Journal of Applied Physiology, Vol 59, Issue 2 434-442, Copyright © 1985 by American Physiological Society
Effect of distortion on the mechanical properties of newborn piglet lung
K. J. Sullivan and J. P. Mortola
During breathing the relatively high chest wall-to-lung compliance ratio of
the newborn favors distortion of the respiratory system. In this study we
have examined the effect of lung deformation, generated by a hydrostatic
pleural surface pressure gradient, on the static (Cstat) and dynamic (Cdyn)
compliance of the isolated newborn piglet lung. Seven lungs from piglets
2-7 days old have been studied in a saline-filled plethysmograph. Static
pressure-volume (PV) curves were obtained by changing the volume a known
amount and measuring the corresponding changes in transpulmonary pressure.
Dynamic PV curves were obtained by ventilating the lung at a fixed pressure
and at 20 cycles/min. These experiments were repeated in an air
plethysmograph on the undeformed lung. Lung volume history was standardized
prior to each maneuver by three inflations to 20-25 cmH2O. Lung collapse
was avoided by applying an end-expiratory load equal to the transpulmonary
pressure at functional residual capacity. Cstat was not significantly
different between the deformed and undeformed lung (P greater than 0.05).
Cdyn was less than Cstat in both cases (P less than 0.025) and was reduced
further by deformation (P less than 0.05). We conclude that 1) peripheral
airway obstruction or the viscoelastic properties of the piglet lung, or
both, decrease Cdyn, and 2) deformation increases the external (PV)
respiratory work by further decreasing Cdyn.
