A NEW DEVICE FOR MEASURING AND RECORDING THE FORCES APPLIED DURING LARYNGOSCOPY

In characterising the forces exerted during laryngoscopy it is accepte d that the significant force component is that which is parallel to th e axis of the laryngoscope handle. This paper describes a new method o f evaluating the forces exerted at laryngoscopy. A laryngoscope handle has been redesigned, incorporating a force-displacement transducer on the handle at the end opposite to where the blade is attached The dev ice is designed specifically to sense the axial component of force. Th e blade attachment block has been detached from the sleeve and connect ed to a steel shaft which forms the new battery compartment. This allo ws the axial farce exerted al the blade during laryngoscopy to be tran smitted along this shaft to the sensing transducer. Lineal ball bearin gs have been introduced between the new shaft and the handle sleeve (o uter casing). The rolling friction has been reduced to less than 0.1% by diamond-lapping the precision ground surface-hardened rod to produc e a mirror finish. Thus, the force transmitted to the transducer is es sentially constant regardless of where the load is applied along the b lade. The output from the system is directly downloaded to a laptop co mputer and the data analysed almost instantaneously to determine the d uration of laryngoscopy, the peak forces applied, the mean force with its standard deviation and graphic display of the data. Provision has been made for data entry checks, recording patient details and study d ata, and creating a data base for the storage and retrieval of the stu dy details.