News Column

Patent Issued for Endotracheal Tube Cuff Inflation Device and Methods

May 27, 2014



By a News Reporter-Staff News Editor at Journal of Technology -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Stanhope, Rawley (Dover, NJ); Close, Brandon W. (Olathe, KS), filed on November 30, 2010, was published online on May 13, 2014.

The assignee for this patent, patent number 8721589, is Spiritus Technologies, LLC (Lenexa, KS).

Reporters obtained the following quote from the background information supplied by the inventors: "Healthcare professionals in General Anesthesia, Intensive Care and Emergency Medicine use over 60 million ETTs a year to manage patient airways. The vast majority of ETTs utilize an inflatable cuff that forms a pneumatic seal with the patient's trachea to prevent air leakage and aspiration during patient ventilation after the ETT has been placed in the patient's trachea through intubation. Multiple studies suggest that maintaining cuff pressure at 20-30 cm H2O is critical for patient safety; pressures below 20 cm H2O have been shown to increase the risk of Ventilator Associated Pneumonia (VAP) and pressures above 30 cm H2O are associated with a higher risk of stenosis, ischemia and rupture of the trachea. Despite the severity and high costs of these complications, unsafe cuff pressures have been observed in over half of intubated patients at numerous hospitals and EMT units.

"There are two conventional techniques to inflate an ETT cuff: (1) subjective feedback based on the pressure of the external palpation balloon and (2) inflating a set volume of air based on the selected cuff size. These methods have been shown to be inaccurate even in the hands of experienced professionals. Studies comparing hospitals with high and low rates of unsafe cuff pressures have found that hospitals using pressure meters to check cuff pressure upon inflation outperformed hospitals relying on conventional techniques utilizing no peripheral instrumentation.

"Some hospitals use a Cufflator or similar blood pressure meter to measure and monitor cuff pressure. The Cufflator is an analog pressure gauge attached to a compressible rubber handle that, when squeezed, acts as a bellow and inflates the cuff. The Cufflator is bulky, expensive, and has been shown to be inaccurate by as much as 4 cm H2O. Consequently, many hospitals prefer to use blood pressure meters in conjunction with a T-valve and a syringe. Although less expensive and more accurate than the Cufflator, connecting these three devices together to inflate the cuff introduces more procedural time. Set-up time aside, both the Cufflator and blood pressure meter require training; (1) users must know the proper pressure to leave the cuff and (2) users must know to inflate the cuff to an excessively high pressure before lowering it to the final pressure. The latter requirement is an accepted practice of experienced Respiratory Therapists to establish a creaseless seal between the cuff and the trachea.

"U.S. Pat. Nos. 4,367,739, 4,370,982, 5,074,443, 5,270,685, 5,163,904, 4,064,879, 4,624,659, 4,475,906, 6,605,064, 4,178,938 4,178,940, and 5,015,233, the entire disclosures of which are incorporated herein by reference, illustrate several prior art syringes and other apparatuses that have been used for inflating ETT cuffs and which suffer from the disadvantages discussed above. Therefore, it would be beneficial to provide an accurate, reliable, and/or cost efficient means to automatically establish a safe ETT cuff pressure.

"There is a long-felt, unmet need for an improved apparatus and related methods for inflating an ETT cuff to a safe pressure. The present general inventive concept provides an accurate, reliable, and/or cost efficient means to automatically establish a safe ETT cuff pressure with a single full stroke of the syringe."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "According to one aspect, an endotracheal tube cuff inflation device is provided. The device includes a syringe body and a syringe plunger slidably positioned within the syringe body for creating a fluid (air) pressure within said body. It further includes a high pressure valve for releasing an excess volume of fluid (air) from the body once the fluid pressure within the body reaches a predetermined high pressure limit and to temporarily maintain it. It further includes a low pressure valve for releasing fluid (air) pressure from the body, after the high pressure limit has been maintained, to reduce the fluid (air) pressure within the body from the predetermined high pressure limit to a predetermined low pressure limit. In some embodiments, the high pressure and low pressure valves are embedded within the body. In other embodiments, the high pressure valve is embedded within the plunger. It will be appreciated that in alternative embodiments, the low pressure valve may be embedded within the plunger (either alone, or in combination with the high pressure valve).

