Philips M3000A, Руководство по обслуживанию

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Mainstream CO
2
Measurement
56 Introduction to the Instrument
Mainstream CO
2
Measurement
Description
The M3016A Measurement Server Extension has a mainstream carbon dioxide respiratory
gas measurement for the Monitor monitoring device. It is designed to be used with the
M3000A Measurement Server for adult, pediatric, or neonatal patients, in a hospital
environment and during patient transport in and outside hospitals by clinical users.
CO
2
respiratory gas measurements indicate the efficiency of the transfer of oxygen from
alveolar air into pulmonary capillary blood and the elimination of carbon dioxide from
pulmonary capillary blood and its transfer into alveolar air.
CO
2
respiratory gas measurements are evaluated as gas passes through the airway adapter on
the patient’s intubation system. CO
2
respiratory gas measurements are an indication of the
patient’s overall respiratory status.
Blood Gas concepts important to this section are:
• Airway Respiration Rate (AwRR)—The number of inspirations and expirations per
minute.
• End Tidal CO
2
(EtCO
2
)—Highest partial pressure of CO
2
measured during one expira-
tion.
• Inspired Minimum CO
2
(ImCO
2
)—Lowest partial pressure of CO
2
during inspiration.
• Instantaneous CO
2
—The CO
2
measurement at any instant.
• Ventilation—The movement of air in and out of the lungs by inspiration and expiration.
Measurements
The mainstream CO
2
measurement produces respiratory CO
2
gas readings in a real-time CO
2
waveform together with numerics for End Tidal CO
2
(EtCO
2
), Airway Respiration Rate
(AwRR), and Inspired Minimum Carbon Dioxide (ImCO
2
).
Factors affecting accurate measurement of mainstream CO
2
respiratory gas are as follows:
• Correct cleaning of the windows on the airway adapter and the transducer.
• Correct placement of the transducer on the airway adapter.
• Temperature of the patient’s breath.
• Amount of water vapour in the patient’s breath.
• Barometric pressure at the site of measurement acquisition.
• Other gases, most notably N
2
O and O
2
, in the gas mixture.
The EtCO
2
(End Tidal Carbon Dioxide) measurement for Carbon Dioxide uses a technique
based on the absorption of infrared radiation by certain gases.
Infrared light is absorbed by CO
2
. The amount of absorption varies according to the CO
2
concentration in the gas mixture. By using an infrared detector to measure the absorption, the
CO
2
concentration in a gas can be derived.