Portable Oxygen: A User's Perspective


Liquid Oxygen


Introduction Reservoirs
Small Units Freezing Up
Midsize Units Index 
Large Units


Portable Oxygen: A User's Perspective

Liquid Oxygen

Introduction

Oxygen becomes a liquid when its temperature reaches about 300 degrees Fahrenheit below zero. At this temperature it takes up a tenth of the space of compressed oxygen. If you use liquid oxygen, your oxygen provider will set up one or more liquid oxygen reservoirs in your home. They will schedule regular visits to fill the reservoirs. 

You will fill a portable unit from the reservoir. Some reservoirs have a fill port on the side and some have a port on the top. Some have valves on both top and side.

If your reservoir has a port to which a supply tube can be connected, you use the liquid oxygen directly from its reservoir. To do so, connect one end of your supply tubing to this port and the other end to your cannula. Use the rotary switch next to this port to adjust the flow rate.

Liquid oxygen may be safer to handle than compressed oxygen. It is stored under far less pressure than compressed oxygen (21 psi vs. 2,000 psi). So long as the vessels containing liquid oxygen are upright, there is little danger of leakage. The greatest danger is burns to the skin should you touch the very cold ports while filling. 

Liquid portable units come in two sizes. 

  • The smaller units hold less than 0.7 Liters of liquid oxygen and weigh less than 6 lbs. All but one has a built-in conserver.
  • The larger liquid portable units hold a liter or more of liquid oxygen and weigh 6 to 9 lbs. None has conservers. You can get them in two versions-- one with continuous flow settings from 0 to 6 Lpm and the other with settings up to 15 Lpm. It is this high flow version that is used by those of us who need more than 6 Lpm.

Small Units

There are five described units in this category. All but the Caire's Sprint have built-in conservers. Both Puritan-Bennett's Companion 550 and Mallinckrodt's Helios have a pneumatic conserver. Both Penox's Escort and Caire's Spirit have electronic every-breath conservers.

Whereas folks who use compressed oxygen have an easy-to-read contents gauge, those who use liquid oxygen measure the contents by the "fish scale" method, that is, you grasp the scale strap and lift the tank high enough so the gauge on its side is at eye level. The carry case of Helios and Escort must first be removed. Once calibrated, the scale on the Spirit will operate with the case attached.

These fish scales are not very accurate. One user told me he could get any reading he wanted, just by holding the scale strap in a different way. The Sprint has a more accurate electrical gauge, which requires a 9-volt battery, that is active at the press of a button.

Table 1
Small Liquid Portables



Sprint

Spirit

Escort

EasyMate
Capacity





Liquid (liters)
0.63
0.33
0.33
0.38
0.34

Gaseous (liters)
513
308
308
275
277

Liquid (lbs.)
1.5
0.9
0.91
1.14
.94
Duration @ 2 Lpm (hrs.)




Continuous 
4
N/A 2.3 N/A

Conserver
N/A
7 7.8 7.8
8
Weight (lbs.)





Empty
4.5
2.8
2.5
3.5 2.6

Full
6
3.6
3.4 4.6
3.6
Dimensions (in.)





Height
13
10.5
8.8 10 8.2

Width
6.5

6.0 5.8 3.6

Depth
4

4.5 4.2 4.8
Pulse Settings N/A 0 - 4 0 - 5 0-6 0-4
Flow Rates (Lpm)
0 to 6
N/A
2 2 N/A
Filling Duration (min.)
1.5
0.4
1.0 0.5 0.30
Filling Valve Location
side/bottom
bottom bottom bottom bottom
Operating Pressure (psi)
20
22
20 20 20
Evaporation (lbs./day)
1.2
1 - 1.5
1.2 ?

Sprint
The Sprint, manufactured by Caire is the only small size liquid oxygen unit without a conserver. It lasts about 4 hours on continuous flow at 2 Lpm. It has a double strap--one for hand carry and the other for the shoulder. The single cannula port, flow control knob, and contents gauge are all located on the top and are easily accessible. 

