Non-invasive measurement of systolic blood pressure on the arm utilising photoplethysmography: development of the methodology.

Photoplethysmography (PPG) can be used to measure systolic blood pressure at the brachial artery. With a specially designed probe, positioned in the most distal position beneath a pressure cuff on the upper arm, this is possible. The distance between the light source (880 nm) and the photodetector was 20 mm. A test was performed on neuro-intensive care patients by determining blood pressure from the PPG curves, and, when it was compared with systolic blood pressure obtained from inserted indwelling arterial catheters, a correlation factor of r = 0.95 was achieved. The difference between blood pressure obtained using PPG and invasive blood pressure measurement was 3.9 +/- 9.1 mmHg (mean +/- SD), n = 19. The depth to the brachial artery was 13.9 +/- 4.1 mm (mean +/- SD), n = 18. A digital PPG system utilising pulsating light was also developed.

Does a magnetic blanket induce changes in muscular blood flow, skin temperature and muscular tension in horses?

REASONS FOR PERFORMING STUDY: Static magnetic blankets are often claimed to induce increases in blood flow, reduce muscle tension and tenderness, and be beneficial in both prevention and treatment of musculoskeletal injuries in horses. However, there are no studies that confirm alleged beneficial effects of magnets on muscles of the back in healthy horses. OBJECTIVES: To investigate whether static magnets sewn into a blanket affect back muscle blood flow, skin temperature, mechanical nociceptive threshold (MNT) and behaviour in healthy horses. STUDY DESIGN: Prospective, randomised, blinded, placebo-controlled crossover study. METHODS: The following outcome measurements of the back of 10 healthy horses were performed; blood flow by photoplethysmography, skin temperature by use of thermistors in conjunction with digital infrared thermography, and MNTs by algometry. The horses' behaviour was filmed during the procedure and scored on an ethogram. Measurements were performed repeatedly for a 30 min baseline period. Thereafter a blanket with active, static magnets (900 gauss) or placebo magnets was placed on the horse and measurements were performed for a 60 min treatment period and a 30 min post treatment period. The study procedure was repeated on the consecutive day, when the horse received the alternative treatment. RESULTS: Blood flow in muscle, skin temperatures, MNTs and behavioural traits did not differ between active and placebo magnetic blankets. Skin temperature increased similarly during both active and placebo blanket treatment. CONCLUSIONS: In healthy horses, magnetic blankets did not induce additional significant effects on muscle blood flow, skin temperature, MNTs and behaviour when compared with nonmagnetic blankets.

Conization as treatment of carcinoma in situ of the uterine cervix.

A series of 343 consecutive cases with the preoperative diagnosis of carcinoma in situ of the uterine cervix treated by cervical conization is presented. In 93% of these patients cervical cytology returned to normal. The follow-up period ranged from 1 to 5 years. There was significantly greater chance for an apparent cure in cases in which histologic evaluation indicated free margins of resection (98%) than in those where the margins were involved by the neoplastic process (70%). Colposcopic evaluation to determine the site for punch biopsies and adequate resection margins could greatly enhance the success of therapeutic conization. The urgent need for conservative management of cervical intraepithelial neoplasia because of its predominance among young women is discussed.

Optical non-invasive technique for vessel imaging: I. Experimental results.

This paper investigates some prerequisites for vessel imaging based on diffuse reflectance measurements in order to develop an optical non-invasive method for the imaging and monitoring of vessels. The method utilizes near-infrared (NIR) radiation (890 nm) from a light emitting diode. The light is guided into the tissue via an optical fibre (diameter 1.0 mm). The backscattered light is collected by an optical fibre of the same type and detected by an optical power meter. The fibres are moved over the skin in two directions with the aid of two motors operated by a microcomputer. Spatially resolved reflectance at the skin surface could be presented as a vessel-map in a colour-coded form on a computer screen. Experimental results indicate that the vessel imaging facility depends upon source-detector separation, relative position and vessel depth, and does not depend essentially on the radiant power from the light source. It is shown that, by a proper choice of probe parameters, one can improve the vessel identification ability. After vessel imaging the technique can potentially be used to monitor several physiological parameters on a selected vascular bed or to distinguish between injured and healthy tissue by monitoring local blood flow, oxygen saturation and the recirculation, pre- and post-operatively.

