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Description  |
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BACKGROUND OF THE INVENTION
This invention relates generally to patient support apparatus, and in
particular to method and apparatus for protecting a patient's head, neck
and face during a surgical procedure that is performed while the patient
is lying in a prone position or seated leaning forward.
During some surgical procedures, it is necessary to support a patient in
the prone (face down) position on an operating table. For example, the
prone position is used during the following procedures: back surgery,
laminectomies, fusions, instrumentations, scoliosis surgery,
hemorrhoidectomies, colorectal surgery, Achilles tendon repair, decubitus
ulcer debridement, myocutaneous flaps, hip surgery, neck surgery, spinal
tumors, removal of Baker's cysts, calcaneal fractures and the like.
A continuing difficulty facing the medical practitioner, when positioning
the patient so that pressure is exerted on his face, is avoiding injury to
the patient's head and face. There are many well-known complications that
can occur if the patient's face and head are not positioned or supported
properly. These complications result from the continued interruption of
blood flow to soft tissue areas, and include the following: soft tissue
necrosis and sloughing with possible infection, necrosis of the
cartilaginous support structures of the nose and ear, corneal ulceration,
conjunctival edema, blindness, central or branch retinal artery occlusion,
and increased intraocular pressure. During the course of surgery in the
prone position, it is necessary to monitor the vital structures of the
patient's face every few minutes so that facial injury caused by
compression of soft, sensitive facial tissue can be avoided.
Moreover, the patient's head must be positioned and his airway must be
properly aligned to accommodate endotracheal instruments used to
administer general anesthetics and oxygen during major surgical
procedures.
A variety of support arrangements have been proposed for supporting a
patient's face and head while the patient is lying in a prone position.
Typically, the patient's head and face are supported between two or more
foam cushions, pillows or towels, with the support members being manually
repositioned every few minutes to relieve the accumulation of pressure on
the patient's sensitive facial tissues. This support arrangement has
obvious disadvantages in that it requires an attendant's close attention
to carefully shift the resting position of the patient's head while
maintaining airway alignment with tracheal intubation equipment. Proper
management of intubation equipment is restricted by the placement of
supporting cushions or towels that obscure the observation of facial
features.
One approach that provides facial support while also allowing close
observation and airway management is disclosed in U.S. Pat. No. 5,220,699.
According to that disclosure, a contoured, inflatable mask is mounted on a
rigid basket that supports a patient's head and face while the patient is
lying in a prone position. The surgical face mask uses an inflatable
chamber for providing soft, cushion support for the patient's forehead and
face. An advantage of that arrangement is that the pressure of facial
engagement is spread over a relatively large, contoured surface. However,
the soft facial tissues are subject to compression injury in that
arrangement, since the facial area of engagement remains unchanged over a
relatively long period of time, thus causing the continuous interruption
of blood flow to those soft tissue areas and various resulting damage.
Another prone support arrangement is disclosed in U.S. Pat. No. 5,287,567
in which a patient's chin and forehead are supported on an inflatable chin
support pad and an inflatable forehead support pad. The soft tissues of
the patient's forehead and chin are subjected to compression injury and
interruption of blood circulation since the areas of skin contact remain
unchanged throughout the procedure.
A similar arrangement for facial support in the prone position is described
in U.S. Pat. No. 5,520,623. In that arrangement, a forehead pad and a chin
pad (neither of which is inflatable) are supported on a rigid basket frame
which maintains the patient's face elevated above a support surface during
a surgical procedure.
Another facial support for a patient lying in the prone position is
disclosed in U.S. Pat. No. 5,269,035 in which a block of soft, closed cell
foam is contoured for conforming, resilient support of the patient's head
and face. U.S. Pat. Nos. 4,504,050 and 4,752,064 also disclose head
support devices for supporting a patient's face in the prone position.
Those support devices are not inflatable and impose a continuous
compression force on sensitive facial, neck and head areas while also
maintaining the patient's head in a fixed position.
Yet another head support arrangement is shown in U.S. Pat. No. 5,044,026 in
which a face pillow is formed by two sponge cylinders that are coupled
together in spaced relation to permit a patient to lie face down in a
prone position with a ventilation passage being formed adjacent the
patient's mouth and nostrils.
Other support arrangements are known for patients needing full body support
to prevent pressure sores, decubitus ulcers, and head and shoulder support
while the patient is in the supine position. For example, U.S. Pat. No.
5,184,365 discloses inflatable support bags that are pressurized for the
purpose of aligning the patient's mouth, pharynx and trachea to
accommodate tracheal intubation in the supine position.
