Abstract:
A method of sealing a trachea is provided that includes inserting a tracheal tube having an inflatable cuff made of a compliant material into a trachea. The method includes inflating the inflatable cuff with a fluid to a first pressure that exceeds a second pressure necessary to create a seal between the inflatable cuff and the tracheal wall. The method includes deflating the inflatable cuff by releasing a first pressure to allow the fluid to flow out of the inflatable cuff without applying vacuum pressure to the fluid while evaluating a rate of change of pressure of the fluid in the inflatable cuff. The method includes identifying a variance in the rate of change of pressure corresponding to a third pressure at which the inflatable cuff separates from the tracheal wall, determining the second pressure by analyzing the third pressure, and reinflating the inflatable cuff to the second pressure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent documents claim the benefit of the filing date under 35 U.S.C. §119(e) of Provisional U.S. Patent Application Ser. No. 62/114,369 filed Feb. 10, 2015, which is hereby incorporated by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to medical devices and more specifically to endotracheal tubes and tracheostomy tubes. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Certain medical devices are used to regulate the flow of fluids and substances in and out of a patient&#39;s body. Endotracheal tubes and tracheostomy tubes are two specific examples of such a medical device. These devices, also known as tracheal tubes, assist the patient in breathing and regulate the airflow in and out of the patient&#39;s lungs. Endotracheal tubes are inserted through the patient&#39;s mouth down into the trachea, whereas tracheostomy tubes are inserted through a surgical incision in the patient&#39;s neck. Ventilators are generally attached to the tracheal tubes to assist the patient&#39;s breathing. 
         [0005]    To ensure proper regulation of air flow and to prevent unwanted fluids or other substances from entering the lungs, a seal between the tracheal wall and the tracheal tube is desirable. With a proper seal, the only passageway into the lungs is through the regulated tracheal tube. This seal is usually achieved through the use of an inflatable cuff attached to the tracheal tube. The cuff is deflated when the device is inserted into the patient&#39;s trachea, and, once the tracheal tube is in position, the cuff is inflated to achieve a seal between the inner wall of the trachea and the outer wall of the tracheal tube. The cuffs are generally inflated with air, but other fluids can be used, including liquids. However, inflatable cuffs can cause multiple problems related to maintenance, patient discomfort, and potential medical complications. Thus, elimination of the problems related to current inflatable cuff designs is desirable. 
         [0006]    There are two general categories of cuffs: complaint cuffs and noncompliant cuffs. Noncompliant cuffs are made of an inelastic material, typically polyvinyl chloride (PVC), and thus have a set volume when fully inflated. Noncompliant cuffs are inflated at a low pressure, which ensures that the cuff applies a corresponding low pressure against the tracheal wall when fully inflated. Therefore, patients encounter minimal discomfort when noncompliant cuffs are used. However, tracheas vary in size, ranging anywhere from 18 to 25 millimeters in diameter. To further complicate this process, clinicians do not know the diameter of the patient&#39;s trachea when performing an endotracheostomy or tracheostomy, thus they typically merely estimate the tracheal diameter based on external characteristics of the patient, such as gender and body type. Because of varying tracheal diameters, noncompliant cuffs are designed to fit any sized trachea. However, this universal cuff design presents problems, especially when a patient with a smaller trachea is presented. With the inelastic material used for noncompliant cuffs, the cuffs must have a fully inflated diameter large enough to seal the largest tracheas. Therefore, with a smaller trachea, a smooth seal is not achieved between the cuff and the tracheal wall because the cuff is not able to fully expand. Instead, cuff folds are formed due to the extra, unused material of the noncompliant cuff. These cuff folds create passageways for bacteria and other unwanted substances to travel around the tracheal tube and reach the lungs. These cuff folds can cause several complications, but the most common issue is ventilator associated pneumonia. Bacteria are able to freely colonize within these cuff folds because the cuff folds shield them from removal and treatment by clinicians. The bacteria then leaks down through the cuff folds into the lungs, causing the patient to contract pneumonia. Thus, elimination of cuff folds is a desirable goal of tracheal tube designs. 
