Respiratory Exercise Response Chapter 11
Exercise Respiratory system Ventilation rate matches work rate Not a limiting factor Elite athletes
Submaximal (<70% VO 2max )
External Respiration
Internal Respiration Oxygen dissociation curve Rest - 25% oxygen dissociates Reserve for exercise 75%
Oxygen Dissociation Curve
Internal Respiration Exercise increases oxygen extraction Increased PO 2 gradient Increased use in muscles Increased PCO 2 Effects on ph
Internal Respiration Exercise increases oxygen extraction Decreased ph Increased H ions Increased temperature Muscle contraction
O 2 -Hb Dissociation Curve: Effect of ph Blood ph declines during heavy exercise Results in a rightward shift of the curve Favors offloading of O 2 to the tissues Fig 10.15
O 2 -Hb Dissociation Curve: Effect of Temperature Increased blood temperature results in a weaker Hb-O 2 bond Rightward shift of curve Fig 10.16
Oxygen Dissociation Curve
Bohr Effect is: Bohr Effect Rightward shift in oxyhemoglobin dissociation curve that occurs during exercise Bohr Effect caused by: Blood ph decreases during heavy exercise Increased blood temperature from exercising skeletal muscles Purpose Greater unloading of oxygen in tissues
Exercise Long term, moderate to heavy Larger responses Drifting patterns
Submaximal Exercise
Incremental Exercise to Max Pulmonary Ventilation Ventilatory thresholds - breakpoints VT1 50-75% VT2 85-95% May be due to anaerobic metabolism Increased CO2
Incremental Exercise to Max
Incremental Exercise to Max Other mechanisms Catecholamine or potassium stimulation of carotid bodies Limitations in Vt, f, Vd/Vt Increasing body temperature Feedback from skeletal muscle proprioceptors
Incremental Exercise to Max Practical use of ventilatory threshold Relates to endurance exercise performance Moderate duration, high intensity Intervals of 4 to 10 min at heart rate above ventilatory threshold (60 min workout)
Incremental Exercise to Max
Exercise-Induced Hypoxemia EIH Faster blood flow through lungs Extravascular water accumulation edema Increases diffusion distance
Static Exercise Maximal voluntary contraction (MVC) Slight rise in V E May be decrease in a-vo 2 diff Rebound rise in recovery
Static Exericse
Ventilatory Control During Exercise Submaximal exercise Increase due to: Central command Primary drive to increase ventilation Humoral chemoreceptors Feedback to fine tune breathing to match metabolic rate Muscle neural feedback Muscle spindles GTO
Ventilatory Control During Exercise Heavy, incremental exercise Exponential rise above T vent Increasing blood H + Possible secondary factors Blood potassium Rising body temperature Catecholamines Neural feedback
Ventilatory Control During Exercise Fig 10.26
Ventilatory changes with Pre exercise Anticipatory rise Central command in higher brain centers (cerebral cortex) Early exercise Rapid rise Central command exercise
Ventilatory changes with Rapid rise replaced by slower rise With maximal exercise Plateaus in submax Slow rise due to Central command Chemo receptors that respond dt to chemical stimuli (CO 2, H + ) exercise
Ventilatory changes with Initial Recovery Sudden decrease in V E Decrease in central command Slower decrease to resting values Proportional to chemoreceptor stimuli CO 2, H + exercise
Effect of Training on Ventilation Ventilation is lower at same work rate following training May be due to lower blood lactic acid levels Better ability of muscles to use fatty acids Results in less feedback to stimulate breathing
Effects of Endurance Training on Ventilation During Exercise Fig 10.27
Ventilatory Equivalent Amount of air ventilated for oxygen consumed VE = liters of air breathed for every liter of oxygen consumed Greater efficiency with training means less air breathed per unit of oxygen consumed VE = V E L/min VO 2 L/min
Ventilatory Efficiency V E = 6 l/min VO 2 = 250 ml/min VE = 6.25 VE = 24 L air/l O 2
Ventilatory Efficiency Submax workload the same Untrained Trained V 100 L/min 90 L/min V E VO 2 2.5 L/min 2.5 L/min 100/2.5 90/2.5 VE 40 L air/l O 2 36 L air/lo 2
Oxygen Cost of Ventilation Respiratory muscles require portion of oxygen consumption Rest 1-2% VO 2 (minimal) Resting VO 2 = 300 ml/min 2 3 to 6 ml/min used for respiratory muscles Heavy exercise 8-10% VO 2 Exercise VO 2 = 3-5 L/min 240 to 500 ml/min used for respiratory muscles
Oxygen cost of smoking Smoking increases airway resistance Respiratory muscles must work harder 2 x at rest 4 x at work Respiratory muscles consume more O 2 Less O 2 for skeletal muscles 2
Oxygen cost of smoking Rest 3-6 ml O 2 x 2 = 6 12 ml O 2 Maximal Exercise Respiratory muscles use 8-10% of 3-5 L O 2 Normal oxygen consumption 240 ml 500 ml Smoker: 8-10% x 4 = 960-2000 ml O 2
Terminology Hyperventilation Increased ventilation Disproportionate increase in V E that occurs at the ventilatory breakpoint
Terminology Dyspnea Difficult or labored breathing One is unable to respond to the demand for ventilation Heart failure, emphysema, chronic bronchitis