Comparison of three auto-adjusting positive pressure devices in patients with sleep apnoea

Auto-adjustable continuous positive airway pressure (APAP) devices are an emerging treatment alternative to fixed-pressure continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea syndrome. They have been engineered to automatically adjust the pressure to the optimal level on a continuous basis. However, not all APAP technologies use the same algorithm. Three different APAP devices (Autoset Spirit, Breas PV 10i and RemStar Auto) were compared in a randomised crossover trial in patients already established on fixed-pressure CPAP therapy. The outcome measures were compliance, quality of life and side-effects. Twenty-seven middle-aged patients (25 male) previously diagnosed with severe obstructive sleep apnoea syndrome (median (interquartile range) apnoea/hypopnoea index 48 (29-76)), established on CPAP therapy for >3 yrs, were randomised to each APAP device for 4 weeks. Mean pressure and patient compliance were significantly lower on the Breas PV 10i than on the other APAP devices. The devices were similar in terms of quality of life, daytime sleepiness and upper airway side-effects, but patients evaluated them significantly differently in terms of device features, sleep quality and pressure comfort, with the Breas PV 10i being the least popular. Auto-adjustable positive airway pressure devices differ in pressure delivery and patient compliance in obstructive sleep apnoea syndrome patients.

Subclinical anaemia of chronic disease in adult patients with cystic fibrosis

Patients with chronic hypoxaemia develop secondary polycythaemia that improves oxygen-carrying capacity. Therefore, normal haemoglobin and haematocrit values in the presence of chronic arterial hypoxaemia in cystic fibrosis constitute 'relative anaemia'. We sought to determine the cause of this relative anaemia in patients with cystic fibrosis. We studied haematological indices and oxygen saturation in healthy volunteers (n=17) and in adult patients with cystic fibrosis (n=15). Patients with cystic fibrosis had lower resting arterial oxygen saturation when compared with normal volunteers (P<0.0001), and exercise led to a greater reduction in arterial oxygen saturation (P<0.0001). However, haemoglobin and haematocrit values in patients with cystic fibrosis did not significantly differ from normal volunteers. Serum iron (P=0.002), transferrin (P=0.02), and total iron-binding capacity (P=0.01) were lower in patients with cystic fibrosis. There were no significant differences in serum ferritin, percentage iron saturation, serum erythropoietin or red cell volume between the groups. The data presented demonstrate a characteristic picture of anaemia of chronic disease in adult patients with cystic fibrosis, except for normal haemoglobin and haematocrit values. Normal haemoglobin and haematocrit values in patients with cystic fibrosis appear to represent a combination of the effects of arterial hypoxaemia promoting polycythaemia, counterbalanced by chronic inflammation promoting anaemia of chronic disease.