Alveolar Air Equation: Calculates partial pressure of O2 in Alveoli
PAO2 = (([blank_start]Pb[blank_end] - 47)[blank_start]FiO2[blank_end]) - (PaCO2/[blank_start].8[blank_end])
Shortcut: PAO2 = (7 x FiO2) - (PaCO2 +10)
Answer
Pb
.8
FiO2
Question 2
Question
A-a Gradient: Measures difference between aveolar and arterial O2
A-aDO2 = PAO2 - PaO2
25-65 on 100% O2 is [blank_start]Normal[blank_end]
66 - 300 is [blank_start]V/Q[blank_end] mismatch
>300 = [blank_start]Shunting[blank_end]
Answer
Shunting
V/Q
Normal
Question 3
Question
Arterial O2 Content (CaO2) Best measurement of O2 delivered to tissues
CaO2 = ([blank_start]Hb[blank_end] x [blank_start]1.34[blank_end] x SaO2) + (PaO2 x [blank_start].003[blank_end])
O2 in red blood cells plus O2 in plasma
Normal value is [blank_start]17[blank_end]-[blank_start]20[blank_end] vol% (mL/dL)
Answer
Hb
1.34
.003
17
20
Question 4
Question
Mixed Venous O2 Content (CvO2) Total O2 in venous blood
CvO2 = (Hb x [blank_start]1.34[blank_end] x [blank_start]SvO2[blank_end]) + [blank_start]PvO2[blank_end] x .003)
Normal [blank_start]12[blank_end] - [blank_start]16[blank_end] vol%
CvO2 will [blank_start]decrease[blank_end] when cardiac output decreases
SvO2 will decrease also.
Answer
1.34
SvO2
PvO2
12
16
decrease
Question 5
Question
Arterial - Venous O2 Content Difference Ca-vO2 - Provides estimate of Tissue O2 consumption
Ca-vO2 = CaO2 - CvO2
Normal is [blank_start]4[blank_end] - [blank_start]5[blank_end] vol %
Used in Fick equation to calculate [blank_start]Cardiac[blank_end] Output
Answer
4
5
Cardiac
Question 6
Question
Cardiac Output Qt
Modified [blank_start]Fick[blank_end]
Used to calculate Cardiac output when O2 consumption and O2 content differences are known
Qt = ([blank_start]VO2[blank_end] / (Ca-vO2([blank_start]10[blank_end]))
Normal value is 4-8 L/min
VO2 = Qt x Ca-vO2 x 10
Answer
10
VO2
Fick
Question 7
Question
Shunt Equation
Qs / Qt
Portion of cardiac output that is shunted and does not participate in gas exchange
Qs/Qt = ((A-aDO2) x .003) / (A-aDO2) x .003) + Ca-vO2
Normal is [blank_start]3[blank_end]-[blank_start]5[blank_end] %
Can be estimated: Assuming 5% shunt increase for each 100 torr of A-aDO2
Answer
3
5
Question 8
Question
SaO2 Arterial O2 Saturation
% of Hb that is bound by O2 calculated by ABG analyzer
Measured by hemoximeter or co-ox
Large differences in calculated and measured could be because of increased carboxyhemoglobin levels
PaO2 is estimated by subtracting [blank_start]30[blank_end] from [blank_start]PaO2[blank_end]
Answer
PaO2
30
Question 9
Question
HB / Hct
HB is normally [blank_start]12[blank_end] - [blank_start]16[blank_end] g/dl
HCT is usually [blank_start]3[blank_end] times HB in percent
Answer
3
12
16
Question 10
Question
Deadspace to Vt Ratio
VD/Vt
% of gas that doesn't participate in gas exchange
Normal is [blank_start]20[blank_end]-[blank_start]40[blank_end]%
((PaCO2 - PeCo2) / [blank_start]PaCO2[blank_end]) x 100
Increased VD/VT indicates deadspace disease like a [blank_start]PE[blank_end]
Answer
PE
20
40
PaCO2
Question 11
Question
Normal Values
PCO2
Arterial [blank_start]40[blank_end]
Range [blank_start]35[blank_end]-[blank_start]45[blank_end]
venous [blank_start]46[blank_end]
PO2
Arterial [blank_start]97[blank_end]
Range [blank_start]80[blank_end] - [blank_start]100[blank_end]
Venous [blank_start]40[blank_end]
pH
Arterial [blank_start]7.4[blank_end]
Range [blank_start]7.35[blank_end] - [blank_start]7.45[blank_end]
Venous [blank_start]7.35[blank_end]
SO2
Arterial [blank_start]98[blank_end]%
Range [blank_start]95[blank_end] - [blank_start]100[blank_end]%
Venous [blank_start]70[blank_end] - [blank_start]75[blank_end]%
HCO3-
Arterial [blank_start]24[blank_end]
Range [blank_start]22[blank_end]-[blank_start]26[blank_end]
Venous [blank_start]24[blank_end]
Normal BE [blank_start]0[blank_end] +- [blank_start]2[blank_end]
Hb
Arteral/Venous [blank_start]15[blank_end]
Range [blank_start]12[blank_end] - [blank_start]16[blank_end]
CaO2
Arterial [blank_start]20[blank_end] vol%
Range [blank_start]17[blank_end]-[blank_start]20[blank_end] vol%
CvO2
Venous [blank_start]15[blank_end] vol%
Range [blank_start]12[blank_end] - [blank_start]16[blank_end] vol %