Video Laryngoscope: A Review of the Literature

Abstract

Orotracheal intubation is the gold standard technique to secure the airways during general anesthesia, in the intensive care unit and in the often hostile prehospital setting. Major complications during airway management are mainly due to inability to secure or maintain the airways, because of an unexpected difficult tracheal intubation, an esophageal intubation, gastric aspiration, and/or iatrogenic trauma of the upper airways [1]. According to one of the most recent observational studies, difficult endotracheal intubation or problematic airway management may be not infrequent. Severe complications are reported to be close to 1/22,000, while death or brain damage occurs in 1:150,000 [2]; these complications are the main cause of anesthesia-related injury, possibly leading to major morbidity and mortality [3]. Large part of the perioperative adverse events associated with a problematic airway management occur to healthy individuals undergoing elective surgery under general anesthesia. Obesity and upper airway obstruction are since long-recognized risk factors for difficult airways, accounting by themselves for approximately 80 % of major complications. In “cannot ventilate and cannot intubate” situations, reiterations of attempts before changing strategy or considering alternative devices are associated with poor outcomes such as death and brain damage [2, 3]. Prediction of a difficult airway management is sometimes unreliable, being at best an inexact science, with poor sensitivity and specificity. Bedside predictors of difficulty are thyromental distance, sternomental distance, mouth opening, or a combination of tests and the laryngeal view obtained. Mallampati and more recently and perhaps more precisely El Ganzouri classifications can be used to predict difficult intubation [4]. Difficult glottic vision during intubation attempts is more frequent in emergency situations and in the critical care setting than during general anesthesia (grade III Cormack & Lehane: 13 % in emergency vs 5 % in general anesthesia; grade IV Cormack–Lehane 7 % vs 1 %, respectively) [2]. After the introduction in the early 1940s of Miller (1941) and Macintosh (1943), straight and curved laryngoscope blades to ease direct laryngoscopy, laryngoscopes (LA) remained largely unchanged for more than 50 years. With the development of rigid fiber-optic laryngoscopes – the first generation of video laryngoscopes – clinicians benefited from advances such as eyepieces that could be attached to optional video cameras. Rigid fiber-optic laryngoscopes placed the observer’s eye close to but above the glottis, allowing a controlled insertion and advancement of an endotracheal tube between the vocal cords. Flexible bronchoscopic intubation in case of intrahospital difficult airway management is today the standard method; this technique, however, requires adequate training and a routine use to be effective. In recent years the development of digital photographic and video techniques has led to video laryngoscopes (VDLs). These devices offer an improved (and shared) indirect view of the glottis on a remote or built-in video screen. A handle and a blade are the components of both LA and VDL, the latter having a fiber-optic or microvideo camera encased close to the end of the blade. The particular shape of the curve blade allows a wider viewing angle, making oral pharyngeal and tracheal axes alignment unnecessary, optical alignment being achieved by the video camera. According to Donati et al., VDLs are generally classified in three groups: (1) standard or Macintosh blade type, (2) angulated blade type, and (3) anatomically shaped with a guide channel [5]. The majority of these devices use a digital camera on the tip of a standard Macintosh or Miller laryngoscope blade providing the indirect visualization of the glottis on a video display (C-MAC, Glidescope, McGrath, Pentax Airway Scope). Less frequent is the use of fiber-optic cables connected to a display (Airtraq). Video laryngoscopes lack the versatility of flexible bronchoscopic intubation (FBI), but are more easy to use, less fragile, and provide a supraglottic vantage point. Learning curve, however, is not as short as proposed by someone.