Abstract:
A re-use prevention mechanism ( 160 ) for an apparatus ( 110 ) having a reusable part ( 120 ) and a single-use disposable part ( 130 ) connectable to the reusable part ( 120 ) is disclosed. The re-use prevention mechanism ( 160 ) comprises a blocking portion ( 1603 ) disposed, in use, between the disposable part ( 130 ) and the reusable part ( 120 ). An actuating member ( 1605 ) is operable between the blocking portion ( 1603 ) and one of the disposable part ( 130 ) and the reusable part ( 120 ) for moving the blocking portion ( 1603 ) into a blocking position upon disconnection of the disposable part ( 130 ) from the reusable part ( 120 ). In the blocking position, the blocking portion ( 1603 ) engages an abutment surface ( 1206 ) on one of the disposable part ( 130 ) and the reusable part ( 120 ) if a user attempts to reconnect the disposable part ( 130 ) to the reusable part ( 120 ) and thereby prevents re-connection of the disposable part ( 130 ) to the reusable part ( 120 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to improvements in apparatus for reducing cross-contamination, and more particularly to a re-use prevention mechanism and to a laryngoscope. 
         [0002]    While the invention has been developed primarily for use in laryngoscopes, and will be described hereinafter with reference to this application, it will be appreciated that the invention is not limited to this particular application and may also be used, for example, in other medical instruments, such as endoscopes and catheters, or indeed, in non-medical applications where hygiene is important, for example in electric toothbrushes with disposable heads, to reduce the incidence of cross-infection or contamination resulting from re-use of disposable parts. 
       BACKGROUND OF THE INVENTION 
       [0003]    Known laryngoscopes comprise an elongate handle and an arcuate blade that is adapted for insertion into a patient&#39;s throat. The blade is connected to the handle by rotating the blade upwardly with respect to the handle. The handle is hollow and contains batteries for powering a light source to provide illumination to a distal end of the blade. 
         [0004]    Historically, the handle and blade have been formed from metal to provide the stiffness required for opening a patient&#39;s airway. Accordingly, these known laryngoscopes have a high capital cost, and are therefore sterilised and reused many times during their service life. The typical cleaning method is autoclaving, which is in itself expensive. 
         [0005]    In recent years, concern has been raised as to the adequacy of the cleaning and sterilisation of laryngoscopes. It is noted that metal laryngoscope handles are particularly difficult to clean, as they are often knurled, which provides a multitude of locations for bacteria and other contaminants to avoid sterilisation. In an attempt to address this problem, some disposable blade laryngoscopes have been developed. However, known disposable blade laryngoscopes have retained the same connection system as for the older fully reusable metal laryngoscopes, in that the blade is rotated upwardly with respect to the handle to engage the blade to the handle. When the disposable blades are connected to the handle in this manner, the blade tip often touches the handle, and accordingly, contaminants present on the handle can be transferred to the blade and subsequently to the patient. 
         [0006]    Another problem with known disposable blades is that they often lack means for preventing their accidental re-use. Where means for preventing blade re-use are provided, it is often only apparent after a user has attempted several times to connect the blade to the handle that the blade in hand is a used blade, thereby causing user frustration and time delays. As will be appreciated, such frustration and delays can be critical in many instances where laryngoscopes are required. 
       OBJECT OF THE INVENTION 
       [0007]    It is an object of the present invention to overcome or substantially ameliorate one or more of the abovementioned disadvantages of the prior art, or at least to provide a useful alternative. 
       SUMMARY OF THE INVENTION 
       [0008]    Accordingly, in a first aspect, the present invention provides a re-use prevention mechanism for an apparatus having a reusable part and a single-use disposable part connectable to the reusable part, the re-use prevention mechanism comprising: 
         [0009]    a blocking portion disposed, in use, between the disposable part and the reusable part; 
         [0010]    an actuating member operable between blocking portion and one of the disposable part and the reusable part for moving the blocking portion into a blocking position upon disconnection of the disposable part from the reusable part; 
         [0011]    wherein, in the blocking position, the blocking portion engages an abutment surface on one of the disposable part and the reusable part if a user attempts to reconnect the disposable part to the reusable part and thereby prevents re-connection of the disposable part to the reusable part. 
