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| 2. |
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| 3. |
- Bergstrand, Sara, et al.
(författare)
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Blood flow measurements at different depths using photoplethysmography and laser Doppler techniques
- 2009
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Ingår i: Skin research and technology. - : Wiley-Blackwell. - 0909-752X .- 1600-0846. ; 15:2, s. 139-147
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Tidskriftsartikel (refereegranskat)abstract
- Background/purpose: This study has evaluated a multi-parametric system combining laser Doppler flowmetry and photoplethysmography in a single probe for the simultaneous measurement of blood flow at different depths in the tissue. This system will be used to facilitate the understanding of pressure ulcer formation and in the evaluation of pressure ulcer mattresses.Methods: The blood flow in the tissue over the sacrum was measured before, during and after loading with 37.5 mmHg, respectively, 50.0 mmHg. The evaluation of the system consisted of one clinical part, and the other part focusing on the technicalities of the probe prototype.Results: An increase in blood flow while loading was the most common response, but when the blood flow decreased during loading it was most affected at the skin surface and the blood flow responses may be different due to depths of measurement. Reactive hyperaemia may occur more frequently in the superficial layers of the tissue.Conclusion: The study showed that the new system is satisfactory for measuring tissue blood flow at different depths. The laser Doppler complements the photoplethysmography, and further development of the system into a thin flexible probe with the ability to measure a larger area is required.
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| 9. |
- Jönsson, Björn, 1951-, et al.
(författare)
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A new probe for ankle systolic pressure measurement using Photoplethysmography (PPG)
- 2005
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Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 0090-6964 .- 1573-9686. ; 33:2, s. 232-239
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Tidskriftsartikel (refereegranskat)abstract
- An automated method for ankle systolic pressure measurement, less operator dependent than the standard continuous wave (CW) Doppler technique, would imply an advantage both in patient measurements and in epidemiological studies. We present a new photoplethysmographic (PPG) probe that uses near-infrared light (880 nm) to detect pulsatory blood flow underneath the distal end of a standard pneumatic cuff. The probe is adapted to the anatomical conditions at the ankle, permitting recording of pressures in both ankle arteries separately. The validity of the equipment was tested with CW Doppler-derived systolic pressures and invasive blood pressure measurements for reference. In 20 healthy subjects, visual analysis of the PPG curves revealed a mean difference between CW Doppler and PPG measurements of –0.5 mmHg (SD 6.9). Corresponding results for the anterior and posterior tibial arteries separately were –1.8 mmHg (SD 6.2) and 0.9 mmHg (SD 7.3), respectively. A correct probe position was essential for the results. In direct recordings from the dorsalis pedis artery in 10 intensive care patients, PPG underestimated systolic pressure in the anterior tibial artery by 4.5 mmHg (SD 12.1). With further development, the PPG probe, integrated in the pneumatic cuff, may simplify measurements of ankle systolic pressures.
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| 10. |
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| 11. |
- Jönsson, Björn, 1951-, et al.
(författare)
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Automatic ankle pressure measurements using PPG in ankle-brachial pressure index determination
- 2005
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 30:4, s. 395-401
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveTo evaluate a new technique using a photoplethysmographic (PPG) probe for automatic ankle pressure measurements.DesignComparative study on two techniques for ankle pressure measurement.SettingUniversity hospital.MaterialThirty-five patients with leg arterial disease and eight healthy volunteers. Ankle-brachial indices (ABPI) were measured using conventional CW Doppler technique and PPG-based prototype equipment for the ankle pressure recordings.Chief outcome measuresABPIs calculated from CW Doppler and PPG ankle pressure measurements. The PPG signals were analysed both by visual judgement and by a software based, automatic algorithm.Main resultsThe mean difference between ABPIs calculated from CW Doppler recordings and PPG (visual analysis) was −0.01 (limits of agreement (±two standard deviations) +0.16 to −0.19). The correlation coefficient was 0.93. When the algorithm was used, the mean difference (CW Doppler−PPG) was 0.05 (limits of agreement 0.28 to −0.18, r=0.89).ConclusionsThe PPG method is a promising technique with an inherent potential for automatisation of the ankle pressure measurements, thereby reducing the observer-dependency in ABPI recordings.
