Patent Publication Number: US-7214184-B2

Title: Laryngoscope

Description:
FIELD OF THE INVENTION 
     The present invention relates to a laryngoscope, and in particular a laryngoscope which includes a deployable mirror. 
     BACKGROUND TO THE INVENTION 
     Intubation is a common requirement for anaesthesia, and a laryngoscope is a commonly used instrument for visualizing the larynx to allow the introduction of an endotracheal (ET) tube. The view obtained at laryngoscopy is normally graded on a 1–4 scale, depending on to what extent the view is obscured. Grades 1 and 2 usually provide little difficulty with intubation. However a grade 3 larynx can present considerable difficulty, often requiring special techniques such as blind insertion of the ET tube. A grade 4 larynx is often impossible to intubate using a standard laryngoscope and normally requires the use of more specialized equipment such as fiberoptic equipment. There are four main anatomical factors that contribute to confound the view of the larynx, namely, forward displacement of the larynx, forward or prominent upper teeth, backward displacement of the tongue and poor mouth opening. Another major factor that contributes to confound the view is the inability to achieve what is commonly known as the Magill position of neck flexion and head extension due to either cervical spine instability or pathological disease such as rheumatoid conditions or ankylosing spondylitis. 
     In its basic form, a laryngoscope includes a handle with a slightly curved or straight plate, commonly known as a blade, extending substantially perpendicularly from the handle. The Macintosh laryngoscope, which normally has a slightly curved blade, is an example of such a laryngoscope, In use, the blade is inserted into the patient&#39;s mouth until its tip is located at the base of the patient&#39;s tongue, Normally the tip of the blade is positioned between the base of the person&#39;s tongue and the epiglottis such that, by lifting the laryngoscope anteriorly, the tongue and epiglottis are moved allowing a clearer view of the trachea. A user will generally look for the larynx (vocal cords) which gives, an exact indication of the position in which to place the breathing tube. 
     The use of a curved Macintosh blade laryngoscope in the context of a Grade 3 or 4 larynx may necessitate a forward and upward levering movement. In such situations the patient&#39;s teeth may inadvertently be used as a fulcrum and persistent attempts to elevate the epiglottis frequently results in damage to the upper teeth. In an attempt to overcome this problem, a levering laryngoscope, commonly known as the McCoy laryngoscope, was created. The McCoy laryngoscope has a pivotable tip at the end of the blade, the tip being operable by a lever on the handle of the laryngoscope. When the handle is depressed, the tip pivots to pull the epiglottis away from the mouth of the larynx. The McCoy laryngoscope helps to improve the view of the larynx and, because the fulcrum point is at the distal end of the blade, decreases the likelihood of the patient&#39;s teeth being damaged. 
     It is also known to provide the blade with a deployable mirror which, during use, allows the user to view the larynx more clearly. U.S. Pat. No. 6,135,948 (Lee) describes an example of such a laryngoscope. However, the Lee Laryngoscope is considered to be awkward to use. 
     Despite the devices described above, intubation remains difficult in many cases. It would be desirable, therefore, to provide an improved laryngoscope, particularly since prolonged attempts at laryngoscopy often result in injury, most commonly vocal cord haematoma and mucosal lacerations. 
     SUMMARY OF THE INVENTION 
     A first aspect of the present invention provides a laryngoscope comprising a blade; a deployable mirror; and an operating mechanism, the operating mechanism being operatively associated with the mirror for the deployment thereof, wherein the mirror is pivotable with respect to the blade, the association of the operating mechanism and the mirror being such that an initial operation of the operating mechanism causes the mirror to be, deployed, and further operation of the operating mechanism causes the mirror to be pivoted with respect to the blade. 
