Chapter 11 ■ End-Tidal Carbon Dioxide Monitoring 77

5. For sidestream capnography, connect the sampling

tube to the analyzer.

J. Complications

1. With mainstream analyzers, the use of too large an airway tube adapter together with the weight of the probe

may introduce an excessive amount of bulk and weight

to the endotracheal tube increasing the risk of tube

kinking or dislodgement.

2. With sidestream capnography, a low–dead-space

adapter allows for less bulk and weight; however, care

must be taken not to pull excessively on the sample line

that is connected to the measurement instrument (6,7)

Colorimetric Carbon Dioxide

Measurement

Colorimetry provides a quick qualitative measure of CO2 in a

gas sample. This method uses a pH-sensitive chemical indicator (similar to a litmus paper) in a plastic housing that is

attached between the endotracheal tube and the ventilator circuit or positive-pressure delivery device. The pH-sensitive indicator changes color when exposed to CO2 (usually from purple to yellow, depending on the device). The response time is

sufficiently fast to detect exhaled CO2 within 1 or 2 breaths.

A. Indications

1. For confirmation of endotracheal tube placement

2. International consensus statements on neonatal resuscitation recommend that endotracheal tube placements be verified by using clinical signs and detection

of exhaled CO2 (22)

B. Procedure

1. Immediately following endotracheal intubation, attach

calorimetric CO2 detector to endotracheal tube adaptor and continue positive-pressure ventilation with

T-piece resuscitator or Ambu bag.

2. Within 1 to 2 breaths, the indicator color should

change from purple to yellow with every exhalation if

the tube is within the trachea and not in the esophagus.

Some CO2 detectors have a small plastic strip that

needs to be removed for the gas to flow through.

3. Remove the CO2 detector before attaching the ventilator circuit.

C. Limitations

1. This device is not very sensitive when CO2 output is

low, as may be the case in patients with cardiac arrest

and minimal CO2 excretion and in very preterm infants

during initial resuscitation (3,22,23)

References

1. Walsh BK, Crotwell DN, Restrepo RD. Capnography/

Capnometry during mechanical ventilation: Respir Care. 2011;

56(4):503.

2. Galia F, Brimioulle S, Bonnier F, et al. Use of maximum end-tidal

CO(2) values to improve end-tidal CO(2) monitoring accuracy.

Respir Care. 2011;56(3):278.

3. Wyllie J, Carlo WA. The role of carbon dioxide detectors for confirmation of endotracheal tube position. Clin Perinatol 2006

;33(1):111.

4. Rozycki HJ, Sysyn GD, Marshall MK, et al. Mainstream end-tidal

carbon dioxide monitoring in the neonatal intensive care unit.

Pediatrics. 1998;101:648.

5. Lightdale JR, Goldmann DA, Feldman HA, et al. Microstream

capnography improves patient monitoring during moderate sedation: a randomized, controlled trial. Pediatrics. 2006;117(6):e1170.

6. Kugelman A, Zeiger-Aginsky D, Bader D, et al. A novel method of

distal end-tidal CO2 capnography in intubated infants: comparison with arterial CO2 and with proximal mainstream end-tidal

CO2. Pediatrics. 2008;122(6):e1219.

Fig. 11.3. Infant sidestream low–dead-space adapter with sample

tubing. (Courtesy of Oridion Capnography, Needham, Massachusetts.)

Fig. 11.4. Infant sidestream low–dead-space adapter (arrow) in

line with endotracheal tube.