Optical non-invasive technique for vessel imaging: II. A simplified photon diffusion analysis.

The purpose of this paper is to explain theoretically the origin of previously presented experimental results by an optical non-invasive method using NIR for imaging blood vessels based on a specific combination of several physical parameters. The theoretical model is based on the diffusion approximation derived from the transport theory deep in a bulk tissue. An analytical solution was obtained describing photon behaviour under certain conditions during vessel identification. The modelled results indicate that the vessel identification facility depends upon source-detector separation and vessel depth, and does not depend essentially on the radiant power from the light source. The solution offers a relatively simple theoretical explanation of the experimental results and can be applied to several other clinical applications using similar technical solutions.

Aspiration cytology of salivary gland tumors: diagnostic experience from six years of routine laboratory work.

Fine-needle aspiration cytology has been used as a routine diagnostic instrument in patients with salivary gland lesions during 1966-1972. A retrospective analysis of the primary cytologic reports correlated with the revised final diagnoses in 461 patients where a pathologic report is available, shows exact agreement in 63 percent, good and not misleading agreement in a further 18 percent, while false reports were initially given in 8 percent, and unsatisfactory specimens were obtained in 11 percent of the patients. On revision of the false reports it is found that with the present experience acquired over several years these can be reduced to under 5 percent. This analysis has also given indications upon which types of specimens are likely to cause diagnostic difficulties.

On-line monitoring of solutes in dialysate using wavelength-dependent absorption of ultraviolet radiation.

The aim of the study was to assess the wavelength dependence of the UV absorbance during monitoring of different compounds in the dialysate. UV absorbance was determined by using a double-beam spectrophotometer on dialysate samples taken at pre-determined times during dialysis, over a wavelength range of 180-380 nm. Concentrations of several removed substances, such as urea, creatinine, uric acid, phosphate and beta2-microglobulin, were determined in the blood and in the spent dialysate samples using standard laboratory techniques. Millimolar extinction coefficients, for urea, creatinine, monosodium phosphate and uric acid were determined during laboratory bench experiments. The correlation between UV absorbance and substances both in the dialysate and in the blood was calculated at all wavelengths. A time-dependent UV absorbance was determined on the collected dialysate samples from a single dialysis session over a wavelength range of 200-330 nm. The highest contribution from observed compounds relative to the mean value of the absorbance was found around 300 nm and was approximately 70%. The main contribution to the total absorbance from uric acid was confirmed at this wavelength. The highest correlation for uric acid, creatinine and urea was obtained at wavelengths from 280 nm to 320 nm, both in the spent dialysate and in the blood. The wavelength region with the highest correlation for phosphate and beta2-microglobulin, with a suitable UV-absorbance dynamic range, was from 300 to 330 nm. In the wavelength range of 220-270 nm the highest absorbance sensitivity for the observed substances was obtained. A suitable wavelength range for instrumental design seems to be around 290-330 nm. The relatively high correlation between UV absorbance and the substances in the spent dialysate and in the blood indicates that the UV-absorbance technique can estimate the removal of several retained solutes known to accumulate in dialysis patients.

Photoplethysmography. Part 2. Influence of light source wavelength.

