Respiratory distress

Respiratory distress is the clinical state of laboured, uncomfortable breathing with signs of increased work: tachypnoea, accessory muscle use, retractions, nasal flaring, grunting (in children), abnormal posture, difficulty speaking and anxiety.

It is a clinical syndrome, not a diagnosis, and sits between dyspnoea (symptom) and respiratory failure (abnormal gases). Recognising distress early, before exhaustion and hypoxia or hypercapnia, prevents arrest.

Clinical relevance. Respiratory distress is among the commonest reasons for emergency assessment and critical care admission. Silent chest, drowsiness and a falling respiratory rate are signs of impending arrest, not of improvement.

Classification.

• By severity:

• Mild: speaks in sentences, mild tachypnoea, saturation 94% or more.
• Moderate: speaks in phrases, accessory muscle use, saturation 90% to 94%.
• Severe: speaks in words, tripod posture, retractions, saturation under 90%.
• Impending arrest: exhaustion, bradypnoea, cyanosis, confusion, silent chest, bradycardia.

• By site: upper airway (stridor, voice change, drooling), lower airway (wheeze, prolonged expiration), parenchymal (crackles, bronchial breathing), pleural (asymmetry), cardiac, central, neuromuscular and chest wall.
• By onset: sudden (seconds to minutes: airway obstruction, pneumothorax, embolism, anaphylaxis, aspiration), acute (hours: asthma, pneumonia, oedema), subacute (days: infection, effusion, malignancy).
• Neonatal: respiratory distress syndrome (surfactant deficiency), transient tachypnoea of the newborn, meconium aspiration, pneumonia, pneumothorax, congenital diaphragmatic hernia, pulmonary hypoplasia, congenital heart disease.
• Acute respiratory distress syndrome: acute (within 1 week) bilateral opacities, non cardiogenic origin, PaO2 to FiO2 ratio of 300 mmHg or under with positive end expiratory pressure (mild 200 to 300, moderate 100 to 200, severe under 100).

Mechanism. Increased respiratory load (obstruction, stiff lungs, effusion, abnormal chest wall), impaired gas exchange (hypoxaemia, hypercapnia), metabolic acidosis and anxiety trigger higher drive and recruit accessory muscles. Fatigue then leads to hypercapnia, acidosis and arrest.

History (brief, from patient, family or ambulance crew).

• Onset and trigger: choking, allergen, sting, new drug or food, trauma, chest pain, palpitations, fever, cough, sputum, haemoptysis, leg swelling, orthopnoea, recent surgery, travel, immobility, diving, altitude, smoke or fumes, near drowning.
• Past history: asthma (previous intubation, admissions, steroid use), chronic obstructive pulmonary disease, heart failure, coronary disease, arrhythmia, immunosuppression, HIV, cancer, neuromuscular disease, sickle cell disease, thromboembolism, pregnancy.
• Drugs: bronchodilators and adherence, beta blockers, ACE inhibitors, opioids, sedatives, anticoagulants, chemotherapy, amiodarone, recreational drugs.
• Allergies and advance care decisions (ceilings of treatment).
• Children: age, feeding, wet nappies, fever, croup, choking, immunisation, prematurity.

Examination (while treating).

• Airway: voice, stridor, drooling, swelling of lips and tongue, secretions, foreign body.
• Breathing, effort: respiratory rate and pattern, tripod position, accessory muscle use, supraclavicular, intercostal and subcostal recession, abdominal paradox, nasal flaring, grunting, ability to complete sentences.
• Breathing, findings: saturation, cyanosis, chest expansion symmetry, percussion, auscultation (wheeze, silent chest, crackles, bronchial breathing, absent breath sounds), tracheal position, surgical emphysema.
• Circulation: pulse rate and rhythm, blood pressure (pulsus paradoxus over 10 mmHg), capillary refill, jugular venous pressure, heart sounds, oedema, calves, signs of shock.
• Disability: consciousness (alert, voice, pain, unresponsive; Glasgow Coma Scale), agitation, drowsiness, flapping tremor, pupils, blood glucose.
• Exposure: temperature, rash, urticaria, burns, trauma, injection marks, medication patches.

