Patent Application
20050229928
This invention relates to apparatus and methods for delivering aerosol particles, e.g. an aerosolized medicament, to the respiratory system of a subject through an invasive or noninvasive pressure-assisted breathing system. More specifically, one aspect of the invention is directed to apparatus and methods for delivering an aerosolized medicament from a nebulizer to a patient by a pressure-assisted breathing system.
The use of pressure-assisted breathing systems is well-known for the treatment of respiratory disorders and diseases in adults, e.g. infection, obstructive sleep apnea and respiratory insufficiency, and in children, e.g. abnormal breathing resulting from small or collapsible airways, small lung volumes, muscle weakness, respiratory distress syndrome, persistent obstruction following surgery, etc. As used herein, the term “pressure-assisted breathing system” means any artificial ventilation system that applies pressures, usually positive, to gas(es) in or about a patient's airway during inhalation as a means of augmenting movement of gases into the lungs. The term is intended to include mechanical ventilators and continuous positive airway pressure (“CPAP”) systems, which also includes bi-level positive airway pressure systems. The term is also intended to include both non-invasive and invasive systems. Systems that utilize an endotracheal or tracheostomy tube are examples of invasive pressure-assisted breathing systems. Systems that utilize nasal prongs or a mask are examples of non-invasive pressure-assisted breathing systems.
Pressure-assisted breathing systems utilize positive pressure during inhalation to increase and maintain lung volumes and to decrease the work of breathing by a patient. The positive pressure effectively dilates the airway and prevents its collapse. The delivery of positive airway pressure is accomplished through the use of a positive air flow source, e.g. a mechanical ventilator, that provides oxygen or a gas containing oxygen through a flexible tube connected to a patient interface device. The term “patient interface device” includes nasal prongs (cannula), nasopharyngeal tubes or prongs, an endotracheal tube, tracheostomy tube, mask, etc.
The tubes associated with commercially available pressure-assisted breathing systems create a “circuit” for gas flow by maintaining fluid communication between the elements of the circuit. Tubes can be made of a variety of materials, including but not limited to various plastics, metals and composites and can be rigid or flexible. Tubes can be attached to various elements of the circuit in a detachable mode or a fixed mode using a variety of connectors, adapters, junction devices, etc. These elements are sometimes collectively referred to herein as “junction devices”.
As an example of one such junction device, a mechanical ventilator system may utilize a ventilator circuit comprising an inspiratory tube that conducts a flow of gas from a ventilator and an expiratory tube that conducts a flow of gas back to the ventilator. This circuit (sometimes referred to herein as a “ventilator circuit”) is in fluid communication with a third tube (the “respiratory circuit”) that conducts a flow of gas to the patient interface device through a junction device, usually a tubular member in the shape of a “Y” or “T”. Such a junction device may comprise a first leg attachable to the inspiratory tube of the ventilator circuit, a second leg attachable to the expiratory tube of the ventilator circuit and a third leg attachable to the respiratory circuit. Other junction devices may be used, for example, to connect a nebulizer or a patient interface device to the appropriate circuit of the ventilator system.
Aerosol generators or nebulizers have been used to deliver an aerosol of medication through a ventilator system into the respiratory system of a patient. For example, U.S. Pat. No. 6,615,824, issued Sep. 9, 2003, and in co-pending U.S. patent application Ser. No. 10/465,023, filed Jun. 18, 2003, and Ser. No. 10/284,068, filed Oct. 30, 2002 describe apparatus and methods for connecting a nebulizer to a ventilator circuit to emit a aerosolized medicament directly into the flow of gas being delivered to a patient's respiratory system. As a result, the gas flows in circuits of ventilator systems are called upon to carry suspended aerosol particles from the aerosol generator to the patient.
It is imperative that a therapeutically effective amount of aerosolized medicament reach the desired sites in the patient's lungs to achieve a successful treatment, yet it is also desirable that the medicament be delivered in as efficient a manner as possible to minimize losses and waste. Although effective amounts of medicament delivered to a patient's airways in aerosol form, e.g. by the using a nebulizer connected to a ventilator system, are considerably less than the amounts needed to deliver a therapeutically effective amount of medicament systemically, current systems still exhibit inefficiencies. For example, aerosol particles being carried in the circuits of ventilator systems and other pressure-assisted breathing systems may be trapped on the inner walls of the tubes, deposited at irregular surfaces and obstructions in the tubes or other elements in the circuits, impact the interconnection between tubes of different diameters, or be diverted by sharply angled paths in the circuits. As one specific example, aerosol particles have to “turn corners” when traveling at relatively high flow rates through the sharply angled conduits presented by the “Y”, “T”, and “V”-shaped junction devices currently used in conventional pressure-assisted breathing system circuits. As a result, the aerosol particles may impact the walls of the junction device, and a portion of the particles may be diverted from the primary aerosol flow into various ports or branches in the circuits. As another example, aerosol particles may be deposited at the junction of a patient interface device and the respiratory tube connecting it to the ventilator circuit, or may be diverted or deposited within the patient interface device itself.
