Patent Application
20150000652
This disclosure relates generally to a gas delivery unit and a breathing mask for delivering respiratory gas of a subject.
Tidal volume (TV) is an amount of an air inspired or taken into the lungs in a single breath. TV is also dependent on the sex, size, height, age and a health etc. of a patient. In general TV also decreases as the size of the patient decreases. In an average healthy adult, TV is about 400-600 ml whereas in an average healthy neonate, that measures 3.5-4 kg and is 50 cm tall. TV is approximately 25-50 ml. On the other hand, in an average premature neonate that measures only 500 grams TV is only about 2-3.5 ml. TV of a smaller patient's is very difficult to measure, but it can be approximated to 4-7 ml/kg, applying a general rule of thumb for approximating the TV of the human lung. In practice the TV of the patient suffering pulmonary system deficiency is normally less than the approximation gives.
Patients can be mechanically ventilated invasively or non-invasively. In invasive ventilation an endotracheal tube is placed into a trachea so that it goes through oral or nasal cavity and larynx. In tracheostomy endotracheal tube goes straight into trachea through neck. The other end of the endotracheal tube is connected to a breathing circuit Y-piece through a luer type connector.
Continuous Positive Airway Pressure (CPAP) is a one type of non-invasive positive pressure ventilation used to maintain an elevated baseline respiratory system pressure during spontaneous breathing. Neonates or infants are preferential nose breathers until 5 months of age, which easily facilitates the application of nasal CPAP for a variety of clinical conditions including respiratory distress syndrome, apnea of prematurity and in other conditions that require positive pressure. This is accomplished by inserting nasopharyngeal tubes, affixing nasal prongs, or fitting a nasal mask to the patient.
Common for all, ventilation Methods is that during an inspiration the flesh breathing gas including higher oxygen (O2) concentration should flow into the patient's lungs through a breathing circuit, nasopharyngeal tubes, affixing nasal prongs, or a nasal mask, then to oral or nasal cavities, a trachea, a bronchus, a bronchi, bronchioles and finally reaching an alveoli deep in the lungs, where all the gas exchange actually occurs. Carbon dioxide (CO2) molecules in hemoglobin of a blood flowing in tiny blood vessels around the alveoli are replaced with O2 molecules in the fresh breathing gas through the thin walls of the alveoli. O2 molecules take their place in the hemoglobin, Whereas CO2 molecules flow out from the patient within the used expired breathing gas, through the same path as the fresh gas came in during the inspiration. This path common for inspiratory and expiratory gases inside the patient's respiratory system causes rebreathing of gases and is called anatomical dead volume.
The anatomical dead volume is almost impossible to reduce, but it is proportional to the size and the physical condition of the patient. The mechanical dead volume outside the patient depends on a breathing circuit design, an inner diameter of a tubing, connectors and additional accessories, such as sidestream and mainstream gas analyzers connected to patient's respiratory system. Obviously the mechanical dead volume is more critical for smaller patients with smaller TV or patients suffering barotraumas etc., which also decrease TV.
A nebulizer is a device used to administer medicine in the form of a mist of small droplets into the lungs of through the lungs into the blood stream. Nebulizers are commonly used for the treatment of cystic fibrosis, asthma, COPD and other respiratory diseases. Nebulizers use oxygen, compressed air or ultrasonic power to break up medical solutions and suspensions into small droplets that can he delivered from the device into the patient's lungs. With mechanically ventilated patients nebulizers are commonly connected between the inspiratory tubing to increase the delivery efficiency of medication into the lungs, since conventional nebulizers generate mist of droplets continuously, also during the expiratory phase, which is lost into the breathing circuit.
The mist form medicine is formed of small fluid drops having a diameter conventionally between 0.1-100 μm depending on the nebulizing technology used. The fluid drops are commonly sprayed out from the nebulizer with a speed, which is specific to used nebulizing technology. The smallest drops have lower inertia proportional to the lower mass and the speed of droplets, which slows down faster due air resistance. The largest drops have higher inertia, proportional to the higher mass and the higher speed of droplets, which also maintain their velocity longer although the air resistance slows down the speed finally.
It is commonly recommended that the best delivery efficiency may be achieved with droplets having a diameter of 1-5 μm, which most probably penetrate the inspiratory air flow and then float down and reach the alveoli in the deep lung. The optimum sized droplet, between 1-5 μm are difficult to generate, but can be achieved with for example nebulizers based on vibrating mesh plate technology.
