HERMES Adult Respiratory Medicine key terms

The fraction of a forced vital capacity expired in the first second; a reduced ratio after bronchodilator testing supports airflow obstruction, while a preserved or raised ratio suggests restriction or normal physiology.

Narrowing of the bronchial tree that slows expiration, detected as a low FEV1/FVC ratio on spirometry and often accompanied by hyperinflation and air trapping.

Retention of gas in the lungs because of premature airway closure, shown by a raised residual volume or residual volume to total lung capacity ratio on plethysmography.

Repeat spirometry after an inhaled short-acting bronchodilator; a substantial rise in FEV1 or FVC supports a diagnosis of asthma rather than fixed obstruction.

Inhalation of escalating doses of methacholine, histamine or mannitol to demonstrate airway hyperresponsiveness when asthma is suspected but baseline spirometry is normal.

Fraction of exhaled nitric oxide, a non-invasive marker of eosinophilic airway inflammation that is raised in atopic asthma and falls with corticosteroid treatment or adherence.

An acute worsening of airway disease driven by eosinophilic inflammation, typically steroid-responsive and associated with raised blood or sputum eosinophils and often with viral triggers.

Increased lung volumes at rest, with an elevated functional residual capacity or total lung capacity, which flattens the diaphragm and increases the work of breathing.

Progressive rise in end-expiratory lung volume during exercise or tachypnoea when expiratory time is too short to reach relaxation volume, causing breathlessness and reduced exercise capacity.

Positive alveolar pressure at end-expiration generated by incomplete emptying, which opposes triggering during mechanical ventilation and can cause hypotension or barotrauma.

Measured end-expiratory alveolar pressure above the set extrinsic PEEP, detected by an expiratory hold manoeuvre and managed by lengthening expiratory time or reducing minute ventilation.

A radiological and histological pattern of subpleural, basal-predominant reticulation with honeycombing and minimal ground glass, characteristic of idiopathic pulmonary fibrosis.

Clustered cystic airspaces with thick walls arranged in layers beneath the pleura, representing irreversible fibrosis and a key feature of a usual interstitial pneumonia pattern.

Airway dilatation produced by surrounding fibrotic tissue rather than by airway wall disease, seen on high-resolution CT in advanced interstitial lung disease.

A progressive fibrosing interstitial lung disease of unknown cause, diagnosed from a usual interstitial pneumonia pattern plus exclusion of other causes, treated with antifibrotics.

Drugs such as pirfenidone or nintedanib that slow the rate of lung function loss in progressive fibrosis without reversing existing scarring, requiring monitoring of liver and gastrointestinal effects.

The absolute or relative fall in FVC over time, used as the main physiological endpoint for monitoring progression and treatment response in fibrotic lung disease.

A structured case conference combining clinical, radiological and pathological information to reach a consensus diagnosis in interstitial lung disease when individual assessments conflict.

Immune-mediated interstitial lung disease provoked by repeated inhalation of an organic antigen, presenting with ground-glass change, air trapping and sometimes poorly formed granulomas.

Removing or reducing exposure to the responsible inhaled trigger in hypersensitivity pneumonitis, combined with corticosteroids in symptomatic or progressive disease.

Chronic lung disease of prematurity following prolonged oxygen or ventilation, with arrested alveolarisation, oxygen dependency and recurrent wheeze in later childhood.

Pauses in breathing longer than 20 seconds, or shorter pauses with bradycardia or desaturation, in infants born before about 37 weeks due to immature respiratory control.

A methylxanthine used to reduce apnoeas and facilitate weaning from ventilation in preterm infants by stimulating the respiratory centre and improving diaphragmatic contractility.

An autosomal recessive disorder of chloride transport causing viscous secretions, bronchiectasis, pancreatic insufficiency and sweat chloride elevation, managed with airway clearance and CFTR modulators.

Pilocarpine iontophoresis with chloride measurement, the diagnostic standard for cystic fibrosis; raised values require confirmation and may be normal in some genetic variants.

Irreversible dilatation of bronchi with thickened walls, chronic productive cough and recurrent infection, confirmed on CT by an increased bronchoarterial ratio or lack of tapering.

Techniques such as postural drainage, oscillating positive expiratory pressure and assisted coughing that mobilise retained secretions in bronchiectasis, cystic fibrosis and neuromuscular weakness.

Occlusion of pulmonary arteries by thrombus, usually from deep veins, causing pleuritic pain, dyspnoea, hypoxia and right ventricular strain; managed with anticoagulation or thrombolysis.

Contrast-enhanced CT timed to opacify the pulmonary arteries, the first-line imaging test for suspected pulmonary embolism in most stable patients.

