Respiratory Emergencies

Sinus tachycardia Atrial arrhythmias, most commonly atrial fibrillation New onset incomplete or complete right bundle branch block Right axis deviation T wave inversion>3 mm in V1 to V3 ST depression >0.5 mm in V1 to V3 Q waves in III and aVF Right ventricular strain (S1, Q3, T3) (large S wave in I, large Q wave in III, inverted T wave in III) Sinus tachycardia Atrial arrhythmias, most commonly atrial fibrillation New onset incomplete or complete right bundle branch block Right axis deviation T wave inversion>3 mm in V1 to V3 ST depression >0.5 mm in V1 to V3 Q waves in III and aVF Right ventricular strain (S1, Q3, T3) (large S wave in I, large Q wave in III, inverted T wave in III) Two-level Wells Score for likelihood of pulmonary embolism Variable Points History Previous DVT/PE 1.5 Surgery under GA or fracture of lower limbs within previous 4 weeks or immobilization >3 days 1.5 Malignancy (receiving treatment, treated in past 6 months or palliative care) 1 Haemoptysis 1 Examination Clinical signs of DVT (minimum of leg swelling and pain with palpation of the deep veins) 3 Heart rate > 100 bpm 1.5 Alternative diagnosis less likely than PE (Respiratory disease: pneumothorax; pneumonia; acute exacerbation of COPD; cardiac disease: acute coronary syndrome; acute congestive heart failure, aortic dissection; musculoskeletal chest pain; gastroesophageal reflux disease; any causefor collapse) 3 Clinical probability of pulmonary embolism Score Likely 4 Unlikely 4 points or less Clinical signs of DVT (minimum of leg swelling and pain with palpation of the deep veins) Alternative diagnosis less likely than PE (Respiratory disease: pneumothorax; pneumonia; acute exacerbation of COPD; cardiac disease: acute coronary syndrome; acute congestive heart failure, aortic dissection; musculoskeletal chest pain; gastroesophageal reflux disease; any causefor collapse) Wells PS, Anderson DR, Rodger M, et al. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer. Ann Intern Med. 2001;135:98–107

Primary survey Tension pneumothorax Dyspnoea; tachypnoea; increasing hypoxaemia; haemodynamic instability, with hypotension and narrowing pulse pressure Contralateral tracheal shift Hyperexpanded chest Hyper-resonance with absent breath sounds Jugular venous distension Flail chest (anterior or lateral double fractures of three or more adjacent ribs; paradoxical segmental chest wall movement over several respiratory cycles and during coughing) Open sucking chest wound Massive haemothorax Cardiac tamponade Tension pneumothorax Dyspnoea; tachypnoea; increasing hypoxaemia; haemodynamic instability, with hypotension and narrowing pulse pressure Contralateral tracheal shift Hyperexpanded chest Hyper-resonance with absent breath sounds Jugular venous distension Flail chest (anterior or lateral double fractures of three or more adjacent ribs; paradoxical segmental chest wall movement over several respiratory cycles and during coughing) Open sucking chest wound Massive haemothorax Cardiac tamponade Secondary survey Contained rupture of thoracic aorta Rupture of tracheo-bronchial tree Oesophageal perforation Diaphragmatic rupture (asymmetrical chest expansion; absent breath sounds; tracheal deviation; elevated hemidiaphragm with loss of normal contour, and intra-thoracic herniation of a hollow viscus (stomach, colon or small bowel) on chest x-ray) Myocardial contusion Pulmonary contusion Contained rupture of thoracic aorta Rupture of tracheo-bronchial tree Oesophageal perforation Diaphragmatic rupture (asymmetrical chest expansion; absent breath sounds; tracheal deviation; elevated hemidiaphragm with loss of normal contour, and intra-thoracic herniation of a hollow viscus (stomach, colon or small bowel) on chest x-ray) Myocardial contusion Pulmonary contusion

Massive haemoptysis (expectoration of >600 ml blood from below the glottis in 24 h or 150 ml blood in a 1 h period) Extensive smoking history Back pain Malaise, fatigue and weight loss lasting more than 3 weeks Dyspnoea at rest Massive haemoptysis (expectoration of >600 ml blood from below the glottis in 24 h or 150 ml blood in a 1 h period) Extensive smoking history Back pain Malaise, fatigue and weight loss lasting more than 3 weeks Dyspnoea at rest

include: Pleuritic chest pain Point tenderness Production of pain by anteroposterior or lateral chest wall compression (“springing”) Local crepitus Subcutaneous emphysema 1st and 2nd rib fractures may be associated with vascular injury (aorta, subclavian artery) or brachial plexus injury 11th and 12th rib fractures may be associated with visceral injury (liver, spleen, kidneys) Pleuritic chest pain Point tenderness Production of pain by anteroposterior or lateral chest wall compression (“springing”) Local crepitus Subcutaneous emphysema 1st and 2nd rib fractures may be associated with vascular injury (aorta, subclavian artery) or brachial plexus injury 11th and 12th rib fractures may be associated with visceral injury (liver, spleen, kidneys)

Confusion (abbreviated mental test score 8 or less, or new disorientation in time, place and person) Raised blood urea nitrogen (>7 mmol/L) Raised respiratory rate (30 breaths per minute or more) Low blood pressure (systolic blood pressure <90 mm Hg, or diastolic blood pressure 7 mmol/L) Raised respiratory rate (30 breaths per minute or more) Low blood pressure (systolic blood pressure <90 mm Hg, or diastolic blood pressure <60 mm Hg) Age 65 years or older Home-based care can be considered for patients scoring 0 or 1, and hospital-based care for those scoring 2 or more (Lim W, van der Eerden MM, Laing R, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax. 2003;58:377–82)

Age <50 years Heart rate 94% on room air No history of DVT/PE No recent trauma or surgery No haemoptysis No exogenous oestrogen No clinical signs of DVT Age <50 years Heart rate 94% on room air No history of DVT/PE No recent trauma or surgery No haemoptysis No exogenous oestrogen No clinical signs of DVT If all eight criteria are met, there is a less than 2% chance of pulmonary embolism (Kline JA, Mitchell AM, Kabrhel C, et al. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemostat. 2004;2:1244–55)

