respirator Pulmonary System Essentials of Exercise Physiology
Dec 15, 2015
respiratory
Pulmonary System
Essentials of Exercise Physiology
respiratory
Respiration External respiration: ventilation and exchange of
gasses in the lungs (pulmonary function). Internal respiration: ventilation and exchange of
gasses in the tissues (pulmonary function).
respiratory
Functions of Respiratory SystemPrimary purpose of
respiratory system is:Provide means of oxygen
exchange between external environment and body
Provide a means of carbon dioxide exchange between the body and the external environment
Exchange occurs as result:Ventilation: mechanicalDiffusion: random movement
respiratory
Functions of Respiratory System
Respiratory system also helps regulate acid-base balance in body, especially during exercise.
Cl- + H+ + NaHCO3
NaCl + H2CO3
CO2 + H2O
respiratory
Acid - Base Balance
Acids - molecules which can liberate hydrogen ions
Bases - molecules which can accept hydrogen ions
Buffer - resists changes in pH by either accepting hydrogen ions or liberating them depending upon local conditions
respiratory
Structure Pulmonary System
Right and left lungs enclosed by membranes called pleura
Visceral pleura adheres to outer surface of lungs
Parietal pleura adheres to thoracic wall and diaphragm
respiratory
respiratory
Intrapleural Space
Contains fluid which lubricates pleura
Creates a low pressure area– pressure is below
atmospheric during inspiration, allowing the lungs to inflate
respiratory
Functional Zones of Air Passages
Conducting zone– passageways leading to respiratory zone– area where no gas exchange occurs– nasal cavity, pharynx, larynx, trachea, bronchioles
Respiratory zone– where gas exchange actually occurs– alveoli
respiratory
Roles of Conducting Zone
Warms air Mucus traps small particles Cilia sweep particles upwards Macrophages engulf foreign particles
respiratory
Roles of Respiratory Zone
Provides large surface area for gas exchange– 600 million alveoli– Total surface area is 60 – 80 square meters or
about size of half a tennis court Provides a very thin barrier for gas exchange
– 2 cell layers thick
respiratory
Alveoli
Type II alveolar cells secrete pulmonary surfactant– form a monomolecular layer over alveolar
surfaces– surfactant stabilizes alveolar volume by
reducing surface tension created by moisture
respiratory
Mechanics of Ventilation
Change in thoracic cavity volume produces corresponding change in lung volume
Increase in lung volume results in decrease in lung pressure (Boyle’s law)
Differences in pressure pulls air into the lungs– pressure within the lungs becomes less than the
atmospheric pressure– bulk flow (from high pressure to low pressure)
respiratory
Muscles of Inspiration
Diaphragm– contracts, flattens, & moves downward up to 10 cm– enlarges & elongates chest cavity, expands volume– during quiet breathing diaphragm works alone
External intercostals, pectoralis minor, sternocleidomastoid & scaleni– lift ribs up and outwards– during exercise, accessory muscles called into play
respiratory
Muscles of Inspiration
respiratory
Muscles of Expiration
Expiration during quiet breathing is passive due to elastic recoil of chest cavity
Decrease in lung volume forces air out of lungs
During exercise and voluntary hyperventilation, – rectus abdominus, transverse abdominus: push
diaphragm up– internal intercostals: pull ribs downwards
respiratory
Total Lung Capacity Tidal volume (VT)
– amount either inspired or expired during normal ventilation
Inspiratory reserve volume– maximal volume inspired after a normal inspiration
Expiratory reserve volume– volume expired after a normal expiration
During exercise VT increases largely from IRV. Residual volume
– volume remaining in lungs after maximal expiration
respiratory
Lung Capacities Total lung capacity
– volume within lung after a maximal inspiration Inspiratory capacity
– maximal volume inspired from the end of tidal expiration
Functional residual capacity– volume in lungs after normal expiration
Vital capacity– maximal volume expired after maximal inspiration
respiratory
Dynamic Lung Volumes
Depend 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).
respiratory
respiratory
Minute Ventilation Volume of gas ventilated in one minute
– equal to tidal volume times frequency– Rest in 70 kg man, 6.0 L/min = 0.5 L x 12– Maximal exercise, 120-175 L/m = 3-3.5 x 40-50– increases as oxygen consumption increases– closely associated with CO2 production
ERROR
respiratory
Anatomical vs Physiological Dead Space
Anatomical dead space– areas of conducting zone not designed for
diffusion of gases– VT = VA + VD
– At rest, VT = 500 ml = 350 ml + 150 ml
Physiological dead space – areas of lung and pulmonary capillary bed which
are unable to perform gas exchange as designed
respiratory
Anatomic Dead Space
respiratory
Physiologic Dead Space Optimal diffusion requires matching of ventilation to
perfusion: 1 ventilated alveoli/ 1 blood perfused alveoli Ventilation (V) / perfusion (Q) is not equal across the
lung Top of lung is poorly perfused
– V / Q = 3.3 at top of lung Bottom of lung has more perfusion than ventilation
– V / Q = .63 at bottom of lung V / Q values above .5 are generally adequate
respiratory
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.
respiratory
Disruptions in Normal Breathing
Dyspnea shortness of breath or subjective distress in breathing.
Hyperventilation ≠ Hyperpnea
Valsalva maneuver: forced exhalation against closed glottis. What happens to blood pressure?
respiratory
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) area thickness