Apnea Testing Practice to Increase Baseline PaCO2 and Frequency of Blood Gas Analyses

Abstract

ObjectiveTo study the influence of the initial partial pressure of carbon dioxide (PaCO2) and frequency of blood gas analyses on the positivity rate and safety of apnea testing (AT). Designprospective multicenter cohort study. SettingSeven teaching hospitals. Participants55 patients who underwent AT. InterventionsPatients were divided into two groups according to their initial PaCO2: the experimental group (≥40 mmHg, 27 patients) and control group (<40 mmHg, 28 patients). Blood gas analysis was performed at 3 min, 5 min and 8 min, and vital signs were taken. AT results and complications were compared between groups. ResultsThe initial PaCO2 of the experimental group was 42.8±2.2 mmHg vs. 36.4±2.9 mmHg in the controls. The AT positivity rate was 100%. The experimental group needed less time to reach the target PaCO2 than the control group (4.07±1.27 min vs. 5.68±2.06 min; P=0.001). Twenty-six patients (96.3%) in the experimental group reached the target PaCO2 in 5 minutes vs. 17 in the control group (60.7%) (P=0.001). Seven patients (12.7%) were unable to complete 8 min disconnection due to hypotension. The experimental group had a slightly lower incidence of hypotension than the control group, but there was no statistical difference (7.4% vs. 17.9%, P=0.245). ConclusionIncreasing the baseline PaCO2 and doing more blood gas analyses can significantly shorten the time needed for AT and improve the AT positivity rate.