GB2329837A - Laryngoscope - Google Patents

Abstract

The laryngoscope, which can detect and indicate correct use thereof, comprises a blade 2, an operating arm 4 connected thereto, a hand grip 8 surrounding the arm and sensing means operatively connecting the arm and the grip, such means including a resiliently deformable member 10 and a plurality of sensors 12 mounted thereto to sense deformation caused by incorrect movement of the hand grip. The sensors may be strain gauges of resistance or semi-conductor type or a fluid system utilising a flexible diaphragm may be used. During proper use, the axial thrust and torque applied by the operator to the grip should be of a constant proportion to one another. The laryngoscope may also serve as a training tool for anaesthetists.

Description

LARYN GOS COPE This invention relates to a laryngoscope, more particularly to an apparatus which detects and provides warning of potentially harmful forces imposed on a patient during a process of endotracheal intubation.

A laryngoscope is a device having a blade and a handle and is commonly used when it is necessary to introduce a ventilation tube through the trachea of a patient in order to assist respiration. This may be necessary when a patient is unconscious during a surgical procedure or as a result of injury. The blade of the laryngoscope is inserted through the mouth of the patient and allows the operator to apply an appropriate force via the handle to expose the opening of the larynx so that a ventilation tube can be inserted.

One problem which may occur during use of a laryngoscope is that potentially harmful forces can be accidentally exerted on parts of the patient's body other than the appropriate tissue structure. In particular, damage to the patient's teeth or fixed dental prostheses is common.

Such improper forces and accidental damage can be caused by incorrect operator technique.

Specifically, an incorrect combination of torque and direct thrust can produce unwanted contact stresses on the patient.

During ideal use of the laryngoscope the force applied to the patient by the blade is supplied by a thrust from the operator's hand on the handle in a direction co-axial with the handle and away from the patient. The separation between such blade force and hand grip force generates a force moment which is balanced by a net torque applied to the hand grip by the operator. The nominal location of the line of action of the net resultant force on the blade is predetermined by the geometry of the blade which is matched to typical anatomical dimensions of patients of similar stature. It follows from the above that during proper use the axial thrust and torque applied by the operator to the hand grip should be of a constant proportion to each other. The correct proportion will be substantially similar across a range of patients of similar stature.

It is an object of the present invention to provide a laryngoscope which can detect and indicate correct use of the laryngoscope. From this follows another object which is to provide a training tool for anaesthetists enabling them to learn correct technique.

According to the present invention there is provided a laryngoscope comprising a blade, an operating arm connected thereto, a hand grip surrounding the operating arm, sensing means connecting operatively the operating arm and the hand grip, said sensing means comprising a resiliently deformable member connected at at least one point to the hand grip and to the operating arm at at least one other point remote from the first mentioned point and a plurality of sensors mounted to said deformable member to sense deformation caused by incorrect movement of the hand grip.

Preferably there is provided means to indicate a combined result of variations in individual ones of said plurality of sensors.

The sensors may be resistors.

The deformable member may comprise two mutually orthogonal portions.

In this case, at least one of the sensors may detect deformation of one portion and another of the sensors may detect deformation of the other portion.

A first portion of the deformable member may extend longitudinally of the hand grip and sensors mounted thereto may indicate torque applied to the hand grip.

A second portion of the deformable member may extend in a direction transverse to the first and sensors mounted thereto may indicated longitudinal pull of the hand grip.

Preferably four sensors are provided, two on each portion. Each is so configured and located that the output indication is unchanged from neutral when correct usage is being employed.

An embodiment of the invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which : Figure 1 shows a part sectional view of the general arrangement of the laryngoscope; Figure 2 is a cross sectional view, on an enlarged scale, of the connection between hand grip and blade; Figure 3 shows in perspective the disposition of strain gauges; Figure 4 shows the (exaggerated) deflected shape of a deflectable connecting member under neutral, ideal and various non-ideal loads. The table below shows resistances of corresponding strain gauges and the resulting effect on the voltage across a Wheatstone bridge circuit; and Figure 5 shows schematically a Wheatstone bridge circuit.

