Cardinal Manifestations of Disease: DYSPNEA

Dr. Meg-angela Christi Amores

Dyspnea

• a "subjective experience of breathing discomfort that consists of qualitatively

distinct sensations that vary in intensity. The experience derives from interactions among multiple physiological, psychological, social, and environmental factors, and may induce

secondary physiological and behavioral responses."

-American Thoracic Society

Mechanisms of Dyspnea

• Motor efferents– Disorders of the ventilatory pump, muscles are

weak or fatigued, greater effort is required• Sensory afferents– Chemoreceptors in the carotid bodies and medulla

are activated by hypoxemia, acute hypercapnia, and acidemia – air hunger

– Mechanoreceptors in the lungs, when stimulated by bronchospasm, lead to a sensation of chest tightness

Mechanisms of Dyspnea

• Integration: Efferent – Reafferent Mismatch– discrepancy or mismatch between the feed-forward

message to the ventilatory muscles and the feedback from receptors that monitor the response of the ventilatory pump increases the intensity of dyspnea

– Asthma and COPD• Anxiety– altering the interpretation of sensory data or by

leading to patterns of breathing that heighten physiologic abnormalities in the respiratory system

Differential Diagnoses

• Dyspnea is the consequence of deviations from normal function in the cardiopulmonary systems

• Respi: 3 categories:• Controller• Ventilatory pump• Gas exhanger

• Cardiovas: 3 categories• Low• Nomal• High Cardiac output

Respiratory System Dyspnea

• Controller:• Stimulation of pulmonary receptors, as occurs in acute bronchospasm,

interstitial edema, and pulmonary embolism = air hunger• High altitude, high progesterone states such as pregnancy, and drugs

such as aspirin

• Ventilatory pump• Disorders of the airways – inc resistance• stiffen the chest wall, such as kyphoscoliosis

• Gas Exchanger• Pneumonia, pulmonary edema, and aspiration all interfere with gas

exchange• Pulmonary vascular and interstitial lung disease

Cardiovascular System Dyspnea

• High Cardiac Output• Mild to moderate anemia is associated with breathing

discomfort during exercise• Left to right cardiac shunts

• Normal• Cardiovascular deconditioning • Diastolic dysfunction (hypertension, aortic stenosis, or

hypertrophic cardiomyopathy)

• Low• Diseases of the myocardium resulting from coronary artery

disease

Approach to patient

• Let patient describe in his/her words• Ask for orthopnea, nocturnal dyspnea• Onset, persistence• Risk factors for certain diseases• Platypnea – dyspnea in the upright position,

relieved in the supine

Respiratory vs. CV system

• a cardiopulmonary exercise test should be carried out to determine which system is responsible for the exercise limitation

• At peak exercise, max ventilation reached, O2 sat below 90%, develops bronchospasm = Respiratory

• If HR >85% of predicted max, anaerobic threshold occurs early, BP high or drops, ischemic changes in ECG = Cardiovascular

Treatment

• Correct underlying problem• Supplemental Oxygen if sO2 is <90%• In COPD: pulmo rehab

• For the next meeting, read on Cardinal Manifestations of Disease : EDEMA

• Harrison’s Principles of Internal Medicine 17th edition