Red flags.

• Silent chest, bradypnoea, exhaustion, cyanosis, confusion, drowsiness, bradycardia, hypotension (impending arrest).
• Stridor, drooling, muffled voice, tripod position, swelling of lips and tongue (airway obstruction).
• Tracheal deviation with hyperresonance and hypotension (tension pneumothorax).
• Pleuritic pain, haemoptysis, leg swelling, tachycardia, hypoxia with clear lungs (embolism).
• Wheeze, rash, hypotension after exposure (anaphylaxis).
• Pink frothy sputum, orthopnoea (acute pulmonary oedema).
• Fever, hypotension, mottling (sepsis).
• Trauma with paradoxical chest movement or subcutaneous emphysema.
• Rapidly ascending weakness, bulbar failure.
• Child with grunting, severe recession, head bobbing, cyanosis, silent chest, floppy or irritable.
• Pregnancy or postpartum.

Airway obstruction. Anaphylaxis, angioedema, epiglottitis, croup, foreign body, retropharyngeal abscess, thermal or caustic injury, laryngeal tumour, vocal cord paralysis, tracheal stenosis, obstructive tumour.

Lower airway and lung. Acute asthma, chronic obstructive pulmonary disease exacerbation, bronchiolitis, pneumonia, aspiration, pneumocystis pneumonia, acute respiratory distress syndrome, interstitial lung disease exacerbation, pulmonary embolism, alveolar haemorrhage, inhalational injury, near drowning, transfusion related lung injury, high altitude pulmonary oedema.

Pleural and chest wall. Tension and simple pneumothorax, massive pleural effusion, haemothorax, empyema, rib fractures and flail chest, pulmonary contusion, diaphragm rupture, kyphoscoliosis, abdominal distension.

Cardiac. Acute pulmonary oedema (ischaemia, arrhythmia, valve failure, hypertensive emergency, cardiomyopathy), cardiogenic shock, tamponade, myocarditis, pericardial constriction, congenital heart disease (infants), aortic dissection.

Metabolic and toxic. Diabetic ketoacidosis, salicylate toxicity, toxic alcohols, lactic acidosis, carbon monoxide, cyanide, methaemoglobinaemia, sepsis, severe anaemia, thyroid storm, adrenal crisis, uraemia.

Neuromuscular and central. Guillain-Barre syndrome, myasthenic crisis, botulism, motor neurone disease, spinal cord injury, brainstem stroke, opioid overdose, status epilepticus, raised intracranial pressure.

Psychogenic. Panic attack, hyperventilation syndrome, functional breathing disorder (diagnosis of exclusion).

Neonatal and paediatric specific. Respiratory distress syndrome of prematurity, transient tachypnoea of the newborn, meconium aspiration, group B streptococcal sepsis, congenital diaphragmatic hernia, choanal atresia, tracheo-oesophageal fistula, bronchiolitis, croup, epiglottitis, foreign body, pertussis.

1. Assess and treat simultaneously (airway, breathing, circulation, disability, exposure). Call for senior help and the airway team early.
2. Monitoring: saturation, ECG, blood pressure, respiratory rate, temperature; capillary glucose; intravenous access; bloods; arterial or venous gas with lactate (hypercapnia and acidosis, rising PaCO2, base excess).
3. Immediate bedside tests: 12 lead ECG and peak expiratory flow in asthma if possible.
4. Point of care ultrasound of lung (B lines, lung sliding, effusion, consolidation), heart (function, tamponade, right ventricular strain) and inferior vena cava.
5. Portable chest radiograph (pneumothorax, consolidation, effusion, oedema, foreign body, tube and line position). Do not delay treatment of tension pneumothorax or anaphylaxis for imaging.
6. Blood tests: full blood count, urea, creatinine, electrolytes, liver function, glucose, C reactive protein, procalcitonin, blood cultures, lactate, troponin, natriuretic peptide, D-dimer when appropriate, coagulation, group and screen.
7. Also request toxicology, salicylate, carboxyhaemoglobin and methaemoglobin by co-oximetry, and thyroid function.
8. Once stabilised: CT pulmonary angiography (embolism), CT chest (parenchyma, airway), CT neck (airway), echocardiography, bronchoscopy (airway or foreign body).
9. Acute respiratory distress syndrome work up: identify the trigger (sepsis, pneumonia, aspiration, pancreatitis, trauma, transfusion, drowning). Use echocardiography to exclude cardiogenic oedema. Measure PaO2 to FiO2 ratio and oxygenation index. Consider bronchoalveolar lavage for infection.
10. Neuromuscular failure: forced vital capacity and negative inspiratory force at the bedside; lumbar puncture, nerve conduction, antibodies.
11. Children: weight based estimation, croup and bronchiolitis scores, blood gas, chest radiograph if uncertain. Avoid distressing examination of the throat in suspected epiglottitis.
12. Neonates: chest radiograph, blood gas, glucose, cultures, echocardiography, pre and post ductal saturations.
13. Decide the level of care and ceiling of treatment with the patient or family early.