Accordingly, it is desirable to find ways to decrease the losses of aerosol particles within pressure-assisted breathing systems. In particular, increasing the efficiency in the delivery of aerosolized medicaments through ventilator systems, and the resulting smaller amounts of medicament required for a treatment, can represent a substantial advantage, particularly when scarce and expensive medicaments are employed.
It has been found in accordance with the present invention that the efficiency of delivery of aerosolized medicaments can be significantly increased by eliminating the sharp angles or corners encountered by the flow of aerosol particles in the circuits of pressure-assisted breathing systems. Specifically, the present invention provides apparatus and methods that increase the efficiency of the delivery of aerosolized medicament to the patient by providing a straight or gently angled path for the flow of aerosol particles from the point at which the aerosol generator introduces aerosol particles into the gas flow to the point at which the aerosol particles enter the patient's respiratory system.
In a preferred embodiment, the present invention provides a pressure-assisted breathing system comprising a flow generator, a circuit connecting the flow generator to a patient's respiratory system and an aerosol generator for emitting aerosol particles of medicament into the circuit, wherein the circuit defines a path for said aerosol particles having a change in angle no greater than 15°, preferably no greater than 12°, and most preferably no change in angle at all.
In one embodiment, the present invention provides a junction device for connecting the various flexible tubes comprising the circuits of a pressure-assisted breathing system. For example, one junction device of the present invention may replace the conventional “Y”, “T” or “V”-shaped junction piece that connects the inspiratory tube and expiratory tube of a ventilator circuit to the respiratory circuit. Still another embodiment provides improved nasal prongs (cannula) for delivering aerosolized medicament to a patient.
One preferred embodiment of the present invention provides a junction device comprising (i) a tubular main body member having a straight longitudinal lumen extending its entire length for conducting a first flow of gas carrying aerosol particles; and (ii) a tubular branch member in fluid communication with the longitudinal lumen for conducting a second flow of gas substantially free of said aerosol particles into or out of the longitudinal lumen.
In one embodiment, the junction device further comprises: (iii) a port for attaching an aerosol generator to the main body member so as to introduce the aerosol particles into the first flow of gas. In one preferred embodiment, the aerosol generator is a vibrating aperture-type nebulizer that is preferably positioned in the port so that the vibrating plate of the nebulizer is flush with the internal surface (“wall”) of the longitudinal lumen so that the emitted aerosol particles will not drag against the internal surfaces of the lumen.
In one embodiment, the present invention provides a ventilator system comprising a ventilator circuit having an inspiratory tube and an expiratory tube converging at a junction device attached to a respiratory circuit. The junction device comprises (a) a tubular main body member having a straight longitudinal lumen extending from a first end attached to said inspiratory tube to a second end attached to said respiratory circuit, and (b) a tubular branch member having a lumen extending from said longitudinal lumen to a third end attached to said expiratory tube. In another embodiment, the junction device further comprises a port for attaching a nebulizer to the main body member so as to introduce aerosol particles into the longitudinal lumen.
In another embodiment, the present invention provides a ventilator system comprising a ventilator circuit and a patient interface device attached to the ventilator circuit, wherein a nebulizer is positioned between the patient interface device and the ventilator circuit. In still another embodiment, a second nebulizer is positioned in the ventilator circuit on a junction device of the present invention.
In one embodiment, the present invention provides a patient interface device comprising a tubular inlet section having a longitudinal lumen, a pair of nasal cannula, and a tubular forked section connecting the inlet section to the nasal cannula. The longitudinal lumen in the inlet section is in fluid communication with lumens in each prong of the forked section so as to define two substantially parallel paths for the aerosol particles, each path having a change angle from the path defined by the longitudinal lumen no greater than 15°, more preferably no greater than 12°
In one embodiment, the present invention provides a method of delivering aerosolized medicament to a subject's respiratory system comprising the steps of attaching the subject to pressure-assisted breathing system comprising a gas flow generator, a circuit connecting the gas flow generator to the subject's respiratory system and an aerosol generator for emitting aerosol particles of medicament into the circuit, the circuit defining a path for said aerosol particles having a change angle no greater than 15°; preferably no greater than 12°, and most preferably no change in angle at all, and then administering the aerosol particles of medicament to the subject via the pressure-assisted breathing system.