         [0012]    In a second aspect, the invention provides medical device comprising: 
         [0013]    a reusable part defining a longitudinal axis; 
         [0014]    a disposable part for connection to the reusable part by engaging the disposable part with a longitudinal end of the reusable part and rotating the disposable part relative to the reusable part about the longitudinal axis. 
         [0015]    Preferably, the medical device further includes a re-use prevention comprising: 
         [0016]    a blocking portion disposed, in use, between the disposable part and the reusable part; 
         [0017]    an actuating member operable between blocking portion and one of the disposable part and the reusable part for moving the blocking portion into a blocking position upon disconnection of the disposable part from the reusable part; 
         [0018]    wherein, in the blocking position, the blocking portion engages an abutment surface on one of the disposable part and the reusable part if a user attempts to reconnect the disposable part to the reusable part and thereby prevents re-connection of the disposable part to the reusable part. 
         [0019]    Preferably, according to either of the above aspects, the actuating member is operable between the blocking member and the disposable part. More preferably, the actuating member resiliently biases the blocking portion toward the blocking position upon disconnection of the disposable part from the reusable part. 
         [0020]    In a preferred form, when the disposable part is engaged with the distal end of the reusable part, the blocking portion engages a recess in the reusable part to rotationally lock the disposable part to the reusable part. 
         [0021]    Preferably, the reusable part is elongate and defines a longitudinal axis. More preferably, the actuating member resiliently biases the blocking portion rotationally, about the longitudinal axis, toward the blocking position upon disconnection of the disposable part from the reusable part. 
         [0022]    Preferably, the disposable part is adapted for connection to the reusable part by engaging the disposable part with a longitudinal end of the reusable part and rotating the disposable part relative to the reusable part about the longitudinal axis. More preferably, the reusable part is generally cylindrical and includes a pair of locking lugs extending radially outwardly from diametrically opposite sides thereof. In a preferred form, the disposable part includes a generally cylindrical tubular coupling sleeve that is adapted to longitudinally slidably engage over a distal end of the reusable part. The disposable part preferably includes a pair of locking flanges extending radially inwardly from diametrically opposite sides of the sleeve and adapted to engage the locking lugs upon rotation, about the longitudinal axis, of the disposable part relative to the reusable part. 
         [0023]    Preferably, engagement of the blocking portion with the abutment surface limits the extent of longitudinal engagement of the disposable part with the reusable part to prevent engagement of the locking lugs and locking flanges. More preferably, a longitudinally extending recess is provided in said one of the disposable part and the reusable part, the blocking portion being engageable with the recess to permit sufficient longitudinal engagement of the disposable part with the reusable part to allow the locking lugs and locking flanges to engage. 
         [0024]    In a preferred form, the disposable part includes a cylindrical coupling sleeve adapted to engage the reusable part. Preferably, the re-use prevention mechanism is, in use, located in the cylindrical coupling sleeve. 
         [0025]    Preferably, the re-use prevention mechanism includes first and second interengageable collars connectable with one of the disposable part and the reusable part, the collars being rotatably lockable to one another in first and second relative rotational positions, wherein the blocking member extends from one of the collars, and wherein in the first position if a user attempts to connect the disposable part to the reusable part, the blocking portion engages the recess, and wherein in the second position if a user attempts to connect the disposable part to the reusable part, the blocking portion engages the abutment surface. In a preferred form, the collars are connected to the disposable part. More preferably, the blocking portion extends from the first collar. 
         [0026]    Preferably, the second collar includes a locking pin for engagement with a corresponding locking aperture in the disposable part to prevent relative rotation of the first collar and the disposable part when the pin and aperture are engaged. The locking pin is preferably adapted to fail if a torque above a predetermined level is applied between the disposable part and the reusable part. Preferably, the locking pin is adapted to withstand a shear force of between around 5N and around 100N, more preferably, between around 30N and around 70N, and in a particularly preferred form, of around 45N. 