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| 12. |
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| 13. |
- Laurent, Claes, 1958-, et al.
(författare)
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Non-invasive measurement of systolic blood pressure on the arm utilising photoplethysmography : development of the methodology
- 2005
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 43:1, s. 131-135
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 14. |
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| 15. |
- Naslund, J., et al.
(författare)
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Decreased pulsatile blood flow in the patella in patellofemoral pain syndrome
- 2007
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Ingår i: American Journal of Sports Medicine. - : SAGE Publications. - 0363-5465 .- 1552-3365. ; 35:10, s. 1668-1673
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Tidskriftsartikel (refereegranskat)abstract
- Background: Anterior knee pain without clinical and radiologic abnormalities has primarily been explained from a purely structural view. A recently proposed biologic and homeostatic explanation questions the malalignment theory. No objective measurement of the pathophysiology responsible for changes in local homeostasis has been presented. Hypothesis: Flexing the knee joint interferes with the perfusion of the patellar bone in patellofemoral pain syndrome. Study Design: Case control study, Level of evidence, 4. Methods: Pulsatile blood flow in the patella was measured continuously and noninvasively using photoplethysmography. Measurements were made with the patient in a resting position with knee flexion of 20°and after passive knee flexion to 90°. In total, 22 patients with patellofemoral pain syndrome were examined bilaterally, and 33 subjects with healthy knees served as controls. Results: The pulsatile blood flow in the patient group decreased after passive knee flexion from 20°to 90°(systematic change in position, or relative position [RP] = -0.32, 95% confidence interval for RP, -0.48 to -0.17), while the response in the control group showed no distinct pattern (RP = 0.17, 95% confidence interval for RP, -0.05 to 0.31). The difference between the groups was significant (P =.0002). The median change in patients was -26% (interquartile range, 37). Conclusions: Pulsatile patellar blood flow in patellofemoral pain syndrome patients is markedly reduced when the knee is being flexed, which supports the previous notion of an ischemic mechanism involved in the pathogenesis of this pain syndrome. © 2007 American Orthopaedic Society for Sports Medicine.
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| 16. |
- Naslund, J., et al.
(författare)
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Non-invasive continuous estimation of blood flow changes in human patellar bone
- 2006
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Ingår i: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 44:6, s. 501-509
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Tidskriftsartikel (refereegranskat)abstract
- A photoplethysmographic (PPG) technique to assess blood flow in bone tissue has been developed and tested. The signal detected by the PPG consists of a constant-level (DC) component - which is related to the relative vascularization of the tissue - and a pulsatile (AC) component - which is synchronous with the pumping action of the heart. The PPG probe was applied on the skin over the patella. The probe uses near-infrared (804 nm) and green (560 nm) light sources and the AC component of the PPG signals of the two wavelengths was used to monitor pulsatile blood flow in the patellar bone and the overlying skin, respectively. Twenty healthy subjects were studied and arterial occlusion resulted in elimination of PPG signals at both wavelengths, whereas occlusion of skin blood flow by local surface pressure eliminated only the PPG signal at 560 nm. In a parallel study on a physical model with a rigid tube we showed that the AC component of the PPG signal originates from pulsations of blood flow in a rigid structure and not necessarily from volume pulsations. We conclude that pulsatile blood flow in the patellar bone can be assessed with the present PPG technique. © International Federation for Medical and Biological Engineering 2006.
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| 17. |
- Nilsson, Lena, 1956-, et al.
(författare)
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Age and gender do not influence the ability to detect respiration by photoplethysmography
- 2006
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Ingår i: Journal of clinical monitoring and computing. - : Springer Science and Business Media LLC. - 1387-1307 .- 1573-2614. ; 20:6, s. 431-436
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Tidskriftsartikel (refereegranskat)abstract
- Objective The non-invasive technique photopl- ethysmography (PPG) can detect changes in blood volume and perfusion in a tissue. Respiration causes variations in the peripheral circulation, making it possible to monitor breaths using an optical sensor attached to the skin. The respiratory-synchronous part of the PPG signal (PPGr) has been used to monitor respiration during anaesthesia, and in postoperative and neonatal care. Studies addressing possible differences in PPGr signal characteristics depending on gender or age are lacking.Methods We studied three groups of 16 healthy subjects each during normal breathing; young males, old males and young females, and calculated the concordance between PPGr, derived from a reflection mode PPG sensor on the forearm, and a reference CO2 signal. The concordance was quantified by using a squared coherence analysis. Time delay between the two signals was calculated. In this process, we compared three different methods for calculating time delay.Results Coherence values ≥0.92 were seen for all three groups without any significant differences depending on age or gender (p = 0.67). Comparison between the three different methods for calculating time delay showed a correlation r = 0.93.Conclusions These results demonstrate clinically important information implying the possibility to register qualitative PPGr signals for respiration monitoring, regardless of age and gender.
