The effect of dead space fraction on weaning from mechanical ventilation in Copd Patients

Background: Chronic Obstructive Pulmonary Disease (COPD) is a common disease that tends to occur worldwide. Physiologically, COPD represents a disruption in ventilation and in the exchange of gases in the lungs. Laboratory tests indicate elevated CO2 level, gradual reduction of the levels of oxygen and pH in arterial blood, and a consequent rise in the Dead Space Fraction (DSF) of the lungs. Objective: Patients with COPD represent a large portion of those artificially ventilated in the Intensive Care Unit (ICU). In an attempt to develop a prognostic tool for the length of treatment, we compared the proportion of DSF to the length of artificial respiration. Methods: This study included 49 patients receiving ventilation due to exacerbation of COPD. Each patient's arterial blood gases (ABG) were measured upon admission. PECO2 was tested using a Datex S/5 instrument. Subsequently, DSF was calculated using the Bohr equation. Statistical data was analyzed using the SPSS-11 program. Results: Patients included in the study were respirated from 5 to 161 hours (average 4047). In addition to ABG measurements, PECO2 levels were measured and DSF calculated for each patient. DSF values varied from 0.22 to 0.74 (average 0.119 0.489). No correlation was found between DSF and length of artificial respiration. These findings do not contribute to the evaluation of the patient's condition nor do they enable us to predict the length of treatment necessary. Conclusion: Evaluation of Dead Space Fraction does not provide a factor in estimating the length of treatment for patients with acute respiratory failure due to Chronic Obstructive Pulmonary Disease (COPD).