Packaging for a sterilizable calibratable medical device

The present invention provides a package for and method of packaging a sterilizable calibratable medical device including a hydratable sensor component. The device is maintained in a sterile environment during storage and in a clean environment during the calibration procedure. The package includes a manifold connected to the sensor component by plumbing. The plumbing establishes fluid communication between the manifold and the sensor component and/or between the sensor component and the ambient environment of the plumbing. The manifold, plumbing and medical device are sealed in a wrap including a gas-permeable surface. The wrap and its contents, including the interior surfaces of the components, are sterilizable by exposing the wrap to a gaseous sterilization solution and appropriately adjusting the plumbing. The medical device is hydratable by directing the hydration solution to the sensor component by means of the plumbing. In order to store the package over an extended period of time, a gas-impermeable chamber is defined which includes the ambient environment of the plumbing. The gaseous environment of the medical device is thereby controllable. In this manner, the device is prepared for calibration and is storable in the sterile environment. By connecting a reservoir including calibration solution to the plumbing, the calibration solution is directed to the sensor component without removing the medical device from its clean enviroment. The temperatures of the sensor component and the solution are controlled throughout the calibration process in order to ensure that the device is calibrated in accordance with its intended use. The present invention further discloses a solution for preparing the medical device for use. The solution is chemically compatible with the intended use of the device.

TECHNICAL FIELD 
This invention relates to packages for and methods of packaging 
sterilizable calibratable medical devices and, more particularly, provides 
a packaging system for in situ sterilization and calibration of medical 
devices consisting of hydratable sensor components. 
BACKGROUND OF THE INVENTION 
Packages for and methods of packaging medical devices are numerous. The 
choice of method for packaging a device depends in part on the intended 
use of the device. Factors include whether the device is used in a sterile 
environment, whether the device is used in contact with or inserted into a 
living animal, whether the device is disposable, etc. Certain devices must 
be sterilized prior to use. One known method for packaging a sterile 
device is to first insert the device into a gas-impermeable wrap. The 
interior of the wrap, including the device, is then sterilized. The wrap 
is then sealed so that the device remains sterilized until the package is 
opened just prior to use. Once the package is opened, a minimum amount of 
handling is desirable to avoid the possibility of contaminating the 
device. 
Certain medical devices additionally require calibration prior to use. 
Medical devices that monitor analyte levels, temperature, etc., often 
include chemical or electrical sensing components that are very sensitive 
to temperature, moisture, etc. These devices are generally used in 
conjunction with monitoring instrumentation that controls and records the 
monitoring process. For example, a medical device may be connected to a 
computerized controller which initiates and transmits an electrical or 
optical signal to the device, receives a resultant signal from the device, 
and analyzes the resultant signal to produce a value indicative of the 
measured characteristic. 
One common way of calibrating a medical device used for monitoring analyte 
concentrations is to immerse the sensing component of the device into a 
calibration solution containing a known amount of the targeted analyte. 
Base measurement levels are recorded in accordance with the known amount 
of the analyte. Such calibration solutions must be highly uniform to 
provide consistent and useful results in the calibration process. The 
solutions are typically unstable and are only prepared as needed or 
prepackaged in glass ampules. Glass ampules require especially careful 
handling during the calibration process to avoid breakage. Shelflife 
problems, e.g., change of chemistry, separation, etc., may be encountered 
with prepackaged solutions that are stored over a period of time prior to 
use. Conventional calibration procedures are time-consuming, costly, 
subject the device to possible contamination, and often require the 
presence of a trained technician to oversee the process. Additionally, if 
a calibratable device is to be stored over a period of time, the device is 
most easily stored in a dry state to avoid problems arising from the 
storage of a moist device. Bringing the sensing component of the device 
from a dry to a functional state often requires hydrating the sensing 
component over an extended period of time. 
When a device must be sterilized as well as calibrated, additional problems 
arise due to the fact that the sterilization and calibration procedures 
are often incompatible. For example, one common method of sterilizing a 
medical device is to expose the device to ethylene oxide (ETO). The ETO 
procedure is carried out in a non-liquid, i.e., dry, environment. This dry 
state renders the sensing component of the device completely nonfunctional 
if the component is meant to operate in a moist environment. In contrast, 
as discussed above, the common method of calibrating such a device is to 
immerse the device in a calibration solution. Thus, an ETO sterilization 
procedure and a moist calibration procedure must be distinct phases in the 
preparation of the device. 
