Vagal stimulation and aerosol histamine increase hysteresis of lung recoil

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Abstract
Bronchoconstriction changes pulmonary resistance and dynamic compliance by altering airway properties and dynamic lung tissue recoil. To assess the contribution of recoil transpulmonary pressure was measured in anesthetized open-chest dogs during sinusoidal ventilation with gas flow and during sinusoidal compression of intrapulmonary gas without flow. Measurements with gas flow characterized total pulmonary behavior, including the contribution of gas flow in airways; whereas measurements during gas compression characterized lung tissue recoil alone. Histamine aerosol produced a 54% decrease in dynamic compliance, a 465% increase in total pulmonary resistance and a 153% increase in pressure-volume hysteresis of dynamic recoil. Vagal stimulation produced a 31% decrease in dynamic compliance, a 135% increase in total pulmonary resistance, an 82% increase in the hysteresis of recoil and a 15% increase in mean recoil pressure. At slow oscillation frequencies (0.2 Hz) and high transpulmonary pressures (10 cm H2O), hysteresis of lung recoil contributes substantially to total pulmonary resistance and changes in dynamic lung recoil can account for much (35%) of the increase in pulmonary resistance seen with bronchoconstriction.