Diagnostic Testing - Core Concepts Flashcards
What is the quick alveolar air equation?
(FiO2 x 7) - (PaCO2 + 10)
In a pinch, FiO2 x 7 should be close enough
How do you calculate the A-a gradient?
PAO2 - PaO2
Find PAO2 with the alveolar air equation, then subtract your arterial (ABG) PaO2.
What is normal a/A ratio?
a
___
A
A ratio lower than ___ indicates surfactant therapy.
0.8 - 0.9
Lower than 0.2 is an indication for surfactant usage. A higher number indicates improvement.
A normal shunt is ___%, and increases by ___% for every increase of ___ in the A-a gradient.
Normal is 5%. Shunt increases by 5% for every increase of 100 in the A-a gradient.
An A-a gradient of 200 would correlate with a shunt of what %?
15%. Start with the normal of 5%, and add 5% for every 100 torr of A-a gradient.
An oxygenation index (OI) of > ___ indicates the need for nitric oxide (iNO)
An oxygenation index (OI) of > ___ indicates the need for ECMO, and is indicative of an 80% mortality rate.
> 25 indicates nitric oxide therapy.
> 40 indicates ECMO therapy.
What is a normal PF ratio?
380 or greater.
PF ratio of:
201-300 indicates ___ ARDS
< 200 indicates ___ ARDS
< 100 ___ ARDS
Mild
Moderate
Severe
What is a normal SaO2/FiO2 ratio? is it less invasive that a P/F ratio?
400
Yes
What is a normal Vd/Vt ratio? (deadspace to tidal volume ratio)
20% - 40% (up to 60% in mech vent patients)
What is the deadspace to tidal volume equation? (Vd/Vt)
PaCO2- PetCO2
_____________ x 100
PetCO2
The most common pathology related to a high deadspace to tidal volume ratio is?
Pulmonary embolism (PE)
A 3L calibrating syringe has an acceptable accuracy range of what %, and what volume?
3.5%, which is about 100 ml. If the syringe is considered accurate, it’s volume will be between 2.9L - 3.1L
The vital capacity measures volume and identifies (restrictive/obstructive) disorders?
Vital capacity identifies restrictive disorders.
The FEV1 measures flow and identifies (obstructive/restrictive) disorders?
FEV1 identifies obstructive disorders.
is 80-100% of predicted a normal result on a PFT?
Yes.
Are CF, bronchitis, asthma, and bronchiectasis obstructive or restrictive?
Obstructive. EVERYTHING else is restrictive.
MIP (maximum inspiratory pressure) of less than ___ indicates inspiratory muscle weakness
<20
MEP (maximum expiratory pressure) of less than ___ indicates poor ability to clear secretions.
<40
Normal SpO2 for newborns?
Normal SpO2 for children?
Newborns: 90-95
Children: 93-97
What is the ideal temperature range for transcutaneous monitoring?
41C - 44C
A transcutaneous monitoring electrode should be moved to a new site in how many hours?
If erythema (redness/blistering) occurs, what should you do?
Move electrode every 4-12 hours.
Move the electrode, and change sites more frequently.
In what order do you assess blood gas values on the exam?
VOCP!!!
CO2 first
PaO2, FiO2
pH
Assess the following blood gas results in order of the NBRC guidelines:
pH
PaCO2
PaO2/FiO2
VOCP!!!
PaCO2 first (assess ventilation)
PaO2/FiO2 (assess oxygenation)
pH (if both are acceptable)
Is the patient ventilating, according to the NBRC guidelines?
If PaCO2 is normal?
if PaCO2 is increased?
if PaCO2 is decreased?
If PaCO2 is normal? Yes the pt is ventilating.
if PaCO2 is increased? No. Change settings.
if PaCO2 is decreased? Yes the pt is ventilating.
What are the 3 possible causes of poor oxygenation?
Poor ventilation
V/Q mismatch (ventilation/perfusion defects)
Shunting (alveolar collapse, PPHN, heart defects)
What is the adequate PaO2 range for the following patients?
Newborn:
Infant:
Child:
Newborn: 50-70
Infant: 85-100
Child: 80-100
On the exam, what is the first drug to always give if there is a problem?
Oxygen
Metabolic alkalosis is almost always a result of low ___,
and is best treated by giving ___.
Potassium. (Hypokalemia)
Treat by giving KCl (potassium chloride).
How many seconds of apnea is considered abnormal for
an infant?
a child?
> 20 seconds for infants
>10 seconds for a child
An AHI (apnea-hypopnea index) of what range is considered moderate?
16-30
Before discharging a baby with an apnea monitor, the parents should know ___.
CPR.
The low heart rate alarm on an apnea monitor should be set between ___.
60-80
Pulmonary Artery Pressure (PAP) is ___
Mean PAP is ___
Pulmonary Artery Pressure (PAP) is 25/8
Mean PAP is 14
If the exam says “wedge” pressure is rising, the problem is in the ___ heart.
Left
If the PAP is rising, the problem is in the ___.
Similarly, if there is a problem with the ___, think PAP.
Lungs
Lungs
If the exam says “left” anything is rising (mitral/bicuspid/left atrial/etc), think ___.
Wedge
Mean systemic arterial pressure is ___
In the 90’s
Normal CVP (central venous pressure) is ___
2-6 mmHg or 4-12 cmH2O
If you are worried about fluids, you should look at this pressure…
CVP. (very sensitive to fluid changes)
If the CVP is rising one of 2 problems exist…
- All values rise, which indicates ___
- Only CVP rises, which indicates ___
Fluid overload (all values rise) Right heart failure (only CVP rises)
Normal CO (cardiac output) is ___.
4-8 L/min
Venous saturation and ___ are directly proportional. If one increases/decreases, the other will follow.
Cardiac output.
