Hamilton G5 - Introduction; Slopeco

E-2 624074/07
ECO
2
sensor option: Volumetric Capnography
E.1 Introduction
Capnography has become an important tool to evaluate the
adequacy of ventilation, as the obvious goal of ventilation is to
remove the CO
2
produced by the body’s metabolic processes.
But conventional, time-based capnography allows only quali-
tative and semi-quantitative, and sometimes misleading,
measurements, so volumetric capnography has emerged as
the preferred method to assess the quality and quantity of
ventilation.
To this end, the ventilator’s volumetric capnography measure-
ments provide the following information:
•The CO
2
elimination (V’CO
2
) measurement permits
assessment of metabolic rate (example., it is high with
sepsis, tetanus, and so on) and treatment progress.
•The end-tidal CO
2
(PetCO
2
and FetCO
2
) measurements
permit assessment of arterial CO
2
(Notice that they are
inaccurate in pulmonary embolism.).
•The airway dead space (VDaw) and alveolar minute ven-
tilation (V’alv) measurements permit assessment of actual
alveolar ventilation (as opposed to minute ventilation).
•The capnogram shape (slopeCO
2
) permits assessment of
COPD, asthma, and inefficient ventilation.
•The physiological dead space fraction (VD/Vt) permits
assessment of risk (Nuckton 2002).