Exam 3 - Exercise Physiology Ch 12, 13, 14

Ch 12 - Pulmonary structure and function Ch 13 - Gas exchange and transport Ch 14 - Pulmonary Ventilation

what is pumonary ventilation?

process of moving and exchanging ambient air with air in lungs

pathway of pulmonary ventilation

• nose and mouth

• trachea (temp adjustment, filter, humidify)

• two bronchi

• bronchioles

• alveoli

what happens in alveolus gas exchange?

• blood enters from right ventricle through pulmonary artery

• blood is oxygenated, CO₂ is removed

• blood exits to pulmonary vein to left ventricle

what is the optimal site of to sample mixed venous blood?

pulmonary artery

how are alveoli arranged?

• appear as a cluster of grapes

• large cross-sectional area for diffusion

what are barriers to the gas diffusion?

• liquid lining in the intra-alveolar membrane

  • surfactant

• alveolar epithelial cells (outer membrane of alveoli)

• basal membrane of alveolar epithelial cell

• interstitial space

• basement membrane of capillary epithelial cell

• capillary endothelium

• plasma in capillary blood

• erythrocyte membrane

• intracellular fluid in erythrocyte

• hemoglobin molecule

what occurs in the lungs?

• site of gas exchange

  • surface that separates blood from surrounding alveolar environment

what is the size of an average-sized adults lungs?

• weigh approx. 1 kg, consists of 10% solid tissue

• 4-6 L in volume

• total surface area = 50-100 m², 20-50x body surface area

how many alveolar sacs does a red blood cell pass?

2-3

at maximal exercise, how much blood flows through the capillary beds of the lung?

less than ½ of a liter, about 1 pint of blood/sec

what are alveoli?

• surface area for gas exchange between lung tissue and blood

• receive largest blood supply of all organs

how large are the alveoli?

• 0.3 mm in diameter or 300 um

in elite athletes, what can high alveolar ventilation and capillary perfusion cause?

• impaired permeability

  • offset by increased pulmonary capillary, protein, and leukotriene increasing inflammatory response

what do the pores of kohn do in alveoli?

evenly disperse surfactant over respiratory membrane reducing surface tensions of liquid

• about 250 mL O₂/min leaves alveoli, about 200 mL CO₂/min diffuses in opposite direction

what can brief intense exercise cause in some athletes?

• increase pulmonary capillary pressure

• generate mechanical stress

  • results in higher conc. of RBCs and protein in broncho-alveolar lavage liquid

what is diffusional equilibrium?

transit time of blood to be oxygenated in pulmonary capillaries

what happens to transit time in the pulmonary capillary during exercise?

• transit time decreases about 0.75 sec to 0.40 sec

decreased capillary transit time is a limiting factor to oxyhemoglobin saturation (S_aO₂) and performance?

False

what happens to transit time in the pulmonary capillary at rest?

• diffusional equilibrium for P_aO₂ and P_aCO₂ is reached in ~0.25 secs

what are the mechanics of ventilation?

• inspiration

• expiration

what occurs in insipiration?

• intra-thoracic pressure < ambient pressure

• lungs inflate

• diaphragm contracts (moves down)

  • also contracts scalene, external intercostal muscles (ribs rise)

what occurs during expiration?

• intra-thoracic pressure > ambient pressure

• lungs deflate

• passive recoil of lung tissue

• relaxation of inspiratory muscles (diaphragm moves up, ribs lower)

what are the different zones of ventilation?

• conducting

• transitional and respiratory

what is the conducting zone of ventilation?

• made up of trachea and terminal bronchioles

• considered anatomical dead space

• small cross-sectional area = high velocity flow

what are the functions of the conducting zones?

• air transport

• humidification

• warming

• partical filtration

• vocalization

• immunoglobulin secretion

what is the transitional and respiratory zones of ventilation?

• made up of bronchioles, alveolar ducts, and alveoli

  • high cross-sectional area = gas movement by diffusion

what are the functions of the transitional and respiratory zones of ventilation?