Oropharyngeal sepsis: periodontal disease; gingivitis; dental abscess; tonsillar abscess Impaired level of consciousness: drugs; alcohol; coma; seizure; shock; general anaesthesia Impaired cough and gag reflex: vocal cord paralysis; myopathy; myelopathy Impaired oesophageal function: achalasia, stricture, diverticula Vomiting: ileus, intestinal obstruction Oropharyngeal sepsis: periodontal disease; gingivitis; dental abscess; tonsillar abscess Impaired level of consciousness: drugs; alcohol; coma; seizure; shock; general anaesthesia Impaired cough and gag reflex: vocal cord paralysis; myopathy; myelopathy Impaired oesophageal function: achalasia, stricture, diverticula Vomiting: ileus, intestinal obstruction

(triad of increased dyspnoea, increased sputum volume, and purulent sputum) Precipitating factors Respiratory infection Bacteria: Haemophilus influenzae; Streptococcus pneumoniae; Staphylococcus aureus; Moraxella catarrhalis Viral: Rhinovirus, influenza virus, parainfluenza virus, coronavirus, adenovirus, picornavirus, parvovirus, respiratory syncytial virus Atypical bacteria: mycoplasma pneumoniae; chlamydia pneumoniae; legionella Heart failure Pulmonary embolism Pneumothorax Non-pulmonary infections Environmental: cold temperature, air pollution, cigarette smoke Non-compliance with medication Respiratory infection Bacteria: Haemophilus influenzae; Streptococcus pneumoniae; Staphylococcus aureus; Moraxella catarrhalis Viral: Rhinovirus, influenza virus, parainfluenza virus, coronavirus, adenovirus, picornavirus, parvovirus, respiratory syncytial virus Atypical bacteria: mycoplasma pneumoniae; chlamydia pneumoniae; legionella Heart failure Pulmonary embolism Pneumothorax Non-pulmonary infections Environmental: cold temperature, air pollution, cigarette smoke Non-compliance with medication

Focal density : consolidation; collapse; effusion; mass Diffuse infiltrates Cardiomegaly: left ventricular failure Normal heart size: ARDS; acute coronary syndrome, diastolic failure; interstitial lung disease Hyperlucency Focal: pneumothorax; bulla Generalised: airway disease Normal CXR Pulmonary embolism Airways disease Acidosis; anaemia; hyperventilation Neuromuscular disorders Diffuse infiltrates Cardiomegaly: left ventricular failure Normal heart size: ARDS; acute coronary syndrome, diastolic failure; interstitial lung disease Cardiomegaly: left ventricular failure Normal heart size: ARDS; acute coronary syndrome, diastolic failure; interstitial lung disease Hyperlucency Focal: pneumothorax; bulla Generalised: airway disease Focal: pneumothorax; bulla Generalised: airway disease Normal CXR Pulmonary embolism Airways disease Acidosis; anaemia; hyperventilation Neuromuscular disorders Pulmonary embolism Airways disease Acidosis; anaemia; hyperventilation Neuromuscular disorders

Symptoms from birth or perinatal period Severe upper respiratory tract disease; nasal polpys Family history of unusual chest disease Chronic wet or productive cough Excessive vomiting (gastro-oesophageal reflux, with or without aspiration) Dysphagia (with or without aspiration) Inspiratory stridor Abnormal voice or cry Finger clubbing Failure to thrive Symptoms from birth or perinatal period Severe upper respiratory tract disease; nasal polpys Family history of unusual chest disease Chronic wet or productive cough Excessive vomiting (gastro-oesophageal reflux, with or without aspiration) Dysphagia (with or without aspiration) Inspiratory stridor Abnormal voice or cry Finger clubbing Failure to thrive

Causes of cough (a forced expulsive manoeuvre, usually against a closed glottis, and associated with a characteristic sound) Acute cough (<3 weeks) Respiratory tract infections: viral upper respiratory tract infection, viral rhinosinusitis, common cold, acute bacterial sinusitis, acute bronchitis, pneumonia, acute exacerbation of COPD, pertussis Inhalation of direct irritants: dust, smoke, ozone, air pollutants Inhalation of specific allergen in the asthmatic: pollen, or low concentration of non-specific irritants: cigarette smoke, perfume; house dust mites Allergic rhinitis Chemical exposure: chloramines in swimming pools Medication: ACE inhibitors Subacute cough (3–8 weeks) Post-infectious cough: prior viral upper respiratory tract infection Bordetella pertussis infection Subacute bacterial sinusitis Asthma Neoplasm Chronic cough (>8 weeks) Persistent airway inflammation: COPD, asthma, bronchiectasis Smoking Neoplasm Interstitial lung disease: pulmonary fibrosis Persistent infection: tuberculosis; bronchiectasis Raised left atrial pressure: mitral stenosis, left ventricular failure Inhaled foreign body Iatrogenic: ACE inhibitors, radiation pneumonitis, steroid aerosols Aspiration syndrome: gastro-oesophageal reflux disease; bulbar dysfunction; oesophageal dysmotility Psychogenic Post-nasal drip syndrome (posterior nasal discharge and night cough): sinusitis; rhinitis (allergic; non-allergic; vasomotor) Primary ciliary dyskinesia Acute cough (<3 weeks) Respiratory tract infections: viral upper respiratory tract infection, viral rhinosinusitis, common cold, acute bacterial sinusitis, acute bronchitis, pneumonia, acute exacerbation of COPD, pertussis Inhalation of direct irritants: dust, smoke, ozone, air pollutants Inhalation of specific allergen in the asthmatic: pollen, or low concentration of non-specific irritants: cigarette smoke, perfume; house dust mites Allergic rhinitis Chemical exposure: chloramines in swimming pools Medication: ACE inhibitors Respiratory tract infections: viral upper respiratory tract infection, viral rhinosinusitis, common cold, acute bacterial sinusitis, acute bronchitis, pneumonia, acute exacerbation of COPD, pertussis Inhalation of direct irritants: dust, smoke, ozone, air pollutants Inhalation of specific allergen in the asthmatic: pollen, or low concentration of non-specific irritants: cigarette smoke, perfume; house dust mites Allergic rhinitis Chemical exposure: chloramines in swimming pools Medication: ACE inhibitors Subacute cough (3–8 weeks) Post-infectious cough: prior viral upper respiratory tract infection Bordetella pertussis infection Subacute bacterial sinusitis Asthma Neoplasm Post-infectious cough: prior viral upper respiratory tract infection Bordetella pertussis infection Subacute bacterial sinusitis Asthma Neoplasm Chronic cough (>8 weeks) Persistent airway inflammation: COPD, asthma, bronchiectasis Smoking Neoplasm Interstitial lung disease: pulmonary fibrosis Persistent infection: tuberculosis; bronchiectasis Raised left atrial pressure: mitral stenosis, left ventricular failure Inhaled foreign body Iatrogenic: ACE inhibitors, radiation pneumonitis, steroid aerosols Aspiration syndrome: gastro-oesophageal reflux disease; bulbar dysfunction; oesophageal dysmotility Psychogenic Post-nasal drip syndrome (posterior nasal discharge and night cough): sinusitis; rhinitis (allergic; non-allergic; vasomotor) Primary ciliary dyskinesia Persistent airway inflammation: COPD, asthma, bronchiectasis Smoking Neoplasm Interstitial lung disease: pulmonary fibrosis Persistent infection: tuberculosis; bronchiectasis Raised left atrial pressure: mitral stenosis, left ventricular failure Inhaled foreign body Iatrogenic: ACE inhibitors, radiation pneumonitis, steroid aerosols Aspiration syndrome: gastro-oesophageal reflux disease; bulbar dysfunction; oesophageal dysmotility Psychogenic Post-nasal drip syndrome (posterior nasal discharge and night cough): sinusitis; rhinitis (allergic; non-allergic; vasomotor) Primary ciliary dyskinesia