         [0007]    To eliminate cuff folds and their associated problems, compliant cuffs can be used. These cuffs are made of an elastic material that can be inflated to a variety of tracheal diameters while maintaining a smooth seal between the cuff and the tracheal wall. The elastic material ensures a proper seal without cuff folds regardless of the tracheal diameter. However, the elastic material is often delicate and prone to tears or leaks. Therefore, the cuff wall of a compliant cuff is usually relatively thick, which then causes the cuff to require a higher pressure to properly inflate it. Additionally, since the clinician does not know the exact size of the given trachea, the cuff is generally inflated to a pressure that ensures that the trachea will be completely sealed regardless of the actual tracheal diameter. This higher pressure, which is exacerbated in patients with smaller tracheas, causes a corresponding amount of pressure to be applied to the tracheal wall. The high pressure can cause patient discomfort and, more seriously, tracheal ischemia and even necrosis. This danger is more severe when the endotracheal or tracheostomy tube is in place for a prolonged period of time. Tracheal ischemia is a restriction in blood supply to the tissues surrounding the cuff which causes a shortage of oxygen and glucose. If ischemia persists for a long period of time, the lack of nutrition will cause necrosis to occur and the tissue will die. The risk of ischemia is greater for tracheostomy tubes, as they are generally more permanent than endotracheal tubes. Therefore, while compliant cuffs create a proper seal against the tracheal wall, elimination of the high pressure on the tracheal wall is desired. 
         [0008]    Additionally, both compliant and noncompliant cuffs require regular maintenance to ensure proper continuous inflation. Compliant cuffs are made of highly permeable or semi-permeable materials, meaning the cuff deflates naturally at a high rate as air slowly leaks through the walls of the cuff. Thus, the pressure must be frequently checked to maintain a proper seal between the cuff and the tracheal wall. Even noncompliant cuffs, despite the use of materials with lower permeability such as PVC, still deflate eventually. Clinicians must check the cuff pressure every 4-8 hours to ensure proper continuous inflation. Often, this check is overlooked due to more critical responsibilities requiring the clinicians&#39; attention, causing the complications discussed above to become more frequent and severe. Thus, a cuff that requires less regular maintenance is desirable. 
       SUMMARY 
       [0009]    In one form of the present disclosure, a method of sealing a trachea is described. The method comprises inserting a tracheal tube that comprises an inflatable cuff into a trachea which comprises a tracheal wall. The inflatable cuff is comprised of a compliant material. The method also comprises inflating the inflatable cuff with a fluid to a first pressure that exceeds a second pressure necessary to create a seal between the inflatable cuff and the tracheal wall. The method also comprises deflating the inflatable cuff by releasing the first pressure to allow the fluid to flow out of the inflatable cuff without applying vacuum pressure to the fluid. The method also comprises evaluating a rate of change of pressure of the fluid in the inflatable cuff while the inflatable cuff is deflating. Additionally, the method includes identifying a variance in the rate of change of pressure corresponding to a third pressure at which the inflatable cuff at least partially separates from the tracheal wall. Additionally, the method comprises determining the second pressure by analyzing the third pressure and reinflating the inflatable cuff to the second pressure. In another embodiment, the steps of inflating and deflating the inflatable cuff can be repeated, wherein the third pressure is determined by analyzing a number of identified variances during the multiple deflating steps. In another embodiment, the second pressure is 0 to 50 centimeters of water more than the third pressure. 
         [0010]    In another embodiment, the method of sealing a trachea can also define the inflatable cuff as an outer cuff and the fluid as an outer cuff fluid. The tracheal tube can also comprise an inner cuff, wherein the outer cuff surrounds the inner cuff. The method can also comprise inflating the inner cuff with an inner cuff fluid after the step of inserting a tracheal tube. Also, the step of evaluating a rate of change of pressure can comprise measuring the rate of change of pressure of the inner cuff fluid while the outer inflatable cuff is deflating, where the rate of change of pressure of the inner cuff fluid is responsive to the rate of change of pressure of the outer cuff fluid. In another embodiment, the second pressure is 0 to 50 centimeters of water more than the third pressure. Additionally, the inner cuff fluid can be comprised of a gas. 
         [0011]    In another form of the present disclosure, a tracheal tube assembly is provided that comprises a tracheal tube with an outer surface, an air flow lumen, and an inflation lumen. The tracheal tube assembly also comprises an inflatable cuff that comprises an outer surface and a cavity, wherein the outer surface of the inflatable cuff is attached to the outer surface of the tracheal tube and the inflation lumen is connected to the cavity of the inflatable cuff. Additionally, the outer surface of the inflatable cuff comprises a muco-adhesive material. 
