[Non-invasive mechanical ventilation in patients with severe stable COPD].
BACKGROUND
The benefits of non-invasive mechanical ventilation (NIMV) in hypercapnic patients with severe stable COPD remain controversial mainly due to their unknown mechanisms.


OBJECTIVE
To assess the clinical and physiological benefits of a 3 weeks period of intermittent NIMV and their underlying mechanisms in COPD patients.


METHODS
Twelve patients (10 male) prospectively recruited (age 65 +/- 3 years, FEV1 27 +/- 2% predicted, PaO2 46 +/- 2 mmHg, PaCO2 55 +/- 2 mmHg) were submitted to NIMV using a commercially available system (BiPAP) 3 h a day, 5 days a week for 3 weeks. Arterial blood gases, 6 min walking distance, dyspnea (Mahler's scale), breathing pattern, PIMax, ventilatory drive (P0.1) and the impedance of the respiratory system (P0.1/V1/T1) were measured before and after NIMV.


RESULTS
A significant improvement in PaO2, PaCO2, PIMax, dyspnea and exercise capacity was observed in addition to a trend for VT to increase and for respiratory rate (RR) to decrease. The impedance of the respiratory system showed a significant reduction. Ventilatory drive, normalized for PaCO2 levels, did not change. Improvement in PaCO2 was related to an increase in Vp whereas a significant association between the reduction in RR and the fall in respiratory system impedance was also found.


CONCLUSIONS
Our study supports previous data demonstrating that NIMV improves clinical and physiologic parameters in advanced stable COPD and suggest that the underlying mechanism is a reduction in the inspiratory load. A randomized clinical trial is needed to confirm that this mechanism is operative.
Díaz
O
O
Departamento de Enfermedades Respiratorias, Universidad Católica de Chile. odiaz@med.puc.cl
Ramos
J
J
Gallardo
J
J
Torrealba
B
B
Lisboa
C
C
D000368:Aged; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000628:therapy; D008173:Lung Diseases, Obstructive / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010342:Patient Acceptance of Health Care; D011446:Prospective Studies; D013997:Time Factors; D012122:Ventilators, Mechanical
D010100:Oxygen