In recent years, optical fiber sensors, also known as optrodes, have been 
developed to detect the presence of and to continuously monitor the 
concentration of various analytes, including oxygen, carbon dioxide, 
glucose, inorganic ions, and hydrogen ions, in solutions. An example of 
such a sensor is a blood gas sensor for monitoring pH, PCO.sub.2 or 
PO.sub.2. Such a blood gas sensor is based on the recognized phenomenon 
that the absorbance or luminescence of certain indicator molecules is 
specifically perturbed in the presence of certain analytes. The 
perturbation in the absorbance and/or luminescence profile is detected by 
monitoring radiation that is reflected or emitted by the indicator 
molecule when it is in the presence of a specific analyte. The targeted 
analyte is generally a part of a solution containing a variety of 
analytes. 
Optrodes have been developed that position an analyte-sensitive indicator 
molecule in the light path at the end of one or more optical fibers. This 
fiber unit is often termed the sensor component. The sensor component is 
an integral part of a blood gas catheter. The indicator molecule is 
typically housed in a sealed chamber at the end of the fiber(s). The 
chamber is secured to the optical fiber by a suitable cement material. The 
walls of the chamber are permeable to the analyte. The sensor component is 
inserted into and left in a patient for an extended period of time. 
Analyte readings in the form of optical signals are transmitted from the 
sensor component to monitoring instrumentation which analyzes the signals 
and controls the monitoring process. 
The sensor component in a blood gas catheter thus typically includes a 
membrane material, an analyte sensing material, an optical fiber, and a 
cement. Each element is chosen to be compatible with the other elements 
and with the monitoring process. In order to monitor a specific analyte, 
the sensor component is sterilized and then brought to a functional state 
in which the catheter sensor is responsive to the targeted analyte. 
Additionally, the monitoring instrumentation is calibrated in conjunction 
with the specific catheter prior to use. If the catheter is subject to the 
above-described ETO sterilization and packaging process, the analyte 
sensing material of the sensor is completely dried and is not in proper 
chemical balance to carry out the monitoring process. Thus, the sensor 
must be hydrated and calibrated prior to use. If the traditional 
calibration method described above is carried out, the catheter is exposed 
and may be contaminated. 
The package and method of packaging of the present invention overcomes 
these and other problems in the prior art. 
SUMMARY OF THE INVENTION 
The present invention provides a package for a sterilizable calibratable 
medical device such that the device is maintained in a clean environment 
during the calibration procedure. The medical device includes a hydratable 
sensing component. The package includes a wrap enveloping the medical 
device, first and second reservoirs, and a plumbing device. The wrap 
includes a gas-permeable surface. The first reservoir is substantially 
filled with a hydration solution which is suitable for hydrating the 
sensor component. The second reservoir is substantially evacuated and is 
sized to hold all of the liquid solution to be used in the preparation of 
the device. The plumbing device is adapted to reversibly establish, 
without breaching the wrap, either gaseous communication between the 
gas-permeable surface and the sensor component, or liquid communication 
between the first reservoir, the sensor component, and the second 
reservoir. In order to sterilize the device, plumbing, and the reservoirs, 
the plumbing device is adapted to establish gaseous communication between 
the sensor component and the ambient environment of the plumbing device, 
and the package is exposed to sterilizing gas. The gas passes through the 
gas-permeable surface and the plumbing device to the sensor component. 
In accordance with other aspects of the present invention, a 
gas-impermeable chamber is defined which includes the ambient environment 
of the plumbing device. In this manner, the gaseous composition of the 
ambient environment of the plumbing device is controlled. The chamber may 
be defined by a bag suitable for enveloping the wrap. 
In accordance with further aspects of the present invention, the package 
includes a delivery device for delivering the hydration solution from the 
first reservoir into the plumbing device. Accordingly, the first reservoir 
is rupturable by the delivery means. The first reservoir is ruptured and 
the hydration solution is directed to the sensor component in order to 
hydrate the sensor component. 
In accordance with additional aspects of the present invention, the sensor 
component includes at least one optical fiber. 