     Preferably, the mirror is pivotably mounted on a deployment assembly, the deployment assembly being pivotably mounted on the blade, the arrangement being such that said initial operation of the operating mechanism causes the deployment assembly to be pivoted with respect to the blade, and said further operation of the operating mechanism causes the mirror to be pivoted with respect to the deployment assembly, 
     More preferably, the deployment assembly comprises a deployment arm coupled to a secondary arm so as to permit relative movement between the deployment arm and secondary arm, the mirror being coupled to both the deployment arm and the secondary arm so that relative movement thereof causes the mirror to pivot. 
     Further preferably, the coupling of the deployment arm and the secondary arm includes a spring assembly biased to maintain the deployment arm and the secondary arm in a first position relative to one another, the arrangement being such that, during said initial operation of the operating mechanism, the spring assembly maintains the deployment arm and the secondary arm in the first position, and that, during said further operation of the operating mechanism, a portion of the deployment arm abuts against the blade so that the action of the operating mechanism on the deployment assembly overcomes the bias of the spring mechanism to cause relative movement of the deployment arm and the secondary arm. 
     Preferably, the spring assembly comprises a pin slidably located within a slot, and a spring arranged to act on the pin to maintain the pin in the first position within the slot. 
     Preferably, the operating mechanism comprises a lever, the lever being pivotable with respect to the blade. 
     Preferably, the blade extends, during use, substantially perpendicularly from a handle. More preferably, the blade is detachably mountable on the handle. 
     In the preferred embodiment, the lever is spring biased in a direction generally away from the handle and wherein said initial and further operation or the lever involve movement of the lever in a direction generally towards the handle. 
     Preferably, the mirror is actuatable between a non-deployed state, in which the mirror is located against or adjacent the blade, and at least one deployed state in which the mirror is spaced-apart from the blade with its reflective surface facing generally towards the blade. More preferably, the lever is arranged to adopt a rest state in the absence of external forces, in which rest state the lever is spaced-apart from the handle, the arrangement being such that, when the lever adopts the rest state, the mirror adopts the non-deployed state, initial movement of the lever from the rest state towards the handle causing the mirror to be deployed, and further movement of the lever towards the handle causes the mirror to be pivoted. 
     In the preferred embodiment, the blade comprises a pivotable tip, the operating mechanism being operatively associated with the tip to cause the tip to pivot with respect to the blade. Preferably, the operating mechanism is arranged to cause the tip to pivot during said initial operation and said further operation. 
     Preferably, the blade carries a light source arranged to irradiate the mirror when deployed. 
     A second aspect of the invention provides a blade for a laryngoscope, the blade comprising a deployable mirror; and an operating mechanism, the operating mechanism being operatively associated with the mirror for the deployment thereof, wherein the mirror is pivotable with respect to the blade, the association of the operating mechanism and the mirror being such that an initial operation of the operating mechanism causes the mirror to be deployed, and further operation of the operating mechanism causes the mirror to be pivoted with respect to the blade. 
     Other advantageous aspects and features of the invention will became apparent to those ordinarily skilled in the art upon review of the following description of a specific embodiment of the invention and with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A specific embodiment of the invention is now described, by way of example, and with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a preferred embodiment of a laryngoscope according to the present invention, with a mirror shown in a non-deployed state; 
         FIG. 2  is a side elevation of the laryngoscope of  FIG. 1 , with the mirror shown in a deployed state; 
         FIG. 3  is an exploded perspective view of the laryngoscope of  FIG. 1 ; 
         FIG. 4  is a side view of the laryngoscope of  FIG. 1  with the mirror in a deployed state; 
         FIG. 5  is a side view of the laryngoscope of  FIG. 1 , similar to that shown in  FIG. 4 , wherein the mirror is in a different deployed state; 
         FIG. 6  is a perspective view of part of a handle forming part of the laryngoscope of  FIG. 1 ; and 
         FIG. 7  shows a perspective view of part of the blade of the laryngoscope, in particular showing a coupling which permits the blade to be secured to the handle. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring now to the accompanying drawings, there is shown, generally indicated as  10 , a preferred embodiment of a laryngoscope according to the invention The laryngoscope  10  comprises a plate, or blade  12 , and a handle  14 . The blade  12  is mountable on the handle  14  such that the blade  12  extends substantially perpendicularly therefrom. The blade  12  carries a mirror  30  which may be deployed and-pivoted relative to the blade  12 , as will he described in detail hereinafter. 
