To the Editor:- We read with interest the study by Dr. Isono et al. investigating the effect of mandibular advancement on pharyngeal patency in obese anesthetized persons. [1]Their observation is important clinically.

We, however, questioned the method to measure the cross-sectional area of the pharynx endoscopically. The authors copied isocontour of the pharynx on the fiberoptic bronchoscope (FOB) camera monitor onto the tracing paper and converted the weight of the paper, which was cut along the trace to square centimeters of the pharynx. The size of one square centimeter in the outer area of the FOB view, however, differs from that in the inner area because of the curvature of the FOB view, as shown in Figure 1and Figure 2. There can be a difference between the weight of the paper in the inner area and that in the outer area even if both are the same. Therefore, it should be cautioned that the cross-sectional area measured by the FOB technique is influenced by the position on the visual field of the FOB.

Figure 1. The 5 mm x 5 mm graph paper.
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Figure 1. The 5 mm x 5 mm graph paper.

Figure 1. The 5 mm x 5 mm graph paper.
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Figure 1. The 5 mm x 5 mm graph paper.

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Figure 2. Fiberoptic view of the graph paper. The same 5 mm x 5 mm graph paper as in Figure 1was kept 2.5 cm away from the tip of the fiberoptic bronchoscope (FOB, BF-P30 Olympus, Tokyo, Japan) and photographed using a camera (SC16–10 Olympus) attached to the FOB. Note that the size of one square centimeter in the outer area (A) differs from that in the inner area (B) because of the curvature of the FOB view.
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Figure 2. Fiberoptic view of the graph paper. The same 5 mm x 5 mm graph paper as in Figure 1was kept 2.5 cm away from the tip of the fiberoptic bronchoscope (FOB, BF-P30 Olympus, Tokyo, Japan) and photographed using a camera (SC16–10 Olympus) attached to the FOB. Note that the size of one square centimeter in the outer area (A) differs from that in the inner area (B) because of the curvature of the FOB view.

Figure 2. Fiberoptic view of the graph paper. The same 5 mm x 5 mm graph paper as in Figure 1was kept 2.5 cm away from the tip of the fiberoptic bronchoscope (FOB, BF-P30 Olympus, Tokyo, Japan) and photographed using a camera (SC16–10 Olympus) attached to the FOB. Note that the size of one square centimeter in the outer area (A) differs from that in the inner area (B) because of the curvature of the FOB view.
View largeDownload slide

Figure 2. Fiberoptic view of the graph paper. The same 5 mm x 5 mm graph paper as in Figure 1was kept 2.5 cm away from the tip of the fiberoptic bronchoscope (FOB, BF-P30 Olympus, Tokyo, Japan) and photographed using a camera (SC16–10 Olympus) attached to the FOB. Note that the size of one square centimeter in the outer area (A) differs from that in the inner area (B) because of the curvature of the FOB view.

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Nariaki Nakura, M.D.

Ichiro Takenaka, M.D.

Tatsuo Kadoya, M.D.

Department of Anesthesiology; Nippon Steel Yawata Memorial Hospital; Yahatahigashi-ku, Kitakyusyu, Japan

Kazuyoshi Aoyama, M.D.

Department of Anesthesiology; Moji Rosai Hospital; Moji-Ku, Kitakyusyu, Japan

(Accepted for publication April 7, 1998.)

1.
Isono S, Tanaka A, Tagaito Y, Sho Y, Nishino T: Pharyngeal patency in response to advancement of the mandible in obese anesthetized persons. Anesthesiology 1997;87:1055-62
Copyright 1998 by the American Society of Anesthesiologists, Inc.