Module 4: Chronic Obstructive Pulmonary Disease and Occupations - Global Burden of COPD.

GLOBAL BURDEN OF COPD:

Chronic Obstructive Pulmonary Disease, (COPD) is:

DEFINITION OF COPD:

Chronic obstructive pulmonary disease (COPD) (Also know as COAD or simply OLD) includes the conditions known as chronic bronchitis and emphysema. It is a disease state resulting predominantly from smoking tobacco and is characterised by airflow obstruction which is generally progressive. It may be accompanied by hyper-reactive airways, and the airway obstruction may be partially reversible.

Description of COPD:

COPD can therefore be thought of as a combination of three conditions, which in any given case may be present in varying degrees of severity.

Chronic bronchitis:

Chronic bronchitis refers to the presence of a chronic productive cough for at least 3 months of the year in two or more successive years in the absence of other recognised causes of chronic cough.

The condition is caused by mucous hypersecretion consequent on mucous gland hyperplasia within chronically inflamed airways.

Emphysema:

Emphysema is a pathological diagnosis describing permanent abnormal enlargement of the airspaces distal to the terminal bronchioles, accompanied by destruction of alveolar walls.

The consequences of emphysema include a reduced surface area for gaseous exchange and loss of lung elasticity, resulting in dynamic collapse of conducting airways and hyperinflation of the lung.

Airflow obstruction:

Since COPD is a somewhat complex combination of conditions it can be interpreted differently according to context. For example to the clinician COPD is a diagnostic rubric meant to include chronic bronchitis, emphysema and irreversible airflow limitation, or as a continuum where most theraputic modalities are directed at reversible airflow obstruction, or even as a hopeless and uninteresting self-inflicted disease.

To the public health specialist it is often seen simply as a condition suffered by smokers over the age of 40.

Spirometry in COPD:

Spirometry is essential for the detection, diagnosis, assessment and management of patients with COPD and should be performed by adequately trained persons using a spirometer that is of the approved standard, which is calibrated regularly.

Peak expiratory flow rate measurements while helpful in asthma are unsuitable for assessment of COPD.

Why perform spirometry?
  1. Detection of airflow obstruction.
  2. Assessment of degree of reversibility.
  3. Monitoring of a trial of systemic corticosteroids.
  4. Monitoring disease progression.

Staging severity of COPD:

In recent efforts international efforts have been made to increase the focus on COPD, support efforts for its prevention and achieve consensus on its management.

One such effort has been GOLD - the Global Initiative on Obstructive Lung Disease. This initiative has provided the staging of COPD severity shown in the next Table below. This staging is primarily based on FEV1 as % of predicted.

  FEV1 (%pred) Symptoms Comments
Stage I (mild) ³ 50% Mild effort-related dyspnoea Good quality of life.. Common Little morbidity. No hypoxaemia.
Stage II (moderate) ³ £ 35% Continuous dyspnoea which interferes with lifestyle Considerable morbidity
Stage III (severe) < 35% Dyspnoea limits activities of daily living Respiratory failure and/or cor pulmonale common. High Mortality.

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Postgraduate Diploma in Occupational Health (DOH) - Modules 3 – 5: Occupational Medicine & Toxicology by Prof Rodney Ehrlich & Prof Mohamed Jeebhay is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
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