The Curious Clinicians 88 - Shunting a Mismatch
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May 1, 2024 Medical student Giancarlo Buonomo joins the podcast to discuss the complexities of systemic pulmonary vasodilators in COPD patients with pulmonary hypertension. The episode explores the impact of sildenafil, inhaled vasodilators, and supplemental oxygen therapy on blood oxygen levels and vascular functions in lung diseases.
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Hypoxic Vasoconstriction's Dual Role
- Hypoxic vasoconstriction initially preserves VQ matching by limiting blood flow to poorly ventilated lung areas.
- Over time, this adaptive response causes vascular remodeling and worsens pulmonary hypertension.
Distinct Mitochondria Mediate Hypoxia
- Pulmonary and systemic vascular smooth muscle mitochondria differ, causing opposite reactions to hypoxia.
- Hydrogen peroxide, produced downstream of oxygen sensing, mediates hypoxic vasoconstriction in lungs.
Sildenafil Lowers Pressure but Lowers Oxygen
- Sildenafil lowers pulmonary artery pressures in COPD-related pulmonary hypertension.
- Despite pressure reductions, blood oxygen levels actually decrease following sildenafil administration.