In accordance with still further aspects of the present invention, the 
plumbing device is adapted to reversibly establish liquid communication 
between the ambient environment of the package, the sensor component, and 
the second reservoir. In this manner, calibration solution that is held in 
a container exterior to the wrap is directed to the sensor component 
without removing the medical device from its clean environment, thereby 
reducing the possibility of contamination. 
In accordance with still further aspects of the present invention, the 
package includes a third reservoir substantially filled with a calibration 
solution suitable for calibrating the sensor. The plumbing device is 
adapted to reversibly establish, without breaching the wrap, liquid 
communication between the third reservoir, the sensor component, and the 
second reservoir. The device is attached to monitoring instrumentation by 
removing the device cables from the wrap at a point remote from the sensor 
component and connecting them to the instrumentation. In this manner, the 
device is calibrated without removing the medical device from its clean 
environment. Additionally, the temperatures of the calibration solution 
and the sensing component are controlled throughout the calibration 
process to ensure that the calibration measurements are obtained at a 
temperature substantially equivalent to the temperature at the point of 
use. 
The packaging technique of the present invention allows a blood gas 
catheter to be calibrated immediately prior to use without the need for a 
blood gas analyzer to obtain a reference value if the blood gas analyzer 
values for the calibration solution are well known. The calibration 
technique is practical and allows calibration using aseptic handling that 
protects the cleanliness of the medical device and minimizes the 
possibility of contamination of the sensor component.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With reference to FIG. 1, one preferred embodiment of package 10 includes 
manifold 12, plumbing 14, inner wrap 16, and outer wrap 18. The manifold 
includes deposit reservoir 20, hydration reservoir 22, and flap 24. The 
deposit reservoir 20 and hydration reservoir 22 are connected to a medical 
device such as catheter 30 by plumbing 14. The plumbing is connected to 
the catheter at the sensor component 32 which includes the analyte sensing 
components of the catheter. The sensor component may also include a 
temperature measuring component. The sensor component 32 is disposed 
within the plumbing. The catheter also includes one or more 
instrumentation cables 34 which ultimately connect the catheter 30 to the 
remainder of the medical monitoring device (not shown). The sensor 
component extends from the cable 34. At the sensor-cable connecting point, 
a cable flange (not shown) extends radially from the cable. 
The plumbing 14 includes hydration tube 40, flush tube 42, calibration tube 
44, delivery device 46, sterilization tubes 48, stopcocks 50a and 50b, gas 
filter 51, and directional valve 52. Preferably, all of the tubing in 
plumbing 14 is polyvinyl chloride (PVC) tubing. Such tubing is easy to 
handle and is slightly gas-permeable over an extended period of time. 
The stopcocks 50 are three-way adjustable valves. The settings of the 
stopcocks are manually adjustable and are easily manipulated through the 
packaging materials. The stopcocks are used to control the flow of 
solution through the plumbing. Caps 53a and 53b overlay the stopcocks in 
order to protect the packaging material from damage caused by protrusions 
on the stopcocks. 
Hydration tube 40 is in full communication with hydration reservoir 22, a 
sterilization tube 48, and stopcock 50a. Flush tube 42 is in full 
communication with the deposit reservoir 20, a sterilization tube 48, and 
directional valve 52. Directional valve 52 allows solution to flow through 
flush tube 42 into the deposit reservoir and prevents solution flow in the 
opposite direction. Calibration tube 44 is in full communication with 
filter 54 and stopcock 50a. Filter 54 is preferably a hydrophobic filter 
through which gaseous solutions freely pass and which prevents the passage 
of liquid solutions. 
Delivery device 46 includes catheter tube 57, joint 58 and connect tube 59. 
One end of catheter tube 57 is connected to stopcock 50a. The other end of 
the catheter tube is connected to joint 58. Joint 58 connects catheter 
tube 57, connect tube 59 and cable 34. The connect tube is connected to 
stopcock 50b. The joint provides fluid communication between the catheter 
tube and the connect tube. Delivery device 46 is preferably used to 
deliver the sensor component to the patient, i.e., the delivery device is 
an integral component of the blood gas catheter. Thus, the materials used 
for delivery device 46 are compatible with the packaging procedure as well 
as with the blood gas monitoring procedure. 
