Respiratory Medicine is the medical specialty concerned with the respiratory system, including the lungs, airways, pleura, respiratory muscles and mechanisms responsible for ventilation and gas exchange. It addresses diseases such as asthma, chronic obstructive pulmonary disease, pneumonia, interstitial lung diseases, bronchiectasis, pulmonary vascular disorders, sleep-related breathing disorders and lung cancer, as well as acute and chronic respiratory failure.
Effective respiration requires coordinated movement of air into and out of the lungs, diffusion of oxygen and carbon dioxide across the alveolar-capillary membrane, adequate pulmonary blood flow and transport of gases through the circulation. Respiratory Medicine therefore overlaps with cardiovascular medicine, infectious disease, oncology, intensive care, occupational medicine, sleep medicine and immunology. Symptoms such as breathlessness, cough, wheeze, chest discomfort and sputum production can result from pulmonary, cardiac, neurological, muscular or systemic disorders, making differential diagnosis essential.
Ventilation and gas exchange depend on the mechanical properties of the lungs and chest wall, airway resistance, respiratory muscle activity and matching between ventilation and pulmonary perfusion. Air enters the conducting airways before reaching the respiratory bronchioles and alveoli, where oxygen and carbon dioxide diffuse across a thin biological barrier. Surfactant produced by alveolar type II cells reduces surface tension and helps maintain alveolar stability.
Haemoglobin carries most oxygen in blood, while carbon dioxide is transported in several forms, principally as bicarbonate. Ventilation-perfusion matching is essential because regions receiving air and blood in disproportionate amounts can reduce effective gas exchange. The respiratory system is regulated by neural networks in the brainstem and by chemoreceptors that respond to carbon dioxide, oxygen and acid-base changes.
Asthma is a chronic inflammatory airway disorder characterised by variable respiratory symptoms and variable expiratory airflow limitation. Airway hyperresponsiveness, inflammation and bronchoconstriction can produce wheeze, cough, chest tightness and breathlessness, often with symptoms that vary over time or in response to triggers. Chronic obstructive pulmonary disease involves persistent respiratory symptoms and airflow limitation associated with abnormalities of the airways, alveoli or both, with smoking being a major risk factor although not the only one.
Bronchiectasis involves permanent abnormal dilation of bronchi and can lead to chronic cough and recurrent respiratory infections. Interstitial lung diseases affect the lung interstitium and can impair diffusion and lung compliance, while pulmonary fibrosis represents a pattern of scarring that can progressively restrict respiratory function. Different mechanisms require different diagnostic and therapeutic approaches.
Respiratory infections range from relatively localised airway infections to severe pneumonia and systemic illness. Viral and bacterial pathogens can cause respiratory disease, with clinical management depending on the suspected organism, severity, host factors and diagnostic findings. Pneumonia can impair alveolar gas exchange through inflammation and fluid accumulation within affected regions of the lung. Some patients develop hypoxaemia requiring supplemental oxygen, while severe disease can progress to respiratory failure.
Antimicrobial therapy is appropriate for selected bacterial infections but does not treat viral infections directly, and inappropriate antibiotic use contributes to antimicrobial resistance. Vaccination, infection-control measures and management of chronic respiratory conditions can reduce the burden of certain respiratory infections. The clinical distinction between infection, inflammatory disease, exacerbation of chronic lung disease and non-pulmonary causes of symptoms is essential.
Pulmonary function testing provides objective information about respiratory mechanics and airflow. Spirometry measures volumes and flow rates during forced breathing and is central to assessing obstructive and restrictive patterns, although interpretation requires appropriate reference values and clinical context. Bronchodilator testing can assess reversibility of airflow limitation in selected circumstances. Lung-volume measurement can identify hyperinflation or restriction, while diffusion-capacity testing evaluates gas transfer across the lungs.
Peak expiratory flow can help monitor variability in selected airway disorders but is less comprehensive than formal pulmonary function testing. Arterial or venous blood gases may be used to assess gas exchange and acid-base status when clinically indicated. Chest radiography, computed tomography and other imaging modalities provide structural information that complements physiological testing.
Respiratory Medicine includes important acute conditions such as respiratory failure, pulmonary embolism and severe asthma exacerbations. Respiratory failure can involve inadequate oxygenation, inadequate carbon-dioxide elimination or both, and may arise from lung disease, impaired ventilation, respiratory muscle weakness, neurological disorders or severe systemic illness. Pulmonary embolism occurs when material, usually a thrombus, obstructs pulmonary arteries and can range from small events with limited physiological effects to life-threatening obstruction and right-heart strain.
Diagnosis involves clinical assessment combined with appropriately selected investigations such as oxygen measurements, electrocardiography, imaging and laboratory testing. Treatment can include oxygen, anticoagulation, thrombolysis or mechanical intervention in selected severe cases. The urgency of respiratory disease depends on physiological impairment rather than simply the presence of a respiratory diagnosis.
Chronic respiratory disease management often involves long-term inhaled therapies, pulmonary rehabilitation, vaccination, exposure reduction and monitoring of disease progression. Inhaled medicines can deliver bronchodilators or anti-inflammatory agents directly to the respiratory tract, reducing systemic exposure compared with some systemic therapies. Correct inhaler technique is important because an appropriately prescribed medicine may provide limited benefit if it does not reach the airways effectively. Pulmonary rehabilitation can improve exercise capacity and quality of life in selected chronic respiratory conditions. Long-term oxygen therapy is indicated for particular forms of chronic hypoxaemia rather than simply for any person who experiences breathlessness. Smoking cessation is particularly important in smoking-related lung disease because continued exposure can accelerate disease progression and increase cancer and cardiovascular risks.
Respiratory Medicine also covers occupational and environmental lung disease. Long-term exposure to dusts, fibres, fumes, gases and other airborne substances can produce diseases including pneumoconioses, occupational asthma and hypersensitivity-related lung disorders. Air pollution can aggravate respiratory symptoms and contribute to cardiovascular and pulmonary disease, with effects varying according to exposure, susceptibility and pollutant type. Tobacco smoke remains a major preventable cause of chronic respiratory disease and lung cancer.
Sleep-related breathing disorders, particularly obstructive sleep apnoea, involve repeated upper-airway obstruction during sleep and can produce intermittent oxygen desaturation and disrupted sleep. Respiratory specialists may therefore use sleep studies, imaging, pulmonary function testing, bronchoscopy and other investigations to identify the mechanism of disease. The field spans both airway and lung pathology and the broader environmental conditions that influence respiratory function.
