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Lecture 5

PHSI 208 Lecture Notes - Lecture 5: Pulmonary Edema, Pulmonary Compliance, Partial Pressure


Department
Physiology
Course Code
PHSI 208
Professor
Baillie Landon
Lecture
5

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!PHSI!208.6!–!University!of!Saskatchewan!
Prof:&Landon&Baillie&
!
January'20,'2016'–'Respiratory'5'
&
Diffusion!is!random!movement!of!molecules!from!a!region!of!high!concentration!to!a!region!of!
low!concentration.!Factors!that!affect!the!random!movement!of!gas!molecules!from!a!region!of!
high!partial!pressure!to!a!region!of!low!partial!pressure!include:!
Concentration!gradient!
Surface!area!
Barrier!permeability!
Diffusion!distance!
Solubility!of!gas!
!
Surface!area,!diffusion!distance!and!barrier!permeability!are!constant!under!normal!conditions.!
In!a!healthy!individual,!concentration!gradient!is!variable!and!the!main!determinant!of!
diffusion,!determined!by!rate!of!ventilation.!
&
Pathologies&That&Cause&Hypoxia&
Pathology!
Description!
Results!In/Causes…!
Emphysema!
Proteolytic!enzymes!break!down!
lung!tissue.!Destruction!of!alveoli!
means!less!surface!area!for!gas!
exchange.!
Decreased!surface!area.!
Fibrotic!lung!disease!
(Pulmonary!fibrosis)!
Thickened!alveolar!membrane!
slows!gas!exchange.!Loss!of!lung!
compliance!may!decrease!alveolar!
ventilation.!
Decreased!barrier!permeability.!
Pulmonary!edema!
Fluid!in!interstitial!space!between!
the!capillaries!and!alveoli!increases!
diffusion!distance.!Arterial!PCO2!
may!be!normal!due!to!higher!CO2!
solubility!in!water.!
Increased!diffusion!distance.!(ex:!
when!the!left!ventricle!of!the!heart!
starts!to!fail).!
Asthma!
Increased!airway!resistance!
decreases!alveolar!ventilation.!This!
is!considered!chronic!inflammation!
and!results!in!the!bronchioles!
constricting.!
Decreased!concentration!gradient.!
!
Gas&solubility&affects&diffusion:&The!alveoli!are!lined!with!liquid.!The!small!interstitial!space!
between!alveoli!and!capillaries!contains!liquid!and!the!blood!itself!is!liquid,!therefore!
respiratory!gases!must!be!soluble!in!liquids.!The!movement!of!gas!molecules!from!air!to!liquid!
is!directly!proportional!to!3!factors:&
1. The!pressure!gradient!of!the!gas!
2. Solubility!of!gas!in!liquid!
3. Temperature-relatively!constant!within!respiratory!system.!
!
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