Dyspnea on Exertion(Archived)

Excerpt

Dyspnea, also known as shortness of breath, is a patient's perceived difficulty in breathing. Sensations and intensity can vary and are subjective. It is a prevalent symptom impacting millions of people. It may be the primary manifestation of respiratory, cardiac, neuromuscular, psychogenic, or systemic illnesses, or a combination of these. Dyspnea on exertion is a similar sensation. However, this shortness of breath is present with exercise and improves with rest. Exercise is defined here as any physical exertion that increases metabolic oxygen demand above the body's ability to compensate. Oxygen is vital to the human body as it is used for oxidative phosphorylation, and it is the last acceptor of an electron in the electron transport chain. The sensation of dyspnea mostly comes when our body is lacking oxygen delivery.

Oxygen Delivery: Hb x 1.39 x SaO₂ x Cardiac Output + 0.003 x PaO₂

1. Hb is the concentration of hemoglobin in grams per liter

2. 1.39- oxygen binding capacity of hemoglobin per gram

3. SaO₂ is hemoglobin oxygen saturation expressed as a fraction (eg, 98% will be 0.98)

4. Cardiac output is described as the amount of blood pumped by the heart in liters per minute

5. 0.003 x paO₂ is the amount of dissolved oxygen in the blood in milliliters

If a body has low Hb, hemoglobinopathies, some toxicities affecting Hb (like carbon monoxide toxicity), low cardiac output (congestive heart failure [CHF], myocardial infarction [MI], arrhythmia), a person will feel dyspneic.