Patent Application
20170258369
The invention is a device for a feedback controlled pressure output system designed to deliver a highly controlled and accurate air stimulus into the larynx coupled with mucosal sensory monitoring for diagnostic use.
Proper larynx function is critical in our daily lives. Part of its job is to instinctively close the glottic airway and initiate a cough in response to a foreign body, such as food or liquid, entering the trachea. Should this instinctive response fail to elicit properly, aspiration of the foreign body into the lungs can occur, with a significant risk of subsequent infection called aspiration pneumonia. Aspiration pneumonia has a mortality rate as high as 70%, and accounts for 10 to 30 percent of all deaths associated with anesthesia. Risk of aspiration is increased in patients with a wide variety of pathologies from gastric acid reflux to neurological diseases and stroke. Specifically, patients undergoing surgical operations under general anesthesia and intubation have been shown to have a deceased ability to achieve full laryngeal reflex post-operatively for an unknown amount of time.
While the laryngeal reflex eventually returns to normal, in an effort to avoid aspiration complications, surgery departments across the world have placed protocols dictating when a patient is allowed to resume eating and drinking after surgery. However, this time period has so far been arbitrarily set by each department, with little insight as to when the laryngeal reflex actually returns.
Thus the inventors came up with the idea to research the return of the laryngeal reflex post-operatively, by creating a novel air stimulus device for experimental and diagnostic purposes.
This invention is an extremely precise air stimulus that uses a control system to output medical grade air into the larynx, while simultaneously monitoring mucosal sensory activity for diagnostic use. The presentation of air stimuli has been widely used in the past in order to better understand the actions of the larynx which include swallowing, speech, and protection. However, no prior air stimulus device exists on the market currently. There previously existed a popular commercial device, the Pentax AP-4000, but that has been out of production (and service) for a number of several years. It is now recognized as inaccurate and unsuitable for research. As such, it fell out of favor due to its limited clinical value. Now, the door is open for the device of this invention to go well beyond filling its place. Our device is designed to be significantly more accurate, safer for the patient, highly modular for easy future modifications and provide diagnostic information not previously available.
This invention delivers a novel tool that is very precise, safe and modular permitting easy future improvements. The first requirement is that it must be a feedback controlled device. Feedback control provides output stability, faster ramp times (the time it takes to reach 2% error from the desired output) and more robustness (the ability to be compatible with all types of patients.) The ability to simultaneously monitor pharyngeal sensory function shall provide clinics with unmatched diagnostic accuracy. The second requirement is safety. This is accomplished by building a closed and carefully monitored system, using a medical air source as our pressure source and components that could be easily sterilized. In this manner, no contamination would be introduced into the patient. In addition, there are both hard coded delimiters and mechanical relief valves that prevent unsafe pressures from being administered. This combination of sterility and safety mechanisms shall both actively prevents users from unintentionally harming their patients and reduces any risks of infection. Lastly, the third requirement is that the device be modular, such that additional inputs and outputs could be programmed in the future. The selected microcontroller is a float point grid array capable of many task. This provides the ability to write code that is very flexible, such that we not only have our primary control function, but can easily take advantage of new signals. An example of how we have taken advantage of this is by monitoring the pharyngeal mucosa sensory function. In addition, we have created a digital Guided User Interface, rather than providing the user with an analogue set of haptic inputs (i.e. dials and buttons). By creating a software human-machine-interface, we can continuously upgrade the backend software to add more functionality, and respond to customer feedback to make the device more user-friendly. We believe this will not only provide greater functionality, but also lead to a more satisfactory customer experience.
In one embodiment, an ultrasonic sensor is integrated into the laryngeal mechanoreceptors.
Other objects and advantages of the present invention will become apparent to those skilled in the art upon a review of the following detailed description of the preferred embodiments and the accompanying drawings.
The device schematics shown in
Typical laryngeal mechanoreceptor physiology is well known.
Initially, medical grade air, either from a tank or wall source, is fed into the device. Prior to reaching the primary components, the air passes through an excess pressure relief valve. This way the incoming air pressure can be limited physically to protect the patient in case of a malfunction upstream of the device.
Within the enclosure, the air reaches a precisely controlled system in which a two valve feedback controlled system provides delicate control for desired output pressures. The solenoid valves are driven by signals from the driver module and microprocessor, which receive command signals by way of user input through the software interface. The user can program both the pressure magnitude and the duration of each test on a very easy to use Guided User Interface. Thus the user directly controls how much air is allowed to pass through the fine control valves, and finally reach the patient (via laryngoscopy).
