Effects of airway obstruction on albuterol-mediated variations in the resistive and elastic properties of the respiratory system of patients with asthma.
OBJECTIVE
To investigate the effects of airway obstruction on albuterol-mediated variations in the resistive and elastic properties of the respiratory system of adult patients with asthma.


METHODS
This study comprised 24 healthy controls and 69 patients with asthma, all of whom were nonsmokers. The patients were divided into three groups according to the severity of airway obstruction (mild, moderate or severe). Each of the three groups was divided into two subgroups according to the bronchodilator response (BR): positive (BR+) or negative (BR(-)). Airway obstruction was determined by means of spirometry, and the resistive and elastic properties were determined by means of the forced oscillation technique. These measurements were conducted before and after albuterol use (300 microg).


RESULTS
The resistance at the intercept (R(0)) presented greater reductions in the groups with higher obstruction. This reduction was more evident in the BR+ subgroups than in the BR(-) subgroups (p < 0.02 and p < 0.03, respectively). There was a significant difference between the control group and the BR+ subgroup with severe obstruction (p < 0.002). The reductions in dynamic elastance (Edyn) were significantly greater in proportion to the degree of obstruction, in the BR(-) subgroups (p < 0.03), and in the BR+ subgroups (p < 0.003). The reductions in Edyn were significantly greater in the BR- subgroup with moderate obstruction (p < 0.008) and in the BR+ subgroup with severe obstruction (p < 0.0005) than in the control group.


CONCLUSIONS
In patients with asthma, increased airway obstruction results in greater reductions in R(0) and Edyn after albuterol use. These reductions are greater among BR+ patients than among BR(-) patients.
Veiga
Juliana
J
Universidade Castelo Branco, Rio de Janeiro, RJ, Brasil.
Lopes
Agnaldo José
AJ
Jansen
José Manoel
JM
de Melo
Pedro Lopes
PL
D000293:Adolescent; D000328:Adult; D000368:Aged; D000402:Airway Obstruction / Q000188:drug therapy* / Q000503:physiopathology; D000403:Airway Resistance / Q000187:drug effects* / Q000502:physiology; D000420:Albuterol / Q000627:therapeutic use*; D000704:Analysis of Variance; D001249:Asthma / Q000188:drug therapy*; D001993:Bronchodilator Agents / Q000627:therapeutic use*; D016022:Case-Control Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012137:Respiratory System / Q000187:drug effects* / Q000503:physiopathology; D013147:Spirometry; D055815:Young Adult
D001993:Bronchodilator Agents; D000420:Albuterol