Patent Application
20080078406
Advantages of the invention may become apparent upon reading the following detailed description and upon reference to the drawings in which:
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
It is desirable to provide a medical device that is resistant to the buildup of mucus or other materials that offers a non-invasive buildup resistance mechanism that does not involve regular maintenance. In accordance with some aspects of the present invention, an endotracheal tube is provided that includes an adhesion-resistant material adapted to reduce mucus and/or microbe adhesion to the surfaces of the tube. This adhesion-resistant material may function to prevent the accumulation of mucus on the interior surface of the endotracheal tube, thereby maximizing the cross-sectional area within the tube through which the patient may breathe. Additionally, in certain embodiments, the lubricious qualities of the adhesion-resistant material may also decrease the coefficient of friction of fluids, such as gas, being transferred in the tube. This, in turn, may function to minimize the patient's work of breathing, positively impacting the comfort of the patient. Further, such endotracheal tubes may also provide the advantage of reduced microbe adhesion and/or buildup on the surfaces of the tube, which may reduce related clinical complications. For example, many types of bacteria adhere more readily to hydrophobic surfaces. Thus, reducing the hydrophobicity of the endotracheal tube's fluid passageway may make the tube more adhesion-resistant to microbes. Preventing the initial adhesion of microbes to the inside surface of the tube may in turn prevent or reduce biofilm formation on the inside surface of the tube.
The adhesion-resistant materials may be used in conjunction with any suitable medical device. In certain embodiments, the adhesion-resistant materials as provided herein may be used in conjunction with a catheter, a stent, a feeding tube, an intravenous tube, an endotracheal tube, a tracheostomy tube, a circuit, an airway accessory, a connector, an adapter, a filter, a humidifier, a nebulizer, or a prosthetic.
An example of a medical device including an adhesion-resistant material is an endotracheal tube 10, as depicted in
The adhesion-resistant layer 14 may be disposed on all or a portion of the inner surface of the conduit 16. For example, in certain embodiments, it may be advantageous dispose the adhesion-resistant layer 14 towards the distal end 17 of the conduit 16, as mucus being coughed into the conduit 16 from the lungs may first enter the distal end 17. Generally, the adhesion-resistant layer 14 may be sufficiently thick to cover an inner surface of the conduit 16 while not being so thick as to significantly impact the flow of fluid through the fluid passageway 13. In certain embodiments, the adhesion-resistant layer 14 may be less than 1 mm thick. For example, an extruded layer may be 0.0001 inches in thickness. It may also be advantageous to employ a nonswellable adhesion-resistant layer 14 in order to minimize the effect of the adhesion-resistant layer 14 on the inner diameter reduction of the fluid passageway 13. However, a swellable adhesion-resistant layer 14 may be used in which any swelling is limited or constrained, or in embodiments in which the layer 14 is sufficiently thin that swelling will have a negligible effect on the inner diameter of the conduit 16.
In one embodiment, the adhesion-resistant layer 14 may be characterized by its degree of hydrophilicity. A hydrophilic adhesion-resistant layer 14 may be advantageous, as many types of bacteria adhere more readily to hydrophobic surfaces. One such measure of hydrophilicity is a contact angle measurement, done by, for example, the sessile drop method. On hydrophilic surfaces, a water droplet will spread out over a larger area than on a hydrophobic surface. The contact angle is the angle at which a liquid/vapor interface meets the solid surface. The shape of the droplet may be determined by the Young-Laplace equation. On many hydrophilic surfaces, water droplets will exhibit contact angles of 0° to 40°. For example, certain hydrogels may be so hydrophilic that water disappears on their surfaces. Such materials may be considered to have a water contact angle of zero. On hydrophobic surfaces, which are resistant to water, one observes a large contact angle (70° to 90°). Thus, the adhesion-resistant layer 14 may have a water contact angle of less than 40° or between 10° to 30°. It should be understood that a generally hydrophilic material, such as a polyethylene glycol, may also include hydrophobic elements, such as a hydrophobic backbone. Further, in certain embodiments the hydrophilic surface may have surface chemistries which provide surface energies not favorable for deposition (for example surface treatments to covalently bind hydrophilic compounds, including ammonia, oxygen, proteins or polysaccharides to the surface), and also a physical steric hindrance effect, where polymer/oligomer chains make it difficult for microbial adhesion to occur. Thus, highly branched hydrophilic materials, such as polyethylene glycols, may be advantageous for use as adhesion-resistant materials.
