Patent Description:
High flow nasal therapy (HFNT) will typically deliver an air/oxygen/aerosol mix to a patient at a rate that exceeds their peak inspiratory rate. An example is 50LPM treatment vs. an average inhalation of about <NUM> LPM (averaged across the inhalation period of a breath) with a peak inhalation of about 35LPM. Aerosol delivered into the high flow stream will be homogeneously distributed. Therefore, the excess airflow contains aerosolised drug that the patient cannot absorb and this results in reduced efficiency. Also, this excess will disperse into the surrounding room air. This is a fugitive emission that potentially exposes clinicians, patients and visitors to aerosolised drugs and patient-generated pathogens.

Also, during exhalation (typically through the mouth), the high flow therapy may continue to deliver to the nasal cavity. A portion of this flow will travel into the cavity and exit the patient's mouth, and this flow augments the exhalation flowrate and has the potential to collect patient pathogens. The remainder of the flow will exit the cavity via the nostrils, but prior to this it also can collect pathogens.

<CIT> and <CIT> describe HFNT systems, in which aerosol is delivered primarily during reduced gas flow periods, in order to increase efficiency and reduce losses. <CIT>) describes a mask for patient ventilation. <CIT>) describes a tube seal adapter for face masks. <CIT> describes a sealing pad for a respiratory mask. <CIT>) describes a mask which is fitted over a nasal prong interface. <CIT> Describes a nasal cannula. <CIT>) describes an exhalation scavenging mask. <CIT>) describes a multi-function oxygen mask. <CIT>) describes systems and methods for administration of drugs and medications). <CIT> describes methods and systems of delivering medication via inhalation.

The invention addresses the problem of achieving effective aerosol treatment with reduction or elimination of gas losses, particularly for high flow treatment.

The invention provides a system as set out in claim <NUM>, and optional features as set out in claims <NUM>-<NUM>.

Referring to <FIG> a patient interface <NUM> comprises an annular soft seal base <NUM> configured to fit around a patient's mouth and nose with a large contact surface of resilient material which is suited to skin contact. The base <NUM> has a relatively rigid core surrounded on at least the patient side with soft material for patient facial contact. The base spine supports a prong receiver <NUM> extending across the base <NUM>, and being of a plastics material having a rugged strength to support attachment of a nasal prong head <NUM> with prongs <NUM> at the end of tubing <NUM> for delivery of high flow gas and aerosol to the nostrils.

<FIG> shows that the interface also includes a shell <NUM> which fits with a seal to the base <NUM> and the support <NUM> to form an enclosed volume around the patient's mouth and nasal area. <FIG> shows an extraction head <NUM> which has an L-shaped conduit <NUM> with a flange <NUM> configured to fit to a cylindrical port <NUM> of the shell.

<FIG> shows the full interface <NUM>, with all of these components in place, together with a lead <NUM> from a pressure sensor within the volume formed by the base <NUM> and the shell <NUM>. The pressure sensor is attached to the inside surface of the shell <NUM>.

The patient interface is modular, the soft seal base <NUM> attaching to the patient's head with securing head straps <NUM>. The support <NUM> supports the prong head <NUM> with the prongs <NUM> correctly aligned. It is envisaged that in other embodiments the prong support is self-supporting by way of head straps rather than being attached to the soft seal base, especially for uses without extraction.

The soft seal base <NUM> is placed on the face first and a comfortable sealing surface is established. This establishes a gas-tight seal and provides a support mechanism for the high flow therapy tubing, and the clinician can conveniently and accurately set up the patient's nasal prongs <NUM> secured to the soft seal base <NUM>. The fit of the prongs <NUM> can be checked and adjusted.

The shell <NUM> can now be assembled. The perimeter of the shell <NUM> interfaces with the base such that it self-locates and forms a seal, the soft seal base <NUM> providing a means of securing the shell <NUM> in place by for example elastic straps, hook-and-loop fasteners, or clips. It is preferred that the shell fit by way of a snap-fit connection with resilient edges. The shell <NUM>, nasal prongs <NUM>/<NUM>, and the soft seal base <NUM> are profiled such that the high flow therapy tubing and head <NUM> can enter from either the left or the right, and a seal is still established without the need for an additional part. In another embodiment an additional capping feature can be provided.

The shell <NUM> preferably includes one or more vents to prevent an excessive negative pressure drop within the volume formed by the base <NUM> and the shell <NUM> due to extraction. These are located away from exhalation / exhaust airstreams of the mouth and the nostrils. The shell <NUM> has a port <NUM> to attach a means of suction, in this case the extraction head <NUM>. The position of the extraction port <NUM> is such that in use it is opposed to the mouth and nostrils for optimal collection of exhaled / exhausted gasses and particles. The vent or vents may not be in the mask itself, and could for example be part of an exhalation tube. The benefit of a vent is that, because the mask is very effective at sealing the space around the nose and mouth, the operation of the high flow system and the forced extraction system does not cause the system to be too intrusive by acting effectively akin to a ventilator, in which all inhalation and exhalation is controlled. There may for example be a very soft opening on an inhale valve to not affect breathing, and/or a pressure release valve for safely in case of reduced extraction. The vent may have a suitable filter to block outflow of unwanted droplets to avoid contamination of the environment.

The shell also has a retainer to attach a sensor for measuring the internal mask pressure.