• gas exchange

• surfactant production

• molecule activation and inactivation

• blood clotting regulation

• endocrine function

what is Fick’s law of diffusion?

governs the diffusion of gas across a fluid membrane

gas diffuses through a sheet of tissue at a rate directly proportional to…

• the tissue cross sectional area

• a diffusion constant directly proportional to solubility of gas

• pressure differential of gas on each side of membrane

  • pressure gradient

gas diffuses through a sheet of tissue at a rate indirectly proportional to…

• tissue thickness

• sqrt of molecular weight of gas

what are the phases of inspiration?

• diaphragm contacts, flattens, and moves downward

• elongation and enlargement of chest cavity expanding lungs

  • intra-pulmonic pressure decreases

• lungs inflate as nose and mouth suck air inward

  • fill lungs to a volume based on magnitude of contraction of inspiratory muscles

• inspiration ends when thoracic cavity expansion ceases cause equality between intra-pulmonic and ambient atmospheric pressure

which muscles contract during inspiration?

• diaphragm

• scalene

• external intercostal muscles

when does inspiratory action increase?

• during exercise

• diaphragm descends, ribs move up, and sternum thrusts outward

why do athletes bend forward from waist after exercise?

• position facilitates breathing

• promotes blood flow back to heart

• minimized antagonist effects of gravity on usual upward direction of inspiratory movements

what are the happens to expiration during rest or light exercise?

• passive process of air movement out of lungs due to

  • natural recoil of stretched lung tissue

  • relaxation of inspiratory muscles

what are the phases of expiration during rest and light exercise?

• sternum and ribs drop, diaphragm rises

• thoracic volume decreases

• alveolar gas compressed, air moves from respiratory tract to atmosphere

• ends when compressive force of expiratory muscles cease

• intra-pulmonic pressure decreases to atmospheric pressure

what happens to the process of expiration during intense exercise?

• internal intercostal and abdominal muscles act powerfully on ribs and abdominal cavity to rapidly reduce thoracic dimensions

• reducing dimensions makes exhalation more rapid and extensive during intense exercise

what are issues to the mechanics of ventilation?

• gender differences

  • no difference in breathing mechanics

• postural differences

what are examples of postural differences affecting ventilation mechanics?

• diaphragmatic breathing in supine position

• more pronounces sternal and costal action in upright position

• intense exercise causes external and internal intercostal actions to dictate rapid changes in thoracic volume rather than diaphragm and abdominal muscles

• optimal posture for ventilation naturally selected by runners and other athletes

what is surfactant?

• surface, active, agent

• consists of lipoprotein mixture of phospholipids, proteins, and calcium ions produced by alveolar epithelial cells (reduce surface tension)

what is surface tension in the lungs?

• resisting force on the surface of a liquid in contact with a gas

• greater the surface tension the greater force needed to inflate alveoli

how does surfactant help the alveoli in the lungs?

• surfactant mixes with fluid surrounding alveoli interrupting the water layer of surface tension

  • reduces energy needed to inflate and deflate alveoli

what predicts static lung volumes?

• age

• gender

• stature

what is tidal volume (TV)?

• air moved during inspiration or expiration phase of breathing cycle

• 0.4-1.0 L of air/breath

what is the inspiratory reserve volume (IRV)?

• inspiring as deeply as possible following normal inspiration

• 2.5-3.5 L above total inspired tidal air

• decreased with age

what is the expiratory reserve volume (ERV)?

• continuing to exhale and forcing as much air as possible from lungs after a normal exhalation

• 1.0-1.5 L

  • decreases with age

what is the forced vital capacity (FVC)?

• total volume of air voluntarily moved in one breath

• includes TV + IRV + ERV

  • 4-5 L in young men, 3-4 L in young women

what is residual lung volume (RLV or RV)?

• volume remaining in lungs after forced maximal expiration

• ~ 24% of FVC or 1.2 L in young men

• ~ 28% of FVC or 1.0 L in young women

• increases with age due to decreased lung tissue elasticity

what is dynamic ventilation dependent on?

