FIELD

Embodiments described herein concern devices and methods that assist gas exchange and stabilize lung volume in patients of all ages with breathing problems.

BACKGROUND

Patients who have breathing difficulties are conventionally provided breathing assistance using mechanical ventilators. These devices are generally expensive and out of reach of a large portion of the population, particularly in economically disadvantaged countries. These devices also require substantial training and expertise to operate and maintain. Further, these devices do not provide the user the ability to set and vary upper limit of safe positive pressure that is patient specific and commensurate with the peak inspiratory pressure levels set during ventilation in an easy and less expensive way using a fluid column.

In recent years, there has been increasing interest in the development of breathing assistance devices that are less expensive. U.S. Pat. No. 8,499,759 discloses the use of a two-way valve in a pressure regulating breathing assistance apparatus wherein the valve is placed intermediate two pressure control conduits that are submerged at varying lengths in a single container containing a fluid. In such apparatus, depending on the size of the valve, back pressure is generated whereby the pressure of gas at a patient interface may be higher than the pressure set using one of the control conduits, but not the other. This back pressure, if not correctly accounted for, has important treatment and safety implications if the device is used on a patient. Further, when two pressure control conduits are located in the same container, the interaction between the two conduits in operation may impact pressures at a patient interface.

There is a significant need to provide a respiratory assistance apparatus that is easy and less expensive to make, operate and maintain, and has high-positive-pressure safety feature that is simple, reliable and easily adjustable relative to the desired patient-specific inspiratory pressure level.

SUMMARY OF THE INVENTION

It is generally known in the medical profession that stabilization of lung volumes and improvement in gas exchange in patients receiving ventilation assistance could be achieved through appropriate settings and control of the positive pressures generated, amplitude and frequency of oscillating positive pressure in the ventilator. Embodiments described herein provide the user a device and method to set pressures, oscillations, amplitude and frequency, and further allows the user to set the upper limit of positive pressure that is specific for a patient to reduce the likelihood of damage to the lungs. Additionally, the embodiments described herein maintain a patient's mean airway pressure at controlled levels. Device parameters such as levels of fluid in the containers, lengths of the ducts immersed in the fluids in the containers can be varied to control the high as well as low pressures. These embodiments also have features that allow a user to select and modulate breaths per minute, inspiratory time, and the ratio of inspiratory to expiratory time. The embodiments described herein are useful to adults, children and newborn babies. Further, the embodiments can be used during transport of patients, and may be used in facilities that do not have access to mechanical ventilators. Several embodiments described herein can also be converted to a bubble Continuous Positive Airway Pressure (CPAP) system.

In one embodiment, a ventilator system is provided having a pressurized gas supply, two containers filled with fluid, and a primary duct with two ends—the proximal end and the distal end. The proximal end is connected to the pressurized gas supply. The primary duct is adapted for connection to a patient interface between the proximal and distal ends. At the distal end, a peak inspiratory pressure control duct is connected and immersed in a body of fluid in the first container. A positive end-expiratory pressure control duct is also connected to the distal end of the duct and immersed in the body of fluid in the second container. A two-port valve, also known as a two-way valve, is connected in between the inspiratory pressure control duct and the positive end-expiratory pressure control duct wherein the rate of opening and closing of the valve can be controlled. In addition, at least one safety duct is connected to the primary duct near the proximal end and is immersed in the fluid column in the first container at depth greater than the immersed length of the peak inspiratory pressure control duct. Immersed length is the vertical distance measured from the top of the fluid surface to the tip of a pressure control duct. The depth to which the at least one safety duct is immersed is controlled by the user. In some embodiments, ducts have simple markings, for example in cm of water, to help the user set high pressure (peak inspiratory pressure), low pressure (positive end-expiratory pressure), and high-pressure limit (Pop-Off). In other embodiments, the immersed length is adjusted by varying water column heights or by varying positions of ducts or both to deliver high and low pressures. In certain embodiments, as a safety feature, the default position of the ventilator system is to deliver the lower pressure at all times as CPAP when the ventilator system is connected to the patient.

The use of double containers allows the user to isolate and fix any issues with one container or duct without disconnecting the patient from the breathing support. Also, the use of double containers prevents the bubbles generated in one container from impacting the liquid column level and pressure in the duct placed in the other container. In some embodiments, two-way or three-way valve allows the user to set breathing rates from 4-60 per minute, known as conventional mechanical breaths, and frequencies in the range of 60-900 per minute, known as high frequency range. In other embodiments, a controller allows the user to control inspiratory to expiratory ratios or have it fixed as percent of cycle time to maintain a desired inspiration time to expiration time ratio, when the cycle frequencies are adjusted. Valves used in the embodiments include without limitation solenoid valves, pneumatic valves and solar powered valves.

In another embodiment, a ventilator system is provided having a pressurized gas supply, two containers filled with fluid, and a primary duct with two ends—the proximal end and the distal end. The proximal end is connected to the pressurized gas supply. The primary duct is adapted for connection to a patient interface between the proximal and distal ends. Also provided is a three-port valve (also known as a three-way valve) having one inlet port and two outlet ports. The distal end of the primary duct is connected to the inlet port of the valve. The first outlet port of the valve is connected to a peak inspiratory pressure control duct that is immersed in a body of fluid in the first container. The second outlet port of the valve is connected to a positive end-expiratory pressure control duct that is immersed in a body of fluid in the second container. In operation, the valve alternatively connects the inlet port to the first outlet port and the second outlet port, i.e., the gas entering the inlet port passes through the first outlet port for a period of time and then the gas entering the inlet port passes through the second outlet port for another period of time, completing a cycle of passage of gas through the first outlet port and the second outlet port. The cycle then repeats. A controller communicably connected to the valve controls the number of cycles per unit time, for example, number of cycles per minute. In addition, at least one safety duct is connected to the primary duct near the proximal end and is immersed in the body of fluid in the first container at depth greater than the immersed length of the peak inspiratory pressure control duct.

In yet another embodiment, a second valve is also provided wherein the second valve is an open-shut type shutoff valve which can isolate the positive end-expiratory pressure control duct from the remainder of the ventilator gas flow circuit.

In some embodiments, the two containers are of the same size and the tips of the peak inspiratory pressure control and the positive end-expiratory pressure control ducts are positioned at same location within each of the two containers. The location is determined by vertical distance of the tip of a control duct from the bottom inner surface of a container. In this embodiment, the peak inspiratory pressure and the positive end-expiratory pressure are set by a user by changing the fluid levels in the two containers.

In another embodiment, the level of fluid in the first container is greater than the level of fluid in the second container such that the immersed length of the peak inspiratory pressure control duct is greater than the immersed length of the positive end-expiratory pressure control duct.

In certain embodiments, the fluid used is water. In other embodiments, the peak inspiratory pressure control duct and the end-expiratory pressure control duct are substantially circular having an inside diameter of between about 0.5 to 2 cm and their immersed lengths inside the containers are in the range of about 2-50 cm.