     The blade  12  comprises a base plate  22  and a side flange or wall  24  extending substantially perpendicularly from the base plate  22 . The blade  12  has a proximal end  13  at which, in use, the blade  12  is connected to the handle  14 , and a distal end, or tip  18 , which, in use, is inserted into a patient&#39;s mouth (not shown) and used in normal manner to facilitate visualization of the trachea or larynx. Preferably, the blade  12  is slightly curved in a manner similar to that of the Macintosh-type laryngoscope. At its proximal end  13 , the blade  12  is provided with a mount  78  which permits the blade  12  to be releasably secured to the handle  141 , by means of a corresponding interengagable coupling  70  located at the top of the handle  14 . Preferably, a light source, conveniently in the form of a light bulb  36 , is provided on the blade  12 . Conveniently, the light  36  is mounted on the side wall  24  at a forward position on the blade  12 , the light  36  being arranged, in use, to irradiate thee region around the tip  18  of the blade  12 . The handle  14  is conveniently arranged to house batteries  90  in order to supply power to the light  36 , although any other suitable power source may be employed. The configuration and operation of the light  36  will be described in greater detail hereinafter. 
     In the preferred embodiment, the tip  18  is pivotally mounted on the blade  12 , conveniently via a link  20 . As is best illustrated in  FIGS. 4 and 5 , the tip  18  is pivotable in the general direction of the handle  14  (as indicated by arrow A in  FIG. 5 ) in order to draw the epiglottis (not shown) away from the laryngeal inlet of the patient, so as to provide a clearer view of the patient&#39;s larynx. In order to effect this pivoting motion, the laryngoscope  10  is provided with an operating mechanism in the form of a lover  16  which is pivotally mounted on the blade  12 . In the illustrated embodiment, and in particular from  FIG. 2 , it can be seen that the lever  16  is mounted to the side wall  24  of the blade  12 . To this end the lever  16  is connected to a bushing  66 , which is seated on and is rotatable about a boss  68  which is provided on the blade  12 . The bushing  66  is coupled to the boss  68  by a spring (not shown), the spring being biased to urge the bushing  66  to rotate in a clockwise direction (as viewed in  FIG. 2 ) about the boss  68 . Thus, the bushing  66 , the boss  68  and the spring together serve as a spring mechanism biased to urge the lever  16  away from the handle  14 .  FIG. 1  shows that lever  16  in a rest state which it adopts under the action of the spring mechanism and in the absence of any external forces, such as a user&#39;s grip, being exerted. 
     The bushing  66  is provided with a first lug  62 , to which is pivotably mounted one end of a rigid strut or rod  60 . The other end of the rod  60  is pivotably connected to the tip  18  of the blade  12 . The arrangement is such that depression or the lever  16  towards the handle  14  (in the direction indicated by arrow B in  FIG. 5 ), causes the first lug  62  to move generally towards the tip  18  and this, in turn, actuates the rod  60  outwardly towards the tip  18 . As the rod  60  is actuated outwardly, it causes the tip  18  to pivot with respect to the blade  12  in a direction generally towards the handle, i.e. clockwise as viewed in  FIG. 2 . It will be understood that the amount by which the lever  16  is depressed determines that amount by which the tip  18  is pivoted. When the lever  16  is released it will, under the action of the spring mechanism, return to its rest state thereby drawing the tip  18  back into normal alignment with the blade  12  as is shown in  FIG. 1 . 
     The mirror  30  may be actuated between a non-deployed state (as shown in  FIG. 1 ) and at least one deployed state.  FIGS. 2 to 5  illustrate the mirror  30  in various states of deployment. 