         [0027]    Preferably, the actuating member takes the form of a resilient biasing finger extending longitudinally outwardly from the second collar, away from the reusable part, for engagement with an abutment portion on the disposable part to resiliently bias the second collar rotationally, about the longitudinal axis, with respect to the disposable part when the biasing finger is deformed against the abutment portion. The resilient biasing finger is preferably deformed against the abutment portion when the disposable part is rotated relative to the reusable part to disconnect the disposable part from the reusable part. 
         [0028]    Preferably, the reuse prevention mechanism is captivity retained within the coupling sleeve of the disposable part. In a preferred form, the first collar includes a radially outwardly extending retaining lug engageable with a corresponding retaining groove in the disposable part for captivity retaining the reuse prevention mechanism within the coupling sleeve of the disposable part. 
         [0029]    Preferably, the second collar includes at least one locking detent engageable with a corresponding notch in the first collar for locking the first and second collars against relative rotation about the longitudinal axis. More preferably, the locking detent engages the notch when the collars are in the second position. In a preferred form, the second collar includes three locking detents and the first collar includes three corresponding notches. Preferably, corresponding pairs of said detents and notches are unevenly circumferentially spaced about said re-use prevention mechanism. 
         [0030]    Preferably, the collars permanently lock together when moved into the second position. 
         [0031]    The second collar preferably includes a circumferential slot and the first collar preferably includes a corresponding radially extending guide projection engageable with the slot. More preferably, a first end of the slot defines the first position and a second end of the slot defines the second position. Preferably, a stop member is provided at the first end of the slot, the stop member being engageable by the guide projection to retain the collars in the first position. The guide projection is preferably disengageable from the stop member by applying a longitudinal compressive force between the disposable part and the reusable part to cause the guide projection to ride over the stop member. 
         [0032]    A longitudinally extending opening preferably extends from one longitudinal end of the second collar and into the slot. Preferably, the guide projection is longitudinally slidably engageable with the longitudinal opening to facilitate interengagement of the first and second collars. In a preferred form, the second collar includes three slots and three corresponding longitudinal openings, and the first collar includes three corresponding guide projections. More preferably, the guide projections and longitudinal openings are unevenly circumferentially spaced about the re-use prevention mechanism, such that the first and second collars can only be interengaged in a single predetermined relative rotational orientation. 
         [0033]    Preferably, with the collars in the first position, the disposable part can be axially slid onto the longitudinal end of the reusable part. More preferably, when the disposable part is engaged with the distal end of the reusable part and the disposable part is rotated relative to the reusable part in a predetermined direction, the collars are moved into the second position and the disposable part is locked to the reusable part in a configuration for use. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    A preferred embodiment of the present invention will be described hereinafter, by way of an example only, with reference to the accompanying drawings, in which: 
           [0035]      FIG. 1  is a schematic view of a laryngoscope system; 
           [0036]      FIG. 2  a schematic view showing how the laryngoscope handle is mounted on the battery charging module; 
           [0037]      FIG. 3  is a schematic view of the laryngoscope shown in  FIG. 1 , wherein the laryngoscope blade and handle are connected for use; 
           [0038]      FIG. 4  is a side elevation view of the laryngoscope handle of the system of  FIG. 1 ; 
           [0039]      FIG. 5  is an exploded side elevation view of the laryngoscope handle of  FIG. 4 ; 
           [0040]      FIG. 6  is an enlarged side elevation view of the distal end of the laryngoscope handle of  FIG. 5 ; 