The flow control knob has 12 settings from Off to 6 Lpm. Its contents dial can be illuminated at the press of a button, courtesy of a 9-volt battery. 

The Sprint fills through the bottom. Its fill lever is located on the side. 

Helios
Helios is an oxygen system first developed by  Nelcor Puritan-Bennett (NPB). It was first marketed by Mallinckrodt and is now marketed by the Puritan-Bennett division of Tyco.

There are two liquid oxygen units that carry the name "Helios." One is the model H300 that first appeared on the market several years ago. With some improvements it was renamed the "Helios Plus." The Helios Plus retains the model number H300.

In late 2003, Puritan-Bennett released a second Helios, called the Marathon. It is the model 850. (When full, the model H300 stores a little over 300 liters of gaseous oxygen in liquid form. When full, the model H850 stores 685 liters. Do you, like I, wonder why the Marathon model number is not H685?

The following two sections describe both of these Helios units. Specifications appear in the above table.

Helios (Plus) (H300)
The H300 can be packaged to address both home and portable oxygen needs. The purpose of this package is to replace the concentrator as well as portable oxygen systems that use compressed oxygen in cylinders.

Helios H300 is the lightest weight and longest lasting of portable oxygen units currently available. The Helios conserver addresses liter flows settings up to 4. It does not have a continuous flow setting. Helios will operate in an upright position, on its back, or at any position in between.

With its low loss reservoir, Mallinckrodt claims that providers can schedule deliveries less frequently. Deliveries which were once required every 7 to 10 days, they say, are now required much less often.

Mallinckrodt has also improved the reservoirs which it markets with the portable unit. It is possible to connect the reservoir to your phone line so your provider can monitor the oxygen level. By so doing, your provider can provide refill services more efficiently.

Some oxygen providers market Helios as a portable system only. The reservoir these providers supply does not have a connection for a tubing between reservoir and the portable unit, so it cannot be used in stationary mode. Helios fill port is compatible with NPB and Caire top fill reservoirs.

Helios may be carried by its convenient handle or placed in a specially-designed carrying bag which has straps that go around the waist, over a shoulder, or both. Of this bag, Kathy of Topeka writes: 

I generally wear my Helios on my shoulder, although it makes my shoulder hurt.  It is much easier around the waist, but, then it gets in the way in the car. I really like the idea about fastening both to the waist and the shoulder to better distribute its weight. But then I will still have the problem with it in the car, especially if I am driving.
To find out more about Helios, visit other sites which describe it. See the manufacturer's website and a patient's website, Ron O'Kane See also  A Comparison of Spirit and Helios Portable Oxygen Systems

Spirit
Caire has developed the Spirit 300 liquid portable system. The Spirit is an electronic every-breath conserver which requires two C cell batteries and uses a single lumen cannula. It comes in a fabric case with a shoulder strap. Its contents gauge is on the top and is activated when the unit is held aloft by its shoulder strap. It is designed to be used in an upright position, only. It can be filled from a reservoir from either its side or bottom port.

The Spirit provides both continuous and pulsating flow. When its flow selection knob is set to::

  • a numbered setting, it dispenses the selected size pulse on each inhalation. For example, when this switch is set to 2, it delivers a 30 ml pulse.. It has a duration of 7 hours with a 2 Lpm user whose breathing rate is 20 bpm.

  • CF, it delivers a factory set continuous flow at a rate of 2 Lpm. At this setting it has a duration of 2.6 hours.
There are  low battery  and pulse mode indicator. The indicator glows green each time an inhalation is detected, whether or not there is oxygen remaining. When the  indicator glows red, you should replace the batteries. The manufacturer suggests that frosting and freezing up can be reduced by removing moisture from the condensation pad, located un the bottom of the unit. A users guide is available online at the Caire website. See also  A Comparison of Spirit and Helios Portable Oxygen Systems.

