Let’s define some terms:
- Respiratory failure is when our respiratory system is unable to maintain sufficient gas exchange leading to hypoxaemia (PaO2 < 60mmHg) or hypercapnia (PaCO2 >50mmHg), and these may happen together. It may happen chronically or acutely.
- Respiratory distress is a clinical syndrome associated with breathing disorders.
- Respiratory arrest is when we have a complete cessation of breathing in patients with a pulse.
Pathophysiology
Disruption of gas exchange > 5 minutes can lead to irreversible damage to vital organs, especially the brain. Respiratory arrest almost always is followed by cardiac arrest unless we restore our respiratory function.
Respiratory arrest may be caused by:
- Airway obstruction
- Upper airway obstruction - may occur in infants <3 months old, secondary to nasal blockage (as they are predominantly nasal breathers). At any age, displacement of the tongue into the oropharynx can also cause obstruction. Blood, mucus, vomit, foreign body, spasm, tumour, trauma and pharyngolaryngeal tracheal inflammation are other causes.
- Lower airway obstruction - due to aspiration, bronchospasm, pneumonia, pulmonary oedema, pulmonary haemorrhage, drowning.
- Decreased respiratory effort - this is due to CNS impairment (disorders of the CNS, drug adverse effects, or metabolic disorder). Disorders that affect the brainstem (location of respiratory center) can lead to hypoventilation, hypoglycaemia.
- Respiratory muscle weakness - due to fatigue or neuromuscular disorders (myasthenia gravis, botulism, poliomyelitis, GBS) and NMJ blocking drugs (-curiums and -curoniums).
😷 Presentation
- Cyanosis
- Gasping and paradoxical breathing
- Agitation, confusion, dyspnoea may be present in patients with impending pulmonary arrest.
- Tachycardia
- Diaphoresis (excessive sweating)
- Intercostal and sternoclavicular retractions
🔍 Investigations
Clinically, it is obvious. Look, listen and feel is all that is needed before treatment is started and we use our ABCDE approach as always.
We do need to ensure that there is no foreign body obstruction. If it is present there will be resistance to ventilation, or it may be discovered with laryngoscopy when using endotracheal intubation.
We want to know if the patient is hypoglycaemic or if they have had any drugs administered as these are reversible causes.
🧰 Management
- Mechanical ventilation
Clearing airway obstruction
- Flex the neck to elevate the head until external acoustic meatus is on the same plane as the sternum and the face is parallel to the ceiling.
- Heimlich maneuver (subdiaphragmatic abdominal thrusts) or chest trusts in pregnant or extremely obese patients. To perform these the rescuer stands behind the patients, arms encircling the midsection. One fist is clenched and placed halfway between the umbilicus and xiphoid process. The other hand lies on top of the fist and both arms are pulled inwards and upwards. If the patient is unconscioius, CPR is performed.
- Infants <1 year should be held in a prone, head-down position. The rescuer needs to support the head and deliver 5 back blows, followed by 5 chest thrusts in a head-down position and the back resting on the thigh.
- Establishing an alternate airway - such as in a cricothryoidotomy.