When the smaller drops are sprayed towards the inspiratory gas flow through the nebulizer limb 232 in
When the largest drops are sprayed towards the inspiratory gas flow they penetrate the gas flow easily and may start to float within the inspiratory gas flow towards the patient. However as the larger drops have higher inertia they also tend to continue to travel into their original direction, thus hitting the walls of a breathing circuit, especially in places where the cross sectional area of the flow path changes rapidly in the connections between conventional breathing circuit parts, such as conventional catheter mounts, L-, T-, Y-pieces, conventional flow, pressure, gas analyzing devices etc. or in the places of very high constrictions, such as where the breathing circuit connects with the endotracheal tube through an endotracheal tube connector. These connections also generate turbulences into the gas flow that redirects the drops floating within the gas flow causing them to hit the breathing circuit wall, but also to collide and combine with each other forming larger drops with higher inertia and incorrect flow directions causing them to hit the walls of the breathing circuit.
The outer diameter Of endotracheal tube is Selected to fit into the patient's trachea to prevent gases to leak through the connection. The inner diameters of endotracheal tubes vary between 2-10 mm in 0.5 mm steps depending on the size of a patient. Every size endotracheal tube connects to the similar sized endotracheal tube port of the endotracheal tube connector. The endotracheal tithe connector further connects to the rest of the breathing circuit through the standard sized breathing circuit port of the endotracheal tube connector. The standard breathing circuit ports of endotracheal tube connectors have outer diameters of 8 mm, 15 mm and 22 mm, but the connector with 15 mm outer diameter is the most commonly used. This means that the cross sectional area between the endotracheal tube end and the breathing circuit end of the endotracheal tube connector changes rapidly and the difference in cross sectional area increases when the patient s size decreases. When the breathing circuit with an inner diameter of 15 mm is connected to for example endotracheal tube with the inner diameter of 2 mm through the endotracheal tube connector it generates a huge cross sectional change into the flow path. This increases the gas flow speed and thus the inertia of the drops floating within the gas considerably, but also the direction of the gas flow near the walls of the connector. The rapid, conical change also generates strong flow turbulences scattering the direction of drops, which in turn causes the drops to collide and combine with each other and to hit walls of an endotracheal tube connector.
In the conventional system shown in
It is not reasonable to place the nebulizer 230 between the expiratory limb 207 or the expiratory tube 211, since the mist of drops generated would be lost into the expiration gas flowing away from the patient.
The nebulizer 230 may be place between the endotracheal tube connector 202 and the common limb 204, which increases the delivery efficiency of even a continuously functioning nebulizer compared to the placement into the expiratory side since the part of the mist of drops produced during inspiration will flow towards the patient's lungs, but this place would increase the volume common for inspiratory and expiratory air flow increasing the rebreathing of gases, which is fatal for the gas exchange in the lungs especially with smaller size patients whose tidal volumes are small.
If the nebulizer 230 is placed between the inspiratory limb 206 or the inspiratory rube 210 the efficiency of delivery increases compared to the placement into the expiratory side since the part of the mist of drops produced during inspiration will flow towards the patient's lungs even the nebulizer produces the drops continuously. However the number of connections, constrictions and turbulences between the nebulizer and the patient lungs increases decreasing the number of drops reaching the lungs. Also the distance between the nebulizer and the patient's lungs becomes longer causing the drops to collide and combine with each other forming larger droplets, which hit the walls of the breathing circuit more probably.
Thus at the moment there does not exist an efficient way of delivering medicine into the patient's lungs as a mist of droplets. For this reason the expensive drugs are lost into the breathing circuit and devices connected to it newer reaching the patient's lungs, Which makes the patient care very problematic as there is no understanding how much drug ends up into the patient lungs and how appropriate and effective the planned care was.
The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification.
In an embodiment, a gas delivery unit for delivering a respiratory gas of a subject includes an expiratory limb for delivering an expiratory gas, and an inspiratory limb for delivering, an inspiratory gas. The gas delivery unit also includes a common limb connecting at a branching point with the expiratory limb and the inspiratory limb for delivering both the expiratory gas and the inspiratory gas, and at least one port for a fluid dispenser. The port is configured to open into at least one of the inspiratory limb, the expiratory limb, the common limb and the branching point, the port having a longitudinal axis along an opening direction, and which longitudinal axis of the port is configured to form an angle δ, which is less than 90° degrees, with a longitudinal axis of one of the inspiratory limb, the expiratory limb and the common limb, and which longitudinal axis of the inspiratory limb is configured to form an angle β, which is at an angle of 100°-180° degrees, with the longitudinal axis of the common limb.
