Abstract:
A laryngoscope constructed of materials including metal components having very low magnetic susceptibilities is described. The battery powering the laryngoscope lamp is a lithium battery also constructed of materials having low magnetic susceptibilities. The battery further includes a unique terminal configuration that prevents the inadvertent use of other batteries, including non-magnetic batteries, in the laryngoscope. A unique lamp retaining mechanism provides for quick and easy replacement of the lamp.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of application Ser. No. 08/837,339, filed Apr. 11, 1997, now U.S. Pat. No. 6,036,639. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a hand held medical device. More particularly, the present invention relates to a laryngoscope, and still more particularly to a laryngoscope that is constructed of materials having relatively low magnetic susceptibilities. This provides the laryngoscope of the present invention as a useful instrument in the vicinity of a magnetic resonance scanner. 
     2. Prior Art 
     Laryngoscopes generally comprise a detachable blade and a cooperating handle which are connected together in an L-shaped configuration. The handle serves as an enclosure for one or more batteries which energize a light source in the handle. The switch for energizing the light source is usually positioned at the top of the handle immediately adjacent to the light source and is activated by the blade when it is connected to the handle and moved into an operative position. Light from the light source is directed to the light conductor disposed in or on the blade. Light passes through the light conductor to the distal end thereof to illuminate the field of view such as a patient&#39;s mouth and larynx during the examination thereof by medical personnel and during the insertion of an endotracheal tube into the trachea of the lungs to administer anesthetic gases therein. 
     The prior art is replete with various types of metallic laryngoscopes, some of which are capable of illumination. Additionally, U.S. Pat. No. 4,607,623 to Bauman describes a laryngoscope constructed of non-ferrous materials such as ABS with the electrically conductive portions provided by first applying a thin copper layer to the ABS followed by electroless plating and then electrolytically plating another copper layer to form a conductive layer about 0.5 to 2 mils thick. A thin layer of aluminum is subsequentially applied to the copper coating in those areas intended to be reflective. The batteries powering this device are not further described, but may be of a nickel/cadmium type commonly used for such application. Nickel/cadmium batteries are not considered to be relatively nonmagnetic and would not be useful with the laryngoscope of the present invention. 
     U.S. Pat. Nos. 310,004 to Weston; 485,089 to Carhart; 2,282,979 to Murphy; 3,352,715 to Zaromb; 3,673,000 to Ruetschi and 4,318,967 to Ruetschi disclose anti- or non-magnetic materials in cells or batteries. Additionally, U.S. Pat. Nos. 2,864,880 to Kaye; 2,982,807 to Dassow et al.; 4,053,687 to Coiboin et al.; 4,264,688 to Catanzarite; 4,595,641 to Giutino; 5,104,752 to Baughman et al.; 5,149,598 to Sunshine; 5,173,371 to Huhndorff et al.; 5,194,340 Kasako; 5,418,087 to Klein; and 5,443,924 to Spellman relate to batteries having means for assuring that proper battery polarity is established. However, none of these patents describe power sources that are useful with the hand held medical device of the present invention because they either include at least some magnetic components, do not have sufficient energy density for extended use or do not have a terminal configuration similar to that of the present invention. U.S. Pat. No. 4,613,926 to Heitman et al. discloses an illuminating assembly for an MRI scanner. 
     There is needed a lighted laryngoscope that is predominantly constructed of metal so that the instrument is capable of withstanding the abusive treatment conditions which surgical instruments are sometimes subjected to. For this purpose, the laryngoscope of the present invention is constructed largely of metal components. However, with ever increasing use of magnetic resonance scanning to aid medical personnel during pre- and post-clinical and surgical procedures, the metal components must be constructed of materials that have as low a magnetic susceptibility as possible. 
     SUMMARY OF THE INVENTION 
     The laryngoscope of the present invention is constructed of materials including metal components having very low magnetic susceptibilities. Those parts not made of metal are preferably formed of a thermoplastic material, for example an acetal compound such as DELRIN. The battery powering the laryngoscope lamp is also constructed of materials having low magnetic susceptibility. Lithium batteries are preferred, and all components such as the casing, terminal leads, current collectors and collector leads, some of which are typically made of nickel, are constructed of stainless steel nonmagnetic austenitic. The battery further includes a unique terminal configuration that prevents the inadvertent use of other batteries, including non-magnetic batteries, in the laryngoscope. A unique lamp retaining mechanism provides for quick and easy replacement of the lamp. 
     These and other aspects of the present invention will become more apparent to those skilled in the art by reference to the following description and to the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a laryngoscope  10  according to the present invention. 
