ABSTRACT
Objective To investigate the correlation between arterial carbon dioxide partial pressure (PaCO2 )and end-tidal carbon dioxide partial pressure (PET CO2 )in prone position operation and calculate the value of PaCO2 according to the PET CO2 .Methods Forty patients with ASA Ⅰ orⅡ undergoing spinal surgery were selected,and the values of PaCO2 and PET CO2 as basic value (T0 ) after induction of general anesthesia in supine position monitor and record the value of PET CO2 and PaCO2 in prone position after 30 min (T1 ),60 min (T2 )and 90 min (T3 ).The correlation between PaCO2 and PET CO2 in each time point were analyzed,and the equation of PaCO2 (y)and PET CO2 (x) with curve fitting and difference of PaCO2 and PET CO2 were calculated.Results There was significant correlation between PaCO2 and PET CO2 in the supine and prone position,their correlation coefficients were r 0 =0.84,r 1 =0.88,r 2 =0.84,r 3 =0.82 (P <0.01).The Pa-ET CO2 was (5.3±2.1)(T0 )in supine position and (6.6± 2.1 )mm Hg (T1 ),(5.8 ± 2.2 )mm Hg (T2 ),(5.9 ± 2.1 )mm Hg (T3 )in prone position.The equation in each time point PaCO2 (y)and PET CO2 (x)were y0 =1.1 x0 +2.5,y1 =1.1 x1 +2.3,y2 =1.1 x2 +2.4,y3 =1.1 x3 +4.6,and the Pa-ET CO2 was 3.7-8.7 mm Hg. There was no significant difference between PaCO2 and PET CO2 at T1-T3 .Conclusion Whenever in prone position or supine position,PET CO2 and PaCO2 have significant correlation in prone position and supine position.The overall range of Pa-ET CO2 is 3.7-8.7 mm Hg,and the PET CO2 can be as indica-tor to estimate PaCO2 in prone position.