[In vitro study on the sealing effect of different shapes of cuff tracheal tubes under the lowest safe pressure].

OBJECTIVE: To compare the effectiveness of cylindrical-shaped and conical-shaped cuff catheters for airway closure using different pressure measurement methods at the lowest safe pressure and to guide the clinical application.

METHODS: Twenty-four patients with endotracheal intubation admitted to the intensive care unit (ICU) of Guangxi Medical University Cancer Hospital from December 2021 to January 2022 were enrolled. Leakage test in vitro was performed on the secretion on the patients' cuff. The needle and plunger from 20 mL syringe was separated, the syringe was sealed with adhesive, and the syringe nozzle was filled thoroughly to create a tracheal model. Consecutively, both cylindrical-shaped and conical-shaped cuff catheters were inserted into the simulated trachea, and the cuff pressure was calibrated to 20 cmH2 O (1 cmH2 O ≈ 0.098 kPa) before commencing the experiment. The viscosity of the secretion on the patients' cuff was classified (grade I was watery subglottic secretion, grade II was thick subglottic secretion, grade III was gel-like subglottic secretion), and the same viscosity secretion was injected into the catheter cuff. Utilizing a self-control approach, intermittent pressure measurement was initially conducted on both the cylindrical-shaped and conical-shaped cuff by improved pressure measurement method (intermittent pressure measurement group), followed by continuous pressure measurement experiment (continuous pressure measurement group). The leakage volume of the three viscosity subglottic secretions and the values of cuff pressure measurement of different shaped cuff catheters at 4, 6, 8 hours of inflation were recorded.

RESULTS: A total of 180 retention samples were extracted from 24 patients with tracheal intubation during ventilation, with 90 samples in each of the two groups using different pressure measurement methods, and 30 samples of retention materials with different viscosities in each group. In the intermittent pressure measurement group, at 4 hours of inflation, all samples of secretion with grade I and grade II on cylindrical-shaped cuff leaked, while 3 samples of secretion with grade III also leaked. For conical-shaped cuff, 28 samples of secretion with grade I leaked, only 2 samples of secretion with grade II leaked, and there was no leak for secretion with grade III. At 6 hours of inflation, all samples of the three viscosity secretions on different shaped cuffs leaked. The leakage was gradually increased with the prolongation of inflation time. In the continuous pressure measurement group, at 4 hours of inflation, all samples of secretion with grade I on cylindrical-shaped cuff leaked, while 29 samples of secretion with grade II leaked, and there was no leak for secretion with grade III. For the conical-shaped cuff, 26 samples of secretion with grade I leaked, and there was no leak for secretion with grade II and grade III. At 6 hours of inflation, the conical-shaped cuff still had no leak for secretion with grade III. As the inflation time prolonged, the leakage of subglottic secretion on different shaped cuffs in both groups was gradually increased. At 8 hours of inflation, all samples experienced leakage, but the leakage of subglottic secretion on different shaped cuffs in the continuous pressure measurement group was significantly reduced as compared with the intermittent pressure measurement group [leakage for secretion with grade III (mL): 1.00 (0.00, 1.25) vs. 2.00 (1.00, 2.00) on the cylindrical-shaped cuff, 1.00 (0.00, 1.00) vs. 2.00 (2.00, 2.00) on the conical-shaped cuff, both P < 0.01]. The values of pressure measurement of cuffs with different shapes at different time points of inflation in the continuous pressure measurement group were within the set range (20-21 cmH2 O). The cuff pressure at 4 hours of inflation in the intermittent pressure measurement group was significantly lower than the initial value (cmH2 O: 18.3±0.6 vs. 20.0±0.0 in the cylindrical-shaped cuff, 18.4±0.6 vs. 20.0±0.0 in the conical-shaped cuff, both P < 0.01), and the cuff pressure in both shaped cuffs showed a significant decrease tendency as inflation time prolonged. However, there was no statistically significant difference in values of pressure measurement between the different shaped cuff catheters.

CONCLUSIONS: Continuous pressure monitoring devices can maintain the effective sealing of conical-shaped cuff catheters at the lowest safe pressure. When using an improved pressure measurement method for intermittent pressure measurement and/or using a cylindrical cuff catheter, the target pressure should be set at 25-30 cmH2 O, and the cuff pressure should be adjusted regularly.