GB2296436A - Light conducting blades for examination and intubation of body cavities - Google Patents

Abstract

Light conducting clear plastic blade for insertion into a body cavity. e.g. as part of a laryngoscopo, illuminated by a light source contained in gap 6 where light passes through the proximal end 1 of the blade and is reflected off surface 2 by total internal reflection and is then conducted out of the blade through light carrying section 3. The blade also has a channel 5 allowing passage of tubes into said body cavity. The blade is particularly useful in neo-natal laryngoscopes and may also be used in nasal or gynaecological speculae with the advantages of disposability and reduced trauma to soft tissues. <IMAGE>

Description

LIGHT-CONDUCTING BLADES The present invention relates to light-conducting blades used to perform examinations of bodily cavities of humans and non-human mammals. In particular, it relates to a light-conducting laryngoscope which is particularly suitable for the examination of neonates.

Generally speaking, blades used for investigating cavities of the body which are not readily accessible have changed very little over the years. One example of such a blade is that used with neo-natal laryngoscopes, used for examination of the larynx and pharynx of neonates. The objective is to displace the tongue and expose the vocal cords to facilitate intubation of the larynx and trachea, thus allowing ventilation of the lungs by mechanical means. The neo-natal laryngoscopes currently used are essentially scaled-down versions of the laryngoscopes used for older children and adults.

Neo-natal laryngoscopes of this type have hardly changes in forty years, and they suffer from a number of disadvantages. The first is that the blades are made from metal and the light is delivered at a point some distance from the end of the blade. In order to attempt to deliver sufficient light to the vocal cords, the doctor must brace the metal blade upwards against the soft tissues of the neonate. This upward-bracing of a harsh metal blade against the soft tissues of the neonate can cause considerable trauma to the tissue.

The second main problem is that the necessary size, shape and relative positioning of the light-source and blade in conventional neo-natal laryngoscopes results in a guiding channel for intubation which is far from satisfactory. This cramped guiding channel, combined with the extreme difficulty in delivering light to the desired area, makes intubation of neonates a very difficult process. In anything but highly experienced hands it is often impossible to achieve.

The blades which are currently available are unsuitable for small pre-term babies, most makes being too large for infants of less than 1200 grammes (compared to babies as small as 400 grammes which are now viable thanks to developments in obstetrics and neo-natal medicine). Vision of the larynx is obscured and the danger of severe soft tissue trauma is very great.

A third main problem associated with current laryngoscopes is that the metal blades thereof should be sterilised after each examination. A proper regime of sterilisation is time-consuming, inconvenient and quite costly. A cheap, disposable laryngoscope blade would clearly be of great value in both the time and the money that would be saved.

Attempts have been made to overcome some of the problems outlined above. In particular, attempts have been made to produce laryngoscope blades which are less likely to cause damage to the soft tissue of neonates.

One blade which has been employed is a metal blade coated with PTFE (polytetrafluoroethylene). Another attempt was made to develop a blade formed entirely from plastics material. However, neither of these blades was satisfactory. In particular, the light source is still delivered a relatively long distance from the tip of the blade.

It is therefore an object of the present invention to provide improved light-conducting blades for the examination of bodily cavities of human and non-human animals. In particular, it is an object of the invention to provide a light-conducting laryngoscope blade, particularly for use with neonates, which does not have the disadvantages noted above.

According to the present invention there is provided a light-conducting blade for the examination of bodily cavities of humans and non-human animals, said blade having a proximal and a distal end, a means for receiving a light source being provided at the proximal end, the light being delivered at the distal end of the blade, the blade being formed from a suitable material which is shaped such that light can be carried from the light source to the distal end of the blade by total internal reflection of the light through the body of the blade.

It will be readily appreciated that delivery of light through the body of the blade by total internal reflection overcomes a number of the problems referred to above. The overall dimensions of the blade can be reduced relative to conventional blades while increasing the ease with which the light is delivered to exactly the point in the cavity to be examined which is desired by the operator. This means that light can be delivered very accurately without the need for difficult manipulation, reducing the chances of soft tissue damage.

Typically, the blade will be formed from a clear plastics material. In a particularly preferred embodiment, the blades are formed from polymethylmethacrylate (PerspexTM), which can be relatively easily tooled and has excellent properties of total internal reflection. Blades according to the invention which are formed from PerspexTM are reletively cheap to make. Consequently, the blades can be sold in a sterile single-use package, easily affixed to a readily available light source and then dispoed of after one use. It is anticipated that the cost of manufacture of such a blade for a laryngoscope, for example, would be less than the cost of autoclaving current metal laryngoscope blades after each use.

TM Materials such as Perspex are less harsh on soft tissue when used as probes as compared to the prior art metal blades. This is of particular importance in the manufacture of blades for neo-natal laryngoscopes, for example.