In another embodiment, a breathing mask for delivering a respiratory gas of a subject includes an expiratory limb for delivering an expiratory gas, and an inspiratory limb for delivering an inspiratory gas. The breathing mask also includes a common limb connecting at a branching point with the expiratory limb and the inspiratory limb for delivering both the expiratory gas and the inspiratory gas, and at least one port for a fluid dispenser. The port is configured to open into at least one of the inspiratory limb, the expiratory limb, the common limb and the branching point, the port having a longitudinal axis along an opening, direction, and which longitudinal axis of the port is configured to form an angle δ, which is less than 90° degrees, with a longitudinal axis of one of the inspiratory limb, the expiratory limb and the common limb, and which longitudinal axis of the inspiratory limb is configured to form an angle β, which is at an angle of 100°-180° degrees, with the longitudinal axis of the common limb.
In yet another embodiment, a breathing mask for delivering a respiratory gas of a subject includes an expiratory limb for delivering an expiratory gas, and an inspiratory limb for delivering an inspiratory gas. The breathing mask also includes a common limb connecting at a branching point with the expiratory limb and the inspiratory limb for delivering both the expiratory gas and the inspiratory gas, and at least one of only one respiratory tube and at least two respiratory tubes, the common limb being in operational contact with one of the only one respiratory tube and the at least two respiratory tubes for delivering inspiratory gas from the common limb into at least one cavity of the subject and expiratory gas from the at least one cavity of the subject to the common limb. The breathing mask also includes at least one port for a fluid dispenser, which port is configured to open into at least one of the inspiratory limb, the expiratory limb, the common limb and the branching point. A longitudinal axis of the port is along an opening direction, and which longitudinal axis of the port is configured to form an angle δ, which is less than 90° degrees, with a longitudinal axis of one of the inspiratory limb, the expiratory limb and the common limb, and which longitudinal axis of the inspiratory limb is configured to forum an angle β, which is at an angle of 100-180° degrees, with the longitudinal axis of the common limb. A diameter of the common limb is configured to deviate less than 10% from one of a diameter of the only one respiratory tube and combined diameters of the at least two respiratory tubes.
Various other features, objects, and advantages of the invention will be made apparent to those skilled in art from the accompanying drawings and detailed description thereof.
Specific embodiments are explained in the following detailed description making a reference to accompanying drawings. These detailed embodiments can naturally be modified and should not limit the scope of the invention as set forth in the claims.
The at least one port 81 enable connecting or disconnecting the fluid dispenser 90 or any other respiratory care device advantageously without losing the pressure in the breathing circuit 1 as shown in
It is advantageous to place the fluid dispenser as close to the patient's airways as possible to minimize the distance between the fluid dispenser and the lungs, but also to minimize the numerous mechanical connections between different breathing circuit parts, turns, intersections etc. to enable as straightforward and smooth flow path as possible for the drops to travel from the fluid dispenser 90 into the patient's lungs, preventing the drops to collide with each other and hit the walls of a breathing circuit. In the schematic view of the gas delivery unit 3 of the breathing circuit 1 shown in
The standard endotracheal tube connector, between the standard size breathing circuits and the standard endotracheal tubes, gather a lot of drops into its walls decreasing the delivery efficiency of the mist form medicine. The volume of the whole breathing circuit common for inspiratory and expiratory gases is also vast causing rebreathing of gases, which is especially problematic with smaller sized patients. Thus it is advantageous in many ways to have patient size specific breathing circuit gas delivery units 3 with an inner diameter similar to patient size specific endotracheal tubes or nasal tubes 100, which they connect to with a minimal change in a cross sectional area firming a continuous and uniform flow path between the at least one port with or without the additional limb SO and the at least one respiratory tube 100, but also ensuring a minimal volume common for the inspiratory and expiratory gases minimizing the rebreathing of gases.
The best results are achieved when the fluid dispenser is placed outside the common limb 20 to minimize the volume causing rebreathing of gases, but also outside the inspiratory limb 6, as close to the patient as possible, to minimize the distance to the patient's lungs and the number of connections, turns and intersections to minimize the number of collisions between the drops and number of collisions into the walls of the breathing circuit tubing. Thus the branching point 21 between the inspiratory limb 6 and the common limb 20 enables the most efficient delivery of drops into the patient's lungs with a minimal breathing circuit volume causing rebreathing of gases.
