Sir,
Obstructive airway diseases (OAD) are a significant contributing factor to morbidity and mortality in the world.[1] India accounts for 18% of the global population and has an increasing burden of chronic respiratory diseases.[1] Oscillometry has the advantage of being performed at tidal breathing and is also useful in early detection of small airway involvement.[2] It can easily be performed by both paediatric and geriatric populations.[1] Liu et al.[3] in their study, demonstrated that in geriatric group, it had good application in the diagnosis and classification of Chronic obstructive pulmonary disease (COPD). A study by Frantz et al.[4] also concluded that oscillometry had the potential to diagnose COPD earlier than spirometry. Oscillometry has been successfully used in paediatric population to diagnose asthma and predict exacerbations.[5] However, the gold standard for diagnosing OAD is spirometry, though oscillometry has been advocated as an alternative.
We performed a cross-sectional study on patients with asthma and COPD aged older than 18 years attending the respiratory outpatient department or admitted to a tertiary care chest hospital in northern India from Apr 2021 to Apr 2022 to assess the correlation of Forced oscillation technique (FOT) parameters and spirometry parameters. We calculated sample size with threshold probability of α = 0.05(level of significance) and with β level of 0.20 (power of study 80%) and the previously observed correlation coefficient between FOT and spirometry parameters in COPD, ranging from 0.4 to 0.7[6] and in asthma, from 0.4 to 0.5.[7] The sample size n for COPD was 13– 47 and for asthma was 42–45. During the period of study, a total of 45 cases of asthma and 55 cases of COPD were included. We excluded patients who were in exacerbations or were on oxygen support. One hundred patients were divided into two groups of obstructive lung disease (asthma and COPD) based on their medical history, physical examination, Global Initiative for obstructive lung disease (GOLD) and Global initiative for asthma (GINA) guidelines.
Forced oscillation technique (FOT) was performed using the Resmon Pro Full device as per the European Respiratory Society recommendation.[8] Spirometry was done after FOT in the same setting. Spirometry was performed with Jaeger Masterscreen pulmonary function instrument in strict accordance with the American Thoracic Society/European Society of Respiratory Diseases guidelines.[9] The FOT parameters (R5, R19, X5) were compared with those of spirometry parameters (FEV1, FVC, FEV1/FVC).
Amongst 100 patients, there were 47% (n = 47/100) males. The mean age of patients was 54.12 years (ranging from 18 to 83 years). By using Pearson’s correlation coefficient test, P value < 0.05; in COPD patients, FEV1, FEV1%, FVC, FVC% showed significant negative correlation with R5, R19, R5%, R19% and a positive correlation with X5. FEV1/FVC showed significant correlation with R5 and X5. However, correlation with R19 and FEV1/FVC was not statistically significant. In asthma, FEV1, FEV1%, FVC, FVC% showed significant negative correlation with R5, R19, R5%, R19% and a positive correlation with X5. FEV1/FVC showed significant correlation with R5 and X5. However, correlation between R19 and FEV1/FVC was not statistically significant. The correlation between spirometry and FOT parameters is plotted in Figures 1–4.
Figure 1.
Scatter plots of correlation between (a) R5 vs FEV1 (b) R19 vs FEV1 (c) R5% vs FEV1% (d) R19% vs FEV1%
Figure 4.
Scatter plots of correlation between (a) X5 vs FEV1 (b) X5 vs FVC (c) X5 vs FEV1% (d) X5 vs FEV1/FVC%
Figure 2.
Scatter plots of correlation between (a) R5 vs FVC (b) R19 vs FVC (c) R5% vs FVC% (d) R19% vs FVC%
Figure 3.
Scatter plots of correlation between (a) R5 vsFEV1/FVC% (b) R19 vs FEV1/FVC% (c) R5% vs FEV1/FVC% (d) R19% vs FEV1/FVC%
An association between reactance and FEV1 in COPD patients has been shown previously.[10,11] A study by Nikkhah M et al.[7] found a remarkably higher R5 and R20 and also a lower X5 in COPD and asthmatic patients in contrast with the control population. In 2009, Winkler et al.[12] detected 87–94% of asthmatic and COPD patients by using different IOS measurements. The difference between various studies has been attributed to the method of study, which included established COPD and asthmatic patients.
Oscillometry is a good alternative to spirometry, specifically suitable for the young and geriatric subgroups. The main limitation is the paucity of data on reference values. However, these are not limitations of the technique per se and can be overcomed once the technique is implemented widely.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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