Datex-Ohmeda S/5 Anesthesia Monitor
Document No. 800 1005-1
8
2.1.4
Patient Spirometry
In anesthesia, CMV (Controlled Mechanical Ventilation) is the mostly used ventilation mode. In this
mode, mechanical breaths are delivered to the patient by a ventilator with a proper tidal volume
(TV), respiration rate (RR), and inspiration/expiration ratio in time (I:E) determined by the settings of
the ventilator.
Delivery of life support gases is based on pressure. However, without knowing volume measured of
exhalation, one cannot be sure that a breath occurred. The ultimate goal of ventilation is to use the
least amount of pressure to generate the most appropriate volume for each breath.
The Patient Spirometry monitors ventilation in anesthesia. Both patient breathing circuit and the
function of the ventilator are monitored. The following parameters are displayed:
Expiratory and inspiratory tidal volume (TV) in ml.
Expiratory and inspiratory minute volume (MV) in l/min.
Expiratory volume in first second (V1.0) in per cent for adults and in 0.5 seconds for children.
Inspiration/expiration ratio in time (I:E)
Airway pressures: Peak pressure (P
peak
), End inspiratory pressure (P
plat
), Positive end expiratory
pressure (PEEP), Real time airway pressure waveform (P
aw
)
Flow: Real time flow waveform (V')
Compliance (C)
Pressure volume loop
Flow volume loop
Airway pressure
PEEP, P
peak
, and P
plat
are measured by pressure transducer on the PVX board. Atmospheric pressure
is used as a reference in measurement. The pressure measurement is made from the airway part
that is closest to the patient between patient circuit and intubation tube.
Airway flow
The measurement is based on measuring the kinetic gas pressure and is performed using Pitot
effect. Pressure transducer is used to measure the Pitot pressure. The obtained pressure signal is
linearized and corrected according to the density of the gas. Speed of the flow is calculated from
these pressure values and TV value is then integrated. MV value is further calculated and averaged
using TV and RR (respiratory rate) values.
Содержание S/5 B-GAS
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