Confusion Agitation Altered level of consciousness Sweating Cyanosis Coma Confusion Agitation Altered level of consciousness Sweating Cyanosis Coma

Polyphonic wheeze Asthma COPD Heart failure Extrinsic allergic alveolitis Anaphylaxis Asthma COPD Heart failure Extrinsic allergic alveolitis Anaphylaxis Monophonic wheeze Foreign body aspiration Bronchial carcinoma Foreign body aspiration Bronchial carcinoma

“All that wheezes is not asthma” Other obstructive lung disease: COPD; bronchiectasis; cystic fibrosis; eosinophilic bronchitis; primary ciliary dyskinesia syndromes Respiratory infections: recurrent viral lower respiratory tract infections, pulmonary tuberculosis, allergic bronchopulmonary aspergillosis (fever, malaise, recurrent airway obstruction, cough with expectoration of brownish mucus plugs, haemoptysis and peripheral blood eosinophilia; chest x-ray shows upper lobe infiltrates, atelectasis due to mucoid impaction, and tramline shadowing of central bronchiectasis representing thickened bronchial walls) Non-obstructive lung disease: diffuse parenchymal lung disease; pulmonary embolism; chronic eosinophilic pneumonia ( with reverse pulmonary oedema appearance on chest x-ray) Gastroesophageal reflux Vocal cord dysfunction: paroxysmal adduction of the vocal cords on inspiration, expiration or both Upper airway obstruction: large airway stenosis Foreign body aspiration Primary endobronchial tumours Adverse drug reactions: ACE inhibitors Left ventricular failure (“cardiac asthma”) Hyperventilation syndrome and panic attacks Other obstructive lung disease: COPD; bronchiectasis; cystic fibrosis; eosinophilic bronchitis; primary ciliary dyskinesia syndromes Respiratory infections: recurrent viral lower respiratory tract infections, pulmonary tuberculosis, allergic bronchopulmonary aspergillosis (fever, malaise, recurrent airway obstruction, cough with expectoration of brownish mucus plugs, haemoptysis and peripheral blood eosinophilia; chest x-ray shows upper lobe infiltrates, atelectasis due to mucoid impaction, and tramline shadowing of central bronchiectasis representing thickened bronchial walls) Non-obstructive lung disease: diffuse parenchymal lung disease; pulmonary embolism; chronic eosinophilic pneumonia ( with reverse pulmonary oedema appearance on chest x-ray) Gastroesophageal reflux Vocal cord dysfunction: paroxysmal adduction of the vocal cords on inspiration, expiration or both Upper airway obstruction: large airway stenosis Foreign body aspiration Primary endobronchial tumours Adverse drug reactions: ACE inhibitors Left ventricular failure (“cardiac asthma”) Hyperventilation syndrome and panic attacks

on Inferior Surface Arterial obstruction Coarctation of the aorta: 4th–8th ribs bilaterally Aortic thrombosis Subclavian obstruction: after Blalock-Taussig shunt for Tetralogy of Fallot Pulmonary oligaemia Takayasu’s arteritis Coarctation of the aorta: 4th–8th ribs bilaterally Aortic thrombosis Subclavian obstruction: after Blalock-Taussig shunt for Tetralogy of Fallot Pulmonary oligaemia Takayasu’s arteritis Venous obstruction Superior vena caval obstruction Superior vena caval obstruction Arteriovenous Pulmonary arteriovenous malformation Chest wall arteriovenous malformation Pulmonary arteriovenous malformation Chest wall arteriovenous malformation Neurogenic Neurofibromatosis Normal variant Neurofibromatosis Normal variant

Peak expiratory flow Spirometry Chest x-ray (including comparison with previous films) 12 lead ECG Arterial blood gases Full blood count Inflammatory markers: C-reactive protein Renal and liver function tests Venous blood lactate Cardiac biomarkers B-type Natriuretic Peptide Bedside transthoracic echocardiography and pulmonary ultrasound Peak expiratory flow Spirometry Chest x-ray (including comparison with previous films) 12 lead ECG Arterial blood gases Full blood count Inflammatory markers: C-reactive protein Renal and liver function tests Venous blood lactate Cardiac biomarkers B-type Natriuretic Peptide Bedside transthoracic echocardiography and pulmonary ultrasound

Unable to talk Exhaustion Confusion Cyanosis of lips and tongue on room air Silent chest/feeble respiratory effort Saturation <90% PFR <33% of predicted or best No response to beta 2 agonist therapy Bradycardia Coma Hypotension Unable to talk Exhaustion Confusion Cyanosis of lips and tongue on room air Silent chest/feeble respiratory effort Saturation <90% PFR <33% of predicted or best No response to beta 2 agonist therapy Bradycardia Coma Hypotension

