Physio Control LIFEPAK 15, Руководство по эксплуатации

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Chapter 4 | Monitoring
©2007-2015 Physio-Control, Inc. LIFEPAK 15 Monitor/Defibrillator Operating Instructions
89
You can set up the LIFEPAK 15 monitor/defibrillator to use the capnography Body Temperature
Pressure Saturated (BTPS) conversion method. This option corrects for the difference in
temperature and moisture between the sampling site and alveoli. The correction formula is 0.97
× the measured EtCO
2
value. See the LIFEPAK 15 Monitor/Defibrillator Setup Options provided
with your device.
EtCO2 Monitoring Waveform Analysis
Valuable information concerning the patient’s expired CO
2
can be acquired by examination and
interpretation of the waveform.
The Phases of the Waveform
The following figure is a graphic representation of a normal capnograph waveform. Four
phases of the waveform require analysis. The flat I–II baseline segment (Respiratory Baseline)
represents continued inhalation of CO
2
-free gas. This value normally is zero. The II–III
segment (Expiratory Upstroke), a sharp rise, represents exhalation of a mixture of dead space
gases and alveolar gases from acini with the shortest transit times. Phase III–IV (Expiratory
Plateau) represents the alveolar plateau, characterized by exhalation of mostly alveolar gas.
Point IV is the end-tidal (EtCO
2
) value that is recorded and displayed by the monitor. Phase
IV–V (Inspiratory Downstroke), a sharp fall, reflects the inhalation of gases that are CO
2
-free.
Alterations of the normal capnograph or EtCO
2
values are the result of changes in
metabolism, circulation, ventilation, or equipment function.
Figure 27 Phases of the Respiratory Waveform
Respiratory Baseline Elevation of the waveform baseline (I–II segment) usually represents
rebreathing CO
2
. This elevation usually is accompanied by gradual increases in the
EtCO
2
value. Rebreathing CO
2
is common in circumstances of artificially produced increased
dead space and hypoventilation. Precipitous rises in both baseline and EtCO
2
values usually
indicate contamination of the sensor.
Expiratory Upstroke In the normal waveform, the rising phase (II–III segment) is usually
steep. When this segment becomes less steep, CO
2
delivery is delayed from the lungs to the
sampling site. The causes of this delay can be physiologic or mechanical and include
bronchospasm, obstruction of the upper airway, or obstruction (or kinking) of an
endotracheal tube (ETT).
Expiratory Plateau The plateau of the waveform, which represents the remainder of
expiration (III-IV segment), should be nearly horizontal. The end of the plateau represents the
EtCO
2
value. Upward slanting of the expiratory plateau occurs when there is uneven
emptying of the alveoli. Similar to the diminished slope of the Expiratory Upstroke, this
pattern can occur in asthma, chronic obstructive pulmonary disease (COPD), partial upper-
airway obstruction, or partial mechanical obstruction such as a partially kinked ETT.