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| 18. |
- Nilsson, Lena, et al.
(författare)
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Combined photoplethysmographic monitoring of respiration rate and pulse : A comparison between different measurement sites in spontaneously breathing subjects
- 2007
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 51:9, s. 1250-1257
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Tidskriftsartikel (refereegranskat)abstract
- Background: The non-invasive photoplethysmographic (PPG) signal reflects blood flow and volume in a tissue. The PPG signal shows variation synchronous with heartbeat (PPGc), as used in pulse oximetry, and variations synchronous with breathing (PPGr). PPGr has been used for non-invasive monitoring of respiration with promising results. Our aim was to investigate PPG signals recorded from different skin sites in order to find suitable locations for parallel monitoring of variations synchronous with heartbeat and breathing. Methods: PPG sensors were applied to the forearm, finger, forehead, wrist and shoulder on 48 awake healthy volunteers. From these sites, seven PPG signals were simultaneously recorded during normal spontaneous breathing over 10 min. Capnometry served as respiration and electrocardiogram (ECG) as pulse reference signals. PPG signals were compared with respect to power spectral content and squared coherence. Results: Forearm PPG measurement showed significantly higher power within the respiratory region of the power spectrum [median (quartile range) 42 (26)%], but significantly lower power within the cardiac region [9 (10)%] compared with the other skin sites. PPG finger measurement showed the opposite, in transmission mode, the power within the respiratory region was significantly lower [4 (10)%] and within the cardiac region significantly higher [45 (25)%] than the other sites. PPGc coherence values were generally high [>0.96 (0.08)], and PPGr coherence values lower [0.83 (0.35)-0.94 (0.17)]. Conclusion: Combined PPG respiration and pulse monitoring is possible, but there are significant differences between the respiratory and cardiac components of the PPG signal at different sites. © 2007 Acta Anaesthesiol Scand.
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| 21. |
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| 22. |
- Pettersson, Jonas, et al.
(författare)
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A Wireless PPG Sensor Applied Over the Radial Artery – A Pilot Study
- 2006
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Ingår i: E-Health - Proceedings of Med-e-Tel 2006. - : Luxexpo. ; , s. 199-202
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Konferensbidrag (refereegranskat)abstract
- Photoplethysmography (PPG) is a well known non-invasive technique in the medical field. It is mainly used for monitoring skin perfusion and oxygen saturation. PPG measures changes in intensity of light that has been emitted into the skin and reflected or transmitted towards a photo detector. There is no exact knowledge of the mechanisms behind the PPG signal but it has been suggested that the pulsatile component is related both to pulsatile volume changes due to varying lumen of the vessel and to red cell orientation during each cardiac cycle.A specially designed wireless PPG sensor has been developed for application over the radial artery to gain centrally related blood flow variables. A study was performed to assess the relationship between the PPG signal and several physiological parameters. Recordings were made using an arrangement of a Doppler ultrasound probe, a non-invasive blood pressure measuring device (Portapres), an impedance measuring device that records respiratory work and a wireless PPG measuring device attached over the radial artery. All signals were recorded simultaneously and analyzed afterwards.The measurements showed a close relationship between the recorded variables. The strongest correlation was found between pulsatile PPG and blood velocity (measured by Doppler ultrasound). This correlation was most obvious during hyperventilation. In this case there was also a strong correlation between PPG and blood pressure measured by Portapres. The recordings also showed that forced deep respiration could be observed both by PPG and Portapres.In conclusion;•the PPG signal may reflect blood pressure variations as well as a velocity related component in the radial artery•respiratory events may be observed in the radial artery using PPG•the wireless PPG sensor system is a new tool for monitoring centrally related physiological parameters but with limited batterylifetime as a drawback
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| 23. |
- Sandberg, Margareta, et al.
