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ABGs

Section F

PAO2: Alveolar Air Equation (alveolar PO2) PAO2 = (PB - PH2O)FiO2 - PaCO2/R
Calculate the alveolar PO2 for a patient on 60% O2 with a PaO2 of 55 and the barometric pressure is 760 torr. (760-47)0.60 - 55/0.8 = 359.05
A-a gradient interpretation 25-65: normal, 66-300: V/Q mismatch, >300: Shunting
Calculate the A-aDO2 for a patient on 60% O2 with a PaCO2 of 55, PaO2 of 72 and barometric pressure of 760 torr. PAO2 = (760 - 47)0.60-55/0.8, A-aDO2 = 359 - 72 = 278, V/Q mismatch
CaO2: arterial oxygen content CaO2 = (Hb x 1.34 x SaO2) + (PaO2 x 0.003), norm: 17-20 vol%
Calculate the CaO2 for a patient whose PaO2 is 85, SaO2 is 96%, and Hb is 14. (14 x 1.34 x 0.96) + (85 x 0.003) = 18.3 vol%
CvO2: mixed venous oxygen content CvO2 = (Hb x 1.34 x SvO2) + (PvO2 x 0.003) norm:12-16 vol%
Calculate the CvO2 for a patient whose PvO2 is 40, SvO2 is 70% and Hb is 14. (14 x 1.34 0.70) + (40 x 0.003) = 13.3 vol %
what would a decreasing PvO2 indicate? decreased cardiac output
C(a-v)O2: arterial-venous oxygen content difference C(a-v)O2 = CaO2 - CvO2 Norm: 4-5 vol%
C(a-v)O2: ABG--pH 7.39, PaCO2 40, PaO2 88, SaO2 96%, Hb 15; VBG--pH 7.36, PvCO2 45, PO2 40, SvO2 70%, Hb 15 CaO2 = (15 x 1.34 x 0.96) + (88 x 0.003) = 19.56, CvO2 = (15 x 1.34 x 0.70) + (40 x 0.003) = 14.19 C(a-v)02 = 19.56 - 14.19 = 5.37 vol%
what would an increasing C(a-v)O2 indicate? CvO2 is decreasing and indicates decreasing cardiac output
QT: cardiac output VO2 / C(a-v)O2 (10) norm: 4-8 L/min
what would the cardiac output be for a patient with an oxygen consumption of 250 mL/min and C(a-v)O2 of 6 vol%? QT = 250 / 6(10) = 4.2 L/min
VO2: oxygen consumption VO2 = QT x C(a-v)O2 x 10
How can arterial oxygen saturation (SaO2) be estimated? SaO2 can be estimated by adding 30 to the PaO2 value.
If the analyzer temperature is lower than the body temperature (patient has a fever), how will the results measure? lower PaCO2 and PaO2, higher pH
If the analyzer temperature is higher than body temperature (hypothermia), how will the results measure? higher PaCO2 and PaO2, lower pH
VD/Vt: deadspace to tidal volume ratio PaCO2 - PECO2 / PaCO2 x 100
VD: deadspace VD/Vt x Vt = VD
Calculate the VD/Vt ratio for a patient whose PaO2 is 50, the pH is 7.35 and PECO2 is 25. 50-25 / 50 x 100 = 50%
what does the servinghaus electrode measure? PCO2
what does the clark electrode measure? PO2
what does the sanz electrode measure? pH
what ABG values are calculated? SaO2, HCO3
How is the pH calibrated in a blood gas analyzer? a low pH solution is injected to see if the accurate value is read. if not, its adjusted using the balance control
formula for calibrating gas for the PCO2 (BP - 47) x % or calibration gas x 7
calculate the low calibrating gas for the PCO2 using 5%, barometric pressure 760. (760 - 47) x 0.05 = 35 or 5 x 7 = 35
what are the two commercially prepared quality controls? blood-based and aqueous/fluorocarbon based control
what are the three levels of quality controls commonly used? acidotic, normal and alkalotic
how often is each quality control level ran? at least one time per day