Limits. Assessment is often by observation alone; do not wait for results. Saturation is a late and unreliable marker of fatigue and can be normal in severe distress on oxygen. PaCO2 may be normal in a tiring asthmatic (a normal or rising PaCO2 is ominous). Silent chest means minimal air movement. Chest radiograph and ultrasound can miss early pneumothorax or embolism. Anxiety may coexist with serious disease.

Immediate priorities (all patients).

• Call for help early; move to resuscitation area; position of comfort (sitting up); stop oral intake; monitor continuously.
• Airway: open and clear (suction, jaw thrust, airway adjuncts). Use heliox 70:30 as a bridge in severe upper airway obstruction or asthma.
• Oxygen: 15 L/min by non rebreather mask for critically ill patients, then titrate to saturation 94% to 98% (88% to 92% in hypercapnic risk, Venturi 24% or 28%).
• Bag and mask ventilation for apnoea or exhaustion.
• High flow nasal oxygen 30 to 60 L/min.
• Continuous positive airway pressure 5 to 10 cmH2O for oedema and obstructive causes.
• Bilevel non invasive ventilation (inspiratory 12 to 20 cmH2O, expiratory 4 to 5 cmH2O) for hypercapnic acidosis and exacerbations of chronic obstructive pulmonary disease.
• Intubate for failure, exhaustion, airway risk or low Glasgow Coma Scale. Use rapid sequence induction by an experienced operator, with preoxygenation.
• Induction: ketamine 1 to 2 mg/kg or etomidate 0.3 mg/kg with rocuronium 1.2 mg/kg or suxamethonium 1.5 mg/kg. Avoid hypotension, and have difficult airway equipment and a cricothyroidotomy kit ready.
• Circulation: intravenous or intraosseous access; fluid bolus 250 to 500 mL for shock unless pulmonary oedema; vasopressors (noradrenaline 0.05 to 0.5 micrograms/kg/minute); treat arrhythmia.
• Treat reversible causes: tension pneumothorax, anaphylaxis, hypoglycaemia, opioid overdose, severe asthma, pulmonary oedema, sepsis.

Specific treatment.

