From the Research
Croup leads to pulsus paradoxus due to increased negative intrathoracic pressure during inspiration, as evidenced by a study published in the American Journal of Respiratory and Critical Care Medicine in 1998 1.
Pathophysiology of Croup and Pulsus Paradoxus
In croup, the viral infection causes inflammation and narrowing of the upper airway, particularly the subglottic region. This narrowing creates increased airway resistance, forcing the child to generate stronger negative intrathoracic pressure during inspiration to overcome the obstruction.
- The exaggerated negative pressure increases venous return to the right heart while simultaneously impeding left ventricular filling by increasing afterload.
- The result is a more pronounced than normal decrease in systolic blood pressure during inspiration, which manifests as pulsus paradoxus (a drop in systolic blood pressure >10 mmHg during inspiration).
Clinical Significance of Pulsus Paradoxus in Croup
This physiological response is similar to what occurs in severe asthma or pericardial tamponade, though the mechanism differs slightly.
- The severity of pulsus paradoxus often correlates with the degree of airway obstruction, making it a useful clinical sign when assessing the severity of croup, particularly in cases where the child is in significant respiratory distress.
- A study published in 2011 2 highlights the importance of recognizing croup symptoms and the potential for pulsus paradoxus as a clinical indicator of severity.
Management of Croup
While the question focuses on the pathophysiology of croup leading to pulsus paradoxus, management strategies are crucial for improving outcomes.
- Nebulized epinephrine and dexamethasone are commonly used treatments, with evidence supporting their efficacy in reducing symptoms and improving outcomes, as seen in studies from 1988 3 and 2018 4.
- The choice of treatment may depend on the severity of symptoms and the presence of pulsus paradoxus, among other factors.