"According to a second aspect, an endotracheal tube cuff inflation device is provided. The device includes a syringe plunger sized and shaped to slide along the inside of a syringe body. The plunger includes an end sized and shaped to engage with the inside of the body such that a fluid (air) seal is formed between the end of the plunger and the inside of the body, and a volume of fluid is expelled from the body through an orifice in one end of the body as the plunger is inserted further into the body and a volume of fluid is taken in to the body as the plunger is drawn out of the body. The device further includes a high pressure valve sized, shaped, and configured to release an excess volume of fluid from the body after the fluid pressure within the body reaches a predetermined high fluid pressure. The predetermined high fluid pressure is sufficient to inflate an endotracheal tube cuff to a point where a pneumatic seal is formed between the endotracheal tube cuff and a patient's trachea to prevent air leakage and aspiration during patient ventilation. The device further includes a low pressure valve sized, shaped, and configured to release an excess volume of fluid from the body to reduce the fluid pressure within the body from the predetermined high fluid pressure to a predetermined low fluid pressure. The predetermined low fluid pressure is high enough to minimize increased risk of Ventilator Associated Pneumonia and low enough to minimize increased risk of stenosis, ischemia and rupture of the trachea. The low pressure valve is sealed, initially, until after the fluid pressure within the body reaches the predetermined high fluid pressure. After the predetermined high fluid pressure is reached, the seal on the low pressure valve is broken such that the fluid pressure within the body is reduced from the predetermined high fluid pressure to the predetermined low fluid pressure.

"A single full stroke of the plunger in the body begins at an initial point where the plunger has been drawn out from the body to the fullest extent possible without breaking the fluid seal that is formed between the end of the plunger and the inside of the body. In some embodiments, a stop is included within the body to prevent removal of the plunger from the inside of the body and ensure the fluid seal that is formed between the end of the plunger and the inside of the body is not broken. The single full stroke ends at a concluding point where the plunger has been inserted within the body to the fullest extent possible without breaking the fluid seal that is formed between the end of the plunger and the inside of the body.

"In some embodiments, the low pressure valve is sized, shaped, and configured to release any fluid pressure buildup in the body (over the course of a single full stroke) generally in excess of about 20 cm H2O to 30 cm H2O. In some embodiments, the high fluid pressure is in the range of generally 60 to 90 cm H2O. In some embodiments, the body includes a fluid volume capacity generally greater than the fluid volume capacity of an endotracheal tube cuff. In some embodiments, the low pressure valve is sealed by a membrane. In some embodiments, the membrane is punctured by the plunger, exposing the low pressure valve and reducing the fluid pressure within the body from the predetermined high fluid pressure to the predetermined low fluid pressure. In some embodiments, fluid flow through the orifice is sealed off after the fluid pressure within the body reaches the predetermined low fluid pressure. In some embodiments, fluid flow through the orifice is sealed off after a period of time (e.g., 3 seconds) after the single full stroke has concluded.

"According to a third aspect, a method of using an endotracheal tube cuff inflation device is provided. The method of use includes drawing out the syringe plunger from the syringe body, connecting the orifice to an endotracheal tube cuff, and inserting the syringe plunger into the syringe body in a single full stroke to create a fluid pressure within said body. The inserting step includes the steps of: releasing an excess volume of fluid from said body once said fluid pressure within said body reaches a predetermined high pressure limit and to temporarily maintain said predetermined high pressure limit within said body; and releasing fluid pressure from said body after said high pressure limit has been maintained to reduce said fluid pressure within said body from said predetermined high pressure limit to a predetermined low pressure limit. In some embodiments, the method further includes sealing off the endotracheal tube cuff inflation device after the fluid pressure within the syringe body is reduced from the predetermined high fluid pressure to the predetermined low fluid pressure.

