recordings in six resting subjects. The SD of the breath-by-breath gas exchange at the mouth around the value at the pulmonary capillaries was 59.7 ± 25.5% for O 2 and 22.3 ± 10.4% for CO 2 . Algorithms including corrections for changes in alveolar volume and for changes in alveolar gas composition improved the estimates of pulmonary exchange, reducing the SD to 20.8 ± 10.4% for O 2 and 15.2 ± 5.8% for CO 2 . The remaining imprecision of the estimates arose almost entirely from using end-tidal measurements to estimate the breath-to-breath changes in end-expiratory alveolar gas concentration. The results led us to suggest an alternative method that does not use changes in end-tidal partial pressures as explicit estimates of the changes in alveolar gas concentration. The proposed method yielded significant improvements in estimation for the model data of this study.