(författare)
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Different patterns of blood flow response in the trapezius muscle following needle stimulation (acupuncture) between healthy subjects and patients with fibromyalgia and work-related trapezius myalgia
- 2005
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Ingår i: European Journal of Pain. - : Wiley. - 1090-3801. ; 9:5, s. 497-510
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Tidskriftsartikel (refereegranskat)abstract
- Needle stimulation (acupuncture) has recently been shown to increase blood flow in the tibialis anterior muscle and overlying skin in healthy subjects (HS) and patients with fibromyalgia (FM). The aim of the present study was to examine the effect of needle stimulation on local blood flow in the trapezius muscle and overlying skin in HS and two groups of patients suffering from chronic pain in the trapezius muscle, i.e., FM and work-related trapezius myalgia (TM) patients. Two modes of needling, deep muscle stimulation (Deep) and subcutaneous needle insertion (SC), were performed at the upper part of the shoulder and blood flow was monitored for 60 min post-stimulation. Blood flow changes were measured non-invasively by using a new application of photoplethysmography. Increased blood flow in the trapezius muscle and overlying skin was found in all three groups following both Deep and SC. In HS, Deep was superior to SC in increasing skin and muscle blood flow, whereas in FM, SC was as effective as, or even more effective, than Deep. In the severely affected TM patients, no differences were found between the stimuli, and generally, a lesser blood flow response to the stimuli was found. At Deep, the muscle blood flow increase was significantly larger in HS, compared to the two patient groups. Positive correlations were found between muscle blood flow at Deep and pressure pain threshold in the trapezius muscle, neck movement and pain experienced at the stimulation, and negative correlations were found with spontaneous pain-related variables, symptom duration and age, pointing to less favorable results with worsening of symptoms, and to the importance of nociceptor activation in blood flow increase. It was hypothesized that the different patterns of muscle blood flow response to the needling may mirror a state of increased sympathetic activity and a generalized hypersensitivity in the patients. The intensity of stimulation should be taken into consideration when applying local needle stimulation (acupuncture) in order to increase the trapezius muscle blood flow in chronic pain conditions. (c) 2004 European Federation of Chapters of the International Association for the Study of Pain.
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| 24. |
- Sandberg, Margareta, et al.
(författare)
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Non-invasive monitoring of muscle blood perfusion by photoplethysmography: evaluation of a new application
- 2005
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Ingår i: Acta Physiol Scand. - 0001-6772 .- 1365-201X. ; 183:4, s. 335-43
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Tidskriftsartikel (refereegranskat)abstract
- AIM: To evaluate a specially developed photoplethysmographic (PPG) technique, using green and near-infrared light sources, for simultaneous non-invasive monitoring of skin and muscle perfusion. METHODS: Evaluation was based on assessments of changes in blood perfusion to various provocations, such as post-exercise hyperaemia and hyperaemia following the application of liniment. The deep penetrating feature of PPG was investigated by measurement of optical radiation inside the muscle. Simultaneous measurements using ultrasound Doppler and the new PPG application were performed to elucidate differences between the two methods. Specific problems related to the influence of skin temperature on blood flow were highlightened, as well. RESULTS: Following static and dynamic contractions an immediate increase in muscle perfusion was shown, without increase in skin perfusion. Liniment application to the skin induced a rapid increase in skin perfusion, but not in muscle. Both similarities and differences in blood flow measured by Ultrasound Doppler and PPG were demonstrated. The radiant power measured inside the muscle, by use of an optical fibre, showed that the near-infrared light penetrates down to the vascular depth inside the muscle. CONCLUSIONS: The results of this study indicate the potentiality of the method for non-invasive measurement of local muscle perfusion, although some considerations still have to be accounted for, such as influence of temperature on blood perfusion.
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| 27. |
- Uhlin, Fredrik, et al.
