The interaction between increased Intra Abdominal Pressure (IAP) and Intrathoracic Pressure under different Positive End Expiratory Pressure (PEEP) levels is intriguing, since these two conditions coexist frequently in several clinical settings. The aim of our study was to investigate the interaction between different PEEP levels and increased IAP during laparoscopic cholecystectomy. In fifty two patients, who underwent scheduled laparoscopic cholecystectomy, cardiovascular parameters were determined by an Oesophageal Doppler Monitor device during two different time periods, before and after pneumoperitoneum, and under five conditions: (i) PEEP 0 cmH2O (ii) PEEP 5cm H2O (iii) PEEP 10cm H2O (iv) PEEP 15cm H2O and (v) in the absence of PEEP or ventilation. Cardiac output and stroke volume showed a statistically significant decrease compared to the baseline value after the application of different PEEP levels, when there was no pneumoperitoneum (p<0.05). However, both parameters increased, when PEEP and pneumoperitoneum were applied together (p<0.001). Corrected flow time, peak flow velocity in the descending thoracic aorta and mean acceleration showed similar alterations but not at all PEEP levels. Finally, αt the no PEEP or ventilation phase, the negative effects of increased IAP on the cardiocirculatory function were predominant. According to these results, application of PEEP seems to counterbalance the negative hemodynamic effects of increased IAP. Moreover, it could also be concluded that ‘ideal’ PEEP level might be the one that borders the IAP level, since the best cardiac output and stroke volume values were reported at that point.

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The occurrence of intraoperative oxygenation impairment is common even in healthy individuals and will vary depending on the patient and the type of surgery. The purpose of this study was to evaluate the incidence of oxygenation impairment in patients with normal lung function and to study the safety and efficacy of three different recruitment strategies. Out of a total number of 430 patients, 150 patients developed intraoperative oxygenation impairment, which was defined as the drop of PaO2/FiO2 ratio below 300. These 150 patients were randomly assigned into four study groups according to the recruitment strategy applied. Group A (N: 38): Application of three hyperinflations of the lungs at airway pressure 40cmH2O for 10 sec, followed by an increase in PEEP from 5 to 10cmH2O. Group B (N: 38): Increase in PEEP from 5 to 10cmH2O. Group C (N: 37): Application of three hyperinflations of the lungs at airway pressure 40cmH2O for 10 sec, without any PEEP alteration and Group D (N: 37): No maneuver. Measurements were taken at the phase of oxygenation deterioration and at 5, 15, 30, 45 and 60min after applying the maneuvers and also before extubation. From a total of 430 patients 150 developed oxygenation impairment (38.4%). The median onset time of the deterioration was 30min after intubation and mechanical ventilation. In group A the PaO2/FiO2 ratio increased significantly immediately after the maneuvers and remained elevated until extubation. In group B the PaO2/FiO2 ratio presented a gradual increase to significant levels before extubation. In group C, the instant post-maneuver increase of oxygenation was not sustained until extubation. Finally in group D a gradual decrease of the PaO2/FiO2 ratio was recorded until the end of surgery. According to the results of our study, one third of patients developed intraoperative oxygenation impairment approximately half an hour after intubation. The application of three hyperinflations of the lungs at an airway pressure of 40cmH2O for 10 sec, followed by an increase in PEEP from 5 to 10cmH2O proved to be the most effective treatment of impaired oxygenation.

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