Contribution to the study of chest and lung mechanics in artificially ventilated normal man during surgery

Firstly the authors describe the principle and the technical application of an original method of measurement of the mechanical ventilatory parameters. Then the method is illustrated with measurements of the pulmonary thoracic and thoraco-pulmonary mechanical parameters in 20 healthy subjects under going extra-thoracic surgery. The results show the lack of correlation between the value of the pulmonary mechanical parameters measured in the awake supine subjects breathing spontaneously and in the anesthetized supine subjects artificially ventilated. The decrease in chest wall elastance could explain the drop in ventilatory level and the unpredictable modifications in pulmonary mechanical parameters. Therefore it is impossible to establish meaningful reference values in healthy subjects undergoing artificial ventilation.