"One embodiment of the instant invention comprises a disposable syringe that, over the course of a single, full stroke of the syringe plunger, will increase cuff pressure, from a generally deflated pressure (approximately 0 cm H2O, or some other suitable pressure below 25 cm H2O) to over 60 cm H2O (or another suitable predetermined high pressure limit, including but not limited to other limits discussed in other embodiments herein) and then decrease the pressure to a final pressure of 25 cm H2O (or another suitable predetermined low pressure limit, including but not limited to other limits discussed in other embodiments herein). The initial pressure overshoot of 60 cm H2O is achieved with a high pressure relief valve, optionally located at the tip end of the syringe, which releases air when the syringe chamber pressure reaches (or exceeds) 60 cm H2O. The syringe chamber volume is larger than the volume of the ETT cuff the syringe is being used to inflate such that the 60 cm H2O pressure relief valve will be activated before the syringe plunger is fully contracted. In some embodiments, at the end of the syringe plunger stroke, and preferably after the ETT cuff has been inflated to 60 cm H2O in the manner described above, the plunger punctures a membrane, thereby exposing a second pressure relief valve that releases air until the pressure drops to 25 cm H2O.

"In another embodiment of the general inventive concept, the syringe used to inject fluid (air) into an Endotracheal Tube cuff (ETTc) to the proper pressure of 25 cm H2O (or other predetermined limit) is comprised of a plunger that slides up and down a chamber in a reciprocating piston arrangement to force air out of the chamber through a male luer nozzle that connects to a standard female luer of the ETTc portal. The syringe has two unique sub-systems that work together to set the cuff pressure to 25 cm H2O, namely the 'Low Valve Activation' and 'Reseal' sub-systems.

"In the Low Valve Activation sub-system, the syringe uses a unique arrangement of passive fluid pressure valves to reach the proper pressure of 25 cm H20 by (stage 1) exceeding the final pressure during the plunger stroke and (stage 2) dropping to the final pressure with a passive valve that is activated at the end of the syringe stroke, allowing air to flow out of system.

"In the Low Valve Activation, Stage 1, during the stroke of the syringe, air is injected into the ETTc until the cuff is fully inflated. The volume of the syringe chamber is larger than the volume of the cuff to ensure the cuff will be fully inflated to pressures exceeding final pressure (preferably 60-90 cm H2O, or other desired predetermined limit) before the plunger travels the distance of a single, complete stroke. To avoid unsafe over-pressurization of the ETTc, air is allowed to escape out of a high pressure passive valve, in this embodiment calibrated to open at pressures around 90 cm H2O (or other predetermined high pressure limit). In one preferred embodiment, the high pressure valve is seated in the plunger. Alternative embodiments have the high pressure valve seated within the syringe chamber. Regardless of where the high pressure valve is physically located, it is arranged such that fluid pressure within the syringe chamber (cavity formed between the body and the plunger) that exceeds the high pressure valve limit is released.

"In the Low Valve Activation, Stage 2, at the end of the plunger stroke, the plunger activates a low pressure valve that was previously sealed off from the airflow through the system. Once activated, air escapes out of the over-pressurized ETT cuff through the low pressure valve. In this embodiment, the Low Valve is calibrated such that fluid pressure immediately decreases until it reaches 25 cm H2O. Consequently, in a preferred embodiment, during Stage 2, the pressure of the system follows an exponential curve that falls sharply the instant the Low Valve is activated. In a preferred embodiment, after a predetermined period of time (e.g. approximately 3 seconds in one embodiment) after the Low Valve is activated, system pressure levels out around 25 cm H2O. In this preferred embodiment, the Low Valve is isolated from the system by a spring-loaded piston member (referred to as the Low Valve Actuator hereon) that seals off the volume around the low valve with an o-ring. When the plunger nears the end of its stroke, it pushes down the Low Valve Actuator, the O-ring seal is broken and air can flow through the Low Valve out of the syringe chamber.

