RESPIRATORY LECTURE

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RESPIRATORY LECTURE
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Function

• O2/CO2 gas exchange and acid/base balance
• Pulmonary Respiration - exchange of gases between
  atmosphere and blood and cells
• Pulmonary ventilation inspiration/exhalation
• External respiration - exchange of gases in lungs
• Internal respiration - exchange of gases in
  tissues

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Physiology

• Warm, moisten and filter incoming air
• Surface for Olfactory stimuli
• Hollow chambers for speech sounds

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Clinical

• Rhinoplasty - nose job
• Laryngitis - inflamed larynx
• Cancer of the larynx smoker
• Tracheostomy - open air passages
• Nebulization - droplets of medication
• Atelectasis - collapsed lung due to change in
  pressure from opening thorax
• Pleurisy - inflamed pleural membranes
• Asthma - sporadic narrowing of air passages
• Emphysema - alveolar walls disintegrate --gt large
  holes
• Hypoxia - general low level of O2 available -
  tissue O2 def.
• Hypoxic - low P O2 in arterial blood
• high altitude, obstructed air passages, fluid in
  lungs
• Anemic - too little functional Hb
• hemorrhage, anemia, CO2 poison and Hb can't carry
  regular O2 amount
• Stagnant - blood can't carry fast enough
• heart failure, circulatory shock
• Histotoxic - enough O2 from blood tissues can't
  use properly
• cyanide - blocks metabolic stuff to use O2

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The physics of it all

• Inspiration - need to increase size of lungs in
  order to inhale and bring air in
• Pressure just prior 760 mmHg (approx
  atmospheric)
• Boyle's Law if you alter pressure you will
  also alter volume
• P1V1 P2V2
• http//www.grc.nasa.gov/WWW/K-12/airplane/aboyle.h
  tml
• increase volume? decrease pressure
• decrease volume ? increase pressure
• pressure x volume a constant at the same temp
• P xV Constant
• means that pressure and volume are inversely
  proportional
• With respiration you use the diaphragm in order
  to change the size/volume
• When there is a decrease in pressure in alveoli
• ( 760 mmHg ? 758 mmHg)? air rushes in
• Muscles
• costal breathing - intercostal m. from thoracic
  spinal nerves
• diaphragmatic breathing - contraction and descend
  of diaphragm
• most important
• sternocleidomastoid may raise sternum
• pectoralis minor - raises ribs

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The physics of it all

• Expiration
• lung pressure gt atmospheric pressure
• passive process - no muscles
• recoil of stretched elastic fibers
• pull of alveolar film
• starts when inspiration muscles relax
• lung volume decreases ? increased pressure 762
  mmHg
• Addition through muscles - abdominal and
  intercostal muscles

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Compliance expandability

• Resiliency of the lung tissue
• may decrease in lung tissue damage
• TB ? scars, pulmonary edema, deficiency in
  surfactant, paralysis of intercostals
• Emphysema increases compliance
• CT structure is damaged
• Surfactant - holds alveoli open
• Other factors include mobility of thoracic cage -
  arthritis etc

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Airway resistance diameter decreases ? increased
resistance

• Chronic Obstructive Pulmonary Disease (COPD) -
  due to asthma or emphysema
• Both may lead to collapsed passageways

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Pulmonary volume

• Tidal volume - volume of air inspired or expired
  normal quiet breathing 500ml 350 ? alveoli
• Anatomical Dead Space - rest stays in airspaces
  (trachea) 150ml
• Minute volume of Respiration (MVR) - total amount
  of air taken in one minute
• MVR tidal volume x breaths per minute 500ml x
  12 6000ml/min
• Inspiratory Reserve volume - extra that you can
  take in 3100ml
• 3100 500 from TV ? 3600ml total intake
• Inspiratory capacity - 3600ml tidal volume
  inspiratory reserve volume
• Expiratory Reserve volume - extra that you can
  exhale 1200ml ? 1700ml total exhale amount
• Residual volume 1200 ml to keep alveoli open
• Functional reserve volume - residual volume exp
  reserve volume 2400ml
• Vital capacity - inspiratory reserve volume
  tidal volume exp reserve volume 4800ml
• total lung capacity total of all volume 6000ml

