What is the most common cause of dyspnea?

The most common cause of dyspnea is typically linked to hypercapnia, which refers to an elevated level of carbon dioxide (CO2) in the bloodstream. When there is an accumulation of CO2, it can lead to respiratory acidosis, stimulating the respiratory centers in the brain. This can result in a sensation of breathlessness as the body attempts to increase ventilation to expel the excess CO2 and restore normal gas exchange.

Dyspnea can manifest from a range of physiological issues, but hypercapnia is often a direct result of impaired ventilation, which can stem from several conditions such as chronic obstructive pulmonary disease (COPD) or respiratory failure. In contrast, while other factors like hypoxemia (low oxygen levels), respiratory muscle weakness, and pulmonary hypertension can contribute to feelings of breathlessness, hypercapnia is considered a more immediate and widespread trigger in many respiratory conditions, making it a primary focus in the assessment of dyspnea.