Gas-liquid microvolume separating apparatus and method

A gas-liquid separator apparatus and device, particularly for use in connection with medical gas analyses, such as capnography, is provided. The separation chamber tapers in a direction from the blow down port to the dry gas outlet port providing increased surface area in the lower portion of the separation chamber for providing capillary volumes or regions. A solid body is disposed in the separation chamber to provide a surface of the capillary volumes and to decrease the effective volume of the separation chamber. The body can be used to occlude the dry gas outlet port upon tipping of the separation chamber at greater than a predetermined angle. A number of internal fins extend inwardly from the side wall and bottom surface into the separation chamber to form capillary volumes in cooperation with the side wall, bottom surface and/or solid body.

FIELD OF THE INVENTION 
The present invention relates to apparatus and method for separating liquid 
from a mixture of liquid and gas and, in particular, to a separating 
apparatus and method with a microvolume usable in connection with gas 
analyzers such as blood gas analyzers. 
BACKGROUND OF THE INVENTION 
In a number of medical procedures, it is desired to obtain an indication of 
the concentration of carbon dioxide in the exhaled breath of a patient. 
This determination, generally known as capnography, is typically conducted 
using an infrared analysis device. Such devices typically require that the 
gas being monitored be substantially dry, i,e., free from condensed water 
or other liquid constituents. Because exhaled gases typically exit a 
patient at about 100% relative humidity, as the gas cools during travel 
through the sampling line and equipment, moisture condenses. It is 
important to remove this moisture from the gas sample which is typically 
continuously drawn from the exhaled gases, usually at a flow rate of about 
200 ml per minute or less. 
Because, in capnography, it is desired to obtain continuous and 
instantaneous indications of the constitution of the exhaled gases, it is 
also important to avoid substantial mixing of gases sampled at different 
times. Accordingly, to avoid dampening the capnographic signal, the 
internal volume of the sampling line, including the volume of any 
gas/liquid separators, is preferably kept as small as possible. For this 
reason, it is generally desirable that a gas/liquid separating apparatus 
employ a separating chamber having a microvolume, i.e., a volume less than 
about 1 ml, and preferably much smaller. 
Several approaches to solving these problems have been tried. U.S. Pat. No. 
4,304,578 issued Dec. 8, 1981 to Hakala, et al. discloses a water 
separator which includes a downward tapering conical separation chamber. 
U.S. Pat. No. 4,382,806 issued May 10, 1983 to Hakala, et al. discloses a 
separation chamber with straight sides for precipitation of condensed 
water and a downward tapering portion at the lower end. U.S. Pat. Nos. 
4,579,568 issued Apr. 1, 1986 to Ricciardelli, et al. and 4,592,368 issued 
June 3, 1986 to Ricciardelli, et al. disclose a separation chamber with a 
barrier which prevents direct flow to a second chamber that diverges 
upwardly. U.S. Pat. No. 4,717,403 issued Jan. 5, 1988 to Choksi discloses 
an apparatus which uses centrifugal separation of the gas and condensed 
moisture. 
Of the above-described approaches, none describes making use of capillary 
forces or methods for No. 4,703,095 issued Dec. 15, 1987 to Ricciardelli 
discloses a separator with downwardly tapering pyramid-shaped lower walls 
forming internal corners with angles that produce capillary action for use 
in separation of a liquid from a gas. The capillary internal corners 
converge towards the liquid port to channel liquid away from the gas 
outlet port. Because of the downward tapering configuration of the 
separation chamber, a smaller interior wall surface area is available for 
formation of capillary volumes toward the bottom of the separation 
chamber. The total capillary volume in the lower area of the separation 
chamber thus is less than that in the upper region of the separation 
chamber. Accordingly, it would be useful to provide a separation 
configuration in which more surface area is available for capillary action 
in the lower portions of the separation chamber, without sacrificing 
effectiveness or efficiency of the capillary action. 
Previously available separators of this type also have been subject to 
other disadvantages. Typical separators withdraw some amount of gas along 
with the separated liquid which is, therefore, not transmitted to the gas 
analysis device. This so-called blow down gas is preferably minimized 
because blow down gas is not available to the gas analyzer. Although 
previous devices are disclosed as requiring as little as 2 to 5% blow down 
for water separation, in practice it has been found that separation of 
liquids with viscosity higher than water (such as typically occurs when 
bodily fluids are mixed in the exhaled gases) require an increase in blow 
down ratio, occasionally greater than 15 to 20%. Accordingly, it would be 
useful to provide an apparatus with sufficient separation efficiency that 
the blow down ratio can be maintained less than about 15% even when the 
viscosity of the liquid is greater than that of water. 
