U.S. patent number 3,724,172 [Application Number 05/153,612] was granted by the patent office on 1973-04-03 for filtered air breathing zone.
Invention is credited to Walter Bruce Wood.
United States Patent |
3,724,172 |
Wood |
April 3, 1973 |
FILTERED AIR BREATHING ZONE
Abstract
A highly portable, localized filtered air breathing zone for a
patient suffering from those respiratory diseases or who require
protection from air borne contamination. The filtered air in which
essentially all particulate matter has been removed provides a
gaseous envelope in the breathing zone adjacent the top portion of
the patient's bed. In another embodiment, the apparatus is arranged
as to extend longitudinally of the bed and thus provide a patient
zone extending transversely across the bed for essentially its
entire length. The latter modification is to provide an essentially
contamination free patient zone or breathing zone for intensive
care units and for enclosures for small children requiring
contamination free air. The patient zone is isolated from ambient
air by means of three gas patterns, one formed at either vertical
edge of the patient zone and one formed transversely across the top
of the patient zone. These act as relatively high velocity air
curtains and thus shield the center portion of the patient zone
from the surrounding ambient air. A gas pervious diffusion wall is
provided in the apparatus between the areas defined by the three
high velocity gas patterns. This forms the center portion of the
patient zone and provides a positive method for filling the
breathing zone with contamination free filtered air. All of the air
circulated is taken from a purified or filtered air source
preferably derived by impelling ambient air through a high
efficiency filter.
Inventors: |
Wood; Walter Bruce (Anchorage,
KY) |
Family
ID: |
22547944 |
Appl.
No.: |
05/153,612 |
Filed: |
June 16, 1971 |
Current U.S.
Class: |
95/287; 5/284;
5/423; 55/DIG.29; 55/356; 55/385.2; 55/414; 55/467; 128/205.26;
128/205.29; 422/120; 454/188; 600/21 |
Current CPC
Class: |
A61G
10/02 (20130101); A61G 13/108 (20130101); Y10S
55/29 (20130101); A61G 2200/14 (20130101) |
Current International
Class: |
A61G
10/02 (20060101); A61G 10/00 (20060101); A61G
13/00 (20060101); B01d 046/00 () |
Field of
Search: |
;55/97,356,385,414,467,473,DIG.29 ;21/74 ;62/261 ;98/36
;128/1R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Talbert, Jr.; Dennis E.
Claims
I claim:
1. Apparatus for providing a filtered gaseous envelope of air for
isolating a patient zone from an ambient environmental gaseous
medium which comprises: a filtering means, a passage means in
communication with said filtering means and said patient zone and a
motor driven gas impeller for impelling air through said filtering
means and through said passage means;
A. the improvement which comprises:
1. a vertically disposed wall positioned adjacent to said patient
zone, the front face of said wall defining a side of said patient
zone;
2. a gas pattern forming means in communication with said passage
means which comprises:
a. a pair of spaced port means each being vertically disposed
relative to said front face of said wall and each being located in
alignment with one or the other of the lateral edges of said front
face for providing streams of relatively high velocity air to form
the lateral borders of said patient zone;
b. a canopy extending forwardly over a portion of said patient zone
and extending across the top of said wall;
c. a horizontally disposed port means opening near the forward edge
of said canopy for providing a stream of relatively high velocity
air to form the upper border of said patient zone; and
d. a low velocity pervious diffusion wall located within the area
defined by said canopy and said vertically disposed port means for
producing a stream of low velocity air to form a zone embodying the
center portion of said patient zone.
2. Apparatus, as defined in claim 1, in which said vertically
disposed wall is the headboard for a patients bed.
3. Apparatus, as defined in claim 2, in which said headboard
contains a plenum chamber in communication with said passage means
and with said patient zone.
4. Apparatus, as defined in claim 1, the further combination with
said passage means of:
A. a plenum chamber and
B. air directing vanes to direct the high velocity air to said port
means and said low velocity air to said low velocity pervious
diffusion wall.
5. Apparatus, as defined in claim 1, the further combination
therewith of
A. plenum chamber and
B. air directing vanes to direct higher velocity air to the sides
of said low velocity pervious wall and lower velocity air to the
center of said low velocity pervious wall so as to form a zone of
air of variable velocity said zone having a relatively low velocity
in its center and a velocity which increases toward its sides.
6. Apparatus, as defined in claim 1, in which said spaced port
means comprises a series of gas outlet openings arranged in
vertical alignment.
7. Apparatus, as defined in claim 1, the further combination
therewith of a pair of gas impervious side shields extending from
the ends of said wall forwardly to cover a portion of the lateral
edges of said patient zone.