ABG graph shows that all the values vary about the mean in a regular manner in control
ABG graph shows 1 point of 15 falling outside the + or -2 standard deviation random error
ABG graph shows: the plotted points all fall within the + or - 2 SD range, but the mean value shifts from where it was at the onset of data shift
ABG graph shows: a steadily increasing trend that is moving outside the + or -2 SD range out-of-control
list the three arteries in order they should be chosen for an ABG sample radial, brachial, femoral
What value from a heel stick capillary sample will not correlate well with an actual ABG? PO2
5 hazards that may occur while drawing an ABG hematoma, clotting, vessel spasm, tissue trauma, bleeding
normal ABG values PCO2: 35-45, PO2: 80-100, pH: 7.35-7.45, SO2: 95-100%, HCO3: 22-26, BE: -2 - +2, HB: 12-16, CaO2/CvO2: 17-20
interpretation and response to PaCO2 above 45 patients not ventilating, ventilate or increase ventilation
interpretation and response to PaCO2 below 35 patient is over-ventilating, add deadspace (PO2 is acceptable)
interpretation and response to PaO2 below 80 and FiO2 .21-.59 hypoxemia due to: poor ventilation(high PCO2) or V/Q mismatch(normal PCO2), increase ventilation, increase FiO2
interpretation and response to PaO2 below 80 and FiO2 0.60 hypoxemia due to shunting, start CPAP if patients is breathing spontaneously or PEEP if patient is on a vent
interpretation and response to PaO2 above 100 and FiO2 .22-1.0 hyperoxemia due to over oxygenation, decrease FiO2 PEEP or CPAP
response to abnormal PCO2 with normal pH don't change ventilation (chronic patient, COPD)
interpretation of pH below 7.35 Acidosis- non-compensated (due to increase CO2 or low HCO3)
interpretation of pH above 7.45 Alkalosis- uncompensated (due to increased HCO3 or low CO2)
partial compensation abnormal pH, CO2 and HCO3 in same direction
pH: 7.30, PCO2: 62, PO2: 70, FiO2: .21 Uncompensated Respiratory Acidosis, patient should be ventilated
pH: 7.38, PCO2: 42, PO2, 60, FiO2: 0.21 Normal ABG with V/Q mismatch, increase FiO2
pH: 7.48, PCO2: 31, PO2: 46, FiO2: 0.60, Hb: 14 Uncompensated Respiratory alkalosis, shunting, CPAP
pH: 7.51, PCO2: 48, PO2: 76, FiO2: 0.21, HCO3: 30, Hb: 13 partially compensated metabolic alkalosis, administer KCI
pH: 7.31, PCO2: 32, PO2: 128, HCO3: 17, FiO2: 0.35, Hb: 6 partially compensated metabolic acidosis, administer bicarb and blood
pH: 7.43, PCO2: 42, PO2: 250, HCO3: 23, FiO2: 0.21, Hb: 14, PB: 760 Too much oxygen, recheck FiO2 and redo ABG
pH: 7.35, PCO2: 54, PO2: 68, FiO2: 0.21, Hb: 8, HCO3: 37 Compensated respiratory acidosis, low FiO2 and administer blood
pH: 7.40, PCO2: 40, PO2: 110, FiO2: 0.21, Hb: 14, HCO3: 24 CO poisoning, 100% O2 and hyperbaric chamber
pH: 7.40 PCO2: 40 PO2: 98 FiO2: 0.21 Hb: 14 HCO3: 24 Normal
pH: 7.30 PCO2: 80 PO2: 88 FiO2: .40 Hb: 12 HCO3: 36 Partially Compensated Respiratory Acidosis, to much O2 for COPD patient, decrease FiO2
pH: 7.31 PCO2: 30 PO2: 82 FiO2: 0.21 Hb: 12 HCO3: 16 Partially compensated metabolic acidosis, administer bicarb
pH: 7.22 PCO2: 51 PO2: 64 FiO2: 0.21 Hb: 12 HCO3: 18 Mixed acidosis
Created by: grumpeme on 2008-07-28