• Anaphylaxis and angioedema: adrenaline 0.5 mg (0.5 mL of 1:1,000) intramuscularly into the anterolateral thigh, repeated every 5 minutes if no response (150 micrograms under 6 years, 300 micrograms 6 to 12 years).
• Give high flow oxygen; 0.9% sodium chloride 500 to 1,000 mL; chlorphenamine 10 mg and hydrocortisone 200 mg intravenously; nebulised salbutamol 5 mg.
• Use nebulised adrenaline 5 mg for upper airway oedema and an adrenaline infusion for refractory shock. Observe for 6 to 12 hours.
• Acute severe asthma: salbutamol 5 mg nebulised continuously or every 15 minutes with ipratropium 500 micrograms every 4 to 6 hours.
• Add prednisolone 40 to 50 mg orally or hydrocortisone 100 mg intravenously every 6 hours, and magnesium sulphate 2 g intravenously over 20 minutes.
• Consider aminophylline 5 mg/kg over 20 minutes (if not on theophylline) then 0.5 mg/kg/hour, and intravenous salbutamol 5 micrograms/minute.
• Intubate with ketamine for exhaustion, using a low rate, long expiratory time and permissive hypercapnia.
• Chronic obstructive pulmonary disease exacerbation: salbutamol 2.5 to 5 mg and ipratropium 500 micrograms nebulised, prednisolone 30 to 40 mg daily for 5 days, controlled oxygen, and non invasive ventilation.
• Antibiotics for chronic obstructive pulmonary disease exacerbation: amoxicillin 500 mg three times daily, or doxycycline 200 mg then 100 mg daily, or co-amoxiclav 625 mg three times daily.
• Tension pneumothorax: immediate needle decompression (14 gauge cannula, second intercostal space mid clavicular line or fifth space anterior axillary line), then chest drain.
• Large simple pneumothorax: aspiration or small bore drain (12 French). Haemothorax: large bore chest drain, resuscitation, thoracic surgery.
• Acute pulmonary oedema: sit up; furosemide 40 to 80 mg intravenously; glyceryl trinitrate infusion 10 to 200 micrograms/minute if systolic pressure over 110 mmHg; continuous positive airway pressure.
• Also treat ischaemia (aspirin 300 mg, anticoagulation, revascularisation), arrhythmia and hypertensive crisis. Avoid routine morphine.
• Pulmonary embolism: unfractionated heparin 80 units/kg bolus then 18 units/kg/hour, or enoxaparin 1 mg/kg twice daily, or rivaroxaban 15 mg twice daily for 21 days then 20 mg daily.
• For shock, give alteplase 100 mg over 2 hours (10 mg bolus then 90 mg over 2 hours). Consider catheter directed treatment or surgical embolectomy.
• Pneumonia and sepsis: give antibiotics within 1 hour (co-amoxiclav 1.2 g every 8 hours with clarithromycin 500 mg twice daily, or ceftriaxone 2 g daily; piperacillin-tazobactam 4.5 g every 6 hours if hospital acquired).
• Also give 30 mL/kg crystalloid for hypotension, achieve source control, and use vasopressors. Give corticosteroids for severe community acquired pneumonia or COVID-19 with hypoxia (dexamethasone 6 mg daily for up to 10 days).
• Acute respiratory distress syndrome: treat the trigger.
• Use lung protective ventilation (tidal volume 6 mL/kg ideal body weight, plateau pressure under 30 cmH2O, positive end expiratory pressure titrated, driving pressure under 15 cmH2O).
• Prone positioning for 16 hours a day when PaO2 to FiO2 ratio is under 150. Conservative fluid strategy after resuscitation. Neuromuscular blockade (cisatracurium) for severe early disease.
• Dexamethasone 20 mg daily for 5 days then 10 mg daily for 5 days in moderate to severe disease. Refer for extracorporeal membrane oxygenation in refractory cases. Avoid excess sedation.
• Upper airway obstruction: call anaesthesia and ENT; give humidified oxygen, nebulised adrenaline 5 mg, dexamethasone 8 to 10 mg intravenously and heliox; early surgical airway if needed.
• Foreign body: back blows and abdominal thrusts, laryngoscopy and Magill forceps, rigid bronchoscopy.
• Croup: dexamethasone 0.15 mg/kg once, nebulised adrenaline 0.4 mL/kg of 1:1,000 (maximum 5 mL).
• Bronchiolitis: oxygen, hydration, nasal suction, high flow oxygen, no routine bronchodilators.
• Neuromuscular failure: elective intubation when forced vital capacity is under 15 to 20 mL/kg, with immunoglobulin 0.4 g/kg daily for 5 days (Guillain-Barre syndrome) or plasma exchange (myasthenic crisis).
• Diabetic ketoacidosis: 0.9% sodium chloride 1 litre over 1 hour, fixed rate insulin 0.1 units/kg/hour, potassium replacement.
• Salicylate poisoning: sodium bicarbonate 1.5 mg/kg, haemodialysis. Carbon monoxide: 100% oxygen, hyperbaric oxygen for severe cases. Cyanide: hydroxocobalamin 5 g intravenously.
• Opioid overdose: naloxone 400 micrograms intravenously repeated every 2 to 3 minutes, then infusion. Methaemoglobinaemia: methylene blue 1 to 2 mg/kg.
• Flail chest and chest trauma: analgesia (regional block, epidural), oxygen, positive pressure support, drainage of haemothorax or pneumothorax.
• Neonatal respiratory distress syndrome: continuous positive airway pressure, surfactant (poractant alfa 200 mg/kg), antenatal corticosteroids (betamethasone 12 mg intramuscularly twice 24 hours apart before 34 weeks), caffeine citrate for apnoea.
• Congenital diaphragmatic hernia: intubate, avoid bag and mask, nasogastric decompression. Duct dependent heart disease: alprostadil 0.01 to 0.05 micrograms/kg/minute.
• Panic and functional distress: only after exclusion of organic disease. Give calm explanation and coached breathing. Avoid benzodiazepines in unexplained distress without monitoring.
• Palliative distress in end of life care: opioids (morphine 2.5 mg subcutaneously every 4 hours as needed), benzodiazepines for anxiety (midazolam 2.5 mg), fan, positioning, oxygen if hypoxic, antisecretory (hyoscine butylbromide 20 mg subcutaneously).

