Respiratory arrest

Respiratory arrest is the absence of effective breathing while a central pulse is still present. Hypoxaemia and hypercapnia follow within seconds to minutes, and hypoxic bradycardia and cardiac arrest follow if ventilation is not restored.

Recognition. No breathing or only agonal gasps, no chest rise, unresponsive or drowsy, and a palpable carotid pulse (brachial in infants).

Mechanisms.

• Central: depressed respiratory drive from drugs, brainstem injury or raised intracranial pressure.
• Neuromuscular: failure of the nerve, junction or respiratory muscle, or a high cervical spinal cord lesion.
• Upper airway obstruction: tongue, foreign body, swelling, laryngospasm.
• Lower airway and parenchymal: severe bronchospasm, pulmonary oedema, consolidation, ventilation failure from exhaustion.
• Pleural and chest wall: tension pneumothorax, large haemothorax, flail chest.

Temporal patterns. Sudden: opioids, obstruction, anaphylaxis, drowning, seizures. Progressive: asthma, chronic obstructive pulmonary disease, Guillain-Barre syndrome and myasthenic crisis, where exhaustion follows hours to days of failure.

Key distinctions. Respiratory arrest is not respiratory failure. In failure there is effort but inadequate gas exchange. In arrest effort is absent or ineffective. A patient with a pulse and apnoea is ventilated before anything else, whereas a patient without a pulse is in cardiac arrest.

Immediate. Check responsiveness, open the airway, look, listen and feel for breathing and check the carotid pulse together for up to 10 seconds. If no pulse, begin compressions. If a pulse is present, ventilate.

History from witnesses. Choking, drowning, overdose, injection or medicine taken, anaphylaxis trigger, asthma or chronic lung disease, neuromuscular disease, recent surgery or anaesthesia, head or neck injury, stroke, seizure, sedatives, alcohol, snake bite, farm chemicals or pesticide, and time of onset.

Examination.

• Airway: snoring, gurgling, stridor, swelling of lips, tongue and face, burns, blood, vomit, neck wound.
• Breathing: chest rise, symmetry, air entry, wheeze or silent chest, tracheal position, crackles, subcutaneous emphysema.
• Pupils (pinpoint with opioids), skin (urticaria, cyanosis, needle marks), muscle tone, reflexes, signs of trauma, temperature.
• Saturation (unreliable in shock, carbon monoxide poisoning and poor perfusion) and capnography.

Red flags (impending respiratory arrest).

• Exhaustion, drowsiness or confusion, silent chest, paradoxical breathing, inability to speak.
• Falling respiratory rate (under 8 breaths/min) after a period of high rate.
• Saturation under 90% on high flow oxygen, PaCO2 over 6.5 kPa with pH under 7.30.
• Bradycardia in a child, or hypotension.
• Single breath count under 10 and vital capacity under 20 mL/kg in neuromuscular disease.

Central depression.

• Opioid poisoning, benzodiazepine poisoning, barbiturate poisoning, alcohol intoxication, gamma-hydroxybutyrate poisoning.
• Brainstem stroke, traumatic brain injury, raised intracranial pressure, status epilepticus and post-ictal state.
• Hypoglycaemia, hypothermia, myxoedema coma, hypercapnic respiratory failure with carbon dioxide narcosis.

Neuromuscular. Guillain-Barre syndrome, myasthenic crisis, botulism, tick paralysis, organophosphate poisoning, neurotoxic snake envenomation, high cervical spinal cord injury, motor neurone disease, hypokalaemic periodic paralysis, severe hypophosphataemia, residual neuromuscular blockade.

Upper airway. Foreign body airway obstruction, anaphylaxis, angioedema, epiglottitis, retropharyngeal abscess, Ludwig angina, inhalation burn, croup, upper airway tumour, bilateral vocal cord paralysis, laryngospasm, obstructive sleep apnoea with sedation.

Lower airway, parenchymal and pleural. Severe asthma, chronic obstructive pulmonary disease, bronchiolitis, aspiration pneumonitis, pneumonia, cardiogenic pulmonary oedema, acute respiratory distress syndrome, pulmonary embolism, tension pneumothorax, haemothorax, flail chest, drowning.