8. Apparatus, as defined in claim 7, in which said port means
comprises a nozzle formed by such shield.
9. Apparatus, as defined in claim 8, in which said nozzle is formed
by said shield and by a cooperating vertically disposed closure
member to form a vertically oriented elongated slit.
10. Apparatus, as defined in claim 1, in which said horizontally
disposed port means comprises a nozzle formed by said canopy near
its forward edge.
11. Apparatus, as defined in claim 10, in which said nozzle is
formed by said canopy and by a cooperating lower closure member to
form an elongated slit which extends across said patient zone.
12. Apparatus, as defined in claim 1, in which said pervious
diffusion wall is a gas diffusion means.
13. Apparatus, as defined in claim 3, in which said pervious
diffusion wall is in communication with said plenum chamber.
14. Apparatus, as defined in claim 13, in which said pervious
diffusion wall includes a diffusing media stretched over said
wall.
15. The process of providing a filtered gaseous envelope of air to
isolate a patient zone from an environmental ambient gaseous
medium, which comprises the steps of:
A. providing a source of filtered air;
B. forming a first and second relatively high velocity rectangular
gas pattern by projecting filtered air so that the direction of
flow of each of said gas patterns project horizontally to form the
lateral borders of said patient zone;
1. each of said gas patterns when viewed in cross section relative
to the direction of flow having a long major axis and a narrow
minor axis in which said major axis is vertically disposed;
C. shielding a portion of the top of said patient zone with a
forwardly projecting canopy means,
D. forming a third high velocity gas pattern of air near the
forward edge of said canopy means by projecting filtered air
forwardly of said canopy means so that its direction of flow is in
a horizontal plane so as to form the top border of said patient
zone,
1. said third gas pattern when viewed in cross section relative to
the direction of flow having along major axis extending
horizontally across said patient zone,
E. forming a fourth rectangular gas pattern of filtered air of
relatively low velocity within the area defined by said first,
second and third pattern, said fourth gas pattern when viewed in
cross section relative to its direction of flow having a long major
axis horizontally disposed and a relatively wide minor axis
vertically disposed, said fourth gas pattern forming the breathing
portion of said patient zone.
16. The process, as defined in claim 15, in which said source of
air is provided by impelling ambient air through a high efficiency
filtering means and thereafter impelling said filtered air to said
patient zone.
17. The processes as defined in claim 16, the further step which
includes:
A. impelling, said filtered air against air directing vanes so as
to increase the velocity of the filtered air going to form the said
first and second air pattern.
18. The process as defined in claim 16, the further step which
comprises:
A. impelling said filtered air against air directing vanes so as to
increase the velocity of filtered air going to form said third gas
pattern.
19. The process as defined in claim 16, the further step which
comprises:
A. impelling said filtered air against air directing vanes so as to
increase the velocity of air toward the lateral edges of said
fourth gas pattern so as to form a velocity gradient across said
gas pattern, said velocity being lowest at the center of the gas
pattern and increasing toward its lateral edges.
Description
BACKGROUND OF THE INVENTION
This invention relates to the provision of a gaseously formed
curtain and is particularly applicable to the provision of an air
curtain so located as to isolate air in a given space from the
surrounding ambient air. More specifically the invention relates to
an apparatus and method for controlling the environment in a
localized zone and more particularly for effectively and
economically isolating a patient zone or a breathing zone from the
external environmental.
DESCRIPTION OF THE PRIOR ART
Patients in intensive care units whether suffering from respiratory
infection, extensive burns or patients under going pre- or
post-operative care for relatively severe or extensive operations
are particularly subject to pathogenic micro organisms. Cross
contamination, even in the most efficiently run hospitals has
continued to exist despite improved aseptic techniques and
anti-biotics. It is known that if the air in the vicinity of a
patient during pre- and post-operative periods is maintained
virtually free from pathogenic organisms, the incidence of
infection is only a fraction of that existing under normally
controlled air conditions. Previously, patients have been isolated
from the bacteria and virous laden air by the physical isolation of
a specific part or even the whole of the patient within a plastic
envelope or enclosure into which is pumped clean, contamination
free air. However, patient morale is adversely affected by total
confinement created by the severe claustrophobic environment of a
plastic tent. Further, nursing care is complicated since direct
physical treatment must be carried out through closed ports or air
locks which demand considerable patience and training of hospital
personnel.