• max stroke volume of lungs (FVC)

• Speed of moving a volume of air (breathing air)

  • Determined by lung compliance or resistance of respiratory passages to air and stiffness imposed by chest and lung

what is forced expiratory volme?

• measured over first second of FVC

  • (FEV_1.0/FVC) x 100 indicates pulmonary airflow capacity

  • equal to ~85% of FVC in healthy individuals

  • delineation point for airway obstruction is ≤ 70%

• FEV_1.0 as a percent of total of FVC reflects pulmonary expiratory power and overall lung resistance to air movement upstream in lungs

what are types of pulmonary impairments or diseases?

• obstructive (bronchial asthma)

  • increased lung resistance, impairs outflow timed vol and velocity

• restrictive (pulmonary fibrosis)

  • decrease lung compliance due to increased stiffness, change in pressure necessary to result in same change in end inspiratory vol

what is maximum voluntary ventilation?

• evaluates ventilatory capacity with rapid and deep breathing for 15 seconds

• MVV is extrapolated to volume ventilated in maximal exercise reflecting that exercise does not maximally stress how healthy a person breathes

how does exercise training improve voluntary ventilation?

• improves strength and endurance of inspiratory muscles

  • external intercostal, scalene, diaphragm

• increases MVV in normal COPD populations

exercise implications of gender differences in lung measures

• women have reduced lung side and airway diameter, smaller diffusion surface, smaller static and dynamic lung functions after statistical adjustment

• less fit women compared to highly trained men have limitations to expiratory flow

  • Requires greater respiratory muscle work and use of ventilatory reserve during maximal exercise

• smaller lung volume + high expiratory rate = higher demand on max flow capacity of airways and adversely affect alveolar to arterial oxygen exchange adversely affecting hemoglobin etc.

what is the relationship between lung function, aerobic fitness, and exercise performance?

• any activity strengthening respiratory muscle may increase pulmonary function somewhat

• regular endurance does not stimulate increase in functional capacity of lungs

• static and dynamic lung function test provide little info about severity of obstruction and restriction of lung disease

• normal pulmonary ventilation not a limiting factor in aerobic performance

how is pulmonary function predicted in men and women?

• employ analog to digital signal conversion and are more sanitary

• pulmonary function scores associate closely with stature (direct) gender (M > F), and age (inverse) used to predict avg lung function

what is minute ventilation?

• volume of air breathed each minute

  • breathing rate

• Breathing rate can increase to 35-45 breaths per minute during strenuous exercuse

• tidal volume (TV) trained and untrained can increase during exercise, but rarely exceed 60%

• V_E increases up to 100-200 liters per min depending on body size, health, and training during maximal exercise

what is alveolar ventilation?

• anatomic dead space (ADS) air in each breathe that remains in conducting regions of pulmonary system

  • portion of inspired air reaches alveoli and participates in gas exchange

  • increases as TV increases due to stretching of respiratory passages

• air does not enter alveoli, participates in gaseous exchange with blood

• essentially dynamic to identical atmospheric air except for 100% water vapor saturation at body temp

• alveolar ventilation determines gaseous concentrations at alveolar-capillary membrane

what does the ventilation-perfusion ratio show?

• represents ratio of alveolar ventilation to pulmonary blood flow

  • ventilation/perfusion = v:p ratio

• there is a disproportionate increases in ventilation to perfusion

what is physiological dead space (PDS)?

• portion of alveolar volume with a ventilation:perfusion ratio that approaches zero

• alveoli may not function adequately in gas exchange due to

  • under perfusion of blood

  • inadequate ventilation relative to alveolar surface

what happens when PDS increases to 50% of TV?

• impaired perfusion to pulmonary embolism

• impaired ventilation due to emphysema, fibrosis, asthmas

• adequate gas exchange becomes impossible when the dead space of lung increases to 60% of total lung volume

what are the zones of perfusion and what do they contain?