           [0041]      FIG. 7  is a side elevation view of the laryngoscope blade of the system of  FIG. 1 ; 
           [0042]      FIG. 8  is an enlarged view of the proximal end of the laryngoscope blade of  FIG. 7 ; 
           [0043]      FIG. 9  is a partial side elevation view of the laryngoscope in a partly assembled state, with the coupling sleeve of the blade cut-away to show the re-use prevention mechanism in the first position; 
           [0044]      FIG. 10  is a partial side elevation view of the laryngoscope, with the coupling sleeve of the blade cut-away to show the re-use prevention mechanism in a configuration for removal of the blade from the handle; 
           [0045]      FIG. 11  is a longitudinal section view through the proximal end of the blade of  FIG. 8 , shown with the re-use prevention mechanism of  FIG. 10  installed in the first position; 
           [0046]      FIG. 12  is a part sectional side elevation view of the assembled handle and blade of the laryngoscope of  FIG. 3 , showing the re-use prevention mechanism in the second position; 
           [0047]      FIG. 13  is an enlarged side elevation view of the re-use prevention mechanism of the laryngoscope system of  FIG. 1 , shown with the first and second collars disengaged; 
           [0048]      FIG. 14  is a side elevation view of the re-use prevention mechanism of  FIG. 13 , shown with the first and second collars engaged in the first position; 
           [0049]      FIG. 15  is a side elevation view of the re-use prevention mechanism of  FIG. 13 , shown with the first and second collars engaged in the second position; 
           [0050]      FIG. 16  is a longitudinal section view through the proximal end of the blade of  FIG. 14 , taken after the blade has been removed from the handle and showing the blocking tab in a blocking position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Laryngoscope System 
       [0051]    Referring to the drawings, and in particular to  FIGS. 1 to 3 , there is provided a laryngoscope system  100  comprising a laryngoscope  110  including a reusable handle  120  and a single-use disposable blade  130 , as well as a battery charging module  150 . 
       Laryngoscope Handle 
       [0052]    As shown in  FIGS. 4 ,  5  and  6 , the handle  120  is generally cylindrical and elongate to define a longitudinal axis  1201 , a proximal end  1202  and a distal end  1203 . 
         [0053]    As can best be seen in  FIG. 6 , the handle  120  is stepped radially inwardly near its distal end  1203  to define a circumferential annular abutment surface  1206 . A recess  1207  extends longitudinally from the abutment surface  1206  toward the proximal end  1202  of the handle  120 . The recess  1207  defines a gap in the abutment surface  1206 . 
         [0054]    Referring again to  FIGS. 4 and 5 , the peripheral surface of the handle  120  is provided with longitudinally extending contoured lands  1208  to increase surface friction. The smooth contouring of the lands  1208  allows for ease of cleaning of the handle  120 . 
         [0055]    The handle  120  is hollow and includes an internal mounting frame  1209  to retain rechargeable batteries (not shown). 
       Laryngoscope Blade 
       [0056]    As seen in  FIG. 7 , the blade  130  is generally arcuate in shape for facilitating its insertion into the throat of a patient. A light pipe  1301  extends from a proximal end  1302  to a distal tip  1303  of the blade  130  for providing illumination into the patient&#39;s throat. The light pipe  1301  transmits illumination from a Light Emitting Diode (LED) (not shown) in the end of the handle  120 . A suitable light pipe  1301  is disclosed in the Applicants&#39; earlier International Patent Publication No. WO2002/071930, the disclosure of which is incorporated herein in its entirety. 
         [0057]    As best seen in  FIG. 8 , a generally cylindrical tubular coupling sleeve  1304  is provided at the proximal end  1302  of the blade  130  to facilitate connection of the blade  130  to the handle  120 . The coupling sleeve  1304  is configured so as to be longitudinally slidably engageable over the distal end  1203  of the handle  120 . As shown in  FIGS. 9 and 10 , a generally trapezoidal cut-out portion  1306  is provided in a wall of the coupling sleeve  1304 . The cut-out portion  1306  defines a radially extending abutment portion  1307  that is oriented diagonally with respect to the longitudinal axis  1201 . A longitudinally extending locking aperture  1308  is provided in the proximal end of the coupling sleeve  1304 , as can be seen in  FIG. 11 . 
