Continuous positive airway pressure facilitates spontaneous breathing in weaning chronic obstructive pulmonary disease patients by improving breathing pattern and gas exchange.
OBJECTIVE
To elucidate the effects of continuous positive airway pressure (CPAP) on breathing pattern, gas exchange and the ability to sustain spontaneous breathing (SB) in chronic obstructive pulmonary disease (COPD) patients with dynamic hyperinflation.


METHODS
Prospective study with two randomised trials of SB without and with CPAP in each patient.


METHODS
Medical intensive care units (ICUs) in two university hospitals.


METHODS
Nine dynamically hyperinflated, intubated COPD patients recuperating from acute exacerbation.


METHODS
One SB trial with CPAP (5-7.5 cmH2O), one without (control) in each patient.


METHODS
airway opening pressure, gas flow and thus breathing pattern, oxygen uptake, carbon dioxide excretion, arterial blood gases, dyspnoea and respiratory drive (P100).


RESULTS
With CPAP, intrinsic positive end-expiratory pressure (PEEPi) fell from 11.4 to 6.3 cm H2O (p < 0.05). Eight patients sustained SB with CPAP for the maximum time planned (30 min), one failed after 18 min. In contrast, only four patients successfully completed the control trial, the others failing after 5-18 min (p < 0.05). Dyspnoea-gauged on a visual analogue scale by five patients--was less severe or occurred later with CPAP. Breathing with CPAP tended to be slower (18.9 vs 22.2 min(-1), p < 0.05) and deeper (tidal volume 370 vs 323 ml). At the end of the control run, PaCO2 was higher (60 vs 55 mmHg, p < 0.05) and still rising while being stable at the end of the CPAP trial.


CONCLUSIONS
CPAP helps severely ill COPD patients sustain SB. Apparently it does so by promoting slower, deeper breathing and thus facilitating carbon dioxide elimination.
Reissmann
H K
HK
Department of Anaesthesiology, University Hospital Eppendorf, Hamburg, Germany. reissmann@uke.uni-hamburg.de
Ranieri
V M
VM
Goldberg
P
P
Gottfried
S B
SB
D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D000403:Airway Resistance; D001784:Blood Gas Analysis; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000150:complications / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D012126:Respiratory Dead Space; D015656:Respiratory Mechanics; D012720:Severity of Illness Index; D013990:Tidal Volume; D013997:Time Factors; D015300:Ventilator Weaning / Q000379:methods*