         [0012]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0013]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0014]      FIG. 1  is a pictorial representation of a tracheal tube and inflatable cuff constructed in accordance with the teachings of the present disclosure; 
           [0015]      FIG. 2  is an illustration of a tracheal tube and inflatable cuff assembly with a deflated single cuff; 
           [0016]      FIG. 3  is an illustration of a tracheal tube and inflatable cuff assembly with an inflated single cuff; 
           [0017]      FIG. 4  is a cross sectional view of a tracheal tube with a single inflatable cuff; 
           [0018]      FIG. 5  is a pictorial representation of a step of inflating a single cuff; 
           [0019]      FIG. 6  is another pictorial representation of a step of inflating a single cuff; 
           [0020]      FIG. 7  is another pictorial representation of a step of inflating a single cuff; 
           [0021]      FIG. 8  is an illustration of various muco-adhesive material patterns that can be applied to an inflatable cuff; 
           [0022]      FIG. 9  is an illustration of a porous cuff filled with an aqueous-jelly solution; 
           [0023]      FIG. 10  is an illustration of a tracheal tube and inflatable cuff assembly with a deflated double cuff; 
           [0024]      FIG. 11  is an illustration of a tracheal tube and inflatable cuff assembly with an inflated double cuff; 
           [0025]      FIG. 12  is a cross sectional view of a tracheal tube with a double inflatable cuff; 
           [0026]      FIG. 13  is a pictorial representation of a step of inflating a double cuff; 
           [0027]      FIG. 14  is another pictorial representation of a step of inflating a double cuff; 
           [0028]      FIG. 15  is another pictorial representation of a step of inflating a double cuff; and 
           [0029]      FIG. 16  is another pictorial representation of a step of inflating a double cuff. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. It should also be understood that various cross-hatching patterns used in the drawings are not intended to limit the specific materials that may be employed with the present disclosure. The cross-hatching patterns are merely exemplary of preferable materials or are used to distinguish between adjacent or mating components illustrated within the drawings for purposes of clarity. 
         [0031]    The present invention addresses the aforementioned shortcomings associated with tracheal tubes. This invention combines the advantages of compliant cuffs and noncompliant cuffs while limiting their respective disadvantages. The present invention reduces or eliminates cuff folds while maintaining a low pressure seal against the tracheal wall that decreases the likelihood of tracheal ischemia. Additionally, this invention reduces the amount of regular maintenance required for tracheal tubes by providing a cuff that maintains an adequate fluid pressure for an extended period of time. 
         [0032]    While this disclosure refers only to tracheal tubes in detail, inflatable cuffs as described in this disclosure can be used in conjunction with a multitude of other medical devices that involve the sealing of an anatomical structure that is cylindrical or tubular in shape. For example, this invention may be used with esophageal, vascular, and other applications. The product or method described herein may also be used for the sizing of vessels, such as the aorta. 
         [0033]      FIG. 1  shows a tracheal tube  2  with an inflatable cuff  4  in a patient&#39;s trachea  6 . In this example, the tracheal tube  2  is an endotracheal tube, but in other embodiments the tracheal tube  2  can be a tracheostomy tube. The inflatable cuff  4  can have multiple layers, or cuffs, within the inflatable cuff  4 . In this example, the inflatable cuff  4  is fully inflated to create a seal between the inflatable cuff  4  and the tracheal wall  8 , thus preventing unwanted fluids and substances from leaking between the inflatable cuff  4  and the tracheal wall  8  down to the lungs. 
         [0034]      FIGS. 2 and 3  show one embodiment of the invention. In this embodiment, a single cuff  10  is attached to the tracheal tube  2 .  FIG. 2  shows the single cuff  10  in a deflated state and  FIG. 3  shows the single cuff  10  in an inflated state. The tracheal tube  2  has a lumen  12  that regulates the passage of air into and out of the lungs. The single cuff  10  surrounds the tracheal tube  2  and connects to the tracheal tube  2  at two points: a distal connection point  14  and a proximal connection point  16 . The single cuff  10  may be bonded to the tracheal tube  2  using an adhesive or any other type of bonding method that prevents or limits fluid leakage from the single cuff  10 . The single cuff  10  is ideally made of a compliant material, preferably silicone. However, the material may also be, but is not limited to, elastomeric materials such as latex, rubber, and polyurethane. Compliance is a measure of the maximum percentage a given material can elastically expand beyond its non-stressed state while still allowing it to revert back to its non-stressed form. Compliant balloons typically have a compliance range of 20 to 500 percent; however that range can vary depending on the specific application of the balloon. In some cases, the compliance can be greater than 500 percent. 
         [0035]    Still referring to  FIGS. 2 and 3 , the single cuff  10  may be inflated and deflated with a fluid  24  using an inflation lumen  18 . The inflation lumen  18  may extend from the single cuff  10  to a point external from the patient where a clinician may easily access it. In this embodiment, the fluid  24  is a liquid, ideally saline or water. A liquid is preferred because of the slower rate at which a liquid would permeate through the wall of the single cuff  10 . A liquid filled single cuff  10  will maintain an adequate pressure for a longer period of time than if the single cuff  10  was filled with gas. However, other liquids or fluids, including gases, may be used as long as the fluid  24  is sterile. The fluid pressure of the single cuff  10  is measured using a pressure measurement device  20 , such as a pressure gauge or meter. A flow meter can also be used that detects the rate of flow of the fluid  24  in and out of the single cuff  10 . The single cuff  10  may be inflated or deflated with a syringe  22  filled with the fluid  24  and connected to the inflation lumen  18 . 
         [0036]      FIG. 4  shows a cross section view of the single cuff  10  within the trachea  8  while the single cuff  10  is inflated and deflated. As can be seen, because the single cuff  10  is made of a compliant material, when it is inflated with the fluid  24 , a smooth seal is made between the tracheal wall  8  and the single cuff  10 . Thus, unwanted substances or fluids are prevented from traveling around the single cuff  10  and down towards the lungs. 
         [0037]    In this embodiment, the single cuff  10  is preferably inflated in a particular way to ensure a proper seal between the single cuff  10  and the tracheal wall  8 .  FIGS. 5, 6, and 7  show the steps of this process. First, referring to  FIG. 5 , the tracheal tube  2 , with the single cuff  10  deflated, is inserted into the trachea  6  through the patient&#39;s mouth. Once the tracheal tube  2  is in position, the single cuff  10  is inflated via the inflation lumen  18  with the syringe  22 . The single cuff  10  is inflated with a fluid  24 , ideally a liquid. As the single cuff  10  is inflated, the fluid pressure of the single cuff  10  is continuously monitored using a pressure measurement device  20 . 
         [0038]    Now referring to  FIG. 6 , the single cuff  10  is inflated to a pressure greater than the pressure necessary to create a seal between the single cuff  10  and the tracheal wall  8 . The pressure necessary to create a seal is unknown at this point since the tracheal diameter is unknown, so the single cuff  10  is overinflated to a pressure high enough to create a seal for even the largest tracheas. This pressure varies based on the material used for the cuff and the corresponding elasticity of the material. Once the single cuff  10  is overinflated, the single cuff  10  is deflated by releasing the pressure applied to the single cuff  10  to allow the fluid  24  to flow out of the single cuff  10 . Ideally, the pressure is released by removing the force initially applied to the syringe  22  inflate the single cuff  10  and allowing the fluid  24  to flow back into the syringe  22 . Alternatively, the pressure can be released by opening a valve  25  attached to the inflation lumen  18  and allowing the fluid  24  to flow through the valve  25 . Due to the high pressure in the single cuff  10 , the fluid  24  will naturally flow back into the syringe  22  or through the valve  25 , thereby gradually deflating the single cuff  10 . 
         [0039]    When deflating the single cuff  10  by allowing the fluid  24  to flow back into the syringe  22 , the single cuff  10  will ideally deflate at a steady rate. To ensure a steady rate, the sliding friction between the syringe  22  and the plunger  26  must be low. If the sliding friction is too high, the fluid  24  will not naturally flow back into the syringe  22 . To reduce the sliding friction, the syringe  22  is ideally a glass or plastic syringe with a rubber plunger  26 . In another potential embodiment, the syringe  22  is made of glass with a fitted tungsten or stainless steel plunger  26 . Additionally, the plunger  26  may be coated with a fluoropolymer, silicone oil, mineral oil, or some other lubricant to reduce the sliding friction between the plunger  26  and the wall  28  of the syringe  22 . 
         [0040]    Now referring to  FIG. 7 , as the single cuff  10  is deflating, the pressure of the fluid  24  in the single cuff  10  is continuously monitored using the pressure measurement device  20 . The fluid pressure will steadily drop as the single cuff  10  deflates. Eventually, the single cuff  10  will begin to separate from the tracheal wall  8 . As this separation begins, the single cuff  10  will tend to resist separating from the tracheal wall  8  because the single cuff  10  has adhered to the tracheal wall  8 . However, as the single cuff  10  continues to deflate, the elastic material of the single cuff  10  will naturally tend to contract to its non-expanded form. Thus, the single cuff  10  will eventually separate from the tracheal wall  8 . At this separation point, the pressure of the single cuff  10 , as measured by the pressure measurement device  20 , may increase suddenly due to the elastic material of the single cuff  10  suddenly separating from the tracheal wall and returning to its non-expanded state. This sudden contraction causes a sudden decrease in the volume of the single cuff  10  and a corresponding increase in pressure. Alternatively, rather than increasing suddenly, the pressure of the single cuff  10  may remain constant for a short period of time at the separation point. While to this point the rate of change in pressure of the fluid  24  remains relatively constant during the deflation of the single cuff  10 , the separation point represents a variance in the rate of change of the fluid pressure. After the separation point, the single cuff  10  will resume deflating at a relatively constant rate, albeit at a slower rate than before the separation point due to the lower pressure of the fluid  24  after separation. The difference in the rate of change of pressure in the single cuff  10  before and after the separation point provide an additional, measurable variance in the rate of change of the pressure of the fluid  24 . Due to this variance, the separation point can be found and the pressure of the fluid  24  at the separation point is recorded. For increased accuracy, the single cuff  10  can be inflated and deflated multiple times to find the separation point and the corresponding fluid pressure in the single cuff  10 . The separation point corresponds to the point at which the single cuff  10  is applying zero pressure to the tracheal wall  8 , but still contacting it. 
