Bronchodilator response in residual volume in irreversible airway obstruction.
BACKGROUND
Although airway obstruction, as defined by improvement of forced expiratory volume in one second (FEV1) and/or forced vital capacity (FVC), is irreversible in patients with COPD, they clearly seem to benefit from treatment with inhaled bronchodilators.


OBJECTIVE
To assess the response pattern of residual volume (RV) compared to FEV1 after bronchodilation in patients with reversible and irreversible airway obstruction.


METHODS
Changes in static lung volumes were compared with improvement in dynamic lung volumes in 396 consecutive patients undergoing reversibility testing with repeat bodyplethysmography. Reversibility was defined as improvement of FEV1 >200 ml and >12% after inhalation of fenoterol hydrobromide.


RESULTS
Irreversibility was found in 297 out of 396 patients with airway obstruction. Except for total lung capacity (TLC), all parameters (residual volume [RV], vital capacity [VC], forced inspiratory vital capacity [IVC], forced vital capacity [FVC], forced expiratory volume in one second [FEV1] and the FEV1/VC ratio) showed statistically significant changes after bronchodilation in 396 patients. The multiple linear regression model adjusted for age, sex and BMI showed a non-linear relationship between DeltaFEV1 or DeltaVC compared to DeltaRV after bronchodilation. If the increase in DeltaFEV1 is lower than 0.1 L, DeltaRV remains constant. However, if the increase in DeltaFEV1 is more than 0.1 L, DeltaRV decreases too. The same is found at an increase in VC of 0.3 L.


CONCLUSIONS
In summary, in patients with irreversible airway obstruction DeltaRV cannot be predicted by DeltaFEV1 or DeltaVC after bronchodilation. Therefore, spirometric assessment should be complemented by bodyplethysmography.
Balestra
Anna-Maria
AM
Pneumology, University Hospital Basel, Switzerland. jleuppi@uhbs.ch
Bingisser
Roland B
RB
Chhajed
Prashant N
PN
Tamm
Michael
M
Leuppi
Jörg D
JD
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D001993:Bronchodilator Agents / Q000627:therapeutic use*; D005260:Female; D005280:Fenoterol / Q000627:therapeutic use*; D005541:Forced Expiratory Volume / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D010993:Plethysmography, Whole Body; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000188:drug therapy*; D012115:Residual Volume / Q000187:drug effects*; D012737:Sex Factors; D012815:Signal Processing, Computer-Assisted; D014109:Total Lung Capacity / Q000187:drug effects; D016896:Treatment Outcome; D014797:Vital Capacity / Q000187:drug effects
D001993:Bronchodilator Agents; D005280:Fenoterol