The sensor component extends from cable 34, through joint 58 and into 
catheter tube 57. The joint includes a ring seal (not shown) through which 
the sensor component extends and against which the cable flange is 
pressed. The ring seal and flange prevent the flow of solution from the 
joint to the cable. The position of the cable and sensor component 
relative to the joint is fixed by a suitable attachment mechanism such as 
a nut screwed over the joint and against the flange. In this manner, any 
fluid flowing between stopcock 50a and 50b passes over the sensor 
component. 
Stopcock 50b is connected to filter 51 and directional valve 52. Filter 51 
is preferably a hydrophobic filter through which gaseous solutions freely 
pass and which prevents the passage of liquid solutions. 
The plumbing establishes gaseous communication between the sensing 
component and the plumbing ambient environment by means of sterilization 
tubes 48, filter 51, and filter 54. The plumbing also establishes liquid 
communication between the manifold reservoirs and the sensor component by 
hydration tube 40, delivery device 46, and flush tube 42. 
Inner wrap 16 includes sides 60a and 60b. Side 60a includes filter 61 along 
one edge. The filter 61 is preferably a bacterial retentive hydrophobic 
filter. An exemplary filter 61 is a fibrous paper-like membrane 
manufactured by E. I. DuPont de Nemours & Co. and referred to by the 
trademark TYVEK. The filter allows gas exchange between the interior and 
exterior of inner wrap 16 when the wrap is otherwise sealed in a 
gas-impermeable manner. The remainder of the material of side 60a is 
preferably clear so that the packaging is easily viewable therethrough. 
The material is also relatively thin and flexible so that the adjustments 
to the packaging, e.g., the stopcocks, are easily carried out through the 
wrap. 
During the packaging process, catheter 30 is sterilized dry, and then 
hydrated and prepared for calibration. With reference to FIG. 2, hydration 
reservoir 22 and deposit reservoir 20 are connected to catheter 30 at 
sensor component 32 by plumbing 14. These components are placed between 
the sides 60a and 60b of inner wrap 16 and the outside edges of the inner 
wrap are completely sealed by edge seals 55. Flap 24 of the manifold is 
caught between the edge seals to secure the position of manifold 12 within 
inner wrap 16. Additionally, seal 56 preferably secures the position of 
catheter 30 within the inner wrap by securing the gathered cable 34. The 
manifold 12 and catheter 30 are positioned within the inner wrap so that 
plumbing 14 is and remains untangled relative to the catheter, and so that 
access to filter 61 is not blocked. Once the inner wrap edges are sealed, 
filter 61 is the only means of gaseous communication between the interior 
and the exterior of the wrap. 
Prior to the sterilization process, stopcocks 50 are open so that the 
lumens of the hydration tube, calibration tube, catheter tube, connect 
tube, and flush tube are all in fluid communication. In order to sterilize 
the catheter, sealed inner wrap 16 functions as a breather bag. The wrap 
is simply a gas-permeable container which acts to keep the gaseous 
environment within it free from bacteria and germs. A sterilizing gaseous 
solution, preferably ethylene oxide (ETO), is pumped into inner wrap 16 
through filter 61. This is performed by pressurizing the atmosphere 
surrounding inner wrap 16. The ETO flows freely over catheter 30, plumbing 
14 and manifold 12. Additionally, the ETO flows into plumbing 14 through 
sterilization tubes 48, filter 51, and filter 54. In this manner, sensor 
component 32 and the interior surfaces of the plumbing and the manifold 
are sterilized. After sterilization, the ETO is outgassed from inner wrap 
16 by allowing the inner wrap to stand and the ETO to dissipate in a 
controlled environment. 
Preferably, all surfaces and passageways of manifold 12, plumbing 14, and 
catheter 30 are sterilized during the ETO procedure. Certain joints and 
attachments in plumbing 14 may be so tight that they are essentially ETO 
impermeable and therefore hinder or restrict access of ETO. These joints 
and attachments are loosened prior to the sterilization procedure and are 
tightened immediately thereafter. 
After sterilization, sterilization tubes 48 are sealed with seals 62 (shown 
in reference). Preferably, tubes 48 are sealed by a radio frequency (RF) 
sealing technique. This technique affects a heat seal without affecting 
the integrity of inner wrap 16. After seals 62 are in place, the only 
points of entry remaining in plumbing 14 are through manifold 12 via 
hydration tube 40 and flush tube 42, filter 51, or through filter 54. 
