الفهرس 
The effect of pressure controlled ventilation on hemodynamics andpulmonary mechanics in prone patients undergoing elective spine surgeries :Comparative study with volume controlled ventilation
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Abstract
As patients turned into prone position experienced more decrease in lung compliance than those on supine position, this prospective, randomized study was designed to compare the effect of PCV and volume-controlled ventilation (VCV) on lung mechanics and heamodynamics in the prone position using the wilson frame during elective lumbar spine surgery. Sixty patients scheduled for elective lumbar spine surgery were randomly allocated to receive mechanical ventilation using either the VCV (n=30) or PCV (n=30) mode. Hemodynamic variables (heart rate, mean arterial blood pressure). Respiratory variables (peak airway pressure, mean airway pressure, shunt fraction, alveolar-arterial oxygen gradient). Dynamic compliance (Cdyn) of the respiratory system was calculated as VT/ (Ppeak-PEEP). The alveolar dead space-to-tidal volume ratio (VD/VT) will be estimated using the hardman and aitkenhead equation: VD/VT=1.135{u00D7}(PaCO2-ETCO2) / (PaCO2-0.005). The Ppeak in the PCV group was lower than that in the VCV group throughout the study period (P value=0.961and 0. 0.109 at supine position and prone position, respectively) and was increased at prone position compared with supine position in both groups. Cdyn was decreased from supine to prone position in both groups. However, the Cdyn in the PCV group was higher than that in the VCV group during the study period however it is only statistically significant after 1.5 and 2 hrs. The arterial oxygen tension was comparable between the 2 groups during the study period