     In the preferred embodiment, the non-deployed state corresponds with the lever  16  adopting its rest state, as shown in  FIG. 1 . In this state, the mirror  30  rests against the base plate  22  of the blade  12 , with the reflective surface of the mirror  30  facing towards the base plate  22 . In this state, the overall size of the blade  12  (including the mirror  30 ) is minimized and this facilitates insertion of the blade  12  into a patient&#39;s mouth/throat (not shown). As can best be seen from  FIG. 1  and  FIG. 3 , it is preferred that that at least the portion of the base plate  22  (including the tip  18 ) that receives the mirror  30  in the non-deployed state is at least as wide as the mirror  30  such that, when in the non-deployed state, the underside (i.e. reflective surface) of the mirror  30  is fully occluded by the base plate  22 /tip  18 . This helps to prevent the reflective surface of the mirror  30  from becoming smudged or otherwise obscured during insertion of the blade  12  into a patient&#39;s mouth. In addition, the mirror receiving portion of the tip  18  and the base plate  22  may be recessed by approximately the depth of the mirror  30  so that the mirror  30 , when in the non-deployed state, sits within the recess (not shown) such that the exposed face of the mirror  30  lies flush with the base plate  22 . 
     Once the blade  12  is inserted into a patient&#39;s mouth, it is necessary to deploy the mirror  30  in order to provide a clear view of the patient&#39;s larynx. To this end, the mirror  30  is carried by a deployment assembly which comprises a deploying arm  26  and a secondary arm  28 . The deploying arm  26  is pivotably mounted on the blade  12 . In the illustrated embodiment, the deploying arm  26  is pivotably mounted on the side wall  24  via a first pivot  50 , and carries a spring  46  which is secured to the deploying arm  26  around an anchor  48 . The secondary arm  28  is coupled to the deploying arm  26  by means of a main slot  42  in which there is located a main pin  44 , and advantageously also a guide slot  52  in which there is located a guide pin  54 . The arrangement is such that the deploying arm  26  and the secondary arm  28  are capable of sliding movement relative to one another in a direction generally parallel with their longitudinal axes, the extent of the sliding movement being limited by the relative dimensions of the slots  42 ,  52  and pins  44 ,  54 . In the illustrated embodiment, the main slot  42  and the guide slot  52  are formed in the deployment arm  26  while the main and guide pins  44 ,  54  are provided on the secondary arm  26 . It will be understood however that in an alternative embodiment the slots/pins may be provided on either arm  26 ,  28 . 
     The spring  46  engages with and acts upon the main pin  44  so as to urge the main pin  44  towards one end of the main slot  42 . In the illustrated embodiment, the spring  46  urges the main pin  44  towards the mirror-end of the main slot  42 , namely the end nearest the mirror  30 . The arrangement is such that, when the mirror  30  is in the non-deployed state, the spring  46  holds the main pin  44  in a first position in the slot. Conveniently, in the first position, the main pin  44  is held in engagement with the mirror-end of the slot  42  as shown in  FIG. 1 . Hence, the spring  46 , the main slot  42  and the main pin  44  together form a spring assembly biased to maintain the deployment arm  24  and the secondary arm  26  in the first position. The guides pin  54  adopts a corresponding first position within the guide slot  52 . 
     In order to actuate the deployment assembly, a second lug  64  is provided on the bushing  66 , generally oppositely disposed on the bushing  66  with respect to the first lug  62 . Thus, when the lever  16  is depressed towards the handle  14 , the second lug  64  moves generally away from the tip  18  of the blade  18  (anti-clockwise as viewed in  FIG. 2 ). A tie  58 , shown in the form of a second rigid rod, has one end pivotably connected to the second lug  64 . The other end of the tie  58  is connected to the deployment assembly. In the preferred embodiment, the tie  58  is connected directly to the second arm  28  and an access slot  41  is formed in the side wall  24  of the blade  12  through which the tie  58  passes. 
