Treaton MV200, User Manual

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5.2 Volume capnometry
5-5
5.2 Volume capnometry
Optionally the device may be equipped with the function of volume capnometry, which operates
only together with mainstream capnometer. Volume capnometer (sometimes the “volumetric
capnometer” term is used) allows to define the following parameters:
•
elimination of CO
2
per minute (VCO
2
), which characterizes the metabolism rate (e.g., high
value indicates sepsis etc.), and reflects the effectiveness of applied respiratory therapy in
dynamics;
•
functional dead space (Vd);
•
minute alveolar ventilation (MValv).
The calculation method of the CO
2
amount per expiration is the combined integration of patient
flow curve and the capnogram from the mainstream capnometer (Figure 5.5).
Figure 5.5 – Synchronization of the capnogram with the flow curve
СО
2
elimination per breathing cycle is:
∫ ∫
⋅ ⋅ − ⋅ ⋅ =
2
1
pat
3
2
pat
) ( 2 ) ( ) ( 2 ) ( 2
t
t
t
t
i
dt t CO t F dt t CO t F VCO
(1)
where: VCO2i – СО
2
elimination per i-breathing cycle, units, ml,
СО 2(t) – the relative concentration of CO
2
,
F
pat
(t) – the patient's flow rate, lpm.
Measuring units of VCO
2
are milliliters given to the patient’s condition (BTPS). Such reduction is
necessary for the correct application of the formulas for calculating other parameters.
Elimination of СО
2
per minute is:
∑
=
=
n
i
m
i VCO VCO
1
2 2
(2)
where: VCO
2
m – CO
2
elimination per minute,
n – number of breaths during the last minute.
t1 t2 t3
Flow, Fpat(t)
Capnogram, CO
2
(t)