Supramaximal flows: comparison between asthmatics and patients with chronic obstructive pulmonary disease.
BACKGROUND
The major motive that prompted this study was to investigate whether or not the differences in supramaximal flow (SF) behavior between patients suffering from asthma and patients suffering from chronic obstructive pulmonary disease (COPD) might aid in clarifying the differences in the physiopathology of the two diseases.


OBJECTIVE
The aim of the present study was therefore to compare SFs in asthma and COPD patients with similar degrees of air-flow limitation.


METHODS
Twelve asthmatic patients were individually matched with 12 COPD patients by forced expiratory volume during the first second (FEV(1)) as a percent (±5%) of the reference value (ΔFEV(1)) and by age (±4 years). The subjects performed baseline maximal expiratory flow-volume curves (MEFV) and then repeated the same maneuvers through a valve that occluded the air flow 6 times per second with an open/closed time ratio of 4/1. We then plotted an envelope of the expiration-interrupted curve passing through the SF peaks, measured the increase in flow at 50% of the forced vital capacity between the baseline curve and the envelope curves (ΔVmax(50)), and compared the FEV(1) of the interrupted curve to the FEV(1) obtained from control MEFV curves (ΔFEV(1)).


RESULTS
We found significantly higher values for ΔVmax(50) (p < 0.03) and ΔFEV(1) (p < 0.01) in the asthmatics compared to the COPD patients.


CONCLUSIONS
The differences reported here are best explained by a greater preservation of elastic recoil pressure at a similar degree of air-flow limitation in the asthmatics than in the COPD patients.
Hospital Alejandro Posadas, Buenos Aires, Argentina. alestork@yahoo.com.ar
Alejandra
A
González
Alejandra
A
Fernández
Sergio
S
Guardia
Hernando
H
Sala
D000368:Aged; D000403:Airway Resistance; D001249:Asthma / Q000503:physiopathology*; D004548:Elasticity; D005260:Female; D006801:Humans; D008297:Male; D008449:Maximal Expiratory Flow-Volume Curves; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*