Escort
Penox  has developed both electronic and pneumatic versions of its Escort liquid portable system.   Both versions are available in 50 and 20 psi  pressure systems. You have the 50 psi system if you fill your Escort in its side. It is the 20 psi system if you fill it at its bottom.

The electronic versions of the Escort are every-breath conservers which require two AA batteries and use a single lumen cannula. It weighs 4 pounds when filled, has a built-in carrying handle and operates upright, on its back, or any position in between. It is not designed to operate while on its side.. It has an easy-to-read contents gauge located on the back of the unit. The contents gauge operates when the unit is held up by its contents indicator strap.

The Escort has a continuous/pulsating flow switch and a rotary pulse selection switch. When the continuous/pulsating flow switch of an electronic version of the Escort is set to 

  • pulsating, it dispenses a pulse on each inhalation of a size selected with the rotary pulse selection switch. When this switch is set to 2, it delivers a 33 ml pulse. It has a duration of 7.8 hours with a 2 Lpm user whose breathing rate is 20 bpm.

  • continuous, it delivers a factory set continuous flow at a rate of 2 Lpm. At this setting it has a duration of 2.6 hours.
There are low battery  and pulse mode indicators. The pulse mode indicator glows green each time an inhalation is detected, whether or not there is oxygen remaining. When the low battery indicator turns red, replace the batteries.

EasyMate
The EasyMate, developed by Precision Medical, is a small and long lasting portable. It is cylindrical in shape and easily fits into the accompanying bag which can easily be worn on the hip. There is a fabric handle that is used for carrying when the bag is not used.

The EasyMate uses a cannula wih single tubing. Its fill valve, cannula port, and setting selection switch are all near the top of the unit. Whereas most other portable sweat at the sides and bottoms, this one sweats only around its domed top. A clear plastic cover is available to protect the unit's top.

The thumbed setting switch has five settings from 0 (off) to 4. (Those of us who find it painful to rotate their wrist may find this type of switch easier.) There is an audible "click" at each setting. (This means that the user can change settings without looking at the switch.)

The conserver is the EasyPulse, used for compressed oxygen systems. It delivers the same amount of oxygen at a given setting, regardless of the user's breathing rate. Should your respiration increase with exercise, you will probably have a higher setting than when at rest.

The EasyMate, like other small and midsize portables, relies on a scale that measures weight to determine how much liquid oxygen is left. Unlike other portables, the EasyMate has a separate cylindrical contents scale that is the length of a wood pencil and about four times the diameter. If you have secured it so it won't get lost, slide one end of the scale in the slot on the top of the EasyMate, then hold the scale aloft by the strap on the scale, and you can read the weight of the remaining oxygen.

I say "read" but, like all other liquid portables, only the full and empty positions on the gauge are marked. You are left to interpolate whether your unit is half full, three quarters full, or ...At least a gas gauge in an automobile, as inaccurate as it is, has intermediate settings between full and empty.

Midsize Units

Midsize liquid portables are slightly heavier and have longer durations than the small liquid portables. When filled, the midsize weight about 2 pounds more and have durations of 6 to 10 hours longer than the small liquid portables.

If you usually go out for trecks of longer than 7-8 hours, or if you don't carry your portable but for short distances, a midsize might be the one for you. 
Table 2 
Midsize Liquid Portables



Helios Marathon Caire
Spirit 600
Capacity


Liquid (liters)
0.67
0.85
0.63

Gaseous (liters)
542
685
516

Liquid (lbs.)
1.6
2
1.5
Duration @ 2 Lpm (hrs.)

Continuous 
4.6
5.6
4

Conserver
8.5
17
13
Weight (lbs.)


Empty
3.9
3.6
4.1

Full
5.5
5.5
5.6
Dimensions (in.)



Height
10.9
15
11.5

Width
5.75
6
6

Depth
4.25
4.5
4.5
Pulse Rates 0-6 0-4 0-6
Flow Rates (Lpm)
0 to 6
0-6 2
Filling Duration (min.)
1.1
1
?
Filling Valve Location
bottom
bottom
side/bottom
Operating Press. (psi)
22
22 20
Evaporation (lbs./day)
1.2-1.8
85-1.0 1.2
*The Companion 550 is no longer manufactured but may still be in the inventory of your provider. 