BRIEF SUMMARY OF THE INVENTION
The problems related to continuous or static compression (in terms of
duration and facial location) of soft facial tissue imposed by prior art
support devices are overcome according to the present invention by a
facial support mask having two or more contoured cushions that are
inflatable and deflatable for providing shifting, soft support for the
patient's head, while alternately relieving pressure applied to
pressure-sensitive facial, neck and head areas. The cushions are
inflatable and deflatable independently of each other temporally and
spatially, so that resting pressure imposed on sensitive head, neck and
facial regions is relieved by alternately pressurizing and depressurizing
the contoured support cushions. Moreover, the duration of resting support
for a particular facial location is controllable over variable intervals,
thus providing intermittent as well as discontinuous spatial support for
the patient's head, neck and face.
Pressurized (compressed) air is automatically supplied to the cushions
during predetermined inflation cycles by a controller that controls the
switching action of two-way and three-way control valves. The pressurized
cushions are alternately vented during predetermined deflation cycles by a
controller that controls the switching action of two-way and three-way
control valves. The inflation, deflation and inflation overlap sequences
are manually adjustable, and pressure sensors confirm the pressurization
and depressurizing of each cushion.
The principal support mode of operation is intermittent non-overlapping
time interval pressurization of the cushions. In the preferred embodiment,
a specific sequence of pressurization and depressurization sequences is
provided. In one of those sequences, both cushions are simultaneously
pressurized. However, at no time are both cushions simultaneously
deflated. The reason for simultaneous pressurization as well as
alternating pressurization of the support cushions is to maintain the head
of the patient in a steady position during the transition from one
sequence to the next.
In the preferred embodiment, the cushions are constructed of soft,
resilient tubular membranes. Preferably, the membranes are transparent so
that the anesthesiologist or surgeon can monitor the patient's face,
pressure-sensitive areas, anesthesia equipment and breathing circuit. The
controller is programmable to provide sequential
pressurization/depressurization of the inflatable cushions, as well as
providing simultaneous inflation of both cushions. By this arrangement,
the inflation/deflation sequence and inflation/deflation intervals are
programmable to provide periodic relief of compression forces by shifting
the areas of facial engagement from one contoured cushion to the other,
and by varying the duration of pressure application for each cushion. This
technique minimizes the localized, time-integrated application of pressure
that is detrimental to the patient.
The multiple inflatable cushion arrangement, in which the cushions are
independently pressurizable and deflatable with respect to each other,
satisfies the specific need for a facial support for safely supporting a
patient's head and face while the patient is in a prone position, and also
is compatible with endotracheal anesthesia. The frequency of shifting
support is manually adjustable as needed, but otherwise the inflatable
cushion assembly operates automatically, thus permitting the attendant to
focus his attention on the patient's vital signs while managing anesthesia
equipment.
The features and advantages of the present invention will be further
appreciated by those skilled in the art upon reading the detailed
description which follows with reference to the drawings, wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a facial support device including multiple
inflatable cushions for use during prone anesthesia;
FIG. 2 is a simplified schematic view showing a patient's head in the prone
position being supported by the facial support device of FIG. 1, and
showing the interconnection of an air compressor and controller for
controlling the pressurization and depressurization of the inflatable
support cushions;
FIG. 3 is a top plan view of the facial support device shown in FIG. 1;
FIG. 4 is a sectional view thereof, taken along the lines 4--4 of FIG. 3;
FIG. 5 is a sectional view thereof, taken along the lines 5--5 of FIG. 3;
FIG. 6 is a simplified schematic diagram showing the interconnection of
valves and pneumatic conduits in an automatic sequencing embodiment; and,
FIG. 7 is a simplified electrical block diagram of the controller shown in
FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
In the description which follows, like parts are indicated throughout the
specification and drawings with the same reference numerals, respectively.
The drawings are not necessarily to scale and the proportions of certain
parts have been exaggerated to better illustrate certain structural
features.
Referring now to FIG. 1 and FIG. 2, a facial support mask 10 constructed
according to the present invention is particularly well-suited for use in
combination with a conventional surgical operating table 12 for supporting
the head and face of a patient in a prone position during the performance
of various surgical procedures and/or while the patient is receiving
anesthesia.
The facial support mask 10 includes as its principal components a base
member 14 and first and second inflatable cushions 16, 18. The base member
14, in combination with the inflatable cushions 16, 18 support the
patient's head and face above the support surface of the operating table
12. The combined height of the base member 14 and fully pressurized,
inflatable cushions 16, 18 is selected to provide a comfortable elevation
and orientation of the patient's head in the prone position.
The base member 14 is preferably constructed of a moldable, durable
material, for example polyvinylchloride (PVC). Other moldable materials
such as polyethylene and polyurethane may also be used. Preferably, the
material selected for the base member 14 should be durable, rigid,
transparent and adherable to the support cushions. The base member 14 is
intersected by a large conical cavity 20 which provides clearance for
portions of the patient's face as well as for an endotracheal tube 22. The
base member 14 is also intersected by a transverse notch 24 and a
transverse notch 25 that permit the endotracheal tube to be routed
caudally or laterally across the operating table 12 from the patient's
mouth to an external connection to ventilation equipment.