In certain embodiments, the adhesion-resistant layer 14 may be characterized by its coefficient of friction against the flow of gas through the conduit 16. Generally, the adhesion-resistant layer 14 may exhibit decreased friction and resistance to gas flow as compared to the relatively hydrophobic material of the conduit 16. Airway resistance is the opposition to gas flow caused by the forces of friction. Resistance to flow in the airways depends on whether the flow is laminar or turbulent, the dimensions of the airway, and the viscosity of the gas. For laminar flow, resistance is quite low. That is, a relatively small driving pressure is needed to produce a certain flow rate.
In other embodiments, the adhesion-resistant layer 14 may be characterized by the adhesion-resistant material from which it is formed. For example, the adhesion-resistant layer 14 may include polyethylene glycols (e.g. BASF Pluronics F-127), polyethylene oxides, polyvinyl alcohols (e.g. Supersorb ionic vinyls), polyalkylene glycols, alkoxy polyalkylene glycols, polysaccharides, polyvinylpyrrolidones, polyacrylic acids, polyacrylamides, polymaleic anhydrides, or copolymers thereof and mixtures thereof. In embodiments in which the material used to form the adhesion-resistant layer is insufficiently hydrophilic, a plasma treatment may be employed to alter the surface chemistry of the adhesion-resistant layer so that its water contact angle is less than 30°.
The cuff 12 may be formed from materials having suitable mechanical properties (such as puncture resistance, pin hole resistance, tensile strength), chemical properties (such as forming a suitable bond to the tube 16), and biocompatibility. In one embodiment, the walls of the inflatable cuff 12 are made of polyurethane having suitable mechanical and chemical properties. An example of a suitable polyurethane is Dow Pellethane® 2363-80A. In another embodiment, the walls of the inflatable cuff 12 are made of a suitable polyvinyl chloride (PVC). Suitable materials may also include polyethylene teraphthalate (PETP), low-density polyethylene (LDPE), polypropylene, silicone, neoprene, or polyisoprene. Typically, endotracheal cuffs are inflated within a patient's trachea such that the intra cuff pressure is approximately 20-30 cm H2O. Endotracheal cuffs utilizing inflation pressures significantly greater than 25 cm H2O, such as 100 cm H2O, may be referred to as high-pressure cuffs, while cuffs that are designed to be inflated at pressures less than 25 cm H2O may be considered low-pressure cuffs.
The adhesion-resistant layer 14 may be manufactured and applied to the cuff 12 by any suitable technique. For example, the adhesion-resistant layer 14 may be co-extruded with the conduit 16.
In other embodiments, the adhesion-resistant layer 14 may be applied to the conduit by radio frequency-oxygen (RF—O2) glow discharge or plasma treatments. Such techniques may be particular useful in embodiments in which the adhesion-resistant layer 14 is substantially thinner than the conduit 16. For example, an adhesion-resistant layer 14 may be only a few microns in thickness when applied by a radio frequency-oxygen (RF—O2 glow discharge technique) or any other appropriate plasma or chemical vapor deposition surface treatment. In certain embodiments, the adhesion-resistant layer may also include an adhesion layer or a tie layer. As shown in
In other embodiments, as shown in
The endotracheal tube 10 of the present invention may be incorporated into systems that facilitate positive pressure ventilation of a patient, such as a ventilator. These systems may include connective tubing, a gas source, a monitor, and/or a controller. The controller may be a digital controller, a computer, an electromechanical programmable controller, or any other control system.
While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