Causes of transudative effusion (serous) (<30 g/L) Right ventricular failure Congestive heart failure Constrictive pericarditis Superior vena caval obstruction Cirrhosis of the liver Hypoalbuminaemia: nephrotic syndrome; liver failure Hypothyroidism Meigs syndrome Obstructive uropathy End-stage chronic kidney disease Peritoneal dialysis Right ventricular failure Congestive heart failure Constrictive pericarditis Superior vena caval obstruction Cirrhosis of the liver Hypoalbuminaemia: nephrotic syndrome; liver failure Hypothyroidism Meigs syndrome Obstructive uropathy End-stage chronic kidney disease Peritoneal dialysis Causes of exudative effusion Malignancy: lung; breast; lymphoma; pleural mesothelioma (fixed mediastinum due to pleural encasement; progressive reduction in size of hemithorax associated with pleural thickening); metastases Infection: para-pneumonic effusions; tuberculosis; fungal; parasitic Pulmonary infarction Gastrointestinal: pancreatitis; oesophageal rupture (pleural fluid amylase may be elevated) Autoimmune: systemic lupus erythematosus Radiation pleuritis Post-myocardial infarction Ovarian hyperstimulation syndrome Asbestos –related pleural disease Yellow nail syndrome Trauma: haemothorax; chylothorax Fistula (ventriculo-peritoneal; bilio-peritoneal; gastro-peritoneal) Drugs: nitrofurantoin; methysergide Malignancy: lung; breast; lymphoma; pleural mesothelioma (fixed mediastinum due to pleural encasement; progressive reduction in size of hemithorax associated with pleural thickening); metastases Infection: para-pneumonic effusions; tuberculosis; fungal; parasitic Pulmonary infarction Gastrointestinal: pancreatitis; oesophageal rupture (pleural fluid amylase may be elevated) Autoimmune: systemic lupus erythematosus Radiation pleuritis Post-myocardial infarction Ovarian hyperstimulation syndrome Asbestos –related pleural disease Yellow nail syndrome Trauma: haemothorax; chylothorax Fistula (ventriculo-peritoneal; bilio-peritoneal; gastro-peritoneal) Drugs: nitrofurantoin; methysergide Exudates can demonstrate on bedside ultrasound the following features: Multiple internal echoes from floating debris Septations and loculation Consolidation of lung Pleural thickening Multiple internal echoes from floating debris Septations and loculation Consolidation of lung Pleural thickening

There is evidence of, or predisposing risk factors for, venous thrombosis There is clinical evidence of acute cor pulmonale (acute right ventricular failure) such as distended neck veins, S3 gallop, or a parasternal lift due to right ventricular pressure overload, tachycardia, tachypnoea, and especially if There is ECG evidence of acute cor pulmonale manifested by a new S1-Q3-T3 pattern, new incomplete right bundle branch block, or right ventricular ischaemia There is evidence of, or predisposing risk factors for, venous thrombosis There is clinical evidence of acute cor pulmonale (acute right ventricular failure) such as distended neck veins, S3 gallop, or a parasternal lift due to right ventricular pressure overload, tachycardia, tachypnoea, and especially if There is ECG evidence of acute cor pulmonale manifested by a new S1-Q3-T3 pattern, new incomplete right bundle branch block, or right ventricular ischaemia

Increased dyspnoea A combination of increased wheeze, cough, or mucus secretion Nocturnal asthma Increased use of short acting sympathomimetics (reliever medication) Increased exercise induced asthma Decreased morning peak expiratory flow rate Increased dyspnoea A combination of increased wheeze, cough, or mucus secretion Nocturnal asthma Increased use of short acting sympathomimetics (reliever medication) Increased exercise induced asthma Decreased morning peak expiratory flow rate

Pneumonia Acute respiratory failure Acute abdominal pain New onset of atrial fibrillation Acute confusional state in the elderly Pneumonia Acute respiratory failure Acute abdominal pain New onset of atrial fibrillation Acute confusional state in the elderly

Although conventionally pneumonia has been classified as typical and atypical, it is now recognized that clinical features correlate poorly with microbial aetiology. Typical bacteria pneumonia with signs of lobar consolidation Sudden onset Fever with chills Cough with purulent sputum Pleuritic chest pain Sudden onset Fever with chills Cough with purulent sputum Pleuritic chest pain Atypical pneumonia Gradual onset, with prodrome of headache and myalgia Dry cough Low grade fever Extra-pulmonary manifestations: abdominal pain, diarrhea, confusion More protracted course CXR findings often more severe than clinical presentation Gradual onset, with prodrome of headache and myalgia Dry cough Low grade fever Extra-pulmonary manifestations: abdominal pain, diarrhea, confusion More protracted course CXR findings often more severe than clinical presentation

Single lung lesion Less than 3 cm in diameter Surrounded on all sides by lung parenchyma Benign patterns of calcification: central; diffuse; popcorn; laminated Single lung lesion Less than 3 cm in diameter Surrounded on all sides by lung parenchyma Benign patterns of calcification: central; diffuse; popcorn; laminated Causes of solitary pulmonary nodule Neoplastic: malignant (bronchogenic carcinoma; solitary metastasis; lymphoma; carcinoid tumour); benign (hamartoma; adenoma; benign connective tissue and neural tumours) Inflammatory: granuloma; lung abscess; rheumatoid nodule; inflammatory pseudotumour (plasma cell granuloma) Congenital: arteriovenous malformation; lung cyst; broncho-pulmonary sequestration; bronchial atresia with mucoid impaction Miscellaneous: pulmonary infarct; intra-pulmonary lymph node; mucoid impaction; haematoma; amyloidosis; normal confluence of pulmonary veins; conglomerate mass of silicosis Neoplastic: malignant (bronchogenic carcinoma; solitary metastasis; lymphoma; carcinoid tumour); benign (hamartoma; adenoma; benign connective tissue and neural tumours) Inflammatory: granuloma; lung abscess; rheumatoid nodule; inflammatory pseudotumour (plasma cell granuloma) Congenital: arteriovenous malformation; lung cyst; broncho-pulmonary sequestration; bronchial atresia with mucoid impaction Miscellaneous: pulmonary infarct; intra-pulmonary lymph node; mucoid impaction; haematoma; amyloidosis; normal confluence of pulmonary veins; conglomerate mass of silicosis Mimics of solitary pulmonary nodule Nipple shadow Cutaneous lesion Rib or other bone lesion Vanishing pseudotumour of congestive cardiac failure (loculated pleural effusion) Nipple shadow Cutaneous lesion Rib or other bone lesion Vanishing pseudotumour of congestive cardiac failure (loculated pleural effusion) Features suggestive of malignancy Clinical: older age; COPD; previous malignancy; environmental exposures; haemoptysis; lung cancer in first degree relatives Radiological: speculated appearance; eccentric or speculated calcification; thick walled cavitation Clinical: older age; COPD; previous malignancy; environmental exposures; haemoptysis; lung cancer in first degree relatives Radiological: speculated appearance; eccentric or speculated calcification; thick walled cavitation

