Emergency Medicine - Acute respiratory failure

GPs face acute situations where an informed approach can improve outcomes. By Dr Chris Bassford.

Life threatening pneumonia should be treated with antibiotics in the community
Life threatening pneumonia should be treated with antibiotics in the community

The acutely breathless patient is one of the most stressful situations that a GP can face. The combination of acute disease, a frightened patient, worried relatives and an anxious practitioner may result in a situation that can compromise patient care.

A GP who has an informed approach to acute respiratory failure can undertake prompt and focused initial management, and reassure those involved that the best possible outcome can be obtained.

Initial assessment
At first contact with the patient, a calm and prompt assessment of the severity of the respiratory failure is essential. It is possible to take a short history of the speed of onset and duration of symptoms, as well as associated symptoms and past history, while simultaneously performing a focused examination.

This should include respiratory rate, pattern and depth of respiration, pulse rate and rhythm, BP and an estimation of peripheral perfusion.

Further history details and a full examination including auscultation can occur at the same time as the initiation of supportive care and summoning and waiting for help.

Supportive care
In an emergency situation the traditional medical model of presentation, history, examination, investigation, diagnosis and treatment is replaced by a pragmatic model where supportive care is started immediately after an initial assessment, and continued while a diagnosis is made and definitive therapy initiated.

In acute respiratory failure supportive care usually involves giving oxygen. Guidelines recommend that all primary care centres have emergency oxygen and pulse oximetry monitoring. But oxygen delivery itself can be a source of concern as it may cause harm in patients at risk of hypercapnoea. How much oxygen to give can be summed up simply: give enough.

For critically ill patients, high flow oxygen via a face mask with a reservoir bag should be given immediately, while waiting for emergency assistance. In other patients, peripheral blood oxygen saturations should be used to titrate therapy.

If levels are above the target saturation then oxygen delivery should be reduced. Normal target saturations are 94-98 per cent in patients who are not at risk of hypercapnoea.

In patients known to have COPD or some other predisposition to hypercapnoea, such as neuromuscular weakness or morbid obesity, a target saturation of 88-92 per cent should be used.

Supportive care for the patient also involves providing reassurance. Keeping calm is important for both practitioner and patient. An overlay of anxiety will exacerbate symptoms and make ventilation less effective by increasing dead-space ventilation.

Making the diagnosis
Examination and investigations can be misleading in respiratory failure. The most valuable tool for diagnosis is the recent and past medical history, but even this can be confused.

Risk factors that lead to COPD also lead to heart disease, so a smoker may present with COPD, acute pulmonary oedema, a pulmonary embolus, or any combination of these.

Dilemmas in making a single diagnosis can lead to hesitancy in initiating therapy, and a less beneficial outcome for the patient. A sensible, pragmatic and necessary approach in some patients is to give therapy simultaneously for pulmonary oedema as well as an infective exacerbation of COPD.

Remember that breathlessness is also a symptom of metabolic acidosis, and consideration of diagnoses outside the bounds of the thorax is worthwhile.

Definitive treatment
Except in the case of a tension pneumothorax, pre-hospital care of respiratory failure is primarily pharmacological. The aim is to reduce lung water, reduce lung inflammation and/or fight infection, and increase gas movement.

In acute cardiogenic pulmonary oedema, a decrease in lung water is achieved mainly by decreasing pulmonary vascular pressure. Loop diuretics are frequently used and act not only as diuretics but as venodilators that reduce right ventricular preload.

Glyceryl trinitrate should also be used in severe cases, but patients with low BP from cardiogenic or distributive shock may be harmed by vasodilator therapy, so care must be taken.

For patients with infection, early administration of antibiotics is thought to improve outcomes. Although they may lead to difficulties with microbiological tests, British Thoracic Society guidelines state that if life-threatening features are present in patients with pneumonia, then antibiotics aimed at pneumoniae species should be started in the community.

Using the CRB-65 severity assessment score to assess patients with suspected pneumonia is useful (see box below).

The acute inflammation in asthma and COPD needs prompt administration of steroids. Oral or IV routes are equally effective and a dose of 40-50mg oral prednisolone or 100mg IV hydrocortisone is usual.

To improve gas movement, airway inflammation and bronchoconstriction must be treated. Where relevant this means steroids and inhaled or nebulised bronchodilators.

Beta-adrenoreceptor agonists are effective broncho-dilators and while also having anti-inflammatory properties, and may help to reduce extravascular lung water. In an emergency setting, nebulisers should be driven by oxygen rather than air, unless harm would arise from this.

In-depth guidelines for most respiratory situations are available on the British Thoracic Society website (www.brit-thoracic.org.uk).

  • Dr Bassford is a specialist registrar and clinical lecturer in respiratory medicine at Birmingham Heartlands Hospital
CRB-65 scoring
  • Confusion - recent onset
  • Respiratory rate ≥ 30 breaths/minute
  • BP systolic ≤ 90 mm/Hg or diastolic ≤ 60 mm/Hg
  • 65 years of age or older

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