Variations in endotracheal tube cuff pressure : is 8-hourly monitoring enough?

Abstract

Background. Most patients admitted to an intensive care unit (ICU) for mechanical ventilation require endotracheal intubation. Cuffed endotracheal tubes (ETTs) are utilised as they provide a better seal to facilitate ventilation and minimise aspiration. Complications due to overinflation or underinflation of the cuff may occur. Neither the frequency of intermittent cuff pressure (Pcuff) measurement nor the advantage of continuous Pcuff monitoring has been clearly established. Objective. To determine deviations in ETT Pcuff from the recommended range during the intervals between routine thrice-daily Pcuff measurements in adult ICU patients. Our key objective was to identify the extent and cause of ETT Pcuff changes during these intervals. In addition, we attempted to demonstrate the failure of routine thrice-daily Pcuff monitoring to detect the large variation in Pcuff of patients throughout the day. Methods. This prospective, observational study was conducted in the King Edward VIII Hospital ICU, Durban, KwaZulu-Natal Province, South Africa. Ethical and institutional approval was obtained. Consent was obtained from patients' next of kin. Intermittent Pcuff was recorded using mechanical manometers, and continuous measurements using pressure transducers. Results. Thirty-five critically ill adult patients were enrolled. The mean study time was 11.1 h. The mean Pcuff was 25.6 (standard deviation 7.1) cmH 2 O for the intermittent group and 26.6 (8.7) cmH 2 O for the continuous group. The intermittent pressure measurements were in the low-pressure range (<20 cmH 2 O) 12% of the time compared with 83% in the target pressure range (20 -30 cmH 2 O) and 5% in the high-pressure range (>30 cmH 2 O). For continuous pressures, 13% of the time was spent in the low-pressure range, 64% in the target pressure range, and 23% in the high-pressure range. For the entire study, 588 events causing Pcuff alterations were recorded. Conclusion. Continuous monitoring of Pcuff indicated that the endotracheal Pcuff varied extensively during mechanical ventilation in critically ill patients, such variation being noted both between patients and within individual patients. Variations in individual patients occurred both during intrinsic patient activities and those of ICU personnel as part of routine patient maintenance. Intermittent monitoring may not detect these variations. Continuous monitoring of Pcuff during mechanical ventilation in ICUs is thus recommended for all patients.