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Optical reflection spectra of the cartilage/bone interface from hip joints of cows were studied. When comparing to ultrasonic measurement, it was found that cartilage thickness could be extracted using optical reflectance spectroscopy. For thicker cartilage layers, a high reflection for the wavelengths 400-600 nm was seen, and for thinner cartilage layers, the characteristic spectra of blood and bone dominated. The optical reflectance spectra may be used to characterise cartilage, and specifically cartilage thickness, in connection with in situ diagnosis or autologous chondrocyte implantation (ACI).

Heart- and respiration rate related signals were measured simultanously using reflection mode of photoplethysmography (PPG) through a fiber optic sensor. The sensor was attached to the ear-lobe. Both heart- and respiration related variations in blood perfusion could be observed after filtering the PE signal. The frequency content of the signal was observed by calculating the power spectral density.

A laser Doppler blood flow instrument for pulp blood flow measurements, designed in response to clinical demands, is discussed. The instrument is designed in two separate units. One includes the power supply, the indicators and control facilities. In the second unit, the miniaturized optical electronics part is housed in a pistol-shaped case which can be held against the tooth during the measurements. The use of a diode laser and a specially designed fiber-optic system has improved the clinical applicability of the method. >

Laser Doppler flowmetry was used to study the microvascular blood flow of the human gingiva. Power spectral density analysis of the Doppler signals indicated differences in the vascular structure/flow patterns in four tissue types that were studied. Cigarette smoking elevated the gingival blood flow during a 5-min period after which the flow came back to baseline values. The study indicates that the laser Doppler method is a convenient and noninvasive method for dynamic blood flow measurements in the gingiva. >

The authors have developed two new sensor principles for heart- and respiratory rate monitoring. One sensor (Hjartrud) is based on skin microcirculatory fluctuations in blood flow, synchronous with the heart- and respiratory rates. A second sensor (Optovent) is based on condensation of humidity from the airways at the end of an optical fibre, the properties of which change with condensation of water. Both sensor principles have been evaluated. The accuracy's are comparable with sensors more established in clinical work. By using optical fibres one can obtain electromagnetic noise immunity of great value in MR-monitoring and during surgical diathermy. The Hjartrud sensor utilises digital signal processing techniques to extract and separate the heart- and respiratory signals from noise. Both instruments are in an industrial preproduction evaluation phase.

A new respiratory monitoring device has been evaluated in the postoperative care unit at Linkoping University Hospital, Sweden. The purpose of the study was to compare the new photoplethysmographic device to more established techniques. Continuous data acquisition from 16 patients (each 1 h long), were performed. The respiratory signals from the photoplethysmographic device were compared to impedance plethysmographic signals. Conclusions from the evaluation are that the performance of the new device is comparable with the impedance method, and in some cases even more reliable.