Facilitation of intrathoracic operations by means of high-frequency ventilation

Gas exchange was measured in eight patients undergoing high-frequency ventilation (HFV) during intrathoracic operations for lung cancer. HFV facilitated the operation because the exposed lung moved only slightly to ventilate and stayed in a less expanded state. Intermittent positive-pressure breathing (IPPB) (control) was switched to HFV 20 minutes after the pleural cavity was opened. HFV either was conducted alone (HFV alone) or was superimposed on a hypoventilation equal to the dead space (HFV on VD). The driving pressure and frequency of HFV were set at 0.5 kg/cm2 using 3, 6, and 12 Hz with an FI02 of 0.50. The only statistically significant difference in arterial PO2 between IPPB and HFV occurred when the HFV alone was used at 12 Hz. Significant differences in arterial PCO2 values existed between IPPB and HFV alone when the HFV was at 6 and 12 Hz, and between HFV alone and HFV on VD at 12 Hz. The arterial pH values were lower at 6 and 12 Hz in HFV alone and were significantly different from pH values during IPPB. Acidosis was due to the respiratory component of HFV only. The metabolic component remained unchanged. It was concluded that the gas exchange was adequately maintained at 3 Hz during HFV alone. The intrathoracic operation was facilitated by less movement as the frequency increased, although the lung volume tended to expand. The gas exchange, particularly the elimination of carbon dioxide, worsened during the use of HFV alone. However, HFV on VD continued to maintain an adequate gas exchange and facilitate the operation.