Companion 550
The NPB Companion 550 is marketed by Mallinckrodt. It has a built in conserver. Its sister, the Companion 500 , is identical but without a conserver. 

Both have a dual strap--one for shoulder carrying and the other for hand carrying. The tank is contoured to fit neatly against you when the strap is over your right shoulder. They fill through the bottom and the fill lever is on the top. The flow control knob is on the top and has 12 settings from Off to 6. This knob is recessed, making it difficult to turn. I have found that both the Salter 4804 and 4807 cannulas do not fit snuggly to the Companion 550, and disconnect easily and often. The four-foot long NPB cannula (NPB 77858-00) fits snugly to the ports. 

The Companion 550 has a switch on the top to change from pulse to continuous flow. Set to pulsating flow, the conserver delivers a 1.5 ml bolus of oxygen at the beginning of an inhalation, followed by continuous flow at the user selected setting to the end of the inhalation. So it can sense the end of inhalations. It uses a dual cannula--one side delivers the oxygen and the other side senses the beginning and end of an inhalation. Ports for the cannula are located on the side of the unit. The instructional manual for this unit recommends continuous flow if you are prescribed 1 Lpm or less. The Companion 500 uses a single cannula.

The contents gauge is quite rudimentary. It is a balance scale and is read when the user holds the unit aloft by the front strap.

The manufacturer claims the 2 Lpm user will run out of oxygen after 8.5 hour on pulsating flow ( assuming a breathing rate of 20 bpm) and 4.6 hours on continuous flow. 

Helios Marathon (H850)
The H850 is Puritan-Bennett's replacement for the Companion 550. Like both the H300 and the Companion 550, it requires a dual cannula. It is pneumatic and requires no batteries. It can be hand carried, or, in a specially designed case, carried with a shoulder strap, or as a back pack. Whereas the 550 must be in an upright position to operate, the Marathon can operate on its back, upright, or any position in between.

Unlike the H300, the H850 can be switched to continuous flow. Whereas most conservers provide continuous flow at a factory set 2 Lpm, the Marathon, like the Companion 550 allows the user to set continuous flow to as high as 6 Lpm.

The Marathon has a single clearly marked rotary switch that controls all settings. From the orange-colored off  or 0 position, rotate the switch counterclockwise to one of the five demand (pulse) setting, labeled D 1.5 to D 4. Rotate it clockwise to one of the six continuous flow settings, labeled from C 1 to C 6. 

Spirit 600
Electronic conserver that requires 2 C-Cell batteries. Delivers a 3 ml pulse on each inhalation at setting 2. Contact me by email for more information.

Larger Units

To  my knowledge, these larger units are no longer manufactured and are no longer available new. They are available second hand through oxygen providers and from those who refurbish oxygen portables.

Two of the three larger liquid portables are also available in continuous flow only, with settings up to 15 Lpm. See Options for the Active High-Flow User

Table 2 
Large Liquid Portable Units

...

DeVilbiss
Model 1.0
NPB Comp.
1000
Caire
Stroller
Caire
Spirit
1200
Capacity



Liquid (liters)
1
1.25
1.25
1.25

Gaseous (liters)
800
1058
1026
1026

Liquid (lbs.)
2.4
3
3
3
Duration @ 2 Lpm (hrs.)


Continuous Mode
6.9
8.5
8
8

Conserver Mode
20.8
N/A
N/A 28
Weight (lbs.)



Empty
4.3-4.7
5-5.6
5
5

Full
6.7-7.1
8.1-8.7
8
8
Dimensions (in.)



