CPAP temporarily supports pulmonary oxygenation in morbidly obese patients

In a prospective, randomised-controlled trial, morbidly obese patients with normal lung function using post-extubation continuous positive airway pressure (CPAP) showed improved pulmonary oxygenation; however, oxygenation did not persist after termination of CPAP.

The rationale behind the study, Dr Felix Girrbach (University Hospital of Leipzig, Germany) explained, was that mechanical ventilation with individualised positive end-expiratory pressure (PEEP_IND) in combination with continuous CPAP support in the initial hours following extubation is associated with better oxygenation compared with the use of PEEP alone [1].

In this study, 46 participants with a BMI of >35 kg/m² who were scheduled to undergo bariatric laparoscopic abdominal surgery were ventilated with PEEP_IND, which was defined as “the PEEP value with the lowest regional ventilation inhomogeneity as determined by electrical impedance tomography (EIT) during a standardised decremental PEEP-trial.”

The participants were randomised to a group that received CPAP (n=21) or a control group (n=25). Baseline characteristics were similar in both groups, with a mean age of 44 years of age and a mean BMI of 46.9 kg/m². The participants in the CPAP arm received continuous CPAP support for 2 hours after extubation compared with standard supportive care for individuals in the control arm, including supplemental nasal oxygen insufflation to oxygen saturation (SpO₂) level of ≥90%. Arterial oxygen partial pressure (PaO₂)/fractional inspired oxygen (FiO₂) ratio was measured 2 hours and 4 hours after extubation, respectively.

Dr Girrbach reported that there was no difference between the groups with regard to the median PEEP_IND , which was roughly 18 cmH₂O in both arms (P=0.76). However, although oxygenation (PaO₂/FiO₂ ratio) prior to extubation was comparable between the 2 arms (P=0.32), the PaO₂/FiO₂ ratio in the CPAP group was significantly higher during CPAP support (472 mmHg in the intervention arm vs 317 mmHg in the control arm; P<0.001).

Dr Girrbach suggested that despite post-extubation CPAP support in morbidly obese patients with normal lung function, the improvement in oxygenation did not persist after termination of CPAP support, potentially pointing to atelectasis formation.

1. Girrbach F, et al. Post-extubation CPAP support and oxygenation in morbidly obese patients — a prospective randomized controlled trial. Session A63, ATS International Conference 2022, San Francisco, CA, USA, 13–18 May.

 

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Posted on 18 July, 2022