Diagnostic Testing - Core Concepts

Question 1

What is the quick alveolar air equation?

Answer 1

(FiO2 x 7) - (PaCO2 + 10)

In a pinch, FiO2 x 7 should be close enough

Question 2

How do you calculate the A-a gradient?

Answer 2

PAO2 - PaO2

Find PAO2 with the alveolar air equation, then subtract your arterial (ABG) PaO2.

Question 3

What is normal a/A ratio?

a
___
A

A ratio lower than ___ indicates surfactant therapy.

Answer 3

0.8 - 0.9

Lower than 0.2 is an indication for surfactant usage. A higher number indicates improvement.

Question 4

A normal shunt is ___%, and increases by ___% for every increase of ___ in the A-a gradient.

Answer 4

Normal is 5%. Shunt increases by 5% for every increase of 100 in the A-a gradient.

Question 5

An A-a gradient of 200 would correlate with a shunt of what %?

Answer 5

15%. Start with the normal of 5%, and add 5% for every 100 torr of A-a gradient.

Question 6

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.

Answer 6

> 25 indicates nitric oxide therapy.

> 40 indicates ECMO therapy.

Question 7

What is a normal PF ratio?

Answer 7

380 or greater.

Question 8

PF ratio of:
201-300 indicates ___ ARDS
< 200 indicates ___ ARDS
< 100 ___ ARDS

Answer 8

Mild
Moderate
Severe

Question 9

What is a normal SaO2/FiO2 ratio? is it less invasive that a P/F ratio?

Answer 9

400

Yes

Question 10

What is a normal Vd/Vt ratio? (deadspace to tidal volume ratio)

Answer 10

20% - 40% (up to 60% in mech vent patients)

Question 11

What is the deadspace to tidal volume equation? (Vd/Vt)

Answer 11

PaCO2- PetCO2
_____________ x 100
PetCO2

Question 12

The most common pathology related to a high deadspace to tidal volume ratio is?

Answer 12

Pulmonary embolism (PE)

Question 13

A 3L calibrating syringe has an acceptable accuracy range of what %, and what volume?

Answer 13

3.5%, which is about 100 ml. If the syringe is considered accurate, it’s volume will be between 2.9L - 3.1L

Question 14

The vital capacity measures volume and identifies (restrictive/obstructive) disorders?

Answer 14

Vital capacity identifies restrictive disorders.

Question 15

The FEV1 measures flow and identifies (obstructive/restrictive) disorders?

Answer 15

FEV1 identifies obstructive disorders.

Question 16

is 80-100% of predicted a normal result on a PFT?

Answer 16

Yes.

Question 17

Are CF, bronchitis, asthma, and bronchiectasis obstructive or restrictive?

Answer 17

Obstructive. EVERYTHING else is restrictive.

Question 18

MIP (maximum inspiratory pressure) of less than ___ indicates inspiratory muscle weakness

Answer 18

<20

Question 19

MEP (maximum expiratory pressure) of less than ___ indicates poor ability to clear secretions.

Answer 19

<40

Question 20

Normal SpO2 for newborns?

Normal SpO2 for children?

Answer 20

Newborns: 90-95
Children: 93-97

Question 21

What is the ideal temperature range for transcutaneous monitoring?

Answer 21

41C - 44C

Question 22

A transcutaneous monitoring electrode should be moved to a new site in how many hours?

If erythema (redness/blistering) occurs, what should you do?

Answer 22

Move electrode every 4-12 hours.

Move the electrode, and change sites more frequently.

Question 23

In what order do you assess blood gas values on the exam?

Answer 23

VOCP!!!

CO2 first
PaO2, FiO2
pH

Question 24

Assess the following blood gas results in order of the NBRC guidelines:

pH
PaCO2
PaO2/FiO2

Answer 24

VOCP!!!

PaCO2 first (assess ventilation)
PaO2/FiO2 (assess oxygenation)
pH (if both are acceptable)

Question 25

Is the patient ventilating, according to the NBRC guidelines? If PaCO2 is normal? if PaCO2 is increased? if PaCO2 is decreased?

Answer 25

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.

Question 26

What are the 3 possible causes of poor oxygenation?

Answer 26

Poor ventilation V/Q mismatch (ventilation/perfusion defects) Shunting (alveolar collapse, PPHN, heart defects)

Question 27

What is the adequate PaO2 range for the following patients? Newborn: Infant: Child:

Answer 27

Newborn: 50-70 Infant: 85-100 Child: 80-100

Question 28

On the exam, what is the first drug to always give if there is a problem?

Answer 28

Oxygen

Question 29

Metabolic alkalosis is almost always a result of low ___, | and is best treated by giving ___.

Answer 29

Potassium. (Hypokalemia) | Treat by giving KCl (potassium chloride).

Question 30

How many seconds of apnea is considered abnormal for an infant? a child?

Answer 30

>20 seconds for infants | >10 seconds for a child

Question 31

An AHI (apnea-hypopnea index) of what range is considered moderate?

Answer 31

16-30

Question 32

Before discharging a baby with an apnea monitor, the parents should know ___.

Answer 32

CPR.

Question 33

The low heart rate alarm on an apnea monitor should be set between ___.

Answer 33

60-80

Question 34

Pulmonary Artery Pressure (PAP) is ___ | Mean PAP is ___

Answer 34

Pulmonary Artery Pressure (PAP) is 25/8 | Mean PAP is 14

Question 35

If the exam says "wedge" pressure is rising, the problem is in the ___ heart.

Answer 35

Left

Question 36

If the PAP is rising, the problem is in the ___. | Similarly, if there is a problem with the ___, think PAP.

Answer 36

Lungs | Lungs

Question 37

If the exam says "left" anything is rising (mitral/bicuspid/left atrial/etc), think ___.

Answer 37

Wedge

Question 38

Mean systemic arterial pressure is ___

Answer 38

In the 90's

Question 39

Normal CVP (central venous pressure) is ___

Answer 39

2-6 mmHg or 4-12 cmH2O

Question 40

If you are worried about fluids, you should look at this pressure...

Answer 40

CVP. (very sensitive to fluid changes)

Question 41

If the CVP is rising one of 2 problems exist... 1. All values rise, which indicates ___ 2. Only CVP rises, which indicates ___

Answer 41

``` Fluid overload (all values rise) Right heart failure (only CVP rises) ```

Question 42

Normal CO (cardiac output) is ___.

Answer 42

4-8 L/min

Question 43

Venous saturation and ___ are directly proportional. If one increases/decreases, the other will follow.

Answer 43

Cardiac output.