Factors that might be expected to influence the relation between compliance or pulmonary resistance and respiratory frequency were examined in normal subjects and patients with chronic obstructive pulmonary disease. Recent investigations, have, in fact, suggested that the pattern displayed by the mechanical properties of the lung in function of respiratory frequency may be influenced by factors that lie outside the time constant mechanism. Increased RL and decreased C dyn may be brought about by dynamic compression of the airways (due to forced respiration) and/or bronchoconstriction (due to hypocapnia). A standard technique was used. Resistance and compliance were determined as soon as the subject began to breathe at a certain rate. Each measurement involved a small number of breaths and was followed by a suitable period of spontaneous respiration. An appreciable fall in expiratory CO2 pressure was usually noted at more than 40 breaths/min. To assess the effect of such changes, RL and Cdyn at faster rates were measured: a) in accordance with the standard technique and as while the subject inhaled a mixture of air and CO2 to prevent hypocapnia. No significant differences were noted at the same rates. In some patients, there was a marked increase in resistance at fast rates even in b). The increase in RL, however, was associated with a disproportionate rise in maximum expiratory oesophageal pressure. By contrast, no relation could be detected between Cdyn in function of respiratory frequency and this pressure change. Orciprenaline or atropine led to no constant change in the ratio between Cdyn or RL and respiratory frequency. It would appear, therefore, that hypocapnia has no appreciable effect on the determination of Cdyn and RL at the respiratory frequency examined in the experiment. The data for RL, respiratory frequency, and maximum expiratory oesophageal pressure suggest that study of the mechanical behaviour of the lung in function of respiratory frequency is influenced by dynamic factors capable of producing compression of the airways.
|Translated title of the contribution||Analysis of factors capable of influencing the relation between dynamic compliance, pulmonary resistance and respiratory frequency in normal subjects and in patients with chronic obstructive pulmonary disease|
|Number of pages||12|
|Publication status||Published - 1978|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine