Abstract:
Under- and overinflation of retention balloons and cuffs for catheters including Foley catheters, and for endotracheal tubes, tracheostomy tubes, laryngeal mask airways and similar devices is correlated with hospital acquired infections and with patient injury. In this patent, a solution that correctly inflates inflatable retention devices is taught, whereby a pressure release means is incorporated into the inflation pathway from the fluid input syringe to the retention means while inflating. This pressure release means can be set to open at or near the optimal fluid pressure so that overinflation can be prevented by releasing any pressure above the optimal pressure and underinflation can be prevented by a user pressurizing the cuff until the valve is noticed to open. As well, observation of fluid leaked through the pressure relief means can indicate misplacement of the retention means, allowing the user to reposition it before patient injury occurs. The invention is presented as a standalone part and in a format whereby the invention is integrated into existing airway cuff inflation designs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from U.S. provisional patent application Ser. No. 61/586,460 filed Jan. 13, 2011. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0003]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    Endotracheal tubes (ETT), tracheostomy tubes, laryngeal mask airways (LMAs) and similar devices are employed to provide respiration to patients in hospital settings when undergoing procedures or recovering or otherwise are unable to breathe. A typical ETT—such as the Mallinckrodt Hi-Lo Cuffed Tracheal Tube—comprises a tube to act as an airway, a cuff to secure the airway (a “retention means”), an inflation line to that cuff, a pilot balloon to assess pressure in the cuff, and an injection port with a one-way non-return valve to allow injection of fluid—typically air, water or saline—into the cuff via the pilot balloon and inflation line. 
         [0005]    For brevity, ETT will be used herein to refer to the mentioned endotracheal tubes (ETT), tracheostomy tubes, laryngeal mask airways (LMAs) and similar devices collectively, unless specific circumstances or implementations require otherwise. ETT is used herein as a general reference to “respiratory gas supply means entering the mouth or a tracheotomy incision” from the definition for Patent Classification class 128/207.14 including endotracheal tubes, tracheal tubes, tracheostomy tubes, breathing tubes, intubation tubes and LMAs. LMAs differ from the others in how they establish an airway as LMAs provide a supraglottic airway, however for the purposes of this invention the point of interest is the inflation means securing them while in use which is similar. 
         [0006]    Physicians (most often anesthetists) and/or nurses need a safe means of securing the ETT to the patient so that respiration can be maintained reliably throughout the patient&#39;s procedure and stay on the ventilator, and until the ETT is intentionally removed. 
         [0007]    ETTs are typically held in place with an inflatable cuff, inflated by injecting into it typically either air or saline. For endotracheal and tracheostomy tubes with inflatable cuffs, the cuff is inserted into the trachea and for an LMA the cuff is inserted into the pharynx. Typically, cuff inflation is done without measurement of the pressure inside the cuff. Frequently there will be a pilot bulb, which can be squeezed or looked at to get an idea of the internal pressure in the cuff, but this measurement is rarely quantified. Also as noted in Liu et al (Liu, Jianhui et al; “Correlations between controlled endotracheal tube cuff pressure and postprocedural complications: a multicenter study” Anesth Analg 2010; 111:1133-7), inflation done without measurement leads to wide variation in cuff pressures. Their work revealed an average cuff pressure of 43+/−23.3 mmHg, sometimes going as high as 210 mmHg. 
         [0008]    If the cuff is underinflated there is a risk of the ETT slipping or falling out, and/or for fluids, such as saliva, to enter the trachea possibly leading to pneumonia and death. If the cuff is overinflated there is a risk of local tissue damage and further adverse events to the patient. Overinflation of endotracheal tube cuffs has been linked to the following adverse events: abrasion of the arytenoid cartilage vocal process; cartilage necrosis; cicatrix formation; consequences of failure to ventilate including death; damage to the perichondrium; development of dense or diffuse fibrosis invading the entire glottic area; emphysema; endobronchial aspiration; endobronchial intubation (hypoxemia); endotracheobronchial aspiration; epistaxis; esophageal intubation (stomach distention); excoriated membranes of the pharynx; eye trauma; fibrin deposition; formation of subglottic web; fracture-luxation of cervical column (spinal injury); fragmentation of cartilage; glottic edema (supraglottic, subglottic retroarytenoidal); granuloma of the inner arytenoid area; infections (laryngitis, sinusitis, abscess, respiratory tract infection); inflammation; intermittent aphonia and recurrent sore throat; laryngeal fibrosis; laryngeal granulomas and polyps; laryngeal obstruction; laryngeal stenosis; laryngeal ulcers; laryngotracheal membranes and webs; membraneous glottic congestion; membraneous tracheobronchitis; mild edema of the epiglottis; mucosal sloughing; paresis of the hypoglossal and/or lingual nerves; perforation of esophagus; perforation of the trachea; pneumothorax; replacement of the trachea wall with scar tissue; respiratory obstruction; retrobulbar hemorrhage; retropharyngeal abscess; retropharyngeal dissection; rupture of the trachea; sore throat; dysphagia; stricture of nostril; stridor; subglottic annular cicatricial stenosis; submucosal hemorrhage; submucous puncture of the larynx; superficial epithelial abrasion; swallowed tube; synechia of the vocal cords; teeth trauma; tissue burns; tracheal bleeding; tracheal stenosis; trauma to lips, tongue, pharynx, nose, trachea, glottis, palate, tonsil, etc.; traumatic lesions of the larynx and trachea; ulcerations exposing cartilaginous rings and minor erosions at cuff site; ulceration of the lips, mouth, pharynx; ulcers of the arytenoid; vocal cord congestion; vocal cord paralysis; and vocal cord ulcerations. [Source: Mallinckrodt Lo-Prof Tracheal Tube Cuffed Instructions for Use] 
         [0009]    It is generally accepted that the correct inflation pressure is 25 cmH2O (18.4 mmHg or 0.36 psi) for ETTs. With a 20% tolerance for error, a range of acceptable pressures may be between 20 and 30 cmH2O. 
         [0010]    A solution to the above problems of under- and overinflation of the ETT cuff, and the subject of this invention, is the incorporation of a pressure release valve into the inflation pathway from the fluid input syringe to the cuff while inflating. This valve can be set to open at or near the optimal fluid pressure so that overinflation can be prevented by releasing pressure above the optimal pressure and underinflation can be prevented by a user pressurizing the cuff until the valve is noticed to open. Valve incorporation into the inflation pathway could be in the form of an adaptor to use with standard commercially available ETTs, or as a valve integrated into a new design for ETTs. 
         [0011]    A related problem exists for insertion of other catheters that require inflation of a retention means for fixation (temporary or otherwise) in a body space. If the insertion is correct but the inflation pressure is too low, the catheter may slip. If the insertion is placed incorrectly and the retention means is inflated in a location that is too small to accommodate the inflated size, tissue damage may occur. For example, over-inflating a balloon in a blood vessel could lead to rupture of the vessel. Also, consider Foley and other indwelling catheters for the administration and collection of fluids. Foley catheters can be used to collect urine for patients that are incontinent and for patients undergoing procedures in which they are unconscious. In this use, Foley catheters are inserted partially into the bladder, to a point where an inflatable retention means—typically a balloon—located near its distal tip can be inflated to prevent the catheter from being pulled out. Should the catheter not be inserted far enough and the balloon not enter the bladder, the balloon could be inflated within the patient&#39;s urethra resulting in pain if the patient is conscious, and if they are unconscious the overinflation may go unnoticed and the patient may also experience tissue damage due to the compression of the urethra. Foley catheters can also be used in gastrostomy, such as for a Janeway gastrostomy procedure where the catheter is used to provide access to the patient&#39;s stomach. Underinflation of the balloon for these catheters can lead to complications including loose catheters and spills. 
         [0012]    Foley catheters comprise a tube to conduct fluids, an inflatable balloon to secure the catheter from inside the space it is to conduct fluids to and/or from (e.g. the bladder for urine collection), an inflation line to the balloon, (optionally) a pilot balloon to assess pressure in the balloon, and an injection port with a one-way non-return valve to allow injection of fluid—typically water or saline—into the balloon via the inflation line. The one-way non-return valve may be similar to those of the ETTs constructed with plungers and springs, or in a simple version they can be as simple as an elastomer cap over the interface to the inflation port through which a needle punctures when injecting. 
         [0013]    Similar to the ETTs, a pressure release valve may be incorporated into the Foley catheter&#39;s inflation pathway from the fluid input source to the balloon to solve this problem of under- and overinflation of the Foley catheter balloon. The valve can be set to open at or near the optimal fluid pressure so that overinflation can be prevented by releasing pressure above the optimal pressure and underinflation can be prevented by a user pressurizing the cuff until the valve is noticed to open. Depending on what volume of fluid is pumped into the cuff before the valve opens, the physician can also determine whether or not the balloon cuff has been inflated where it was intended, such as the bladder, or in an undesirable location, such as the urethra. 
         [0014]    For a catheter such as a Foley catheter, the adaptor implementation of the invention can work as an adaptor interposed between the Foley catheter balloon&#39;s inflation means and the Foley catheter balloon. In some cases the inflation port may be a Luer fitting with a check valve (one-way valve) as for the ETTs above and the use would be the same, with possible adaptation to correct for pressure differences required to maintain the balloon&#39;s retention under the pressures of the bladder. In other cases the catheter&#39;s inflation port may be through a rubber, elastomeric or other covering where a needle is usually required. In this case the adaptor could either have a needle built in or be adapted for the use of a needle at its interface to the inflation port. 
         [0015]    Valves and related mechanisms have been described in ETTs and catheters before. However, previous mechanisms have been bulky and cumbersome, inefficient, complicated, disruptive of the user&#39;s routine practice, and costly to the point where these solutions are rarely seen and the problems of over- and underinflation still exist. Contrasting previous solutions, the invention disclosed herein is of a simple construction with only one additional part to the standard catheter and ETT design; it is non-obtrusive; it conforms to the user&#39;s expected routine of standard practice; and it is very inexpensive due to its simplicity. 
       Patent Documents 
       [0016]    See U.S. Pat. Nos. 3,642,005, 3,794,043, 3,854,484, 4,000,741, 4,116,201, 4,119,101, 4,147,170, 4,159,722, 4,248,222, 4,284,084, 4,361,107, 4,403,988, 4,501,273, 4,584,998, 4,598,707, 4,649,914, 4,653,539, 5,360,003, 6,530,898, 7,360,556, 7,673,653, 7,717,116 and 7,987,851, and applications 20110220116, 20110220118 and 20110220119. 
       SUMMARY OF THE INVENTION 
       [0017]    One form of the invention is as an adaptor that is used with commercially available ETTs and catheters whose proper function requires inflation through an inflation port. The invention can be a hollow chamber interposed between an inflation means (such as a syringe) and the ETT or catheter, with a release valve to allow passage of a fluid above a certain pressure, and with interfaces to allow connection to the appropriate devices used to inflate the ETT&#39;s or catheter&#39;s cuff and to the connector to the ETT or catheter cuff&#39;s inflation line. Typically these interfaces can include an interface to receive a syringe input and an output interface to mate with the particular ETT tube being used. For adaptors used in hospital settings, the interfaces will usually be Luer type fittings. 
         [0018]    In another embodiment of the invention the valve can be integrated into the inflation port of a modified version of a commercially available ETT or catheter. In this embodiment of the invention, the ETT&#39;s or catheter&#39;s cuff inflating injection port can be augmented to further include a pressure release valve. This pressure release valve preferably vents outside of the ETT or catheter and is preferably positioned in the expanded injection port external to the airspace created by the cuff, the cuff inflation line and pilot balloon on the proximal to the user side of the one-way valve. The one-way valve is able to function as it does for the typical ETT. In summary, the invention provides an automatic pressure release means without interfering with the normal operation and function of the ETT. 
         [0019]    Methods of using the invention for inflating cuffs and balloons without under- or over-inflation are described. As well, methods for determining when inflation of a catheter&#39;s balloon occurs outside of the desired body space and in a more confined space are also described. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a perspective view of the endotracheal tube adaptor apparatus; 
           [0021]      FIG. 2  is a side view of the endotracheal tube adaptor apparatus; 
           [0022]      FIG. 3  is a cutaway view of the endotracheal tube adaptor apparatus from the side; 
           [0023]      FIG. 4  is a perspective view of the modified endotracheal tube apparatus including the invention; 
           [0024]      FIG. 5  is a side view of the modified endotracheal tube apparatus including the invention; and 
           [0025]      FIG. 6  is a cutaway view of the modified endotracheal tube apparatus from the side. 
           [0026]      FIG. 7  shows views of standard LMA and ETT devices. 
           [0027]      FIG. 8  shows Foley catheters properly placed in a male and female (modified from http://calder.med.miami.edu/pointis/indwelling.html) with reference to the anatomy. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    One embodiment of the invention as an adaptor to provide inflation pressure control to an ETT or other catheter with inflatable retention means will now be described with reference to  FIGS. 1 to 3 . 
         [0029]    In  FIG. 1 , the adaptor is shown in a perspective view and in  FIG. 2 , the adaptor is shown in a side view. The adaptor as shown is comprised of a main body  31 , valve  36  and fluid supply interface cap  38 . 
         [0030]    Main body  31  has distal and proximal ends with the distal end having the ETT or catheter interface  32  and with the proximal end connecting to the fluid supply interface cap  38 . Main body  31  has a passage to allow fluid to move through main body  31  between and through ETT or catheter interface  32  and interface cap  38 . Joined to main body  31  is valve  36 , which in  FIGS. 1 to 3  is drawn as an umbrella valve that joins to main body  31  preferably on an external surface. Main body  31  (and main body  1  in  FIGS. 4 to 6 ) can be cheaply manufactured using plastics and can be dyed to have color and made opaque or transparent as desired. Candidate plastics include polycarbonate and Acrylonitrile butadiene styrene (ABS). 
         [0031]    Fluid supply interface cap  38  provides an interface so that fluid may be delivered through the adaptor, into the ETT or catheter and to the ETT cuff or catheter balloon to inflate the cuff or balloon. As such, the fluid supply interface cap  38  can be designed to mate with a standard injection device, such as by having the geometry of the end of fluid supply interface cap  38  mate with a hospital syringe for hospital use. 
         [0032]    Fluid supply interface cap  38  has been drawn in  FIG. 1  as a separate part to main body  31  that is bonded to main body  31  but could be a part of main body  31  if the device was made with a process such as blow-molding. 
         [0033]    ETT or catheter interface  32  is at the distal end of main body  31 . ETT or catheter interface  32  functions to connect to the ETT or catheter tube to allow passage of the inflating fluid, and therefore ETT or catheter interface  32  preferably has geometry matching the ETT in use. These interfaces can conform to the aforementioned Luer standard, for example. 
         [0034]    The valves in the figures (valve  36  and valve  136 , for example) have been presented as umbrella valves but can be other valve types or mechanisms, such as rubber flaps, spring-loaded traps and duckbill valves. 
         [0035]    Valve  36  and valve  136  serve to cover fluid venting holes  133  (shown in  FIG. 3 ) until the pressure inside main body  131  hollow space  140  and in air cavity  139  beneath valve  136  rises over a defined pressure, such as 25 cmH2O a recommended pressure for ETT cuffs to provide hold without causing injury to the patient. Valve  136  is designed to open at pressures above the defined pressure. In the case of an umbrella valve, the valve can be made of a flexible material (silicone, for example) such that the increased pressure causes valve  136  to deform and/or lift creating a gap through which fluid can leak. 
         [0036]    In a typical use, a syringe (not shown) filled with fluid is connected to fluid supply interface cap  38 . The syringe plunger (not shown) is pressed forcing air through fluid supply interface cap  38  and into main body  31 . Air flows through ETT or catheter interface  32  and into the ETT or catheter (not shown) and the pressure rises in the cuff or balloon (not shown) inflating it. Simultaneously, the pressure increases in main body  31  and in the space between main body  31  and underneath valve  36  to match closely the pressure in main body  31 . The user continues to force air or other fluid into the main body  31  and through it into the inflation port and cuff or balloon until the valve  36  opens indicating it has reached the specified pressure, or until the user is satisfied they have the appropriate pressure. If they have overfilled the cuff or balloon, the excess pressure will leak out through the valve. 
         [0037]    In another embodiment of the invention, the release valve function of the invention can be integrated into the inflation port of a standard ETT or catheter as shown in  FIGS. 4 through 6 . In  FIG. 4 , the integrated invention is shown in a perspective view and in  FIG. 5 , the integrated invention is shown in a side view.  FIG. 6  shows a cutaway view to demonstrate the function of release valve  6  and the one-way non-return valve. 
         [0038]    Similar to standard ETTs and catheters, an integrated embodiment of this invention has tubing  5  to conduct fluid to an inflatable cuff or balloon (not shown); a one-way valve to prevent pressure leaking out of the cuff or balloon comprised of a plunger  9  with plunger end cap  7 , seal  10  and spring  11 ; and a main body  1  to contain the one-way valve and offer an interface for the inflating syringe to connect to. Optionally, the integrated embodiment of this invention can also have a pilot bulb  4  for indicating pressure level in the cuff or balloon by feel and sight. Main body  1  along with distal endpiece  2  and fluid supply interface endpiece  3  together are analogous to the injection port of the standard ETT. Distal endpiece  2  and fluid supply interface endpiece  3  have been drawn separately from main body  1  for ease of manufacture by injection molding, but could be combined. 
         [0039]    Plunger  9  has been extended compared with the standard inflation port&#39;s plunger to accommodate the extra length of main body  1  which has been extended to accommodate valve  6  and allow pushing on plunger end cap  7  by the tip of a syringe delivering fluid through syringe interface  8 . 
         [0040]    Valve  6  has been added to prevent overinflation in the cuff or balloon and main body  1  has been modified to contain valve  6 . Valve  6  has the same purpose and general function as valve  36  of the adaptor described above. When pressure in main body  1  and, due to the fluid connection between the two areas, in valve air cavity  119  beneath valve  16  in  FIG. 6  rise above the selected pressure, valve  16  opens. With valve  16  open, inflation fluid can escape, releasing pressure until the internal pressure in main body  1  and the cuff or balloon reaches the defined pressure and valve  16  can close. 
         [0041]    Looking at  FIG. 6 , operation of the one-way valve of the invention is seen to be similar to the standard ETT. When the cuff or balloon pressure is not being altered (the cuff or balloon is neither being inflated nor deflated), spring  111  is compressed such that it pushes against back wall  120  of distal endpiece  2  and the distal face of plunger spring rest  121  such that seal  110  is pressed against the back wall  122  of main body  1  preventing fluid from passing through main body  1  to end cap air passage  118 . 