Most of the following detailed description is directed to a ventilator embodiment of the invention for illustrative purposes only, it being understood that the invention is not limited to such embodiment and can be applied to other pressure-assisted breathing systems.
Circuit V includes a ventilator 2 in fluid communication with inspiratory tube 3 and expiratory tube 4 converging at “Y”-shaped junction device 5. Respiratory circuit R includes a patient interface device 6 in fluid communication with circuit V at junction device 5. Nebulizer 7 is in fluid communication with circuit V at intersection 8 upstream to junction device 5. In operation, a pressurized flow of gas 9 is introduced into inspiratory tube 3 from ventilator 2 and passes to and through intersection 8. Nebulizer 7 emits an aerosolized medicament 10 into gas flow 9 at intersection 8 to produce combined gas flow 11 containing aerosolized medicament 10. Gas flow 11 is transported through junction device 5 to patient interface device 6 and ultimately to the respiratory system of the patient upon inspiratory effort by the patient through patient interface device 6. Expiratory effort by the patient through patient interface device 6 produces expiratory flow 12 which flows from patient interface device 6 through junction device 5 to expiratory tube 4 and back to ventilator 2.
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Another embodiment of the present invention is shown in
The gas flow generator employed in the present invention may conveniently comprise any of the known sources of pressurized gas suitable for use in a pressure-assisted breathing system. Typically, the gas flow generator is capable of supplying a flow of gas, which includes at least some portion of oxygen, at slightly greater than atmospheric pressure. For example, the source of pressurized gas may be an air blower or a ventilator, or the pressurized gas may originate from a wall supply of air and/or oxygen, such as that found within hospitals and medical facilities, or may originate from a pressurized cylinder of cylinders. The pressurized gas may comprise various known mixtures of oxygen with air, nitrogen, or other gases and may be provided in a single stream or flow.
The respiratory circuit of the present invention may comprise a patient interface and optionally, such customary tubes and connectors as are required to provide fluid communication between the ventilator circuit and the patient interface device. The patient interface device may include any of the known devices for providing gas communication to the patient's respiratory system. By way of example, the patient interface device may include nasal prongs, an oral/nasal mask, a nasal mask, nasopharyngeal prongs, an endotracheal tube, a tracheostomy tube, a nasopharyngeal tube, and the like.
The nebulizer used in the present invention may be any of the aerosol generators suitable for creating aerosols as liquid droplets or dry particles (referred to herein as “aerosol particles”), for example, atomizers, atomizing catheters, vibrating aperture-type nebulizers, ultrasonic nebulizers, jet nebulizers, etc. Preferred nebulizers may comprise a reservoir for holding a liquid medicament to be delivered to a patient's respiratory system and an aerosol generator for aerosolizing the liquid medicament. The nebulizer is positioned so as to direct aerosol particles into a circuit of the pressure-assisted breathing system. For example, the nebulizer may be connected to a circuit of a ventilator system through a separate connector, a connector integrated with the nebulizer body or a connector integrated with a junction device. Particularly preferred “vibrating aperture-type” nebulizers comprise a vibrational element and dome-shaped aperture plate with tapered holes. When the plate vibrates at a rate of about 100 thousand times per second, a micro-pumping action causes liquid to be drawn through the tapered holes, creating a low-velocity aerosol with a precisely defined range of droplet sizes. Such nebulizers are commercially available from Aerogen Inc., Mountain View, Calif., and are described in detail in the art, for example, in U.S. Pat. No. 6,615,824, issued Sep. 9, 2003, and in copending U.S. patent application Ser. No. 10/465,023, filed Jun. 18, 2003, and Ser. No. 10/284,068, filed Oct. 30, 2002. The entire disclosures of said patent and applications are incorporated by reference herein.
Due to the increased efficiency of the present invention, the reservoir of the nebulizer may be sized to accommodate a smaller amount of medicament. For example, the reservoir of the nebulizer may have a capacity equal to a single unit dose of medicament, i.e. an amount sufficient for one treatment, and substantially all of the medicament may be delivered to the patient without the need to replenish the reservoir. This is particularly beneficial in respiratory therapies that utilize phospholipid surfactants since these medicaments are scarce, expensive and, because of their high viscosity, are difficult to deliver. The present invention may also eliminate the need to pump medicament from an outside container to the nebulizer, although in some applications of the invention this may be desirable.
