arterial blood gas Flashcards
(18 cards)
metabolic acidosis
pH <7.35
HCO3 <22
hyperventilation
metabolic alkalosis
pH >7.45
HCO3 >26
hypoventilation
respiratory acidosis
pH <7.35
PaCO2 > 6
renal bicarbonate retention
respiratory alkalosis
pH > 7.45
PaCO2 <4.5
renal bicarbonate excretion
factor controlling the gas diffusion
con gradient
membrane thickness
temperature
surface area
ventilation/ perfusion matching: optimal balance between air reaching alveoli and blood reaching alveoli
Mechanism affecting ABG: respiratory minute volume (RMV)
total amount of air that an individual inhales in 1 min
-> RR X Tidal vol
Mechanism affecting ABG: alveolar ventilation
breath/1min x (Vtidal - Vdeadspace)
normal ventilation is most efficient
deep ventilation: increase vol of air exchanges but not partical in all situation
ventilation perfusion
air reaching alveoli / blood flow per min
V/Q not 1
gravity: lower lung has more blood (not fully oxygenated) while upper lung has more gas (not fully extracted)
V/Q mismatch
low V/Q: shunt perfusion (perfusion without ventilation)
high V/Q: dead space ventilation (ventilation without perfusion)
Low V/Q ratio: Blood O2 (PaO2) decrease
less ventilation relative to perfusion
hypoxemia
lung disease: pneumonia, asthma
High V/Q ratio
not enough blood flow for gas exchange
cause: cardiogenic shock, pulmonary embolism
correct V/Q:PaO2
controls perfusion by changing arteriolar diameter
correct V/Q:PaCO2
controls ventilation by changing bronchiolar diameter
V/Q <0.8
decrease PaO2; increase PaCO2
alveoli constrict
lower blood flow
V/Q >0.8
decrease PaO2; increase PaCO2
alveoli dilate (bronchoconstriction)
lower airflow
disease situation
oxygen therapy
positioning: prone positioning
