Presentation on theme: "Essentials of Exercise Physiology"— Presentation transcript:
1 Essentials of Exercise Physiology Pulmonary SystemEssentials of Exercise Physiology
2 RespirationExternal respiration: ventilation and exchange of gasses in the lungs (pulmonary function).Internal respiration: ventilation and exchange of gasses in the tissues (pulmonary function).
3 Functions of Respiratory System Primary purpose of respiratory system is:Provide means of oxygen exchange between external environment and bodyProvide a means of carbon dioxide exchange between the body and the external environmentExchange occurs as result:Ventilation: mechanicalDiffusion: random movement
4 Functions of Respiratory System Respiratory system also helps regulate acid-base balance in body, especially during exercise.Cl- + H+ + NaHCO3 NaCl + H2CO3 CO2 + H2O
5 Acid - Base Balance Acids - molecules which can liberate hydrogen ions Bases - molecules which can accept hydrogen ionsBuffer - resists changes in pH by either accepting hydrogen ions or liberating them depending upon local conditions
6 Structure Pulmonary System Right and left lungs enclosed by membranes called pleuraVisceral pleura adheres to outer surface of lungsParietal pleura adheres to thoracic wall and diaphragm
10 Functional Zones of Air Passages Conducting zonepassageways leading to respiratory zonearea where no gas exchange occursnasal cavity, pharynx, larynx, trachea, bronchiolesRespiratory zonewhere gas exchange actually occursalveoli
11 Roles of Conducting Zone Warms airMucus traps small particlesCilia sweep particles upwardsMacrophages engulf foreign particles
12 Roles of Respiratory Zone Provides large surface area for gas exchange600 million alveoliTotal surface area is 60 – 80 square meters or about size of half a tennis courtProvides a very thin barrier for gas exchange2 cell layers thick
13 Alveoli Type II alveolar cells secrete pulmonary surfactant form a monomolecular layer over alveolar surfacessurfactant stabilizes alveolar volume by reducing surface tension created by moisture
15 Mechanics of Ventilation Change in thoracic cavity volume produces corresponding change in lung volumeIncrease in lung volume results in decrease in lung pressure (Boyle’s law)Differences in pressure pulls air into the lungspressure within the lungs becomes less than the atmospheric pressurebulk flow (from high pressure to low pressure)
16 Muscles of Inspiration Diaphragmcontracts, flattens, & moves downward up to 10 cmenlarges & elongates chest cavity, expands volumeduring quiet breathing diaphragm works aloneExternal intercostals, pectoralis minor, sternocleidomastoid & scalenilift ribs up and outwardsduring exercise, accessory muscles called into play
18 Muscles of ExpirationExpiration during quiet breathing is passive due to elastic recoil of chest cavityDecrease in lung volume forces air out of lungsDuring exercise and voluntary hyperventilation,rectus abdominus, transverse abdominus: push diaphragm upinternal intercostals: pull ribs downwards
19 Total Lung Capacity Tidal volume (VT) Inspiratory reserve volume amount either inspired or expired during normal ventilationInspiratory reserve volumemaximal volume inspired after a normal inspirationExpiratory reserve volumevolume expired after a normal expirationDuring exercise VT increases largely from IRV.Residual volumevolume remaining in lungs after maximal expiration
21 Lung Capacities Total lung capacity Inspiratory capacity volume within lung after a maximal inspirationInspiratory capacitymaximal volume inspired from the end of tidal expirationFunctional residual capacityvolume in lungs after normal expirationVital capacitymaximal volume expired after maximal inspiration
22 Dynamic Lung VolumesDepend on volume and speed of air movement; more useful in diagnosing lung disease.FEV: Forced Expiratory Volume. Volume that can be forcefully expired after maximal inspiration within given time, usually 1 sec.MVV: Maximal Voluntary Ventilation. Volume of air that can be ventilated by maximal effort in one minute. Breathe maximally for 12 (or 15) seconds and total volume recorded, multiplied by five (or 4).
24 Minute Ventilation Volume of gas ventilated in one minute equal to tidal volume times frequencyRest in 70 kg man, 6.0 L/min = 0.5 L x 12Maximal exercise, L/m = x 40-50increases as oxygen consumption increasesclosely associated with CO2 productionIncorrect TV for normal breathing ml is 500 ml.ERROR
25 Anatomical vs Physiological Dead Space Anatomical dead spaceareas of conducting zone not designed for diffusion of gasesVT = VA + VDAt rest, VT = 500 ml = 350 ml mlPhysiological dead spaceareas of lung and pulmonary capillary bed which are unable to perform gas exchange as designed
27 Physiologic Dead Space Optimal diffusion requires matching of ventilation to perfusion: 1 ventilated alveoli/ 1 blood perfused alveoliVentilation (V) / perfusion (Q) is not equal across the lungTop of lung is poorly perfusedV / Q = 3.3 at top of lungBottom of lung has more perfusion than ventilationV / Q = .63 at bottom of lungV / Q values above .5 are generally adequate
28 Minute Ventilation in Exercise Adjustments in breathing rate and depth maintain alveolar ventilation as exercise.Trained athletes maintain alveolar ventilation by increasing VT and minimal increase rate.Deeper breathing causes a greater percentage of incoming “fresh” VT to enter alveoli.Increasing VT in exercise results from encroaching primarily on IRV or ERV?VT plateaus at about 60% vital capacity.
29 Disruptions in Normal Breathing Dyspnea shortness of breath or subjective distress in breathing.Hyperventilation ≠ HyperpneaValsalva maneuver: forced exhalation against closed glottis. What happens to blood pressure?
30 Gas Exchange Fick’s Law Diffusion occurs at a rate which is proportional to differences in partial pressure and the surface area available and is inversely proportional to the thickness of the membrane.Diffusion rate = (P1 - P2) areathickness