Valved auxiliary device for use with aerosol container

An auxiliary device is provided for use with a metered-dose aerosol device. The auxiliary device comprises a chamber having an inlet adapted to receive the metered-dose aerosol device, and an outlet. A mask adapted to communicate with the nose and/or mouth of an infant or young child communicates with the chamber outlet via a first valve which permits the infant or young child to inhale aerosol-carrying air from the chamber, and communicates with atmosphere via a second valve permitting exhalation therethrough. The distance between the chamber inlet and the chamber outlet is such that the mass percentage of aerosol particles having a diameter of from 1.0 microns to 5.0 microns is substantially a maximum at the chamber outlet, and the volume of the chamber is from 200-500 ml.

BACKGROUND OF THE INVENTION 
This invention relates to an auxiliary device for use with a metered-dose 
aerosol container, either with or without an actuator. The aerosol 
container, with or without actuator, is referred to below as a 
metered-dose aerosol device. In particular, the invention relates to a 
spacer device to be attached to a metered-dose aerosol device for use in 
infants and young children to enable them to inhale medicaments such as, 
for example, bronchodilators and corticosteroids. 
There are a substantial number of infants and young children generally 
termed "wheezy infants" who suffer from wheezy bronchitis, and other 
bronchopulmonary diseases such as respiratory distress syndrome due to 
post hyaline membrane disease and broncho-pulmonary dysplasia or neonatal 
pneumonia. These diseases if left untreated will in a significant number 
of cases develop into asthma. These conditions and other conditions such 
as cystic fibrosis will respond to treatment with for example, inhaled 
bronchodilators and corticosteroids provided there is a suitable device 
able to administer the medicaments so that they can reach the lungs of the 
infants and young children. 
Administration of medicaments to infants and young children by inhalation 
is currently carried out using electric nebulisers but these devices have 
the disadvantage that they cannot be used with infants at home or the 
medicaments have to be administered over a time consuming period for 
example up to 10 minutes making it difficult to obtain the cooperation of 
the infant. It can be appreciated that if treatment is to continue for 
example, 3 or 4 times a day, this can be inconvenient. There is also 
considerable loss of medicament with this method of administration. 
Existing large volume spacers, typically having a volume of about 750 ml, 
which are on the market when used for infants and young children have the 
disadvantage that the volume is too large for the infants' lungs and the 
inlet valve has too high a resistance and does not work in a vertical 
position for use in infants. 
It has been proposed to provide a spacer device for use by infants and 
young children. However, only one such device is commercially available 
anywhere. This device uses a chamber having a volume of about 140 ml which 
is adapted at one end to receive the outlet of a metered-dose inhaler. The 
chamber is 110 mm long, and at its other end it communicates via an 
inhalation valve, which is in the form of a slit membrane, with a mask 
intended to be placed over the nose and mouth of an infant or young child. 
This device, however, has several disadvantages, the appreciation of which 
forms part of the present invention. Thus, it has been found that the 
inlet valve does not open sufficiently to enable the infants to inhale 
sufficient medicament. Also, a disadvantage has been appreciated in that 
because there is no separate exhalation valve the exhaled air can only be 
released by leakage around the edge of the mask. 
SUMMARY OF THE INVENTION 
The device of the present invention has been specially tailored for infants 
and young children and aims to avoid or at least mitigate some or all of 
the above mentioned disadvantages. 
According to the present invention there is provided an auxiliary device 
for use with a metered-dose aerosol device, the auxiliary device 
comprising means defining a chamber having an inlet adapted to receive the 
metered-dose aerosol device, and an outlet; administration means adapted 
to communicate with the nose and/or mouth of an infant or young child and 
communicating with the chamber outlet via a first valve which permits the 
infant or young child to inhale aerosol-carrying air from the chamber, and 
communicating with atmosphere via a second valve permitting exhalation 
therethrough; the distance between the chamber inlet and the chamber 
outlet being such that the mass percentage of aerosol particles having a 
diameter of from 1.0 microns to 5.0 microns is substantially a maximum at 
the chamber outlet, and the volume of the chamber being from 200-500 ml. 
The administration means is preferably an inhalation mask adapted to be 
positioned over the nose and mouth of the infant or young child, and for 
practical purposes a mask is essential when the infant is under 2 years of 
age, or of a size which one would expect in an infant under 2 years of 
age. 
