To evaluate the correlation of the post bronchodilator IC (% predicted), with other prognostic and severity variables in COPD.
60 stable COPD patients (41 men, 19 women, age= 69 ± 7 years, FEV1/FVC= 48 ± 10%, ) were submitted to spirometry with FVC and SVC maneuvers and 6 minutes walk test (6MWT) before and after albuterol spray (400 mcg). The IC% and other variables were correlated by univariate and multivariate analysis with the 6-minute walk distance post BD, percent predicted (6MWD%). The IC% was correlated with the BODE index and the GOLD staging severity of COPD.
The 6MWD% did not differ between genders and didn’t correlate with age. Patients on long-term oxygen therapy had shorter 6MWD% (46±21% vs 95±17% patients without oxygen, p=0,001). The number of exacerbations per year correlates with the 6MWD% (p=0,05). The number of drugs and co-morbidities didn’t correlate with the 6MWD%. The 6MWD% was linearly correlated with the FVC% after BD (r=0,46 p<0,001), FEV1% (r=0,57, p< 0,001), CI% (r=0,68, p<0,001), Borg after 6 minutes (r=-0,62, p= <0,001), SpO2 (r=0,36, p= 0,005) and FEV1/FVC% (r=0,56, p<0,001). In a stepwise forward logistic regression analysis, the strongest association with the 6MWD% was: IC % (r2=0,44), long term oxygen use (r2 = 0,62) and Borg 6 min (r2 = 0,65). IC ≤ 70% was observed in 11/23 patients (47%) in GOLD stages 3 or 4 vs. 6/37 patients (16%) in GOLD stages 1 or 2 (x2=6,98, p=0,008). IC ≤ 70% was observed in 8/17 patients (47%) with BODE index 3 or 4 compared to 9/43 patients in BODE 1 or 2 (20%) (x2=4,096, p=0,043).
The IC % postBD is the better functional predictor of the 6-minute walk distance and has a strong association with other severity variables in COPD.
In COPD the Inspiratory Capacity (IC) reflects the lung hyperinflation and correlates with the 6MWD%, BODE index and GOLD. This study considered the IC% measured by spirometry, a simple and usual method.
Clarice Freitas-Santos, None.