Dyspnoea is the conscious and unpleasant awareness of increased work done during breathing, and may indicate cardiac, pulmonary, cardio-pulmonary or neuromuscular disease. Dypsnoea is not synonymous with respiratory distress. There are a number of underlying mechanisms, which may coexist in the same patient. Mechanisms of shortness of breath Increased demand Physiological: exercise; high altitude Pathological: anaemia; increased metabolism (fever, thyrotoxicosis) Impaired performance Airflow obstruction: upper airway obstruction; obstructive lung disease: asthma, COPD, bronchiectasis; lower airway obstruction: foreign body Reduced lung volume (restrictive lung disease): pleural disease/effusion; pneumothorax; kyphoscoliosis; massive obesity; spine or chest wall deformities; interstitial lung disease Impaired gas exchange: alveolar lung disease: consolidation (pneumonia); pulmonary oedema Loss of lung compliance: interstitial lung disease Neuro-muscular diseases: Guillain-Barre syndrome; myasthenia gravis; diaphragmatic paralysis; poliomyelitis; spinal cord injury (cervical cord transection); muscular dystrophies Loss of thoracic cage (chest wall) compliance Mechanisms of shortness of breath Increased demand Physiological: exercise; high altitude Pathological: anaemia; increased metabolism (fever, thyrotoxicosis) Physiological: exercise; high altitude Pathological: anaemia; increased metabolism (fever, thyrotoxicosis) Impaired performance Airflow obstruction: upper airway obstruction; obstructive lung disease: asthma, COPD, bronchiectasis; lower airway obstruction: foreign body Reduced lung volume (restrictive lung disease): pleural disease/effusion; pneumothorax; kyphoscoliosis; massive obesity; spine or chest wall deformities; interstitial lung disease Impaired gas exchange: alveolar lung disease: consolidation (pneumonia); pulmonary oedema Loss of lung compliance: interstitial lung disease Neuro-muscular diseases: Guillain-Barre syndrome; myasthenia gravis; diaphragmatic paralysis; poliomyelitis; spinal cord injury (cervical cord transection); muscular dystrophies Loss of thoracic cage (chest wall) compliance Airflow obstruction: upper airway obstruction; obstructive lung disease: asthma, COPD, bronchiectasis; lower airway obstruction: foreign body Reduced lung volume (restrictive lung disease): pleural disease/effusion; pneumothorax; kyphoscoliosis; massive obesity; spine or chest wall deformities; interstitial lung disease Impaired gas exchange: alveolar lung disease: consolidation (pneumonia); pulmonary oedema Loss of lung compliance: interstitial lung disease Neuro-muscular diseases: Guillain-Barre syndrome; myasthenia gravis; diaphragmatic paralysis; poliomyelitis; spinal cord injury (cervical cord transection); muscular dystrophies Loss of thoracic cage (chest wall) compliance Hyperventilation resulting from medullary respiratory centre stimulation in response to chemical or neural stimuli Increased arterial hydrogen ion concentration, e.g. metabolic acidosis producing air hunger (Kussmaul’s breathing) Increased arterial paCO 2 , e.g. respiratory acidosis Decreased arterial PaO 2 via aortic, carotid and brain stem chemoreceptors, e.g. pneumonia, impaired oxygen delivery due to anaemia, shock and stroke Increased central arousal, e.g. exertion, anxiety, thyrotoxicosis, phaeochromocytoma Pulmonary J receptor discharge, e.g. pulmonary oedema Increased arterial hydrogen ion concentration, e.g. metabolic acidosis producing air hunger (Kussmaul’s breathing) Increased arterial paCO 2 , e.g. respiratory acidosis Decreased arterial PaO 2 via aortic, carotid and brain stem chemoreceptors, e.g. pneumonia, impaired oxygen delivery due to anaemia, shock and stroke Increased central arousal, e.g. exertion, anxiety, thyrotoxicosis, phaeochromocytoma Pulmonary J receptor discharge, e.g. pulmonary oedema

Caused by direct trauma, such as antero-posterior compression from seat belt or steering wheel injuries, with posterior displacement of the distal sternal fragment, or indirect trauma, such as hyperflexion and axial compression, with posterior displacement of the proximal sternal agent. Manubrio-sternal joint dislocation may also result by these mechanisms. Can be associated with myocardial or pulmonary contusion Usually diagnosed on a lateral view of the sternum Isolated sternal fracture with normal 12 lead ECG and normal chest x-ray carries a very low risk of intrathoracic injury Caused by direct trauma, such as antero-posterior compression from seat belt or steering wheel injuries, with posterior displacement of the distal sternal fragment, or indirect trauma, such as hyperflexion and axial compression, with posterior displacement of the proximal sternal agent. Manubrio-sternal joint dislocation may also result by these mechanisms. Can be associated with myocardial or pulmonary contusion Usually diagnosed on a lateral view of the sternum Isolated sternal fracture with normal 12 lead ECG and normal chest x-ray carries a very low risk of intrathoracic injury

Linear (due to thickening of interlobular septa) Kerley A lines: 2–6 cm long and <1 mm wide, radiating out from hilum towards pleura Kerley B lines: short (1–2 cm long) and 1–2 mm wide, perpendicular to lower lateral pleural edge Reticular (mesh-like network appearance): fine, medium, coarse Nodular (multiple discrete round opacities): military (1–2 mm), small, medium, large Reticulo-nodular Linear (due to thickening of interlobular septa) Kerley A lines: 2–6 cm long and <1 mm wide, radiating out from hilum towards pleura Kerley B lines: short (1–2 cm long) and 1–2 mm wide, perpendicular to lower lateral pleural edge Reticular (mesh-like network appearance): fine, medium, coarse Nodular (multiple discrete round opacities): military (1–2 mm), small, medium, large Reticulo-nodular

Cavitary lesions Alveolar infiltrates: diffuse; localized Mass lesion Bronchiectasis Cardiomegaly and increased pulmonary blood flow Hilar adenopathy or mass Normal Cavitary lesions Alveolar infiltrates: diffuse; localized Mass lesion Bronchiectasis Cardiomegaly and increased pulmonary blood flow Hilar adenopathy or mass Normal

Chest pain: pleuritic (pulmonary embolism, pneumothorax, pneumonia); cardiac (acute coronary syndrome; mechanical complications: interventricular septal rupture, mitral regurgitation from chordae rupture; cardiac arrhythmia) Cough: pneumonia; asthma; COPD Orthopnea: congestive heart failure; bilateral diaphragmatic paralysis Paroxysmal nocturnal dyspnoea: congestive heart failure Severe sore throat: epiglottitis Platypnoea (dyspnoea worse on upright posture and relieved on recumbency): hepato-pulmonary syndrome with right-to-left shunt, patent foramen ovale Chest pain: pleuritic (pulmonary embolism, pneumothorax, pneumonia); cardiac (acute coronary syndrome; mechanical complications: interventricular septal rupture, mitral regurgitation from chordae rupture; cardiac arrhythmia) Cough: pneumonia; asthma; COPD Orthopnea: congestive heart failure; bilateral diaphragmatic paralysis Paroxysmal nocturnal dyspnoea: congestive heart failure Severe sore throat: epiglottitis Platypnoea (dyspnoea worse on upright posture and relieved on recumbency): hepato-pulmonary syndrome with right-to-left shunt, patent foramen ovale