The ensuing description will refer simply to use by an infant. It is to be 
understood, however, that use by a young child, too old properly to be 
called an infant, is also covered by the present invention. By "infant or 
young child" we mean those up to and including 4 years of age, or of a 
size which one would expect in an infant or young child up to and 
including that age.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The embodiment of FIG. 1 comprises an elongate tube 1 of cylindrical 
cross-section. The: tube may conveniently be made of a transparent 
plastics material, such as an acrylic material. The transparency of the 
material allows the adult supervising the child to observe that the 
inhalation valve (see below) is working correctly. The tube 1 defines a 
chamber 2 having a volume of from 200 to 500 ml, preferably from 250-350 
ml. A particularly preferred volume for use with one of the aerosol 
containers with which the invention may be used, namely Ventolin 
(salbutamol) is 350 ml, and details of this are given below. The distance 
down the tube from where the spray leaves the aerosol container (see 
below) to the downstream end of the tube is indicated in FIG. 1 by l and 
the internal diameter of the tube by d. Since, with the aerosol container 
in position, the point where the spray leaves it is substantially at the 
upstream end of the tube, the distance l is substantially the length of 
the chamber, and it is so referred to below and shown in FIG. 1 of the 
drawings. The significance of the volume and length of the chamber are 
discussed in more detail below. 
The chamber is provided at its inlet end with walls 3 which are directed 
longitudinally inward and which are adapted to grip an outlet spout 4 of 
an actuator 5 inserted therein. The actuator receives a metered-dose 
aerosol container 6 therein which is adapted, when depressed, to dispense 
a metered dose of a medicament-containing aerosol through the outlet spout 
4. The aerosol container 6 may be a can of known type and the actuator 5 
may also be of known type, and the details of both are not relevant for 
the purposes of the present description, except that, as explained further 
below, the dimensions of the chamber 2 depend on the choice of aerosol 
actuator and aerosol container. Typically, the pressure within the aerosol 
may be from 40-110 psi (276-758 kPa), for example from 50-60 psi (345-414 
kPa), the pressure being measured at 20.degree.-25.degree. C. 
At its outlet end, the chamber is provided with a valve 10 which is adapted 
to open when the infant inhales and which is therefore referred to below 
as the inhalation valve. The valve 10 comprises a disk 11 which is biased 
into a closed position in which it bears against an annular seat 12 by 
means of a spring 13. The spring is trapped between the disk 11 and a pair 
of cross-wires 14 (see especially FIG. 3). Various alternative types of 
inhalation valve may be used, for example a cone-diaphragm valve (see FIG. 
4). 
The inhalation valve should be so constructed as to open once the pressure 
on the outlet side is less than that on the inlet side by a low value, 
preferably not more than about 0.03 kPa. The flow resistance of the valve 
should also be low, preferably not more than about 0.02 kPa/l/s for a flow 
rate of 75 ml/s. 
The device is provided with a further valve 15 which opens when the infant 
exhales and closes during inhalation, and which is referred to herein as 
the. exhalation valve. The valve 15 comprises a disk 17 trapped within a 
cylindrical chamber 18. It is advantageous for the chamber 18 to be made 
of a transparent or translucent material so that it can be seen that the 
valve is working correctly. During inhalation the reduced pressure on the 
lower side of the disk causes it to close a passageway 19 by which it is 
connected to the interior of the device, and thus to prevent air being 
inhaled through the passageway. During exhalation, when the valve 10 is 
closed, the increased pressure in the passageway 19 causes the disk 17 to 
rise and permits the air exhaled by the infant to pass through the 
passageway 19 and thence out through an array of apertures 20. The flow 
resistance of the exhalation valve should be sufficiently low that the 
positive end-expiratory pressure created thereby does not exceed about 
0.05 kPa. 
It is desirable that the dead space within the valve arrangement should be 
as small as possible, i.e. the space in the volume defined between the 
valves 10 and 15 and the region where the mask is attached, and in an 
actual example this was 16 ml. 
