Abstract

Monitoring of the effectiveness of ventilation is a significant problem during high-frequency ventilation (HFV). The time necessary to achieve equilibrium of the arterial tension of carbon dioxide (Paco2) following step changes in ventilation is appreciable, because of large body stores of CO2. Waiting for Paco2 to reach equilibrium is not only time-consuming but a potentially dangerous means of monitoring ventilator adjustments during HFV. Five kittens of mean +/- SD 1,082 +/- 383 gm weight were studied during HFV, both with normal lungs and lungs injured by saline lavage-induced surfactant depletion. The transcutaneous tension of carbon dioxide (Ptcco2) was monitored continuously to determine the time required to achieve equilibrium of Paco2 following a step change in ventilation. The rate of pulmonary CO2 elimination (VECO2) was measured immediately before and immediately after (less than 12 sec) step changes in ventilation and was used to predict the change in Paco2 achieved once equilibrium was reestablished. With normal lungs, equilibration time following step changes in ventilation was found to be approximately 20 minutes. After step decreases in ventilation of the injured lung, achieving equilibrium state took significantly longer, approximately 30 minutes. The Paco2 predicted was significantly related to the change in Paco2 achieved at equilibrium for both normal and injured lung studies. We concluded that direct monitoring of VECO2 during HFV may be a useful clinical monitoring technique, allowing rapid and accurate assessment of the efficiency of ventilation following step changes in ventilation and potentially assisting in optimizing ventilator settings.

View details for Web of Science ID A1987L110400004

View details for PubMedID 3122154