To ensure greater safety, a couple of measures were taken. A transistor-transistor logic (TTL) input enables the valve to be closed regardless of the analog input, which allows for greater safety and control of the device as the valve can be safely completely closed when not in use. A pressure sensor located downstream of the solenoid valve provides feedback of the air output back to the software. The Feedback Control System (FCS) creates a circuit loop which communicates back to the microprocessor the results in a steady and accurate pressure output over the duration of the stimulus presentation. Lastly all components shall be sterile.
The device improves targeting of peripheral nerves such as the internal branch of the superior laryngeal nerve using surface electrodes. Two major short comings of surface electrodes use are electrode placement and interference from the surrounding muscular tissue. Needle electrodes are an alternative, but are limited by a patient acceptance especially with neck placement. It is very difficult to get a clear neural signal with topical electrodes due to the poor signal to noise ratio. Traditional amplification and filtering of the signal will not suffice, as amplification would maintain the signal to noise ratio, and filtering could distort the action potential signal. Optimizing electrode placement will improve the signal to noise ratio without the introduction of distortion.
This issue also generalizes to EMG nerve conduction studies, which often require the usage of invasive insertion electrodes to diagnose nervous system functional status. Given even insertion electrodes require close placement to the nerve for signal acquisition, this sometimes results in multiple insertions for each patient. This can be a painful procedure, such that patients have been known to refuse treatment on this basis alone. Therefore, there is a clear need for a system that can precisely locate the position of commonly used peripheral nerves for electro-diagnostic purposes.
This solution couples an ultrasonic sensor with the EMG electrode manifold. For example, the superior thyroid artery and vein accompany the internal branch of the superior laryngeal nerve as it exits the larynx through a hole in the thyrohyoid membrane, such that physicians have used this artery in the past to locate the nerve. Given the density difference of the surrounding tissues: blood vessels, cartilage, and the surrounding fascia, ultrasonic sensor can be used to resolve the position of superior thyroid artery and vein and thereby the internal branch of the superior laryngeal nerve. Thus, by resolving the co-located blood vessel we are able to more precisely locate the internal branch of the superior laryngeal nerve enhancing the signal to noise ratio—in a very cost effective manner.
Because the nerve runs horizontally in the same plane before turning vertically, the electrode manifold incorporates an array of electrodes to capitalize on this anatomic regularity. The reliability of the directionality of the commonly used peripheral nerves makes electrode array-placement feasible. Once the nerve located, it is very reasonable to incorporate others to not only improve signal to noise robustness but to permit assessment of nerve transmission velocity.
Note this technology generalizes very well to other peripheral nerves, such as the median, sural, and peroneal nerves. Many peripheral nerves used in EMG studies have an artery or vein in close proximity; as such, the same ultrasonic sensing technology could be used to locate the location of the nerve. Therefore, it is believed that this system could also be offered as a standalone nerve targeting system, to be used for peripheral nerve sensory and stimulatory electrodes.
This device integrates an ultrasonic sensor as an analogous input, and then couples the sensor and electrode together into a single manifold.
The electrode array will permit qualitative assessment of nerve conduction velocity through the delays identified as the action potential passes and is detected in each subsequent equidistant placed sensors in the array. To give an indication of location, we would use a harmonic generator. We would take the absolute value of the difference in measured density versus expected blood density, and have the system “beep” at a duty cycle that reflects proximity. It could also be possible to give a visual indicator on the LMS's Guided User Interface, but we would most like leave that within the ‘Advanced’ tab for simplicity.
It is additionally proposed that actuation mechanism be offered for physician who are interested in using insertion electrodes. While the typical insertion electrode is painful due to the geometry, there do exist painless needles, such as those used in acupuncture. Given that all that is necessary for nervous signal acquisition is a quality conducting surface, a similarly thin needle could be integrated directly into the manifold, with corresponding actuator. This actuator would then deliver the painless insertion electrode precisely into the patient at a location of the nerve. In this case of one time use electrodes, the actuator could be a simple spring loaded mechanism. In the use case of repeated use electrodes, the actuator could be a DC motor, where feedback control could be used to determine proper electrode insertion depth. Note that the electrode would have a fine point, followed with greatly widening base, to create a physical barrier to unsafe insertion depths.
The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from scope of the invention. Accordingly, the whole of the foregoing description is to be construed in an illustrative and not a limitative sense, the scope of the invention being defined solely by the appended claims.
This application claims the benefit of U.S. provisional patent application Ser. No. 62/081,802 filed on Nov. 19, 2014.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/061282 | 11/19/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62081802 | Nov 2014 | US |
