Pulmonary diagnostic testing Flashcards
Three primary sites for obataining arterial blood gas
Radial
Brachial
Femoral
The Modified Allen’s test
used to assess the collateral circulation
Hand should pink up within 1-2 sec
ABG Hazards and Problems
air bubbles
effects on pH, PaCo2, PaO2
- PaCO2 decreases toward 0
- PaO2 increases or decreases toward 150 torr
- pH increases
ABG Hazards and Problems
Improper cooling
effects on pH, PaCO2, PaO2
- PaCO2 increases
- PaO2 decreases
- pH decreases
Capillary samples are used to obtain blood gas samples in
heel sticks
infants
capillary sample
PO2 values do/do not correlate well with ___
- do not
- arterial blood
especially true when the arterial po2 is above 60torr
Capillary gases should not be used to monitor
oxygen therapy
Only pH and PCO2 correlate with arterial
Name harzards and problems of an arterial sample
- Disruption of blood flow
- clotting
- Bleeding
- Vessel spasm
- Tissue trauma
- Air bubbles
- improper cooling
- too much liquid heparin
Capillary blood samples correlate with arterial blood samples
pH and PCO2
not PO2
Umbilical arterial catheter tip placement
at L-3 which is above the bifurcation of the aorta but below the renal arteries
Unbilical artery PO2 may be used to regulate
FiO2
Advantages of umbilical artery catheter (UAC)
- allows continuous monitoring of blood pressure
- Arterial samples of ABG and other lab analysis
- Blood transfusion
Arterial line: If transducer is above the catheter, displayed pressure is
lower than actual
Arterial line: if transducre is below catheter, displayed pressure is
higher than actual
Blood Gas analyzers
Severinghaus electrode
PCO2 -
partial pressue of carbon dioxide in sample
Blood Gas analyzers
Clark electrode
PO2
Patrial pressure of oxygen in sample
Blood Gas analyzers
Sanz electrode
Acid base status
Blood Gas analyzers
Quality Control : when the blood gas machine is functioning correctly, the mesured control valies ..
will be close to the mean and withing +/- 2 standar deviations
Blood Gas analyzers
Westgard rules
a comon set of rules developed to differentiate between random errors and true out of control situations
* Called multiple-rule method
Blood Gas analyzers
Out of control situations
- one control observation exceeds the mean +- 3 SD
- Two consecutive control observations exceed the mean +2 SD or the mean -2SD
- The difference between consecutive control runs exceed 4SD
Point of care testing
anytype of lab testing done at the bedside
List laboratory test that can be perfored by point of care testing
- blood glucose
- arterial blood gas
- hematrocit
- serum electrolytes
Intravenous infusionis used to administer ____, ____, and ____ continuously to the pt
- medications
- blood products
- supplemental nutrition/ fluids
Venipuncture is performed to provide ____
vascular access for continuous infusion or for blood sampling for laboratory analysis
Alveolar Air equation
Definition
Calculates the partial pressure of oxygen (PO2) in the alveoli
PAO2
PAO2
equation
= (PB-Ph2o) FiO2 - (Paco2/0.8)
(747-47) Fio2 - Paco2/ 0.8
Fio2 is NOT in percent
A-a gradient
Definition
Measures the difference between alveolar and arterial PO2
A-aDO2
equation
PAO2 -PaO2
A-aDO2 normal value
25-65 torr on 100%
A-aDO2
66-300 torr
interpretation
V/Q mismatch
A-aDO2 : >300
interpretation
Shunting
A-a gradient of 190 torr
what would be a treatment ?
give O2 therapy
A-a gradient of 350 torr
what would you recommend
give positive pressure therapy
P/F ratio
definition
ratio of the partial pressure of arterial O2 to the inspired fractional concentration of oxygen
Used in determination of ALI or ARDS
P/F ratio
Measures the efficiency of oxygen transfer across the lung
P/F ratio
P/F ratio : normal value
> 380 torr
P/F ration : < 300 signifies
ALI
P/F ration : < 200 signifies
ARDS
Arterial oxygen content
definition
best measurement of oxygen delivered to the tissues , or the bes index of oxygen transport
best measurement of oxygen delivered to the tissues , or the best index of oxygen transport
Arterial oxygen content
(CaO2)
CaO2
equation
(Hb x 1.34 x SaO2) + (PaO2 x 0.003)
shortcut: Hb x 1.34 x SaO2 or Hb x 1.34
Normal value for CaO2
arterial oxygen content
17-20 vol % (mL/dL)
Mixed venous oxygen content
definition
total amount of oxygen carried in the mixed venous blood
equation like CaO2 but with venous
CvO2 normal value
12-16 vol %
arterial- venous oxygen content difference
definition
measures the oxygen consumption of the tissues
C(a-v)O2
equation
CaO2 - CvO2
C(a-v)O2 normal value
4-5 vol%
CvO2 values will __ when C.O __
What about SvO2?
- decrease
- decreases
- SvO2 values also decrease if C.O decreases
C.O decreases, CvO2 decreases
The percentage of the hemoglobin that is bounde by oxygen
Arterial Oxygen Saturation
SaO2
PaO2 value can be estimated by
subtracting 30 from the SaO2
measure the amount of ventilation support required to provide the level of oxygenation
Oxygen Index
Oxygen Index equation
(Paw- Fio2 / PaO2 ) x 100
Fio2 is a decimal not a percent
Normal OI
<10
An increase in the pt venous oxygen content would indicate that
C.O increased
Deadspace to tidal volume ratio
VD/VT
the percentage of the VT that does not participate in gas exchange
Ventilation without perfusion
oxygen index
Recomend __ for newborns with __
- ECMO for newborns withOI >40
Normal VD/VT ratio
deadspace
20-40%
(up to 60% with ventilator pt )
Desired minute volume equation
current Ve x current PaCO2 = desired Ve x desired PaCO2
PaO2 value
Below 80
interpretation
Hypoxemia
can be caused by
* Poor ventilation
* V/Q mismatch
Hypoxemia
can be caused by
PaO2 below 80
- Poor ventilation
- V/Q mismatch
Response for hypoxemia
- increase ventilation
- increase FiO2 up to 60%
- add PEEP
PaO2 bellow 80
with 60% + fio2
interpretation. What does the pt have?
Shunt, refractory hypoxemia, venous admixture
Shunt, refractory hypoxemia, venous admixture
RESPONCE
decrease Fio2, PEEP or CPAP
When pH is inside aceptable range
its called
Compensated or Chronic
When pH outside the acceptable range
its called
Non-compensated or Acute
abg sample
Higher PaO2 values (>140) would indicate
supplemental oxygen in use , bubble in sample or technical error
Lower PaO2 values may indicate
V/Q mismatch, diffusion defect, shunting or venous blood
Treatment for CO poisoning
100% oxygen and hyperberic oxygen therapy
comfirm Pulmonary embolus with
V/Q scan, CT scan, pulmonary angiography
Supect embolus in
pt with
- post op pt
- bedridden pt
- history of deep vein thrombosis
- women in advance stages of pregnancy
- Venous stasis
- obesity
- Trauma
- atrial fibrillation
Loss of metabolic acids, dehydration, electrolyte imbalance (due to vomiting)
Treatment
Administer potassium chloride (KCl) and oxygen
normal PaCO2 of a newborn
< 50 torr