Lung degassing: an evaluation of two methods.

This study compares the effectiveness of the oxygen absorption and vacuum degassing methods for removing trapped gas from lungs. In addition, the effects of changing vacuum pressure, number of times to degas, and lung orientation during the vacuum degassing procedure were evaluated. To evaluate the two methods, a capacitance spirometer was designed and constructed to record lung volume as lungs were vacuum degassed. When lungs containing trapped gas were degassed in a vacuum chamber, they initially expanded, then slightly decreased in volume until the vacuum was released. Lung volume rapidly decreased as the pressure in the vacuum chamber returned to ambient pressure. The results showed that oxygen absorption atelectasis was more effective in removing gas from the lungs than vacuum degassing the lungs. When vacuum degassing was use, it was found to be most effective when the pressure in the chamber was reduced to the vaporization pressure of H2O and when the lungs were degassed twice. Degassing the lungs more than twice did not significantly remove more gas from the lungs. Lung orientation did not affect the removal of gas during vacuum degassing.