As noted above, it is desirable, in order to avoid damping or otherwise 
distorting the capnographic signal, that the separation chamber be kept at 
a small volume. Accordingly, it is desirable to provide a separation 
chamber with means for reducing the volume occupied by gas by substantial 
amounts such as 0.04 ml or more, to provide a dead space having a volume 
of about 0.1 ml or less. 
Previous devices typically rely exclusively on gravitational means for 
separation or for channelling separated liquid away from the dry gas 
outlet port. Accordingly, previous devices are unusable when tilted 
substantially out of the preferred operating orientation or in reduced or 
zero gravity conditions. Accordingly, it would be useful to provide a 
device which will operate when tilted in positions up to 90.degree. from 
the vertical or in a reduced or zero gravity environment. 
Relatedly, previous devices, if tipped out of the preferred orientation, 
will permit liquid to exit from the dry gas outlet port causing fouling of 
the gas analyzer and consequent expensive cleaning or repairs. 
Accordingly, it would be useful to provide an apparatus in which tilting 
at greater than a predetermined angle results in prevention of the passage 
of liquid through the dry gas outlet port. 
Because of the time and expense involved in sterilizing medical equipment, 
it would be also be advantageous to provide a device in which the regions 
which might become contaminated with the separated liquid are detachable 
from the remainder of the apparatus and are constructed using sufficiently 
inexpensive procedures and materials that such portions can be disposed of 
rather than cleaned and reused.

SUMMARY OF THE INVENTION 
The separation chamber provided in the present invention is defined by 
interior surfaces which taper upwardly so that the cross-sectional area in 
the lower portion of the separation chamber exceeds the cross-sectional 
area of the upper portion. 
Accordingly, the interior surface area of the separation chamber is greater 
in the lower portion, affording larger surface areas for provision of 
capillary channels or volumes. The more effective capillary action 
provided by the present invention contributes to more efficient 
separation, even for higher viscosity fluids, and thus a lower blow down 
ratio requirement. Furthermore, the higher efficiency of capillary action 
permits utilization of the separation chamber even when tilted from the 
vertical such as up to 90.degree. or in reduced or zero gravity 
environments. A solid movable body such as a ball bearing is disposed in 
the separation chamber. The ball bearing in the lower position acts to 
form a surface of the capillary volumes, further increasing capillary 
action efficiency. The movable body also occupies space and thereby 
reduces the effective volume of the separation chamber. When the 
separation chamber is tipped at greater than a predetermined angle, the 
ball bearing occludes the outlet port preventing passage of liquid and 
consequent fouling of the analyzer. Preferably, a device such as a magnet 
is used to position and maintain the ball bearing in the occluded position 
upon tipping beyond a predetermined angle. 
An outlet port from the separation chamber conveys the separated liquid and 
the blow down gas to a reservoir. The reservoir may include an absorbing 
material to assist in preventing moisture from being drawn into the blow 
down port when the device is tilted. Additionally, the absorbing material 
can be selected to have large expansion when wetted to provide an 
indication when the reservoir is filled. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a separator 10 according to the present invention 
includes a manifold portion 12 in fluid communication with a reservoir 14. 
As best seen in FIG. 2, the manifold 12 contains a separation chamber 16 
and a low-pressure passageway 18. The low-pressure passageway 18 
communicates with the reservoir 14 by a first tube 19. The separation 
chamber 16 has three ports. An inlet port 22, best seen in FIG. 3, is used 
for transmitting a sample of the patient s exhalation gases obtained by 
means of a sampling device 24 of any of the types well known in the art, 
connected to the exhalation gas passageway 26 from the patient. A first 
outlet port 28 is provided in the first, normally upper end surface 30 of 
the separation chamber 16 for removal of substantially dry gas. A second 
outlet port 32 is provided in the second, normally lower end surface 34 of 
the separation chamber for conveyance of a mixture of substantially all 
liquid and a blow down portion of gas into the reservoir 14 by way of a 
second tube 35 extending partially into the reservoir 14. The first end 
surface 30 and the second end surface 34 are connected by a sidewall 38. 
