REFLEX BRONCHODILATION PRODUCED BY PHASIC VENTILATION OF THE LUNGS

The primary purpose of this work was to demonstrate whether oscillation of tracheal pressure in the range of normal breathing frequencies is more effective than static lung inflation in producing reflex bronchodilation. Secondarily, studies were conducted to determine a single factor that would integrate the reflex bronchodilator effects of frequency and tidal volume. Dogs were anesthetized and placed on cardiopulmonary bypass. After tracheal tone had been reflexly enhanced by chemoreceptor stimulation, oscillatory patterns of ventilation were produced around static pressure lung inflations of approximately 5.0 mmHg. The reflex bronchodilation produced by oscillation of lung volume was compared with that produced by static pressure lung inflation. Reflex bronchodilation produced by oscillation of lung volume was greater than that produced by static pressure inflation of the lungs and was strongly related to the maximum first time derivative of pressure (dP/dt, mmHg/s) observed, irrespective of whether the changes in the maximum dP/dt were produced by changes in the frequency or amplitude of the oscillations of tracheal pressure.