Oxygen therapy physiology

hypoxia

low levels of O2 in the tissues leading to cellular disturbances, inability to make ATP, tissue injury/death

hypoxemic

occurs when there is low levels of O2 in the blood which can occur from dec O2 tension or anything effecting ability to do gas exchange

anemic

occurs when there is an issue w O2 carrying capacity from hemoglobin levels leading to low O2 levels

stagnant

occurs when there is a dec perfusion or BF leading to dec lvls of O2

histotoxic

occurs when there is abnormal metabolism or dec tissue metabolism leading to ability to use O2

atmospheric pressure

the total pressure of gas mixture or the sum of pressures of each gas in the mixture

partial pressure

the pressure each gas exerts

21%

the partial pressure of O2 is

alveolar has equation

the estimation of how much O2 is in the alveoli and can give the indication of gradient used for gas exchange

true

PiO2 is the fraction of inspired O2 considering the amt of barometric pressure and humidifying factors in the airways

t or f

false

PiO2 is the pressure of inspired O2 considering the amt of barometric pressure and humidifying factors in the airways

t or f

V/Q mismatch, shunt causing incomplete diffusion

a decrease in pressure from the alveolar to the arterial O2 pressure occurs from

Fick law for diffusion

factors which effect the rate of gas diffusion

area

rate of diffusion is directly proportional to the ____ where a larger size inc rate of diffusion

difference in gas

rate of diffusion is directly proportional to the _____ where it is proportional to driving pressure

thickness

rate of diffusion is inversely proportional to the ____ where a larger value dec ability to diffuse

true

PAO2 is the driving force of diffusion

t or f

false

PaO2 is the driving force of diffusion

t or f

shunt

occurs when there is dec ventilation/dec PAO2 leading to a dec PaO2

deadspace

occurs when there is dec perfusion leading to dec PaO2

FiO2

the fraction or % of concentration of inspired O2

true

when FiO2 increases from supplemental O2 then we see inc in PiO2 thus a higher pressure gradient for inc force of O2 diffusion

t or f

false

when FiO2 increases from supplemental O2 then we see dec in PiO2 thus a higher pressure gradient for inc force of O2 diffusion

t or f

alveolar arterial gradient

the gradient of pressure coming from the alveoli to the arterioles and can determine rate of diffusion

true

in healthy people not all O2 from the alveoli can go to the blood and a small amt is healthy

t or f

false

in healthy people all O2 from the alveoli can go to the blood and a small amt that is shunted indicates pathology

t or f

true

the bottom of the lungs has better perfusion compared to ventilation

t or f

false

the bottom of the lungs has better ventilation compared to perfusion

t or f

normal A-a gradient

a type of hypoxemia where an issue occurs at ventilation such as low inspired O2 and alveolar hypotension leading to dec O2 in tissues

increased A-a gradient

a type of hypoxemia where an issue occurs at diffusion across the barrier such as VQ mismatching, shunts and dec diffusion effects leading to low O2 in tissues

PF ratio

the ratio of partial pressure of O2 in arterioles and fraction of % O2 inspired to help indicate a pulmonary shunt factor

true

a PF ratio where PaO2 is 100mmhg is 475 mmhg

t or f

mild ARDS

PF ratio of 200-300mmhg can indicate ___

moderate ARDS

PF ratio of 100-200 mmhg can indicate ____

severe ARDS

PF ratio of less than 100 mmhg can indicate ___

PaO2

O2 which is transported vis physically dissolving in plasma

SaO2

O2 which is transported via chemically binding to Hb which is measured directly from arterial blood

true

when o2 diffuses across the barrier it immediately dissolves into plasma

t or f

false

when o2 diffuses across the barrier it immediately binds to Hb

t or f

low solubility coefficient

O2 in plasma has a ____ meaning it does not dissolve well in blood and enters the RBC

true

the amt of Hb binding or SaO2 is determined by PaO2

t or f

false

the amt of Hb binding or SaO2 is independent to the PaO2

t or f

hemoglobin

a molecule w 4 binding sites for O2 and can carry 1.34 ml of O2

O2 hb/total hb

SaO2 ratio is the

true

SvO2 is generally lower than SaO2 but never 0

t or f

CaO2

the O2 conc in arterial blood or the total # of O2 molecules in arterial blood including the ones bound to Hb and dissolved in plasma

rate of O2 delivery

depends on the CO multipled by the CaO2

O2 bound to Hb

depends on the max O2 carrying capacity of Hb, Hb conc, and SaO2

dissolved O2

depends on the partial pressure of O2 and the solubility constant of O2

true

CaO2 is impacted by SaO2, hb and PaO2 but each component is it’s own thing

t or f

S shaped curve

PaO2 and SaO2 have an ____ relationship

flat portion/>60 mmhg

the ___ of the SaO2 and PaO2 curve indicates major changes in PaO2 has little effects on SaO2

steep portion/20-60mmhg

the ___ of the SaO2 and PaO2 curve indicates minor changes in PaO2 has large effects on SaO2

true

PaO2 is the driving force for O2 binding to Hb but the amt of Hb is independent from the PaO2

t or f

false

PaO2 is the driving force for O2 binding to Hb and the amt of Hb is dependent from the PaO2

t or f

true

dissolved O2 is not sufficient for O2 delivery

t or f

false

dissolved O2 is sufficient for O2 delivery n emergencies

t or f

strong affinity

when PaO2 is >60mmHg then O2 has a _____ to hb

weak affinity

when PaO2 is 20-60mmHg then O2 has a _____ to hb

left shift

when temp, DPG, and [H+] decreases there is a _____ in the PaO2 and SaO2 curve showing inc affinity

right shift

when temp, DPG, and [H+] increase there is a _____ in the PaO2 and SaO2 curve showing dec affinity

normal

if PaO2 is 80-100 mmhg and SaO2/SpO2 is 95-100% then hypoxemia is classified as

mild

if PaO2 is 60-79 mmhg and SaO2/SpO2 is 90-94% then hypoxemia is classified as

moderate

if PaO2 is 40-59 mmhg and SaO2/SpO2 is 80-89% then hypoxemia is classified as

severe

if PaO2 is <40 mmhg and SaO2/SpO2 is <75-80% then hypoxemia is classified as

SpO2

the estimate of SaO2 using pulse oximetry using infrared and red light wavelength to absorb bound and unbound Hb

reflectance

a type of pulse oximetry used when the light source and detector are on the same side

trasmittance

a type of pulse oximetry used when the light source and detector are on the opposite side

occult hypoxemia

occurs when someone has hypoxemia but the pulse oximeter reads SpO2 as normal due to high melanin conc

Artero-venous difference

the difference bw amt of O2 in arteries and how much is in the venous system or how much O2 is extracted

true

in cases of hypoxia in limbs there will be an overall dec venous O2 content

t or f

false

in cases of hypoxia in limbs there will be an overall inc venous O2 content

t or f

VO2

if ___ is increased during rest consider the risk of tissue hypoxia

lactic acid

in critical illnesses ___ can be overproduced in ischemic tissue due to hypoperfusion

ECMO

a pump and oxygenator which can replace a heart and lung fxn in cases of failure