lead to measurement error, depending on the frequency

response of the capnograph; different capnographs may

have different frequency responses.

3. Contamination of either the monitor or the sampling

system by secretions, blood, or condensation may lead

to inaccurate results.

4. Large dead space affects PetCO2 measurements. The

difference between PetCO2 and PaCO2 increases as

dead-space volume increases and may vary within the

same patient over time.

5. The PetCO2 adapter can add to the dead space and

resistance of the respiratory circuit, particularly in small

infants.

6. PetCO2 measurements may not provide an accurate

correlation with PaCO2 in small preterm infants with

nonhomogenous lung disease and, therefore, cannot be

substituted for PaCO2 analyses in preterm infants during this critical period (19,20).

7. Acute pulmonary hypoperfusion during cardiac surgery

may be associated with a sudden decrease in PetCO2

and mimic accidental endotracheal extubation (21).

G. Equipment

1. Use adaptors specifically designed for neonatal application.

2. For mainstream capnography, an airway adapter is

needed, along with a reusable sensor attachment.

3. For sidestream capnography, an airway adapter with

sampling tube is used (Fig. 11.3).

4. Sidestream technology can be used with nasal prongs

in spontaneously breathing patients.

5. Capnograph or capnometer

H. Precautions

1. In the mainstream adapter, prevent condensation in

the airway adapter.

2. In the sidestream adapter, prevent fluid (water) buildup

in the sampling tube.

3. For both mainstream and sidestream, when adding

bulk to the endotracheal tube, extra attention should be

given to properly securing the position of the tube.

4. Tidal volume measurements may be affected if the

PetCO2 adapter is placed between the endotracheal

tube and the ventilator flow sensor.

I. Technique

1. Familiarize yourself with the system before proceeding.

2. Follow manufacturer’s instructions for equipment calibration

3. Attach the adapter in line with the endotracheal tube

and the ventilator T piece (both sidestream and mainstream) (Fig. 11.4).

4. For mainstream capnography, connect the sensor to the

airway adapter.

Fig. 11.1. Mainstream capnographic monitor unit and clip-on

sensor assembly. (Courtesy of Respironics, Inc., Murrysville,

Pennsylvania.)

Fig. 11.2. Sidestream capnographic monitor unit with sample

line. Note PetCO2 value and wave. (Courtesy of Oridion

Capnography, Needham, Massachusetts.)