Pulmonary Function During Exercise Chapter 10

The Respiratory System Provides gas exchange between the environment and the body Regulates of acid-base balance during exercise

Ventilation Moving Air

Conducting and Respiratory Zones Conducting zone Conducts air to respiratory zone Humidifies, warms, and filters air Components: –Trachea –Bronchial tree –Bronchioles Respiratory zone Exchange of gases between air and blood Components: –Respiratory bronchioles –Alveolar sacs

Pathway of Air to Alveoli

Mechanics of Breathing Ventilation –Movement of air into and out of the lungs via bulk flow Inspiration –Diaphragm pushes downward, lowering intrapulmonary pressure Expiration –Diaphragm relaxes, raising intrapulmonary pressure Resistance to airflow –Largely determined by airway diameter

The Mechanics of Inspiration and Expiration

Pulmonary Volumes and Capacities Measured by spirometry Vital capacity (VC) –Maximum amount of air that can be expired following a maximum inspiration Residual volume (RV) –Air remaining in the lungs after a maximum expiration Total lung capacity (TLC) –Sum of VC and RV

Pulmonary Volumes and Capacities Inspiratory Reserve volume (IRV) –Maximum amount of air that can be inspired following a normal inspiration Expiratory reserve volume (ERV) –Air remaining in the lungs after a normal expiration

A Spirogram Showing Pulmonary Volumes and Capacities

Check measurements to find: Norms for body sizes Indications of healthy lung function Indications of diseases/conditions that affect ventilation –Asthma –Emphysema

Pulmonary Ventilation (VE) The amount of air moved in or out of the lungs per minute –Product of tidal volume (V T ) and breathing frequency (F B ) –(looks similar to Q = SV x HR? ) V E = V T x F B...

Respiration Movement of gasses

Diffusion of Gases Gases diffuse from high  low partial pressure –From lungs to blood and back to lungs –From blood to tissue and back to blood

Partial Pressure of Gases Each gas in a mixture exerts a portion of the total pressure of the gas The partial pressure of oxygen (PO 2 ) –Air is 20.93% oxygen Expressed as a fraction: –If total pressure of air = 760 mmHg, then PO 2 = x 760 = 159 mmHg

Partial Pressure and Gas Exchange

O 2 Transport in the Blood O 2 is bound to hemoglobin (Hb) for transport in the blood –Oxyhemoglobin: O 2 bound to Hb Carrying capacity –201 ml O 2 L -1 blood in males 150 g HbL blood -1 x 1.34 mlO 2 g Hb -1 –174 ml O 2 L -1 blood in females 130 g HbL blood -1 x 1.34 mlO 2 g Hb -1

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

O 2 -Hb Dissociation Curve: Effect of pH Oxygen Content (ml O 2 / 100 ml blood) Amount of O 2 unloaded

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

O 2 -Hb Dissociation Curve: Effect of Temperature Amount offloaded Oxygen Content (ml O 2 / 100 ml blood)

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

Dissociation Curves for Myoglobin and Hemoglobin

Carbon Dioxide Transport Not identical to oxygen transport

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 - Muscle Normal Metabolism binds to Hb Carbonic Acid Bicarbonate

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 - Lung Ventilation O 2 replaces on Hb

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 + Muscle Lung Intense Exercise Ventilation

Release of CO 2 From Blood

Effect of Respiratory Gases on Ventilation How do these gasses affect breathing?

Control of Ventilation Respiratory control center in the brainstem –Regulates respiratory rate –Receives neural and humoral input Feedback from muscles PO 2, PCO 2, H +, and K + in blood PCO 2 and H + concentration in cerebrospinal fluid

Effect of Arterial PO 2 on Ventilation

Effect of Arterial PCO 2 on Ventilation

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 H + + HCO 3 -  H 2 CO 3  H 2 O + CO 2 Exhalation

Ventilatory Control During Submaximal Exercise

Incremental Exercise Linear increase in ventilation –Up to ~50-75% VO 2max Exponential increase beyond this point Ventilatory threshold (T vent ) –Inflection point where V E increases exponentially..

Ventilatory Response to Exercise: Tvent

Is This Trainable? Does an endurance trained person breathe less? Does an endurance trained person need less oxygen?

Effect of Training on Ventilation Ventilation is lower at same work rate following training –May be due to lower blood lactic acid levels –Results in less feedback to stimulate breathing –Well trained produce less CO 2 – stim. for breathing

Effects of Endurance Training on Ventilation During Exercise

Ventilatory Response to Exercise: Trained vs. Untrained In the trained runner –Decrease in arterial PO 2 near exhaustion more oxygen extracted –pH maintained at a higher work rate less lactic acid produced – “aerobic metab.” –T vent occurs at a higher work rate lower relative intensity

Ventilatory Response to Exercise: Trained vs. Untrained

Do the Lungs Limit Exercise Performance? Sub maximal exercise –Pulmonary system not seen as a limitation Maximal exercise –Not thought to be a limitation in healthy individuals at sea level –May be limiting in elite endurance athletes

Questions?

End