CareFusion AVEA - Alveolar Dead Space; Alveolar Ventilation (Va); Anatomic Dead Space; Tidal Volume Ratio (VD Ana; Vt); Oxygenation Index (OI)

236 Appendix I: Volumetric CO2 Calculations Operator's manual
L2786 Rev. M
Anatomic Dead Space / Tidal volume Ratio (Vd ana / Vt)
Anatomic dead space / Tidal volume ratio is used to calculate the ratio of the tidal volume not
participating in gas exchange (wasted ventilation). This is calculated on a breath to breath
basis. Vd phy / Vt is probably more clinically relevant, but requires an arterial blood sample to
be accurate.
Alveolar Dead Space
Alveolar dead space is (mathematically) the difference between physiological dead space and
anatomical dead space. It represents the volume of the respiratory zone that is from ventilation
of relatively under-perfused or non-perfused alveoli.
Alveolar Ventilation (V
A
)
The minute volume of fresh gas that participates in gas exchange.
Oxygenation Index (OI)
Oxygenation index is a dimensionless number often used to assess the “pressure cost” of
oxygenation. This parameter is calculated from the F
IO
2
mean airway pressure and an arterial
blood oxygen measurement entered by the clinician.
P
AO
2
/ FIO
2
Ratio (P/F)
The P
AO
2
/ FIO
2
ratio is a simple assessment of gas exchange. This parameter is calculated
from the F
IO
2
monitor value and an arterial blood oxygen measurement entered by the clinician.
Note:
Because PAO
2
may be entered in either mmHg or kPa, the normal range for parameters OI and
P/F differ depending on the setting of the CO
2
units control.