ABSTRACT
Thoracic surgeries and aesthesia for lung resection has presented anaesthesiologists with certain unique physiological problems. These include placing [lateral decubitus position] in order to obtain optimal access for most operations on lungs, pleura, esophagus, and great vessels, opening the chest wall [open pneumothorax] and one lung ventilation anaesthesia. One lung ventilation anaesthesia and lateral decubitus position produces decrease in functional residual capacity and an obligatory right to left shunt that ranges from 15% to 40% leading to increase in ventilation perfusion [V/Q] mismatch thus causing hypoxia and or hypoxemia. An optimal level of positive end expiratory pressure of 5cmH O when added to dependent lung is known to improve arterial oxygenation and improve ventilator 2 efficiency. To compare different values of positive end expiratory pressure [PEEP] during one lung ventilation, for its effects on blood arterial oxygenation and carbon dioxide levels. Study Randomized controlled trial [RCT]. Conducted in surgical Unit-III and Department of anaesthesia and Intensive Care, Combined Military Hospital, Rawalpindi. Duration of study with dates: Ten months from 25-12-2008 to 01-10-2009, Additional quantum of Data was collected from 01-01-2011 to 25-01-2011. The patients were divided into two equal groups of 100 patients each, by random allocation of patients to either in-group A [subjected to zero PEEP] or group-B [subjected to PEEP 5cm of water]. At induction and start of two lung ventilation 14 [14.0%] of the patients from group-A and 16 [16.0%] from group-B had normal PaCO. At initiation of one lung ventilation 25 [25.0%] of the patients from group-A and 80 [80.0%] from group-2 B had normal PaO. At initiation of one lung ventilation 26 [26.0%] of the patients from group-A and 80 [80.0%] from group-B had normal PaCO 2 2 with p<0.001. At end of procedure one lung ventilation 30 [30.0%] of the patients from group-A and 90 [90.0%] from group-B had normal PaO. 2 At end of procedure one lung ventilation 32 [32.0%] of the patients from group-A and 91 [91.0%] from group-B had normal PaCO. 2 The execution of one-lung ventilation still constitutes a challenge in clinical and surgical practice