Bronchodilation in COPD: beyond FEV1-the effect of albuterol on resistive and reactive properties of the respiratory system.
OBJECTIVE
Current debates on the bronchodilator response in COPD patients and whether the variation in FEV1 can be considered as an indicator of complete reversibility in such patients motivated us to conduct this study. The objective of the study was to determine the effect of albuterol on the resistive and reactive properties of the respiratory system in COPD patients.


METHODS
We evaluated 70 patients with COPD, divided into two groups based on spirometry findings: bronchodilator (BD)-negative (n = 39); and BD-positive (n = 31). We used the forced oscillation technique (FOT) to evaluate the following parameters: resistance at the intercept (R0), associated with the total resistance of the respiratory system; mean resistance (Rm), associated with central airway resistance; dynamic compliance (Cdyn); and the slope of resistance (S) and mean reactance (Xm), both of which are associated with the homogeneity of the respiratory system.


RESULTS
The use of albuterol resulted in significant reductions in (p < 0.00002) and Rm (p < 0.0002). There were also significant increases in S (p < 0.0001), Cdyn (p < 0.0001) R0 and Xm (p < 0.00004).These modifications occurred in both groups, the changes in FOT parameters being greater than those observed for spirometric parameters.


CONCLUSIONS
The use of albuterol improved the resistive and reactive properties of the respiratory system of the COPD patients under study. These changes occurred regardless of the FEV1-based classification, thereby indicating that the use of this parameter in isolation might not suffice to identify the physiological effects involved.
Costa
Gerusa Marítimo da
GM
Rio de Janeiro State University, Rio de Janeiro, Brazil.
Faria
Alvaro Camilo Dias
AC
Di Mango
Ana Maria Gonçalves Tavares
AM
Lopes
Agnaldo José
AJ
Jansen
José Manoel
JM
Melo
Pedro Lopes de
PL
D000368:Aged; D000403:Airway Resistance / Q000187:drug effects*; D000420:Albuterol / Q000627:therapeutic use*; D001993:Bronchodilator Agents / Q000627:therapeutic use*; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects*; D006801:Humans; D008297:Male; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy*; D013147:Spirometry; D018709:Statistics, Nonparametric
D001993:Bronchodilator Agents; D000420:Albuterol