(författare)
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Complementary parameter for dialysis monitoring based on UV absorbance
- 2009
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Ingår i: Hemodialysis International. - : Wiley. - 1492-7535 .- 1542-4758. ; 13:4, s. 492-497
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Tidskriftsartikel (refereegranskat)abstract
- An optical on-line monitoring system aimed at the estimation of dialysis dose has been tested clinically. The natural logarithmic slope is used to calculate Kt/V(urea) from ultraviolet (UV)-absorbance measurements. Errors in the calculation of Kt/V(urea) may appear due to changes in blood and dialysate flow or due to disturbances when the slope is used to estimate dialysis dose. This study introduces a new parameter for dialysis monitoring that may be used as a complementary parameter, the area under UV-absorbance curve (AUCa), to reflect a total solute removal during dialysis. The aim was to investigate the relationship between this new dialysis on-line monitoring parameter, AUCa, and the total removal of a few solutes. Fifteen patients were monitored during hemodialysis using UV absorbance at the wavelength of 297 nm. All spent dialysate passed through a flow cuvette in a spectrophotometer and then further to a collection tank where solute concentrations in the entire spent dialysate were determined. The AUCa at 297 nm was compared with the total amount of removed solute in the tank (reference method). The result shows strong correlations between AUCa and the total removal of urea, urate, creatinine, and phosphate during a given treatment and less strong correlation in all 15 patients together. A first indication of a new, possible, complementary parameter in hemodialysis treatment is presented, the AUCa, prospected to estimate solute removal.
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| 28. |
- Uhlin, Fredrik, et al.
(författare)
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Dialysis dose (Kt/V) and clearance variation sensitivity using measurement of ultraviolet-absorbance (on-line), blood urea, dialysate urea and ionic dialysance
- 2006
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Ingår i: Nephrology Dialysis Transplantation. - : Oxford University Press (OUP). - 0931-0509 .- 1460-2385. ; 21:8, s. 2225-2231
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Tidskriftsartikel (refereegranskat)abstract
- Background. An on-line monitoring system for dialysis dose calculations could make it possible to provide an adequate dialysis dose that is consistently given to haemodialysis (HD) patients. The aim of this study was to compare dialysis dose (Kt/V) using four different methods and their sensitiveness to a reduction in clearance. Methods. Six patients were monitored on-line with ultraviolet (UV)-absorbance at a wavelength of 297 nm in three consecutive dialysis sessions during 1 week. During the last treatment, the clearance was reduced by 25% by decreasing the blood flow. For the determination of UV-absorbance, a spectrophotometer was connected to the fluid outlet of the dialysis machine with all spent dialysate passing through a flow cuvette. The equilibrated Kt/V (eKt/V) estimated by UV-absorbance was compared with eKt/V from the ionic dialysance method using the on-line clearance monitor (OCM) and the appurtenant software dose-calculation tool DCTool (Fresenius Medical Care, Germany), eKt/V calculated from the dialysate-urea slope and with eKt/V from pre- and post-dialysis blood-urea samples as reference. Results. The study demonstrates that the sensitiveness to clearance reduction is similar in the four methods compared for eKt/V. When the different methods were compared, the mean eKt/V of UV-absorbance was 1.21 ± 0.20, blood 1.30 ± 0.21, dialysate 1.32 ± 0.21 and OCM (using the DCTool) 1.31 ± 0.21. The standard deviation was of the same magnitude. Conclusion. The UV-method gives a similar response to clearance reduction compared with the other methods when comparing dialysis dose. The high sampling rate by continuous monitoring of UV-absorbance allows evaluation of the clearance process during dialysis and gives immediate feedback to on-line adjustments.
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| 29. |
- Uhlin, Fredrik, et al.
