Diagnostic Testing Flashcards
Full formula for PAO2
(PB-PH2O)FiO2 - PaCO2/0.8
PAO2 shortcut
(FiO2x7) - (PaCO2+10)
Clinical shunt shortcut
5% baseline, add 5% per 100 torr of A-a gradient
Four pulmonary disorders that could increase shunt
Atelectasis, pneumonia, pulmonary edema, ARDS
Oxygenation index formula
(PawxFiO2 / PaO2) x 100
Acceptable range of accuracy for 3L syringe
+/- 3.5%, 2.895-3.105
What device is used to calibrate an instrument which measures flow
Rotameter
At what age can a child perform basic spirometry?
5 and up
What is the single most important spirometry test and how long must the procedure be sustained for a while who is less than ten? Older than 10?
FVC/FEV1
3 seconds
6 seconds
What is the best test to evaluate volume? What type of disorder does it evaluate?
Vital capacity, restrictive
What is the best test to evaluate flow rates? What type of disorder does it evaluate?
FEV1, obstructive
Why is a pre and post bronchodilator study done? How much change in the FEV1 is considered significant?
Evaluate reversibility, 12%
3 obstructive and 2 restrictive diseases found in children
Obstructive: asthma, CF, bronchitis
Restrictive: pulmonary fibrosis, skeletal deformities
When determining a child’s personal best peak flow measurement, when should they record their peak flow?
Record peak flow BID, for 2-3 weeks, during a period when asthma is under control. Then pick single highest measurement.
How many times should the peak flow maneuver be performed in one sitting?
3x
What value should be recorded after a child performs peak flow maneuvers
Highest of the three numbers
What negates a positive bronchial provocation test?
20% decrease in FEV1
What value for MIP indicates respiratory muscle weakness?
<20
What value for MEP indicates inability to clear airway secretions?
<40
What two parameters are measured by pulse ox?
Spo2 and HR
Normal range SpO2 for newborns?
90-95%
Normal range SpO2 for children?
93-97%
What factors effect accuracy of pulse ox?
Perfusion, nail polish, hypotension, erythema
Primary co-oximeter indication
Detect COHb
Normal range for COHb
1-3%
What value of COHb indicates carbon monoxide poisoning?
> 20%
What parameter is measured by cerebral oximetry?
Tissue oxygenation
Where are the sensors placed to monitor cerebral tissue oxygenation?
Forehead
Where in the patient circuit should capnograpy sensor be placed?
Proximal to ETT
What is the effect of moisture or secretions on ETCO2 sensor?
False low readings
What is indicated by an increase in the capnograph reading?
Decrease in ventilation
What is indicated by a decrease in capnograph reading?
Increase in ventilation, and a decrease in perfusion (dead space, PE, etc)
What is the significance of continuous low readings following intubation?
Tube in esophagus
What do transcutaneous monitors measure?
PO2 and PCO2
What two advantages do transcutaneous monitors have over ABGs?
Non-invasive, continuous
Why is the skin around heated? And to what temp?
Improves capillary blood flow (perfusion), 41-44C
What conditions would diminish the accuracy of the transcutaneous monitor?
Skin thickness, anemia, shock, burns, vascular disease, cardiac defects
Where is the transcutaneous electrode placed?
Flat areas with good perfusion (chest, abdomen, thighs, back), no bony areas, large vessels, or extremities
How often should the transcutaneous electrode site be changed?
4-12 hours, otherwise erythema develops
Describe how a transcutaneous monitor is calibrated
With room air and a zeroing solution
Describe how a transcutaneous monitor can be used to detect the presence of a R to L shunt
Pre- and post ductal, reads at least 15 higher on pre
POC test time
90 seconds
3 methods to obtain ABG
Umbilical arterial line
Arterialized capillary sample
Peripheral artery puncture
When placing an umbilical artery Lin, what size catheter should be used for a newborn <1500g? >1500g?
3.5Fr, 5Fr
Briefly describe how to draw a sample from an umbilical artery line
Insert catheter into the umbilical artery at the cut end of the umbilical cord
Why should the heel not be squeezed when obtaining a capillary blood sample?
It will alter results and damage heel
What value from the capillary sample will not correlate well with actual arterial blood gas values?
PO2
What needle size should be used for a peripheral artery puncture?
25 gauge
For what period of time should the puncture site be compressed following the procedure
5 minutes
What is the important concern when performing peripheral artery puncture?
Stimulation of child effecting result
What sample size should be obtained from an umbilical or peripheral artery?
1.25-2mL
Newborn ABG ranges
PH: 7.25-7.35
CO2: 45-55
PaO2: 50-70
Infant ABG ranges
PH: 7.34-7.46
CO2: 30-45
PaO2: 85-100
What is different about a premature infants ABG?
Higher CO2, lower pH (50-55, 7.33)
What two values from an ABG will assess the oxygenation status of a pt?
PaO2 and FiO2
What three possible problems could cause hypoxemia?
Poor ventilation
V/Q mismatch
Shunting
V/Q mismatch responds to what tx?
Oxygen
Pneuomogram
12-24 hr continuous recording of respiratory movement, HR, SpO2, and nasal air flow
Polysomnogram
Monitors sleep stages via EEG, respiration, ECG rhythm, muscle activity, gas exchange, and snoring data
When would periods of apnea be considered abnormal?
