A prospective comparative study of continuous and intermittent endotracheal tube cuff pressure measurement in an adult intensive care unit
Memela, Mduduzi Emmanuel
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Introduction: The aim of this study was to establish the most reliable standard method for monitoring endotracheal tube cuff pressure in an intensive care unit. Methodology: The study was conducted at King Edward VIII Hospital ICU on adult patients undergoing prolonged intubation of more than 24 hours. Consent was obtained from the patient’s next of kin. The patient’s Pcuff for this study was recorded in two ways simultaneously for a period of 12 hours during the day. The principal investigator recorded the Pcuff thrice during the study period using the Posey cufflator®. Continuous recording was done using a pressure transducer connected to the Nihon Kohden BSM®. Factors causing changes in Pcuff were also documented. Results: Thirty-five critically ill adult patients were enrolled into the study. Nineteen (54.3%) of the subjects were male. Seventeen out of 35 subjects were studied for the entire 720 minute period. The mean time of study of the group was 667 minutes with the lowest period being 135 minutes for one patient. The group mean ± Standard deviation (SD) was 26.6 8.7 with a 95% confidence index of 9.2 – 44.0 and the median value was 25 for continuous readings. For the entire group, 13% of the time was spent in the low pressure range (< 20 cmH2O), while 23% was spent in the high pressure (> 30 cmH2O). A mean of 64% of the time was spent in the normal pressure range. Overall, the most frequently encountered events that caused pressure changes were body movement, coughing, head movement and suctioning accounting for 26.2%, 20.1%, 19.2% and 9.4% respectively. For intermittent readings, the mean ± SD of all patients for T0 was 25.3 ± 6.9; for T6 25.9 ± 8.7 and for T12 24.8 ± 3.8. The overall mean ± SD for all readings was 25.6 ± 7.1. For the entire group, 12% of the time was spent in the low pressure range (< 20 cmH2O), while 5% was spent in the high pressure (> 30 cmH2O). A mean of 83% of the time was spent in the normal pressure range. The correlation between intermittent pressure and the continuous reading at the same time was r = 0.87. iii Discussion: Continuous monitoring of Pcuff indicated that the endotracheal cuff pressure varies extensively during mechanical ventilation in critically ill patients, such variation being noted both between patients and within an individual patient. In an attempt to compare intermittent and continuous monitoring of endotracheal cuff pressures, a good correlation between the two measurements was demonstrated. However, the variations in pressures noted for an individual patient would not have been detected if endotracheal cuff pressures were monitored intermittently. Hence, with continuous monitoring the pressure changes may be detected early. Conclusion: Continuous monitoring of cuff pressure during mechanical ventilation in intensive care units is thus recommended for all patients. If intermittent monitoring is performed, it should be more frequently than eight-hourly. It is recommended that a pressure range of 20-30 cmH2O still be used as the normal range. The role of self adjusting pressure devices, although needing further exploration, holds much promise.