“I can’t breathe”: The Challenge of Dyspnea

1. “I can’t breathe”: The Challenge of Dyspnea Physiology and Pathophysiology PawandeepBrar MD Palliative Care Physician TemmyLatner Centre for Palliative Care Mount Sinai Hospital

2. Objectives • Review causes of dyspnea • To review normal respiratory cycle • Review pathophysiology of dyspnea

3. Causes of Dyspnea

4. Physiology of Respiration • Respiratory Centre in the medulla and pons coordinates activity of: • Diaphragm, • Intercostal Muscle • Accessory Muscles of Respiration

5. Physiology of Respiration • Respiratory Centre receives sensory information from • Central and Peripheral Chemoreceptors • Peripheral Mechanoreceptors from muscles • Pulmonary Vagal Afferents

6. Physiology of Respiration • Respiratory system designed to maintain homeostasis with respect to gas exchange (adequate oxygenation) & the acid-base status of the organism (adjust PaCO2 to maintain normal pH) • Derangements in oxygenation as well as acidemia lead to breathing discomfort

7. Pathophysiology of Dyspnea • Pathophysiology of dyspnea is complex & multiple • Can break it down into 3 components • Work of Breathing: increase effort of breathing against increased resistance of breathing with weakened muscles (sensed through mechanoreceptors) • Chemoreceptors: sense hypercapnea and hypercarbia • Neuromechanical Dissociation: when there is a mismatch between what the brain desires for respiration and the sensory feedback it receives

8. Take Home Points • Respiratory system is a complex feedback loop designed to maintain homeostasis • Hypoxia is not the only factor in dyspnea • There is still much to be learned about the pathophysiology of dyspnea!

9. Thank you!