Disposition.

• Critical care: severe distress, impending arrest, need for ventilation, shock, acute respiratory distress syndrome, severe asthma, tension pneumothorax after decompression, airway obstruction, neuromuscular failure, neonates with distress.
• High dependency or monitored ward: moderate distress needing non invasive support, oxygen requirement, pneumonia with CURB-65 of 3 or more, embolism with strain, acute heart failure.
• Admit all new moderate to severe distress. Use a short stay unit for mild asthma or croup with full response. Discharge only when stable, on room air, with follow up.

Monitoring. Continuous saturation, ECG, respiratory rate, heart rate, blood pressure. Repeat gas 30 to 60 minutes after any change and in ventilated patients every 4 to 6 hours. Also monitor PaO2 to FiO2 ratio, fluid balance, vital capacity, chest radiograph after procedures, ventilator pressures, pain and sedation scores and early warning score. Repeat assessment every 15 minutes in the first hour.

Referral and escalation. Critical care and anaesthesia; respiratory; cardiology; ENT and thoracic surgery; toxicology; neurology; paediatric intensive care and neonatology; palliative care for end of life; retrieval service when intensive care is not available locally.

Safety netting. After discharge, return by emergency services for breathlessness at rest, inability to speak in sentences, blue lips, silent chest, stridor, chest pain, confusion or exhaustion. Provide written action plans for asthma and chronic obstructive pulmonary disease, adrenaline auto-injector training, inhaler technique, vaccination and smoking cessation.

Special groups.

• Children: weight based doses, age specific rates, grunting and recession as markers of severity. Do not examine the throat in suspected epiglottitis. Keep the parent close. Give oxygen without distressing the child.
• Neonates: temperature control, glucose, sepsis cover (benzylpenicillin 50 mg/kg and gentamicin 5 mg/kg).
• Pregnancy: left lateral tilt, oxygen to keep saturation over 95%, embolism, amniotic fluid embolism, peripartum cardiomyopathy, pulmonary oedema from tocolytics or magnesium, aspiration. Use the usual regimens. Plan perimortem caesarean at 4 minutes in arrest.
• Older adults: atypical presentation, multiple causes, treatment ceilings, delirium.
• Immunosuppressed: pneumocystis pneumonia (co-trimoxazole 120 mg/kg/day in divided doses for 21 days with prednisolone), fungal infection, cytomegalovirus.
• Trauma: tension pneumothorax, haemothorax, flail chest, tamponade. High altitude and diving: pulmonary oedema, decompression illness.
• Endemic regions: severe malaria with respiratory distress, tuberculosis, pneumonia, rheumatic heart disease, snake bite neurotoxicity, organophosphate poisoning (atropine 2 mg intravenously every 5 minutes until secretions dry, pralidoxime) and sickle cell acute chest syndrome are common.