Echocardiographic or CT evidence of right ventricular dilatation, hypokinesis or septal flattening from acute pressure overload, which identifies higher-risk pulmonary embolism.

Systemic or catheter-directed delivery of a fibrinolytic agent to dissolve thrombus, indicated in pulmonary embolism with haemodynamic instability and considered in deteriorating patients.

Mean pulmonary arterial pressure above 20 mmHg at rest on right heart catheterisation, classified by mechanism into arterial, left heart, lung disease, chronic thromboembolic and multifactorial groups.

Invasive measurement of right atrial, pulmonary arterial and wedge pressures with cardiac output, required to confirm pulmonary hypertension and guide vasodilator therapy.

Pulmonary hypertension persisting after at least three months of anticoagulation for embolism, caused by organised thrombus; potentially curable by pulmonary endarterectomy.

Acute hypoxaemic respiratory failure within a week of a known insult, with bilateral opacities not fully explained by heart failure and a low PaO2/FiO2 ratio on positive pressure.

A ventilation strategy using low tidal volumes around 6 mL/kg predicted body weight with limited plateau pressure, which reduces ventilator-induced lung injury and mortality in ARDS.

Plateau pressure minus applied PEEP; it reflects tidal strain on aerated lung and is associated with outcome in ARDS independently of tidal volume.

Turning a ventilated patient face down for prolonged periods to improve ventilation-perfusion matching and reduce mortality in moderate to severe ARDS.

A transient increase in airway pressure intended to reopen collapsed alveoli in ARDS; benefits are uncertain and it carries a risk of barotrauma and hypotension.

Respiratory support delivered through a mask without an artificial airway, used in hypercapnic exacerbations of COPD and cardiogenic pulmonary oedema, but not routinely in de novo hypoxaemic failure.

Heated, humidified oxygen at high flow through nasal cannulae, providing modest positive pressure and stable FiO2; used in acute hypoxaemic respiratory failure and post-extubation.

Acute infection of lung parenchyma acquired outside hospital, diagnosed from symptoms plus a new infiltrate and stratified for site of care using a severity score.

A severity score allocating one point each for confusion, urea above 7 mmol/L, respiratory rate 30 or more, low blood pressure and age 65 or above, guiding admission decisions.

Frank pus in the pleural space complicating pneumonia, requiring drainage and prolonged antibiotics; loculation and low pleural pH or glucose support the diagnosis.

Abnormal fluid accumulation between the visceral and parietal pleura, classified as transudate or exudate by protein and lactate dehydrogenase, with thoracentesis guiding management.

Pleural fluid to serum ratios of protein above 0.5 or lactate dehydrogenase above 0.6, or fluid LDH over two-thirds the upper normal serum limit, identifying an exudate.

Infection with Mycobacterium tuberculosis, diagnosed by sputum microscopy, culture or nucleic acid amplification; latent infection is treated to prevent progression to active disease.

Persistent immune response to mycobacterial antigens without clinical or radiological evidence of active disease, detected by interferon-gamma release assay or tuberculin skin testing.

Use of a negative-pressure room with high-efficiency filtration and fitted respiratory protection to prevent transmission of pathogens spread by droplet nuclei, such as tuberculosis.

Repetitive upper airway collapse during sleep causing apnoeas, oxygen desaturation, arousals and daytime sleepiness, quantified by the apnoea-hypopnoea index.

The number of apnoeas and hypopnoeas per hour of sleep on a sleep study, used to grade severity and to define obstructive sleep apnoea above five events per hour.

Attended overnight recording of EEG, eye movements, airflow, respiratory effort, oxygen saturation and limb movement, the reference standard for diagnosing sleep-disordered breathing.

Continuous positive airway pressure delivered by mask to splint the upper airway open in obstructive sleep apnoea, reducing events and symptoms when adherence is adequate.

Daytime hypercapnia with a body mass index of 30 or more in the absence of other causes, reflecting reduced ventilatory drive and chest wall load, often with coexisting sleep apnoea.

Low-dose CT offered to high-risk ever-smokers within a defined age range to detect early lung cancer, with benefit dependent on selection, nodule protocols and smoking cessation support.

A rounded opacity up to 3 cm surrounded by lung, assessed by size, growth and morphology; risk of malignancy guides surveillance intervals or further investigation.

A classification of tumour size and invasion, regional nodal involvement and distant metastasis that determines prognosis and whether surgery, radiotherapy or systemic therapy is appropriate.

An oral targeted drug for non-small cell lung cancer harbouring activating EGFR mutations, offering high response rates but eventual resistance through secondary mutations.

An antibody blocking inhibitory receptors such as PD-1 or PD-L1 that restores T-cell activity against tumour cells, with immune-related adverse events affecting lungs, gut and endocrine organs.