<FIG> shows test results for ambient aerosol particles in the environment surrounding the patient's head for with the mask and system shown in <FIG>. This mask is conventional in terms of how it is configured to engage the face, simply a flexible clear polymer with holes cut to take the HFNT delivery and extraction hoses. It does not have the benefits of the mask of <FIG>.

<FIG> demonstrates an extraction flowrate in the region of 80LPM to 100LPM is required to capture approximately all aerosol particles, in these examples with treatment at 50LPM. <FIG> demonstrates the major differences between the bands of <NUM>- to <NUM> LPM, <NUM> LPM, and no extraction. In the latter there is essentially no difference between situations where the mask is present and is not, because of losses around the edges of the mask. <FIG> shows more detail for the higher extraction rate band, with the vertical axes showing particles in the tens per cm<NUM>. <FIG> is a summary histogram showing that there is a liner relationship between extraction flowrate and percentage of particles captured. , reaching full capture at about 90LPM extraction.

The positioning of the extraction port opposite the patient's mouth affects the rate of emission capture for a given extraction rate. In <FIG>, the `Lower Fit' outperforms the `Nominal Fit' in terms of capture of emissions (<NUM>% vs. <NUM>%). The degree of sealing between the mask and the face affects rate of emission capture for a given extraction rate. In <FIG> `Closed Fit' is the same as `Lower Fit' except that there is sealing at the cheeks. At the same level of extraction (<NUM> LPM) versus the same emission flowrate (50LPM, there is no breath in this example) the `Closed Fit' outperforms the `Lower Fit' in term of capture of emissions (<NUM>% vs. <NUM>%).

The effect of extraction on the nasal cavity has been investigated. A test setup as shown in <FIG> but with addition of a nasal pressure sensor involved:.

The results of this are illustrated in <FIG>, which displays the distribution of the nasal pressure peaks, which occur during exhalation, with and without extraction. The average difference is a reduction of <NUM>. 3mBar when extraction is applied; the difference of the maximums is <NUM>.

<FIG> displays the distribution of the nasal pressure troughs (these occur during inhalation) with and without extraction. The average difference is a reduction of <NUM>. 68mBar when extraction is applied; the difference of the minimums is also <NUM>.

These results demonstrate the advantages of decreasing extraction during exhalation and not having any extraction during inhalation.

Major advantages of the invention include:.

The patient interface <NUM> can connect to a standalone aerosol / high flow therapy device <NUM> by a tubing set <NUM> as depicted in <FIG>. This allows breath-synchronised step-down aerosol delivery. As illustrated in <FIG> a heated humidified air/ O<NUM> mixture is delivered on a tube <NUM>, and flow is split by a valve <NUM> into an aerosol branch <NUM> with a nebulizer <NUM> and a parallel bypass branch <NUM>. The branches merge into a common tube <NUM> which leads to the interface <NUM>.

In some examples, the aerosol delivery path can include an aerosol chamber having an increased volume to slow down the flowrate at the point of aerosol delivery.

The valve <NUM> can dynamically throttle the flowrate, and can dynamically divert the flowrate to provide scenarios such as:.

Step-down aerosol delivery: when switching to the aerosol path <NUM> during inhalation, the average flowrate is reduced. This will improve dose efficiently. The period of reduced flowrate is short to prevent de-recruitment effects. There is a ramp down / ramp up of the reduced flowrate, and these ramps can be controlled / modulated to minimise de-recruitment and discomfort.

The system controller can adapt the baseline extraction to match the high flow therapy setting. The controller can be programmed to dynamically change the extraction rate to match the breath pattern, as illustrated in <FIG>. This can maximise the effectiveness of extraction, and therefore reduce the required extraction rate. This has the benefit of reducing the impact on the treatment pressure, and also reduces the extraction source requirements.

An advantageous part of the extraction system is that there is filtration in line with the extracted airflow to capture any pathogens or drug before it is vented to the ambient room. This can be a standard commercial filter that can be changed out by the clinicians. Due to the large levels of humidity in the expelled gas, the filter will become saturated, and the filter regime adapted accordingly. The system can determine the actual flowrate based off the mask pressure readings. Or, additional flow and pressure sensors could be employed on the system side of the filter. The system can increase the power supplied to the extraction source to keep the extraction flowrate consistent over time as the filter approaches saturation.

A condenser can be employed to take vapour out of the extracted gas prior to it reaching the filter. This can prolong the life of the filter. The condensing mechanism is preferably such that the surfaces that make contact with the extracted gasses are part of a disposable circuit. A heat pump (for example using a Peltier heat exchanger) can be employed to increase the rate of condensing, as illustrated in <FIG>. The heat collected in this exchange can be employed in heating of the high flow therapy delivered to the patient. This would have energy saving benefits.

Claim 1:
An aerosol treatment system comprising:
a patient interface (<NUM>) to cover a patient's mouth and nose,
an aerosol delivery apparatus (<NUM>, <NUM>),
a high flow treatment system (<NUM> - <NUM>) linked with the patient interface (<NUM>),
a controller (<NUM>),
a heater and a humidifier, separately or combined, to provide a heated humidified air/O2 mixture (<NUM>) delivered to the patient interface (<NUM>), and
sensors for detecting patient breathing,
wherein the controller (<NUM>) is configured to control delivery of aerosol to provide breath-synchronised aerosol delivery,
characterized in that the system comprises:
a valve (<NUM>) arranged to split delivery flow into an aerosol branch (<NUM>) with a nebulizer (<NUM>) and a parallel bypass branch (<NUM>), and the branches merge into a common tube (<NUM>) which leads to the patient interface (<NUM>).