Pneumatic chest wall compression. A cause of respiratory failure from massive subcutaneous emphysema. Subcutaneous emphysema rarely causes significant adverse clinical consequences. Two patients had development of massive subcutaneous emphysema during positive-pressure ventilation that resulted in chest wall compression and respiratory failure. Drainage of the subcutaneous air produced dramatic improvement. Subcutaneous emphysema is potentially fatal in ventilated patients. Specific decompression of subcutaneous tissues is indicated in such extreme cases. 