Mechanical determinants of early acute ventilatory failure in COPD patients: a physiologic study.
OBJECTIVE
The purpose of this study is to investigate the respiratory mechanics, breathing pattern, and pressure-generating capacity of respiratory muscles during the early phases of an acute exacerbation of COPD.


METHODS
Prospective study.


METHODS
Division of Emergency Critical Care and Chronic Ventilator Unit.


METHODS
A total of 24 COPD patients: nine patients requiring ventilatory support because of acute respiratory acidosis due to COPD exacerbation (NPPV group, pH 7.28 +/- 0.02); seven patients successfully managed with medical therapy only (SB group, pH 7.39 +/- 0.04); eight clinically stable, long term mechanically ventilated, COPD patients (IPPV group).


METHODS
Respiratory mechanics during a period of unsupported breathing.


RESULTS
A rapid shallow breathing, in the presence of a high drive to breath and a high diaphragmatic tension-time index (TT(di)), was found in NPPV and IPPV groups compared to the SB group (f/V (T) ratio: 118 +/- 43 and 137 +/- 65, respectively, versus 37 +/- 12 breaths/min/L; P (0.1): 5.0 +/- 1.0 and 5.4 +/- 1.4, respectively, versus 2.2 +/- 0.2 cmH(2)O, TT(di): 0.168 +/- 0.035 and 0.161 +/- 0.039, respectively, versus 0.057 +/- 0.033); at variance, PEEPi(dyn) was greater in IPPV compared to the other two groups. A significant relationship was observed between TT(di) ratio and f/V (T) (Rho 0.756).


CONCLUSIONS
During the early phases of an acute exacerbation, patients with COPD and acute respiratory failure had an imbalance between the decreased capacity of the respiratory muscles to generate pressure and the increased respiratory load. This imbalance was similar to that recorded in patients with COPD and chronic ventilatory failure. In both groups, the imbalance was associated with rapid shallow breathing. Among the mechanical constraints to ventilation, only PEEPi,dyn was different between acute and chronic patients with ventilatory failure.
Purro
Andrea
A
Emergency Department, Gradenigo Hospital, Turin, Italy. andrea.purro@h-gradenigo.it
Appendini
Lorenzo
L
Polillo
Carolina
C
Musso
Giovanni
G
Taliano
Claudio
C
Mecca
Fabio
F
Colombo
Roberto
R
Carbone
Giorgio
G
D000142:Acidosis, Respiratory / Q000175:diagnosis / Q000209:etiology / Q000517:prevention & control; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D011175:Positive-Pressure Respiration; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000453:epidemiology*; D012121:Respiration, Artificial / Q000295:instrumentation*; D012131:Respiratory Insufficiency / Q000503:physiopathology / Q000534:rehabilitation*; D015656:Respiratory Mechanics; D012132:Respiratory Muscles / Q000503:physiopathology