Respiratory Changes in Exercise

Introduction

• Bite Size Med: Discussing quick concepts in basic medical sciences.
• Focus: Respiratory changes during exercise.
• Concepts Covered: Physiology, oxygen demand, carbon dioxide production, ventilation.

Physiological Changes During Exercise

Oxygen and Carbon Dioxide Balance

• Increased Oxygen Demand: Exercising muscles require more oxygen.
• Carbon Dioxide Production: Increased due to enhanced tissue metabolism.
• Alveolar Ventilation: Must increase to accommodate oxygen intake and CO2 expulsion.
  • Result: Despite increased ventilation, arterial O2 and CO2 remain normal — possibly due to efficient gas exchange.
  • Venous Changes: Increased CO2 and reduced O2 in venous blood.

Ventilation Stimuli

• Muscle and Joint Proprioceptors: Stimulate the dorsal respiratory group in the medulla, enhancing inspiration.

pH and Exercise

• Moderate Exercise: pH remains stable.
• Strenuous Exercise:
  • Lactic Acid Production: From anaerobic metabolism increases H+ concentration.
  • Result: Lower pH.

Cardiovascular Changes

• Increased Cardiac Output: To meet oxygen demands.
• Pulmonary Blood Flow: Increases, affecting ventilation-perfusion (V/Q) ratio.
  • V/Q Ratio: More uniform due to balanced increase in ventilation and perfusion.
  • Normal V/Q Discrepancy: Higher at the apex, lower at the base of the lungs under resting conditions.

Oxygen Dissociation Curve

• Shift to the Right: Occurs during intense exercise.
  • Reasons: Increased CO2, lactic acid, elevated muscle temperature.
  • Effect: More oxygen released to meet high demand.
  • P50 Increase: More O2 needed for 50% hemoglobin saturation.

Conclusion

• Understanding these physiological changes helps manage the body's oxygen and carbon dioxide levels during exercise.