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Using a CO₂ detector to confirm endotracheal intubation in SARS patients

Chien-Kun Ting, MD^*, Hsu-Tang Liu, MD^*, Kung-Yen Chen, MD^*, Chen-Kou Liu, MD^*, Mei-Yung Tsou, MD PhD^*,, Kwok-Hon Chan, MD^*, and Shen-Kou Tsai, MD PhD^*,

^* Taipei Veterans General Hospital, Taipei
Taiwan National Yang-Ming University, Taipei, Taiwan, E-mail: sktsai{at}vghtpe.gov.tw

To the Editor:

Severe acute respiratory syndrome (SARS) is a new respiratory viral epidemic with devastating impact on economics and the practice of medicine.¹ SARS struck Taiwan in the Spring of 2003, causing many deaths, serious morbidity and closure of provincial hospitals. The high infectious rate by droplet transmission places anesthesiologists at a substantial risk during tracheal intubation. Two physicians were infected during intubation resulting in mortality at the early stage of SARS in Taiwan. In addition to wearing personal protective equipment (PPE), using powered air purifying respirators (PAPR) during tracheal intubation can completely eliminate SARS-CoV contamination. PPE consisted of double gowns, double gloves, Tyvek hood (Texas America Safety Company, Brownwood, TX, USA), N95/100 mask (3M, Taipei, Taiwan), goggles and face shield.

However, wearing PPE with PAPR renders the user with impaired hearing, vision and communication. Verifying correct tracheal intubation by using a stethoscope for auscultation became difficult. There were 31 SARS patients who required tracheal intubation for mechanical ventilation at the Taipei-Veterans General Hospital. A total numbers of 37 intubations were performed because four patients had double intubations and one patient had triple intubations. In order to prevent cough with high viral content during intubation, after preoxygenation the tracheal intubation was facilitated by iv administration with propofol and succinylcholine. We then connected the disposable colorimetric end-tidal CO₂ detector (the Nellcor® Easy Cap^TM II) to the endotracheal tube to verify the correct endotracheal tube placement.

The CO₂ detector device (the Fenem FEF^TM CO₂ detector) was first introduced for confirmation of tracheal intubation in 1988.² It is a small, portable plastic attachment connected between the tube and catheter mount of the breathing system. It is also a semi-quantitative capnometer devoid of electronics. The EasyCap^TM II detector detects carbon dioxide in exhaled gases via a chemical coloured membrane and changes colour from purple to yellow. Such a change indicates the presence of CO₂ in the exhaled gas which passes. In our experience, the colour of the colorimetric end-tidal CO₂ detector changed from purple to yellow within six cycles of breathing ventilated by ambu-bagging after endotracheal intubation in SARS patients.

None of the anesthesiologists who performed the intubation procedure under the guideline was infected. The use of the disposable colorimetric end-tidal CO₂ detector could be a simple and reliable way of confirming correct tracheal intubation in SARS patients while wearing PPE with PAPR.

References

1 Kamming D, Gardam M, and Chung F. Anaesthesia and SARS (Editorial). Br J Anaesth 2003; 90: 715–8.[Free Full Text]

2 O’Callaghan JP, Williams RT. Confirmation of tracheal intubation using a chemical device. Can J Anaesth 1988; 35: S59 (abstract).[Medline]

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