• 1: not present in healthy lung tissue, no perfusion

• 2: pulse flow, moderate perfusion, (pressure: pulmonary arterial > alveolar pressure > venous)

• 3: arterial and venous pressure exceeds alveolar pressure, optimal perfusion

• 4: high interstitial pressure increases vascular resistance, impair perfusion

rate vs depth

• in moderate exercise, well-trained athletes maintain alveolar ventilation by increases TV with only small increase in breathing rate

• each person develops a style of breathing where breathing rate and TV blend to provide effective alveolar ventilation

• TV in exercise increases by encroaching on both IRV and ERV

what is hyperventilation?

• increases in pulmonary ventilation that exceeds O₂ consumption and CO₂ elimination of needs of metabolism

what is dyspnea?

inordinate shortness of breath or subjective distress in breathing

what is the valsalva maneuver?

• closing the glottis following a full inspiration while maximally activating expiratory muscles

• creates compressive force that increases intra-thoracic pressure above atmospheric pressure

  • occurs normally in activities requiring a rapid max application force of short duration

what are the consequences of the valsalva maneuver?

• during static, straining type exercises reduces venous return and arterial blood pressure

  • diminishes brain’s blood supply producing dizziness or fainting

• once glottis reopens intra-thoracic pressure normalizes and blood flow establishes an “overshoot” in arterial blood pressure

what happens to the respiratory tract during cold-weather?

• not usually respiratory tract because of airway warming

• cold air has less moisture and pulls fluid from respiratory tract

• Fluid loss from airways contributes to dehydration, dry mouth, burning throat sensation, generalized irritation of respiratory passages

CH 13 what does arterial oxygen content depend on?

• concentration of inspired air, usually ambient

  • 20.93% O₂, 79.04% N₂, 0.03% CO₂

• pressure of ambient air

  • changes with weather and altitude

what does dalton’s law state?

total pressure of a gas mixture is equal to the sum of partial pressures of constituent gases in mixture

how do you compute partial pressure?

percentage concentration of specific gas divided by the total pressure of gas mixture

what happens to air as it enters the respiratory system?

• completely saturates with water vapor as it enters nasal cavities and mouth passing down respiratory tract

• water vapor dilutes inspired mixture

• effective PO₂ in tracheal air decreases by about 10 mm Hg from its ambient value of 159 to 149 mm Hg

what is the pressure of saturated air at body temperature?

PH₂O: 47 mm Hg

what is alveolar air?

• air that continues through to the alveoli

• enters alveoli from blood and dilutes the O₂ fraction

why is there more N₂ in alveolar air than ambient air?

• at rest and low intensity exercise VCO₂ produced is less than VO₂ consumed

what influences P_ACO₂, P_AO₂, P_AN₂?

• functional residual capacity

  • expiratory reserve volume + residual lung volume

  • causes relative stability

what does henry’s law state?

• mass of a gas that dissolves in a fluid at a given temperature varies in direct proportion to the pressure of gas over the liquid

what are factors that govern the rate of gas diffusion into a fluid?

• pressure differential

• solubility of gas in fluid

  • CO₂ most soluble, 25x more soluble than O₂

what happens during gas exchange in the lungs?

• alveolar gas-blood equilibrium takes place in 0.25 sec

• at rest, transit time of given erythrocyte past the vicinity of an alveolus through pulmonary capillary is ~0.75 sec

• during maximal exercise, velocity of pulmonary capillary blood flow increases ~50% over rest and pulmonary capillary volume increase ~300%

what are barriers of alveolar pulmonary capillary membrane for gas diffusion?

• liquid lining intra-alveolar membrane

• alveolar epithelial cells

• basement membrane of alveolar epithelial cell

• interstitial space ~0.3 um

• basement membrane of capillary epithelial cell

• capillary endothelium

• plasma in capillary blood

• erythrocyte membrane

• intracellular fluid in erythrocyte

• hemoglobin molecule

what impairs alveolar gas transfer?

• build up of a pollutant layer thickening alveolar membrane

• reduction in alveolar surface area

what do impairing factors do to alveolar gas transfer?

