How to test for Hypoxia (HX)?

From the Guidelines

To test for hypoxaemia (HX), pulse oximetry should be used to measure arterial oxygen saturation (SpO2) as the initial assessment tool. This is based on the British Thoracic Society (BTS) guideline for oxygen use in adults in healthcare and emergency settings 1. The guideline recommends that general practitioners (GPs) or first responders visiting a patient’s home should carry a portable pulse oximeter to assess hypoxaemia and guide use of oxygen if available.

Key Assessment Points

• The medical history should be taken when possible in an acutely breathless patient and may point to the diagnosis of a particular acute illness such as pneumonia or pulmonary embolism or an exacerbation of a chronic condition such as COPD, asthma or heart failure 1.
• Physical examination should be undertaken urgently to provide evidence of a specific diagnosis such as heart failure or a large pleural effusion 1.
• Record arterial oxygen saturation measured by pulse oximetry (SpO2) and consider blood gas assessment in patients with unexplained confusion and agitation as this may be presenting feature of hypoxaemia and/or hypercapnia 1.

Testing for Hypoxaemia

• Pulse oximetry is a non-invasive and quick method to assess oxygen saturation, and it should be used continuously until the patient is stable or arrives at hospital for a full assessment 1.
• If a patient has a clear history of asthma or heart failure or other treatable illness, appropriate treatment should be instituted in accordance with guidelines or standard management plans for each disease 1.
• Blood gas estimations should be used to assess patients with a clinical exacerbation associated with a 3% or greater fall in oxygen saturation on their usual oxygen therapy 1.

Important Considerations

• Never discontinue oxygen therapy to obtain an oximetry measurement on room air in patients who clearly require oxygen therapy 1.
• The oxygen concentration should be adjusted upwards or downwards to maintain the target saturation range, and the oxygen saturation should be monitored continuously until the patient is stable or arrives at hospital for a full assessment 1.

From the Research

Testing for HX

There are no direct references to testing for HX in the provided studies. However, some studies mention testing and assessment methods for related conditions:

• The study 2 discusses the use of rivaroxaban, a direct factor Xa inhibitor, for the prevention and treatment of thromboembolic disorders.
• The study 3 reviews the usefulness of Complete Blood Count (CBC) to assess cardiovascular and metabolic diseases, but does not mention testing for HX specifically.
• The study 4 provides updated guidelines for outpatient management of anticoagulation therapy, including the use of direct oral anticoagulants, but does not mention testing for HX.

Some key points to consider:

• The study 3 highlights the importance of CBC components, such as white blood cell count, neutrophil-to-lymphocyte ratio, and platelet count, in predicting cardiovascular disease and metabolic disorders.
• The study 4 recommends validated bleeding risk assessments, such as HAS-BLED, to be performed at each visit for patients on anticoagulation therapy.
• There is no direct evidence to support a specific testing method for HX, and further research may be needed to determine the best approach.