Acute Respiratory Failure Flashcards
define respiratory failure
dysfn w/ gas exchange, can be life threatening
hypoxic: PaO2 less than 60
hypercarbic: PCO2 over 50
sx of r failure
dyspnea, tachycardia/tachypnea, cyanosis
impaired mental status, headache, coma from hypercapnia
contrast dead space and shunt
shunt has perfusion but no ventilation
dead space is ventilation w/o perfusion
examples of shunt
atelectasis, pneumonia, edema
examples of dead space
conducting airways, pulm bullae, PE
good way to tell if its shunt
does not respond much to supplemental O2
how to calculate the Aa gradient
PAO2-PaO2
PAO2 calculated w/ alveolar gas equation:
PAO2= PIO2- (PACO2/R)
PIO2=FiO2(Patm-PH2O)
meaning of Aa gradient
measure of gas exchange efficiency, will be elevated V/Q mismatch, diffusion impairment, and shunt
normal Aa gradient
age/4+4
how to tx shunt
decrease shunt (eg tx w/ antibiotics), open alveoli (PEEP), maybe intubate
compensation during PE/ dead space
hyperventilation helps prevent hypercapnea
can be made worse if sedated and/or kept at low RR- prevent compensation and worsen hypercapnea
diffusion limitation effect on exercise
become quickly hypoxic, increased cardiac output causes faster perfusion, O2 does not have enough time to equilibriate w/ thickened diffusion barrier
no “reserve” time
Aa gradient w/ hypoventilation
normal!;
6 possible causes of decreased ventilation
low respiratory drive (OD), nerve conduction problems, muscle disease in the respiratory system, chest wall diseases, lung disease (COPD), upper airway obstruction
COPD and respiratory failure
can cause both hypercapneic and hypoxemic- elevated Aa from V/Q mismatch, hypercapnea from lower alveolar ventilation and increased work of breathing