Height
12.6
13.8-14.5
13.5
14

Width
7.1
8
8
8

Depth
4.7
4.5
4.5
4.5
Pulse Settings N/A N/A 0-6
Flow Rates (Lpm)
0 to 6
0 to 6
0 to 6
2
Filling Duration (min.)
1
1.1
2
?
Filling Valve Location
side
bottom
side/bot
side/bot
Operating Pressure (psi)
20
22
20
20
Evaporation (lbs./day)
-
1.3-1.5
1.2
1.2

Devilbiss Model 1.0
I know  little about the Devilbiss Model 1.0. I find no information about it so  I suspect it is no longer manufactured.

Stroller
The two portable liquid oxygen systems for continuous flow only are the Stroller (image), manufactured by Caire Medical , and the Companion 1000 (image) , manufactured by Puritan Bennett . Each weighs about 9 lbs. when full and has settings from 0 to 6 Lpm. Both systems have a cannula port, rotary selection switch, a contents gauge, and a carry strap.

Note:
The Stroller is the big brother of the Sprinter. It comes in two cases--the blue case and the beige one. The blue on comes in both side and bottom fill models, whereas the beige one is side fill only.

The cannula port of the Stroller is on the side. Both the selection switch and contents gauge are on the top, each under a separate covering lid. The selection switch has 11 settings from 0 to 6 Lpm. The contents gauge is electronic. Push its button and indicator lights tell you how much oxygen remains.

 NOTE. The contents gauge lights run on a 9 volt battery whose compartment is in the base of the tank. Replace the battery only when the tank is empty by turning it on its side and removing the two screws in its base to expose the battery compartment.

There is a warning light at one side of the gauge. When it flashes, it is time to replace the battery. I have rarely seen this indicator flashing. On two of my units,  when the gauge acted erratically, I replaced the battery and the gauge recovered and acted normally.

You, like I, may find it inconvenient to lift a lid each time you want to check the contents gauge or change the flow setting. This inconvenience can be easily remedied by removing the lids. Just remove two screws between the lids (under the tab with "Stroller" name on it) with an Allen wrench. Save the lids and screws in a plastic bag so they can be returned to your oxygen provider when you return the unit.

Companion 1000
The selection switch of the Companion 1000 is on the side. Both the contents gauge and the cannula port are on the top. The selection switch has 11 settings from 0 to 6 Lpm. The contents gauge which is very large and readable, operates like a spring-mounted fish scale. Lift the unit an inch or two above the floor by the front strap and the gauge's needle indicates the remaining contents.

Stroller and Companion 1000
The selection switches on both the Stroller and the Companion 1000 are very similar.
  • The switches of both are in a small indentation of the unit, requiring the user to use fingertips to adjust the flow rate. Adjusting the flow rate could be a problem for those users with severe arthritis.

  • The selection numbers are visible when viewed directly above the switch. This is more difficult to do when the switch is located on the side, as it is on the Companion 1000.  Fortunately, the switches on both are positive click--that is, you can feel each new position as you turn the switch. Learn your settings by counting the clicks.
The Stroller is a "side filler," meaning it is filled from the valve on the side of every reservoir, the same valve used to fill the reservoir. The Companion 1000 is a "top filler," meaning it is filled while sitting on top of the reservoir, like the Helios™. Only Puritan Bennett reservoirs are top-fill equipped. Filling effort  favors the top filler slightly, but  not enough to be important in selecting one portable over the other. Those who carry a reservoir in a vehicle may choose the side-filler because there is insufficient headroom to fill a top-filler portable.

Both units have a carry strap so the unit can be carried over the shoulder. The Companion 1000 is contoured, so it fits against your side. The beige Stroller is not. The Companion 1000 also has a shorter strap for carrying the unit in the hand.

Both liquid systems can be carried for short distances or pulled in a cart like the one used for the E cylinder. Because I need to sit and rest on walks of 10 yards or longer, I use a wheeled walker  which will carry two or three liquid portables and still give me a place to sit and rest.

Spirit 1200
Electronic conserver that requires 2 C-Cell batteries. Delivers a 3 ml pulse on each inhalation at setting 2. Contact me by email for more information.

