Journal of Applied Physiology, Vol 67, Issue 2 614-619, Copyright © 1989 by American Physiological Society
Removal of excessive bronchial secretions by asymmetric high-frequency oscillations
L. Freitag, W. M. Long, C. S. Kim and A. Wanner
Pulmonary Division, University of Miami, Mount Sinai Medical Center, Florida 33140.
The present study evaluated whether high-frequency oscillations (HFO) with
biased flow profiles applied at the airway opening are capable of altering
mucus clearance. In eight anesthetized sheep, artificial mucus (100 P) was
infused continuously (1 ml/min) into the left main bronchus via a cannula
inserted through the dorsal wall of the left main bronchus after
thoracotomy. Outcoming mucus was collected every 10 min from the end of a
cuffed orotracheal tube. Animals were ventilated with a Harvard respirator
at a low frequency with superimposed HFO at 14 Hz with asymmetrical
waveforms generated by a digitally controlled electromagnetic piston pump
(expiratory bias: peak expiratory flow 3.8 l/s, peak inspiratory flow 1.3
l/s; inspiratory bias: reverse of expiratory bias). The influence of
posture and of HFO airflow bias on mucus clearance was determined. In the
horizontal position, mucus clearance with expiratory biased HFO was 3.5 +/-
2 (SD) ml/10 min. Head-down tilt produced a clearance of 3.1 +/- 3 ml/10
min; addition of HFO with expiratory bias increased clearance to 11.0 +/-
2.0 ml/10 min (P less than 0.05). No clearance occurred with inspiratory
biased HFO during head-down tilt. These results indicate that expiratory
biased HFO at the airway opening can clear excessive airway secretions and
augment clearance by postural drainage.
