Comparison between the Truview PCD™ or the GlideScope® video laryngoscope and direct laryngoscopy for tracheal intubation in pediatric patients

Abstract

To the Editor, In a randomized clinical trial, Riveros et al. compared the performance of the Truview PCD or the GlideScope video laryngoscope (GVL) with Macintosh laryngoscopy for tracheal intubation in children aged neonatal to ten years. Trial results showed that the laryngeal view obtained with the original GVL was significantly worse than that obtained with a Macintosh laryngoscope. The findings were not in agreement with those of two recent randomized studies in which a second generation Cobalt GVL provided a laryngeal view in children superior to that provided by direct laryngoscopy. Riveros et al. attributed their findings to the limited size options in the original GVL blades for the study participants. In our view, the unique characteristics of the Cobalt GVL blades vs the original GVL blades also account for differences in laryngeal visualization between the two recent studies and Riveros et al.’s study. The disposable blades of the Cobalt GVL are narrower and longer than the reusable blades of the original GVL. This enables manipulation of laryngeal structures and allows more room in the oral cavity to insert the tracheal tube. Furthermore, the original GVL uses a curved blade with a 60 angle in the midline, and the field of view of the camera does not cover the tangent of the distal half of the blades. This results in a blind area below the blade tip. Hirabayashi et al. show that the blind area below the blade tip of the original GVL is 2 mm and 13 mm in the smalland medium-size blades, respectively. Although a small blind area below the blade tip of the small-size GVL blade may not interfere with laryngoscopy, the mid-size GVL blade with a 13-mm width blind spot may require a camera view in a more anterior direction and optimum external laryngeal manipulation to obtain better exposure of the glottis. Kim et al. have shown that Cormack and Lehane grades of laryngeal visualization using the original GVL without optimum external laryngeal manipulation can overestimate the reported frequency of difficult laryngoscopy in children aged three months to 17 yr. Compared with the original GVL, however, the camera of the Cobalt GVL is closer to the blade tip, especially in pediatric devices. In the original GVL, the blade length in front of the camera is 3.6 cm, 5.5 cm, and 6.1 cm in the small-, medium-, and large-size blades, respectively, whereas in the Cobalt GVL, the blade length in front of the camera is 0.7 cm, 1.5 cm, 2.8 cm, 3.7 cm, and 5.3 cm, in size 0, 1, 2, 3, and 4 blades, respectively (http://verathon.com/language/ en-us/products/glidescope.aspx). Due to the smaller distance between the camera and blade tip, the airway structures can be visualized with the pediatric Cobalt GVL without a blind area below the blade tip. Additionally, the proper function of a laryngoscope is dependent on using an appropriate blade length. In the Methods section of their study, Riveros et al. described use of the small Truview PCD blade for neonates and infants, whereas the medium-size blade was used for children. Currently, five sizes of the Truview PCD blades are commercially available. The manufacturer (Truphatek International Ltd., Netanya, Israel; www.truphatek.com), recommends the following blade sizes: size 0, for patients aged less than one year and weighing 0.8-4 kg; size 1, for patients aged one to K. P. Liu, MD C. H. Li, MD Department of Anesthesiology, China-Japan Friendship Hospital, Beijing, China