     FIG. 2 is an exploded view of the laryngoscope handle  12  and head assembly. 
     FIG. 3A is a partial, cross-sectional view of a portion of the handle  12  and the head assembly for the laryngoscope  10 . 
     FIG. 3B is a partial, cross-sectional view of the handle  12  and end cap  50  for the laryngoscope  10 . 
     FIG. 4 is a plan view of the battery  32  for the laryngoscope  10 . 
     FIG. 5 is a side, elevational view of the battery  32 . 
     FIG. 6 is a perspective view of the head  100  for the laryngoscope  10 . 
     FIG. 7 is a perspective, exploded view of the lamp retainer  124  for the laryngoscope  10 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to the drawings, FIGS. 1 to  7  show a laryngoscope  10  having low magnetic susceptibility characteristics according to the present invention and generally comprised of a handle  12 , a detachable blade  14  and an attachment means  16  for detachably securing the blade  14  to the handle  12  in a generally L-shaped configuration. The instrument is utilized to depress a patient&#39;s larynx during an examination thereof or during the insertion of an endotracheal tube. The blade is of stainless steel or a fiberglass composite commercially available from Heine under the trademark SANALON. 
     With particular reference to FIGS. 2,  3 A, and  3 B, the handle  12  is a cylindrically-shaped tube comprising an intermediate section  18  meeting at a step  20  with a proximal section  22  having internal threads  24 , and the intermediate section  18  meeting at a chamfer  26  with a distal section  28 . The outer surface of the handle  12  is provided with raised, knurled ridges  30  (FIG. 1) to aid in gripping the laryngoscope  10 . The handle  12  is preferably constructed of chrome plated brass. 
     A battery  32  (FIGS. 2,  3 A,  3 B,  4  and  5 ) is housed inside the intermediate handle section  18  for providing power to a lamp means as an assembly  34 , which will be described in detail hereinafter. The battery  32  is constructed of materials having relatively low magnetic susceptibility with a unique terminal configuration according to the present invention. The battery  32  is preferably an alkali metal battery and more preferably an alkali metal/liquid catholyte battery. A most preferred chemistry utilizes the lithium/thionyl chloride-bromine chloride (Li/BCX) couple. The battery casing adjacent to the distal handle section  28  is insulated to prevent electrical contact in the conventional manner. 
     As shown in FIGS. 3A,  4  and  5 , the opposite end of the battery  32  includes a negative contact ring  36  that is permanently attached to the battery case to provide one terminal for the battery. The central, positive terminal  38  is recessed and insulated by material  40  around its perimeter to prevent accidental shortening. A non-magnetic fuse  42  prevents inadvertent run-away electrochemical reaction while a thermoplastic insulator plate  44  supported on a ledge of the insulated material  40  protects the positive terminal  38  and fuse  42 . A central opening  46  in plate  44  provides for access to the positive terminal  38 . To provide the battery  32  having a relatively low magnetic susceptibility, all external and internal electrical components such as the casing, the terminals  36 , 38 , the current collectors and the contact leads are of stainless steel. 
     The unique terminal configuration prevents the inadvertent loading and discharge of batteries into the handle  12  not intended for use with the laryngoscope  10 . Such inadvertent battery use could have detrimental affects on the laryngoscope&#39;s low magnetic susceptibility characteristics. 
     The battery  32  is secured inside the handle  12  by a cap spring  48 , preferably of silver plated beryllium copper, that biases between the battery and an end cap  50  snug-fitted into the distal handle section  28  extending part way into the intermediate handle section  18 . The end cap  50  is of a non-magnetic material, such as an acetal thermoplastic material with an enlarged head  52  that abuts the distal end of handle  12 . A groove  54  formed between the cap head  52  and an annular protrusion  56  of the cap receives an O-ring  58  of a flexible elastomeric material for sealing the cap  50  in the distal section  28  of the handle  12  in a fluid tight engagement. 
     As shown in FIGS. 2 and 3A, a battery retainer assembly is threaded into the proximal handle section  22  and includes a battery retainer  60 , preferably of an acetal thermoplastic material, that threads into the handle  12  to capture a battery pin  62 , a battery spring  64 , a tube disk  66  and a pair of spring contacts  68  therein. The battery pin  62  is preferably of gold plated brass, the battery spring  64  is preferably of silver plated beryllium copper, the tube disk  66  is of an acetal thermoplastic material and the spring contacts  68  are of silver plated beryllium copper. 
     The battery retainer  60  comprises a threaded portion  70  sized to threadingly mate with the internal threads  24  of the proximal handle section  22 . The threaded portion  70  of the battery retainer  60  meets a cylindrically-shaped portion  72  that extends to a chamfer  74  ending at an end face  76 . The battery retainer  60  has a first, cylindrically-shaped bore  78  that meets at an internal shoulder  80  with a second, lesser diameter cylindrically-shaped bore  82  extending to the end face  76 . A pair of diametrically opposed openings  84  are provided through the thickness of the threaded portion  70 . The battery retainer  60  receives the battery pin  62  having a cylindrically-shaped body  86  provided with an annular protrusion  88  adjacent to a proximal end  90  thereof. 
