What is the appropriate workup for hypoxia (low oxygen levels)?

From the Guidelines

A hypoxia workup should begin with immediate oxygen supplementation, using a reservoir mask at 15 L/min if the initial SpO2 is below 85%, or nasal cannulae at 2–6 L/min or simple face mask at 5–10 L/min, while investigating the underlying cause, as recommended by the BTS guideline for oxygen use in adults in healthcare and emergency settings 1. The initial assessment should include a thorough history and physical examination, focusing on respiratory, cardiac, and neurological systems.

• Order arterial blood gas analysis to determine the severity and type of hypoxemia (e.g., hypoxemic vs. hypercapnic respiratory failure) 1.
• Obtain a chest X-ray to identify pulmonary pathologies such as pneumonia, pulmonary edema, pneumothorax, or pleural effusions.
• Complete blood count may reveal anemia or infection, while basic metabolic panel can identify metabolic disturbances.
• Consider an electrocardiogram and cardiac enzymes to rule out cardiac causes.
• Pulmonary function tests help diagnose obstructive or restrictive lung diseases.
• For suspected pulmonary embolism, order a D-dimer test followed by CT pulmonary angiography if elevated.
• Echocardiography is useful for evaluating cardiac function and detecting right-to-left shunts. In cases of unexplained hypoxia, consider sleep studies to rule out sleep apnea or bronchoscopy to evaluate for airway obstruction. The workup should be tailored to the clinical presentation, with more invasive testing reserved for cases where initial investigations are inconclusive, and the oxygen saturation should be monitored continuously until the patient is stable or arrives at hospital for a full assessment, adjusting the oxygen concentration upwards or downwards to maintain the target saturation range of 94–98% unless stated otherwise 1.

From the Research

Hypoxia Workup

• Hypoxia is a condition where the body or a region of the body is deprived of adequate oxygen supply, and its workup involves various diagnostic and therapeutic approaches 2.
• The management of hypoxia typically starts with assessing the severity of hypoxemia, determining the underlying cause, and implementing appropriate treatment, which may include oxygen therapy, non-invasive ventilation, or mechanical ventilation 2.

Oxygen Therapy

• Conventional oxygen therapy (COT) and noninvasive ventilation (NIV) have been traditionally used to treat acute or chronic respiratory failure, but high-flow nasal cannula (HFNC) oxygen therapy has emerged as a promising alternative 3.
• HFNC provides oxygen at high flows with optimal heat and humidification, reducing anatomical dead space, improving carbon dioxide wash-out, and generating a positive end-expiratory pressure, making it well-tolerated and easy to use in various clinical settings 3.
• Studies have shown that HFNC can effectively reduce dyspnea and improve oxygenation in patients with respiratory failure from various etiologies, potentially avoiding the need for more invasive supports 3, 4.

Comparison of HFNC and NIV

• A physiological comparison of HFNC and helmet NIV in patients with acute hypoxemic respiratory failure found that helmet NIV improved oxygenation, reduced dyspnea, and decreased inspiratory effort, with similar transpulmonary pressure swings and comfort levels 4.
• However, another study suggested that HFNC may be comparable to NIV in preventing reintubation after extubation in COPD patients, with improved tolerance, comfort, and fewer complications 5.

Clinical Considerations

• The choice of oxygen therapy, including HFNC, NIV, or conventional oxygen therapy, depends on the individual patient's characteristics, the underlying cause of hypoxia, and the clinical setting 6, 5.
• Clinicians should consider the available options and individualize their approach based on patient characteristics, and future research should focus on addressing the gaps in knowledge to guide clinical decision-making and optimize outcomes for patients with hypoxia 5.