Background: Chronic obstructive pulmonary disease (COPD) is estimated to affect 10% of the population worldwide and is an important cause of mortality and morbidity. Traditional spirometric measurements such as FEV1 correlate poorly with exercise tolerance and exertional dyspnea that is associated with lung hyperinflation which can be measured by lung volume study. This research identified the presence of hyperinflation and their association even with mild stage and among those with increasing levels of COPD severity.
Method: This was a prospective cohort analytic study among COPD patients diagnosed by pulmonary function test with post-bronchodilator study FEV1/FVC ratio of < 0.70, consistent with airflow obstruction. Lung volume study was done among those who do not have lung volume study. An analysis of variance were used for the association of TLC, RV and RV/TLC ratio on the different levels of COPD severity based on GOLD criteria. A p- value of ≤ 0.05 was considered significant.
Results: Seventy-four patients were included in the study. Fifty-nine patients (80%) were males and 15 (20%) were females. The mean age of the study population was 62 years old with mean height of 160.01 ± 8.4 cm and weight of 61.43 ± 15.8 kg. Majority of the patients (93 %) were smoker, with mean average pack-year-smoker of 30.93 ± 22.1 pack-year. Five patients (7%) who have no smoking history were majority males (4 males and 1 female). The mean FEV1 was 52 % predicted in the post-bronchodilator study. Most of the patients were at GOLD 2 with 33 patients (45%), followed by GOLD 3 with 30 patients ( 40%), then GOLD 4 with 6 patients (8%) and GOLD 1 with 5 patients (7%). Lung volume parameters such as TLC and RV across all stages did not show good association with COPD severity. What was observed was as COPD severity increases, there was also an increasing RV/TLC ratio. However, looking at the changes between one category to the next, the change in RV/TLC was significantly increased between GOLD 1 and 3 (p-value of 0.043) and GOLD 1 and 4 only (p-value of 0.008).
Conclusion: In conclusion, RV/TLC ratio can serve as a good objective parameter for hyperinflation where the ratio increases in direct association with increasing COPD severity. This association is more significantly noted when COPD patients are in GOLD 3 and 4 category.