IgE related: allergens (animals and pets; grain; house dust mites; pollen, including trees and grass; moulds and fungi); proteolytic enzymes Non IgE related: hardwood dust; colophony fumes (solder); isocyanates; exercise; sex; atmospheric pollution (traffic fumes); emotion; smoking and second-hand smoke; recreational drugs; weather and changes in temperature; viral infections IgE related: allergens (animals and pets; grain; house dust mites; pollen, including trees and grass; moulds and fungi); proteolytic enzymes Non IgE related: hardwood dust; colophony fumes (solder); isocyanates; exercise; sex; atmospheric pollution (traffic fumes); emotion; smoking and second-hand smoke; recreational drugs; weather and changes in temperature; viral infections

Sudden (foreign body aspiration) or gradual onset Duration Diurnal variation Relation to initial upper respiratory tract infection Paroxysms of cough, with or without syncope Cough on eating or post-prandial: gastro-oesophageal reflux Triggers/aggravating factors: air temperature change; exercise; aerosols Production of sputum; haemoptysis Smoking Occupational history Medication history: ACE inhibitors Chronic lung disease: COPD, bronchiectasis Atopic disease Sudden (foreign body aspiration) or gradual onset Duration Diurnal variation Relation to initial upper respiratory tract infection Paroxysms of cough, with or without syncope Cough on eating or post-prandial: gastro-oesophageal reflux Triggers/aggravating factors: air temperature change; exercise; aerosols Production of sputum; haemoptysis Smoking Occupational history Medication history: ACE inhibitors Chronic lung disease: COPD, bronchiectasis Atopic disease

Ability to talk with ease Respiratory rate, especially if >30 breaths per minute Inability to adopt the supine position (orthopnoea) Increased effort of breathing Degree of hypoxaemia (oxygen saturation <92%) Central cyanosis, which equates to a concentration of deoxygenated haemoglobin greater than 50 g/L Peak expiratory flow rate 30 breaths per minute Inability to adopt the supine position (orthopnoea) Increased effort of breathing Degree of hypoxaemia (oxygen saturation <92%) Central cyanosis, which equates to a concentration of deoxygenated haemoglobin greater than 50 g/L Peak expiratory flow rate <50% of predicted

Pulmonary infarction Non-infective, inflammatory pneumonia: Eosinophilic pneumonia diffuse bilateral alveolar opacities, inter-lobular septal thickening producing Kerley B lines, and bilateral small pleural effusions Broncho-pulmonary aspergillosis Cryptogenic organising pneumonia (presents with a subacute onset of dry cough, shortness of breath, anorexia, malaise, fever and weight loss; multiple bilateral patchy alveolar opacities with a peripheral sub-pleural and bronchovascular distribution, often migratory as the disease progresses; normal lung volumes; refractory to antibiotic therapy; rapid clinical and radiological improvement with steroid therapy) Pulmonary vasculitis: granulomatosis with polyangiitis (Wegener’s granulomatosis) (solitary or mutiple pulmonary nodules, with or without cavitation) Eosinophilic granuloma Acute allergic or toxic pneumonitis Pulmonary infarction Non-infective, inflammatory pneumonia: Eosinophilic pneumonia diffuse bilateral alveolar opacities, inter-lobular septal thickening producing Kerley B lines, and bilateral small pleural effusions Broncho-pulmonary aspergillosis Cryptogenic organising pneumonia (presents with a subacute onset of dry cough, shortness of breath, anorexia, malaise, fever and weight loss; multiple bilateral patchy alveolar opacities with a peripheral sub-pleural and bronchovascular distribution, often migratory as the disease progresses; normal lung volumes; refractory to antibiotic therapy; rapid clinical and radiological improvement with steroid therapy) Pulmonary vasculitis: granulomatosis with polyangiitis (Wegener’s granulomatosis) (solitary or mutiple pulmonary nodules, with or without cavitation) Eosinophilic granuloma Acute allergic or toxic pneumonitis

Poorly adherent probe Dark skin Excessive motion: motion artifact Low signal-noise ratio with impaired peripheral perfusion: shock; cardiac arrest False nails; blue, black or green nail varnish Lipaemia: hyperlipidaemia; propofol infusion Bright ambient light Abnormal haemoglobins: carboxyhaemoglobin; methaemoglobin Intravenous dyes: methylene blues SpO 2 < 80% Venous pulsations: obstructed venous return; severe right heart failure; dependent limb; tourniquet constriction Poorly adherent probe Dark skin Excessive motion: motion artifact Low signal-noise ratio with impaired peripheral perfusion: shock; cardiac arrest False nails; blue, black or green nail varnish Lipaemia: hyperlipidaemia; propofol infusion Bright ambient light Abnormal haemoglobins: carboxyhaemoglobin; methaemoglobin Intravenous dyes: methylene blues SpO 2 < 80% Venous pulsations: obstructed venous return; severe right heart failure; dependent limb; tourniquet constriction

