[Experimental study of the monitoring bias of pressure in intubation balloon using handheld pressure gauge]

Abstract

Objective: To explore the bias between the real pressure and the measured values when handheld pressure gauge (HPG) was used to monitor intermittently the pressure in the intubation balloon, so as to provide some measures for the correct use of HPG.

Methods: In the first part of the study, HPG was used to measure the pressure with the balloon connected with a three-way tube with which to control the inflation and deflation in a laboratory to measure the pressure in the air bag. After gaining the deviation in this in vitro experiment, it was tested and verified in vivo in adult patients undergoing endotracheal intubation.

Results: After 132 times of measurements, it was found that measurement with a HPG might result in an "inherent loss" (3.928±0.291) cmH2O (1 cmH2O=0.098 kPa, t=155.273, P=0.000) between inflation value [(30.000±0.000) cmH2O] and measured value [(26.072±0.291) cmH2O]. In addition, after 214 times repeated measurements, the pressure "loss" during disconnection of the gauge was as high as (1.196±0.954) cmH2O (t=18.348, P=0.000) between filled values [(30.000±0.000) cmH2O] and measured values [(28.804±0.954) cmH2O] and it was named as "error loss". At last, the total error was verified by clinical test, and it was (5.270±2.583) cmH2O (t=29.632, P=0.000) between pressure of filled value [(30.000±0.000) cmH2O] and measured value [(24.730±2.583) cmH2O].

Conclusions: When the balloon pressure was monitored intermittently with HPG, the real value should be the measured value plus the "error". In addition, subglottic aspiration should be done before the connection of the balloon to the gauge to prevent the secretions on the cuff falls into the deeper airway, and to maintain the cuff pressure at 30 cmH2O.