Nebulizers

Details Nebulizers Nebulizers

1999-01-04

2002-04-09

Dawson, Glenn K. (Department: 3761)

Surgery

Liquid medicament atomizer or sprayer

C128S200240, C128S203120, C128S203250

Reexamination Certificate

active

06367470

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to nebulisers.
2. Brief Description of Art
Many different types of nebulisers are known for delivering medication directly into the lungs of a patient, usually for treatment of respiratory diseases. Nebulisers normally deliver medication in the form of droplets or a dry powder. In most nebulisers, atomisation of the medicament into a stream of air occurs continuously, regardless of whether the patient is inspiring or expiring. However, the effect of continuous atomisation is that a significant proportion of medication is lost during expiration.
Commonly known nebulisers are either pneumatically operated from a compressed air source connected to the nebuliser which atomises the liquid, or are ultrasonic nebulisers which use a piezo-electric crystal to atomise the liquid. More recently, a mesh-type nebuliser has been developed in which the medication is forced through a fine mesh in order to create droplets of the medication. The optimum diameter of medication particles or droplets is about 1-5 microns. If the particles or droplets are bigger than this, they are likely to be impacted in the airway before they reach the lungs, but if they are smaller than one micron, they tend to be carried out of the lungs again on exhalation without sedimenting in the lungs.
One known nebuliser analyses the pressure changes within the device during the first three breaths to determine an average shape of the breathing pattern. A timed pulse of atomisation is commenced upon start of subsequent inspirations such that atomisation occurs for the first 50% of the inspiration. This is illustrated in
FIG. 1
where the breathing pattern and pulse are superimposed. This is effective in reducing the loss of medication during exhalation to about 3%.
FIG. 1
shows the breaths in a graph of flow rate against time. When the treatment is commenced, a patient breathes in and out three times through the nebuliser before treatment commences. The first three breaths are measured so that the timed pulse of atomisation occurs for 50% of the average time of inhalation. The duration of inhalation is indicated as T
1
, T
2
and T
3
. These timed periods are averaged, and divided by two in order to determine the pulse length for the next fourth breath where treatment starts. For each subsequent breath, the duration of the pulse of atomisation is determined by summing the time period of inhalation of the previous three breaths, dividing by three to obtain an average and dividing by two. The dose administered to the patient is directly proportional to the duration of the pulse of atomisation, and so the period of atomisation is summed, and the atomiser is switched off, or indicates that the patient should stop once the dose administered to the patient reaches the amount of medication prescribed for that treatment.
Other nebulisers are known in which the timed pulse of atomisation is other than 50% of the duration of inspiration. However, in these other nebulisers, the pulse length must be set for each patient by the clinician. Many of the nebulisers are, therefore, suitable only for use in a controlled environment, such as a hospital. The setting of the pulse length for each patient means that most nebulisers are not suitable for a patient to use at home.
Reference is made to International Patent Publication No. WO 97/48431, the contents of which are hereby incorporated by reference in its entirety. In addition,
FIGS. 2 and 3
of this application show the nebuliser which is disclosed in the above International Patent application. Referring to
FIG. 2
, a mouthpiece
1
is shown through which a patient inhales in the direction of arrow
2
. Below the mouthpiece
1
is a removable atomising section
3
which, in turn, rests on a base
4
.
The base
4
is shown in more detail in FIG.
3
. Referring to
FIG. 3
, the base
4
includes an inlet
5
through which air is supplied under pressure from a compressor (not shown). The pressurized air is led via a tube
6
to a manifold
7
which controls the flow of pressurized air to an air outlet
8
which directs air into the atomising section
3
shown in FIG.
2
. The base
4
also includes a pressure sensor
9
which detects the pressure within the atomising section
3
via a port
10
electronic circuitry and a battery. The port
10
connects the pressure sensor
9
to the inside of the mouthpiece. This is attached to a printed circuit board
17
which is powered by the battery
19
. When the pressure sensor detects that a patient has inhaled, the electronic circuitry controls the manifold
7
to divert pressurized air to the air outlet
8
.
Referring again to
FIG. 2
, air under pressure passes through the air outlet
8
of the base
4
and is conducted through a tubular post
11
to an atomiser nozzle
12
out of which the air issues under pressure. A deflector
13
is located in the path of the pressurised air issuing from the nozzle
12
so that the pressurized air is deflected laterally so as to pass beneath a baffle
14
. The passage of the pressurized air across the top of the tubular post
11
causes medication
15
to be drawn up between the outer surface of the tubular post
11
and the inner surface of a sleeve
16
which surrounds the tubular post
11
. The medication
15
is atomised in the stream of air, and carried away in the stream of air below the rim of the baffle
14
and up through the mouthpiece
1
to a patient.
The pressure sensor
9
in the base
4
monitors the breathing pattern of a patient, and on the basis of the breathing pattern, the manifold
7
is controlled by the electronic circuitry to supply pressurized air to the atomising section
3
only during the first 50% of an inhalation phase incorporated in WO 97/48431.
BRIEF SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a nebuliser comprises means for determination of the duration of a pulse of atomisation during inspiration, the determination means including means for measuring the tidal volume of a patient, timing means for measuring the duration of inspiration, means for storing an estimate of the volume of a patient's upper airway, and means for calculating the duration of the pulse on the basis of the tidal volume measured by the tidal volume measuring means, the duration of inspiration measured by the timing means, and the stored estimated volume of a patient's upper airway from the storage means.
According to a second aspect of the invention, a method for determining the duration of a pulse of atomization during inspiration during operation of a nebuliser comprises:
(i) measurement of the tidal volume of a patient;
(ii) measuring the duration of inspiration of a patient;
(iii) storing an estimate of the volume of a patient's upper airway; and
(iv) calculating the duration of the pulse on the basis of the measured tidal volume of the patient, the measured duration of inspiration and the stored estimated volume of the patient's upper airway.
The means for calculating the duration of the pulse on the basis of the tidal volume is preferably comprised of a microprocessor, and the microprocessor might also be one of the elements of the tidal volume measuring means. The means for measuring the tidal volume of a patient includes a breathing sensor, which is preferably a peak flow sensor, but could be any one of a number of known sensors such as a pressure sensor. If a pressure sensor or the like is used, the microprocessor can determine to flow rate of each breath from the output of the sensor. From the sensor output it can determine the tidal volume. Associated with the microprocessor is an electronic memory in which data is stored, and in which is stored an estimate of the patient's upper airway, thereby constituting the means for storing an estimate of the patient's upper airway.
In this document, the upper airways of a patient are the mouth and trachea, and preferably include the volume of the nebuliser chamber.
The determination of the length of pulse o

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