TRACHEAL MUCUS CLEARANCE IN HIGH-FREQUENCY OSCILLATION .2. CHEST WALL VERSUS MOUTH OSCILLATION

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Abstract
Tracheal mucus clearance rate (TMCR) in anesthetized dogs was compared during spontaneous breathing (SB), ventilation by high-frequency oscillation at the airway opening (HFO/AO) and ventilation by high-frequency oscillation of the chest wall (HFO/CW). The HFO/AO was carried out by using a piston pump with a high impedance transverse flow at the endotracheal tube proximal end; HFO/CW was effected by creating rapid pressure oscillations in an air filled cuff warapped around the lower thorax of the animal, causing small tidal volumes at the mouth. The TMCR was measured by observing the displacement rate of a charcoal marker in the lower trachea; a fiberoptic bronchoscope was used to deposit the marker before each experiment and to relocate it after a 5 min run. In 7 dogs, mean TMCR during control (SB) was 8.9 .+-. 3.5 mm/min. At 13 Hz with an oscillatory tidal volume (VTO) of 1.5 mg/kg, mean TMCR was 240% of control with HFO/CW (P < 0.001) and 76% of control with HFO/AO (NS). During HFO/AO at 20 Hz and a 3 ml/kg VTO, mean TMCR was 97% of control. High-frequency ventilation by rapid chest wall compression enhances tracheal mucus clearance when compared with spontaneous breathing, whereas high-frequency oscillation at the mouth does not.

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