Understanding Respiratory Physiology: Key Concepts and Adaptations in Breathing

1. Chapters 10 & 11 Respiration, Responses and Adaptations

2. Respiration • Pulmonary Ventilation • Breathing; the process by which air is moved into and out of the lungs • Bring in Oxygen (room air=79% N, 21% O2, .03% CO2) • Remove CO2

3. Respiration • The volume of air moved in one minute’s time is called MINUTE ventilation (Ve) • Tidal volume (TV) X Respiratory Rate (RR) • Rest = 500 ml X 12 breaths/min = 6L/min

4. Static Lung Volumes • Tidal Volume: the volume of air breathed during ventilation (~ 500 ml) • Residual Volume: Amount of air remaining in the lungs after a forced exhalation (~ 1200 ml)

5. Static Lung Volumes • IRV: Amount of air that can be forcefully inhaled after a normal tidal inhalation • Males – 3100 ml, females – 1900 ml • ERV: Amount of air that can be forcefully exhaled after a normal tidal exhalation • Males – 1200 ml, females – 700 ml

6. Static Lung Volumes • Total lung capacity: The maximum amount of air contained in the lungs after a maximum inspiration (TV + IRV + ERV + RV) • 6000 ml for males, 4200 ml for females • Vital Capacity: Total amount of exchangeable air (amount that can be expired after a maximum inspiration) (TV + IRV + ERV) • 4800 ml males, 3000 ml females

7. Dynamic Lung Volumes • Volumes measure in a specific time period • FEV1 – forced expiratory volume • +/> 80% of FVC is normal • < 65-70% suggests lung damage/disease • MVV – maximal voluntary ventilation • Estimate of max. ventilation potential in 1 min.

8. a-vO2 difference • Difference in the amount of oxygen in arterial and venous blood • Reflects oxygen use by the tissues • aO2 = ~ 20 ml O2/dL blood • vO2 @ rest = ~ 15 ml O2/dL • Resting a-vO2 diff = ~ 5 ml O2/dL

9. Respiratory Response Short or long-term, light, moderate and heavy submaximal exercise • Ventilation increases (hyperpnea) • Need for O2 increases; need to rid body of CO2 • Low exercise intensities – Ve increases mostly due to an increase in TV (deeper breathing) • High exercise intensities – RR also starts to increase, increasing Ve further

10. Respiratory Response Short or long-term, light, moderate and heavy submaximal exercise • After 2-3 minutes, Ve reaches a steady state

11. Respiratory Response Incremental aerobic exercise to maximum • Ve increases with increasing exercise intensity, although the increase is not entirely linear • Ve can increase to 100 L/min in smaller individuals and 200 L/min in larger individuals

12. Respiratory Response Incremental aerobic exercise to maximum • Ve increases linearly up to ~ 50-75% max, at which point a break occurs which results in a second steeper rise

13. Ventilatory Threshold – the point(s) where minute ventilation breaks from linearity during incremental exercise to maximum • The % of max at which the Ventilatory Thresholds occur is related to endurance performance

14. Respiratory Limitations? Maximal Voluntary Ventilation (MVV) • Ve is usually not pushed to the MVV, even during maximal exercise • Therefore, Ve usually does not limit exercise capacity

15. Respiratory Limitations • Asthma • Chronic Obstructive Pulmonary Disease (COPD) • These conditions cause resistance to air flow (ventilation) and can result in dyspnea (shortness of breath) • In these individuals, the respiratory system can limit performance

16. Respiratory Responses Static Exercise • Responses are similar to short term, light to moderate aerobic exercise • Valsalva Maneuver – breath holding that involves closing of the glottis and contraction of the diaphragm and abdominal musculature • Increase intra-abdominal pressure and BP increases • Proper breathing helps to regulate BP

17. Respiratory Adaptations • Most lung volumes and capacities remain essentially unchanged after training • Swimmers demonstrate some increases

18. Ve adaptations • Resting Ve does not change • Submaximal Ve may decrease a bit • Maximal Ve increases after training • Primarily due to increased maximal RR, but maximal tidal volume increases too

19. Why so few changes in lung function?