Alternatively, sterilization tubes 48 include filters 64 (shown in 
reference). Filters 64 are preferably hydrophobic filters which allow 
gaseous solutions to pass freely through, but liquid solutions, such as 
the hydration solution, are not allowed to pass through. If such filters 
are used, the sterilization tubes 48 do not require sealing after the 
sterilization process. 
During the foregoing ETO sterilization procedure, the surfaces exposed to 
the ETO are completely dried. Thus, sensor component 32 is rendered 
nonfunctional since it operates in a moist environment. Sensor component 
32 must be hydrated after sterilization and prior to use. Manifold 12 and 
plumbing 14 are used to hydrate the sensor component without removing it 
from its sterile environment within inner wrap 16. 
In order to hydrate sensor component 32 within the sterile environment of 
inner wrap 16, a hydration solution is included within the inner wrap. The 
hydration solution is held and protected throughout the sterilization 
procedure in hydration reservoir 22. After sterilization, the hydration 
solution is released from hydration reservoir 22. Manifold 12, in 
conjunction with plumbing 14, delivers the hydration solution to sensor 
component 32 which is the portion of catheter 30 which requires hydration 
to be functional. The remainder of the catheter is maintained in a dry 
state. 
With reference to FIG. 3, one preferred hydration reservoir 22 includes 
rupture plate 68, container 70, and outer envelope 72. Container 70 is 
suitable for holding a liquid such as a hydration solution or calibration 
solution. Container 70 protects the solution from contact with the ETO 
which is highly toxic. The container material is impermeable to ETO and is 
capable of withstanding the pressure and temperature changes that occur 
during a standard ETO sterilization process. In this manner, the solution 
is maintained in a sterile and nonpyrogenic state. Additionally, the 
container material is rupturable by mechanical pressure as will be 
discussed below. One suitable material for container 70 is 
foil-polypropylene laminated film. 
Rupture plate 68 is preferably made up of a relatively rigid material. The 
plate is flat and corresponds in surface area to the surface of container 
70. The rupture plate includes point 74 which, under adequate mechanical 
pressure, turns downwardly towards container 70 to rupture the container. 
The rupturing position is shown in reference. 
With reference to FIG. 4, outer envelope 72 is formed about container 70 
and rupture plate 68 so that there is adequate room within the envelope 
for the solution to flow from the container into the envelope and to 
hydration tube 40. Envelope 72 and deposit reservoir 20 are preferably 
made from two pieces of material that are connected by seals 73 (shown in 
reference) so that deposit reservoir 20, envelope 72, and flap 24 are 
formed. Container 70 is configured so that the container does not block 
the hydration tube when sealed within envelope 72. Flat edges 77 along the 
perimeter of container 77 aid in this positioning. Hydration tube 40 and 
flush tube 42 are sealed in communicating relationship with the interior 
of envelope 72 and the interior of deposit reservoir 20, respectively. 
Referring again to FIG. 2, in order to hydrate sensor component 32, 
stopcock 50a is adjusted so that the fluid path betwen hydration tube 40 
and catheter tube 57 is open. Stopcock 50b is adjusted so that the fluid 
path between connect tube 59 and valve 52 is open. Container 70 is 
ruptured as discussed above. The contents of the container are forced into 
envelope 72 by applying uniform pressure to rupture plate 68 against the 
container. The hydration solution flows through envelope 72 and hydration 
tube 40 to delivery device 46. Once the delivery device is filled with 
hydration solution, stopcocks 50a and 50b are adjusted in order to close 
off the delivery device thereby securing the solution over sensor 
component 32. The solution is held there in order to adequately hydrate 
the sensor component. Preferably, some of the hydration solution is held 
in the delivery device during the storage period, i.e., until calibration 
takes place. In this manner, sensor component 32 is held in a hydrated 
state during the storage period. 
Preferably, the hydration fluid contains a chemical composition the same or 
very close to the composition contained in the initial calibration 
solution to be used with the device. Each solution content is highly 
sensor specific. The hydration solution may be formulated to also act as a 
calibration solution and be used to establish a first calibration point of 
the sensor component, e.g., by equilibrating the hydration-calibration 
solution with gases at levels appropriate for calibration of the specific 
analyte sensor in sensor component 32. 