The fact that an exhalation valve is provided in addition to an inhalation 
valve, unlike the known commercially available device referred to above 
which has an inhalation valve only, provides a significant benefit. The 
known device relies on leakage around the edge of the mask to permit 
passage of exhaled air, and if this is insufficient an attendant, for 
example a parent of the infant, must alternately withdraw the mask from 
the face and replace it, in unison with the breathing of the infant. 
To permit use by an infant a mask 30 is provided which is of a suitable 
size and shape to cover the nose and mouth of the infant. 
The device is conveniently made in three detachable units, to facilitate 
manufacture and cleaning. The tube 1, including the walls 3, constitutes 
one unit. The mask 30 constitutes a second unit. The remainder of the 
device, i.e. the portion which carries the valves 10 and 15, constitutes a 
third unit. The fact that the mask is removable means that as the child 
grows the mask can be removed and replaced with a larger sized mask. 
Reference has been made above to the significance of the dimensions of the 
chamber 2, and this will now be explained further. 
Firstly, the volume of the chamber is important. The tidal volume of 
inhalation of an infant is normally 5-8 ml/kg body weight. However, 
infants in respiratory distress have a tidal volume approximately equal to 
from 7-14 ml/kg body weight. The volume of the chamber should be 
substantially greater than the tidal volume of the user, and should 
preferably be from 5 to 15 times the tidal volume, more preferably 5 to 10 
times. 
It has been found in an investigation of the breathing of twenty infants 
with brocho-pulmonary disease that, on average, even during respiratory 
distress, they took from 4 to 11 breaths (mean value 7.0.+-.2.2) every 10 
seconds. The infants investigated were aged from 0.8 to 18.8 months and 
had weights of from 2.86 to 12.3 kg. Over a period of 10 seconds, the 
total volume inspired exceeded 350 ml in the case of 80% of the infants, 
and in no case did the volume fall below 200 ml. 
Secondly, the length of the chamber is important. In an aerosol, the 
aerosol particles cover a range of sizes and it has been found that the 
size distribution varies with the distance from the valve orifice of the 
aerosol container. The size of particles inhaled by the user should, as 
far as possible, lie between 1.0 microns and 5.0 microns. Particles 
smaller than 1 micron in diameter tend to be exhaled. Particles greater 
than 5 microns in diameter tend to be deposited before reaching the lungs. 
It has been found that the distance from the valve orifice at which the 
mass percentage of particles in the desired size range is at a maximum 
varies from case to case, though in all those studied so far the optimum 
distance is significantly greater than the distance of 110 mm present in 
the commercially available device referred to above. Tests have been 
carried out on three bronchodilator metered dose inhaler suspension 
aerosols, namely Ventolin (salbutamol), Berotec (fenoterol) and Bricanyl 
(terbutaline), (Ventolin, Berotec and Bricanyl are Trade Marks). These 
tests showed that the maximum mass percentage of particles between 0.5 
microns and 5 microns was achieved at 230 mm for Ventolin (54%), at 130 mm 
for Berotec (45%) and at 280 mm for Bricanyl (56%). 
In a particular spacer device of the type shown in FIG. 1, intended for use 
with Ventolin in an aerosol container at a pressure of about 50 psi (345 
kPa), l was 230 mm and d was 44 mm. Consequently, the volume of the 
chamber was 350 ml. 
It is believed that the optimum distance, depends, inter alia, on the 
pressure within the aerosol container, the design of metering valve used 
in the aerosol container and the design of the nozzle of the aerosol 
dispenser. For any particular case the optimum distance can be determined 
by routine experimentation. In addition to the medicaments referred to 
above, the device of the present invention can, of course, also be used 
for other medicaments which are to be inhaled, for example those sold 
under the trade marks Becotide, Becloforte and Yentide. 
In the modified valve 10' shown in FIG. 4, the components which correspond 
generally to components shown in FIGS. 1 to 3 are denoted by the same 
reference numeral but with the addition of a prime. It will be seen that 
the valve 15' is located inwardly compared to the valve 15, so as to 
reduce the risk of its being damaged in use. The disk 11 is replaced by a 
cone-type diaphragm valve 11'. 
Various other modifications may be made to the device described. For 
example, the illustrated tube 1 may be replaced by a tube which consists 
of a plurality of telescopically arranged sections, whereby the length l 
can be varied according to the nature of the aerosol container and 
actuator being used.