Ventilatory Response at Rest and During Maximal Exercise Testing in Patients with Severe Obesity Before and After Sleeve Gastrectomy

Introduction: Sleeve gastrectomy (SG) has become a widespread treatment option in patients affected by severe obesity. However, studies investigating the impact of the subsequent weight loss on the ventilatory response at rest and during physical exercise are lacking. Methods: This is an observational study on 46 patients with severe obesity (76% females), comparing parameters of ventilatory function 1 month before and 6 months after SG. Patients were first evaluated by resting spirometry and subsequently with an incremental, maximal cardiopulmonary exercise test (CPET) on treadmill. Results: The important weight loss of 26.35 ± 6.17% of body weight (BMI from 43.59 ± 5.30 to 32.27 ± 4.84 kg/m2) after SG was associated with a significant improvement in lung volumes and flows during forced expiration at rest, while resting ventilation and tidal volume were reduced (all p ≤ 0.001). CPET revealed decreased ventilation during incremental exercise (p < 0.001), with a less shallow ventilatory pattern shown by a lower increase of breathing frequency (∆BFrest to ATp = 0.028) and a larger response of tidal volume (∆TVAT to Peakp < 0.001). Furthermore, a concomitant improvement of the calculated dead space ventilation, VE/VCO2 slope and peripheral oxygen saturation was shown (all p ≤ 0.002). Additionally, the increased breathing reserve at peak exercise was associated with a lower absolute oxygen consumption but improved exercise capacity and tolerance (all p < 0.001). Conclusion: The weight loss induced by SG led to less burdensome restrictive limitations of the respiratory system and to a reduction of ventilation at rest and during exercise, possibly explained by an increased ventilatory efficiency and a decrease in oxygen demands.