"In the reseal, since the airflow out of the Low Valve will continue (through eventual bleeding of the valve) until the system pressure drops to near zero, the syringe includes a method of shutting off the airflow when the pressure has fallen to 25 cm H2O. Since the pressure drops to 25 cm H2O approximately 3 seconds after the Low Valve is activated, the Reseal mechanism has an approximate 3 second delay before the system completely reseals. In the preferred embodiment, the Reseal mechanism is comprised of a spring-loaded piston (separate from the Low Valve Actuator and referred to as the Flow Actuator hereon) with an O-ring that shuts off flow through the male luer nozzle. The Flow Actuator slides inside the Plunger. As the Plunger is pushed down during the syringe stroke, friction from the Plunger pushes the Flow Actuator down against the spring thereby breaking the o-ring seal and allowing air to flow out the nozzle. At the end of a syringe stroke, the spring pushes the Flow Actuator back up to until the Flow Actuator O-ring is in its sealed position. The spring is calibrated so that the returning force placed upon the Flow Actuator is slightly greater that the friction of the Plunger on the Flow Actuator. Consequently, the Flow Actuator slowly travels upward toward the reseal position (3 second total travel time). I will be appreciated that alternative delay periods may be utilized without departing from the spirit and scope of the instant invention.

"In some preferred embodiments, in which the syringe of the present general inventive concept is intended to be used with, and is used with, a standard ETT cuff used on adults, the syringe volume prior to breaking the seal of the second (low) pressure relief valve (i.e. by breaking a membrane covering the seal, activating a piston to open the seal or otherwise exposing the low pressure valve) is approximately 13 ml. This volume is designed to be larger than the volume of the standard ETT cuff, and allows the syringe of this embodiment to work with a large variety of ETT cuffs, including ETT cuffs that are used in the animal life sciences. There is a linear relationship between measured cuff pressure (cm H2O) and the volume of air in the cuff (ml), defined as: Pressure=7.5*Volume+2.7. Based upon this equation, the minimum syringe volume necessary to inflate the standard ETT cuff to 60 cm H2O is approximately 7.64 ml. Thus, the syringe volume of approximately 13 ml of the preferred embodiment discussed herein helps to ensure proper inflation of a standard ETT cuff to 60 cm H2O, by taking into account outliers from the study discussed in Appendix B and producing a volume of air that is significantly greater than the volume typically necessary to inflate the ETT cuff to 60 cm H2O, and thereby utilizing the 60 cm H2O pressure release valve to prevent the cuff pressure from exceeding 60 cm H2O.

"The embodiments of the present general inventive concept discussed above provide healthcare professionals with means to automatically establish a safe ETT cuff pressure with a single stroke of a syringe. The present general inventive concept automatically establishes a safe pressure, thereby eliminating risk and procedural time associated with conventional methods of ETT cuff inflation. In addition, the device of the embodiment discussed herein is disposable and lightweight, both of which are qualities valued in hospital setting. The automatic syringe of the embodiment discussed herein may eliminate, or help to reduce, hospitals' durable medical equipment costs, procedural time and procedural risk. Hospitals continue to cut costs by incorporating disposable devices into patient care; disposables may be billed to the patient, reduce inventory costs and do not require periodic calibration (as do ETT cuff pressure measurement devices such as the Cufflator). Meanwhile, hospitals are faced with the constant challenge of reducing risk to the patient, which often requires increased durable medical equipment spending and procedure duration. Nevertheless, the instant invention provides a novel device that has the advantage of reducing both patient risk and hospital cost. Some embodiments of the general inventive concept are intended to be single use only and afterward disposed of. Other embodiments of the general inventive concept are intended to be disposable after a patient no longer needs it, but may be used and re-used repeatedly on a single patient (for example, the syringe may be re-used if the proper seal was not achieved on the first try or if the ETT Cuff needs to be re-inflated).

"The foregoing and other objects are intended to be illustrative of the general inventive concept and are not meant in a limiting sense. Many possible embodiments of the invention may be made and will be readily evident upon a study of this specification and accompanying drawings comprising a part thereof. Various features and subcombinations of general inventive concept may be employed without reference to other features and sub combinations. Other objects and advantages of the general inventive concept will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of this invention."

For more information, see this patent: Stanhope, Rawley; Close, Brandon W.. Endotracheal Tube Cuff Inflation Device and Methods. U.S. Patent Number 8721589, filed November 30, 2010, and published online on May 13, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=107&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=5341&f=G&l=50&co1=AND&d=PTXT&s1=20140513.PD.&OS=ISD/20140513&RS=ISD/20140513

Keywords for this news article include: Hospital, Spiritus Technologies LLC.

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Source: Journal of Technology