     The internal threads  24  at the proximal handle section  22  terminate at an internal shoulder  92 . Shoulder  92  supports the tube disk  66  having a central opening  94 . The tube disk  66  also includes a pair of opposed channels  96  (shown in dashed lines in FIG. 2) that communicate between the outer edge thereof and diametrically opposed portions of the opening  94 . The tube disk  66  supports the pair of spring contacts  68 , each having a leg disposed in one of the disk channels  96  with a contact portion  98  of the springs extending from the opposite face of the tube disk  66 . 
     As shown in FIG. 3A, with the tube disk  66  supported on the internal shoulder  92 , the spring contacts  68  are captured between the shoulder  92  and the disk  66  with the contact portions  98  contacting the annular, negative terminal  36  of battery  32 . The tube disk  66  and spring contacts  68  are secured in this position by the battery retainer  60  threaded into the proximal handle section  22 . The battery retainer  60  further captures the battery pin  62  between itself and the tube disk  66  with the proximal end side of the annular protrusion  88  abutted against the internal shoulder  80  of the battery retainer by the battery spring  64  surrounding the body  86  of the battery pin  62  and biasing between the tube disk  66  and the opposite side of the annular protrusion  88 . The pair of diametrically opposed openings  84  in the battery retainer  60  are provided to receive a tool (not shown) such as a spanner wrench for tightening the battery retainer  60 , battery pin  62 , battery spring  64 , tube disk  66  and spring contacts  68  into position. The battery retainer assembly together with the battery  32  loaded into the handle  12  and secured therein by the cap spring  48  and end cap  50  form the portion of the laryngoscope  10  of the present invention generally referred to as the battery pack assembly. 
     After the battery retainer assembly is threaded into the proximal handle section  22 , the proximal section  22  threadingly receives a head  100 . As shown in FIGS. 2,  3 A,  4  and  6 , the head  100  includes a cap portion  102  having external threads  104  that threadingly mate with the internal threads  24  at the proximal handle section  22 , and the attachment means  16  for attaching the blade  14  to the handle  12 . The head  100  is preferably constructed of chrome plated brass. 
     The head  100  further comprises an internal passage  106  extending from its threaded end through the cap portion  102  to the attachment means  16 . At the threaded end, the bore  106  has a beveled portion  108  tapering inwardly toward a first cylindrical portion  110  that meets with an internally threaded portion  112  at step  114 . The internal threaded portion  112  of head  100  meets with a second cylindrical portion  116  at step  118  which extends to a shoulder  120  that meets with an opening  122  (shown in dashed lines in FIG. 1) leading into the blade attachment means  16 . 
     To provide illumination to a fiber optic blade light conductor  123  (shown in dashed lines in FIG.  1 ), the lamp assembly  34  is mounted in the internal bore  106  of head  100 . The lamp assembly  34  includes a lamp retainer  124  (FIGS. 2,  3 A and  7 ) having an interior cylindrically-shaped bore  126  extending to a shoulder  128  that meets with an outwardly beveled, reflector portion  130 . The lamp retainer  124  is preferably constructed of stainless steel. A lamp  132  is received inside the bore  126  with the lamp casing  134  abutted against the shoulder  128  so that the lamp  132  is disposed in a reflective relationship with the reflector portion  130  of lamp retainer  124 . A lamp  132  useful with the laryngoscope  10  of the present invention is commercially available from Boehm under model no. X02.88.044. 
     Lamp retainer  124  is provided with an annular enlarged portion  136  opposite a portion of the interior cylindrically-shaped bore  126  and adjacent to shoulder  128 . An annular groove  138  in the enlarged portion  136  intersects an opening  140  communicating with the interior bore  126 . A stainless steel detent in the shape of a ball  142  serving as a lamp holder is disposed inside the opening  140 . Opening  140  is somewhat less in diameter than that of the detent  142  so that a portion of the detent protrudes into the bore  126  contacting the lamp casing  134  of lamp  132  received inside the bore  126 . The detent  142  is retained in this position by a beryllium copper spring clip  144  seated in groove  146  in the annular enlarged portion  136  to thereby removably hold or retain the lamp  132  in the lamp retainer  124 . 
     The lamp retainer  124  is itself secured in the internal bore  106  of head  100  by a lamp retainer ring  148  having exterior threads  150  that threadingly mate with the internal threaded portion  112  of head  100 . The lamp retainer ring  148  is preferably constructed of chrome plated brass and further comprises an internal shoulder  152  meeting with an opening  154  that is only somewhat greater in diameter than the outer cylindrical side wall of the lamp retainer  124 . With the lamp retainer  124  received in the internal bore  106  of head  100 , a head spring  156 , preferably constructed of silver plated beryllium copper and sized to surround the outer side wall of the lamp retainer  124 , biases between the annular enlarged portion  136  of lamp retainer  124  and the shoulder portion  152  of the lamp retainer ring  148  threaded into the head  100 . 