The nebulizer may be connected to a controller for controlling operation of, and to supply power to, the aerosol generator. Preferably, the controller and other electronic components are connected with wires, cables and connectors that are small and flexible. In one embodiment, the controller may be integrated in the same enclosure with a CPAP system controller. In this case, the two systems may use the same power supply and communicate electronically. Examples of other components that may also be associated with nebulizers are a timer, status indication means, liquid medicament supply nebule or syringe, etc., all as know by those skilled in the art and described in detail in the aforementioned patent and patent applications.
When used in a ventilator system, the nebulizer may be conveniently positioned in the ventilator circuit or in the respiratory circuit. As one example, the nebulizer may be attached to the inspiratory tube of the ventilator circuit using a separate connector or using a connector integrated with the body of the nebulizer. Such connectors are adapted to provide a conduit for aerosol particles to travel from the aerosol generator of the nebulizer to the gas flow in the ventilator circuit so that the aerosol particles are entrained in the gas flow. As another example, the nebulizer may be attached to a port in a junction device of the present invention, as previously described above in connection with
For example,
In other embodiments, it may be advantageous to have a nebulizer positioned in the respiratory circuit. For example, placement of the nebulizer in close proximity to the patient's nose, mouth or artificial airway, e.g. directly adjacent to the point of intake of an endotracheal (ETT) tube or in close proximity to a nasal cannula or mask, may further improve the efficiency and control of the delivery of the aerosolized medicament to the patient. Since significant deposition of aerosol particles may occur at the connection of patient interface device when the aerosol particles impact the edges of the connector as they try to enter the device, placing the nebulizer as close as possible to the patient interface device makes the “dead space” between the aerosol generator and the patient interface device as small as possible. This reduction or elimination of dead space may significantly reduce the loss of aerosol particles entering the patient interface device.
Referring now to
Connector base 73 may further comprise main body member 74 having inlet 75 adapted to interconnect with connector 65 on one end and outlet 76 adapted to interconnect with endotracheal tube 67 on the opposite end. Longitudinal lumen 77 extends from inlet 75 through main body member 74 to outlet 76 to form a straight path for the flow of gas from connector 65 to endotracheal tube 67. The vibrating plate of aerosol generator 72 is positioned in port 78 of connector base 73, preferably flush with the internal wall of lumen 77, so as to emit aerosol particles of medicament produced by aerosol generator 72 directly into the gas flow within lumen 77 with a minimum amount of turbulence.
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One embodiment of the present invention provides a method of delivering aerosolized medicament to a subject, preferably a human patient that exhibits one or more symptoms of infection or other respiratory disease or disorder. The method generally comprises attaching the subject to a pressure-assisted breathing system comprising a gas flow generator, a circuit connecting the gas flow generator to the subject's respiratory system and an aerosol generator for emitting aerosol particles of medicament into the circuit, wherein the circuit defines a path for the emitted aerosol particles having a change in angle of no greater than 15°. The larger changes of path angle, e.g. about 12°-15°, are most suited to pressure-assisted breathing systems employing nasal cannula, particularly when used with surfactant medications. In other applications, smaller changes of path angle may be preferred, i.e. a change in path angle of no greater than 12° and most preferably no change in path angle (a straight path).
Medicaments useful in the practice of the invention may be any of those commonly used in aerosol form for treating the above-described symptoms, for example, various antibiotics or combinations of antibiotics (preferably used in ventilator systems) and surfactant medicaments (preferably used in CPAP systems). Examples of antibiotics include anti-gram-positive agents such as macrolides, e.g. erythromycin, clarithromycin, azithromycin, and glycopeptides, e.g. vancomycin and teicoplanin, as well as any other anti-gram-positive agent capable of being dissolved or suspended and employed as a suitable aerosol, e.g. oxazoldinone, quinupristin/dalfopristen, etc. Antibiotics useful as anti-gram-negative agents may include aminoglycosides, e.g. gentamicin, tobramycin, amikacin, streptomycin, netilmicin, quinolones, e.g. ciprofloxacin, ofloxacin, levofloxacin, tetracyclines, e.g. oxytetracycline, dioxycycline, minocycline, and cotrimoxazole, as well as any other anti-gram-negative agents capable of being dissolved or suspended and employed as a suitable aerosol.
