Effects of Increasing Airway Pressures on the Pressure of the Endotracheal Tube Cuff During Pelvic Laparoscopic Surgery.

BACKGROUND: Tracheal tube cuff pressures exceeding the perfusion pressures of the tracheal mucosa have been associated with complications such as sore throat, tracheal mucosa ulcers, tracheal rupture, and subglottic stenosis. Despite appropriate inflation, many factors can increase the tracheal cuff pressure during mechanical ventilation. This prospective observational cohort study was designed to test the hypothesis that during a clinical model of decreasing respiratory compliance, the pressure within the endotracheal tube cuff will rise in direct relationship to increases in the airway pressures.

METHODS: Twenty-eight adult obese patients (BMI ≥30 kg/m) scheduled for elective laparoscopic gynecologic procedures were enrolled. All patients received general anesthesia utilizing endotracheal tubes with low-pressure high-volume cuffs. After baseline adjustment of the cuff pressure to 25 cm H2O, the airway pressures and endotracheal cuff pressures were continuously measured using pressure transducers connected to the anesthesia circuit and cuff pilot, respectively. Data on cuff and airway pressures, mechanical ventilation parameters, intraabdominal pressures, and degree of surgical table inclination were collected throughout the anesthetic procedure. General linear regression models with fixed and random effects were fit to assess the effect of increases in airway pressures on cuff pressure, after adjusting for covariates and the clustered structure of the data.

RESULTS: The mean (standard deviation) age and body mass index were 42.2 (8.8) years and 37.7 (5.1) kg/m, respectively. After tracheal intubation, the cuffs were overinflated (ie, intracuff pressures >30 cm H2O) in 89% of patients. The cuff pressures significantly changed after concomitant variations in the airway pressures from a mean (standard error) value of 29.6 (1.30) cm H2O before peritoneal insufflations, to 35.6 (0.68) cm H2O after peritoneal insufflation, and to 27.8 (0.79) cm H2O after peritoneal deflation (P < .0001). The multilevel mixed regression models revealed that after controlling for clustering of the data (at the patient and study phase levels) and covariates, increased peak airway pressures were significantly associated with increased pressures within the endotracheal cuff (coefficient [95% confidence interval], 0.25 [0.14-0.36]; P < .0001). Other variables associated with increasing endotracheal cuff pressure included degree of surgical table inclination (0.08 [0.04-0.12]; P = .0003) and I:E ratio of 1:1 (4.47 [2.10-6.83]; P = .0002).

CONCLUSIONS: This clinical model of decreased respiratory compliance in mechanically ventilated patients reveals that the pressure within the endotracheal cuff significantly changes in direct relation to changes in the airway pressures. This finding may have clinical relevance in patients requiring prolonged use of high airway pressures.