         [0041]    Based on the separation point and the corresponding pressure of the fluid  24  in the single cuff  10 , the clinician can determine to what pressure to inflate the single cuff  10 . To achieve a seal between the tracheal wall  8  and the single cuff  10 , the single cuff  10  should be inflated, at a minimum, to the pressure of the fluid  24  at the separation point. However, to ensure that there is a proper seal the single cuff  10  is ideally inflated to a point where the pressure of the fluid  24  is 5 to 50 cm H 2 O greater than the pressure at the separation point, although that range can be adjusted. To prevent patient discomfort and tracheal ischemia, the single cuff  10  should not be inflated to a pressure much greater than the given range. Since clinicians do not know the tracheal diameter of any given patient, the separation point allows clinicians to accurately determine the pressure needed to create a proper seal for each individual patient. Therefore, this process lessens the risk of over pressurizing the single cuff  10  and causing patient discomfort and ischemia. Additionally, this process ensures a proper seal between the single cuff  10  and the tracheal wall  8 . 
         [0042]    For there to be a measurable separation point and a corresponding pressure jump or pressure pause of the fluid  24 , the single cuff  10  is ideally made of a material that adheres to the tracheal wall  8 . While silicone, the material used for the single cuff  10  in the present embodiment, will adhere at least partially to the tracheal wall  8 , another material can be used to increase the adherence and thereby enhance the visibility of the separation point. To achieve adherence, materials with muco-adhesive properties may be used. Muco-adhesiveness is a measure of the ability of a material to adhere to a mucosal layer. The mucosal layer, a viscoelastic fluid made primarily of mucus, lines the exposed surfaces of internal organs, such as the tracheal wall  8 . Thus, using muco-adhesive materials with the single cuff  10  will cause the single cuff  10  to adhere to the tracheal wall  8 . As the muco-adhesiveness of the outer layer of the single cuff  10  increases, the single cuff&#39;s  10  adherence to the tracheal wall  8  increases. Correspondingly, the pressure jump of the fluid  24  will be more visible to the operator. Examples of muco-adhesive materials that can be used to enhance the visibility of the separation point include, but are not limited to, anionic polymers such as polyacrylic acid, polymethacrylic acid, carboxymethylcellulose, sodium aliginate, poly[(maleic acid)-co-(vinyl methyl ether)], carbomer, and carbopol polymers. Additionally, cationic polymers such as chitosan and polymethacrylates, amphoteric polymers such as gelatin and N-carboxymethylchitosan, and polymeric thiomers such as conjugates of poly (acrylic acid)/cysteine, chitosan/N-acetylcysteine, alginate/cysteine, chitosan/thioglycolic acid, and chitosan/thioethylamidine may be used. Additional materials that may be used include amylose, amylopectin, fibrin glue, porcine small intestinal submucosa, and hydroxypropyl methyl cellulose. 
         [0043]    However, most of the muco-adhesive materials discussed above are noncompliant or semi-compliant, making them unideal materials for the single cuff  10 , as a compliant material is preferred. Thus, rather than using the muco-adhesive materials for the single cuff  10 , a muco-adhesive layer  30  may be bonded to the compliant single cuff  10  using various patterns or markings as shown in  FIG. 8 . Potential patterns used for the muco-adhesive layer  30  can include, but are not limited to, dots, various hatches, and lines. In this situation, the single cuff  10  is still primarily made of silicone or some other compliant material, while the muco-adhesive layer  30  has a pattern that enhances the visibility of the separation point without compromising the compliancy of the single cuff  10 . Alternatively, the muco-adhesive layer  30  may be applied to the compliant single cuff  10  in a solid layer that is thin enough to allow unimpeded cuff expansion upon inflation while allowing adequate cuff compliance to occur. The acceptable thickness of a solid muco-adhesive layer  30  depends on the muco-adhesive material used as well as the material used for the single cuff  10 . Additionally, while the muco-adhesive layer  30  may adhere to the tracheal wall  8 , the muco-adhesive layer  30  may not properly bond to the single cuff  10  because of material incompatibilities. Therefore, a tye, or intermediate, layer may be used between the single cuff  10  and the muco-adhesive layer  30  to ensure all layers are properly bonded together. 