       Blade/Handle Coupling 
       [0058]    Referring again to  FIGS. 4 ,  5  and  6 , the handle  120  includes a pair of locking lugs  1210  that extend radially outwardly from diametrically opposite sides of thereof. The blade  130 , as best seen in  FIGS. 8 ,  11  and  12 , includes a corresponding pair of locking flanges  1309  that extend radially inwardly from diametrically opposite sides of the to coupling sleeve  1304  for rotational engagement with the locking lugs  1210 . The locking flanges  1309  are adapted to engage the locking lugs  1210  upon rotation, about the longitudinal axis  1201 , of the blade  130  relative to the handle  120  in order to secure the blade  130  to the handle  120  against relative axial displacement, as shown in  FIG. 12 . 
       Re-Use Prevention Mechanism 
       [0059]    Returning to  FIG. 11 , a re-use prevention mechanism  160  is captivity retained within the coupling sleeve  1304  of the blade  130 . When the laryngoscope  110  is in use, the re-use prevention mechanism  160  is located between the blade  130  and the handle  120 , as can be seen in  FIG. 12 . The mechanism  160  includes first  1601  and second  1602  interengageable collars, which are shown in detail in  FIGS. 13 to 15 . The collars  1601  and  1602  are rotatable relative to one another about the longitudinal axis  1201  between a first position, as shown in  FIG. 14 , and a second position, as shown in  FIG. 15 . The collars  1601  and  1602  are also rotatably lockable relative to one another in the first and second positions. Moreover, the collars  1601  and  1602  permanently lock together when in the second position. 
         [0060]    Referring to  FIG. 13 , the first collar  1601  includes a blocking portion in the form of a longitudinally extending generally rectangular tab  1603 . When the collars  1601  and  1602  are in the first position, as shown in  FIGS. 9 ,  11  and  14 , the blocking portion aligns with and engages the recess  1207  in the abutment surface  1206 . This engagement rotationally locks the first collar  1601  to the handle  120 , and thereby locks the blade  130  to the handle  120  if the first  1601  and second  1602  collars are rotationally interlocked in one of the first and second positions. Engagement of the blocking portion  1603  with the recess  1207  also permits sufficient longitudinal engagement of the blade  130  with the handle  120  to allow the locking lugs  1210  and locking flanges  1309  to engage, as shown in  FIG. 12 . When in a blocking position, as shown in  FIG. 16 , the tab  1603  is engageable with the abutment surface  1206  of the handle  120  to prevent the blade  130  from being reused by limiting the extent of longitudinal engagement of the blade  130  with the handle  120  and thereby preventing engagement of the locking lugs  1210  and locking flanges  1309 . As shown in  FIG. 11 , a retaining lug  1604  also extends radially outwardly from a peripheral surface of the blocking tab  1603  for engagement with the retaining groove  1305  in the coupling sleeve  1304  of the blade  130  to captivity retain the reuse prevention mechanism  160  within the coupling sleeve  1304 . 
         [0061]    Referring again to  FIG. 13 , the second collar  1602  includes an actuating member in the form of a resilient biasing finger  1605 , which extends from the second collar  1601  longitudinally outwardly away from the handle  120 . As shown in  FIG. 10 , the biasing finger  1605  is operable between the abutment portion  1307  of the blade  130  and the blocking tab  1603  for resiliently biasing the blocking tab  1603  rotationally about the longitudinal axis  1201 , so as to move the blocking tab  1603  into the blocking position, as shown in  FIG. 16 , upon disconnection of the blade  130  from the handle  120 . When the blocking tab  1603  is in the blocking position, re-connection of the blade  130  to the handle  120  is prevented. 
         [0062]    As can be seen in  FIG. 13 , the second collar  1602  also includes a locking pin  1606 . As shown in  FIGS. 11 and 12 , the locking pin  1606  is engageable with the locking aperture  1308  in the blade  130  to prevent relative rotation of the first collar  1601  and the blade  130  when the pin  1606  and aperture are engaged. The locking pin  1606  is adapted to fail if a predetermined torque is applied between the blade  130  and the handle  120 . The locking pin  1606  is designed to withstand a torque sufficient to apply a shear force to the pin of between around 5N and around 100N, and more preferably between around 30N and around 70N. However, in a particularly preferred embodiment, the pin  1606  is adapted to fail if a torque sufficient to generate a shear force of around 45N is applied. 