Referring now to the drawings a laryngoscope comprises a blade 2, an operating arm 4 connected to the blade 2 by means of hub 6 to extend perpendicularly therefrom. A hand grip 8 surrounding and mechanically connected to the operating arm 4 solely by means of a deformable connecting member 10 is adapted for manual grasping such that all forces and torques applied to the hand grip 8 by the operator are transmitted to the operating arm 4 by means of the deformable member 10.

The connecting member 10 is made of steel or the like so that it is sufficiently resiliently deformable for bending to be measurable. It comprises an axial longitudinally extending limb 10a connecting two transverse limbs 10b. The axial limb 10a of the deformable member is rigidly connected to the hand grip 8 by means of a mounting block 16. One end of each transverse limb 10b of the deformable member 10 is rigidly connected to the operating arm 4. Elastic or mechanical hinges 14 connect the transverse limbs 10b to the axial limb 10a so that no significant bending stresses within transverse limbs 10b are transferred to the adjoining axial limb 10a and no significant bending stresses within the axial limb 10a are transferred to either adjoining transverse limb 10b.

Electrical resistance strain gauges 12 are bonded to surfaces of the axial limb 1Oa and of the transverse limbs 10b. Strain gauges 12a and 12d are attached to the upper surface of transverse limbs 10b. Strain gauges 12b and 12c are attached to the front and rear surfaces respectively of the axial limb 10a.

The precise disposition of strain gauges 12 on the deformable member 10 and the physical shape and proportions of the deformable member 10 are such that each strain gauge suffers the same change in electrical resistance when the member is deformed by torque and axial force in the correct proportion to each other consistent with proper use of the laryngoscope.

The strain gauges may be semi conductors, resistance foil or the like. They need not necessarily be electrical - it being possible to use a fluid system utilising a flexible diaphragm.

Referring now to Figures 4 and 5, the strain gauges 12a and 12d are indicated by R2 and R1 respectively, whilst gauges 12b and 12c are indicated respectively by R4 and R3. They are connected together in a Wheatstone bridge circuit, as shown in Figure 5.

As may be seen from Figure 4 the Wheatstone bridge circuit is only balanced in the neutral, non stressed mode and when the pull and torque forces are correctly applied. Incorrect operation produces changes in the relative electrical resistances of said strain gauges to cause a change in a supplied voltage, which change can be indicated. Hence a single indicator can point to a particular form of correct usage.

Claims (9)

1. CLAIMS 1. A laryngoscope comprising a blade, an operating arm connected thereto, a hand grip surrounding the operating arm, sensing means connecting operatively the operating arm and the hand grip, said sensing means comprising a resiliently deformable member connected to the hand grip at at least one point and to the operating arm at at least one other point remote from the first mentioned point and a plurality of sensor means mounted to said deformable member to sense deformation caused by incorrect movement ofthe hand grip.
2. 2. A laryngoscope as claimed in Claim 1, wherein the deformable member comprises two portions, arranged to be substantially mutually orthogonal one to the other.
3. 3. A laryngoscope as claimed in Claim 2, wherein at least one ofthe sensor means is adapted to detect deformation of one of said orthogonal portions and another of the sensor means is adapted to detect deformation of another portion.
4. 4. A laryngoscope as claimed in either Claim 2 or Claim 3, wherein a first portion ofthe deformable member extends substantially longitudinally ofthe hand grip and sensor means mounted thereto are adapted to indicate torque applied to the hand grip.
5. 5. A laryngoscope as claimed in Claim 4, wherein a second portion of the deformable member extends in a direction transverse to the first and sensor means mounted thereto are adapted to indicate longitudinal pull of the hand grip.
6. 6. A laryngoscope as claimed in either Claim 4 or Claim 5, wherein four sensors are provided, two on each portion, with each so configured and located that the output indication is unchanged from neutral when correct usage is being employed.
7. 7. A laryngoscope as claimed in any one of Claims 1 to 6, wherein means are provided to indicate a combined result of variations in outputs of individual ones of said plurality of sensors.
8. 8. A laryngoscope as claimed in any one of the preceding claims, wherein the sensor means are resistors.
9. 9. A laryngoscope substantially as described herein with reference to the Figures of the accompanying drawings.