To the Editor:-The nasal cannula is one of the most commonly used methods of administering supplemental oxygen and sampling end-tidal carbon dioxide (ETCO(2)) for the monitoring of respiratory rate and rhythm in patients undergoing sedation for surgical procedures. Although it is a convenient method of delivering oxygen, patients sometimes complain about nasal irritation from placement of the nasal cannula and drying of the nasal passages from oxygen administration. The Bitegard (Gensia Automedics, Inc., San Diego, CA) is a recently produced bite block used in patients undergoing general anesthesia to prevent endotracheal tube occlusion. This bite block may also be used in the awake patient with minimal discomfort. We present a modification of the Bitegard that may be used for the administration of supplemental oxygen and sampling of ETCO(2) in patients undergoing intravenous conscious sedation.

Taking a standard nasal cannula with oxygen and ETCO(2) sampling ports, the nasal prongs are cut off and the oxygen and ETCO(2) sampling lines are separated. The lines are then glued to the lateral grooves of the bite block (the nonbiting surface) with sterile medical adhesive. Special consideration must be taken to ensure proper placement of the ETCO2line because it is a suctioning sample line and may become occluded by adjacent tissue or saliva. The ETCO2line should be placed on the tongue side of the Bitegard because this line may become occluded if it is placed adjacent to the cheek. In addition, the ETCO2line should be secured at the most proximal portion of the bite block to ensure that saliva does not occlude the sample line. The oxygen and ETCO2lines are then fastened to the arm of the Bitegard with plastic chest-tube bands and secured with a chest-tube banding gun (Figure 1A). The modified Bitegard is placed directly into the patient's mouth with the plastic hook of the modified Bitegard turned to the patient's cheek side. Alternatively, the modified Bitegard may be turned on its side and placed in the patient's mouth with the plastic hook turned to the patient's chin. Mouth breathing should be encouraged once the modified Bitegard is in place.

Figure 1. (A) Modified BiteGard. (B) Modified Bitegard demonstration by the author.

Figure 1. (A) Modified BiteGard. (B) Modified Bitegard demonstration by the author.

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We used this device on 10 patients scheduled for outpatient ophthalmic procedures, after approval of the protocol by the institutional review board of human experimentation. Six of the patients receiving the modified Bitegard observed having a dry mouth after their 30-min procedure and two patients stated that the device was tolerable but mildly uncomfortable. Three patients experienced no discomfort or dry mouth. ETCO2waveform was present in two patients throughout their procedures without any occlusion. Five patients showed intermittent ETCO2waveform and therefore experienced periodic sample-line occlusion or nasal breathing. Three patients showed no ETCO2waveform. In every case, the modified Bitegard did not interfere with the surgical field, and the surgeons were satisfied with the oxygen technique. The oxygen saturation in all patients increased from the patient's baseline to 99% with an oxygen flow rate of 2 l/min. All patients tolerated the modified Bitegard without complication. In certain patients, the modified Bitegard may be an acceptable alternative to nasal cannula oxygen supplementation because it does not interfere with the surgical field during facial or ocular surgery. In addition, this device easily inserts into the patient's mouth (Figure 1B).

We have found the modified Bitegard to be easy to prepare, tolerable for the patient, and a simple alternative to nasal cannula oxygen supplementation and monitoring of ETCO2in patients undergoing monitored anesthesia care.

Andrea R. Williams, M.D.

Keith Tomlin, M.D.

Department of Anesthesia and Perioperative Medicine; Medical University of South Carolina; Charleston, South Carolina

(Accepted for publication August 27, 1998.)