Functional respiratory effects of noninvasive ventilation in acute hypercapnic patients with chronic obstructive pulmonary disease

Abstract

Introduction: Noninvasive ventilation (NIV) is useful for improving oxygenation, decreasing hypercapnia, and avoiding invasive mechanical ventilation in patients with chronic obstructive pulmonary disease (COPD) exacerbations and acute respiratory failure [1,2]. During the hospitalization, the treatment intensity is quite variable on the basis of the patient's clinical condition. Often, after the acute phase, patients need only periods of NIV followed by oxygenotherapy. NIV reduces the work of breathing and probably improves the respiratory muscular strength even when the ventilation is ended [3]. The aim of this study is to evaluate this effect in COPD submiTed to NIV. Methods: We studied 10 patients (seven male; three female; age 74.2 ± 5.3 years) admiTed to our hospital with a COPD exacerbation and acute respiratory failure. After a period of clinical stabilization, patients underwent spirometry and arterial blood gas as basal examinations. For each patient, NIV was applied for 2 hours and than spirometry and arterial blood gas were repeated. Results: are presented as mean ± SD. Data were evaluated by paired t test and a value of P <0.05 was taken as statistically significant. Results: At the end of NIV, the forced ventilatory capacity (FVC) and the forced expiratory volume at the first second (FEV1)/FVC ratio were significantly increased compared with the basal value: FVC 47.9 ± 11.0% basal, 55.3 ± 15.6% after NIV, P = 0.02; FEV1/FVC 68.5 ± 17.1 basal, 59.3 ± 15.2 after NIV, P = 0.007. Compared with the basal value, arterial carbon dioxide pCOT2was significantly decreased: 68.0 ± 2.5 mmHg (basal), 55.3 ± 4.5 mmHg (after NIV), P <0.02; and arterial oxygen was increased: 50.0 ± 14.2 mmHg (basal), 56.3 ± 15.3 mmHg (after NIV). Conclusions: The results of this study demonstrate that, in COPD exacerbation, NIV determines a decrease of the pulmonary hyperinflaction. This effect could improve the clinical status and the work of breathing.