Chapter 11. Respiratory emergencies
Respiratory emergencies are a frequent part of the workload of a pre-hospital clinician. The following definitions are important in managing patients with respiratory problems:
• Hypoxaemia – inadequate oxygenation of the blood
• Hypoxia – inadequate oxygenation of the body
• Hypercarbia – high level of carbon dioxide in the blood, leads to acidaemia
• Acidaemia – where the blood becomes excessively acid (low pH), the body’s immediate response is to increase the respiratory rate (tachypnoea)
• Tachypnoea – a raised respiratory rate (usually >30 breaths/min)
• Hyperventilation – excessive breathing rate. In the absence of acidaemia will cause symptoms such as tingling around the lips and carpo-pedal spasm (seen in panic attacks).
Asthma
Approximately 1000 people die in the UK each year from this condition, so never underestimate the severity of an asthma attack. Individuals susceptible to other atopic disorders such as eczema, are more prone to developing asthma. There also appears to be a familial element.
Generalised airway obstruction is caused by:
• Inflammation of the airway passages, leading to oedema and swelling
• Increased production of thick mucus, leading to plugging of bronchioles
• Generalised bronchial smooth muscle constriction, leading to bronchospasm.
Precipitating causes of an acute exacerbation of asthma include:
• Exercise
• Infection
• Allergy to drugs or other substances
• Emotional upset.
Be especially cautious with patients who have a previous history of near-fatal asthma, with previous hospital admission or even a previous stay on intensive care for their asthma. These patients are sometimes referred to as ‘brittle’ asthmatics.
Life-threatening deterioration of an asthma attack may be very rapid.
Use of the peak flow meter
The patient’s peak expiratory flow rate (PEFR) is a useful predictor of the severity of an attack, particularly if the patient knows the value of their usual/normal PEFR. A predicted PEFR can be calculated if necessary, although the patient or parent (if the patient is a child) will often know it.
In rare cases, asthmatic patients develop spontaneous pneumothorax as a result of a ruptured bulla (lung cyst). They may also develop subcutaneous emphysema in the neck and anterior chest wall.
The differential diagnosis of a severe asthma attack includes pulmonary oedema, anaphylaxis, pneumothorax and airway obstruction.
Beware the asthma patient with a silent chest.
Management of asthma
• Maintain an air of calm
• Take a rapid history, including recent episodes and current treatment
• If the patient is unable to give a history, do not delay transfer to hospital
• Measure a PEFR if possible
• If severe or life-threatening features are present, or the patient does not respond to treatment, then warn the receiving hospital of your impending arrival.
Patients with severe or life-threatening asthma may not appear distressed or have all of these features. Make the diagnosis if any feature is present.
Prehospital treatment of severe and life-threatening asthma
The aim of emergency treatment is to reverse hypoxia with oxygen and reduce bronchospasm using β2-adrenoreceptor agonists. Oral or intravenous steroid therapy has no effect for at least 4 hours.
Adults
• Oxygen, high flow via a reservoir mask (10–15 L/min)
• Salbutamol 5 mg via an oxygen-driven nebuliser, repeated as necessary
• Intravenous access (consider crystalloid infusion if dehydrated)
• Hydrocortisone 200 mg IV
• ECG monitoring
• Immediate evacuation to hospital.
If the asthma is severe or life-threatening, ipratropium 0.5 mg should be added to the nebuliser.
Children
Buy Membership for Emergency Medicine Category to continue reading. Learn more here
