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Some causes are not amenable to preventive measures. Monitoring of at-risk patients with capnography is appropriate in some situations (eg in an Intensive Care Unit, intraoperatively and in the Recovery Room) and will allow earlier detection of a problem.
The end-tidal pCO2 is typically lower than the arterial pCO2 and the difference between these values is an index of the magnitude of the alveolar dead space. So if the end-tidal pCO2 is elevated then the arterial pCO2 is usually even more elevated.
First Key Fact: Watch for inadequate alveolar ventilation
Inadequate alveolar ventilation is the underlying problem in nearly all patients so any patient who could have impaired ventilation is at risk of developing respiratory acidosis. So recognise these at-risk situations.
Second Key Fact: Give oxygen to avoid hypoxaemia
Inadequate ventilation will also necessarily affect arterial oxygenation so steps to avoid, recognise and/or treat arterial hypoxaemia are very important. The simple measure of providing supplemental oxygen by face mask to patients can often correct or prevent hypoxaemia.
Some particular medical situations where prevention can be utilised are:
- Better airway care and attention to safe positioning of cerebrally obtunded patients (ie prevent airway obstruction).
- Increased care in the use of drugs (such as CNS sedatives or opiate drugs) which can depress ventilation
- Increased attention to the care of patients at risk of aspiration (eg unconscious patients)
- Ensuring adequate reversal of neuromuscular relaxants