Acute Respiratory Failure Flashcards
(38 cards)
A V/Q mismatch of <1 means what?
there is a decrease in ventilation (decrease PaO2)
A V/Q mismatch of >1 means what?
there is dead space ventilation (decrease PaO2/increased PaCO2)
What type of condition would cause a decrease in ventilation (V)?
any disease that fills up the alveoli with fluid (e.g. pneumonia)
What condition is commonly associated with a decrease in perfusion (Q)?
PE
What are the 3 types of respiratory failure?
- hypoxemic respiratory failure
- hypercarbic respiratory failure
- mixed respiratory failure
Traditionally what test has been used to provide “cutoffs” to guide the clinician when determining respiratory failure?
ABGs
Using an ABG how is hypoxemia and hypercapnia defined?
- hypoxemia = RA PaO2 <50-60 mmHg
- hypercapnia = PaCO2 > 45 mmHg
What are the 3 tests used for diagnosing respiratory failure?
- physical exam
- ABG
- CXR
What is a late sign of respiratory failure?
cyanosis
What 3 components of the ABG will tell us about acid-base balance?
- pH
- pCO2
- HCO3
What component of the ABG will tell us about ventilation?
pCO2
What component of the ABG will tell us about oxygenation?
- pO2
- O2 saturation
How is hypoxic respiratory failure defined using an ABG?
- pO2 and O2 sat will be low
- room air PaO2 < 60 mmHg
How is hypercapnic respiratory failure defined using an ABG?
- decrease in pH and increase in pCO2
- PaCO2 > 45 mmHg with pH < 7.35
What 2 clinical features suggest acute respiratory failure?
- increased work-rate of breathing
- altered mental status
What are the 3 elements of an ABG?
- acid-base
- ventilation
- oxygenation
What does the oxygen hemoglobin dissociation curve say about the relationship pO2 and O2 saturation?
When the saturation is high you hold onto O2 better, when the saturation drops the ability to hold on O2 is rapidly decreased
A SaO2 of 90 is equal to a PaO2 of ___.
60
What are the 2 major measures of oxygenation?
- Alveolar-arterial gradient
- PaO2:FiO2 ratio
How is the A-a gradient determined? What does it provide?
- need to calculate Alveolar O2 then subtract from measured arterial O2 via ABG
- it provides a sense of “how hard” it is to transfer O2 from the alveoli to the blood
What change in A-a gradient usually indicates a V/Q mismatch or a shunt?
high gradient (normal = <10 torr but increases with age)
A ____ paO2:FiO2 ration is bad.
low
If a patient presents in respiratory distress but has a _____________ what diagnosis should you consider?
- normal CXR
- CXR with alveolar pattern
- CXR interstitial pattern
- CXR with lobar consolidation
- CXR with hyperinflated lungs
- PE
- CHF, ARDS
- mild CHF, pulmonary fibrosis, atypical pneumonia
- pneumonia
- COPD
What CXR pattern is this?
normal CXR