         [0044]    In another embodiment of the invention, a porous cuff  32  made of a compliant material is provided as shown in  FIG. 9 . The porous cuff  32  has pores  34  that allow the weeping of a fluid through the porous cuff  32 . Ideally, the cuff will have a porosity between 0.00001% and 0.5%, which refers to the percentage of the porous cuff  10  that is open air. The porosity is ideally high enough to allow a fluid to weep through the porous cuff  32 , but not so high that the porous cuff  32  deflates at an undesirable rate. The porous cuff  32  may be inflated with an aqueous-jelly solution  36 . This aqueous-jelly solution  36  can be made of two parts: a liquid  38  and a water soluble lubricating jelly  39 . The liquid  38  must be sterile, preferably saline or water. The water soluble lubricating jelly  39  is a sterile, gelatinous substance that can be dissolved in an aqueous solution. The water soluble lubricating jelly  39  can be made of, but is not limited to, glycerol, carboxymethyl cellulose, hypromellose, and propylene glycol. 
         [0045]    The ratio of the liquid  38  to the water soluble lubricating jelly  39  preferably ranges from 75% liquid  38  and 25% water soluble lubricating jelly  39  to 25% liquid  38  and 75% water soluble lubricating jelly  39 . When the porous cuff  32  is filled with the aqueous-jelly solution  36 , the aqueous-jelly solution  36  will weep through the pores  34  in the porous cuff  32  into the trachea  6 . Once in the trachea  6 , the water soluble lubricating jelly  39  acts as an adhesive or bonding agent that fills any existing gaps between the tracheal wall  8  and the porous cuff  32 . The aqueous-jelly solution  36  may also be used to fill the single cuff  10  of the previous embodiment. The mixture may help lessen the rate at which the fluid  24  would permeate through the single cuff  10 . 
         [0046]    Another embodiment of the invention is shown in  FIGS. 10 and 11 . In this embodiment, a tracheal tube  40  with an inflatable cuff  42  is shown.  FIG. 10  shows the inflatable cuff  42  in a deflated state, while  FIG. 11  shows the inflatable cuff  42  fully inflated. The tracheal tube  40  has a lumen  44  that regulates the passage of air into and out of the lungs. The inflatable cuff  42  surrounds the tracheal tube  40  and has two layers: an inner cuff  46  and an outer cuff  48 . The inner cuff  46  is ideally made of a noncompliant or semi-compliant material, such as nylon, polyvinyl chloride (PVC), polyethylene, or polyethylene terephthalate. Noncompliant balloons typically have a compliance range of 0 to 10 percent. Semi-compliant balloons typically have a compliance range of 5 to 30 percent. However these ranges may vary depending on the specific application of each balloon. The outer cuff  48  is ideally made of a compliant material, such as silicone, latex, rubber, or polyurethane. As discussed above, compliant balloons typically have a compliance of 20 to 500 percent; however this range may vary. The inner cuff  46  and outer cuff  48  are bonded to the tracheal tube  40  using an adhesive or any other type of bonding method that prevents or limits fluid leakage from the inflatable cuff  42 . The inner cuff  46  has two connection points to the tracheal tube  40 : a distal inner cuff connection point  50  and a proximal inner cuff connection point  52 . The outer cuff  48  has two connection points to the tracheal tube  40 : a distal outer cuff connection point  54  and a proximal outer cuff connection point  56 . Ideally, the distal outer cuff connection point  54  is more distal than the distal inner cuff connection point  50  and the proximal outer cuff connection point  56  is more proximal than the proximal inner cuff connection point  52  so that the outer cuff  48  completely surrounds the inner cuff  46 . 
         [0047]    Still referring to  FIGS. 10 and 11 , the inner cuff  46  may be inflated and deflated using an inner inflation lumen  58 , and the outer cuff  48  may be inflated and deflated using an outer inflation lumen  60 . The inner inflation lumen  58  and outer inflation lumen  60  may extend from their respective cuffs to a point external from the patient where the clinician may easily access them to inflate and deflate the cuffs. 