After sensor hydration has taken place, catheter 30 is preferably incubated 
to aid in returning the catheter to a functional state, and to stabilize 
the sensor component chemistry. Sensor component 32 is incubated in the 
hydration solution that is held within catheter tube 57. To ensure the 
chemical balance of the solution is held constant, the package itself is 
incubated in a gas controlled environment. Inner wrap 16 is placed in a 
gas-impermeable container and flushed with a gaseous solution. The gaseous 
solution in which the inner wrapper and contents are incubated has 
chemical characteristics that are essentially the same as those of the 
dissolved gases in the hydration solution. The gaseous solution is also 
pre-equilibrated with water, i.e., the solution is hydrated. This 
characteristic of the gaseous solution prevents the solution from drawing 
the water off of the hydration solution held within delivery device 46. 
The gaseous solution passes through filter 61 into the interior of the 
inner wrap. Because of this controlled environment external to plumbing 
14, no change in the chemical composition of the hydration solution will 
be affected due to the slight gas-permeability of delivery device 46. The 
dissolved gases in the hydration solution are thus maintained at the 
desired level. The time period, temperature, and gaseous composition for 
incubation are highly dependent on the sensor component elements and 
intended use. 
For storage purposes, the gas-permeable portions of inner wrap 16 are 
sealed off. Preferably, the wrap is placed within outer wrap 18. The outer 
wrap is gas-impermeable and acts to seal the inner wrap gas-permeable 
sections including filter 61. Outer wrap 18 creates a constant gaseous 
environment surrounding catheter tube 57 and sensor component 32. A 
gaseous solution is pumped into the outer wrap and passes into inner wrap 
16 through filter 61. The gaseous solution preferably has similar chemical 
characteristics to the incubation solution and the hydration solution. 
Again, the controlled environment ensures that the composition of gases 
dissolved in the hydration solution will not be altered by gaseous 
exchange through the delivery device. In this manner, the chemical 
composition of the hydration solution in the delivery device is maintained 
at a constant level throughout the storage period. Prior to use, depending 
upon the specific sensor component, it may be preferable to again incubate 
the entire package to further enhance the response of the sensor 
component. 
With reference to FIG. 5, calibration tube 44 and cable 34 are removed from 
both inner wrap 16 and outer wrap 18 at a point remote from the sensor 
component 32. The cables are connected to monitoring instrumentation (not 
shown). In this manner, the readings obtained by the catheter 30 are 
transmitted to the monitoring instrumentation. 
Preferably, calibration tube 44 is small-bore tubing that has a small 
volume. This configuration reduces the amount of fluid that must be 
displaced when one or more calibration solutions are introduced into the 
plumbing. 
To calibrate the device, two calibration solutions are typically used. Each 
solution contains a predetermined concentration of the targeted analyte. 
Filter 54 is removed from calibration tube 44 and an injection device (not 
shown) is attached thereto. A container of calibration solution is 
attached to the injection device. The injection device preferably includes 
a stopcock. The calibration solution passes from the container through 
calibration tube 44 and stopcock 50a to catheter tube 57 and connect tube 
59. Stopcock 50b is set so that the solution flows through the stopcock to 
deposit reservoir 20 until enough solution from the delivery device 46 has 
been displaced to ensure that all of the solution held within the delivery 
device is the first calibration solution. At that point, the stopcock on 
the injection device is closed to hold the calibration solution within the 
delivery device. 
Preferably, the temperatures of the calibration solution and sensor 
component are controlled throughout the calibration process. The 
temperatures are brought to and maintained at a temperature substantially 
equivalent to the temperature of the point of use of the sensor component, 
e.g., body temperature for a blood gas catheter. This control ensures that 
the calibration measurements taken are accurate. The temperature of the 
calibration solution is adjusted while the solution is in the container 
prior to delivery to the sensor component. The temperature of the wrap and 
its contents is adjusted by inserting the wrap between the sides of a 
thermal blanket. The wrap remains enveloped by the thermal blanket 
throughout the calibration procedure. In this manner, the sensor component 
is maintained in its clean environment during the calibration procedure. 
If the sensor component includes a temperature sensing component, the 
temperature sensing component is utilized to provide component temperature 
information. 