Referring now to FIGS. 3 and 4, the inflatable cushions 16, 18 are
fabricated from a multi-component, plastic material such as vinyl,
silicone rubber, urethane or the like that is approved for medical use.
Each cushion preferably is in the form of a thin, transparent plastic tube
or membrane that is capable of safely operating at inflation pressures up
to 30 psi or more. Moreover, each cushion is curved and contoured to at
least partially encircle the cavity 20, and the outer cushion 18 at least
partially encircles both the inner cushion 16 and the cavity 20. For this
purpose, the inner inflatable cushion 16 is provided with a curved crown
portion 16A and wing portions 16B, 16C that are curved for a close
conforming fit with the forehead and side portions of a patient's head and
face.
As shown in FIG. 2, the inner cushion 16 may at least partially engage the
bridge of the patient's nose. The outer inflatable cushion 18 is provided
with a crown portion 18A and wing portions 18B, 18C that are radially
spaced with respect to the inner inflatable cushion 16. The cushions are
curved and contoured so that they do not engage sensitive structures of
the head and neck, such as the eye and the tip of the nose.
The crown and wing portions of the inner and outer inflatable cushions 16,
18 are curved and contoured for a close conforming fit along different
sets of facial surface areas, respectively. According to this radially
spaced relationship, each cushion is arranged so that it can, by itself,
fully support the patient's head and face, but with different facial and
forehead portions of the patient being supported by the each inflatable
cushion.
According to an important feature of the invention, the cushions 16, 18 are
independently inflatable and deflatable with respect to each other, so
that the resting pressure forces imposed on sensitive facial and forehead
regions of the patient are intermittently relieved by alternately
pressurizing and depressurizing the contoured support cushions 16, 18. In
the preferred embodiment, the inflatable cushions 16, 18 are sequentially
pressurized and depressurized, thus providing continuous, soft support for
the patient's forehead and face, while alternately relieving compression
forces applied to pressure-sensitive facial areas.
Alternately pressurizing and depressurizing the inflatable cushions 16, 18
shifts the location of the compressive forces, thus relieving pressure on
compressed tissues and permitting recovery of normal circulation in
sensitive tissues. The time interval duration of pressurization and
depressurization is also mutually adjustable for each cushion during a
programmable sequence, as described below. This shifting, variable
pressure and intermittent pressurization arrangement does not disturb the
resting position or elevation of the patient and/or the patient's head
during surgery.
Referring now to FIG. 2 and FIG. 5, the inflatable cushions 16, 18 are
provided with connector fittings 26, 28 which are received within air
passages 30, 32 for attachment to supply conduits 34, 36, respectively.
The air passages 30, 32 are terminated by quick connect couplings 38, 40,
respectively, which are connectable to the supply conduits 34, 36 as shown
in FIG. 6.
Referring now to FIG. 2 and FIG. 6, the supply conduits 34, 36 are coupled
to a source of compressed air, such as a pneumatic compressor 42, by a tee
coupling 44 and a common supply conduit 46. Preferably, the compressor 42
is a low cost, low noise and reliable air compressor having a rated output
of approximately 0.5 scfm with a maximum pressure of 30 psi, for example
Model No. 007CDC19, manufactured by Thomas Corporation and distributed by
Tool Systems, Inc. Pressurized (compressed) air produced by the compressor
42 is selectively applied to the inflatable cushions 16, 18 through flow
control valves V1, V2, V3, V4 and V5. According to an alternative
embodiment, the pressurized (compressed) air is supplied from one or more
portable compressed air canisters through a pressure regulator to provide
approximately 0.5 scfm at a maximum pressure of 30 psi.
The flow control valves V1, V2, V3, V4 and V5 are two-position, three-port
flow valves, commonly referred to as two-way or three-way valves,
depending on the number of active outlet ports available. The power-off,
unswitched position of each valve is selected to be "normally open" or
"normally closed" depending on the switching logic used by the controller.
Suitable flow control valves can be obtained from Clippard Minimatic of
Cincinnati, Ohio, distributed by Cross Sales & Engineering Co. of
Norcross, Georgia. The preferred model numbers are ET-2-12-L (two-way
valves) and ETO-3-12-L and ET-3-12-L (three-way valves). As used herein,
the terms "unswitched" and "switched" as used in connection with the flow
control valves V1, V2, V3, V4 and V5 refer to the power-off valve position
(unswitched) indicated by the solid arrow, and the power-on
solenoid-actuated valve position (switched) indicated by the dashed arrow.
