Videolaryngoscopy using an Android smartphone: A direct digital technique.

Abstract

Sir, Direct laryngoscopy has been the standard of care in securing the airway, in both routine and emergent cases. Videolaryngoscopy, introduced about a decade earlier aims to overcome the limitations of direct laryngoscopy. Some of the disadvantages of direct laryngoscopy include the need for an optimal line of sight for glottic visualisation, greater cervical spine movement during laryngoscopy, a lack of visual feedback for other healthcare providers during resuscitation and for novices undergoing training in laryngoscopy, and lack of image archiving capability.[1,2] Despite the advantages, the high initial cost of investment remains a deterrent for the widespread adoption of videolaryngoscopy over direct laryngoscopy.[3] Videolaryngoscopy may be done inexpensively. The use of complementary metal oxide semiconductor sensors attached to the blade of a conventional Macintosh laryngoscope should suffice. The authors, in an earlier study, demonstrated the use of a low cost universal serial bus (USB) endoscope camera assembled on a Macintosh laryngoscope, to perform videolaryngoscopy.[4] The device used the video processing capabilities of a personal computer to display real time video. The evolution of this technique could then be to utilise the high quality display and graphical processing present in the ubiquitous smartphone, keeping the initial and recurring costs of the technique low. For technical reasons, the use of smartphones for displaying the video stream from an USB endoscope camera is not simple. We chose the Android smartphone operating system (OS) V3.1 or higher (checked using “about device” menu of the OS), that supports the USB on-the-go (OTG) host function. This feature allows direct interfacing of the USB camera with the mobile device using an USB OTG cable. Apple OS devices do not support a similar capability due to restrictions in its use of its host-capable USB port. Initial attempts at obtaining a video stream were unsuccessful, due to lack of inbuilt USB video class drivers in the Android OS kernel of several mobile devices. We attempted to recreate this functionality with open source custom software that processes the USB video stream directly in Google Nexus 2012 Android mobile device.[5] However, a high quality video recording was obtained in most of the mobile devices that we tested, by using “CameraFi” (Vault Micro Inc., Seoul, Korea) app freely downloaded from the online Google Play Store at https://play.google.com/store/apps/details?id=com.vaultmicro. CameraFi. The USB endoscope camera was disinfected prior to use, assembled and upright orientation done as described in our earlier study.[4] The USB camera was fixed about 40 mm from the tip of a Macintosh blade (size 3 or 4) using clean adhesive tape (Durapore, 3M Inc., USA). The application supported capture of high quality images as well as real time video capture Figure 1. The camera required minimal electrical power supplied through the USB port of the mobile device. The electrical safety of the camera was ensured due its completely insulated, waterproof casing. We had successfully tested this assembly for videolaryngoscopy in an adult mannequin. The mouth opening required by the USB camera-blade assembly was the same as that for a conventional Macintosh blade. Figure 1 Real time video capture from universal serial bus endoscope camera using CameraFi app in Android operating system This technique used readily available components with minor modification of a conventional laryngoscope. The technique involves direct digital transmission of the image to a smartphone through its USB port, without the use of cumbersome, optical-based smartphone adapters such as the Airtraq Universal Phone adapter (Prodol Meditec S.A, Vizcaya, Spain) that may affect image quality. Newer USB endoscope cameras of 5.5 mm diameter, 2 m cable length are available from online retailers, which are inexpensive, costing <10$, for example, at http://www.tomtop.com/product?q=endoscope+borescope. Future efforts would involve developing medical grade, 3D-printed laryngoscope conduits that encase the USB camera, conforming to all regulatory standards. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.