Towards automated sleep state estimation using a Holter-oximeter.

Single-channel ECG and finger photoplethysmogram were used to estimate sleep states in obstructive sleep apnea patients. Overnight Holter-oximeter recordings from 14 subjects with suspected sleep apnea were analysed. Parameters including the RR interval, photoplethysmogram amplitude and rise time, and pulse arrival time were characterised and a Hidden Markov Model classifier used to identify Wake, REM and Sleep states. An overall accuracy of 77% and Cohen's kappa of 0.54 was achieved, establishing a baseline level of usefulness for sleep state estimation using a Holter-oximeter. Autonomic arousals detected using pulse arrival time also appeared to be strongly correlated with Epworth Sleepiness Scale scores.

Continuous blood pressure monitoring using ECG and finger photoplethysmogram.

Pulse arrival time and the amplitude of the finger photoplethysmogram were used to track blood pressure continuously over 10-minute intervals. The measures were recorded with a holter-oximeter from a sample of 8 young, healthy human subjects in the supine and standing positions. Results indicate that, with individual calibration, systolic and diastolic blood pressure can be estimated with an average error of +/-6 and +/-4 mmHg respectively. Using pulse arrival time in combination with the amplitude of the finger photoplethysmogram gave better results than using any one alone, with PPG amplitude appearing to be more robust.

Pulse transit time-derived respiratory parameters and their variability across sleep stages.

We considered the capability of pulse transit time (PTT) to provide respiratory information in obstructive sleep apnea (OSA) patients. PTT-derived respiratory frequency was quite well correlated with that derived from inductance plethysmography, with amplitude slightly less so. The PTT-derived respiratory estimates were also used to distinguish sleep stage. In some subjects, statistically significant differences in respiratory parameters were observed between Wake, REM, and Stage 2 sleep, but this effect was highly subject dependent.

Osteocutaneous radial forearm free flaps. The necessity of internal fixation of the donor-site defect to prevent pathological fracture.

BACKGROUND: Osteocutaneous radial forearm free flaps have fallen from favor due to pathological fractures of the radius. The purposes of this study were to propose a means to decrease the rate of pathological fracture by prophylactic fixation of the donor-site defect and to evaluate this technique biomechanically. METHODS: Two groups of ten matched pairs of fresh-frozen cadaveric radii were harvested. In Group 1, an eight-centimeter length of radius comprising 50 percent of the cross-sectional area of the bone was removed to simulate an osteocutaneous radial forearm donor-site defect. This defect was created in one member of each pair, with the other bone in the pair left intact. In Group 2, both members of the ten matched pairs of radii had identical defects created as previously described. However, one radius in each pair had a twelve-hole, 3.5-millimeter dynamic compression plate placed across the segmental defect. In each group, five matched pairs were tested to failure in torsion and five matched pairs were tested to failure in four-point bending. RESULTS: In Group 1, the intact radius was a mean of 5.7 times stronger in torsion and 4.2 times stronger in four-point bending than the radius with the segmental resection. In Group 2, the radius that was ostectomized and fixed with a plate was a mean of 4.0 times stronger in torsion and 2.7 times stronger in four-point bending than the ostectomized radius. CONCLUSIONS: Removal of an eight-centimeter segment from the radius dramatically decreased both torsion and bending strength. Application of a plate over the defect in the radius significantly restored the strength of the radius (p = 0.01).

Acute leukemia in Malaysian children.

A review of acute childhood leukemia in the University Hospital, Kuala Lumpur reveals no significant differences in either the epidemiological or clinical features between Malaysian and Caucasian children. BCG does not appear to have conferred any protection against the occurrence of leukemia. With the introduction of total therapy 4 of 10 patients with good prognostic features and 3 of 15 patients with poor prognostic features have survived 3 years. Prognosis appears to correlate with adopted clinical criteria.