Dr. R. Tandon
Sitaram Bhartia Institute, New Delhi
Pressures
RA
RV
PA
PAW
LA (PV)
LV
SA
: a = 2-6; V = 2-4 m = 3 (0-6)
:15-25 edp 0-5.
:15-25; diast. 6-10, m = 10-15.
: a = 6-12, V = 8-14, m 6-10 (12)
: a=6-12, V=8-14, m = 6-10 (12)
: 90-120 / 0-10 (12)
:90-120 / 60-75 (70-85).
Pressures
i)
RA a = RV edp
‘a’  edp = TS
ii)
PA diast. = LA m.
PA diast.  LA (m) =  PVR
iii) PAW ‘a’ = LA ‘a’ = LV edp.
iv) PAW ‘a’ (LA a)  edp = obstr.
(PV obstr, cortriat, MS, supra valv ring).
Oxymetry
Oxygen Capacity (vol. %)
Oxygen content (vol. %)
Oxygen saturation (%)
Vol % = ml O2 / 100 ml. Bl.
Oxygen Capacity
1 gm Hb can carry 1.36 ml O2.
If Hb=15 gm : Capacity=15 x 1.36 =20.4
If Hb=10 gm : Capacity=10 x 1.36 = 13.6
Hence Hb must be determined for the calculation of O2
capacity.
Oxygen Saturation (%)
% of oxygenated Hb.
Obtained directly using oxymeters.
Pulm. Ven. Sat. = 98% (100%).
Arterial O2 Sat. = PV sat = 98-100%.
Mixed ven. O2 Sat = 75-80% (PA).
A drop of 2% or  in arterial O2 sat. compared to PV
Sat. = RL shunt
Oxygen Content
O2 content = O2 cap x O2 sat./100.
Hb 15 gm : Cap 15 x 1.36 = 20.4.
SA Sat. 98%; MV Sat. = 80%, 60%.
SA Content = 20.4 x 98
100
=
19.99
MV content = 20.4 x 80
100
=
16.32
MV content = 20.4 x 60
100
=
12.24
Oxygen Content


PO2 – 100 – O2 content
(room air)
Hb
Bound
15
20.4
10
13.6
PO2 – 600
15
20.4
10
13.6
Dissolved
0.3 ml (1.5%)
0.3 ml (2.5%)
1.8 ml (9%)
1.8 ml (14%)
Cardiac Output




CO = Oxygen consumption (VO2)
(PV) SA O2 Cont.–MVO2 cont. x 10
Oxygen consumption can be measures but is
generally assumed depending on age, HR and BSA
from nomograms.
O2 content needed to calculate flows.
Cardiac Output
O2 content : (Hb 15)
SA (98%)
1)
MV (80%)
2)
MV (60%)
= 19.99
= 16.32
= 12.24
CD (1) = ____VO2______ = ___VO2___
19.99 - 16.32 x 10
3.67 x 10
CO (2) = ______VO2_____ = ___VO2___
19.99-12.24 x 10
7.75 x 10
Cardiac Output
i) CO = __VO2__
3.67x 10
ii) CO =
= __150___ = 4.08 l/m/M2
3.67 x 10
__VO2___ = __150___ = 1.93 l/m/M2
7.75 x 10
7.75 x 10
The lower the mixed venous O2 content (Or saturation) the
lower the cardiac output.
Cardiac Output
Qp) Pulm. Bl. flow
= __________VO2___________
PV O2 Cont.–PA O2 Cont. x 10
Qs)
= __________VO2___________
SA O2 cont.–MV O2 Cont. x 10
Syst. Bl. flow
In the absence of a left to right or right to left shunt Qp = Qs
L  R shunts
Bl. Samples taken from PA, RV, RA, SVC
ASD : SVC to RA
Sets 1-10%, 2-7%, 3-5%
VSD : RA to RV
Set 1-7%, 2-5%
PDA : RV to PA
1 set – 5%, 2-3%
L  R shunts
(Qs) Syst. Flow =
__________VO2___________
SA O2 cont.–MV O2 Cont. x 10
(Qp) Pulm. flow =
__________VO2___________
PVO2 Cont.–PA O2 Cont. x 10
QP – Qs = LR shunt.
Shunts
Qp =
______VO2_______
PVO2 – PAO2 x 10
Qs
______VO2_______
SAO2 - MVO2 x 10
=
L  R shunt = Qp – Qs
R  L shunt = Qs – Qp
Shunts (Bidirectional)
Qp =
Qs
___VO2__________
PVO2 – PAO2 x 10
=
___VO2__________
SAO2 - MVO2 x 10
Qep =
___VO2__________
PVO2 – MVO2 x 10
L  R shunt = Qp – Qep
R  L shunt = Qs – Qep
Shunt Ratio
Qp / Qs
= __SAO2– MVO2_
PVO2 – PAO2
Ratio can be estimated if saturation and
Hb are known.
Resistance to Flow
Systemic vasc. resistance (SVR)
Pulmonary vasc, resistant (PVR)
Dynes / sec. / cm-5 or Wood unit.
1 wood unit = 80 dynes / sec / cm-5.
Always calculated as related to BSA.
(Indexed)
Vasc. Resistance
R
=
___Delta P______
Q (l / m / M2)
SVR
=
__Ao (m) – RA (m)_
Qs (l / m / M2)
PVR
=
__PA m - LA m____
QP (l / m / M2)
Normally
PVR = 1 to 3 units
SVR = 15-30 units