Ventilation/Perfusion Ratios in the Lung

O 2 Transport in the Blood O 2 is bound to hemoglobin (Hb) for transport in the blood –Oxyhemoglobin: O 2 bound to Hb –Deoxyhemoglobin: O 2 not bound to Hb

Oxyhemoglobin Dissociation Curve

O 2 -Hb Dissociation Curve: Effect of pH Blood pH declines during heavy exercise Results in a “rightward” shift of the curve –Bohr effect –Favors “offloading” of O 2 to the tissues

pH and O2-Hem Diss. Curve

O 2 -Hb Dissociation Curve: Effect of Temperature Increased blood temperature results in a weaker Hb-O 2 bond Rightward shift of curve –Easier “offloading” of O 2 at tissues

Temp. and O2-Hem Diss. Curve

O 2 Transport in Muscle Myoglobin (Mb) shuttles O 2 from the cell membrane to the mitochondria Higher affinity for O 2 than hemoglobin –Even at low PO 2 –Allows Mb to store O 2

Diss. Curve - Myoglobin vs. Hemoglobin

CO 2 Transport in Blood Dissolved in plasma (10%) Bound to Hb (20%) Bicarbonate (70%) –CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 - –Also important for buffering H +

3 Forms of CO2 Transport in Blood

CO2 Exchange in Lung

Ventilation and Acid-Base Balance Blood pH is regulated in part by ventilation An increase in ventilation causes exhalation of additional CO 2 –Reduces blood PCO 2 –Lowers H + concentration

Transition from Rest to Steady State

Exercise in a Hot Environment During prolonged submaximal exercise: –Ventilation tends to drift upward –Little change in PCO 2 –Higher ventilation not due to increased PCO 2

Ventilation vs. Hot/Humid

Respiratory Parameters (Elite vs. Untrained)