Comparing nasopharyngeal apnoeic oxygenation at 18 l/min to preoxygenation alone in obese patients - A randomised controlled study.

STUDY

OBJECTIVE

Investigate a low-cost, nasopharyngeal apnoeic oxygenation technique, establish its efficacy, and compare it to preoxygenation only in an obese population. The study's hypothesis was that nasopharyngeal apnoeic oxygenation at 18 l.min-1 would significantly prolong safe apnoea time compared to preoxygenation alone.

DESIGN

Randomised controlled study.

SETTING

Theatre complex of a resource constrained hospital.

PATIENTS: 30 adult, obese (BMI ≥ 35 kg.m-2) patients presenting for elective surgery. Patients with limiting cardio-respiratory disease, suspected difficult airway, risk of aspiration, and that were pregnant, were excluded. Patients were allocated by block randomisation in a 1:2 ratio to a preoxygenation-only (No-AO) and an intervention group (NPA-O2).

INTERVENTIONS: All patients were preoxygenated to an Et-O2 > 80%, followed by a standardised induction. The intervention group received oxygen at 18 l.min-1 via the nasopharyngeal catheter intervention. The desaturation process was documented until an SpO2 of 92% or 600 s was reached.

MEASUREMENTS: Baseline demographic and clinical characteristics were collected. The primary outcome was safe apnoea time, defined as the time taken to desaturate to an SpO2 of 92%. Secondary outcomes were rate of carbon dioxide accumulation and factors affecting the risk of desaturation.

MAIN

RESULTS

The study was conducted in a morbidly obese population (NoAO = 41,1 kg.m-2; NPA-O2 = 42,5 kg.m-2). The risk of desaturation was signifantly lower in the intervention group (Hazzard Ratio = 0,072, 95% CI[0,019-0,283]) (Log-Rank test, p < 0.001). The median safe apnoea time was significantly longer in the intervention group (NoAO = 262 s [IQR 190-316]; NPA-O2 = 600 s [IQR 600-600]) (Mann-Whitney-U test, p < 0.001). The mean rate of CO2 accumalation was significantly slower in the intervention group (NoAO = 0,47 ± 0,14 kPa.min-1; NPA-O2 = 0,3 ± 0,09 kPa.min-1) (t-test, p = 0.003). There were no statistically significant risk factors associated with an increased risk of desaturation found.

CONCLUSIONS

Nasopharyngeal apnoeic oxygenation at 18 l/min prolongs safe apnoea time, compared to preoxygenation alone, and reduces the risk of desaturation in morbidly obese patients.

CLINICAL TRIAL REGISTRATION: PACTR202202665252087; WC/202004/007.