The sidewall 38 defines the cross-sectional area at any point along the 
longitudinal extent of the separation chamber 16, which varies in such a 
way that the cross-sectional area in the region adjacent to the first end 
surface 42 is less than the cross-sectional area in the region adjacent to 
the second end surface 44. Preferably, the sidewall 38 defines a 
substantially conical surface, i.e., lies substantially along an imaginary 
cone 46, as best seen in FIG. 8. Extending inward from the sidewall 38 
into the interior of the separation chamber 16 are one or more upper fins 
48. Preferably, the apices, or inward-most extent of the upper fins 48, 
define a cylinder, i.e., lie substantially along an imaginary cylindrical 
surface 52. In the embodiment depicted in FIGS. 1-8, there are three fins 
48a, 48b, and 48c, of substantially triangular cross-sectional shape. 
The upper fins 48 act to position and guide movement of an interior body, 
as described more fully below, and can also form a surface of a capillary 
region or volume in cooperation with the sidewall 38, as described more 
fully below. Because whether a region or volume will have a capillary 
action on a fluid depends on the characteristics of the fluid, principally 
the surface tension thereof, the geometry and dimensions of a capillary 
volume must be defined in relationship to the fluid. In the present case, 
a contemplated use of the invention is separation of liquid from exhaled 
gases. In many instances, the liquid will be substantially water, and thus 
the present invention includes volumes which are capillary volumes with 
respect to water. As noted above, however, in many medical applications, 
the liquid will include an amount of typically viscous body fluids, so 
that preferably the capillary volumes will be capillary with respect to 
fluids which are more viscous than water. 
Preferably, the upper fins 48 extend only partly along the longitudinal 
extent of the sidewall 38 and are sufficiently spaced from the first 
outlet port 28 to prevent any capillary conveyance of liquid to the 
vicinity of the outlet port 28, such as might result in movement of liquid 
through the first outlet port 28. 
The first end surface 30 is substantially shaped as a segment of a sphere, 
such as a hemisphere, with a planar portion 54 to assist in occlusion of 
the first outlet port 28, as described more fully below. The first outlet 
port 28 is preferably centrally located in the planar portion 54. 
The second outlet port 32 is adjacent to, and preferably formed in, the 
second end surface 34. The second end surface 34 is preferably shaped as a 
segment of a sphere, such as a hemisphere. A plurality of lower fins 56 
project inward from the second end surface 34 into the interior of the 
separation chamber 16, as best seen in FIG. 7. The lower fins 56 act to 
position a solid body in the separation chamber 16 and to define capillary 
regions or volumes, as described more fully below. As best seen in FIG. 6, 
the lower fins 56 are substantially trapezoidal in cross section so that 
the innermost extensions or surfaces 58 of the lower fins 56 are 
substantially flat. 
In the embodiment depicted in FIGS. 1-8, six lower fins, 56a-56f, are 
provided, preferably radially disposed about the second outlet port 32. 
Preferably, the flat surfaces 58 define a spherical surface, i.e., lie 
along a sector of an imaginary sphere, substantially parallel to the 
second end surface 34. 
The fins 56, in cooperation with the second end surface 34, form walls of 
capillary regions or volumes. The capillary volumes include the 
interstices 62a-62f between the lower fins 56. It has been found that a 
converging configuration of capillary volumes 62, such as that depicted in 
FIGS. 1-8, is effective to convey liquid towards the second outlet port 32 
with sufficient efficiency that even when the liquid has a viscosity 
higher than water, the amount of gas flow or blow down needed to convey 
the liquid away from the first outlet port 28 and into the reservoir 14 is 
less than in previous configurations. Without wishing to be bound by any 
theory, it is believed that the efficiency is related to providing both 
capillary volumes 62, which taper towards the second outlet port 32, and a 
relatively large surface area in the second end surface 31 for 
accommodating more capillary volumes 62. The tapering of the sidewall 38 
is consistent with both the desirably of a large surface area for the 
second end surface 34, and the desirability of a small total volume for 
the separation chamber 16. 
Another advantage of increased capillary effect of the present 
configuration is that the device is less dependent on gravitational action 
than previous devices. Accordingly, the present invention is operable when 
tipped, such as at angles up to about 90.degree., so that gravity is not 
acting in a direction toward the second outlet port, and is also operable 
in low or zero gravity environments. 