To overcome these severe disadvantages, apparatus has been proposed
which leaves one or more walls open and isolated from the external
atmosphere by reason of an air curtain. Such apparatuses, are
disclosed and claimed by Denny in U.S. Pat. No. 3,462,920, in 1969
and by Truhan in U.S. Pat. No. 3,511,162, in 1970. Both of these,
however, are dependent upon a rather elaborate and expensive
superstructure comprising a plenum chamber located parallel to the
mattress of the patients bed and containing a series of ports or
nozzles directed downwardly onto the patient with high velocity gas
curtains on the peripheral edges of the plenum to isolate the
filtered gaseous environment surrounding the patient from the
bacteria ladened ambient air. Truhan additionally provides for
recycling of the filtered air through a return duct 17 wherein the
air forming the curtain and the patient zone is recycled to
filtering media to be reused in isolating the patient zone.
The use of horizontal air flow in hospital applications requiring
contamination free breathing areas has been accomplished in the
past by installing a bank of filters either at the head or along
the side of the bed and bathing the patient with filtered air flows
of from 90 to 100 feet per minute. These installations have
involved a complete wall fabricated of high efficiency particulate
air filter (HEPA) modules. Each module might be 2 feet in width and
up to 8 feet in height. The installations require an area of at
least 3 to 4 feet behind the filter module bank to service the
filters. The cost of these units is extremely high and the rate of
air flow can be a problem to some patients. The units are not
portable.
SUMMARY OF THE INVENTION
The present invention provides a highly portable unit for
protecting vulnerable patients from air borne bacteria and viral
and other irritating solid particulate contamination. Further, the
present invention provides a relatively inexpensive unit for
protecting only the breathing zone of patients requiring protection
from air borne contamination. The present invention provides a
relatively inexpensive and portable unit for protecting a
vulnerable patient either from bacteria, viral or particulate
contamination so as to isolate the breathing zone of the patient
from contaminated external atmosphere and yet provide easy access
of the patient to nursing and medical personnel. In contrast to
installations presently in use involving an entire bank of filter
modules, a small compact HEPA filter, as for example, one 12 inches
in height and 12 inches in depth can be used with a high rate of
air flow through the filter. Thereafter the filtered air is
diffused so as to flow at relatively low rates into the patient or
breathing zone. By contrast with other developments the present
invention does not direct the air curtain downwardly onto the
patient but provides an air curtain having three borders of rather
high velocity air which project in a generally horizontal direction
to define the top and sides of the patient zone. The center portion
of the patient zone is provided by a relatively low velocity air
pattern obtained through a pervious gas diffusion wall. This in a
preferred embodiment involves a velocity gradient across said gas
pattern. The velocity is lowest at the center of the gas pattern
and increases gradually toward the lateral edges of the breathing
zone. While the unit is primarily adapted for use in providing a
patient or breathing zone near the pillow or top area of the
patient's mattress, and is designed for use by patients requiring
protection from air borne particulate contamination, it is within
the scope of this invention to utilize the apparatus so as to
extend along the length of one side of the patient's bed so that
the patient zone formed by the high velocity gas patterns extend
horizontally across the patient's mattress for virtually the entire
length of the bed. Thus, there is provided in this modification a
patient zone comprising an envelope of purified air physically
isolated from bacteria ladened and environmental air and
encompassing essentially the entire area of the patient's mattress.
Further it is within the scope of this invention to provide a unit
adapted for a chair for use with ambulatory patients who require a
contamination free breathing zone. Because of the novel and
relatively low cost construction of the apparatus of this
invention, an effective patient zone is provided, isolated from the
external environment by use of relatively low velocity air. Thus
the patient is not subject to drafts, noise is essentially
eliminated and there is no claustrophobic effect. The patient is
instantly accessible to medical and surgical care from the top side
or front of the patient zone.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation with parts in section of the device of
this invention in use with a bed and which illustrates in dotted
lines the patient breathing zone as well as portions of the
invention when in tilted position.
FIG. 2 is a fragmentary plan view illustrating in dotted lines the
outer boundary of the patient or breathing area.
FIG. 3 is a sectional view taken along lines 3--3 of FIG. 1 which
illustrates the relation of the plenum chamber, the ports and gas
pervious wall forming the front face of the plenum chamber.
FIG. 4 is a sectional view along lines 4--4 of FIG. 3 illustrating
the structure of the various diffusion members of the gas per vious
diffusion wall and illustrating the direction of air flow through
the plenum chamber.