Risk factors (related to Virchow’s triad of hypercoagulability of blood, venous stasis and vascular endothelial injury) may be temporary or reversible (provoked thromboembolism) or persistent. Major Surgery: recent major abdominal or pelvic surgery; hip or knee replacement Obstetric: late pregnancy; Casarean section; puerperium Pelvic and lower limb fractures Varicose veins Malignancy: abdominal or pelvic malignancy; advanced or metastatic malignancy Reduced mobility: prolonged bed rest; hospitalization; institutional care Previous venous thromboembolism Surgery: recent major abdominal or pelvic surgery; hip or knee replacement Obstetric: late pregnancy; Casarean section; puerperium Pelvic and lower limb fractures Varicose veins Malignancy: abdominal or pelvic malignancy; advanced or metastatic malignancy Reduced mobility: prolonged bed rest; hospitalization; institutional care Previous venous thromboembolism Minor Age >60 years Oestrogens: oral contraceptive; oestrogen replacement therapy (HRT) Hypercoagulable states Chronic indwelling central venous catheters Multiple trauma Spinal cord injury Myeloproliferative disorders (hyperviscosity) Chronic heart failure Cerebrovascular accident with hemiplegia Acute medical illness Family history of venous thromboembolism Acquired thrombophilic syndromes: antiphospholipid antibody syndrome; paroxysmal nocturnal haemoglobinuria; nephrotic syndrome Inherited thrombophilic syndromes: antithrombin III deficiency; protein C and protein S deficiency; factor V Leiden mutation (activated protein C resistance); factor II (prothrombin) gene mutation G20210A causing elevated prothrombin levels; hyperhomocystinaemia Mixed thrombophilic syndromes: hyperhomocysteinaemia; elevated factor VIII levels Long distance sedentary travel (>4 h in the preceding month) Occult malignancy (Trousseau’s syndrome of chronic disseminated intravascular coagulation associated with migratory thrombophlebitis, multiple thrombotic events (venous and arterial), bleeding, therapeutic warfarin resistance, and non-bacterial thrombotic endocarditis, is associated with occult cancer). Unprovoked venous thromboembolism may indicate the need for testing for undiagnosed cancer by physical examination, blood tests and chest x-ray. Age >60 years Oestrogens: oral contraceptive; oestrogen replacement therapy (HRT) Hypercoagulable states Chronic indwelling central venous catheters Multiple trauma Spinal cord injury Myeloproliferative disorders (hyperviscosity) Chronic heart failure Cerebrovascular accident with hemiplegia Acute medical illness Family history of venous thromboembolism Acquired thrombophilic syndromes: antiphospholipid antibody syndrome; paroxysmal nocturnal haemoglobinuria; nephrotic syndrome Inherited thrombophilic syndromes: antithrombin III deficiency; protein C and protein S deficiency; factor V Leiden mutation (activated protein C resistance); factor II (prothrombin) gene mutation G20210A causing elevated prothrombin levels; hyperhomocystinaemia Mixed thrombophilic syndromes: hyperhomocysteinaemia; elevated factor VIII levels Long distance sedentary travel (>4 h in the preceding month) Occult malignancy (Trousseau’s syndrome of chronic disseminated intravascular coagulation associated with migratory thrombophlebitis, multiple thrombotic events (venous and arterial), bleeding, therapeutic warfarin resistance, and non-bacterial thrombotic endocarditis, is associated with occult cancer). Unprovoked venous thromboembolism may indicate the need for testing for undiagnosed cancer by physical examination, blood tests and chest x-ray.

It is important to consider the diagnosis in the following circumstances, given the non-specificity of symptoms and signs, aided by the presence of thrombo-embolic risk factors: Acute dyspnoea, especially when unexplained Cardiovascular collapse, with arterial hypotension (SBP 15 min) and cardiogenic shock related to acute right ventricular failure (massive pulmonary embolism) Pleuritic chest pain Pulmonary infarction: pleuritic chest pain, dyspnoea and haemoptysis Near syncope or syncope Chronic progressive dyspnoea (chronic thrombo-embolic pulmonary hypertension) Acute dyspnoea, especially when unexplained Cardiovascular collapse, with arterial hypotension (SBP 15 min) and cardiogenic shock related to acute right ventricular failure (massive pulmonary embolism) Pleuritic chest pain Pulmonary infarction: pleuritic chest pain, dyspnoea and haemoptysis Near syncope or syncope Chronic progressive dyspnoea (chronic thrombo-embolic pulmonary hypertension)

Predominantly lower lobe distribution, with reduced lung volumes: idiopathic pulmonary fibrosis, collagen vascular disease, asbestosis, chronic aspiration Reticulo-nodular pattern with increased lung volume: lymphangioleiomyomatosis, Langhans cell histiocytosis (multiple upper lobe nodules, many of which cavitate and are replaced by irregular thin-walled cysts of varying sizes) Predominantly upper and middle lobe distribution: mycobacterial and fungal disease, silicosis, sarcoidosis, extrinsic allergic alveolitis (hypersensitivity pneumonitis) Predominantly lower lobe distribution, with reduced lung volumes: idiopathic pulmonary fibrosis, collagen vascular disease, asbestosis, chronic aspiration Reticulo-nodular pattern with increased lung volume: lymphangioleiomyomatosis, Langhans cell histiocytosis (multiple upper lobe nodules, many of which cavitate and are replaced by irregular thin-walled cysts of varying sizes) Predominantly upper and middle lobe distribution: mycobacterial and fungal disease, silicosis, sarcoidosis, extrinsic allergic alveolitis (hypersensitivity pneumonitis)

Chronic productive cough in the absence of wheeze or shortness of breath Smoking history >20 pack years (pack year= (cigarettes smoked per day/20) × number of years smoking) Voice disturbance Symptoms with colds only, with no interval symptoms Normal physical examination of the chest when symptomatic Normal peak expiratory flow when symptomatic Cardiac disease Chronic productive cough in the absence of wheeze or shortness of breath Smoking history >20 pack years (pack year= (cigarettes smoked per day/20) × number of years smoking) Voice disturbance Symptoms with colds only, with no interval symptoms Normal physical examination of the chest when symptomatic Normal peak expiratory flow when symptomatic Cardiac disease

(based on oropharyngeal examination, assessment of atlanto-occipital joint mobility and of the space between the horizontal ramus of mandible and the hyoid bone-the potential displacement space) Small mouth Limited mouth opening (3 cm or less, two fingerbreadths or less); limited temporomandibular joint mobility; trismus Protruding upper incisors Dental implants Short inter-incisor distance Large tongue (macroglossia) Cleft or high arched narrow palate Mandibular hypoplasia (micrognathia) Short or muscular neck Limited neck mobility Obesity Small mouth Limited mouth opening (3 cm or less, two fingerbreadths or less); limited temporomandibular joint mobility; trismus Protruding upper incisors Dental implants Short inter-incisor distance Large tongue (macroglossia) Cleft or high arched narrow palate Mandibular hypoplasia (micrognathia) Short or muscular neck Limited neck mobility Obesity In addition, current airway obstruction, inflammation and haemorrhage are also predictors of a difficult airway

It is important to distinguish between true haemoptysis, pseudo-haemoptysis (coughing of blood that originates from a source other than the lower respiratory tract, namely the upper airway or oral cavity), or haematemesis, based on the history. Haemoptysis is a common symptom, and can vary from streaks of blood in the sputum to massive haemorrhage. Post-nasal drip or epistaxis suggest pseudo-haemoptysis Smoking history Occupational exposure: asbestos; silica Weight loss Pleuritic chest pain Symptoms of congestive heart failure: breathlessness on exertion, orthopnoea, paroxysmal nocturnal dyspnoea Productive cough and fever Concurrent with menstruation (catamenial haemoptysis related to pulmonary endometriosis) History of cancer Anticoagulant therapy Exposure to tuberculosis Travel history Coexisting renal disease Post-nasal drip or epistaxis suggest pseudo-haemoptysis Smoking history Occupational exposure: asbestos; silica Weight loss Pleuritic chest pain Symptoms of congestive heart failure: breathlessness on exertion, orthopnoea, paroxysmal nocturnal dyspnoea Productive cough and fever Concurrent with menstruation (catamenial haemoptysis related to pulmonary endometriosis) History of cancer Anticoagulant therapy Exposure to tuberculosis Travel history Coexisting renal disease

