5) Accidental esophageal intubation  

Capnograms during esophageal intubation

Ingestion of carbonated beverages prior to anesthesia

When used with the standard technique of listening to breath sounds, C0₂ monitoring is probably the best way to detect esophageal intubation. Although C0₂ may be present in the stomach it is rapidly flushed out during ventilation of the stomach and the PETCO₂ reading would decrease, resulting in a flat capnogram.^1,2   Recently, PETCO₂ detectors, which change color on  exposure to 4% C0₂, have been used successfully to confirm tracheal intubation.³ These detectors can be used where CO₂ monitors are not available.³   It should be noted that in the presence of carbonated beverages in the stomach a PETCO₂ as high as 38 mmHg can be observed with esophageal ventilation and it may take at least six breaths for PETCO₂ to decrease to zero. However, the C0₂ waveforms produced as a result are abnormal in shape and, therefore, could be detected earlier by capnography than capnometry.⁴

(6) Blind nasal intubation

Continuous recordings of C0₂ at the proximal end of the nasal tracheal tube facilitate guiding of the tube towards the larynx during blind nasal intubation in the spontaneously breathing patient. As the tube is moved away from the larynx, the end-tidal recordings decrease.⁵ Carbon dioxide recordings can be replaced by audio signals that are proportional to C0₂ concentration (audio capnometry). This has the advantage that one does not have the distraction of looking at the capnometer during the procedure.⁶

(7) Proper positioning of double lumen-tubes

In addition to the standard methods available PETCO₂ monitoring of each lung may be a valuable adjunct not only for assuring proper tube placement, but also for detecting dislodgement of double-lumen tubes during the course of anesthesia. Correct placement of double-lumen tubes can be checked by analyzing individual C0₂ wave forms from each lung during clamping and unclamping procedures. Further, periodical monitoring of C0₂ wave forms from individual lungs may be useful to monitor ventilation of each lung particularly when the patient is prepared, draped, or when the chest is not available for auscultation, or the quality of breath sounds is not clear enough.⁷ To monitor C0₂ wave forms from each lung the author's practice is to incorporate a three-way stopcock into the sampling tube. The stopcock can be used to direct the flow from either lung individually or from both lungs simultaneously into the C0₂ monitor, thus obviating the need for two C0₂ monitors.^8,9  More details are presented in 'thoracic section'.

  References

1. Birmingham PK, Cheney FW, Ward RJ. Esophageal intubation: a review of detection techniques. Anesth Analg 1986;65:886-91.

2. Linlo K, Paloheimo M, Tammisto T. Capnography for detection of accidental oesophageal intubatio. Acta Anaesthesiol Sand 1983;27:199-202.

3. . 'O' Flaherty D, Adams AP.  The end-tidal carbon dioxide detector. Assessment of new method to distinguish oesophageal from tracheal intubation.  Anaesthesia 1990;45:653-5.

4. Sum Pink ST, Mehta MP, Symreng T.  Reliability of capnography in identifying esophageal intubation with carbonated beverage or anatacid in the stomach.  Anesth Analg 1991;73:333-7.

5. Linlo K, Paloheimo M. Capnography facilitates blind nasotracheal intubation. Acta Anaesthesiol Belg 1983;34:117-22.

6. Omoigui S, Glass P, Martel DIJ, et al. Blind nasal intubation with audio-capnometry. Anesth Analg 1991;72:392-3.

7. Shafieha MJ, Sit J, Kartha R et al. End-tidal CO2 analyzers in proper positioning of the double-lumen tubes. Anesthesiology 1986;64:844-5.

8. Shankar KB, Moseley H, Kumar AY.  Dual end-tidal CO2 monitoring and double-lumen tubes. Can J Anaesth 1992;39:1000-3.

9. Bhavani-Shankar K, Russell R, Aklog LMushlin P.  Dual capnography facilitates detection of a critical perfusion defect in an individual lung. Anesthesiology 1999; 90 (1): 302-304.