Longer than 20 seconds for infants, longer than 10 seconds in children
Three types of apnea
Central, obstructive, combined
Which type of apnea is common in older children?
Obstructive
Describe how to diagnose obstructive sleep apnea
Nasal air flow stops but chest motion continues or increases
What is the correct interpretation of an apnea-hypopnea index of 26?
Moderate (16-30)
What is the correct interpretation of a respiratory disturbance index of 16 for a 15 y/o?
Moderate (15-30)
RBI of 8 in <12 y/o?
Moderate (5-10)
List five ways apnea can be treated
CPAP/BiPAP
Weight loss
Trach
Tonsillectomy/adenoidectomy
Drugs: caffeine, resp stimulant, theophylline
What factors would indicate that an infant is at risk for SIDS?
SIDS sibling
One or more apparent life threatening episodes (ALTE)
Preterm infant with significant apnea episodes
Snoring in infants
What are indications for apnea monitoring?
Infants who may be at risk for significant apnea (>20sec) or bradycardia (<80bpm)
Under what condition is it safe to d/c apnea monitoring?
2 mos free of events
No monitor alarms on apnea settings >20 seconds and bradycardia <60
After asymptomatic period when infant received DPT immunization and experienced nasopharyngitis without recurrence of symptoms
Follow up pneumogram is Normal
Send baby home with apnea monitor after parents learn
CPR
What two life functions are monitored with hemodynamics?
Circulation and perfusion
At what age can a PAC be placed in a child?
8-9 y/o
What is the primary cause of bradycardia in an infant?
Hypoxemia
What is the primary cause of tachycardia in children?
Hypoxemia
How can the quality of the cardiac monitor tracing be improved?
Clean skin with alcohol prior to placement
How is blood pressure best measured?
Indwelling arterial catheter and pressure transducer
What factors will increase blood pressure?
Stress, hypoxia, sepsis
What factors will decrease blood pressure?
Shock, severe stress, severe sepsis
Normal pressure in left ventricle
120/0
Normal pressure in systemic arteries
90
Normal pressure in systemic veins
10
Normal pressure in right atrium
2-6
Normal pressure in right ventricle
25/0
Normal pressure in pulmonary arteries
25/8
Mean pulmonary artery pressure
14
Normal pressure in pulmonary veins
8-10
Normal pressure in left atrium
2-6
What does the CVP monitor and evaluate?
Fluid levels and function of right heart
Where is the tip of the CVP catheter placed?
Superior vena cava
Normal CVP value
2-6
What does PAP refer to and what does it measure?
Pulmonary artery pressure, lung fuction
Normal PAP value
25/8, mean 14
What type of blood samples are obtained via the PAC?
Mixed venous blood samples (balloon must be deflated prior to sampling)
Normal pulmonary capillary wedge pressure? (PCWP)
4-12
How can PCWP be estimated if the catheter cannot be wedged?
PA diastolic pressure
How does the PCWP change in a pt with cardiogenic pulmonary edema?
Elevated
How does PCWP change in a pt with non-cardiogenic pulmonary edema? (ARDS)
Normal
You see wedge you think
Left
Identify location of the tip of the catheter at each section
Right atrium
Right ventricle
Pulmonary artery
Pulmonary capillary wedge
What are the four ways to determine cardiac output
Fick equation
QT = HR x SV
Thermal dilution
CaO2 - CvO2
Normal range for cardiac output (Qt)
4-8
Normal value for SvO2
75%
significance of a decrease in SvO2?
Decreased CO, decreased O2 delivery, increased O2 demand, impaired tissue oxygenation, shock
Formula for calculating cardiac index
Cardiac output (Qt) divided by body surface area
Normal range or cardiac index
2.5-5.0
Right heart failure, cor pulmonale, tricuspid valve stenosis hemodynamics (CVP, PAP, PCWP, CO)
CVP increased
PAP N/decreased
PCWP N/decreased
CO N
Lung disorders, PE, Pulmonary Han, air embolism hemodynamics (CVP, PAP, PCWP, CO)
CVP increased
PAP increased
PCWP N/decreased
CO N
Left heart failure, mitral valve stenosis, CHF, high PEEP effects hemodynamics (CVP, PAP, PCWP, CO)
CVP N
PAP increased
PCWP increased
CO decreased
Hypervolemia hemodynamics (CVP, PAP, PCWP, CO)
All increased
Hypovolemia hemodynamics (CVP, PAP, PCWP, CO)
All decreased
Systemic vascular resistance definition, NV, formula
Pressure gradient across the systemic circulation divided by cardiac output
<20 or 1600 dynes
(MAP-CVP) / QT
SVR is increased in
Systemic hypertension and/or vasoconstriction
SVR is decreased in
Increased CO/CI
PVR definition, NV, formula
Pressure gradient across pulmonary circulation divided by CO
<2.5 or 200 dynes
(MPAP - PWP) / Qt
PVR is increased with
Hypoxia, PHtn
How to convert mmHg/L/Min to dynes
X 80
Mixed venous oxygen content (CvO2) equation and NV
CvO2 = (Hb x 1.34 x SvO2) + (PvO2 x 0.003)
12-16vol%C
CvO2 decreases when
CO decreases