Surfactant medications (sometimes referred to herein as “surfactants”) are protein-lipid compositions, e.g. phospholipids, that are produced naturally in the lungs and are essential to the lungs' ability to absorb oxygen. They facilitate respiration by continually modifying surface tension of the fluid normally present within the air sacs, or alveoli, that tube the inside of the lungs. In the absence of sufficient surfactant, these air sacs tend to collapse, and, as a result, the lungs do not absorb sufficient oxygen. Insufficient surfactant in the lungs results in a variety of respiratory illnesses in both animals and humans. Since most of these surfactant medications are animal-based, the current supply is limited, and although synthetic surfactants are available, their manufacture is both inexact and expensive. In addition, the surfactant medications are typically high in viscosity and are difficult to deliver to the patient's respiratory system. The increased efficiency of the pressure-assisted breathing system of the present invention, and the smaller amount of medicament required for a treatment according to the present invention, can be a substantial advantage when such scarce and expensive medicaments are employed.
In a preferred embodiment, the nebulizer of the present invention has a reservoir capacity equal to a unit dose of medicament. As an example, one dose of a liquid phospholipid surfactant medicament is typically achieved by instilling about 100 mg of the surfactant into an infant's lung. However, the required aerosol dose appears to be considerably less. For example, animal researchers have determined that an inhaled dose of about 4.5 mg/kg of surfactant is sufficient to substantially improve oxygenation in animal models. This suggests that a sufficient unit dose of surfactant to deliver to the lungs of a 1 kg. infant in aerosolized form may be about 5-10 mg. Since liquid surfactant is typically dispensed in a dilute solution having a concentration of 25 mg/ml, about 2/5 ml (10/25 ml) of liquid surfactant may be required to obtain 10 mg of active surfactant. A neonate CPAP system may be designed according the present invention to deliver about 6-18% of the total aerosolized medicament to an infant's lungs with a normal breathing pattern. If, for example, the nebulizer efficiency is 10%, the amount of surfactant solution required in the nebulizer reservoir to deliver a unit dose of aerosolized surfactant would have to be increased by a factor of 10, i.e. 10×2/5 ml or 4 ml. Therefore, a nebulizer reservoir having a capacity of 4 ml may be sufficient to provide a unit dose of surfactant to a 1 kg infant in accordance with the present invention without the need to replenish the reservoir.
The unit dose and the corresponding nebulizer reservoir size may vary depending on the efficiency of the nebulizer, the weight of the patient and the amount of surfactant needed. For example, if the infant in the above example weighs 3 kg, a unit dose (and corresponding reservoir size) would be about 12 ml of liquid surfactant (i.e. 3 kg×4 ml/kg). Similarly, if 5 mg of active surfactant is needed in the above example, a unit dose would be about 2 ml of liquid surfactant (i.e. 5/25 ml×10), and if the efficiency of the nebulizer in the above example is 15%, a unit dose would be about 2 2/3 ml (i.e. 2/5 ml×100/15).
A nebulizer according to the present invention may administer a unit dose by aerosol in less than 20 minutes, and possibly in as little as 5 minutes. Aerosol generation can be continuous or phasic, and can be timed to titrated dose delivery rate over time; for example, a 4 ml maximum dose with nebulization for 1 second out of every 10, 20 or 30 seconds.
The pressure-assisted breathing systems of the present invention may include any of the other elements conventionally found in such systems such as, for example, humidifiers, filters, gauges, traps for sputum and other secretions and controllers that control the breathing cycle, the nebulizer and/or other components. An humidifier in the system is particularly advantageous since control of the humidity may affect the efficiency of aerosol particle delivery. For examples, the aerosol particles should be prevented from undergoing significant hygroscopic enlargement since particles enrobed in water will tend to condense of the walls of system tubes. Breathing cycle controllers may also be particularly useful in the practice of the invention since they may be used to actuate the administration of aerosol only during the inspiration phase of the breathing cycle or when the humidifier is not active, thereby further enhancing the efficiency of the system.
It is understood that while the invention has been described above in connection with preferred specific embodiments, the description and drawings are intended to illustrate and not limit the scope of the invention, which is defined by the appended claims and their equivalents.
This application is a continuation-in-part of U.S. application Ser. No. 10/828,765, filed Apr. 20, 2004, which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10828765 | Apr 2004 | US |
| Child | 10883115 | Jun 2004 | US |
