Two months follow up of auto-CPAP treatment in patients with obstructive sleep apnoea.

BACKGROUND: Continuous positive airway pressure (CPAP) with fixed mask pressure is the current standard treatment for obstructive sleep apnoea (OSA). Auto-CPAP devices apply at any time the minimally required pressure to normalise breathing and may improve patient comfort and compliance. We present an open descriptive study of auto-CPAP treatment at home in patients previously managed with conventional CPAP. METHODS: Fifteen patients with obstructive sleep apnoea (OSA), previously treated for at least one year with standard CPAP, were followed prospectively for a two month period on auto-CPAP. Outcome measures were both subjective evaluation by the patients and objective (polysomnographic) data obtained at one and two months of follow up. RESULTS: The Epworth sleepiness score did not change significantly between baseline and follow up after one and two months and no systematic changes in CPAP related side effects were reported. Compared with the baseline polysomnographic values without treatment, a significant improvement in both respiratory and sleep parameters was observed during auto-CPAP. These results were not significantly different from those obtained with standard CPAP. A significant correlation was found between the effective CPAP pressure (Peff) and the amount of time spent below Peff during auto-CPAP treatment (r = 0.6, p = 0.01). CONCLUSION: Long term auto-CPAP treatment in these patients with severe OSA appears to provide comparable efficacy to that of standard CPAP treatment.

Functional residual capacity in healthy preschool children.

The purpose of this study was to evaluate the feasibility of routine functional residual capacity (FRC) measurements in healthy preschool children aged 2.7-6.4 yrs. Furthermore, accuracy and reproducibility were investigated and normal values were collected. A mass-produced closed-circuit helium dilution device (rolling seal) was used. Selection of the 113 healthy children (from the 571 measured) was based on an extensive personal and family history questionnaire and on clinical examination before measurements were performed. With three successive attempts it was possible to achieve at least two reproducible measurements in 73% of the children (repeatability coefficient 95.3 mL). The main problems were leakage at the corner of the mouth and irregular breathing pattern. The mean time to perform a measurement was 113 s. Mean FRC was significantly higher in boys than in girls: 778 versus 739 mL for a body length of 110 cm (p<0.05). FRC correlated with height (H) (r=0.69), weight (W) (r=0.56), age (A) (r=0.62) and all three combined (r=0.70): FRC = -534.89 + 1.84 x W (kg) + 10.07 x H (cm) + 2.51 x A (months). When a power or exponential function was used to describe FRC as a function of height, the results were not superior to the linear regression (r=0.69): FRC (mL) = -766.2 + 13.8 x H (cm) (r=0.69) or FRC (L) = 0.620 x H (m)(2.03) (r=0.69) or FRC (mL)= 99.5 x e(0.018xH (cm)) (r=0.69). Among these, we recommend the power function because it will better fit broader height ranges. Reliable functional residual capacity measurements can be routinely performed in preschool children with a mass-produced device. Reference values were collected for children 95-125 cm in height.

Hypoxic ventilatory response and carotid endarterectomy.

Carotid endarterectomy is reported to abolish hypoxic ventilatory responsiveness. This effect is thought to be due to denervation or destruction of the carotid bodies by surgical exposure. The technique of carotid endarterectomy, however, does not require the sacrifice of these structures. Six patients who had bilateral carotid endarterectomy with careful preservation of the carotid bodies and their innervation were studied pre- and postoperatively with respect to hypoxic ventilatory responsiveness and the latter was taken as a measure of chemoreceptor activity. Five patients showed a weak or absent response to hypoxia before surgery. In four of these there was a significant increase in reactivity after the procedure (p less than 0.01 in one case, p less than 0.05 in three others). The fifth patient had a non-significant increase and the sixth had a normal response before and after surgery. Thus, loss of chemoreceptor function after bilateral carotid endarterectomy was not observed in this group of patients with preserved carotid bodies. The low ventilatory hypoxic sensitivity before surgery and its occasional increase after removal of the plaque suggests that atherosclerosis might well impair the microscopic blood supply to the carotid bodies, inducing sensor dysfunction but this hypothesis requires further investigation.

Effect of oxygen administration on the breathing pattern during haemodialysis in man.

During haemodialysis (HD), allowing important CO2- unloading, an irregular breathing pattern (BP) is frequently observed. This has been attributed to a decrease in central chemoreceptor firing, with a greater contribution of the peripheral chemoreceptors in the chemical drive to breathe. To provide further evidence for these findings we studied five patients with end-stage renal failure in chronic HD. They underwent HD with a cuprophane membrane and acetate-containing dialysate. Ventilation was measured continuously using respiratory inductance plethysmography. Oxygen was administered for 30 min, using nasal cannulae, at a rate of 6 l.min-1, starting 130 min after the onset of the HD. Blood gases were taken from the arterial line. During the initial air breathing, arterial oxygen tension (PaO2) decreased from 12.3 +/- 1.2 kPa (92.8 +/- 8.9 mmHg) at 0 min to 10.5 +/- 1.8 kPa (79.0 +/- 13.3 mmHg) at 2 h (p less than 0.01) (mean +/- SD). All patients showed irregular breathing with 1.4 +/- 0.6 apnoeas exceeding 10 s per 10 min after 2 h. Minute ventilation decreased from 6.8 +/- 1.9 l.min-1 at 0 min to 5.4 +/- 1.3 l.min-1 at 2 h (p less than 0.05). During the O2 breathing, PaO2 increased to 26.3 +/- 4.0 kPa (197.8 +/- 30.3 mmHg) (p less than 0.001), while arterial carbon dioxide tension (PaCO2) remained unchanged. The irregular BP previously observed vanished completely. The mean number of apnoeas exceeding 10 s per 10 min decreased to 0.08 +/- 0.12 during O2 (p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)