Ineffectiveness of using the pressure relief valve technique during cuff inflation

Abstract

Objective: To test the effectiveness of using a cuff pressure relief valve technique to maintain cuff pressure levels within the normal in vitro range (Phase 1) in patients admitted to the intensive care unit (Phase 2) and to test the reproducibility of the technique using different syringes.

Methods: In Phase 1, a tracheal tube was inserted into a trachea model. Ten- and 20mL syringes were used to inflate the cuff through the tracheal tube. The cuff was slowly and steadily inflated until the syringe plunger would move in the opposite direction of the application. After the plunger stopped, the cuff pressures were recorded. In Phase 2, the same maneuvers for inflating the cuff were performed on 20 patients using 5, 10, and 20mL syringes and were compared with manometer measurements. The intraclass correlation coefficient and Bland-Altman analysis were employed to determine the reproducibility and agreement between syringes. Data were expressed as medians (interquartile range).

Results: There was no reproducibility between syringes with an intraclass correlation coefficient ranging between -0.33 and 0.8 (p>0.05). The pressures generated with the syringes were higher than the pressures generated using a standard manometer: the 5mL syringe pressure was 105cmH2O (82.5-120cmH2O), the 10mL syringe pressure was 69cmH2O (47.5-111.3cmH2O), and the 20mL syringe pressure was 45cmH2O (35-59.5cmH2O). The Bland-Altman analysis confirmed the large bias and variability between the syringes used, compared with the manometer.

Conclusion: The use of syringes is not an effective technique for determining the cuff pressure in patients admitted to the intensive care unit.

Figure 1

Comparisons between the initial cuff pressures (cmH₂O) (P-initial) and the cuff pressures obtained during maneuvers with 5mL (P5), 10mL (P10), and 20mL (P20) syringes in Phase 2 of the study; in vivo experiments (individual data for all patients). * p<0.001 compared with the P-initial.

Figure 2

Bland-Altman plot of the differences and means between the initial cuff pressures (P-initial) and the cuff pressures obtained during maneuvers with the 5mL (P5) (A), 10mL (P10) (B), and 20mL (P20) (C) syringes. The differences are listed on the y-axis, and the mean of the two values are on the x-axis. Bias is shown as a solid line, and the 95% limits of agreement are shown as dotted lines. ULA - 95% upper limit of agreement (bias+1.96 * standard deviation); LLA - 95% lower limit of agreement (bias-1.96 * standard deviation).