     The lamp  132  is provided with a contact  158  that extends beyond the retainer ring  148  and into the beveled portion  108  of head  100  with the external threads  24  of the cap portion  102  mated to the internal threads  24  at the proximal handle section  22 . In this position, a shoulder  160  intermediate the external threads  104  and an annular step  162  abuts the end of the proximal handle section  22 . An elastomeric O-ring  164  is received in the steps  162 , held tightly between the cap  102  and handle  12 . 
     The blade  14  is attached to the handle  12  in a pivotal manner by the attachment means  16  which includes a base portion  166  of blade  14 , and a pair of opposed side walls  168  and  170  extending from a base plate  172  supported on the cap portion  102  of head  100 . The side walls  168 ,  170  are provided with respective channels  174 ,  176  that extend part way across the length of the side walls from an end thereof. Each side wall  168 ,  170  further includes an opening  178  opposite the terminal end of the channels  174 ,  176 . 
     The base portion  166  of the blade  14  is sized to be received between the side walls  168 ,  170  of head  100 . The base portion  166  also has a through bore (not shown) sized to receive a pin  180 , preferably constructed of stainless steel, and a pair of spring biased detents  182  (one shown in dashed lines in FIG. 1) that are receivable in the respective channels  174 ,  176 . 
     To fix the blade  14  with respect to the handle  12  in the generally L-shaped configuration, the base portion  166  of blade  14  is positioned between the side walls  168 ,  170  of head  100  with the through bore aligned with the openings  178 . The pin  180  is moved through the openings  178  and bore to thereby pivotably attach the blade  14  to the handle  12 . 
     FIG. 3A shows that when the head  100  is threaded onto the proximal handle section  22 , the contact  158  of lamp  132  contacts the proximal end  90  of the battery pin  62 . The opposite, distal end  166  of the battery pin  62  is in a raised position, out of contact with the central, positive terminal  38  of battery  32 . The lamp  132  is energized by pivoting the blade  14  with respect to the handle  12  about the pin  180  until the spring biased detents  182  seat in the opposed channels  174 ,  176  in side walls  168 ,  170 . This movement serves to releasibly lock the blade  14  in the generally L-shaped configuration with respect to the handle  12 . As the blade  14  is so pivoted, the base portion  166  contacts the lamp retainer  124 , moving it and the lamp  132  towards the battery  32  and against the biasing force of head spring  156 . The lamp contact  158  in turn forces the battery pin  62  towards the battery  32  against the biasing force of the battery spring  64  until the distal end  166  of the pin  62  contacts the central, positive terminal  38  of battery  32  (as shown in dashed lines in FIG.  3 A). The electrical circuit is completed through the annular, negative contact ring  36 , the spring contacts  68 , the handle  12 , the head  100 , lamp retainer ring  148  and the detent  142  contacting the lamp casing  134 . With the lamp  132  energized, light is directed to the blade light conductor  123  which transmits the light to the end of the blade  14 . When the laryngoscope  10  is utilized during a medical examination or during the insertion of an endotracheal tube, the conductor  123  helps to illuminate the zone of interest to thereby aid the physician. 
     When the blade  14  is pivoted about pin  180  in the opposite direction to break the L-shaped configuration, the head spring  156  biases the lamp retainer  124  and lamp  132  away from the battery  32  and the battery spring  64  biases the battery pin  62  out of contact with the central, positive battery terminal  38 . 
     In addition to serving as a portion of the electrical contact path for energizing the lamp  132 , the lamp assembly  34  including the lamp retainer  126 , detent  142  and spring clip  144  provide a structure for quickly and easily replacing the lamp  132  should it burn out or otherwise malfunction. To change the lamp  132 , the head  100  is unscrewed from the proximal handle section  22  and the lamp retainer ring  150  is unthreaded from the head  100 . This releases the lamp assembly  34  from the head  100  and the lamp  132  is easily moved out of the bore  126  in the lamp retainer  124 , releasing from contact with the spring clip  144  biased detent  142 . A new lamp  132  is then replaced inside the lamp retainer  124  and the lamp assembly  34  including spring  156  and lamp retainer ring  150  are then re-assembled inside the head  100  and the head is screwed onto the handle  12 . 
     In accordance with the stated low magnetic susceptibility characteristics of the laryngoscope of the present invention, Table 1 lists the magnetic susceptibilities of the various materials used to construct the laryngoscope along with selected other materials. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                 Atomic or 
                   