     The arrangement is such that, initial depression of the lever  16  from its rest state draws the tie  58  rearwardly (i.e. away from the tip  18 ), thereby exerting a rearward force on the secondary arm  28 . Initially, the spring  46  acts to prevent relative sliding movement between the secondary arm  28  and the deploying arm  26 . Hence, the force applied to the secondary arm  28  by the tie  58  causes the deploying arm  26  (and therefore also the secondary arm  28 ) to pivot about the first pivot  50  (anti-clockwise as seen from  FIG. 2 ), thereby drawing the mirror  30  upwardly away from the base plate  22  into a deployed state. However, as can be seen from  FIG. 1 , the deploying arm  26  is provided with a shoulder  34  which, after limited rotation of the deploying arm  26  about pivot  50 , abuts against the base plate  22 . At this point, the deploying arm  26  cannot rotate any further in the direction away from the blade  12 . Thus, the force exerted on the secondary arm by further rearward movement of the tie  58 , due to further depression of the lever  16 , overcomes the force of the spring  46  which is no longer able to hold the main pin  44  in its first position. As can best be appreciated from  FIG. 4 , the main pin  44  is thus drawn rearwardly within the main slot  42  (i.e. away from the mirror-end), against the action of the spring  46 , resulting in relative sliding movement between the deploying arm  26  and the secondary arm  28 . The laryngoscope  10  is arranged to translate this relative movement into pivoting movement of the mirror  30  relative to the deploying arm  26 , as is described below. 
     The mirror  30  is pivotably mounted on the deployment assembly. To this end, the mirror  30  is; fixed to a mounting bracket  32  which is pivotably mounted on the deploying arm  26  at a second pivot  55 . The secondary arm  28  is pivotably connected to the mounting bracket  32  at a third pivot  56  which in eccentrically located relative to the second pivot  55 , as may best be seen in.  FIGS. 4 and 5 . The arrangement is such that, as the secondary arm  28  is drawn rearwardly (i.e. away from the mirror  30 ) with respect to the deploying arm  26 , the mounting bracket  32  will be caused to pivot about the second pivot  55  (in an anti-clockwise direction as viewed in  FIGS. 4 and 5 ), thereby imparting a corresponding pivoting motion to the mirror  30  (as, indicated by arrow C in  FIG. 5 ). It will be apparent that the mounting bracket  32  could be formed integrally with the mirror  30 , thereby obviating the need for the two components to be manufactured separately and subsequently secured together. 
     In  FIG. 3 , the mirror  30  is shown in a deployed but non-pivoted position with respect to the deployment arm  26  and this corresponds to the situation where the main pin  44  (and therefore the guide pin  54 ) are held in the first position, i.e. no relative sliding movement of the deployment arm  26  and the secondary arm  28  has taken place. In  FIG. 4 , the main pin  44  is shown drawn partially back along the length of the main slot  42 , and thus the mirror  30  in pivoted, or angularly displaced, with respect to the deploying arm  26  by a corresponding amount. In  FIG. 5 , the lever  16  has been sufficiently depressed that the main pin  44  is drawn fully back within the main slot  42 , and thus the mirror  30  is in its fully pivoted, or moot angularly displaced, state with respect to the deploying arm  26 . 
     It will be appreciated that, depending on the amount by which the lever  16  is depressed, the mirror  30  may adopt a plurality of different deployed states and that, when deployed, the mirror  30  may further adopt a plurality of different pivoted states with respect to the deployment arm  26 , Hence, during use, a user is able to adjust the position and orientation of the mirror  30  until an optimal view of the larynx is obtained. 
     It will be apparent that, as both the lever  16  and the main pin  44  are spring biased, release of the lever  16  will result in the mirror  30  returning to its non-pivoted state, and subsequently in pivoting of the deploying arm  26  and the secondary arm  28  back towards the base plate  22 , so as to return the mirror  30  to its non-deployed state. 
