Hamilton G5 - Examples of Normal or Expected Values in Mechanically; Ventilated Patients

E-8 624074/07
ECO
2
sensor option: Volumetric Capnography
Table E-1. Examples of “normal” or expected values in mechanically
ventilated patients
1
Description Unit
2
Normal Reference
VDaw ml BTPS 2.2 ml/kg IBW Radford 1954
slopeCO
2
%CO
2
/l 31324*Vt-1.535 Aström 2000
V’CO
2
3
ml/min STPD 2.6 to 2.9 ml/min/kg Weissmann
1986Wolff 1986
FetCO
2
4
% 5.1 to 6.1% Wolff 1986
V’alv mmHg (kPa) 36 mmHg (4.8 kPa) Kiiski, Takala 1994
VD/Vt ml/min BTPS 52 to 70 ml/min/kg
actual body weight
5
VD/Vtbohr -- Normal:
0.36 to 0.42High:
> 0.63 ±0.1
Kiiski, Takala
1994 Wolff
1986 Nuckton
2002
6
1. These values are for illustration purposes and do not replace physician-directed treatment.
2. Bulk gas volumes such as minute ventilation and tidal volumes are usually measured in
BTPS. Specific gas volumes are expressed in STPD. Conversion factors can be found in
physics textbooks.
3. V’CO
2
= V’alv * FetCO
2
4. FetCO
2
= PetCO
2
/(Pb-PH
2
O)
5. V’alv = V’CO
2
/FetCO
2
STPD
Lower value of normal range:
V’alv = 2.6/0.061 = 43*ml*kg/min*STPD = 52*ml*kg/min*BTPS
Upper value of normal range:
V’alv = 2.9/0.051 = 57*ml*kg/min*STPD = 70*ml*kg/min*BTPS
6. VD/Vtbohr is equivalent to VD/Vt if PetCO
2
is identical to PaCO
2
. In normal lungs, this is the
case. In diseased lungs, however, PetCO
2
and PaCO
2
are not identical. The classic example
is pulmonary embolism.