The fluid dispenser 90 may be connected through the port 81, located in the inspiratory limb 6 or in the common limb 20 (not shown in figures) to allow nebulized fluid drops to penetrate and flow within the inspiratory gas flow. However if the fluid dispenser is placed in the inspiratory limb 6 the distance and the number of connections between the fluid dispenser and the patient increases. The longer the distance the more probably the fluid drops collide and combine with each other forming larger droplets with higher inertia after they hit the walls of the breathing circuit as in the turn. If the fluid dispenser is placed in the common limb 20 the volume of a common path, where the inspiratory and expiratory gases flow, is increased causing rebreathing of gases. If the nebulizer is placed in the expiratory limb 7 it is more difficult for the mist of drops to enter the inspiratory flow and most of the mist will be lost during expiration. However, it is possible to place the port $1 with or without the additional limb 80 into the expiratory limb 7, but then advantageously the port with or without the additional limb $0 may locate close to the branching point 21, typically within a distance which is less than the diameter of the expiratory limb 7.
The inspiratory gas flow in the breathing circuit needs to be laminar for the fluid drops to travel straightforward on average towards the patient lungs within the inspiratory gas flow. Laminar inspiratory gas flow also enables easier penetration of drops into the gas flow and enables them to retain the longitudinal flow direction in the common limb 20 and endotracheal tube or nasal tubes 100 enabling them to float within the inspiratory gas flow into the patient's lungs without colliding with each other and into the walls of the breathing circuit. Every cross sectional change, turn or intersection generates turbulences along the inspiratory gas flow path. The inspiratory air 60 flowing through the inspiratory limb 6 into the common limb 20, past the expiratory limb 7 generates turbulences 64 into the output of expiratory limb 7 near the branching point 21. These flow turbulences disturb the penetration and the direction of droplets sprayed by the fluid dispenser through the port 81 with or without the additional limb 80 into the inspiratory gas flowing by. The turbulences 64 generated into the output of expiratory limb 7 near the branching point 21 can be minimized by adjusting the angle a between the longitudinal axis 61 of the inspiratory limb 6 and the longitudinal axis 63 of the expiratory limb 7 and the angle β between the longitudinal axis 61 of the inspiratory limb 6 and the longitudinal axis 62 of the common limb 20. Thus it is advantageous that the angle β is between 100°-180° degrees and the angle a is between 0°-170° degrees. The better results are achieved, with the angle β between 110°-160° degrees and the angle α is between 30°-120° degrees and the best results are achieved with the angle β between 125°-145° degrees and the angle a is between 45°-100° degrees. When the angles α and β are 0° degrees they represent a special case of coaxial tubing when the inspiratory tubing, is located inside the expiratory tubing.
When considering usability aspects it is advantageous that the inspiratory limb 6 and expiratory limb 7 open out parallel towards the ventilator 9 and that they are bent into an angle τ in regard to common limb 20 to avoid twisting forces from the inspiratory and expiratory tubes directed to the endotracheal tube to prevent it to disconnect from the patients trachea as shown in
The inertia of droplets needs to be appropriate to enable the droplets to penetrate into the inspiratory gas flow 60 and to prevent droplets bouncing from the boundary surface of inspiratory gas flow. Fluid dispensers based on vibrating mesh plate can produce droplets between 1-5 μm with a fairly constant droplets speed. Also the average speed of inspiratory gas flow between different sizes of patients can be equalized with the patient size specific breathing circuit gas delivery units 3, shown in
The length L1 of the common limb 20 shown in
Thus the optimum place for the fluid dispenser 90 to administer medicine into the patient's lungs in the form of mist or droplets is to connect it into the at least one port 81 with or without the additional limb 80, which is placed close to or into the branching point 21 of the gas delivery unit 3 firstly to minimize the distance between the fluid dispenser 90 and the patient, secondly to minimize the number of turns, intersections, constrictions and mechanical connections between the different breathing circuit parts, thirdly the location of the port 81 with or without the additional limb 80 and the direction of the port with or without the additional limb are adjusted in regard to longitudinal axes of one of the inspiratory limb 6, expiratory limb 7 and common limb 20 to enable the penetration of droplets into inspiratory gas flow and not into the walls of the breathing circuit and fourthly the location and the direction of the longitudinal axes of at least one of the additional limb 80 and the at least one port 81 is adjusted in regard to longitudinal axes of inspiratory limb 6 and expiratory limb 7 to increase the usability of the gas delivery unit 3, but also to minimize the flow turbulences make the inspiratory air flow laminar and suitable for the droplets to float into the correct direction and inertia along the longitudinal axes of the common limb 20 into the patient's lungs.
The offset in distance in the intersection between the longitudinal axes 65 along at least one of the opening of the port 81 and along the longitudinal axis of the additional limb 80 and the common limb 20 can be used to generate controlled flow swirl that may ease the penetration of droplets into the inspiratory gas flow and increase the delivery efficiency.
A breathing mask 102 is shown in
The written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention.
The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