(författare)
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Estimating total urea removal and protein catabolic rate by monitoring UV absorbance in spent dialysate
- 2005
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Ingår i: Nephrology Dialysis Transplantation. - : Oxford University Press (OUP). - 0931-0509 .- 1460-2385. ; 20:11, s. 2458-2464
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Tidskriftsartikel (refereegranskat)abstract
- Background. Dialysate-based, on-line measurements of Kt/V and protein catabolic rate (PCR) in dialysis patients have been considered more accurate compared with measurements on the blood side during dialysis. The primary aim of this study was to compare total removed urea (TRU) and PCR, normalized to body weight (nPCRw), obtained by three dialysate-based methods: (i) on-line ultraviolet (UV) absorbance of the spent dialysate; (ii) total dialysate collection (TDC), as reference method; and (iii) Urea Monitor 1000 (UM) from Baxter Healthcare Corp. Methods. We studied 10 uraemic patients on chronic, thrice-weekly haemodialysis. We made absorption measurements (UV radiation) on-line with a spectrophotometer connected to the fluid outlet of the dialysis machine, with all spent dialysate passing through an optical cuvette for single-wavelength measurements. UV absorbance measurements were compared with TDC and the UM. Results. nPCRw obtained with UV absorbance was 0.82±0.17, that from TDC 0.81±0.18, and that measured by UM 0.87±0.18, which was significantly higher than the results of the other methods. The difference between nPCRw calculated by TDC and by UM was –0.05±0.06, showing a slightly lower SD than the difference between nPCRw by TDC and UV absorbance, –0.01±0.07. Conclusion. The study demonstrates that TRU, and consequently PCR, can be estimated by on-line measurement of the UV absorption in the spent dialysate.
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| 30. |
- Uhlin, Fredrik, 1965-
(författare)
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Haemodialysis Treatment Monitored On-line by Ultra Violet Absorbance
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes and evaluates an optical method utilizing ultra violet (UV) absorbance for on-line monitoring of haemodialysis treatment. Increased efficiency of haemodialysis treatment is considered to correlate to decreased morbidity and mortality when urea clearance (Kt/V) is elevated. However, further improvements have not been achieved at a higher Kt/V. The mortally rate in the haemodialysis population is still high (27% in Sweden).Urea as the clinical marker is under discussion, partly due to urea being non-toxic, but also that the uraemic syndrom is the result of a cumulative retention of innumerable involved compounds.On-line monitoring systems based on urea determination for improved dialysis efficiency have been suggested and developed in different settings over the last two decades, but have not achieved worldwide utilisation as routine clinical equipment. This thesis demonstrates that the UV-technique utilising 280, 285 and 297 nm is capable of estimating dialysis efficiency in therms of Kt/V, nutritional status in terms of protein catabolic rate (PCR), with the same characteristics as existing methods. One novel finding using UV-absorbance with high sampling rates is the on-line visualisation of the clearance process for following variations in clearance caused by clinical events and disturbances as well as during and after adjustments. The fact that the UV-absorbance technique does not measure urea directly but has high correlation to several other both UV-absorbing and not-absorbing solutes makes it suitable to reflect a more overall solute retention process. Finally, a new efficiency parameter based on the calculation of the area under UV- curve (clearance curve), is suggested to reflect the total removal of some solutes.In summary the UV-technique has the potential to be an additional tool to evaluate improvements of dialysis efficiency, which may result in decreased morbidity, longer life span and enhanced quality of life for the haemodialysis patients.
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| 31. |
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| 32. |
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| 33. |
- Uhlin, Fredrik, et al.
(författare)
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Ultra violet absorbance on-line measurement utilized to monitor clinical events during haemodialysis
- 2006
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Ingår i: Journal of Renal Care. - 1755-6678 .- 1755-6686. ; 32:3, s. 141-146
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Tidskriftsartikel (refereegranskat)abstract
- Background: On-line monitoring systems of the spent dialysate, used to estimate dialysis dose, have been developed with different instrumentation during the last two decades. The routine use of an on-line monitoring system has been suggested to provide to give an adequate dialysis dose to the haemodialysis (HD) patients. The aim of this study was to show that monitoring the spent dialysate using UV-absorbance may bring new information about the clearance process. Methods: 108 HD treatments distributed among 16 clinical stable patients were monitored on-line using ultra violet (UV) absorbance. For the measurement of UV-absorbance a spectrophotometer was connected to the fluid outlet of the dialysis machine with all spent dialysate passing through a flow cuvette. The UV-absorbance curves were examined in combination with the recorded observations of events that occurred during the studied treatments.Results: The study demonstrates that UV-absorbance visualizes different kind of events such as hypotension, conductivity alarms, restricted flow in artery needle blood pump stop that often occur during dialysis treatment.Conclusion: An on-line UV-monitoring system with a high sampling rate makes it possibility to identify variations in dialysis clearance of different origin and gives feedback after performing interventions during a dialysis session
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