Acute respiratory failure results from acute or chronic impairment of gas exchange between the lungs and the blood causing hypoxia with or without hypercapnia.
Patients may present with shortness of breath, anxiety, confusion, tachypnoea, cardiac dysfunction, and cardiac arrest. Central nervous system depression can occur as a result of lack of oxygenation of the blood and vital organs or excessive accumulation of carbon dioxide.
Pulse oximetry, chest x-rays, blood gas analysis, and end-tidal carbon dioxide monitoring (capnometry) are key diagnostic tests.
Management involves first ensuring that the upper airway is patent and clear of obstructions. Supplemental oxygenation and ventilatory support are likely to be required, with immediate attention to the underlying cause or causes for respiratory failure.
Endotracheal intubation and mechanical ventilation are employed when other less invasive manoeuvres have failed.
This topic covers acute respiratory distress in patients over the age of 12 years.
Acute impairment in gas exchange between the lungs and the blood causing hypoxia with or without hypercapnia (e.g., caused by acute decompensation of chronic pulmonary disease). Hypoxic respiratory failure (type I respiratory failure) is hypoxia without hypercapnia and with an arterial partial pressure of oxygen (PaO₂) of <8 kPa (<60 mmHg) on room air at sea level. Hypercapnic respiratory failure (type II respiratory failure) is hypoxia with an arterial partial pressure of carbon dioxide (PaCO₂) of >6.5 kPa (>50 mmHg) on room air at sea level.
History and exam
Key diagnostic factors
- presence of risk factors
- direct trauma to the thorax and neck
- accessory breathing muscle use
- inability to speak
- retraction of intercostal spaces
- loss of airway/gag reflex
Other diagnostic factors
- cardiac rhythm disturbances
- underlying neuromuscular disorder
- drug use
- cigarette smoking
- young age
- older age
- pulmonary infection
- chronic lung disease
- upper airway obstruction
- lower airway obstruction
- alveolar abnormalities
- perfusion abnormalities
- cardiac failure
- peripheral nerve abnormalities
- muscle system abnormalities
- opioid and sedative medicines
- toxic fumes and gases
- traumatic spinal injury
- traumatic thoracic injury
- central nervous system (CNS) disorders
- acute vascular occlusion
- pulmonary effusion
- hypercoagulable states
1st investigations to order
- pulse oximetry
- arterial blood gases
Investigations to consider
- serum bicarbonate (HCO₃)
- chest x-ray
- pulmonary function tests
- Urine or serum toxicology
- chest CT
- CT pulmonary angiography (CTPA)
- ventilation/perfusion lung scan
- cardiothoracic ultrasound
- transcutaneous CO₂ monitoring
no acute upper airway obstruction: stable
no acute upper airway obstruction: unstable
- Hyperventilation secondary to metabolic acidosis
- Hyperventilation secondary to anxiety
- Sleep apnoea
- Guideline for oxygen use in adults in healthcare and emergency settings
- Official ERS/ATS clinical practice guidelines: noninvasive ventilation for acute respiratory failure
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