Pendelluft is not the major contributor to respiratory insufficiency in dogs with flail chest: a mathematical analysis

Abstract

"Pendelluft", or out-of-phase movement of the airway gas between the intact and flait-chest-side lungs has long been believed to be the major contributor to respiratory dysfunction in patients with flail chest. However, conflicting findings have also been reported mainly from animal studies. The aim of this study was to provide a mathematical projection on this classical problem. We measured respiratory impedance (ZRS) of dogs with flail chest using a pseudorandom forced oscillation method. A mathematical model implementing flail chest was fitted toZRS. The fitted results were used in simulating the mechanical behavior of a respiratory system with flail chest during spontaneous breathing. Our results suggest that the paradoxical movement of breathing between the flail segment and the intact chest wall does not create substantial pendelluft and that alveolar hypoventilation is created by the wasting movement of the flail segment which interferes with effective thoracic expansion.

Pendelluft in the bronchial tree

“…However, comparison with experimental data focusing on the larger airways and proximal bifurcations is possible. Shinozuka et al (16) measured pendelluft at the carina in an animal model of flail chest. They measured the magnitude of pendelluft volume transferred between the two lungs to be Ͻ2% of the tidal volume.…”

“…Clinically, pendelluft can be observed during mechanical ventilation of patients with unilateral chest or lung injury, where the two lungs can sometimes be seen inflating and deflating out of phase with each other (6,16). More subtle pendelluft is sometimes observed as a gradual drop in pressure during an end-inspiratory pause, which may be caused by airflow between the different regions of the lungs.…”