Why Were Rigid and Semirigid Fiberoptic and Video Laryngoscopes Developed?
Macewan originally performed endotracheal intubation with his fingers.1 In 1913 Janeway used a speculum very similar to the laryngoscopes introduced by Miller and Macintosh in 1941 and 1942, respectively.2 And until recently, we’ve remained largely dependent upon the line-of-sight technique exemplified by direct laryngoscopy (DL). It was proposed that “the sniffing position” aligns the axes of the mouth, pharynx, and trachea, yet the incisors, the tongue, the epiglottis, and occasionally the position of the larynx itself, often conspire against a clear line-of-sight view. Studies on conscious adults with normal airway features, in neutral, sniffing, and simple extension demonstrate that positioning alone does not align the axes3 and there was little difference between the sniffing position and simple extension in a large series of patients undergoing DL.4 If positioning does not align these axes, how do we accomplish intubation by DL? We apply force, displacing and compressing the tongue, mandible, and frequently the larynx itself. Yet even among adults with seemingly normal airways, it is not possible to view the larynx by direct means in approximately 6% to 10%.5–7 Despite attempts to do so, we frequently fail to identify patients in whom DL will prove difficult or worse.8 Studies suggest that when DL fails, all too frequently we try harder and have more attempts,9 sometimes with adverse consequences.9–11
Instruments that are more or less anatomically shaped can overcome the anatomical barriers that may make DL difficult or impossible. Rigid and semirigid fiberoptic, optical, and video laryngoscopes are designed specifically for this purpose.
Another significant limitation of DL is that the experience is difficult to share.12,13 Since only the laryngoscopist can visualize the glottis during the laryngoscopy, this reduces the ability of an assistant in anticipating the laryngoscopist’s needs, complicates the teaching and recording of laryngoscopy, limits clinical documentation and the possibilities for quality improvement as well as the conduct of airway research. Video laryngoscopy circumvents many of these limitations but generally relies upon alternative devices.
Flexible endoscopes have greatly expanded our ability to diagnose and manage problems in previously inaccessible body parts. These devices are versatile but complex. For tracheal intubation, flexible fiberoptic and video endoscopes demand a different skill set than DL. Nonetheless, practitioners must master these devices since they remain to play an important role in some situations. Unfortunately, their complexity and versatility also add to their cost and fragility. As well, blood, secretions, vomitus, or fogging may significantly interfere with visualization.
Fiberoptic and video technology have been incorporated into flexible, semi-rigid, or rigid devices, designed specifically for tracheal intubation. Flexible fiberoptic and video endoscopic intubation will be discussed in Chapter 10. Rigid and semi-rigid devices may be stylet-like, channeled, or nonchanneled and blade-like (see Figure 11.1). All provide illumination and enable ...