gas exchange Flashcards
what is daltons law
total pressure of a mix of gases is equal to the sum of the partial pressures of the individual component gases
what is the composition of dry air
21 oxygen
78 nitrogen
.1 argon
what is henrys law
explains how gasses dissolve across the alveoli-capillary membrane
-amount of gas absorbed by a liquid is directly proportional to the partial pressure and solubility of the gas in the liquid
altitude=less pressure
when you have a lot of atmospheric pressure, it will force more molecules to diffuse from capillary to blood= dissolution of O2 into blood due to pressure gradient
what is ficks law of diffusion
passive exchange of gas between lung and blood and blood and tissues/organs is dependent on:
- concentration gradient/partial pressures of gases
- solubility of gases
- surface area available for diffusion
- membrane thickness
diffusion of oxygen is better w more surface area
supplemental O2 change pressure gradient of O2
when is diffusion less likey to occur
when the interstitial is wider and thicker
what provides surface area for gas exchange with pulmonary blood
alveoli
how does lung disease impair diffusion
-during exercise, pulm blood flow is quicker which shortens time available for gas exchange
-lung disease are unable to oxygenate the pulm blood fully and have a limited ability to exchange gases fully
=impaired ADLS and exercise
talk about CO2 and the membrane
it diffuses across the alveolar-capillary membrane 20x faster than oxygen so less likely to compromise co2 transfer from blood to alveoli
what is oxygen transport
amount of o2 delivered to tissues
what is o2 content of blood dependent on
- PaO2
- hemoglobin concentration
how is o2 transported
2 forms:
- dissolved in plasma
- reversibly bound to hemoglobin
what is the bohr effect
promotes unloading (muscle)
- increases co2
- decreases ph
- decreases Hb affinity for o2
how is co2 transported
3 ways:
- bicarbonate in RBC and plasma
- carbaminohemoglobin
- dissolved gas
what is the haldane effect
-deoxyhemoglobin can carry more o2
what happens in pulm circulation with low oxygen
vasoconstriction
explain pulm circulation
- rate of BF through pulm circulation = flow of rate through systemic circulation
- pulm vascular resistance (afterload) low
- autoregulation: hypoxic vasoconstriction that is when pulm arterioles constrict when alveolar po2 decreases…matches ventilation and perfusion ratio
what are local factors for vasodilation
- low ph
- high co2
- nitric oxide
- decreased oxygen
what part of the lung does the majority of BF and ventilation go?
base
are ventilation and perfusion evenly matched across the lung?
no
what is a low v/q?
shunt
what is a high v/q?
dead space
what is a physiologic shunt
VV #1 reason people desaturate -pulse ox here is lower than normal -blood flow without air flow -blodo has low o2 and high co2 poorly oxygenated
what is physiologic deadspace
V>Q or Q
what is perfusion
heterogenous
- gravity effect
- cardiac output
- pulm vascular resistance
what is zone I ventilation and perfusion
alveoli > arterial> venous
-airflow > BF (deadspace )
what is zone II ventilation and perfusion
arterial <> alveoli > venous
-airflow <> BF
what is zone III ventilation and perfusion
arterial > venous> alveoli
-BF > airflow (shunt)
what is the cause of desaturation
ventilation or perfusion issue
what happens to V and Q during exercise?
both increase with workload
at rest, V/Q mismatched but during exercise they are matched
breathing more deeply because as workload increases , CO2 must be blown off
CO2 values stay the same until anaerobic threshold is hit which = Co2 dropping