     The base plate  22  is provided with a recess  57  arranged to house the mounting bracket  32  when the mirror  30  is in the non-deployed state. Although a suitably shaped aperture (not shown) could have alternatively been provided in the base plate  22  for receiving the mounting bracket  32 , the recess  57  ensures that, during insertion of the blade  12  into a patient&#39;s mouth, the mirror  30  is not contacted by saliva or the live, which may subsequently impair the view provided by the mirror  30 . Further, by surrounding the mounting bracket  32  the recess  57  protects the patient&#39;s mouth and tongue from damage which may otherwise be caused during insertion of the blade  12 . 
     In addition, the side wall  24  may be laterally recessed along at least part of the length thereof adjacent the deploying arm  26  and the secondary arm  28 , such that the outwardly facing surface of the deploying arm  26  lies substantially flush with the remainder of the side wall  24 . It will be appreciated that such an arrangement would provide a clearer view, in use, down the length or the blade  12 . 
     The light  36  is arranged to irradiate the mirror  30  when deployed. The light  36  may be of any suitable form, for example an LED, a tungsten filament bulb, or a fibre optic bundle. In order to supply the light  36  with power, a conduit  40  is connected to the light  36 , and extends rearwardly to the coupling  70 , as can be seen in  FIG. 2  and  FIG. 7 . The coupling  70 , during use, is electrically connected to the handle  14  so as to enable the passage of currant from the batteries  90  in the handle  14  to the conduit  40 , a preferred arrangement for which is described below. 
     The batteries  90  are inserted, by removal of a cap  88 , into the handle  14 . The coupling  70  at the top of the handle  14 ,  45  shown in  FIG. 6 , includes a first contact  86  projecting therefrom. When the mount  78  is secured to the coupling  70 , the first contact  86  abuts a second contact  76 , which is electrically connected to the conduit  40 . In order to releasably secure the blade  12  to the handle  14 , the coupling  70  includes a mouth  72  which engages a bar  80  of the mount  78 . The coupling  70  further includes a number of conventional detent balls  74  which engage corresponding indents  84  in a pair of walls  82  of the mount  78 . The coupling  70  may thus be clipped and unclipped to the mount  78 , thereby supplying power to the light  36  when the handle  14  is secured to the blade  12 . 
     With the laryngoscope  10 , the deployment of the mirror  30 , the pivoting of the mirror  30  and the pivoting of the tip  18  can all be performed by operation of a single lever  16 . Deployment of the mirror  30  occurs simultaneously with pivoting of the tip  18  as the lever  16  undergoes initial depression from its rest state. In the preferred embodiment, the arrangement is such that the lever  16  continues to cause the tip  18  to pivot as the lever  16  is further depressed, i.e. the tip  18  pivots simultaneously with the pivoting of the mirror  30 . It is found that during said further depression of the lever  16  the user can fine tune the orientation of the mirror  30  and tip  18  so as to optimize his view of the trachea/larynx. Hence, the user has full operational control over the laryngoscope  10  using only one lever  16 . The laryngoscope  10  may therefore readily be operated using only one hand. 
     Moreover, the lever  16  may be operated by exerting a simple squeezing action on the lever  16  and does not require any dextrous finger movements. 
     Further, the provision of a deployable and adjustable mirror allows the larynx to be visualized in difficult intubations without the need to use fiberoptic equipment (which are expensive and require considerable user training). 
     In alternative embodiments (not shown), the lever  16  may be replaced with any other suitable operating mechanism. For example, a cable system may be used wherein one or more cables are connected to the deployment assembly and, when used, the pivotable blade tip, for the actuation thereof. An operating knob may be provided on the cable to allow a user to push or pull the cable (s) back and forth thereby operating the mirror and tip in a similar manner to that described above. 
     The foregoing description is of a preferred embodiment of the invention and a skilled person will readily understand that many of the specific component parts described above may be replaced with technically equivalent parts while achieving the same technical effect. The present invention is therefore not limited to the embodiment described herein, which may be amended or modified without departing from the scope of the present invention.