The clearance of mucus in the trachea during high frequency chest wall compression (HFCWC) was studied in nine anesthetized dogs. High frequency chest wall compression was applied by oscillating the pressure in a thoracic cuff such that it produced oscillatory tidal volumes of 25 to 100 cc at frequencies of 3 to 17 Hz. The tracheal mucus clearance rate (TMCR) was determined by direct observation of the rate of displacement of a charcoal particle spot by means of a fiberoptic bronchoscope. Baseline TMCR during spontaneous breathing averaged 8.2 +/- 5.6 mm/min in the 9 dogs. The TMCR during 2 min of HFCWC was increased at 5, 8, 11, 13, 15, and 17 Hz but not at 3 Hz. The enhancement of clearance was most pronounced in the range of 11 to 15 Hz, reaching a peak value of 340% of control at 13 Hz. These studies suggest that HFCWC might be of considerable potential benefit as a mode of chest physiotherapy.

A case is reported in which a young man undergoing exploratory thoracotomy following a gunshot wound had a cardiac arrest during reinflation of the collapsed lung. Systemic air embolism was suspected as the cause. Subsequent neurological examination and C.T. scan demonstrated a lesion ascribable to this. Discontinuation of nitrous oxide, aspiration of left heart chambers and a head-down position are recommended as immediate treatment if this diagnosis is made. In cases with piercing lung trauma high inflation pressures should be avoided to prevent embolism.

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