Each flow control valve has a single inlet port with switched and
unswitched outlet ports. Thus, the two-way flow control valve V1 has an
inlet port 48, an unswitched outlet port 50 and a switched outlet port 52
(blocked). Likewise, the three-way flow control valve V2 has an inlet port
54, an unswitched outlet port 56 and a switched port 58. The two-way flow
control valve V3 has an inlet port 60, an unswitched outlet port 62
(blocked) and a switched outlet port 64. The flow control valve V4 has an
inlet port 66, an unswitched outlet port 68 and a switched outlet port 70.
The flow control valve V5 has an inlet port 72, an unswitched outlet port
74 and a switched outlet port 76.
The flow control valves V1, V2, V3, V4 and V5 are mechanically and
electrically coupled for independent shifting actuation by separate
solenoids 78, 80, 82, 84 and 86. Pressurization and depressurization of
the cushions 16, 18 are thus performed independently of each other.
In the preferred embodiment as represented by FIG. 6, the flow control
valves V1, V2, V3, V4 and V5 are coupled between the compressor 42 and the
inflatable cushions 16, 18 for selectively pressurizing the inflatable
cushions independently with respect to each other, and for selectively
releasing pressurized air from the inflatable cushions 16, 18
independently of each other. This is made possible by connecting the
unswitched outlet ports 50, 56 of the flow control valves V1, V2 in air
flow communication with each other, with the switched outlet port 52 of
the flow control valve V1 being closed, and the switched outlet port 58 of
the flow control valve V2 being open to atmosphere.
The flow control valves V3, V4 control the application of pressurized air
to the inflatable cushion 16, and are similarly connected. According to
this valving arrangement, when the flow control valves V1, V2 and V5 are
in the unswitched positions as shown in FIG. 6, an air flow passage is
established between the main supply conduit 46 of the compressor and the
supply conduit 36 which supplies pressurized (compressed) air to the
inflatable cushion 18. When the flow control valves V1, V2 are actuated to
the switched position, pressurized air is permitted to vent through the
supply conduit 36 and through the inlet port 54 of the flow control valve
V2 through the outlet port 58 which is open to the atmosphere. In the
switched position, the flow control valve V1 is shifted to the closed
outlet port 52, thereby interrupting the flow of compressed air from the
compressor 42 to the outer cushion 18.
During the outer cushion pressurization interval, air in the inner
inflatable cushion 16 is vented through the supply conduit 34, through the
inlet port 66 of flow control valve V4 and into the atmosphere through the
unswitched outlet port 68, which is open to the atmosphere. Compressed air
from the compressor 42 that is delivered to the flow control valve V3
through supply conduit 34 is blocked by the closed outlet port 62 of valve
V3. When the flow control valves are switched, compressed air in the outer
inflatable cushion 18 is permitted to vent into the atmosphere through the
open outlet port 58 of flow control valve V2, while the inner inflatable
cushion 16 is pressurized through the switched outlet port 64 of flow
control valve V3, the switched outlet port 70 and inlet port 66 of flow
control valve V4.
Referring now to FIG. 2, FIG. 6 and FIG. 7, the inflatable cushions 16, 18
are pressurized and depressurized automatically by a controller 88. The
controller 88 includes as its principal components a microprocessor 90
that performs sequencing operations according to instructions stored in an
electrically programmable read-only memory (EPROM). Sequencing operations
are coordinated by three interval timers T1, T2 and T3, four voltage
comparators 92, 94, 96 and 98, an over-pressure logic circuit 100 and five
solenoid output drivers 102, 104, 106, 108 and 110.
The microprocessor 90 receives input logic signals 126, 128, 130 and 132
that indicate the under-pressure/over-pressure threshold conditions of the
pressure sensors 112, 114 that are connected in flow communication in the
supply conduits 34, 36, respectively. The microprocessor also receives
timing logic signals 116, 118 and 120 that are output by the timers T1, T2
and T3. The pressure sensors 112, 114 are analog transducers, for example
model number PX139-030D4V, distributed by Omega Engineering, Inc.
The non-inverting (+) inputs of the logic comparators 92, 94, 96 and 98 are
connected to the analog voltage outputs 122, 124 of the pressure sensors
112 and 114. The switching thresholds of the voltage comparators 92, 94,
96 and 98 are adjusted by variable resistors R1, R2, R3 and R4 which are
coupled to a supply voltage V.sub.CC. The resistors R1, R2, R3 and R4 form
voltage divider circuits that provide reference voltages on the inverting
(-) inputs of the voltage comparators. Each reference voltage is set to
correspond with a desired threshold operating pressure and maximum
operating pressure within the inflatable cushions 16, 18, for example 15
psi and 30 psi, respectively.
The comparator logic output signals 126, 128 are at logic low when the
inflatable cushions are under-inflated (below 15 psi) and the logic
outputs are at logic high when the inflation pressure of the cushions
equals or exceeds the preset minimum leve | | |
