Volume 6 | Issue 9 | 2020 | Respiratory Medicine
COPD – 2020 a paradigm shift AUTHORS: Dr Ciara Ottewill, SpR in Respiratory Medicine; and Prof Stephen J Lane, Consultant Respiratory Physician, Department of Respiratory Medicine, Tallaght University Hospital Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality worldwide. Though classically it is associated with smoking, it is estimated that up to 20-45 per cent of those with COPD worldwide are non-smokers. The majority of studies to date focus on latestage disease, however, it is becoming increasingly clear that a focus on primary prevention of the disease is needed. Early detection of those with pre-COPD and early COPD should become priorities going forward.
smokers, in contrast, appears to be relatively static, with an estimated 40-50 per cent of smokers developing the disease. Genetic factors, including α-1-antitrypsin deficiency, are also known to contribute to the disease.
COPD trends in Ireland in 2020 Ireland has one of the highest rates of hospitalisation for COPD in the OECD, at approximately 400 admissions per 100,000 population, which is among the highest rates of hospital admissions for COPD globally. Though over the past 15 years there has been a notable international
Background COPD is the third common cause of death worldwide,1 and is estimated to affect up to 12 per cent of the world population. It is the cause of over three million deaths annually, far surpassing the current annual death rate from Covid-19 (which at time of publication was estimated by the World Health Organisation (WHO) to have surpassed one million in its first 10 months). It is among the most common causes of death in Ireland, surpassed only by cardiovascular disease and cancers. The OECD estimates that COPD attributes to approximately 40 per cent of respiratory mortality in Ireland. The prevalence of COPD appears to be increasing globally, in particular in countries including China and India. This increase appears to be primarily in non-smokers. It is estimated that approximately 25 per cent of the Irish population diagnosed with COPD are non-smokers. Prevalence of non-smokers with the diseases varies globally, with 45 per cent of patients in South Africa having never smoked. The reasons for non-smoking related COPD are becoming clearer and can be related to intrauterine factors, early life factors, exposure to inefficient combustion of biomass fuels in poorly ventilated houses, and second hand smoke for example. Prevalence of COPD in
22
Ireland has one of the highest rates of hospitalisation for COPD in the OECD, at approximately 400 admissions per 100,000 population, which is among the highest rates of hospital admissions for COPD globally
decrease in mortality secondary to cancer and cardiovascular disease, including myocardial infarction, mortality from COPD remains high. COPD accounts for the primary diagnosis in over 1,500 deaths annually in Ireland, which is second only to lung cancer in causes of death from respiratory disease, as is outlined in the 2018 Respiratory Health of the Nation document from the Irish Thoracic Society. COPD is more prevalent in lower socioeconomic groups within Ireland.
Pathophysiology Exhalatory airflow obstruction (afterload) and hyperinflation (preload)
There are two key pathological changes in COPD, ie, chronic bronchitis and emphysema. Chronic bronchitis and emphysema results in either anatomical or functional airflow obstruction. This obstruction occurs throughout the entire length of the non cartilaginous, smooth muscle containing tracheobronchial tree. The obstruction occurs predominantly during exhalation as the airways are naturally more narrowed then than during inhalation. Thus there is increased ‘afterload’ to the process of exhalation making it more difficult and lengthy for patients to exhale at rest and during exercise. Emphysema, in addition to exhalatory obstruction, results in increased lung compliance because of parenchymal destruction. Therefore in the ‘tug of war’ between the chest wall and lung parenchyma maintained by the pleura, the outward forces of the chest wall will overcome the inward forces of the damaged elastic lung resulting in an increase of volume trapped in the lung at the end of quiet exhalation or the FRC (functional residual capacity). This trapped volume results in significant ‘preload’ to the patients with predominant emphysema subtype. Ultimately the lung becomes hyperinflated and ‘barrel-like’ as the chest wall creeps up over the trachea. COPD patients find themselves ‘breath stacking’ because of this air trapping, which contributes substantially to breathlessness at rest and on exertion. Powerful treatments for COPD, including LAMAs (long-acting muscarinic antagonists) and LABAs (long-acting beta agonists), work by bronchodilating (as measured by an improvement in FEV1) the increased afterload of exhalatory airflow obstruction. In addition, along with lung volume reduction surgery (LVRS) and endobronchial valve therapy (EBV), they act by deflating the preload caused by the hyperinflated FRC (as measured by increasing the VC (vital capacity), which can often be significant).
