Comparison of Blood Gases of Ventilated Patients During Transport.

Gervais HW, Eberle B, Konietzke D, Hennes HJ, Dick W Critical Care Medicine 1987 Vol 15 Pages 761-763

Blood gas variables were compared during the transport of 30 ventilator-dependent patients. 10 were ventilated with a manual resuscitation bag alone (unmonitored), 10 with a tidal volume meter at the exhalation valve of the resuscitation bag (monitored), and the final 10 with a portable Drager Oxylog ventilator set to the same minute volume used in the ICU. Blood gases were analyzed before and at the end of transport. Transport duration varied between 15-25 minutes for all cases. In the unmonitored group, significant decreases occurred in arterial pCO2 (p<.01) and pO2 (p<.01). Arterial pH (p<.05) increased. There were no statistically significant changes in the monitored group whereas arterial pCO2 (p<.05) decreased and pH (p<.01) increased in the ventilator group. The authors note that during transport, the Oxylog did not deliver the preset minute volume, exceeding it by 2.35 +/- 0.6 lpm. This propensity to overventilate was confirmed in later tests of six separate devices. This was considered a concern as hyperventilation is experimentally and clinically well documented as a triggering event for coronary vasospasm. The authors conclude that minute volumes should be monitored during transport of ventilated patients. The technique is inexpensive and can be accomplished easily by attaching a respirometer to the outlet of the nonrebreathing valve of the bag or ventilator, thus optimizing patient care whenever ventilation during transport is necessary.