Circulatory and metabolic. Evolving cardiac arrest, shock, diabetic ketoacidosis with exhaustion.

Mimics. Syncope, post-ictal apnoea with recovery, functional unresponsiveness.

Treat first; investigate while ventilating.

Immediate tests. Saturation and waveform capnography, capillary glucose, arterial blood gas with lactate (pH, PaCO2, PaO2, bicarbonate), ECG, and continuous cardiac monitoring.

Interpretation. PaCO2 over 6.5 kPa with pH under 7.30 is acute respiratory acidosis. PaO2 under 8 kPa on oxygen is severe hypoxaemia. An end tidal CO2 trace that is flat or absent after intubation means the tube is not in the trachea or there is no circulation.

Targeted tests after stabilisation.

• Chest radiograph and bedside ultrasound for pneumothorax, effusion, pulmonary oedema and consolidation.
• Full blood count, urea, creatinine, electrolytes, phosphate, magnesium, creatine kinase, liver tests, carboxyhaemoglobin, paracetamol and salicylate levels, toxicology and blood cultures as indicated. Mast cell tryptase within 1 to 2 hours of onset with a baseline at 24 hours for suspected anaphylaxis.
• Neuromuscular disease: forced vital capacity (intubation threshold under 20 mL/kg, or a fall of 30% or more), maximum inspiratory pressure less negative than 30 cm H2O, maximum expiratory pressure under 40 cm H2O. Then lumbar puncture, nerve conduction studies, acetylcholine receptor antibodies and MRI of the spine as directed.
• CT head when central causes are unclear, CT chest and CT pulmonary angiography for suspected parenchymal or vascular disease, and laryngoscopy for suspected upper airway pathology.

Limitations. Saturation lags and may read falsely high with carbon monoxide. Blood gases confirm but must never delay ventilation. Bedside spirometry is unreliable in a patient who cannot cooperate.

Airway. Head tilt and chin lift, or jaw thrust if neck injury is possible. Suction. Oropharyngeal airway sized from the corner of the mouth to the angle of the jaw. Nasopharyngeal airway if the jaw is clenched (avoid with suspected skull base fracture).

Ventilation.

• Bag valve mask with two person technique and 100% oxygen at 15 L/min. Adults: 1 breath every 6 seconds (10 breaths/min), each over 1 second, to visible chest rise (about 6 to 8 mL/kg of ideal body weight). Avoid hyperventilation and gastric inflation.
• Reassess the pulse every 2 minutes. Begin compressions if the pulse is lost, or in a child if the pulse is under 60/min with poor perfusion despite oxygenation.
• Once oxygenated, titrate to saturation 94 to 98% (88 to 92% in those at risk of hypercapnic failure).

Advanced airway. Preoxygenate. Confirm placement with waveform capnography. A patient who is deeply unresponsive with no tone may need no drugs. For a patient with tone:

• Ketamine 1 to 2 mg/kg IV (0.5 to 1 mg/kg in shock) or etomidate 0.3 mg/kg IV, single dose; monitor blood pressure, which may fall.
• Rocuronium 1.2 mg/kg IV, single dose, or suxamethonium 1.5 mg/kg IV, single dose. Avoid suxamethonium with hyperkalaemia, burns or crush injury beyond 24 hours, denervation, neuromuscular disease, prolonged immobility and personal or family malignant hyperthermia. Sugammadex 16 mg/kg IV reverses rocuronium in a failed airway.
• Failed intubation and failed ventilation: front of neck access by scalpel cricothyroidotomy.
• Ventilator settings: tidal volume 6 to 8 mL/kg ideal body weight, rate 12 to 16 breaths/min, PEEP 5 cm H2O, titrate oxygen. In severe asthma use a rate of 8 to 10 breaths/min with a long expiratory time.

Cause directed treatment.