The exact shape of the blade and the position at which the light is delivered by total internal reflection will depend upon the nature of the cavity to be examined. It is possible, for example, that it might be desirable to deliver light at a number of points along the length of the examining blade, rather than just at the tip of the blade. Appropriate adjustment of the internally reflecting surfaces would enable such a possibility to be achieved. Consequently, in addition to laryngoscopes, any examining blade for which illumination is required falls within the scope of the present invention, e.g. as replacements for illuminated speculums for use in nasal and gynaecological examinations.

In one embodiment of the invention there is provided a light-conducting laryngoscope blade, said blade having a distal and a proximal end, a means for receiving a light source being provided at the proximal end, the light being delivered at the distal end of the blade, the blade being formed from a plastics material, the internal body of the blade being shaped such that light can be carried from the light source to the distal end of the blade by total internal reflection through the body of the blade and the external surfaces of the blade being complementary to the oral cavity and pharynx of the patient.

Typically, the blade is formed from polymethylmethacrylate. In a preferred embodiment, the body is further provided with a channel to assist the guiding of tubes during intubation. In a particularly preferred embodiment, the main body of the blade, between the proximal and distal ends, is substantially "C" shaped when viewed end-on, and the distal end of the blade curves away from the longitudinal axis of the main body of the blade towards the proximal end of the blade. The "C" shaped section of the main body of the blade enables the mouth to remain open and the tongue compressed out of the field of vision, providing working access to the vocal cords. The curved, light-emitting proximal tip is thus positioned superior to the epiglottis, delivering light at the exact point required by the operator.

Different sizes of blades can be manufactured to suit varying sizes of patient being examined. This is of particular importance for neo-natal laryngoscope blades. The blades of the present invention can be used on the very smallest of neonates without any of the problems described above for existing metal blades.

Furthermore, as the light is delivered through the body of the blade itself by total internal reflection, the effective working space is increased, making intubation easier.

The present invention may be further understood by consideration of the following example, with reference to the accompanying drawings in which: Figure 1 is a laryngoscope blade according to the present invention, viewed from the side; Figure 2 is the same blade viewed along its length from position A; Figure 3 is the same blade viewed along its length from position B; Figure 4 is a perspective view of the blade from below; Figure 5 shows the other side view of the blade shown in Figure 1; and Figure 6 is a schematic internal view of the internal reflecting surfaces of the blade shown in Figures 1 to 5.

A laryngoscope blade of the present invention is TM manufactured from a plastics material, e.g. Perspex and has a cavity 6 at its proximal end which can accept a light source (not shown), e.g. via a moulded thread.

The light source can be any commonly available light-source, e.g. a Welch Allyn otoscope holder model 728. At the end of the receiving cavity 6, perpendicular to the light beam generated by the inserted light source, is a highly polished surface 1 which allows a maximum amount of light from the source to be released into the light carrying section 3 of the body of the blade.

At the proximal end of the light carrying section 3, opposite the highly polished surface 1, is an angled reflecting surface 2. The angle of the reflecting surface is such that the light from the light source is totally internally reflected through the light carrying section of the blade 3. The angle of the reflceting surface 2 is of great importance, and will vary depending upon the refractive index of the material and its resulting critical angle, e.g. the refractive index of perspex is approximately 1. 5 and the critical angle is 42g. Angle F (see Figure 6) should be greater than the critical angle plus 90', i.e. greater than 132-.

At the distal end of the blade is a curved tip 4.

When the blade is attached to a light source, and then placed in the oral cavity, the curved upper section 5 of the blade holds the oral cavity open and compresses the tongue, placing the curved tip 4 superior to the epiglottis. The light carried through the light-conducting section of the body 3 is released through the curved tip 4. A ledge 7 is provided at the tip 4 which spreads out the light, illuminating the pharynx. Thus, light is carried by total internal reflection within the body of the blade direct to the vocal chords, simultaneously illuminating the pharynx.

Viewed along the longitudinal axis of the blade from the curved distal end 4, the relatively large working area offered by the "C" shaped body 5 can be appreciated.

It will be appreciated that the above example is not intended in any way to be limiting, and is merely illustrative, rather than descriptive, of the present invention.

Claims (6)

1. A light conducting device, such as a laryngoscope, comprising a light-conducting blade, said blade having a distal and proximal end, a light source being provided at the proximal end, the light being delivered from a light source at the distal end of the blade, by internal reflection through the body of the blade, wherein the blade comprises a channel which can assist in guiding tubes during intubation of a body cavity under examination.

2. A device according to Claim 1, provided with a curved upper section of the blade which defines one side of the channel.

3. A device according to claim 2 in which the upper section forms a channel which is C-shaped in cross section.

4. A device according to any of Claims 1 to 3 sized for small pre-term babies and neonates.

5. A device as claimed in any of Claims 1 to 4 substantially as herein described.

6. A light-conducting device which can act as a guide intubation of a body cavity substantially as described herein, with reference to the accompanying drawings.