Once the calibration solution is delivered to the delivery device and the 
temperature of the sensing component stabilized, analyte measurements are 
taken via cables 34. Once the measurements are taken, the injection device 
stopcock is opened and a second solution is transmitted to delivery device 
46 in a similar manner. As an alternative method of retaining the 
hydration solution within the delivery device, stopcocks 50a and 50b are 
closed to hold the solution therebetween while the calibration 
measurements are taken. 
Once calibration is completed, a parenteral grade saline solution is 
flushed through the plumbing to wash out any remaining calibration 
solution. The solution is introduced to the plumbing through calibration 
tube 44. The catheter is then removed from the package by disconnecting 
the delivery device from the remainder of the plumbing. The joints at 
stopcocks 50a and 50b are disconnected and delivery device 46 and sensor 
component 32 are removed as a unit. The remainder of the package is 
disposed of. 
Since all solutions are flushed into deposit reservoir 20, the reservoir is 
sized so that its capacity is equal to or greater than the total volume of 
all of the hydration, calibration, and cleaning solutions to be used to 
prepare the catheter for use. 
With reference to FIG. 6, a preferred package embodiment 82 is similar to 
package 10, but includes calibration reservoirs 84a and 84b, each 
containing a separate calibration solution, as well as reservoir 85 
containing a hydration solution. (Similar components between packages 82 
and 10 will be referred to with the same reference numbers.) The 
calibration reservoirs are similar to reservoir 22 of package 10. Each 
reservoir includes a rupture plate 86, a container (not shown), and an 
envelope 90. The plumbing 92 includes calibration tubes 98a and 98b, 
sterilization tubes 100a and 100b, and passage tube 102. The calibration 
tubes are connected to the calibration reservoirs along the seals of 
envelopes 90a and 90b. The calibration tubes are connected to passage tube 
102 which is connected to stopcock 104. Stopcock 104 is similar to 
stopcock 50a. The remainder of plumbing 92 is similar to plumbing 14. The 
package also includes deposit reservoir 109 sized so as to receive all of 
the hydration and calibration solutions and any cleaning solutions to be 
used. 
To prepare catheter 30 for use, an ETO sterilization procedure as described 
above is carried out. Sensor component 32 is then hydrated and incubated. 
Inner wrap 16 is packaged in outer wrap 18 for storage purposes. Prior to 
use, cables 34 are removed from the inner and outer wraps and connected to 
monitoring instrumentation. Calibration reservoir 84a, including the first 
calibration solution, is ruptured and the solution directed into delivery 
device 46. The stopcocks are adjusted to hold the solution in the delivery 
device. The temperature of the sensor component is controlled as described 
above. Calibration measurements are taken when the temperature of the 
sensor component is stabilized and correct. Once the first calibration 
measurement is completed, calibration reservoir 84b, including the second 
calibration solution, is ruptured and the solution directed into the 
delivery device. The temperature of the sensor component is again 
stabilized and corrected. The second calibration point is then established 
and the catheter is ready for use. 
In each of the above-described embodiments, the sensor component may be 
brought to first calibration point conditions by utilizing a specifically 
equilibrated hydration solution. The hydration solution is equilibrated 
with a gaseous composition equivalent to that used to create the first 
calibration solution. When the first calibration point conditions are 
achieved in this manner, only one calibration solution, that corresponding 
to the second calibration point conditions, need be introduced to the 
sensor component during calibration. This reduces the steps required to 
prepare the catheter for use. Similarly, if the package is for a medical 
device that requires the setting of only a single calibration point, then 
a properly equilibrated hydration solution is the only solution necessary 
to prepare the device for use. In such an instance, the plumbing need not 
include a calibration section for delivering calibration solution to the 
sensor component. To utilize such a device, the instrumentation cables are 
removed from the packaging and connected to monitoring instrumentation. 
The sensor component is already immersed in the hydration solution that 
acts as the calibration solution. Calibration measurements are immediately 
taken and the device is then ready for use. 
As an example of the relationships between the various solutions and the 
sensor component, if a blood gas catheter were to be used to measure pH, 
PO.sub.2 and PCO.sub.2, the buffer formulations for the calibration 
solutions would be selected to control the relationship between pH and 
PCO.sub.2. Calibration solutions are characterized by their differing 
PCO.sub.2 levels. 
