Overview
- ↑ O2 demand → ↑ respiratory rate and ↑ tidal volume → ↑ minute ventilation
- ↑ O2 consumption and ↑ CO2 production
- Arterial blood
- no change in PaO2 and PaCO2
- ↑ minute ventilation and ↑ efficiency of gas exchange ensure that there is neither a decrease in PaO2 nor an increase in PaCO2
- ↓ pH during strenuous exercise
- secondary to lactic acidosis
- no change in PaO2 and PaCO2
- Venous blood
- ↑ PvCO2
- skeletal muscle adds more CO2 than usual to venous blood
- no change in PaCO2
- sufficient ↑ minute ventilation to remove excess CO2
- ↑ PvCO2
- Pulmonary blood flow
- ↑ cardiac output → ↑ pulmonary blood flow → ↓ pulmonary resistance
- pulmonary blood flow becomes more evenly distributed throughout lungs
- V/Q ratio from lung apex to lung base becomes more uniform
- ↓ physiologic dead space
- ↑ cardiac output → ↑ pulmonary blood flow → ↓ pulmonary resistance
- Oxygen-hemoglobin dissociation curve
- ↑ tissue PCO2, ↓ tissue pH, and ↑ temperature → shifts to right
- ↓ hemoglobin affinity for O2 → ↑ O2 unloading in exercising skeletal muscle
- ↑ tissue PCO2, ↓ tissue pH, and ↑ temperature → shifts to right
- Chronic changes include
- ↑ cardiac chamber size and ↑ wall thickness due to hypertrophy
- ↑ ejection fraction and ↑ cardiac output due to greater efficiency
- ↑ maximum oxygen consumption (VO2 max) during exertion