         [0048]    In this embodiment, the inner cuff  46  is inflated with a fluid via the inner inflation lumen  58  using a manometer  62 . Air or some other gas is preferable over a liquid because gasses are more responsive to slight changes in pressure, meaning any variance in pressure will be more easily detected than if a liquid is used; however, liquids may be used. The manometer  62  has the dual function of inflating the inner cuff  46  and measuring the air pressure of the inner cuff  46 . However, other pressure measurement and inflation devices may be used. The outer cuff  48  is inflated with a fluid  66 . While the fluid  66  is ideally a liquid, such as water or saline, gases may be used. The outer cuff  48  may be inflated via the outer inflation lumen  60  with the use of a syringe  64  filled with the fluid  66 . 
         [0049]      FIG. 12  shows a cross sectional view of the inflatable cuff  42  with the inflatable cuff  42  both inflated and deflated. As can be seen, when the outer cuff  48  is fully inflated, a proper seal between the outer cuff  48  and the tracheal wall  68  is achieved because the outer cuff  48  is made of a compliant material. Additionally, the inner cuff  46 , made of a noncompliant or semi-compliant material, may still have cuff folds when the inflatable cuff  42  is inflated, but the cuff folds have no effect on the seal between the outer cuff  48  and the tracheal wall  68 . Since there are no cuff folds on the outer cuff  48 , passageways for bacteria and other unwanted substances are eliminated. 
         [0050]    To ensure that a proper seal is created between the inflatable cuff  42  and tracheal wall  68 , the inflatable cuff  42  must be inflated in a particular way.  FIGS. 13-16  show this process in detail. Referring to  FIG. 13 , the tracheal tube  40  is first inserted into the trachea  70  through the patient&#39;s mouth. During this step, both the outer cuff  48  and the inner cuff  46  are deflated. 
         [0051]    Now referring to  FIG. 14 , the inner cuff  46  is over-inflated via the inner inflation lumen  58  with air using a manometer  62  to a pressure of over 80 cm H 2 O. While the over-inflation step is not critical to the process, it ensures that any folds or air pockets in the deflated inner cuff  46  will not cause inaccuracies in future pressure measurements. The inner cuff  46  is then deflated to a low pressure, ideally between 20 and 32 cm H 2 O. 
         [0052]    Referring to  FIG. 15 , the outer cuff  48  is then inflated via the outer inflation lumen  60  with a fluid  66 , ideally a liquid. In this embodiment, the fluid  66  is a saline solution; however, other liquids such as water or any other sterile liquid may be used. Using a liquid rather than a gas to inflate the outer cuff  48  ensures that the inflatable cuff  42  will stay inflated for a longer period of time because a liquid will not permeate through the outer cuff  48  as quickly as a gas. The fluid  66  can be placed within a syringe  64  and may then be injected into the outer cuff  48  through the outer inflation lumen  60 . While the outer cuff  48  is being inflated, the air pressure of the inner cuff  46  may be continuously monitored using the manometer  62 . The outer cuff  48  is inflated to a pressure greater than the pressure necessary to create a seal between the inflatable cuff  42  and the tracheal wall  68 . Since this pressure is unknown, the outer cuff  48  is overinflated as indicated by the pressure change in the inner cuff  46 . As the outer cuff  48  is inflated, the increased pressure against the inner cuff  46  by the outer cuff  48  causes the pressure in the inner cuff  46  to increase. The outer cuff  48  is ideally inflated to a point where the pressure in the inner cuff  46  is over 100 cm H 2 O, although that range can be adjusted based on factors such as the materials and fluids used. 
         [0053]    Now referring to  FIGS. 15 and 16 , once the outer cuff  48  is overinflated, the outer cuff  48  is then deflated by releasing the pressure applied to the outer cuff  48  to allow the fluid  66  to flow out of the outer cuff  48 . Ideally, the pressure is released by removing the force initially applied to the syringe  64  to inflate the outer cuff  48  and allowing the fluid  66  to flow back into the syringe  64 . Alternatively, the pressure can be released by opening a valve  67  attached to the outer inflation lumen  60 . Due to the high pressure in the outer cuff  48 , the fluid  66  will naturally flow out of the outer cuff  48  and back into the syringe  64  or through the valve  67 , thereby slowly deflating the outer cuff  48 . 