• Opioid poisoning: ventilate first, then naloxone 0.4 mg IV, repeated every 2 to 3 minutes; use 0.04 to 0.1 mg increments in chronic opioid users; titrate to respiratory rate over 10 breaths/min; maximum about 10 mg before the diagnosis is reconsidered; naloxone lasts 20 to 90 minutes, shorter than most opioids, so consider an infusion of about two thirds of the reversal dose each hour; observe for at least 2 hours after the last dose and up to 6 hours after long acting or modified release opioids and methadone.
• Benzodiazepine oversedation (iatrogenic only): flumazenil 0.2 mg IV over 15 seconds, then 0.1 mg every 60 seconds; maximum 1 mg in one course; avoid in mixed overdose, epilepsy and long term benzodiazepine use.
• Anaphylaxis: adrenaline 0.5 mg IM (0.5 mL of 1 mg/mL) into the anterolateral thigh, repeated every 5 minutes if there is no improvement; children: 150 micrograms under 6 years, 300 micrograms at 6 to 12 years; monitor ECG, blood pressure and saturation; start an adrenaline infusion for refractory shock; observe for biphasic reactions.
• Severe asthma: salbutamol 5 mg nebulised, repeated every 15 to 20 minutes or given continuously; ipratropium 500 micrograms nebulised every 20 minutes for 3 doses; hydrocortisone 100 mg IV; magnesium sulphate 2 g IV over 20 minutes (single dose; monitor blood pressure and reflexes). Adrenaline 0.5 mg IM if anaphylaxis is possible.
• Foreign body: 5 back blows then 5 abdominal thrusts (chest thrusts in pregnancy and obesity; back blows and chest thrusts only in infants), then laryngoscopy and Magill forceps.
• Tension pneumothorax: immediate decompression in the fifth intercostal space and a chest drain.
• Hyperkalaemia with paralysis: calcium chloride 10% 10 mL IV over 2 to 5 minutes, then insulin and glucose and salbutamol.
• Organophosphate poisoning: atropine 2 mg IV, doubling every 5 minutes until secretions dry, the chest clears, heart rate is over 80 beats/min and systolic pressure is over 80 mmHg; remove contaminated clothing and protect staff.
• Neuromuscular disease: Guillain-Barre syndrome or myasthenic crisis: intravenous immunoglobulin 0.4 g/kg daily for 5 days, or plasma exchange (5 sessions of 200 to 250 mL/kg over 1 to 2 weeks); avoid suxamethonium, aminoglycosides, macrolides, fluoroquinolones, magnesium and beta blockers in myasthenia.
• Neurotoxic snake bite: ventilate until paralysis resolves and give antivenom from the product label, with limb immobilisation.
• Drowning: 5 initial rescue breaths with 100% oxygen.
• Magnesium toxicity (after eclampsia treatment): calcium gluconate 10% 10 mL (1 g) IV over 10 minutes.

Special groups. Children: 12 to 20 breaths/min (1 breath every 3 to 5 seconds), 5 initial breaths, brachial pulse in infants, weight based drug doses. Pregnancy: left lateral tilt, high aspiration and difficult airway risk, early senior anaesthetic help. Obesity: ramped position. Older adults: lower sedative doses.

Monitoring. Continuous saturation, waveform capnography, ECG and blood pressure. Gas at 30 to 60 minutes after ventilation starts and as clinically needed. Pupils, Glasgow Coma Scale, urine output.

Referral and escalation. Critical care for all patients. Anaesthesia for difficult airway. Neurology for neuromuscular disease. Toxicology or poison centre for overdose. Surgery or ENT for obstructing lesions. Psychiatry after intentional overdose.

Admission criteria. Every patient needs critical care admission. Opioid reversal alone may allow observation in a monitored area after full recovery.

Discharge and safety netting. Discharge only after full recovery with the cause treated or understood. Provide naloxone supply and training for opioid users, an anaphylaxis plan with two adrenaline auto-injectors for allergic causes, and asthma and neuromuscular action plans. Patients and families are told to call emergency services at once for breathlessness, noisy breathing, blue lips or drowsiness.