Surgery – Respiratory method or device – Means for mixing treating agent with respiratory gas
Reexamination Certificate
2002-05-17
2004-06-15
Dawson, Glenn K. (Department: 3761)
Surgery
Respiratory method or device
Means for mixing treating agent with respiratory gas
C128S205250, C128S206210, C128S206240, C128S206280
Reexamination Certificate
active
06748949
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mask and more particularly, to a face mask for use in delivering an aerosolized drug or the like to a patient.
2. Description of Related Art
Masks are commonly used in a wide range of applications and have widespread use in a number of medical settings. For example, masks are typically used in administering gases to a patient, e.g., an anesthetic agent, and more recently, masks have been increasingly used in drug delivery systems, including nebulizer drug delivery systems and metered dose inhalers using valved holding chambers (MDI/VHC). Nebulization is the application of a drug to a patient by means of an aerosol produced by a flow of gas. The aerosol and the drug are breathed in through the mask and are administered into the respiratory system of the patient as the patient inhales. The MDI/VHC creates its aerosol from the expansion of a volatile liquid into a gas within the VHC.
Nebulization is particularly used in the pediatric field as a means for delivering a drug or the like. In patients, such as young children, who have limited cooperation and attention span, the delivery of an aerosolized drug is carried out primarily with the use of a face mask. The face mask is placed over the nose and mouth of the patient, held in place by a caregiver or by using conventional straps or the like. The face mask is attached to an aerosol drug delivery device. In the case of nebulizers, the face mask is pressurized by the flow from the nebulizer and aerosol fills the mask becoming available for inhalation via the nose or the mouth. When the patient inhales, a negative pressure is applied to the face mask reservoir and the aerosolized drug is inhaled and enters into the respiratory system of the patient.
Metered dose inhalers are also used with face masks to disperse a drug to a patient. These devices dispense a predetermined amount of drug when activated and the patient is required to inhale in order to draw the aerosolized drug into the face mask reservoir and subsequently into the respiratory system of the patient.
Nebulizer drug delivery is different from drug delivery using a metered dose inhaler particularly in the degree of pressurization of the face mask. Metered dose inhalers can pressurize the mask to some degree, especially if aerosol is sprayed directly into the mask and a spacer is not used. A spacer is a device which is placed between the face mask and the source of aerosol (typically a bottle). Often, the spacer has one way valves and therefore is called a “valved holding chamber” (VHC). Face masks are used for both nebulizer drug delivery and for metered dose applications, but there are several associated shortcomings.
Nebulizers readily pressurize the mask and deliver more drug but leaks around the face are enhanced, resulting in increased facial deposition of the drug. Thus, leakage around the mask affects the performance of the particular device and in the case of nebulizers, leakage actually enhances the delivery of the drug; however, it is enhanced at the price of increased facial deposition and potentially local side effects. In order to effectively administer the aerosolized drug into the respiratory system of the patient, the face mask should cover the entire mouth and nasal openings of the patient.
The face mask is generally arranged so that it seats against the cheeks of the patient and extends across an upper portion of the bridge of the patient's nose. Because the bridge of the nose is elevated relative to the rest of the patient's face, e.g., cheeks, the upper portion of the face mask is slightly elevated relative to surrounding portions of the face mask which extend across the cheeks and under the mouth of the patient. This occurs even when the patient attempts to produce a tight seal between the mask and the face. For nebulizers, this produces certain leakage areas where the aerosolized drug can be discharged underneath the face mask and into the atmosphere. Because of the design of face masks and their above-described placement over the face, leakage is universally present in the perinasal areas on either side of the nose. This results in a jet of leaked aerosol being oriented and deposited directly into the eyes of the patient. In other words, aerosol is discharged underneath the face mask in these perinasal areas and flows directly towards the patient's eyes and unfortunately, many of the conventional masks are constructed in such a manner that the leaks that do occur are characterized as being high powered leaks (high kinetic energy) due to the high velocity that the fluid has as it flows underneath the mask and along the face directly into the eyes.
This may lead to several undesired side effects. For example, deposition of the leaked aerosolized drug may be associated with direct trauma to the eyes and associated structures. As leakage occurs, these organs are exposed to the aerosolized drug. There is speculation that the risk of developing cataracts increases as a result of aerosolized drugs being directly deposited in the eyes of the patient. At the very least, leakage of aerosolized drugs causes discomfort as the aerosol, traveling at a great velocity, is discharged underneath the face mask and deposits in the perinasal areas, including the eyes. In addition, leaks of certain aerosols can cause dermatological problems in some patients due to an adverse reaction between facial skin and the aerosol. Other undesirable conditions may result from having the aerosolized drug leaking and being deposited onto the face.
The disadvantages associated with conventional mask constructions are readily apparent by viewing
FIGS. 1
,
1
a
and
2
.
FIG. 1
is a front perspective view of a typical face mask
10
(that is commercially available from Laerdal Medical Corporation of Wappingers Falls, N.Y.). While, the face mask
10
is illustrated as being worn by an adult in
FIGS. 1 and 1
a
, it will be understood that face mask
10
is designed to be worn by small children and finds particular application in pediatric care where the patient is unable or uncooperative in the administration of the drug. The face mask
10
has a body
12
including a peripheral edge
14
which is intended to engage a face of a patient. The body
12
defines a face mask reservoir in which the patient's nasal openings and mouth are in communication. The body
12
is typically made of a flexible material, such as a thermoplastic, e.g., a PVC material. The body
12
has a central opening
16
defined in part by an annular flange-like member
18
which extends outwardly from an outer surface
19
of the body
12
. During use, the member
18
is coupled to other components of a drug delivery system (not shown) to permit delivery of the aerosolized drug. The opening
16
serves as a means for delivering the aerosolized drug to the patient. Depending upon the type of drug delivery assembly that is being used, e.g., a metered dose inhaler or a nebulizer system, the opening
16
receives the aerosolized drug as it is transported to the face mask reservoir defined by the body
12
. The breathing action of the patient causes the aerosolized drug to be inhaled by the user and introduced into the patient's respiratory system.
As previously mentioned, one of the deficiencies of the face mask
10
is that leakage areas form around the peripheral edge
14
. More specifically, the peripheral edge
14
does not form a complete seal with the face of the patient and accordingly, leakage flow paths
17
with high local velocities are formed at certain areas along the periphery of the face mask
10
, especially in perinasal areas
15
. In fact, maneuvers to reduce leaks along edge
10
may increase the velocity of leaks in perinasal areas
15
. The perinasal areas
15
are particularly prone to the formation of leaks and this results in the aerosolized drug being discharged directly into the eyes and the associated structures. As previously mentioned, there are at least two different types of a
Darby & Darby
Dawson Glenn K.
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