Vent, Resp Failure - Muthiah Flashcards
what specifically do the central chemoreceptors respond to and what is the effect?
they respond to increased [H+], or dec pH, in the CSF as a result of inc pCO2 - the result is in an increase in ventilation to exhale more CO2
What is Muthiah definition of ventilatory failure
any time CO2 is retained (hypercapnia)
respiratory failure can be of what two types
type I - pure hypoxemia
type II - hypoxemia + hypercapnia (this is ventilatory failure)
What are 3 mechanisms of hypoxemic failure
1 - V/Q mismatch
2 - shunt
3 - exacerbated by low mixed venous O2
what are 2 mechanisms of hypercapnic failure
1 - decreased minute ventilation (MV) relative to demand
2 - increased dead space ventilation
recall the 3 mechanisms of hypoxic resp failure that cause a wide A-a
1 - V/Q mismatch
2 - R - to - L Shunt
3 - diffusion limitation
recall the 2 mechanisms of hypoxic resp failure that causes normal A-a
1 - hypoventilation
2 - decreased PiO2
what is the essential pathophys behind hypercapnia with regards to the alveoli
in order to have retained CO2, there must be a decrease in alveolar ventilation at some level
what are 4 general causes of hypercapnic resp failure
1 - central hypoventilation
2 - neuropathies
3 - muscle (pump) failure
4 - airway obstruction
what are 3 causes of a right shift in the hemoglobin binding curve (i.e. decreased affinity for O2)
1 - inc Temp
2 - acidosis (indication of inc CO2)
3 - inc 2,3 DPG
mnemonic TAP
What 4 factors will cause a left shift of the hemoglobin binding curve (i.e. increased affinity for O2)
1 - dec Temp
2 - alkalosis
3 - dec 2,3 DPG or fetal hemoglobin (does not bind 2,3 DPG as well)
4 - CO (carbon monoxide)
Formoterol is a long acting Beta 2 agonist with a rapid onset of action. Can it be used for rescue?
no
What management strategy of respiratory failure should you not overlook and what is the methodology behind it
hydration - pt is losing water as moisture in their breath, and these pts are hyperventilating, so losing more water than nml
What treatment strategy, as an alternative to intubation, can be applied to a pt with respiratory failure from and asthma or COPD exacerbation that is worsening?
BiPap - noninvasive way to provide pressure support and PEEP
What is the Haldane effect?
Haldane effect: deoxygenated blood has a better capacity to carry CO2; oxygenated blood has a reduced capacity to carry CO2
In hypoxic individuals, some CO2 is bound to hemoglobin as carbaminohemoglobin. Supplemental O2 100%, will raise the PaO2 and the SaO2. CO2 must be displaced from Hb, and this readily happens in the presence of inc pO2 (This is the Haldane effect - inc O2 causes displacement of CO2 so O2 can bind, and vice versa) this displaced CO2 then can only dissolve in the blood and this raises the PCO2
what are two indications that a pt is hypoxic? one physical exam finding, one lab finding
tachypnea and an O2 sat less than 90
what is a good indication of hypercapnia (looking at blood)?
a bicarb higher than 30 on the serum analysis
what is the evaluation of choice in pts suspected of PE?
helical CT
when should you not do PFTs?
acute situations - ARDS, pneumonia, PE, other acute shit
How do you treat the pt in hypoxic respiratory failure?
supplemental O2
What is the most common mechanism of hypoxemia?
V/Q mismatch
Again, how do we differentiate between V/Q mismatch and Shunt as mechanism for hypoxia?
give supplemental oxygen
if it corrects - V/Q mismatch
if not - shunt
in what patients do anticholinergics work best in?
COPD - often times can have an inc vagal tone
How do you know if the pt is getting tired (i.e. losing muscular ability to breathe?)
increased somnolence, decreased RR, etc.
what is significant of an acute pt that is getting tired - what is the mechanism of this exacerbation? (I can’t think how to ask this)
CO2 acts as a narcotic - why fatigue and CO2 retention is a vicious cycle - as pt gets tired, they breathe less, and expel less CO2, which causes more fatigue and less breathing
what will ABG show in pt that is getting tired
CO2 retention
Should pts w/ COPD be given O2, since it causes the pt to retain CO2? and why? (What are the 2 reasons for inc CO2)
yes they should
the resultant V/Q inequality, along with the Haldane effect are the most significant causes of hypercapnea
Supplemental oxygen given to a pt w/ chronic hypercapnia can cause an increase in PCO2. what is the mechanism behind the worsening V/Q mismatch?
worsening V/Q mismatch: supplemental O2 demolishes the hypoxic induced vasoconstriction of the pulmonary vasculature
release of hypoxic vasoconstriction in poorly ventilated areas of the lung is caused by an increase in PaO2
Consequnce: there is increased blood flow to low V/Q areas and a worsening of V/Q inequality which exaggerates the degree of CO2 retention