         [0042]    In a typical use, when the user wishes to inflate the cuff or balloon, the user inserts a syringe into syringe interface  18  of fluid supply interface endpiece  13 . The syringe contacts and displaces plunger end cap  17 , moving plunger  19 , further compressing spring  111  and forcing back plunger  19  and seal  110  to open air passage  118 . The user may then press on the syringe to force fluid through main body  1 , air passage  118 , distal end cap  2 , pilot bulb  14  and into the cuff or balloon (not shown) inflating it. Simultaneously, the pressure increases in main body  1  and in air cavity  119  beneath valve  16  to match closely the pressure in main body  31 . Fluid venting holes  116  connect the air spaces inside main body  1  and air cavity  119 . Again, once the pressure in the cuff and in main body  1  exceeds an optimal pressure, the pressure will also be increased in air cavity  119  causing valve  16  to open. Valve  16  will remain open until the pressure is reduced to the optimal level. 
         [0043]    The user may deflate the cuff by inserting the syringe into syringe interface  18  to open the one-way valve as above, and then pulling back on the syringe to withdraw fluid into the syringe. 
         [0044]    Plunger end cap  17  may further comprise channels  117  to prevent a seal forming between the syringe and the face of plunger end cap  17 , which could limit the injection of fluid. 
         [0045]    As with the previous instantiation&#39;s valve, valve  16  has been presented as an umbrella valve but can be other valve types or mechanisms, such as rubber flaps, spring-loaded traps and duckbill valves. Its role is to cover the fluid venting holes  116  (shown in  FIG. 6 ) until the pressure inside main body  1  and in air cavity  119  beneath valve  16  rises over the defined pressure. 
         [0046]    Valve  36  is preferably positioned proximal to the one-way valve (closer to the user and the inflation means) as shown in the figures, so that normal function of the one-way valve is preserved. Inflation, re-inflation and deflation procedures can be the same. Also, if there is accidental compression of the cuff such as by accidental contact with the patient, transmission of the increased pressure to the pressure release valve can be stopped by the one-way non-return valve and the cuff does not accidentally deflate. 
         [0047]      FIG. 7  has been added to show commercially available ETTs and their common parts as referenced in this invention disclosure. On the left is LMA  70  and on the right is endotracheal tube  71 . The invention as an adaptor could interface to inflation port  74  to inflate pilot balloon  73  and through inflation line  72  either cuff  75  for LMA  70  or cuff  76  for endotracheal tube  71 . The invention as an integrated part could be built into a modified version of inflation port  74 . 
         [0048]      FIG. 8  has been added to demonstrate Foley catheters in use inside male and female patients and to illustrate how inflation outside of the bladder could be painful and damaging to the patient. The Foley catheter  82  comprises a tip  80  where fluid is dispensed and taken in (in this example of the figure, urine is removed), a balloon  81  for retention within the body space, inflation line  82  for directing fluid to balloon  81 , inflation port  84  and fluid administration and/or collection port  85 . In the diagram the balloon  81  is shown inflated and inside the bladder. The Foley catheters illustrated are standard devices not incorporating the invention. The invention could be used as an adaptor interfacing to inflation port  84 , or the invention could be integrated into inflation port  84 . 
         [0049]    The invention can also be used to assess whether or not an ETT or catheter, particularly one with an inflatable retention means like the Foley catheter, has been inserted correctly. The user could proceed as they normally do for site preparation and insertion of the ETT or catheter. Once the ETT or catheter is in a position that the user things is correct, the user can attempt to inflate the cuff or balloon with a small amount of fluid less than the amount required to inflate the cuff or balloon under normal circumstances. For example, for a balloon requiring 10 mL to fill, the user could inject 3 mL and examine the valve. If at this point the valve is noted to have opened and/or have leaked fluid, the user can hypothesize that the cuff or balloon is in a position where it cannot expand freely and therefore should be reinserted and/or the patient&#39;s situation should be investigated further in case there is another issue beyond a short insertion. If there is no leakage of fluid, it can be assumed that the cuff or balloon is in the correct location and the full amount of fluid required can be injected.