Compliance with long-term oxygen therapy by concentrator.

Controlled oxygen therapy has been developed to treat chronic respiratory failure in patients with hypoxic obstructive airways disease (COAD). In two studies published in the early 1980's long term oxygen therapy (LTOT) improved survival and reduced clinical deterioration over a three year period in such patients (1, 2]. The reduction in mortality was proportionate to the number of hours per day of oxygen therapy. The minimum daily time for clinical benefit was 15 hours with greater benefit for longer periods. It is important, therefore, that patients comply fully with prescribed therapy. A number of studies are now reviewed to assess pa· tient compliance under different regimens. In the MRC trial patients were prescribed oxygen therapy for at least 15 hours per day [1]. They were visited every 6 weeks at home and all patients bad two monthly clinic appointments. The weighing of cylinders after use (in Sheffield), recording the time of use of concentrators (in Birmingham), and random visits to patients and assessment of liquid oxygen usage (in Edinburgh) all suggested that most patients took at least the prescribed amount of oxygen. In the NOIT trial patients were prescribed either nocturnal (12 h/day) or continuous (24 h/day) oxygen (2]. For the first 6 months of the study patients received weekly home visits by a nurse practitioner and were seen each month in an out-patient clinic. After the first 6 months they were visited at home at least once a month and examined in an out-patient clinic at least every 3 months. The patient and family members were required to keep written records of oxygen use. According to oxygen concentrator time-checks, nocturnal oxygen therapy patients averaged 12.0:t2.5 (so) h/day but continuous (24 h) oxygen therapy patients averaged 17.7:t4.8 h/day. According to patients' logs 56% of continuous oxygen therapy patients used oxygen for 19 or more hours per day. This was considered to be good compliance with therapy [3]. The investigators believed compliance was good because patients were followed very closely and found it easy to believe that oxygen was beneficial to them. Ev ANS et al. [ 4] reported their clinical experience with oxygen concentrators. In the first year, 14 concentrators were allocated to patients with cor pulmonale associated with COAD. Every three months technical staff visited the patient's home to read the hidden clock, change air filters, perform minor servicing and to ensure the concentration of oxygen delivered was at least 90%. Patients were seen at three monthly intervals in out-patients for clinical assessment. Patients used the machines for a mean of 13.3 hours