DSA #3 Flashcards
V/Q ratio of 0 indicates what?
no ventilation ie. peanut stuck in throat
arterial blood gas composition will equal venous blood
creates a physiological shunt
what effect does hypoxic vasoconstriction have?
happens when the V/Q ratio is low, the V/Q raised and brings arterial blood gases closer to expected values
what happens when the V/Q ratio is high?
bronchoconstriction, to INC resistance and DEC ventilation thus limiting alveolar dead space
what is anoxia?
total absence of oxygen being delivered to the tissues
describe hypoxic hypoxia
PaO2 is below normal bc alveolar PaO2 reduced
blood cannot fully equilibrate with alveolar air
describe anemic hypoxia
O2 carry capacity of the blood is reduced
ex. CO
describe circulatory hypoxia
tissue not receiving sufficient O2 bc the heart cannot pump blood to the tissue
ex. sickle cell,
describe histotoxic hypoxia
cells poisoned, tissue unable to use O2
ex. Cyanide
quickly describe what is fucked up with each type of hypoxia: hypoxic anemic circulatory histotoxic
lungs
blood
tissue
everything is working properly
describe characteristics of CSF
very little protein
NO cholesterol
like plasma and absorbed in the blood
more HCO3-
how is chronic hypercapnia fixed by choroid plexus?
chronic hyopcapnia?
HCO3- added to CSF, H+ moved into the blood
H+ added to CSF, HCO3- moved into blood
oxygen content equation
oxygen content = oxygen capacity x %saturation
oxygen capacity = amt Hb in blood x 1.34
describe the 3 steps in an acute response to altitude (hypoxia)
- peripheral chemoreceptors INC firing rate at a PaCO2 of 70 mmHg and INC ventilation
- Inc ventilation will INC PaO2 and DEC PaCO2
- DEC PaCO2 will cause a DEC in the firing rate of central chemoreceptors
name the 3 big adjustments of acclimatization
- cells of choroid plexus have a CSF that is more basic, add H+ to it, but still maintain a PaCO2 lower than normal
- INC EPO production –> INC Hb content of blood
- INC # and size of mitochondria, more efficient O2 utilization
what happens in altitude sickness?
cerebral vasculature will dilate in response to hypoxia
this causes INC perfusion pressure and filtration leading to mild edema
pulmonary edema is a side effect of altitude, when does it occur and for what reason
rapidly ascend greater than 2500m and then do physical activity OR live at altitude, come down to sea level then go back up
edema due to INC pulmonary vascular permeability, pulmonary hypertension occurs but LA pressure is NORMAL
total barometric pressure equation
descend 10m = INC 1 atm
pressure due to water + pressure due to air
ie. 4atm + 1atm
what happens in hyperbaric conditions
how can it be used for treatment?
O2 toxicity leading to superoxide anion and peroxide production
CO poisoning
what is nitrogen narcosis?
high [N2] exerts effects on neurons in CNS similar to alcohol
what are bends or decompression sickness?
ascending too rapidly from underwater
N2 dissolves in plasma while submerged, when you ascend slowly it has time to get back to the lungs to convert to the gas state there, but if ascent is too rapid, it will convert to gas while in blood
this is painful
what happens in an air embolism?
glottis is closed and air is not allowed to leave the lungs during ascent so it goes into the blood
PV may rupture creating an air embolus which can kill
V/Q ratio of infinity indicates what?
pulmonary embolism which blocks blood flow
creates alveolar dead space
