The Effect of Alveolar Recruitment Maneuvres on Arterial Oxygenation and Lung Compliance During General Anesthesia

Background: General anesthesia is associated with hypoxemia and atelectasis that is promoted by high inspiratory oxygen concentration. In this trial, the effect of PEEP versus PEEP with recruitment manoeuvre during general anesthesia in improving the arterial oxygenation and lung compliance has been studied. Patients and Methods: The study included ninety adult patients ASA I or II, undergoing surgery of 2 hours or more under a standardized general anesthesia technique and ventilated in a volume controlled mode at VT 8 ml/kg and frequency 10-12 bpm to maintain normocarbic. After about 30 mins when patients were vitally stable, they were allocated randomly to three equal sized groups according to the maneuvre done. In group I, same ventilator setting with no PEEP. In group II, PEEP of 5 cm H2O was added and in group III, recruitment was achieved by applying gradual increased PEEP levels up to 15 cm H2O, I E ratio 1:1, RR 7bpm and increased VT until a PIP of 40 cmH2O for 30 seconds. The procedure was performed once and PEEP maintained at 5 cmH2O allthrough. Intraoperative hemodynamics, oxygen saturation, endtrial CO2, arterial blood gases and lung compliance were compared in the three groups. Results: No significant statistical difference was found between the three groups as regards the age, sex, weight, height. BMI, type and duration of surgery, blood loss and need for bloodtransfusion and amount of IV fluids (P 0.05). End-tidal CO2, oxygen saturation, arterial pH, Paco2 and HCO3 concentration and base deficit were the same in the three groups and did not change significantly from their base line values (P 0.05). Pao2 was significantly lower (P 0.05) in the control group [204(14.2)mmHg] relative to the other two groups intraoperatively. 5 mins after the maneuvre, with no significant difference between PEEP group [241(14.9)mmHg] and recruitment group [245(13.8)mmHg]. After 15 mins. of the maneuvre PaO2 was significantly lower (P 0.05) in the control group [204(14.1)] relative to PEEP group [241(14.8)] and recruitment group [245(13.9)], with no significant difference between PEEP and recruitment groups. However, 30 mins following the maneuvre, Pao2 decreased somewhat in the PEEP group [231 (13.9)mmHg] while it remained high in the recruitment group [244(14.1) mmHg] (P 0.05). Static lung compliance (Tidal volume/Plateau pressure-PEEP) decreased gradually in the control group to become significantly less than baseline and other two groups (P 0.05). In PEEP group, it remained similar to its baseline all through the study but 30 mins after the maneuvre it became significantly less than baseline and recruitment group. In the recruitment group, compliance increased dramatically 30 mins after the maneuvre to become significantly higher than its base line and the other two groups (P 0.05). Conclusion: Addition of PEEP to the ventilator circuit during general anesthesia conduct could improve arterial oxygen tension without increasing inspired oxygen faction; moreover, addition of recruitment maneuvre with sustained increased in inspiratory airway pressure of 40 cmH2O would further improve arterial oxygen tension and lung compliance. This easy recruitment showed no complications.