         [0063]    Referring again to  FIG. 13 , the second collar  1602  also includes three circumferentially spaced locking detents  1607 . The first collar  1601  includes three corresponding notches  1608 . The locking detents  1607  are engageable with the notches  1608  for locking the first  1601  and second  1602  collars against relative rotation about the longitudinal axis  1201 . The locking detents  1607  engage the notches  1608  when the collars  1601  and  1602  are in the second position, as shown in  FIG. 15 . However, as shown in  FIG. 14 , when not engaged with the notches  1608 , the locking detents  1607  resiliently engage a radially outwardly extending circumferential flange  1609  of the first collar  1601  and thereby resiliently bias the first  1601  and second collars  1602  longitudinally away from one another. 
         [0064]    Again, referring to  FIG. 13 , three circumferential slots  1610  are provided in the second collar  1602  and are engageable by corresponding guide projections  1611  extending radially outwardly from the first collar  1601 . The slots  1610  and guide projections  1611 , as with the detents  1607  and notches  1608 , are also unevenly circumferentially spaced. A first end  1612  of each of the slots  1610  defines the first relative position of the first  1601  and second  1602  collars, as shown in  FIG. 14 , and a second end  1613  of the slots  1610  defines the second relative position of the collars  1601  and  1602 , as shown in  FIG. 15 . A stop member  1614  is provided at the first end  1612  of each of the slots  1610  and is engageable by the corresponding guide projection  1611  to retain the collars  1601  and  1602  in the first position. The guide projections  1611  can be disengaged from the corresponding stop members  1614  by applying a longitudinal compressive force between the blade  130  and the handle  120  to cause the guide projections  1611  to ride over the stop members  1614  against the resilient bias of the locking detents  1607 . 
         [0065]    As can be seen in  FIG. 13 , three longitudinally extending openings  1616  extend from an inner longitudinal end  1616  of the second collar  1602 . Again, the openings  1616  are unevenly circumferentially spaced about the second collar  1602 . Each of the openings  1616  extends into a corresponding one of the three slots  1610 . The guide projections  1611  are each longitudinally slidably engageable with a corresponding one of the longitudinal openings  1616  to facilitate interengagement of the first  1601  and second  1602  collars. The uneven spacing of the openings  1616  and the guide projections  1611  about the second collar  1602  ensures that the first  1601  and second  1602  collars can only be interengaged in a single predetermined relative rotational orientation. It will be appreciated that this predetermined relative orientation corresponds to a predetermined relative rotational location of the blocking portion  1603  and the biasing finger  1605 . 
       Connection of the Blade and Handle 
       [0066]    To install the re-use prevention  160  mechanism into the blade  130 , the first  1601  and second  1602  collars are connected together in the first position as shown in  FIG. 14 . The re-use prevention mechanism  160  is then longitudinally inserted into the coupling sleeve  1304  of the blade  130  and is retained axially by engagement of the retaining lug  1604  and retaining groove  1304  and retained rotationally by engagement of the locking pin  1606  and locking aperture  1308 , as shown in  FIG. 11 . When the collars  1601  and  1602  are in the first position and with the retaining lug  1604  and retaining groove  1304  engaged, the blocking portion  1603  is correctly aligned for engagement with the recess  1207  of the handle  120 . In a preferred form, the blade  130  is supplied with the re-use prevention mechanism  160  pre-installed, as shown in  FIG. 11 . 
         [0067]    To connect the blade  130  to the handle  120 , the distal end of the handle  120  is longitudinally inserted into the coupling sleeve  1304  and, if required, the handle  120  is rotated about the longitudinal axis  1201  until the recess  1207  aligns with the blocking tab  1603 . With the recess  1207  and blocking tab  1603  aligned, a longitudinal compressive force is applied between the blade  130  and the handle  120  to cause the blade  130  to be pressed fully on to the handle  120 , whereupon the blocking tab  1603  fully engages the recess  1207  and the guide projections  1611  are caused to ride over the corresponding stop members  1614 , and then the handle  120  is rotated anticlockwise with respect to the blade  130  to move the collars  1601  and  1602  into the second position, as shown in  FIG. 12 . Engagement of the locking pin  1606  with the locking aperture  1308  and the blocking tab  1603  with the recess  1207  secure the first  1601  and second  1602  collars respectively to the blade  130  and handle  120  during rotation between the first and second positions. 
