Background: Morbid obesity is associated with several respiratory function alterations i.e. decreased lung
compliance. Mechanical ventilation in this group of patients is difficult to perform and requires significantly higher airway pressures to achieve appropriate tidal volume and gas exchange. Weight loss improves respiratory functions. However, its influence on mechanical ventilation conditions is still not well described.
Case report: In four morbidly obese male patients with BMI > 50 kg m-2, the mechanical ventilation conditions were observed during RYGB surgery (Roux-en-Y gastric by-pass- a surgical method of treatment of severe obesity), and several months after, during incisional hernia repair, when weight loss achieved 25% (BMI 41 kg m-2). The results were compared to group of 25 nonobese individuals (BMI< 25 kg m-2 ) and 22 morbidly obese with BMI about 42 kg m-2.
The study revealed that, however studied subjects are still considered as morbidly obese, their
lung compliance increased significantly achieving level more similar to nonobese than to obese patients with similar BMI (58.4± 9.1 vs. 65.1± 6.6 vs. 40.8± 6.1 respectively).
Conclusions: In conclusion we claim that weight loss in morbidly obese improves mechanical ventilation
conditions more rapidly than it would result from actual weight loss.

Keywords: gastric-bypass-adverse-effects, body-mass-index, gastric-bypass-methods, obesity-morbid diagnosis, Obesity, respiratory-function-tests, Lung-Compliance-physiology, weight-loss-physiology