A prolonged inspiratory time demonstrated a beneficial effect on oxygenation. Furthermore, it showed better CO2 elimination without elevating the peak or plateau airway pressure compared with applying external PEEP. In terms of gas exchange and respiratory mechanics, a prolonged inspiratory time appears to be superior to applying external PEEP in patients undergoing laparoscopic surgery in the Trendelenburg position.

SummaryWe evaluated the effects of a prolonged inspiratory time on gas exchange in subjects undergoing one-lung ventilation for thoracic surgery. One hundred patients were randomly assigned to Group I:E = 1:2 or Group I:E = 1:1. Arterial blood gas analysis and respiratory mechanics measurements were performed 10 min after anaesthesia induction, 30 and 60 min after initiation of one-lung ventilation, and 15 min after restoration of conventional two-lung ventilation. The mean (SD) ratio of the partial pressure of arterial oxygen to fraction of inspired oxygen after 60 min of onelung ventilation was significantly lower in Group I:E = 1:2 compared with Group I:E = 1:1 (27.7 (13.2) kPa vs 35.2 (22.1) kPa, respectively, p = 0.043). Mean (SD) physiological dead space-to-tidal volume ratio after 60 min of onelung ventilation was significantly higher in Group I:E = 1:2 compared with Group I:E = 1:1 (0.46 (0.04) vs 0.43 (0.04), respectively, p = 0.008). Median (IQR [range]) peak inspiratory pressure was higher in Group I:E = 1:2 compared with Group I:E = 1:1 after 60 min of one-lung ventilation (23 (22-25 [18-29]) cmH 2 O vs 20 (18-21 [16-27]) cmH 2 O, respectively, p < 0.001) and median (IQR [range]) mean airway pressure was lower in Group I:E = 1:2 compared with Group I:E = 1:1 (10 (8-11 [5-15]) cmH 2 O vs 11 (10-13 [5-16]) cmH 2 O, respectively, p < 0.001). We conclude that, compared with an I:E ratio of 1:2, an I:E ratio of 1:1 resulted in a modest improvement in oxygenation and decreased shunt fraction during one-lung ventilation. Deterioration in pulmonary gas exchange results in serious adverse effects during one-lung ventilation (OLV) [1,2], with significant hypoxaemia occurring in 5-10% of patients. The pathophysiology of gas exchange disturbance during OLV is attributed to intrapulmonary shunt due to collapse of the nonventilated lung and ventilation/perfusion (V/Q) mismatch due to an increase in atelectasis in the dependent lung [2][3][4]. We hypothesised that oxygenation during OLV would be improved by applying inverse-ratio ventilation (IRV), with the resultant increase in mean airway pressures reducing atelectasis in the dependent lung and thus reducing V/Q mismatch. Inverse-ratio ventilation is a prolonged inspiratory time compared with expiratory time and is known to be effective for increasing oxygenation and reducing peak airway Anaesthesia 2013Anaesthesia , 68, 908-916 doi:10.1111 pressures in adults with respiratory distress syndrome [5] and respiratory failure [6]. Previous studies evaluating the effect of IRV during general anaesthesia revealed no muscle-sparing [7] or only a marginal improvement in gas exchange [8,9]; however, there have been no studies investigating the effectiveness of IRV in subjects undergoing OLV for lung surgery. The aim of our study was to evaluate whether a prolonged inspiratory time improves gas exchange and respiratory mechanics in patients undergoing lung surgery with OLV compared with conventional ventilatory settings. However, a considerable amount of auto-positive e...

We can conclude that, when combining the main spinal and the supporting epidural anesthesia, CSEA has greater efficacy and fewer side effects than the pH-adjusted EA in cesarean sections.