FIG. 5 is a view in perspective illustrating the apparatus of this
invention extending longitudinally over a bed to protect the entire
mattress area for use as an intensive care unit.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1 a typical hospital bed 1, including a
mattress 2 is shown in full lines. Behind the bed is a blower and
filter package 4 and duct 5 which connects to the plenum headboard
10 to distribute air into the breathing or patient zone 7. It will
noted in FIG. 1 that canopy 11 extends forwardly from the plenum
headboard and side shield members 12 extend diagonally from the
forward edge of canopy to the plenum headboard 10 at about mattress
level. It is well known that hospital beds are pivoted so as to
allow the patient to adjust the mattress to sitting, reclining or
sleeping positions. This is shown in dotted lines in the FIG. 1
showing that the relationship of the headboard 10 and the canopy 11
relative to the top portion of the mattress remains constant even
though the angular disposition of the mattress changes in well
known manner. The fragmentary plan view illustrated in FIG. 2
illustrates the outer boundary of the patient zone 7 relative to
the canopy 11.
Referring now to FIG. 1, air is pulled into the filter blower
package 4 through air intake (not shown). Contained in the filter
blower package 4 is a blower or gas impeller and a high efficiency
filter. Such high efficiency particulate air (HEPA) filters are
well known in the art and have been shown to remove 99.97 to 99.99
of all particles and bacteria, 0.3 microns in diameter and larger.
Smaller particles are also removed by this type of filter but the
amount of removal of these particles has not been established.
Removal of smaller particles is not a matter for significant
concern, however, since most bacteria range from 0.5 to 25 microns
in diameter and very rarely exist in the air as single unattached
cells but are usually attached to particles of dust and skin scales
considerably larger than themselves. Typical diameters for
particulate matter includes the following: tobacco smoke, 0.01 to
0.4 microns; bacteria and spores, 0.5 to 25 microns, pollens, 10 to
100 microns, insecticide dust, 0.5 to 10 microns, sneeze droplets,
10 to 400 microns, foundry dust, 1 to 1,000 microns. One of the
organisms chiefly responsible for post-operative infection is the
hemolytic Staphylococcus aureus which is generally considered to be
approximately 0.8 microns in diameter. Thus by use of the HEPA
filters essentially all of these irritating and pathogenic
organisms are removed from the atmosphere. The purified air is
impelled through duct 5 to the plenum headboard 10. It is directed
by the V shape air directing vanes 25 and by the median air
directing vane 26 to the upper portions of the plenum chamber 24.
At the forward part of the canopy 11 is a horizontal port means 15
formed by the canopy 11 and the lower closure member 16 to form an
elongated slit horizontally disposed relative to the mattress 2 and
extending transversely across the mattress. High velocity air
issuing from this horizontal port forms an air pattern which
direction of flow is parallel to the top of the mattress 2 and
which has its long axis directed transversely across the mattress.
The side ports 17 are made up of a series of jet openings 18 which
are vertically aligned along the side edges of the plenum chamber
24. Thus the air pattern formed by high velocity air issuing in
horizontal direction along the length of the mattress 2 may be
considered rectangular. In any event, when viewed in section
relative to the direction of flow the longitudinal axis of the air
pattern is vertical and forms the lateral edges of the patient
breathing zone 7.
The pervious diffusion wall 20 (which is defined by the sideport
means 17 and the horizontal port means 15) comprises a perforated
diffusion cloth media 21 covering a supporting wire screen 22 and a
perforated aluminum plate 23 containing about 43 percent openings.
The gas pattern formed through the pervious diffusion wall varies
from 10 FPM (feet per minute) in the center to 40 to 50 FPM along
the vertical edge.
The variation in exit velocity from the pervious diffusion wall 20
is accomplished by gas directional vanes such as 25 and 26 and by
the manipulation of non-porous blanking material over the diffusion
media 21 to direct the air flow to vertical edges as required. The
lowest velocity gases are in the pillow area and the higher
velocity gases gradually increase as the pattern approaches the
lateral edges adjacent to the side port means 17.
As previously mentioned, the primary purpose of this invention is
for patients suffering from respiratory illness, such as asthma.
Nevertheless, it is within the scope of this invention to arrange
the plenum chamber 10 and the canopy 11 and the side shields 12 so
that the unit extends longitudinally from head to foot of a
patients bed so that the (filtered air) zone extends across the
entire mattress.
Referring now to FIG. 3, it has been found that in order to
maintain the integrity of the air curtains or air patterns that the
velocity of the issuing from the side port means 17 and from the
top horizontal port means 15 should be in the range of 100 to 200
feet per minute with a total of about 300 CFM of filtered air
exhausting from all outlets in headboard 10.
