Long-term oxygen therapy: advances and perspectives in technical devices.

Since the early beginnings of long-term oxygen therapy, by means of cylinders of compressed oxygen and their subsequent replacement with oxygen concentrators, most technical advances have been steadily focused on improving the facilities for continuous ambulatory oxygen therapy. Largely for this purpose, two different systems have been developed. 1) Oxygen concentrators in combination with portable cylinders for patients requiring oxygen at home and during short-term outdoor activities. If connected to an oxygen-conserving device, the duration of the ambulatory administration can be increased substantially. To improve mobility, a new generation of lightweight cylinders can nowadays be provided be several suppliers, thus; the weight of the portable systems can be reduced down to 2.1 kg. 2) Liquid oxygen is still the most convenient system for patients requiring continuous oxygen at home as well as during extensive daily outdoor activities. Liquid oxygen administration, however, is handicapped by its high costs, mainly due to logistical expenditure. Conserving devices are capable of lowering substantially the consumption and costs of gaseous and liquid oxygen. The following conserving techniques have proved to be efficient: reservoir cannulas, demand oxygen-pulse devices, and transtracheal catheters. The transtracheal route additionally improves physical ability and prolongs survival, suggested to be a consequence of unloading the work of breathing. Looking to future perspectives, there is ongoing progress in the technical improvement of concentrators. A very promising product is a new kind of concentrator which can be used to refill small portable cylinders at home. This system may be a real and probably less expensive alternative to liquid oxygen. In conclusion, all future efforts should be directed at improving the facilities for providing continuous ambulatory oxygen therapy, the superior concept for pulmonary rehabilitation in patients with chronic respiratory insufficiency.