CALCULATIONS
PIO2 = PB – 47 x FIO2
667
47
620
x .21
130.2
-
PAO2 = PIO2 – PaCO2 x 1.2*
* If FIO2< 60% otherwise use 1.0
-
a/A PO2 =
PaO2
PAO2
a/A PO2 =
130.2 mmHg
48.0 mmHg (40.0 x 1.2)
82.2 mmHg
(PAO2)
75 mmHg normal PaO2 (Amarillo)
82.2 mmHg (Amarillo)
A-a PO2 = PAO2 - PaO2
-
VD physiologic
mmHg (PB)
mmHg (water vapor)
mmHg
FIO2
mmHg (PIO2)
82.2
75
7.2
mmHg
mmHg
mmHg
a/A PO2 = 0.91
(PAO2)
(PaO2)
(A-a PO2 gradient)
VDphysiologic =
PaCO2 - PECO2
x VE
PaCO2
VD
PaCO2 - PECO2
=
VT
PaCO2
VDphysiologic =
40 - 27
x 500
40
VD
40 - 27
=
VT
40
VD
= 0.325
VT
VDphysiologic = 0.3.25 x 500
VDphysiologic = 162.5 ml
VD anatomic
VDanatomic =
FACO2 - FECO2
x VE
FACO2
VDanatomic =
6.45% - 4.35%
x 500
6.45%
VDanatomic = .325 x 500
VDanatomic = 162.5 ml
R respiratory exchange ratio
R=

VCO
2
 2
VO
R=
200 ml
250 ml
R = 0.8
VE (or VT) x f = V (V E)
500 ml x 14 bpm = 7000 ml or 7 L
VA x f = V A
350 ml x 14 bpm = 4900 ml or 4.9 L
VD x f = V D
150 ml x 14 bpm = 2100 ml or 2.1 L
V = V D + V A
7 L = 2.1 L + 4.9 L
DLCO x 1.23 = DLO2
36 ml/min/mmHg (CO) x 1.23 = 44.28 ml/min/mmHg (O2)