CPAP titration by an auto-CPAP device based on snoring detection: a clinical trial and economic considerations.

This study aimed to assess the ability of an auto-nasal continuous positive airway pressure (nCPAP) device (REM + auto; NPBFD, Nancy, France) to predict the optimal constant nCPAP level. The apnoea/hypopnoea detection facility of the auto-nCPAP device was deliberately disabled and nasal mask pressure vibration detection was the only mode of pressure setting. The auto-nCPAP device was tested on 10 previously untreated patients with obstructive sleep apnoea during a single night, with ambulatory polysomnography performed in a conventional hospital room; the efficacy of the fixed pressure determined by the auto-nCPAP device was assessed by an ambulatory full polysomnography 2 weeks after the initiation of treatment at home. The fixed nCPAP pressure was effective (apnoea/hypopnoea and arousal indices <10 events x h(-1)) in all but two of the 10 patients studied. When the fixed nCPAP pressure was increased by 2 cmH2O in these two patients, sleep and respiration were normalized. Since only 12 ambulatory polysomnographic recordings were used to determine the effective nasal continuous positive airway pressure level, and as the device restored normal breathing and sleep in all 10 patients, it was concluded that this method of nasal continuous positive airway pressure titration may improve cost-effectiveness and reduce waiting lists in sleep laboratories.

Evaluation of an auto-nCPAP device based on snoring detection.

We evaluated an auto-nasal continuous positive airway pressure (nCPAP) prototype (MC+; SEFAM, Nancy, France) in which apnoea/hypopnoea detection was disabled and nasal mask pressure vibration detection was the only mode of pressure setting. The device was tested in 15 previously untreated obstructive sleep apnoea patients during a night with polysomnography. We observed that a single night of auto-nCPAP improved the apnoea/hypnoea index (AHI) (12 +/- 21 vs 51 +/- 31 disordered breathing events.h-1 of sleep (mean +/- SD)), the awakening-arousal index (13 +/- 20 vs 40 +/- 26 arousals.h-1 of sleep), and duration of slow wave sleep (102 +/- 49 vs 71 +/- 56 min) but not of rapid eye movement (REM) sleep (55 +/- 31 vs 64 +/- 38 min). Auto-nCPAP was effective (apnoea/hypopnoea and arousal indices < 10 events.h-1) in all but three patients. Auto-nCPAP was ineffective in one patient, whose obstructive respiratory events were not preceded by nasal mask pressure vibration detection, and in two patients who were quasi-permanent mouth breathers. Snoring detection may be effective in sleep apnoea syndrome with heavy snoring and without permanent mouth breathing, during the first night of nasal continuous positive airway pressure treatment.

[Environment and permanent cardiac pacing]. / Environnement et stimulation cardiaque définitive.

The increasing technological sophistication of cardiac pacemakers make them potentially more vulnerable to electrical interference. The clinical consequence are of variable importance depending on the type of pacemaker and the nature of the interference. Electrical interference is present in the domestic, industrial and, above all, the medical environment. Apart from controlling the sources of emission, prevention requires standards of protection for the casing and electronic circuitry. Patient education remains primordial.

Application of the micropipette technique to the measurement of cultured porcine aortic endothelial cell viscoelastic properties.

The viscoelastic deformation of porcine aortic endothelial cells grown under static culture conditions was measured using the micropipette technique. Experiments were conducted both for control cells (mechanically or trypsin detached from the substrate) and for cells in which cytoskeletal elements were disrupted by cytochalasin B or colchicine. The time course of the aspirated length into the pipette was measured after applying a stepwise increase in aspiration pressure. To analyze the data, a standard linear viscoelastic half-space model of the endothelial cell was used. The aspirated length was expressed as an exponential function of time. The actin microfilaments were found to be the major cytoskeletal component determining the viscoelastic response of endothelial cells grown in static culture.

The application of a homogeneous half-space model in the analysis of endothelial cell micropipette measurements.

Experimental studies have shown that endothelial cells which have been exposed to shear stress maintain a flattened and elongated shape after detachment. Their mechanical properties, which are studied using the micropipette experiments, are influenced by the level as well as the duration of the shear stress. In the present paper, we analyze these mechanical properties with the aid of two mathematical models suggested by the micropipette technique and by the geometry peculiar to these cells in their detached post-exposure state. The two models differ in their treatment of the contact zone between the cell and the micropipette. The main results are expressions for an effective Young's modulus for the cells, which are used in conjunction with the micropipette data to determine an effective Young's modulus for bovine endothelial cells, and to discuss the dependence of this modulus upon exposure to shear stress.