Can optimal use of spirometry have a positive impact on the progression of chronic obstructive pulmonary disease?

Chronic obstructive pulmonary disease (COPD) is a progressive condition characterized by airflow limitation.[1] The progression of COPD is often accompanied by periods of increasing symptoms, such as dyspnea, cough, and sputum production, known as exacerbations. As per several longitudinal cohort studies, the mean frequency of exacerbation in COPD is approximately two episodes per year,[23] 10% of these episodes require hospitalization and half of the patients require re-hospitalization within 6 months. The frequency of exacerbation is an important outcome parameter in COPD,[4] as exacerbations are associated with increased mortality[56] and significant impairment of health-related quality of life (HRQL).[7-9] The lung function impairment that occurs due to each exacerbation may not return to baseline.[210] Moreover, expenditures incurred in the treatment of exacerbations account for more than 50% of the total direct medical cost of COPD.[1112] Exacerbations cause a tremendous financial burden both on an individual and the whole society as it leads to unscheduled doctor visits, additional treatment with antibiotics or corticosteroids and admission to hospital.[1314] There has been an increasing interest in evolving various new strategies to prevent exacerbations of COPD. Although pharmacotherapy, vaccination, pulmonary rehabilitation, and smoking cessation are few of the very important strategies to prevent acute exacerbations of COPD, preventing progression of COPD appears to be an equally promising strategy to reduce the frequency of exacerbations. Looking to the fact that the frequency of exacerbation increases with decreasing lung functions,[15-17] preventing progression of COPD appears to be one of the most crucial strategies to reduce the frequency of acute exacerbations. If COPD is diagnosed early enough, it is possible to slow down or even stop the further progression of the disease process. Optimal use of spirometry in clinical practice can help detecting COPD in its less advanced (mild or moderate) stages. Early diagnosis followed by timely initiation of pharmacotherapy and nonpharmacologic interventions, can help preventing further progression of the disease and minimizing the pool of patients with advanced (severe and very severe) COPD in the community.

Optimization of pharmacotherapy, especially inhaled medicines has received maximum attention as a strategy to prevent acute exacerbations. The results of TORCH study[18] have shown 25% reduction in exacerbations with combinations of inhaled corticosteroids (ICS) and long-acting beta-agonists (LABA). In both the studies by Calverley et al.[19] and Szafranski et al.,[20] there was a 24% reduction in exacerbations with the combination of ICS and LABA. UPLIFT study[21] has proven that treatment with tiotropium leads to a reduction in the frequency of exacerbations by 14%. Another important strategy to prevent exacerbations is vaccination. The data from Cochrane systematic review has provided substantial support to the value of influenza vaccination for preventing exacerbations of COPD.[22] Benefits of pulmonary rehabilitation are well established[23] in terms of improvement in exercise capacity and quality of life.

Although pharmacotherapy reduces frequency of exacerbations significantly, it has no positive impact on the survival rate and long-term decline in the lung functions. Diagnosing COPD early by the optimal use of spirometry, can reduce the frequency of exacerbations, which are more frequent with the severe impairment in the lung functions. There is a well-established relationship between degree of airflow obstruction (FEV1%) and the annual exacerbation frequency. Correlation between annual exacerbation frequency and the four different COPD severity stages as per the GOLD classification is established very well now.[24] In a study by Andersson et al.,[25] exacerbation frequency was found to be directly proportional to the severity of lung function impairment, that is, frequency of 0.67 for mild, 0.70 for moderate, 1.06 for severe, and 2.56 for very severe COPD. Vestbo et al.[24] has reported exacerbation frequency below 1.0 for patients with FEV1% above 50% and exacerbation frequency was found to be between 1.0 and 1.5 in those with FEV1% between 40% and 50%. A study by Burge et al.[17] showed exacerbation frequency of 2.6 and 1.2 in patients with FEV1% below 45% and above 55%, respectively. Observations derived from the ISOLD and UPLIFT[21] studies indicate that the frequency of acute exacerbations tends to increase as the severity of the underlying COPD increases. Those patients with lower FEV1% exacerbate more in comparison to those whose lung functions are not very much compromised.

In the view of all these evidences, it can be postulated that diagnosing COPD in its less-advanced (mild or moderate) stages can help reducing frequency of exacerbations by arresting or slowing down its further progression. Catching them early is the only strategy that could prevent further progression and hence could reduce the incidence of acute exacerbations. In comparison with other diagnostic tools (ie, clinical evaluation, radiological pictures, arterial blood gas analysis) spirometry has a greater potential of detecting a COPD patient in early stages (ie, mild and moderate stages as per the GOLD guidelines). Diagnosis based on just symptoms is less likely to help detecting COPD in the early stage as by the time patients develop dyspnea they already are in the severe stage of COPD as they tend to lose 50% of their lung functions (FEV1 < 50%) by then. Radiology detects hyperinflation and arterial blood gas analysis detects hypoxemia again in the severe stage of COPD. Thus, none of these tools (clinical examination, chest X-ray and ABG) can help diagnosing COPD in its less advanced stages. Moreover, as GOLD guidelines recommend use of ICS only in severe and very severe COPD patients, early diagnosis can help minimizing the use of inhaled corticosteroid, which are reported[18] to increase the incidence of pneumonias and hence admission rate too. Early diagnosis followed by early smoking cessation advice can help reducing exacerbation frequency as quitting smoking either halts or slows down the accelerated decline in the lung functions.[26]

Optimal use of spirometry in clinical practice can prevent progression of COPD by detecting it in the early stage. Halting or slowing down the progression of COPD can help minimizing the pool of patients with advanced (severe and very severe) COPD in the community, which eventually would reduce the frequency of acute exacerbations and the cost of treatment. Progressing COPD is detrimental to the good health status of the COPD patients. Sensitizing clinician about the optimal use of spirometry in their clinical practice could help preventing progression of the disease and improving health status of the patients.