When the microvascular blood perfusion in human skin is measured by photoplethysmography (PPG), infra-red light (800-960 nm) is normally used as the light source. The PPG signal, which consists of a pulsatile (AC) and a slowly fluctuating (DC) component, was studied at different optical wavelengths utilising optical fibres for guiding the light to and from the skin surface. Finger and forearm skin was examined and high and low skin blood perfusion was brought about by local water-induced temperature provocation. The analysis of the measurement results provided evidence that the use of shorter wavelengths in PPG (AC) for monitoring skin perfusion changes could be applicable. The use of different optical wavelengths also raises the possibility of recording perfusing changes at different depths in the superficial tissue. The sweat water content in stratum corneum of human skin will probably determine the total amount of reflected and backscattered radiation reaching the photodetector. This is important when the skin perfusion is changed by alterations in the environmental temperature conditions activating the sweat glands in tissue. Temperature-dependent optical characteristics of blood-free skin tissue may explain the limited ability of the DC component of PPG to monitor skin perfusion changes.

Photoplethysmography. Part 1. Comparison with laser Doppler flowmetry.

Photoplethysmography (PPG) and laser Doppler flowmetry (LDF) were compared and evaluated. The comparison was accomplished considering differences in physical principles and geometrical and optical conditions. Changes in human skin perfusion were induced by cold and hot water provocation on limited areas of the finger and the forearm. The results showed that LDF and PPG, using red light at 630-660 nm and a commercial PPG probe, were in general equally sensitive in detecting a blood perfusion increase following a skin temperature elevation. However, we also found that PPG occasionally showed an inverse response to a skin temperature elevation, especially in finger skin. Furthermore, the study indicated that laser light is unsuitable as a light source in PPG using optical fibres of small diameter and with no fibre separation. It was also found that the physical dimensions of the probe (including the light source and photodetector) play an important role in determining the measuring volume and the quality of the signal.

Monitoring of respiratory and heart rates using a fibre-optic sensor.

A new method, which uses a fibre-optic probe to monitor respiratory and heart rates simultaneously, has been developed and evaluated. The results provide evidence that it is possible to monitor respiratory and heart rates using the reflection mode of photoplethysmography (PPG). The fibre-optic probe makes it possible to monitor from different sites on the patient, and the method is convenient to use. In addition, the probe is X-ray transparent, insensitive to electromagnetic interference (e.g. during MRI investigation) and may be made very light and small. Therefore the method is suitable for the observation of both adults and neonates, in hospitals as well as in other environments.

Accuracy of pulse oximetry at various haematocrits and during haemolysis in an in vitro model.

In situations in which it may be impossible and/or unethical to evaluate pulse oximetry in humans, an in vitro model with circulating blood may be a necessity. The main objective was to develop such an in vitro model and, in this model, validate the pulse oximetry technique at various haematocrit levels. The pulsating character of arterial blood flow in a tubing system was simulated by using a specially constructed pressure-regulated roller pump. The tubing system was designed to minimise damage to red blood cells. The pulse oximeter readings (SpO2) were compared with oxygen saturation analyses by a haemoximeter (SaO2). The pulse oximetry readings were recorded at various haematocrit levels and during haemolysis in the SaO2 range 60-100 per cent. At a haematocrit level of 41-44 per cent, there was no correlation between SaO2 and SpO2 readings. After diluting the blood with normal saline to a haematocrit of 10-11 per cent, a good correlation between SaO2 and SpO2 was found. Following haemolysis, the agreement between SaO2 and SpO2 was further improved. Using the developed in vitro model, the results indicate that the accuracy of a pulse oximeter may be dependent on the haematocrit level.

Specimen fixation in urinary cytology.

Several solutions were evaluated with regard to the preservation and preparation of urine for cytologic evaluation, using a Millipore filtration method. An adequate quantitative yield and good cellular morphology were obtained with formaldehyde-based mixtures as well as with several commercially available solutions. A pure transport medium inhibiting bacterial growth and enzymatic activity preserved cell samples equally well.

Cytologic diagnosis of bancroftian filariasis in a nonendemic area.

