POSITIVE END EXPIRATORY PRESSURE (PEEP);

COMPARISON DIFFERENT VALUES DURING ONE LUNG VENTILATION, FOR ITS EFFECTS ON BLOOD ARTERIAL OXYGENATION AND CARBON DIOXIDE LEVELS

Abstract

Introduction: 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. Objectives: 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 Design: Randomized controlled trial (RCT). Setting: 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. Subjects and methods: 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). Results: 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
Conclusions: The execution of one-lung ventilation still constitutes a challenge in clinical and surgical practice.