Influence of panting frequency on plethysmographic measurements of thoracic gas volume

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Abstract
Using an integrated flow pressure-corrected body plethysmograph, total lung capacities (TLC) derived from thoracic gas volumes measured at low, medium and high panting frequencies were obtained in 10 healthy men and in 13 patients with chronic airflow obstruction before and after an aerosol of albuterol. Using a gastric balloon, gastric-to-mouth pressure ratios (.DELTA.Pga/.DELTA.Pm) were also assessed. In patients before albuterol, estimated TLC remained unchanged from low to medium and increased (not significantly) from medium to high frequency. Healthy subjects and patients after albuterol showed a significant decrease in TLC from low to medium panting frequencies, which persisted after correcting the data for abdominal gas compression using observed .DELTA.Pga/.DELTA.Pm. In patients after albuterol the results may be explained, at least in part, by intrathoracic airway compliance and mechanical inhomogeneity of the lung. In healthy subjects a remote possibility is the association of mechanical inhomogeneity and nonuniform pleural pressure.