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CO2 - O2 exchange

• O2 and CO2 diffuse down the concentration
  gradient
• Charles' Law - temperature is proportional to
  pressure
• P/T constant
• increase temp ? increase pressure
• Gay-Lussac Law - volume changes w/ temperature
  and therefore so does pressure
• V is proportional to T
• Gas Equation PV nRT
• n number of moles of gas R gas constant
• Daltons Law - this equation applies to gas
  mixtures as well as pure gases
• http//members.aol.com/profchm/dalton.html
• Henry's law
• The quantity of a gas that dissolves in a liquid
  is proportional to partial pressure and
  solubility coefficient
• http//dwb.unl.edu/Teacher/NSF/C09/C09Links/www.ch
  em.ualberta.ca/courses/plambeck/p101/p01182.htm
• air 75 N2 which is a low solubility
  coefficient at sea level
• under higher pressure N2 will go into solution in
  the plasma
• scuba problems ? slow ascent to breath N2 out of
  lungs rather then letting it stay in the tissues

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Hb - polypeptide

• 4 subunits of Fe for O2 to attach to can carry 4
  O2
• Alpha and Beta subunits of the polypeptide
• Positive cooperatively - bind one O2 the rest
  will bind easier
• Mb O2 storage in the muscle - only binds one O2

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Oxygen Dissociation Curves

• At rest P O2 alveolar air 105 mmHg
• P CO2 of alveolar air 40 mmH
• P O2 of deoxygenated blood 40 mmHg
• P CO2 of deoxygenated blood 45 mmHg
• P O2 oxygenated blood 105 mmHg
• P CO2 oxygenated blood 40 mmHg
• only 25 of O2 is available - deoxygenated
  blood retains O2
• Rate of exchange in the lungs
• Partial pressure difference
• as long as P O2 alveolar gt P O2 deoxygenated
  blood ? diffusion
• high altitude - less P O2 of alveolar
• Surface area for gas exchange - pulmonary
  disorder ? decrease area
• Diffusion distance - edema (fluid in lungs) ?
  increase distance
• Breathing rate and depth - slow RR ? slower
  exchange
• Binding to Hb - depends upon P O2
• increase P O2 ? increase saturation of Hb
• Hb 75 sat'd at P O2 40 mmHg - (at rest
  pressure)

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Factors Affecting the curve

• Temp - Hb harder to load O2 and gives it up
  easier for the tissues that need it
• curve shift to the left
• pH - increase in CO2 --gt H2CO3 --gt H and HCO3-
• Hb harder to load O2 and gives it up easier for
  the tissues that need it
• acid alters Hb structure and cannot carry O2 as
  well
• curve shifts to the left Bohr Effect
• 2,3 DPG diphosphoglycerate from anaerobic
  metabolism (glycolysis)
• Produced by RBC's in low O2 - binds to Hb
• 2,3 DPG - increased by GH, Epinephrine,
  Norepinephrine, testosterone
• Favors O2 unloading - decreases affinity of Hb to
  O2
• curve shifts to the left
• P CO2 as it rises ? Hb releasing O2 and taking
  on CO2
• Fetal Hb - saturates w/O2 faster
• binds to 2, 3, DPG less strongly
• Shifts curve to left
• takes O2 from maternal blood - which is low in O2
  already vs atmospheric air

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Oxygen loading and unloading

• Lungs
• H and Hb ? HHb
• O2 replaces H of HHb in lungs ? HbO2
• Tissues
• CO2 and H2O from cell metabolism ? plasma and
  RBCs
• CO2 and H2O converted to H2CO3 ? H and HCO3-

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Control of Respiration

• Nervous
• Medulla - inspiration stimuli
• basic rhythm
• autorhythmic neurons phrenic nerve to diaphragm
• Pneumotaxic area of pons
• inhibitory to inspiratory area
• limit duration of inspire
• Apneustic area of pons
• transition of inspire to expire
• overrides pneumotaxic when pneumotaxic is
  inactive
• activate inspire -prolong it ? inhibit expire
• Cortex - voluntary
• limited by CO2 and H in the blood
• Preset - may increase in preparation for exercise

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Control of Respiration

• Receptors
• Stretch in walls of bronchi --gt vagus --gt
  apneustic area inhibited
• decrease stretch --gt turn off inhibit of
  apneustic area --gt inspire
• Chemical - chemoreceptors
• central - CO2 as it diffuses across BBB - near
  medulla
• peripheral - in carotid and aorta
• H, CO2 and O2 (a little - since blood remains
  fairly saturated)
• Proprioceptors - movement in joints
• Baroreceptors carotid and aorta - detect BP
• Other
• Temp/fever ? increase RR to cool off
• Pain
• sudden ? stop RR
• chronic ? increase
• Irritation of air passages - mechanical or
  chemical