               
               
                   
                   
                 Density 
                 Molecular 
                 Susceptibility 
               
               
                   
                 Material 
                 (g/cc) 
                 Weight 
                 (× 10 6 ) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Carbon 
                 2.26 
                 12.011 
                 −218 
               
               
                   
                 (polycrystalline 
               
               
                   
                 graphite) 
               
               
                   
                 Gold 
                 19.32 
                 196.97 
                 −34 
               
               
                   
                 Beryllium 
                 1.85 
                 9.012 
                 −24 
               
               
                   
                 Silver 
                 10.50 
                 107.87 
                 −24 
               
               
                   
                 Carbon (diamond) 
                 3.513 
                 12.011 
                 −21.8 
               
               
                   
                 Zinc 
                 7.13 
                 65.39 
                 −15.7 
               
               
                   
                 Copper 
                 8.92 
                 63.546 
                 −9.63 
               
               
                   
                 Water (37° C.) 
                 1.00 
                 18.015 
                 −9.03 
               
               
                   
                 Human Soft 
                 ˜1.00- 
                 — 
                 ˜(−11.0 to 
               
               
                   
                 Tissues 
                 1.05 
                   
                 −7.0) 
               
               
                   
                 Air (NTP) 
                 0.00129 
                 28.97 
                 +0.36 
               
               
                   
                 Stainless Steel 
                 8.0 
                 — 
                 3520-6700 
               
               
                   
                 (nonmagnetic, 
               
               
                   
                 austenitic) 
               
               
                   
                 Chromium 
                 7.19 
                 51.996 
                 320 
               
               
                   
                   
               
             
          
         
       
     
     It is known that brass is an alloy of copper and zinc. 
     In contrast, Table 2 lists the magnetic susceptibilities of various relatively highly magnetic materials. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 Atomic or 
                   
               
               
                   
                   
                 Density 
                 Molecular 
               
               
                   
                 Material 
                 (g/cc) 
                 Weight 
                 Susceptibility 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Nickel 
                 8.9 
                 58.69 
                    600 
               
               
                   
                 Stainless 
                 7.8 
                 — 
                 400-1100 
               
               
                   
                 Steel 
               
               
                   
                 (magnetic, 
               
               
                   
                 martensitic) 
               
               
                   
                 Iron 
                 7.874 
                 55.847 
                 200,000 
               
               
                   
                   
               
             
          
         
       
     
     The data use to construct Tables 1 and 2 was obtained from a paper authored by John Schneck of General Electric Corporate Research and Development Center, Schenectady, N.Y. 12309, entitled “The Role of Magnetic Susceptibility In Magnetic Resonance Imaging:Magnetic Field Compatibility of the First and Second Kinds”. The disclosure of that paper is incorporated herein by reference. 
     Thus, the laryngoscope of the present invention is an instrument which is useful for pre and post clinical and surgical applications, especially in an environment proximate the strong magnetic field emitted by a magnetic resonance scanner. 
     It is appreciated that various modifications to the inventive concepts described herein may be apparent to those of ordinary skill in the art without departing from the spirit and scope of the present invention as defined by the appended claims.