TABLE 27.1.

Causes of Dyspnea

	Site of Pathology	Pathophysiology
Pulmonary Causes
Airflow limitation	Airways	Limitation to ventilation through flow-through airways
Restriction (intrinsic)	Lung parenchyma	Poor lung compliance
Restriction (extrinsic)	Chest wall	Poor chest wall compliance with or without poor chest wall strength
Acute pulmonary disease	Lungs	Increased ventilation/perfusion (V/Q) mismatch
Cardiac Causes
Valvular disease	Heart valve stenosis or incompetence	Limited cardiac output
Coronary disease	Heart muscle ischemia	Coronary insufficiency leads to myocardial ischemia
Heart failure	Ventricular failure	Limited cardiac output from decreased stroke volume
Circulatory
Anemia	Low hemoglobin can be from blood loss or from hemoglobinopathies	Limited oxygen-carrying capacity
Peripheral circulation	Peripheral arterial disease	Inadequate oxygen supply to metabolically active tissues, leading to early anaerobic threshold
Whole Body
Obesity	Excess adipose tissue with associated physiologic changes	Increased work of movement, decreased efficiency May have respiratory restriction if severe—both extrinsic chest wall restriction and upper airway obstruction
Psychogenic	Emotional	Hyperventilation, anxiety
Deconditioning	Multiple organ systems, muscle weakness, cardiac deconditioning	Loss of ability to effectively distribute systemic blood flow, inefficient aerobic metabolism
Malingering	Emotional	Inconsistent results