As noted, for example, in U.S. Pat. No. 4,713,095, the angle of corners 
affects the degree of capillary action of a capillary volume. Accordingly, 
in the preferred embodiment, the angle 64 which the lower fins 56 make 
with the second end surface 34 is preferably less than or equal to about 
135.degree.. This angular relationship is preferably also used in the 
upper fins 48. 
Although the lower fins 56, acting only in cooperation with the second end 
surface 34, can be configured to provide capillary volumes 62 with the 
desired efficiency, in the preferred embodiment a solid body, such as a 
ball bearing 66 is disposed in the separation chamber 16 to also define 
surfaces of capillary volumes. The ball bearing 66 is positionable to 
substantially contact the flat surfaces 58 of the lower fins 56 and, in 
this position, to form an additional surface to define the capillary 
volumes 62. Thus, in the preferred embodiment, the capillary volumes 
62a-62f are defined by the fins 56a-56f, the second end surface 34, and 
portions of the surface of the ball bearing 66. The presence of the ball 
bearing has been found to increase the efficiency of the capillary action, 
and thus permit a lowering of the blow down ratio (i.e., the percentage or 
portion of the gas which is introduced into the separation chamber that is 
drawn through the second outlet port 32), which is necessary to remove 
liquid from the separation chamber 16 so as to prevent its passage through 
the first outlet port 28. In one embodiment of the invention, the solid 
body is fixed, such as by gluing, in a position away from the first outlet 
port 28 and proximate to, but spaced from, the second outlet port, such as 
the position 66 depicted in FIG. 3, to be in a non-sealing relationship 
with the second outlet port 32. 
The ball bearing 66 is also operable to provide other functions. Because 
the ball bearing occupies a certain amount of space in the separation 
chamber 16, the effective volume (i.e., the dead space or volume available 
for the gas) is reduced, thus reducing or preventing degradation of the 
gas analysis signal because of excessive gas mixing in the separation 
chamber 16. 
Further, the ball bearing 16 can act to occlude the first outlet port 28 
when such is desired. For example, it may be desired to occlude the first 
outlet port 28 whenever the separation chamber 16 is tipped out of its 
preferred vertical alignment, depicted in FIG. 3, beyond a predetermined 
maximum tipping angle, such as tipping to such a degree that liquid in the 
separation chamber 16 or reservoir 14 will flow through the first outlet 
port 28. Preferably, the upper fins 48 are configured to guide the ball 
bearing 66 from the lower position depicted in FIG. 3 to an upper position 
68, shown in phantom lines. It is for this reason that the upper fins 48 
define a substantially cylindrical surface 52 for passage of the 
substantially spherical ball bearing 66. It has been found that the 
desired seating of the ball bearing 66 to occlude the first outlet port 28 
is facilitated by provision of the planar region 54 around the first 
outlet port 28. 
The maximum tipping angle, beyond which it is desired to occlude the first 
outlet port 28, will depend on the configuration of the separation chamber 
16 and the outlet ports 28, 32. In part because of the upward tapering 
configuration of the sidewall 38, a larger tipping angle can be tolerated 
in the present invention than could be tolerated by previous downward 
tapering configurations. In general terms, the maximum tipping angle will 
be that angle at which either a portion of the sidewall 38 is angled 
sufficiently downward with respect to gravity to permit liquid to flow 
into the first outlet port 28, or at which liquid in the reservoir 14 can 
freely flow into the separation chamber 16 under the influence of gravity. 
Accordingly, the maximum tipping angle is affected by the geometry of the 
separation chamber 16 and reservoir 14. The downward tapering of the 
separation chamber permits toleration of a larger tipping angle than could 
be permitted with an untapered or oppositely tapered chamber. Further, the 
extension of the first and second tubes, 19, 35 into the reservoir 14 
permits some degree of tipping (and thus, pooling of liquid near the top 
of the reservoir 14) before liquid can pass back into the separation 
chamber 16. 
The angle at which the ball bearing 66 moves to the second or upper 
position 68 can be adjusted or affected by the configuration of the 
sidewall 38 or upper fins 48 so that movement is controlled only by 
gravitational forces. Preferably, however, a device is provided to 
position and maintain the ball bearing 66 in the upper position 68 upon 
tipping beyond a predetermined angle. In the embodiment depicted in FIG. 
