Does the presence or absence of hypoxemia (low oxygen levels in the blood) significantly impact the differential diagnosis of acute dyspnea (shortness of breath)?

From the Guidelines

No, it is not true that the presence or absence of hypoxemia has a minimal impact on the differential diagnosis of acute dyspnea. Hypoxemia is a critical finding that significantly narrows the differential diagnosis in patients with acute shortness of breath. The presence of hypoxemia strongly suggests conditions that affect gas exchange in the lungs, such as pneumonia, pulmonary embolism, pulmonary edema, or acute respiratory distress syndrome. Conversely, normal oxygen saturation in a dyspneic patient may point toward conditions like anxiety, anemia, metabolic acidosis, or early heart failure. The degree of hypoxemia can also provide clues about the severity of the underlying condition. For example, severe hypoxemia despite supplemental oxygen might indicate shunt physiology as seen in severe pneumonia or ARDS. When evaluating a patient with acute dyspnea, oxygen saturation should be measured immediately, and arterial blood gas analysis should be considered to assess the degree of hypoxemia and determine if hypercapnia is present. This information, combined with clinical history, physical examination findings, and other diagnostic tests, helps clinicians rapidly identify the cause of dyspnea and initiate appropriate treatment, as supported by recent studies such as the one published in 2021 by the American College of Physicians 1.

Some key points to consider when evaluating a patient with acute dyspnea include:

• Measuring oxygen saturation immediately and considering arterial blood gas analysis to assess the degree of hypoxemia and determine if hypercapnia is present
• Using point-of-care ultrasonography to improve the correctness of diagnosis in patients with acute dyspnea, as shown in a study published in 2021 1
• Considering the use of BNP or NT-proBNP measurements to improve diagnostic accuracy in the diagnosis of acute heart failure syndrome, as recommended in a study published in 2007 1
• Assessing patients with hypoxemia for underlying conditions that may be causing the hypoxemia, such as chronic lung disease or cardiac disease, and considering the use of oxygen therapy to relieve symptomatic breathlessness, as discussed in a guideline published in 2017 1.

Overall, the presence or absence of hypoxemia has a significant impact on the differential diagnosis of acute dyspnea, and clinicians should consider this information when evaluating patients with this symptom.

From the Research

Presence or Absence of Hypoxemia in Acute Dyspnea Diagnosis

• The presence or absence of hypoxemia has a significant impact on the treatment of acute dyspnea, as evidenced by studies on high-flow nasal cannula (HFNC) oxygen therapy 2, 3.
• HFNC has been shown to improve dyspnea and comfort in patients with acute dyspnea and hypoxemia, and may be considered as a first-line therapy even before making a clear diagnosis for dyspnea 3.
• However, the effect of HFNC on oxygenation and patients' prognosis is still unclear, and more studies are needed to explore this topic 3.

Differential Diagnosis of Acute Dyspnea

• Acute dyspnea is a complex symptom that can be caused by various diseases, including congestive heart failure, asthma exacerbation, COPD exacerbation, and pneumonia 2, 4.
• The differential diagnosis of acute dyspnea requires a comprehensive approach, taking into account the patient's medical history, physical examination, and laboratory results 4.
• The presence or absence of hypoxemia may not have a significant impact on the differential diagnosis of acute dyspnea, as the underlying cause of the symptom is often multifactorial 5, 6.

Treatment of Acute Dyspnea and Hypoxemia

• HFNC oxygen therapy has been shown to be effective in treating acute dyspnea and hypoxemia, and may reduce the risk of requiring more advanced ventilation support 2, 3.
• The optimal management of patients with acute dyspnea and pulmonary diseases requires a defined pathway, including organization, structure, personnel, and content 4.
• Apnoeic oxygenation via HFNC combined with non-invasive ventilation preoxygenation may be an effective strategy for reducing oxygen desaturation during intubation in hypoxaemic patients 6.