Nonventilatory factors associated with get down the level of PaCO2 determine in patients with hypercapnic respiratory failure

This study was designed to identify the factors other than ventilator affecting the success of non-invasive mechanical ventilation in patients admitted to the intensive care unit with hypercapnic respiratory failure. Forty-one patients admitted to Intensive Care Unit of Chest Diseases of Gazi University Faculty of Medicine with hypercapnic respiratory failure were included in this prospective cohort study which took place between January 2010-November 2012. These patients were followed up for at least 96 hours. Patients with 10 mmHg and more decline in the PaCO2 in the first 72 hours were considered as successful (Group 1) and patients without this decline were accepted as unsuccessful (Group 2). The effects of age, APACHE II score, markers of infection, bronchospasm, heart failure, thyroid function and dead space respiration (VD / VT) were studied on the PaCO2 decrease in patients treated with noninvasive mechanical ventilation. Twenty-eight of the 41 patients were included in group 1, 13 patients were included in group 2. There was no significant difference in ventilatory parameters between two groups (p> 0.05). Patients who are successful were younger (p=0.048). The initial PaCO2 levels (p <0.0001), free T3 value (p=0.045) and 78ejection fraction (0.004) of these patients were higher. The first day (p = 0.043), the second day (p=0.039), and the third day (p=0.015) dead spaces respiration values were lower. Stable period (p=0.013), the first day (p =0.017), and the second day (p=0.025) % predicted FEV1 values and stable period (p=0.002), third day (p=0.046) and fourth day (p=0.017) % FEV1/FVC ratios were lower. In unsuccesful group, the first day (p=0.014) and the third day (p=0.031) CRP levels of patients were higher. Among the predictors of the success of the noninvasive mechanical ventilation; initial PaCO2 (OR: 1.59, 95% CI:1.1-2.3, p=0.014), fT3 (OR: 12, 95% CI:1.51-101, p=0.019) and VD / VT (OR: 1.23, 95% CI:1.01-1.52, p=0.048) values were found to be independent risk factors. As a results of this study we concluded that when the noninvasive mechanical ventilation treatment response can not be achieved in patients with hypercapnic respiratory failure; revision of the factors cause the dead space ventilation, the thyroid function and bronchodilator therapy of patients may be useful.