 

Reservoirs

Reservoirs are usually selected by your oxygen provider and parked at your home or another location convenient to you where they are periodically refilled. Reservoirs are cylinders about 14 to 16 inches in diameter and about 29 to 40 inches tall. Filled, they weight between 100 and 160 lbs. Some reservoirs are designed for home use only, others to only refill portables, and others serve both purposes. Those which are designed specifically to refill portables may be low loss (LL) reservoirs which have a lower than usual evaporation rate. 

A reservoir is what you seek when your portable nears the empty mark. That reservoir may not be your "home" unit, but one you carry along in your motor vehicle. If you are on liquid oxygen and travel, you should look into the feasibility of carrying a small reservoir with you.

Table 3 shows the specifications on one 10 liter and three 20 liter reservoirs. The 20 liter units fit well in a motor home or SUV. Depending on your flow rate, you can carry a week or more of refills along with you. 

New on the market is the 10 liter reservoir, whose specifications are also shown in Table 3. Of this unit, the manufacturer says 

We introduced the L-10 at a recent trade show. We recognized the niche market for this smaller size. Our thoughts are to market this product for "Weekend" use, office use, traveling and the like. Because of its size it will be a good device for those folks who want be on the go. It can easily fit in cars of all sizes, even those in Europe which are smaller than those in the US. And because of the size, the weight comes in around 28 lbs. empty and 53 lbs. filled. We don't want to be confined to our houses so, take a portable and an L-10 and go. With as many liquid sites around the country and the world, there is sufficient coverage to fill and go as needed.
Table 3 
Small Liquid Reservoirs


Caire
L10
Caire
L20
DeVilbiss
20
NPB
C21
Capacity




Liquid (liters)
10.7
21.6
20.4
21

Gaseous (liters)
8,881
17,780
16,700
16,750

Liquid (lbs.)
26
52
49
49
Duration @ 2 Lpm (hrs.)
68
148
140
140
Weight (lbs.)




Empty
27
39
39
45

Full
53
91
88
94
Dimensions (in.)




Height
19.5
24.5
24.5
25

Diameter
12
14
14
14.25
Flow Rates (Lpm)
Off-6
Off to 6*
Off to 6
Off-6
Filling Duration (min.)
1.5-2.5
1.5-2.5
1.5-2.5
-
Filling Valve Location side/top
side/top
side/top
-
Operating Pressure (psi)
20
20
20
19.5
Evaporation (lbs./day)
1.5
1.5
1.5
1.9
For more information about smaller reservoirs, see the Caire and NPB websites.

Freezing Up

Liquid portables can freeze up after filling, particularly during humid weather. When they do freeze up, the flow of oxygen stops and remains stopped for 10 to 20 minutes. 

Liquid portables freeze up because extremely low temperatures around the fill port freezes any moisture close by and turn it into ice crystals. These ice crystals cling to the nearby parts on the portable making it too cold to perform normal operations. 

You can reduce episodes of this type by doing two things: 

  • Dry the fill ports of both the reservoir and portable with a towel before connecting them.
  •  
  • When filling is complete and the fill lever is closed, allow the portable to remain connected to the reservoir for about 20 seconds before disconnecting. If the two units cannot be separated easily, allow another l20 seconds before disconnecting. 

  • Should the valve of the portable continue to vent when disconnected, reconnect for 20 seconds.
If, after filling your liquid portable unit, oxygen stops flowing you should do the following: 
  • Find another source of oxygen to use for the 10 to 20 minutes it will take for the coils to warm and the oxygen to flow.
  • Reduce this recovery time by moving the portable to a place where it is warmer, but never near an open flame.
DO NOT touch the fill port of the reservoir or portable. Its temperature is cold enough to cause skin burns. 

IMPORTANT: 
The information here provided is for educational purposes only and it is not intended nor implied to be a substitute for professional medical advice. Always consult your own physician or healthcare provider with any questions you may have regarding a medical condition. 

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