Patent Application
20130269693
This invention is related to the field of breathing gas delivery machines, such as continuous positive airway pressure (CPAP) or bi-level positive airway pressure (Bi-PAP) machines of the type typically used to treat patients suffering from breathing disorders, such as hypopnea or apnea, and, in particular, is related to the humidification apparatus and methods for such devices.
Continuous Positive Airways Pressure (CPAP) machines are well known in the art for use in the treatment of a number of respiratory conditions, such as sleep apnea and hypopnea, by supplying a continuous positive pressure to a patient's airway while the patient sleeps.
It is well known in the art that such machines be equipped with a humidification apparatus to humidify the air being delivered to the patient. This tends to increase the comfort of the patient and eliminates the “dry mouth” condition experienced by many users of the machines.
A typical humidification apparatus consists of a simple humidification chamber containing a reservoir into which water is introduced by the user. The water is heated by an electro-resistive heating element and the air flow being delivered to the patient passes through the humidification chamber containing the heated water, thereby warming and humidifying the air. The device may be equipped with multiple settings settable by the user to vary the level of humidification by varying the temperature to which the water is heated.
There are several problems existing with the current humidification devices for the CPAP machines. First users may experience a condition known as “rain-out” in which heated humidified air exits the humidification chamber and condenses as it cools in the lower temperature hose before reaching the patient. The condensed water tends to accumulate in the hose and may even block certain portions of the hose, forcing the user to breath are through the accumulated water, creating a “gurgling” sound and interfering with pressure delivery to the patient. This problem is sometime solved in the prior art by providing a heated wire along the length of the tube to prevent the air from cooling as it flows through the tube. However, this solution is undesirable in that it tends to increase the overall power consumption of the machine and cost of the air supply tube which is usually disposable and replaced at set intervals.
In addition to the rain-out problem, the heating of the water also increases the overall power consumption of the machine. Therefore it would be desirable to provide an improved humidification apparatus that address both the rain-out problem without increasing power consumption.
The present invention includes a method operating a CPAP machine to improve the humidification of the air being breathed by the user, as well as the accompanying improved humidification apparatus.
As is well known to one skilled in the art, the breathing cycle of a patient is composed of an inhalation phase and a exhalation phase. In prior art devices, the patient airflow is permitted to pass through the humidification chamber during the entire breathing cycle, both during the inhalation phase and the exhalation phase. In the preferred embodiment of the present application, the patient air flow is allowed to pass through the humidification chamber only during the inhalation phase of the breathing cycle. During the exhalation phase of the breathing cycle, the air flow is diverted to an alternate path that does not pass through the humidification chamber.
This modified method of handling the airflow addresses both problems noted above. With respect to the rain-out problem, the cooler, dryer air passing through the hose during the exhalation phase of the breathing cycle will tend to dry out any condensing humidity in the hose and secondly, the passage of less air through the humidification chamber will cause the electro-resistive heater to use less energy to keep the water in the reservoir heated to the desired temperature, thereby not only reducing the likelihood of rainout but actually reducing power consumption at the same time.
In addition, the method provides the added benefit of requiring the user to fill up the water reservoir in the humidification chamber less often. In empirical studies the method of the present invention can reduce both the water consumption and the power consumption of the device by over 50%.
a and 6b show a perspective and end view respectively of the valve shuttle portion of the valve in
In a preferred embodiment of the invention, the microprocessor 100 also controls solenoid-enable valve 108 which can be in one of two states. In the first state, valve 108 allows airflow to pass from blower 106 through humidifier 110. In the second state, valve 108 diverts the airflow away from humidifier 110 and sends it directly to the patient.
Many CPAP-type machines contain algorithms to detect the beginning and end of the inhalation and exhalation phases of the breathing cycle of the user. In particular, in Bi-PAP devices this detection is necessary because different pressures are applied during the inhalation and exhalation phases. The actual method of detecting the transition between the inhalation and exhalation phases is not part of this invention. However, the presence of such an algorithm and its implementation in the device is necessary to take advantage of the method and apparatus of the present invention.
In one embodiment of the invention, valve 108 may switch from one state to the other when the phase transition is detected. However, in a preferred embodiment, it is desirable to open or close the valve in anticipation of the phase transition such that humidified air reaches the patient at the approximate start of the inhalation phase and non-humidified air reaches the patient at the approximate start of the exhalation phase. Switching the state of valve 108 at the transition detection instead of in anticipation of the transition will cause a short overlap at the beginning of each phase, during which, for example, humidified air is being delivered to the patient when non-humidified air is desired, or visa versa.
Thus, the opening and closing of valve 108, which allows the airflow to either pass through humidification chamber 110 or be diverted therefrom, need to occur in anticipation of the transitions instead of when the transition between the phases is actually detected. Various factors, such as the length of the tube between the machine and the user and the amount of leakage being experienced by the user will effect the time it takes for humidified air to travel from humidification chamber 110 to the patient. Therefore, the actual time period in anticipation of the transition will be dependent upon these and other factors.
A preferred embodiment of the valve is shown in
Coupler 5, positioned at the inlet port 10 of valve body 1 serves as an interface to a hose or other conduit carrying the air from the air pump within the machine. Rare earth magnets 4 positioned on the interior of valve shuttle 2 causes valve shuttle 2 to move longitudinally within valve body 1 and responds to a magnetic field provided by a solenoid (not shown). As valve shuttle 2 moves longitudinally through valve body 1 it is also caused to rotate approximately 45 degrees by the movement of spindles 3 through slots 6.
a and 6b show a perspective and end view of valve shuttle 2 respectively. In
As previously stated, there are many designs of electromechanical valves which may be used in this application and as such the invention is not meant to be limited by this particular valve. In addition, the method and apparatus of the invention is not limited to use in CPAP or Bi-PAP machines, but has applications in any machine delivering air to a patient, such as a ventilator or for use during surgery to deliver anesthesia.