3, the device for positioning and maintaining the ball bearing 66 in the 
upper position 68 is an array of four magnets 72A-D. A number of 
advantages are obtained by using a positioning device such as a magnet 72. 
The strength of the magnets 72A-D can be adjusted so that they are 
effective to position the ball bearing 66 in the upper position 68 as soon 
as the ball bearing 66 has moved to within a predetermined distance of the 
magnets 72A-D, such as from tipping of the separation chamber 16. In this 
manner, it is possible to adjust the tipping angle at which the ball 
bearing 66 is moved to the upper, occluding position 68. By using an 
electromagnet, rather than a permanent magnet, the strength of the 
magnetic field can be calibrated to adjust the maximum permissible tipping 
angle, or the electromagnet can be activated by an angle-sensing device 
(not shown). Further, because the relatively more expensive magnet 72 is a 
part of the housing 74, rather than part of the separator 10, the overall 
cost of the separator 10 is maintainable at a level which permits the 
separator 10 to be used in a disposable fashion. Preferably, the magnets 
72A-D are positioned slightly above the center of the ball bearing 66 when 
the ball bearing is in the upper position 68. 
The housing 74 preferably contains apparatus, such as resilient sleeve 75, 
for holding the separator 10 in position so as to permit easy 
detachability and replacement of the separator 10 consistent with its 
preferred use as a disposable member. The housing 74 also contains a 
passageway 78 for conveying gas from the first outlet port 28 to the gas 
analyzer 82, which can be any gas analyzer, such as an infrared capnogram 
or others well known in the art. 
FIG. 7 depicts a preferred manner of assembly of the device. As shown, the 
device is preferably formed from three sections, an upper manifold section 
84, a lower manifold section 86, and a reservoir section 88. Although the 
preferred material of construction is a clear polycarbonate material, 
other materials, such as metal, resins, plastics, and the like, can be 
used. The parts are preferably formed by molding, such as injection 
molding, but can be formed by other processes, such as stamping, milling, 
and the like. The parts 84, 86, 88 are preferably joined by a bonding 
technique, such as ultrasonic welding, although they can also be joined by 
adhesion, screwing, bolting, and other well known methods. 
The exact dimensions and shapes of the apparatus will depend on the 
intended use. In one preferred embodiment, the interior volume of the 
separation chamber 16 is approximately 0.1 ml. The ball is 0.172 inches 
(about 4.4 mm) in diameter, and the imaginary cylinder defined by the 
upper fins has a diameter of about 0.18 inches (about 4.6 mm). The lower 
fins 56 define a spherical sector with a 0.184 inch diameter, whose center 
is 0.006 inches (about 0.15 mm) above the plane of the parting line. The 
second end surface 34 lies along a sphere of 0.224 inches in diameter 
(about 5.7 mm) whose center is coincident with the center of the sphere 
defined by the lower fins 56. The inlet port 22, first outlet port 28, and 
second outlet port 32 have diameters of approximately 0.03 inches (about 
0.75 mm). The reservoir 14 has a capacity of about 0.3 cubic inches (about 
5 ml). The upper end surface 30 lies partially along a spherical sector 
with a radius of 0.09 inches (about 2.3 mm). 
The manner of operation of the present invention will now be described. 
Operation of a gas analysis system of a type usable in connection with the 
present invention is described in U.S. Pat. No. 4,592,368, albeit with 
another type of gas/liquid separator. In general, gas, such as exhaled gas 
from a patient, is conveyed through a passageway 26 and is sampled by a 
sampling device 24. A slight negative pressure is provided in the 
separation chamber 16 by virtue of negative pressures established at the 
low-pressure passageway 18 and the first outlet port 28, in a manner well 
known in capnography gas-liquid separators. Because of the lower pressure 
in the separation chamber 16, gas from the sampling device 24 enters the 
separation chamber 16 through the inlet port 22. The fluid entering inlet 
port 22 is a mixture of gas and liquid, the liquid typically being liquid 
which has condensed from the gas as it has cooled. The liquid impacts the 
interior surfaces of the separation chamber 16 and the ball bearing 66, 
and accumulates or coalesces in the capillary volumes 62. The coalescence 
in the capillary volumes 62 can be accomplished or enhanced by ordinary 
gravity drainage of droplets down the sidewall 38 and/or capillary 
conveyance along capillary volumes formed between the upper fins 48 and 
the sidewall 38. The liquid is directed, by capillary action and/or 
gravitational action, away from the first outlet port 28 and towards the 
second outlet port 32. Because of the relatively lower pressure in the 
reservoir 14, by virtue of the partial vacuum created through the low 
pressure passageway 18, substantially all liquid and the blow down portion 
of the gas are conveyed through the second outlet port 32 to the reservoir 
14. The reservoir 14 is preferably provided with an absorbent material 92 
to assist in preventing flow of liquid from the reservoir 14 into the 
separation chamber 16, such as upon tipping of the reservoir 14. 
