Multimodal non-invasive monitoring to apply an open lung approach strategy in morbidly obese patients during bariatric surgery

To evaluate the use of non-invasive variables for monitoring an open-lung approach (OLA) strategy in bariatric surgery. Twelve morbidly obese patients undergoing bariatric surgery received a baseline protective ventilation with 8 cmH 2 O of positive-end expiratory pressure (PEEP). Then, the OLA strategy was applied consisting in lung recruitment followed by a decremental PEEP trial, from 20 to 8 cmH 2 O, in steps of 2 cmH 2 O to find the lung’s closing pressure. Baseline ventilation was then resumed setting open lung PEEP (OL-PEEP) at 2 cmH 2 O above this pressure. The multimodal non-invasive variables used for monitoring OLA consisted in pulse oximetry (SpO 2 ), respiratory compliance (Crs), end-expiratory lung volume measured by a capnodynamic method (EELV CO2 ), and esophageal manometry. OL-PEEP was detected at 15.9 ± 1.7 cmH 2 O corresponding to a positive end-expiratory transpulmonary pressure (P L,ee ) of 0.9 ± 1.1 cmH 2 O. ROC analysis showed that SpO 2 was more accurate (AUC 0.92, IC95% 0.87–0.97) than Crs (AUC 0.76, IC95% 0.87–0.97) and EELV CO2 (AUC 0.73, IC95% 0.64–0.82) to detect the lung’s closing pressure according to the change of P L,ee from positive to negative values. Compared to baseline ventilation with 8 cmH 2 O of PEEP, OLA increased EELV CO2 (1309 ± 517 vs. 2177 ± 679 mL) and decreased driving pressure (18.3 ± 2.2 vs. 10.1 ± 1.7 cmH 2 O), estimated shunt (17.7 ± 3.4 vs. 4.2 ± 1.4%), lung strain (0.39 ± 0.07 vs. 0.22 ± 0.06) and lung elastance (28.4 ± 5.8 vs. 15.3 ± 4.3 cmH 2 O/L), respectively; all p < 0.0001. The OLA strategy can be monitored using noninvasive variables during bariatric surgery. This strategy decreased lung strain, elastance and driving pressure compared with standard protective ventilatory settings. Clinical trial number NTC03694665.