Effects of sedation on respiratory mechanic dynamics and oxygen metabolism in patients with mechanical ventilation

Objective: To investigate the effect of sedation on respiratory mechanic dynamics, intrapulmonary shunt fraction, oxygen metabolism in patients with mechanical ventilation. Method: Sixty patients with mechanical ventilation were divided randomly into control group and sedation group. Propofal was administered to patients, whose ramsay scores were kept at III or IV levels, in sedation group while the equal amount of normal saline was given in control group. Mixed venous blood and arterial blood samples were taken for blood gas analysis in both groups before and at 2 hours after administration. Heart rate, blood pressure, breathing rate and airway resistance all were recorded at the same time. Results: There were no significant differences in oxygenation index, blood pressure, blood lactic acid, total lung static compliance and intrapulmonary shunt fraction between two groups before and after administration. Heart rate, respiratory rate, oxygen uptake and airway resistance of patients in sedation group were lower than those in control group, and partial pressure of oxygen in mixed venous blood of patients in sedation group were higher than those in control group. These differences were statistically significant. Conclusions: Sedation can decrease oxygen uptake and airway resistance of patients with mechanical ventilation. However, no alteration in the oxygenation index, total lung static compliance and intrapulmonic shunt ratio can be observed.