1. “I can’t breathe”: The Challenge of Dyspnea
Physiology and Pathophysiology
Pawandeep Brar MD
Palliative Care Physician
Temmy Latner 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 CAUSE EXAMPLE Directly related to Cancer
Primary/metastatic lung involvement, pleural effusion, carcinomatosis lymphangitis, SVC syndrome, chest wall invasion, pathological rib fractures
Indirectly Related to Cancer
Pneumonia, cachexia, PE, anemia, metabolic abnormality, ascites
Related to Cancer Therapy
Surgery (lobectomy), radiation pneumonitis, chemotherapy induced fibrosis or cardiomyopathy
Unrelated to Cancer
COPD, CHF, asthma, anxiety, neuromuscular disorder, spiritual pain
: we all know several different causes of dyspnea and this is what we are looking for when we exam a pt….odds are we will find more than one reason for a pt to be dyspneic. But what is the underlying pathophysiology that causes a person to feel sob?

4. Physiology of Respiration
Respiratory Centre in the medulla and pons coordinates activity of:
Diaphragm,
Intercostal Muscle
Accessory Muscles of Respiration
: To understand how these clinical states may trigger dyspnoea, one must first understand how respiratory sensoryinformation is processed by the brain and leads trespiratory
activity. The respiratory centre in the medulla andpons coordinates the activity of the diaphragm, theintercostal muscles, and the 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!