Good results have been obtained by utilizing 1/4 inch diameter jet
openings 18 spaced 1 inch on center in side port 17 with the top 25
percent of the holes blocked off. Further, the jet openings 19,
supplying horizontal slot 15 are one-fourth inch in diameter
located one-half on centers with every third opening closed. Air
velocity can also be regulated by increasing or decreasing fan
speeds; opening or closing the jet openings 18 or 19 or by other
techniques known to the art.
The effectiveness of the invention is well demonstrated by test
data measuring the integrity of the breathing zone 7 while
operating in a normal contaminated area. The background of
contaminates making up the ambient air surrounding the bed during
the test consisted of the following particle counts per cubic of
air sampled.
81,000 particles 0.5 microns or larger 18,000 " 1.0 " 800 " 2.0
"
These measurements were made using a Baush and Lomb Counter (40-1)
with digital readout.
The test measurements of the contamination level surrounding the
open end of the breathing zone 7 were taken by establishing an
imaginary grid parallel to the pervious diffusion wall 20 and
taking a reading every inch in the vertical and horizontal planes.
The grid was first taken one inch from the outer most edge and
gradually moved away from the face of diffusion wall 20. It was
determined that the high velocity jet action of the horizontal air
pattern from part 15 prevented 0.5 micron and larger particles from
entering the breathing zone 7 for almost the full height of the
diffusion wall 20 as far as 20 inches downstream from plate 23
along the centerline of the bed. However, as the grid was moved
away from the wall 20 particulate matter started to penetrate the
vertical air patterns formed by side ports 17 on each side of the
bed. The following measurements were taken in the grid plane 17
inches down from the wall 20. (These figures were chosen since 17
inches provides a more than ample breathing zone for the patient.)
All the readings were zero in a zone extending from 2 inches below
the top edge of canopy 11 from the center of mattress to 3 inches
from the side edge of the bed. All readings 4 inches from the edge
of the bed, in an area extending vertically from canopy to 3 inches
above the mattress, were zero except for 1 which read 100 particles
of a size 0.5 microns and larger. At a height of 3 inches above the
mattress particle counts for 0.5 microns diameter particles of 300
to 900 per cubic foot were obtained at the lateral border 8 inches
from the edge of the bed. The particle count at mattress level is
believed to result from particles shed from the sheet. It should be
that the particle counts at 3 inches from the edge of the bed
averaged 800 which is far below the ambient level of 81,000
particles per cubic foot.
The same procedure was followed testing for particles having
diameters of 2 microns and larger and it was determined that 24
inches downstream from the perforated plate 23, a zero count was
found. This zone extended from 2 inches below the canopy to the top
of the mattress with no reading at 1 inch above the mattress. The
zone defined by the air patterns, produced by side port 17 and top
port 15 are such that the entire center area of the patient
breathing zone 7 is essentially completely free of particles of 0.5
micron diameter or above, at a distance of 17 inches from the
headboard 10 and completely free of 2 micron and larger particles
at a distance of 24 inches from the headboard 10. Therefore, as
previously indicated, essentially all pathogenic organisms will be
shielded from a zone extending from 1 to 17 inches away from the
headboard and basically all bacteria, pollen and spores will be
shielded from the breathing zone, extending for a distance of from
1 to 24 inches, from the headboard 10. In other words the
contamination free zone for 0.5 micron diameter material is 7
inches shorter than the zone for 2 micron diameter material, but in
any event is more than ample as a breathing zone for a patient. All
of the experiments were run with a side shield 12 in place but
without a closure member similar to closure member 16 to direct the
air. It was found, however, that it was necessary to extend closure
member 16 for 10 inches from the perforated plate 23 to be
effective. The canopy 11 extended 14 inches forwardly of headboard
10 while, as previously indicated, the effective contamination free
breathing area 7 extended forwardly from 17 to 24 inches.
It is clear, that by providing a canopy 11 with a forwardly
extending horizontally disposed port 15 near the forward edge of
the canopy and providing port means at the forward edge of the side
shields 12 that the effective zone of the mattress could be
extended so that when the unit is disposed longitudinally the
entire mattress could be isolated from the surrounding environment.
Of course, it is also possible to increase the velocity of gases
extending from the port means to extend the breathing zone.
By utilization of the relatively low velocity of purified gases the
unit runs quietly, drafts are essentially eliminated and the cost
of the unit and operating expenses are relatively low.
Many modifications will occur to those skilled in the art from the
detailed description here in above given and such modifications are
meant to be exemplery in nature and non-limiting except so as to be
commensurate in scope with the appended claims.
* * * * *