The functional disability experienced by patients with severe pulmonary disease relates both to their physiological impairment and their inability to adapt and maintain a normal lifestyle. As patients develop a medical need for supplemental oxygen, breathlessness and lack of energy are compounded by the increased demand of carrying oxygen equipment.
Oxygen conserving devices have been introduced as a means of making oxygen therapy more efficient, more portable, and less intrusive [1,2]. In addition, hypoxemia can be prevented more readily in those patients with high oxygen flow requirements by using oxygen conserving devices, such as reservoir cannulas and transtracheal catheters. Escalating costs and reduced reimbursement have also fostered the availability of these systems.
This review will compare traditional, continuous flow oxygen delivery by nasal cannula with a variety of oxygen conserving devices. The indications for long-term supplemental oxygen, the use of oxygen in hypercapnic patients, and issues regarding oxygen therapy during air travel are discussed separately. (See "Long-term supplemental oxygen therapy" and "Use of oxygen in patients with hypercapnia" and "Traveling with oxygen aboard commercial air carriers".)
CONTINUOUS FLOW NASAL CANNULA
Continuous flow nasal cannula oxygen delivery via nasal prongs is the standard against which all developments or improvements should be compared . The nasal cannula is universal and generally well accepted by patients and the public alike, and its effectiveness in meeting the oxygen needs of the stable chronic lung disease patient is essentially unquestioned. However, it is inefficient, as only a small percentage of the oxygen delivered to the nose actually reaches the alveoli.
Oxygen flowing through the standard nasal cannula is nearly 100 percent pure. However, the patient actually receives a blend of pure oxygen and room air. In fact, a much larger volume of inspired atmospheric air, containing 20.9 percent oxygen, is entrained with the oxygen . The resultant inspiratory oxygen concentrations via standard flow settings are approximated in the figure (figure 1).