Pulmonary Function Testing in Infants and Children

摘要

This research addressed the application of forced mechanical oscillations of the respiratory system to non-invasive testing of pulmonary function in uncooperative patients. The major results of these studies fall within three categories. First, frequency domain responses of the respiratory system (DC-10 kHz) were models using a distributed parameter model of the complete tracheo-bronchial tree. This model revealed the relationship between lung structure and many of the measurable response parameters. Second, the time domain impulse reflection response of the respiratory system was investigated theoretically and experimentally. In a result of particular importance, the authors showed that the cross-sectional area of the upper and central airways (as a function of distance along the airway) could be inferred from acoustic reflections measured at the mouth. Accuracy of the inferences required high bandwidths (10 kHz) and breathing of light gas mixtures. Airway area by acoustic reflections measured at the mouth provides a rapid non-invasive estimate of central airway structure with minimal patient contact time and minimal cooperation. Thirdly, the effects of forced oscillations upon gas exchange in the lung were studied. A result of particular relevance to infant care is that augmented diffusion promoted by high frequency oscillations (approximately 15 Hz) can support gas exchange even when tidal volumes fall well below dead space volume.