The following solution is a specific example of a solution that is suitable 
for use with the above-described catheter: 
0.916 grams/liter potassium phosphate; 
3.007 grams/liter sodium phosphate; 
6.136 grams/liter sodium chloride; and 
1.848 grams/liter sodium bicarbonate. 
The solution is a bicarbonate-phosphate buffer which contains 105 mM sodium 
chloride which is the sodium chloride level that is substantially 
equivalent to that found in blood. The solution is adjusted with carbon 
dioxide gas and compressed air, or the equivalent oxygen/nitrogen mixture, 
to form the hydration and calibration solutions. 
It has been found that the inclusion of sodium chloride in the preparation 
solutions is useful to reduce perturbations in the measuring process that 
are caused by the existence of predominate ions other than the targeted 
analyte(s) in the solution being monitored. In blood, sodium chloride is a 
predominate ionic compound that is not monitored by the blood gas catheter 
of the example. If the preparation solutions in which the sensor component 
is hydrated and calibrated do not contain the chloride component, an ionic 
gradient is created across the sensor component membrane when the sensor 
component is actually used in blood. This gradient effects the subsequent 
monitoring information received from the sensor component. 
A suitable time and temperature for incubation of such a PCO.sub.2, 
PO.sub.2 and pH sensor has been found to be at least 7 days at a 
temperature of approximately 20.degree. C. This incubation is adequate to 
bring the sensor component of the catheter to calibration conditions 
reflected in the amount and type of chemicals included in the gaseous 
mixture. Prior to use, it is preferable to again incubate the entire 
package for approximately 7 days at a temperature substantially equivalent 
to the temperature at the point of use. For an in situ blood gas catheter, 
the temperature range for the second incubation is 37.degree. to 
40.degree. C. The second incubation has been found to improve the pH 
response time of the catheter. The catheter is then in a state for final 
calibration and use. 
While preferred embodiments of the invention have been illustrated and 
described, it will be appreciated that various changes can be made herein 
without departing from the spirit and scope of the invention. Other 
methods and devices for holding and delivering the solutions in the 
manifold are available. For example, the solutions could be held directly 
in the envelopes and the plumbing means could include stopcocks for 
controlling the flow of the solutions from the envelopes into the plumbing 
means. Additionally, directional valves or other fittings are suitable for 
use in place of the stopcocks. 
Many of the specific characteristics of the preferred embodiments depend 
upon material compatibility and the specific sensor component of the 
packaged device. For example, if a strong gas-impermeable clear material 
through which the stopcocks are adjustable is available and compatible 
with the procedures, this material is suitable for forming inner wrap 16. 
If this inner wrap is gas-impermeable, with the exception of filler 61, 
then the device is storable over an extended period of time without the 
outer wrap once the gas-permeable portions of the inner wrap are somehow 
sealed. This is also the case if the sensor component is held in a 
gas-impermeable plumbing section. The process of creating a constant 
gaseous environment about the plumbing for storage and incubation purposes 
is not necessary if the delivery device itself is gas-impermeable. 
Other means for sealing off filter 61 during storage are available. The 
filter is covered with a seal patch, or the wrap portion including the 
filter is separated from the remainder of the wrap by a seal through the 
sides 60a and 60b of the inner wrap. In an alternative configuration, one 
or both sides 60a and 60b of inner wrap 16 are made of TYVEK membrane, or 
other suitable gas-permeable material, to increase the gas exchange rate 
through the inner wrap. In these embodiments, a gas-impermeable chamber is 
formed within which the gaseous environment about the plumbing is held 
during storage. The chamber may be formed by means of an outer wrap as 
described above. 
Further, if a suitable ring and seal material are used, calibration tube 44 
may be positioned outside of the package. In one embodiment, the 
calibration solution is then delivered through the calibration tube 
without breaching the wrap. Similarly, if the cables of the medical device 
are connectible to the monitoring instrumentation without breaching the 
wrap, the device is maintained in a sterile environment during the 
calibration procedure. 
Finally, it is to be understood that the package and method of packaging of 
the present invention are not limited to blood gas catheters. The 
configuration of the sensor component of a specific device may dictate 
alternative configurations for the packaging.