Preferably, the absorbent material 92 expands upon wetting, and can be 
used to provide a visual indication of the amount of liquid in the 
reservoir 14, such as by providing a view port or window in the reservoir 
14 or by forming reservoir 14 of a substantially transparent material. 
Use of the separator 10 is continued until the reservoir 14 is 
substantially filled with liquid, for example, as indicated by expansion 
of material 92 in the reservoir 14. At this point, the separator 10 can be 
removed from the housing 74 and replaced by a new separator 10. Because 
substantially all patient-wetted surfaces are contained in the separator 
10 or are upstream thereof, replacement of a separator 10 with a sterile 
separator prevents contamination of a new patient. Preferably, a removed 
separator 10 is disposed of, whereas the housing 74 is reusable. 
When the separation chamber 16 is tipped beyond a predetermined angle, as 
described above, the ball bearing 66 is brought within the influence of a 
magnet 72, and the magnet positions the ball bearing 66 adjacent to and 
seating with respect to the first outlet port 28 to prevent the passage of 
liquid through the first outlet port 28. 
As can be seen from the above description, a number of advantages are 
provided by the present invention. Capillary action in the present 
configuration is sufficiently effective to permit reduction of the blow 
down ratio, such as reduction below 15% even when fluids more viscous than 
water are separated. Upward tapering sidewalls provide for increased 
surfaces for capillary volumes in lower portions and increase in the 
permissible tipping angle without excessive increase in the volume of the 
separation chamber 16. A solid body, such as a ball bearing, provides for 
an additional surface for definition of capillary volumes, provides for a 
decrease in the effective volume of the separation chamber, and is usable 
for selective occlusion of the first outlet port, for example, upon 
tipping beyond a predetermined angle. The apparatus is inexpensively made, 
consistent with disposable use. The separator 10 is detachable in such a 
way that patient-wetted surfaces are removable from the housing to assist 
in preventing contamination from one patient to another. 
Increased efficiency of capillary action contributes to greater liquid 
separation ability, and thus lowers the chance of passage of liquid 
through the first outlet port. Because movement of liquid to the second 
outlet port is effected, at least in part, by capillary action, the 
separator 10 is capable of operation in positions of up to 90.degree. from 
the vertical, or in reduced or zero gravity conditions. The device will 
automatically shut off flow to the second outlet port if predetermined 
conditions of acceptable orientation are exceeded, thus preventing liquid 
from fouling the measuring device. 
A number of variations and modifications of the invention can be practiced, 
including those described below. The sidewall of the separation chamber 
can be formed in a tapering configuration other than a conical 
configuration. The solid body, which is movable in the separation chamber, 
can be a body other than a ball bearing and other than a spherical body, 
although it is preferably gas-impermeable. The upper fins can define an 
imaginary surface other than a cylindrical surface, particularly in 
cooperation with a non-spherical movable body. Fins with non-triangular or 
non-trapezoidal cross sections are usable, although flat surfaces of 
contact with the movable body, particularly with respect to the lower 
fins, assist in preventing damage from impact between the movable body and 
the fins. The upper and lower end surfaces can have other than spherical 
sector configurations, consistent with channeling of flow to the outlet 
ports. Devices for positioning and maintaining the ball bearing in the 
upper position, other than a magnet, can be used, such as springs, 
electric devices, hydraulic or fluid devices, and the like. A gas 
analyzer, other than an infrared capnographic analyzer, can be used and 
the separator 10 can be used in non-gas analyzer contexts, such as any 
context in which it is desired to separate a liquid from a gas. Although 
the preferred use of the separator is as a disposable unit, the separator 
can be provided in a reusable and/or sterilizable configuration. 
Although the invention has been described in terms of its preferred 
embodiment, modifications and variations are also included in the present 
invention, the scope of which is defined by the following claims.