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JOURNAL TITLE: Journal of Medical Academics
Background: Laparoscopic surgery is performed under general anesthesia with mechanical ventilation, and a high-volume, low-pressure endotracheal tube (ETT) with a sealing cuff pressure about 20–30 cm of H2O is commonly used for a proper seal and avoidance of overinflation. Nitrous oxide (N2O) is an inhalational anesthetic that is used with oxygen in the ratio 50:50 for the maintenance of anesthesia if there is no facility of medical air. However, N2O increases the intracuff pressure of the tracheal tube due to diffusion of N2O in to cuff during general anesthesia. The present research was done to study the cuff pressure changes during laparoscopic surgeries with N2O anesthesia and to assess its variation during the various stages of surgery and also its correlation with position of the patient. Materials and methods: A study was done in a tertiary-level hospital over a period of 1 year in 70 patients undergoing laparoscopic surgery. Endotracheal tube was inflated with incremental doses of 0.5 mL of air to a point where no leak on auscultation on the suprasternal area was noted. Cuff pressure measurement using cuff pressure monitor (Hand pressure gauge) was done at the time of first inflation of cuff up to 20–30 cm of H2O and airway pressure, along with total amount of air inflated was noted as “zero” reading. Thereafter, cuff pressure was measured at regular interval of 5 minutes. Cuff pressures and airway pressures were taken just prior to insufflation, 2 minutes after abdominal insufflation, thereafter every 15 minutes throughout surgery, and 2 minutes after desufflation and prior to extubation. Results: Out of 70 patients, maximum patients were of the age-group of 20–50 years (78.5%). There was no statistically significant difference between the groups. Cuff pressure at the induction was kept in range of 20–30 cm of H2O. In this study, mean tracheal cuff pressure at baseline was 21.10 + 6.16 (p value of 0.207) and prior to insufflation was 21 + 7.13 (p value of 0.733). The cuff pressures at 2 minutes post insufflation (P2), P15, P30, P45, and P60 were 31.40 ± 12.54 cm of H2O, 25.79 ± 8.68 cm of H2O, 24.61 ± 7.37 cm of H2O, 23.83 ± 9.43 cm of H2O, and 24.63 ± 4.77 cm of H2O, respectively. p value was strongly significant showing a positive correlation between pneumo-peritoneum and cuff pressures. We could see the cuff pressure continuously increasing in successive readings. Post desufflation and prior to extubation, there was a fall in cuff pressure with mean cuff pressure being 17.24 + 5.32 cm of H2O and 15.27 + 4.00 cm of H2O, respectively, which also suggests that cuff pressures increased with pneumoperitoneum. Conclusion: Use of N2O increases the cuff pressure (31.4 + 12.54 cm of H2O), especially immediately post-insufflation (35.54 + 12.06 cm of H2O), more so in head low position (36.28 + 12.13 cm of H2O). Mean airway pressure (Ppeak) also increased with pneumoperitoneum (22.60 + 4.38 cm of H2O). The regular monitoring of endotracheal tube cuff pressure should be a part of regular safe practice of anesthesia, and use of handy device like hand pressure gauge should be implemented in regular practice where N2O is used.
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