         [0054]    When deflating the outer cuff  48  by allowing the fluid  66  to flow back into the syringe  64 , the outer cuff  48  will ideally deflate at a steady rate. To ensure a steady rate, the sliding friction between the syringe  64  and the plunger  70  must be low. If the sliding friction is too high, the fluid  66  will not naturally flow back into the syringe  64 . To reduce the sliding friction, the syringe  64  is ideally a glass or plastic syringe with the plunger  70  made of rubber. In another potential embodiment, the syringe  64  is glass with a fitted tungsten or stainless steel plunger  70 . Additionally, the plunger  70  may be coated with a fluoropolymer, silicone oil, mineral oil, or some other lubricant to reduce the sliding friction between the plunger  70  and the wall  72  of the syringe  64 . 
         [0055]    Referring to  FIG. 16 , as the outer cuff  48  is deflating, the pressure of the inner cuff  46  is continuously monitored using the manometer  62 . The pressure of the inner cuff  46  will steadily drop as the outer cuff  48  deflates. Eventually the outer cuff  48  will begin to separate from the tracheal wall  68 . As this separation begins, the outer cuff  48  will tend to resist separating from the tracheal wall  68  because the outer cuff  48  has adhered to the tracheal wall  68 . However, as the outer cuff  48  continues to deflate, the elastic material of the outer cuff  48  will naturally tend to contract to its non-expanded form. Thus, the outer cuff  48  will eventually separate from the tracheal wall  68 . At this separation point, the pressure of the inner cuff  46 , as measured by the manometer  62 , may increase suddenly due to the elastic material of the outer cuff  48  suddenly separating from the tracheal wall  68  and returning to its non-expanded state. This sudden contraction may cause a sudden decrease in the volume of the outer cuff  48  and a responsive increase in pressure of the inner cuff  46 . Alternatively, rather than increasing suddenly, the pressure of the inner cuff  46  may remain constant for a short period of time at the separation point. While the rate of change in pressure of the outer cuff  48  and the inner cuff  46  remains relatively constant during the deflation of the outer cuff  48 , the separation point represents a variance in the rate of change of the pressure of the fluid  66 . After the separation point, the outer cuff  48  will resume deflating at a relatively constant rate, albeit at a slower rate than before the separation point due to the lower pressure of the fluid  66  after separation. The difference in the rate of change of pressure in the outer cuff  48  and the inner cuff  46  before and after the separation point provide an additional, measurable variance in the rate of change of the pressure of the fluid  66 . Due to this variance, the separation point can be found and the pressure of the inner cuff  46  at the separation point is recorded. For increased accuracy, the outer cuff  48  can be inflated and then deflated multiple times to find the separation point and the corresponding pressure of the inner cuff  46 . The separation point corresponds to the point at which the outer cuff  48  is applying zero pressure to the tracheal wall  68 , but still contacting it. 
         [0056]    Based on the separation point and the corresponding pressure of the inner cuff  46 , the clinician is able to determine to what pressure to inflate the outer cuff  48 . To achieve a seal between the tracheal wall  68  and the outer cuff  48 , the outer cuff  48  should be inflated, at a minimum, to the point where the pressure of the inner cuff  46  equals the pressure of the inner cuff  46  at the separation point. However, to ensure that there is a proper seal the outer cuff  48  is ideally inflated to a point where the pressure of the inner cuff  46  is 5 to 50 cm H 2 O greater than the pressure at the separation point, although that range can be adjusted. To prevent patient discomfort and tracheal ischemia, the outer cuff  48  should not be inflated to a pressure much greater than the given range. Since clinicians do not know the tracheal diameter of any given patient, the separation point allows clinicians to accurately determine the pressure needed to create a proper seal for each individual patient. Therefore, this process lessens the risk of over pressurizing the inflatable cuff  42  and causing patient discomfort and ischemia. Additionally, this process ensures a proper seal without cuff folds between the inflatable cuff  42  and the tracheal wall  68 . 
         [0057]    For there to be a measurable separation point and a corresponding pressure jump or pressure pause in the inner cuff  46 , the outer cuff  48  is ideally made of a material that adheres to the tracheal wall  68 . As discussed in a previous embodiment and shown in  FIG. 8 , muco-adhesive materials can be used, either as part of the outer cuff  48  or as an additional layer on top of the outer cuff  48 . The muco-adhesive layers or patterns can enhance the visibility of the separation point for clinicians performing this procedure. 
         [0058]    In another embodiment, the outer cuff  48  can be made of a porous material such as the porous cuff  32  described in  FIG. 9 . Additionally, the fluid used to inflate the outer cuff  48  can be an aqueous-jelly solution of  FIG. 9  that is designed to weep through the outer cuff  48  into the trachea  70 . The aqueous-jelly solution can then act as an adhesive or bonding agent that helps ensure a proper seal between the tracheal wall  68  and the outer cuff  48 . 
         [0059]    The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.