• each extends the time before alveolar-capillary gas equilibrates

• added demand for rapid gas exchange in exercises compromises aeration and negatively affects exercise performance

what happens to the alveoli when a person has emphysema?

• alveoli become damaged and collapsed

• decreases surface area for gas diffusion

what happens to a muscle cell during gas transfer?

• at rest, PO₂ in fluid outside cell averages 40 mm Hg and intracellularly PCO₂ averages 46 mm Hg

• in vigorous exercise, PO₂ in tissue falls toward 0 mm Hg and PCO₂ approaches 90 mm Hg

what forms due to pressure differences in gases between plasma and tissues?

diffusion gradient

how does the blood carry oxygen?

• in physical solution dissolved in fluid portion of blood

• in loose combination with hemoglobin (Hb)

  • partial pressure of oxygen dissolved in physical solution dictates the oxygenation of Hb to HbO₂

what would happen if there was no hemoglobin present in oxygen transport?

lack of venous oxygen reserve

where is hemoglobin contained?

red blood cells

how many red blood cells are normally present in males?

~ 27 trillion

how many red blood cells are normally present in females?

~ 24 trillion

how much hemoglobin are normally present in males?

14-18 g x 100/ mL

how much hemoglobin are normally present in females?

12-16 g x 100/ mL

what does the gender difference explain in oxygen carrying capacity of hemoglobin?

• slightly lower aerobic capacity of women relative to men

• higher hemoglobin concentration in men relate to stimulating effects of testosterone on RBC production

what makes up a molecule of hemoglobin?

• four oxygen binding sites, one for each Fe⁺⁺ atom in middle of porphyrin rings

• porphyrin rings 1-4, progressively greater O₂ affinity

• tense form of Hb binds with low affinity (tissues)

• relaxed form of Hb binds to O₂ with high affinity (lungs)

how is a hemoglobin molecule formed?

• O₂ binds to Fe⁺⁺ moving Fe⁺⁺ atom into the plane of porphyrin ring

• movement of Fe⁺⁺ pulls proximal histidine residue and its attached peptide helix toward the ring

• distal histidine residue forms a hydrogen bond with the O₂ bound to Fe⁺⁺

  • hydrogen bond results in a non-linear and weaker Fe⁺⁺-O₂ bond that helps offloading of O₂ at the tissues

  • bond results in change in valence state of iron

• peptide helix adjust conformation by rotating 15º of a₁B₁ dimer relative to a₂B₂

• movement of aB dimers alters conformation of Fe⁺⁺ at the other three un-liganded sites breaking extensive network of salt bridges, ionic bonds, and hydrogen bonds at subunit interfaces

how does anemia effect oxygen transport?

• iron deficiency without anemia does not impair oxygen transport and aerobic capacity, but iron deficiency can progress into anemia

• iron deficiency cause significant decrease in the iron content of RBCs and reduces blood’s oxygen-carrying capacity

• iron deficiency anemia causes a decreased oxygen pulse

• increased exercise heart rate is a compensatory response to decreased C_aO₂ in anemic subjects

• iron supplementation to eliminate anemia decreases the exercise HR response to a standard work rate increased oxygen pulse

what is cooperative binding?

• joining of O₂ with hemoglobin

• O₂ molecule binds to iron atom in one of four globin chains progressively facilitating the binding of subsequent O₂ molecules

what is the oxygen transport cascade?

how oxygen moves from ambient air at sea level to the mitochondria of maximally active muscle tissue

what is the relationship of PO₂ and hemoglobin in the lungs?

• hemoglobin does not fully saturate with O₂ when exposed to alveolar gas, at sea level P_AO₂ only achieves 98% O₂ saturation

• supplemental O₂ has little effect on oxyhemoglobin loading and increasing C_aO₂

• hemoglobin saturation with O₂ changes little until the PO₂ declines to about 60 mm Hg

what is sports anemia?

• hemo-dilution due to plasma induced volume expansion

  • ex: pre-training hematocit = 45.8%

    • post training hematocrit = 37.4%