TABLE 27.2.

Effects of Physiologic Conditions on Cardiopulmonary Exercise Capacity

Abnormality	Physiologic Abnormality	Gas Exchange
Obesity	•Increased work with activity •Inefficient exercise	•Rapid alveolar-arterial p(a-a)o 2 fall with exercise •Low aerobic capacity (Vo 2max) •Rapid fatigue
Peripheral vascular disease	•Claudication can limit exercise	•Low Vo 2max •Increased lactic acidosis •Associated deconditioning often present •Low anaerobic threshold
Pulmonary vascular disease	•Impaired pulmonary blood flow •Right ventricular failure or overload •Possible right to left shunt	•Low Vo 2max •Low anaerobic threshold •Rapid pulse at low exercise •Hypoxemia •Excessive dyspnea
Anemia	•Low oxygen-carrying capacity	•Low Vo 2max •Early anaerobic threshold •Rapid pulse at low exercise •Fatigue and dyspnea
Chronic obstructive pulmonary disease	•Impairment to expiratory phase of breathing •Decreased alveolar ventilation	•Low Vo 2max •Low anaerobic threshold •Rapid pulse at low exercise •Submaximum heart rate achieved •Retention of CO2 that increases with exercise
Restrictive lung disease (intrinsic)	•Poor diffusion capacity •Poor pulmonary compliance •Pulmonary hypertension in later disease	•Low Vo 2max •Early anaerobic threshold •Tachypnea at all levels of exertion •Low pulmonary reserve •High alveolar-arterial p(a-a)o 2 difference yielding marked hypoxemia •Marked dyspnea •Presence of pulmonary hypertension can cause severe hypoxemia and loss of hemodynamic response to exercise •Can trigger cough with exercise
Restrictive lung disease (extrinsic)	•Poor chest wall compliance •Chest wall muscle weakness •Loss of neural control of breathing musculature	•Low Vo 2max •Early anaerobic threshold •Tachypnea with low tidal volumes •Low pulmonary reserve •Submaximum heart rate achieved •Oxygenation and CO2 usually preserved until severe end-stage disease
Asthma	•Restricted expiratory phase of breathing from airway obstruction •Decreased alveolar ventilation •In exercise-induced asthma, peak flows drop 5–10 minutes into exercise	•Most findings are normal when not symptomatic and resemble obstructive disease with acute attack
Ventricular failure	•Compromised pulmonary blood flow •In left ventricular failure, can have pulmonary vascular congestion	•Low Vo 2max •Early anaerobic threshold •Tachypnea, dyspnea •Exaggerated heart rate response to exercise •May have hypoxemia with pulmonary congestion and loss of normal hemodynamic response to exercise
Ischemic heart disease	•Chest pain/cardiac ischemia •Can precipitate ventricular failure	•Often normal at rest or until ischemia •With onset of ischemia and ventricular stiffening/systolic dysfunction, can appear like mild ventricular failure •Can have loss of normal hemodynamic response to exercise with onset of ischemia
Metabolic acidosis	•Metabolic acidosis, low HCO3 −	•Normal diffusion •Exaggerated response of ventilation to exercise •Low Vo 2max