Parasitic infections are common in the developing countries, but the cytologic diagnosis of such infections is infrequent or rare. This paper presents four cases of filariasis caused by Wuchereria bancrofti diagnosed by cytologic examination and discusses some unusual observations. The finding of microfilariae in pleural fluid in the absence of the classic symptoms and signs of tropical pulmonary eosinophilia is highlighted. In two patients, nocturnal microfilaremia could not be demonstrated despite Nuclepore filtration, thus suggesting the possible merits of cytology in the primary diagnosis of a filarial infection. Even the diethylcarbamazine provocative test failed to elicit a peripheral microfilaremia in one patient, further emphasizing the importance of cytology as a diagnostic method in amicrofilaremic infections. Attention is drawn to the need for a high index of suspicion on the part of the cytologist in the identification of parasitic organisms in material from high-risk groups to achieve an early diagnosis of such infections and the prompt institution of appropriate chemotherapy. This may obviate the more serious pathologic changes of advanced disease, especially the disfigurement of chronic and late filariasis.

On-line monitoring of solutes in dialysate using absorption of ultraviolet radiation: technique description.

PURPOSE: The aim of this work was to describe a new optical method for monitoring solutes in a spent dialysate using absorption of UV radiation. METHOD: The method utilises UV-absorbance determined in the spent dialysate using a spectrophotometrical set-up. Measurements were performed both on collected dialysate samples and on-line. During on-line monitoring, a spectrophotometer was connected to the fluid outlet of the dialysis machine, with all spent dialysate passing through a specially-designed cuvette for optical single-wavelength measurements. The concentrations of several substances of various molecular sizes, electrical charge, transport mechanism, etc. were determined in the dialysate and in the blood using standard laboratory techniques. The correlation coefficient between UV-absorbance of the spent dialysate and concentration of the substances in the spent dialysate and in the blood was calculated from data based on the collected samples. RESULTS: The obtained on-line UV-absorbance curve demonstrates the possibility to follow a single hemodialysis session continuously and to monitor deviations in the dialysator performance using UV-absorbance. The experimental results indicate a very good correlation between UV-absorbance and several small waste solutes removed such as urea, creatinine and uric acid in the spent dialysate and in the blood for every individual treatment at a fixed wavelength of 285 nm. Moreover, a good correlation between the UV-absorbance and substances like potassium, phosphate and beta2-microglobulin was obtained. The lowest correlation was achieved for sodium, calcium, glucose, vitamin B12 and albumin. CONCLUSIONS: A technique for on-line monitoring of solutes in the spent dialysate utilising the UV-absorbance was developed. On-line monitoring during a single hemodialysis session exploiting UV-absorbance represents a possibility to follow a single hemodialysis session continuously and monitor deviations in dialysis efficiency (e.g. changes in blood flow and clearance). The UV-absorbance correlates well to the concentration of several solutes known to accumulate in dialysis patients indicating that the technique can be used to estimate the removal of retained substances.

A technique based on laser Doppler flowmetry and photoplethysmography for simultaneously monitoring blood flow at different tissue depths.

The aim of this study was to validate a non-invasive optical probe for simultaneous blood flow measurement at different vascular depths combining three photoplethysmography (PPG) channels and laser Doppler flowmeter (LDF). Wavelengths of the PPG were near-infrared 810 nm with source-to-detector separation of 10 and 25 mm, and green 560 nm with source-to-detector separation of 4 mm. The probe is intended for clinical studies of pressure ulcer aetiology. The probe was placed over the trapezius muscle, and depths from the skin to the trapezius muscle were measured using ultrasound and varied between 3.8 and 23 mm in the 11 subjects included. A provocation procedure inducing a local enhancement of blood flow in the trapezius muscle was used. Blood flows at rest and post-exercise were compared. It can be concluded that this probe is useful as a tool for discriminating between blood flows at different vascular tissue depths. The vascular depths reached for the different channels in this study were at least 23 mm for the near-infrared PPG channel (source-to-detector separation 25 mm), 10-15 mm for the near-infrared PPG channel (separation 10 mm), and shallower than 4 mm for both the green PPG channel (separation 4 mm) and LDF.