New applications of capnography

 

  Capnography versus bronchoscope during percutaneous tracheostomy 

A prospective randomized controlled trial of capnography vs. bronchoscopy for Blue Rhino percutaneous tracheostomy.

Mallick A, Venkatanath D, Elliot SC, Hollins T, Nanda Kumar CG.  A prospective randomized controlled trial of capnography vs. bronchoscopy for Blue Rhino percutaneous tracheostomy. Anaesthesia. 2003 Sep; 58(9): 864-8.

 A crucial step for successful percutaneous tracheostomy is the introduction of the needle and guide wire into the trachea. Capnography has recently been proposed as one way to confirm tracheal needle placement. In this randomized controlled study, the authors used capnography in 26 patients and bronchoscopy in 29 patients to confirm needle placement for percutaneous tracheostomy using Blue Rhino kit. The operating times and the incidence of peri-operative complications were similar for both groups. Capnography proved to be as effective as bronchoscopy in confirming correct needle placement.

 

Capnography for feeding tube insertion

Pulmonary complications of feeding tubes: a new technique of insertion and monitoring malposition. 

D'Souza CR, Kilam SA, D'Souza U, Janzen EP, Sipos RA. Can J Surg.  1994 Oct; 37(5): 404-8.

The study consisted of thirteen anesthetized adult patients and 7 awake subjects scheduled to undergo elective surgery. Airway sampling for carbon dioxide with capnography was performed in 13 anesthetized adults with the tip of the feeding tube in the pharynx, in the esophagus and in the trachea, and airway sampling for carbon dioxide from the pharynx and esophagus in 7 awake subjects during introduction of the feeding tube. Fluoroscopic monitoring of the position of the tip of the feeding tube was performed during introduction in two patients and two volunteers.  In all patients, with the tube either in the trachea or pharynx, a normal capnogram was displayed. When the tube was introduced into the esophagus no capnogram curve was seen, indicating the absence of carbon dioxide. With the subject lying down during introduction, the weighted tube followed the posterior pharyngeal wall to the upper esophageal sphincter. 

CONCLUSION: Positioning of the patient lying down with the head flexed and capnographic measurement of carbon dioxide levels from the tip of the feeding tube during insertion is a safe, accurate and cost-effective method for the introduction of feeding tubes.

 

 Capnography confirms correct feeding tube placement in intensive care unit patients. 

Kindopp AS, Drover JW, Heyland DK. Can J Anaesth. 2001 

The authors tested the accuracy and potential time savings of capnography as compared with a two-step radiographic method in placing feeding tubes in critically ill patients.  One hundred feeding tube placements were studied in a tertiary care intensive care unit. All placements utilized a two-step radiographic method, but capnography was added to the procedure. The procedure was then completed or abandoned depending on radiographic interpretation. Radiography showed 11 feeding tubes projecting within the tracheobronchial tree. In all 11 of these placements, the capnography unit displayed a normal capnogram. Radiography revealed 86 tube placements in the midesophageal region. In all 86 of these placements, capnography displayed a "purging warning". In three placements, radiography indicated that the tube was coiled in the oropharynx. In these cases, the capnograph displayed one "no purging/no capnogram" result, and two "purging" warnings. If using capnography alone, an average of 72.5 min would be required to complete a feeding tube placement (which includes time for requisite "pre-feed radiograph"). The two-step radiological approach took an average of 169.4 min, a difference of 96.9 min (P <0.0001) between the two methods. 

CONCLUSIONS: Capnography accurately identified all intratracheal feeding tube placements in this study. This study also shows that the use of capnography would significantly shorten the time needed for tube placement compared with a two-step radiologic method. The authors conclude that capnography should be considered for routine use when placing feeding tubes since it adds little time to the procedure and may improve patient safety. 

 

 Report on the development of a procedure to prevent placement of feeding tubes into the lungs using end-tidal CO2 measurements. 

Burns SM, Carpenter R, Truwit JD. Crit Care Med. 2001 May; 29(5): 936-9.

: To determine the accuracy of a technique using capnography to prevent inadvertent placement of small-bore feeding tubes and Salem sump tubes into the lungs. : A total of 25 ventilated adult MICU patients were studied-5 in phase 1 and 20 in phase 2. Phase 1 tested the ability of the end-tidal CO2 (ETCO2) monitor to detect flow (and thus accurately detect CO2) through small-bore feeding tubes. A small-bore feeding tube, with stylet in place, was placed 5 cm through the top of the tracheostomy tube ventilator adapter in five consecutive patients. The distal end of the feeding tube was attached to the ETCO2 monitor. The ETCO2 level and waveform were assessed and recorded. Because CO2 waveforms were successfully detected, a convenience sample of 20 adult MICU patients who were having feeding tubes placed (13 Salem sump tubes, 7 small-bore feeding tubes) was then studied. The technique consisted of attaching the ETCO2 monitor to the tubes and observing the ETCO2 waveform throughout placement. Of the seven small-bore feeding tubes tested, all were successfully placed on initial insertion. Placement was confirmed by absence of an ETCO2 waveform and by radiograph. Of the 13 Salem sump tubes, 9 were placed successfully on first attempt and confirmed by absence of CO2 and by air bolus and aspiration of stomach contents. ETCO2 waveforms were detected with insertion of four of the Salem sump tubes; the tubes were immediately withdrawn, and placement was reattempted until successful. 

CONCLUSIONS: The technique described is a simple, cost-effective method of assuring accurate gastric tube placement in critically ill patients.