Heart rate increment: an electrocardiological approach for the early detection of obstructive sleep apnoea/hypopnoea syndrome.

The prevalence of OSAHS (obstructive sleep apnoea/hypopnoea syndrome) is high in developed countries and it is estimated that the vast majority of patients remain undiagnosed. On the basis of physiological evidence, we evaluated the frequency component of HRI (heart rate increment) as a simple and inexpensive screening tool for OSAHS detection in a first group of patients (group 1) and validated their discriminant capacity in a second group (group 2). The predictive accuracy of hourly %VLFI (frequency-domain HRI variable obtained from nocturnal ECG Holter monitoring) was analysed by comparison with an hour-by-hour respiratory disturbances index assessed by complete polysomnography in 28 consecutive clinically suspected OSAHS patients for group 1 and in 35 patients for group 2.

Validation of a two-axis accelerometer for monitoring patient activity during blood pressure or ECG holter monitoring.

Objectives: The aim of the study was to evaluate the efficiency of a position/activity monitoring system based on a dual-axis accelerometer strapped to the subject's thigh and a position sensor located within a monitor placed on the subject's belt.

Methods: Twenty-six subjects wearing two monitors (one accelerometer on each thigh) were submitted to various activities and positions under the control of an observer. An analysis of each tracing was performed both manually by a technician and automatically by dedicated software before being compared with the information gathered during the study.

Slow waves in circular muscle of porcine ileum: structural and electrophysiological studies.

The structural and functional bases of pacemaking (slow waves) in porcine ileal circular muscle were studied. The myenteric plexus contained two, structurally distinct types of interstitial cells of Cajal (ICC) interconnected by gap junctions and connected by close contacts to muscle layers. At the deep muscular plexus, ICC were present, not regularly close to nerve axons or in gap junction contact with one another or outer circular muscle, which had many gap junctions.

Effect of different calcium channel blockers on inhibitory junction potentials and slow waves in porcine ileum.

The effect of several calcium channel blockers was evaluated: (i) on spontaneous electrical and mechanical activities and (ii) on the response to electrical field stimulation. The study was carried out on whole-thickness preparation of porcine ileum. Glass microelectrodes were used to record membrane potential from smooth muscle cells.

Non-adrenergic, non-cholinergic inhibitory junction potential in rat colonic circular muscle is partly sensitive to omega-conotoxin GVIA and resistant to L-, P- or Q-type calcium channel blockers.

The effects of several Ca2+ channel blockers were evaluated on inhibitory junction potential (IJP) evoked in rat colonic circular muscle by electrical field stimulation (EFS). Glass microelecrodes were used to record membrane potential of smooth muscle cells. IJPs were tetrodotoxin-sensitive (1 microM) and disappeared in Ca(2+)-free solution.

Analysis of electric field stimulation of single cardiac muscle cells.

Electrical stimulation of cardiac cells by imposed extracellular electric fields results in a transmembrane potential which is highly nonuniform, with one end of the cell depolarized and the other end hyperpolarized along the field direction. To date, the implications of the close proximity of oppositely polarized membranes on excitability have not been explored. In this work we compare the biophysical basis for field stimulation of cells at rest with that for intracellular current injection, using three Luo-Rudy type membrane patches coupled together as a lumped model to represent the cell membrane.