Equal ratio ventilation (1:1) improves arterial oxygenation during laparoscopic bariatric surgery: A crossover study

Abstract

Background:Hypoxaemia and high peak airway pressure (Ppeak) are common anesthetic problems during laparoscopic bariatric surgery. Several publications have reported the successful improvement in arterial oxygenation using positive end expiratory pressure and alveolar recruitment maneuver, however, high peak airway pressure during laparoscopic bariatric surgery may limit the use of both techniques. This study was designed to determine whether equal I:E (inspiratory-to-expiratory) ratio ventilation (1:1) improves arterial oxygenation with parallel decrease in the Ppeak values.Methods:Thirty patients with a body mass index ≥40 kg/m2 scheduled for laparoscopic bariatric surgery were randomized, after creation of pneumoperitoneum, to receive I:E ratio either 1:1 (group 1, 15 patients) or 1:2 (group 2, 15 patients). After a stabilization period of 30 min, patients were crossed over to the other studied I:E ratio. Ppeak, mean airway pressure (Pmean), dynamic compliance (Cdyn), arterial blood gases and hemodynamic data were collected at the end of each stabilization period.Results:Ventilation with I: E ratio of 1:1 significantly increased partial pressure of O2 in the arterial blood (PaO2), Pmean and Cdyn with concomitant significant decrease in Ppeak compared to ventilation with I: E ratio of 1:2. There were no statistical differences between the two groups regarding the mean arterial pressure, heart rate, respiratory rate, end tidal CO2 or partial pressure of CO2 in the arterial blood.Conclusion:Equal ratio ventilation (1:1) is an effective technique in increase PaO2 during laparoscopic bariatric surgery. It increases Pmean and Cdyn while decreasing Ppeak without adverse respiratory or hemodynamic effects.

The Effect of Ventilation Strategy on Arterial and Cerebral Oxygenation During Laparoscopic Bariatric Surgery

“…However, previous studies report that prolonged inspiratory time did not deteriorate but rather improved CO 2 removal by decreasing airway dead space and increasing alveolar ventilation [4,23,24]. In addition, pressure-controlled ventilations with I/E ratios of 1:1 and 1:2 showed comparable CO 2 removal during laparoscopic bariatric surgery [6]. This result was consistent with our result.…”

“…In addition, since the negative effect of obesity on arterial oxygenation is not likely to be compensated by increased tidal volume or respiratory rate [13], additional ventilation strategy is often sought. In an earlier study of laparoscopic bariatric surgery, compared to conventional ratio ventilation, equal I/E ratio ventilation improved respiratory mechanics and arterial oxygen tension during pressure-controlled ventilation with a PEEP 5 cmH 2 O [6], which is partly consistent with our results. In the present study, equal ratio ventilation tended (not statistically significant) to improve arterial oxygen tension but significantly ameliorated respiratory mechanics.…”

“…Studies on prolonged I/E ratio ventilation during laparoscopic surgery and one lung ventilation also reported favorable results in terms of oxygenation and respiratory mechanics [4,5]. Recently, prolonged I/E ratio ventilation of 1:1 was reported to improve arterial oxygenation in morbidly obese patients undergoing bariatric surgery [6]. They suggested that the benefit of prolonged I/E ratio results from increased mean airway pressure and dynamic compliance, which must have recruited collapsed alveoli [6].…”

“…Recently, prolonged I/E ratio ventilation of 1:1 was reported to improve arterial oxygenation in morbidly obese patients undergoing bariatric surgery [6]. They suggested that the benefit of prolonged I/E ratio results from increased mean airway pressure and dynamic compliance, which must have recruited collapsed alveoli [6]. However, this increase in mean airway pressure may have negative impact on hemodynamic and cerebral oxygenation, especially when the patient is positioned in reverse Trendelenburg position [7,8].…”

Intraoperative ventilation strategies for obese patients undergoing bariatric surgery: systematic review and meta-analysis

“…Random sequence generation and allocation concealment were correctly described in seven studies [14,17,19,20,22,24,25]. In the blinding of participants and personnel domain all the studies were classified as high risk as the personnel could not be blinded.…”