Oxygen Therapy
Liquid Oxygen
Although Liquid Oxygen has been provided in the UK for over ten years, it is only recently that this mode of supply has become generally available. Liquid Oxygen has been shown to be of benefit to patients who, although requiring Oxygen therapy, are otherwise potentially mobile and active.
The package provided comprises a reservoir unit in which to store the liquid, plus a small portable flask. The flask is transfilled from the reservoir to provide portable (or "ambulatory") Oxygen outside the home environment. Because the portable unit can be filled quickly, and can be "topped up", it provides an instant source of ambulatory Oxygen as and when required, without the need for recourse to a third party.
The equipment
Oxygen exists in a liquid state at temperatures below -180 degrees centigrade. For this reason it is supplied in a vacuum insulated flask, otherwise known as a Dewar, or reservoir unit. A typical reservoir unit will be approx. 33" tall and 15" in diameter. (83 cm x 36 cm). The weight when full is 124 lbs, or 55.8 kg. For this reason, a roller base is provided to facilitate the movement of the unit. The portable unit measures approx 14.5" x 6" x6" (36 cm x 15cm x 15 cm) and weighs 8.7 lbs (3.9 kg) when full.
As a single unit of liquid converts to 860 units of gaseous Oxygen, this system provides the facility to store large volumes of product in a relatively compact container. The reservoir, for example holds 30 litres of liquid which provides over 25,000 litres of gas!
The reservoir and portable units operate on the same basic principle:Oxygen in liquid form is extracted from the container, and passed through a system of tubes which utilize heat from the surroundings to convert it to gas at ambient temperature. No electronic or electrical components are utilized in this process, hence the equipment is totally independent of any power supply. The purity of Oxygen supplied by this means is identical to that provided through a hospital pipeline: i.e. over 99%.
Prescribing Liquid Oxygen ("Lox")
The prescribing process is similar to that of a Concentrator. In addition to the standard concentrator request form an accompanying letter is required stating the reasons why liquid is preferred to other modalities. Lox patients typically require a high flow rate, are highly mobile, or have other special circumstances. Usually, patients assessed for Lox will already be using a concentrator in their home; the liquid is then utilized for Ambulatory purposes only.
The prescription and letter will specify the flow rate required, and the hours per day for which it is anticipated the Lox will be in use and the reason why Lox is required. It will be forwarded to Health Facilities Scotland, clearly marked as being a requirement for Liquid Oxygen.
Upon receipt of the details, Dolby will install the equipment (subject to a risk assessment), train the user/carer in its use, and then agree subsequent deliveries. Deliveries are facilitated on a full for empty basis at pre-determined intervals. The operator will uplift the empty reservoir unit from the premises and provide a full one in its place.
Risks associated with Liquid Oxygen
The usual precautions apply as with any mode of Oxygen delivery. However, the following are specific to liquid Oxygen:
- Cold Burns: Certain external components of the reservoir and the portable unit can become very cold during the transfilling process. Users are advised to avoid contact with these components until such time as they have warmed to ambient temperature.
- Leakage from either unit is minimal, however a safety valve is incorporated into both the reservoir and the portable to prevent excessive build up of pressure.
- In addition, it is not permissible to install Lox in premises above ground floor level. This is due to the weight of the reservoir (Manual handling issues), and the volume of gas which potentially could be released. (Oxygen is denser than air and thus will sink to the lowest level available).