Widening of the mediastinum is most often due to technical factors such as patient positioning or the projection used. Rotation, incomplete inspiration, or an AP view, may all exaggerate the width of the mediastinum, as well as heart size. Mediastinal width >6 cm in erect PA film Mediastinal width >8 cm in supine AP chest film Mediastinal width >7.5 cm at aortic knob Ratio of mediastinal width to chest width >0.25 at aortic knob Mediastinal width >6 cm in erect PA film Mediastinal width >8 cm in supine AP chest film Mediastinal width >7.5 cm at aortic knob Ratio of mediastinal width to chest width >0.25 at aortic knob

Fine end-inspiratory crackles over both lung bases: pulmonary oedema Medium end-inspiratory crackles: pulmonary fibrosis Localised crackles: pneumonia Expiratory wheeze: airways obstruction Absent breath sounds: pneumothorax Fine end-inspiratory crackles over both lung bases: pulmonary oedema Medium end-inspiratory crackles: pulmonary fibrosis Localised crackles: pneumonia Expiratory wheeze: airways obstruction Absent breath sounds: pneumothorax

Natural history: acute (<3 weeks’ symptoms), episodic, chronic Respiratory risk factors: smoking; family history of respiratory disease; occupational history (asbestos; coal mining); hobbies, travel, environmental exposure to organic antigens at home or work (including birds, pets); HIV risk factors Rheumatological symptoms: myalgia; arthralgia; proximal muscle weakness; Raynaud’s phenomenon’ morning stiffness Drug history Past medical history Natural history: acute (<3 weeks’ symptoms), episodic, chronic Respiratory risk factors: smoking; family history of respiratory disease; occupational history (asbestos; coal mining); hobbies, travel, environmental exposure to organic antigens at home or work (including birds, pets); HIV risk factors Rheumatological symptoms: myalgia; arthralgia; proximal muscle weakness; Raynaud’s phenomenon’ morning stiffness Drug history Past medical history

Mediastinal widening, with mediastinal-chest ratio >0.25 and superior mediastinal width >8 cm Loss of, or abnormal, aortic knob contour Tracheal deviation to the right Wide right paratracheal stripe Depression of left main stem bronchus Oesophageal deviation (nasogastric tube) deviation to the right Left apical pleural cap: a curvilinear opacity with mass effect on the lung apex Wide left paraspinal line Left haemothorax Fractures of upper ribs Mediastinal widening, with mediastinal-chest ratio >0.25 and superior mediastinal width >8 cm Loss of, or abnormal, aortic knob contour Tracheal deviation to the right Wide right paratracheal stripe Depression of left main stem bronchus Oesophageal deviation (nasogastric tube) deviation to the right Left apical pleural cap: a curvilinear opacity with mass effect on the lung apex Wide left paraspinal line Left haemothorax Fractures of upper ribs

Water cooling units: Legionella Military barracks: Mycoplasma Birds: psittacosis, histoplasmosis, aspergillosis Dogs, cats, rats, pigs, cattle: leptospirosis Goats, pigs, cattle: Q fever Abattoirs, veterinary practitioners: brucellosis Soil: blastomycosis Decaying wood, caves, chicken: histoplasmosis Florists, gardeners, plants, straw: sporotrichosis Water cooling units: Legionella Military barracks: Mycoplasma Birds: psittacosis, histoplasmosis, aspergillosis Dogs, cats, rats, pigs, cattle: leptospirosis Goats, pigs, cattle: Q fever Abattoirs, veterinary practitioners: brucellosis Soil: blastomycosis Decaying wood, caves, chicken: histoplasmosis Florists, gardeners, plants, straw: sporotrichosis

Mild: PEFR >75% predicted or best PEFR >75% predicted or best Moderate: PEFR 50–75% predicted or best PEFR 50–75% predicted or best Severe: PEFR 25/min Tachycardia >110/min PEFR 25/min Tachycardia >110/min Life threatening

Pneumomediastinum indicates perforation of some portion of either the respiratory or gastrointestinal tracts Features of pneumomediastinum Free mediastinal air, causing streaky radiolucencies in the mediastinum and outlining the heart borders, the central diaphragm (causing visualisation of the entire disphragm) and the thymus, and extending to the neck Subcutaneous emphysema Ring shaped radiolucencies around the aorta and pulmonary artery Free mediastinal air, causing streaky radiolucencies in the mediastinum and outlining the heart borders, the central diaphragm (causing visualisation of the entire disphragm) and the thymus, and extending to the neck Subcutaneous emphysema Ring shaped radiolucencies around the aorta and pulmonary artery Causes of pneumomediastinum Alveolar rupture: spontaneous; positive pressure ventilation; compressive trauma to the chest; rupture of lung by rib fracture with tracking of air into the mediastinum by way of the chest wall and neck; asthma Traumatic laceration of trachea or a central bronchus (associated with double wall sign, caused by intramural air in proximal airways leading to visualisation of both sides of the bronchial wall, and the fallen lung sign of collapse of the inferior lung) Spontaneous or iatrogenic perforation of pharynx, oesophagus, duodenum, colon, or rectum, with tracking of air into the mediastinum: Boerhaave syndrome; endoscopic intervention (biopsy, dilatation, sclerotherapy) Following placement of an intercostal tube or mediastinoscopy or similar invasive procedures Alveolar rupture: spontaneous; positive pressure ventilation; compressive trauma to the chest; rupture of lung by rib fracture with tracking of air into the mediastinum by way of the chest wall and neck; asthma Traumatic laceration of trachea or a central bronchus (associated with double wall sign, caused by intramural air in proximal airways leading to visualisation of both sides of the bronchial wall, and the fallen lung sign of collapse of the inferior lung) Spontaneous or iatrogenic perforation of pharynx, oesophagus, duodenum, colon, or rectum, with tracking of air into the mediastinum: Boerhaave syndrome; endoscopic intervention (biopsy, dilatation, sclerotherapy) Following placement of an intercostal tube or mediastinoscopy or similar invasive procedures