         [0068]    During rotation of the blade  130  relative to the handle  120  between the first and second positions, the locking lugs  1210  and locking flanges  1309  engage to axially secure the blade  130  to the handle  120  in the second position, as shown in  FIG. 12 . Also, when the second position is reached, the locking detents  1607  and notches  1608  engage to secure the first  1601  and second  1602  collars against relative rotation. Also, engagement of the guide projections  1611  with the slots  1610  locks the collars  1601  and  1602  together axially. Accordingly, in the second position, the collars  1601  and  1602  are permanently locked together. With the collars  1601  and  1602  so secured, engagement of the blocking tab  1603  with the recess  1207  and the locking pin  1606  with the locking aperture  1308  rotationally locks the blade  130  to the handle  120 . 
         [0069]    It will be appreciated that during connection of the blade  130  to the handle  120 , the tip of the blade  130  is isolated from the handle  120  to reduce the probability of contamination of the blade  130  by the handle  120 . This situation is contrasted to that of known laryngoscopes, where it is necessary for the blade tip to be placed very close to the handle prior to align the coupling components of the blade and handle prior to rotating the blade upwardly with respect to the handle to lock the blade onto the handle. 
       Disconnection of the Blade and Handle 
       [0070]    To disconnect the blade  130  from the handle  120 , the handle  120  is rotated clockwise with respect to the blade  130 , about the longitudinal axis  1201 . A predetermined torque must be applied between the blade  130  and the handle  120  to cause shear failure of the locking pin  1606  and thereby allow the handle  120  to rotate relative to the blade  130 . Once the pin  1606  has failed, the handle  120  will rotate sufficiently relative to the blade  130  to disengage the locking lugs  1210  and flanges  1309 . Also, as the handle  120  is rotated, the biasing finger  1605  is deformed against the abutment portion  1307  of the coupling sleeve  1304 , as shown in  FIG. 10 , such that when the distal end  1203  of the handle  120  is longitudinally removed from the coupling sleeve  1304 , the biasing finger  1605  resiliently rotates the blocking tab  1603  in an anti-clockwise direction relative to the blade  130  and into a blocking position as shown in  FIG. 16 . As discussed above, with the blocking tab  1603  in the blocking position, if a user attempts to re-connect the blade  130  to the handle  120 , the blocking tab  1603  engages the annular abutment surface  1206  of the handle  120  to prevent the extent of longitudinal engagement of the handle  120  and blade  130  required to allow the locking lugs  1210  and flanges  1309  to engage. 
       Alternative Embodiments 
       [0071]    It will be appreciated by those skilled in the art that the claimed invention may be embodied in many other forms. Some alternative embodiments are provided below by way of example only: 
         [0072]    the re-use prevention mechanism may be connected to the handle, rather than to the blade; 
         [0073]    the actuating member may be connected to the blade or the handle rather than to either of the collars and may engage the collars, rather than being connected to one of the collars and engaging the blade or the handle; 
         [0074]    the biasing finger may act between the handle and the blocking portion, rather than between the blade and the blocking portion. 
         [0075]    As will be appreciated, the several examples of alternative embodiments listed above are by no means exhaustive, and those skilled in the art will understand that many additional alternative embodiments of various components of the illustrated laryngoscope may be employed within the scope of the invention. Also, while the invention has been described with reference to a laryngoscope, it can also be used in other medical instruments, such as endoscopes and catheters, or indeed, in non-medical devices where hygiene is important, for example in electric toothbrushes with disposable heads, to reduce the incidence of cross-infection or contamination resulting from re-use of disposable parts.