| 1. |
- Cordtz, Joakim, et al.
(author)
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Central venous oxygen saturation and thoracic admittance during dialysis: New approaches to hemodynamic monitoring
- 2008
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In: Hemodialysis International. - : Wiley. - 1542-4758 .- 1492-7535. ; 12:3, s. 369-377
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Journal article (peer-reviewed)abstract
- Intradialytic hypotension (IDH) is one of the most important short-term complications to hemodialysis (HD). Inadequate cardiac filling due to a reduction in the central blood volume is believed to be a major etiological factor. The aim of this study was to evaluate whether these pathophysiologic events are reflected in the central venous oxygen saturation (ScO2) and thoracic admittance (TA) during dialysis. Twenty ambulatory HD patients, 11 hypotension prone (HP) and 9 hypotension resistant, with central vascular access, were monitored during 3 HD sessions each. ScO2, TA, finger blood pressure (BP), and relative change in blood volume (Delta BV) were measured and sampled continuously. The relative TA decrease and Delta BV were both largest in the HP group (p < 0.05 for both), whereas ScO2 decreased only in HP patients (p < 0.001). Baseline TA was lower in the HP group (p < 0.01). Changes in ScO2 and TA correlated much closer than did changes in ScO2 and Delta BV (r=0.43 and 0.18, respectively). Our results suggest that an intradialytic decrease in cardiac output, as reflected by a fall in ScO2, is a common feature to HD patients prone to IDH. In patients using a central vascular access, ScO2 and TA measurements may be more specific to the pathophysiologic events preceding IDH than Delta BV-the current standard monitoring method.
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| 2. |
- Flodgren, Erik, et al.
(author)
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GPR40 is expressed in glucagon producing cells and affects glucagon secretion.
- 2007
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In: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 354:1, s. 240-245
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Journal article (peer-reviewed)abstract
- The free fatty acid receptor, GPR40, has been coupled with insulin secretion via its expression in pancreatic beta-cells. However, the role of GPR40 in the release of glucagon has not been studied and previous attempts to identify the receptor in alpha-cells have been unfruitful. Using double-staining for glucagon and GPR40 expression, we demonstrate that the two are expressed in the same cells in the periphery of mouse islets. In-R1-G9 hamster glucagonoma cells respond dose-dependently to linoleic acid stimulation by elevated phosphatidyl inositol hydrolysis and glucagon release and the cells become increasingly responsive to fatty acid stimulation when overexpressing GPR40. Isolated mouse islets also secrete glucagon in response to linoleic acid, a response that was abolished by antisense treatment against GPR40. This study demonstrates that GPR40 is present and active in pancreatic alpha-cells and puts further emphasis on the importance of this nutrient sensing receptor in islet function. (c) 2006 Elsevier Inc. All rights reserved.
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| 3. |
- Holm, Anders, et al.
(author)
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The GPER1 Agonist G-1 Attenuates Endothelial Cell Proliferation by Inhibiting DNA Synthesis and Accumulating Cells in the S and G2 Phases of the Cell Cycle.
- 2011
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In: Journal of Vascular Research. - : S. Karger AG. - 1423-0135 .- 1018-1172. ; 48:4, s. 327-335
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Journal article (peer-reviewed)abstract
- G protein-coupled receptor 30 (GPR30) or G protein-coupled estrogen receptor 1 (GPER1) is expressed in the vasculature, but the importance of vascular GPER1 remains to be clarified. Here we investigate effects of the GPER1 agonist G-1 on endothelial cell proliferation using mouse microvascular endothelial bEnd.3 cells. The bEnd.3 cells express mRNA for GPER1. The bEnd.3 cells expressed both ERα and ERβ immunoreactivities. Treatment with G-1 reduced DNA synthesis and cell number with IC(50) values of about 2 μM. GPER1 siRNA prevented G-1-induced attenuation of DNA synthesis. G-1 accumulated cells in S and G2 phases of the cell cycle, suggesting that G-1 blocks transition between G2 and M. G-1 had no effect on DNA synthesis in COS-7 cells only weakly expressing GPER1 mRNA. 17β-Estradiol had no effect on DNA synthesis in physiological concentrations (nM). The ER blocker ICI182780 reduced DNA synthesis with similar potency as G-1. Treatment with the ERK/MAP kinase inhibitor PD98059 had no effect on G-1-induced attenuation of DNA synthesis. G-1- induced antiproliferation was observed not only in bEnd.3 cells but also in human umbilical vein endothelial cells and HMEC-1 endothelial cells. We conclude that the GPER1 agonist G-1 attenuates endothelial cell proliferation via inhibition of DNA synthesis and by accumulation of cells in S and G2.
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| 4. |
- Holmer, Mattias
(creator_code:cre_t)
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Detecting blood path disruption in extracorporeal blood processing
- 2015
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Patent (other academic/artistic)abstract
- A device monitors a blood path from a blood vessel access of a human subject through an extracorporeal blood processing apparatus and back to the blood vessel access. A pumping device in the blood path is operable to pump blood through the blood path from the blood withdrawal device to the blood return device. The monitoring device obtains pressure data from a pressure sensor arranged upstream of the pumping device in the blood path, and processes the pressure data for detection of a disruption of the blood path downstream of the pumping device, e.g. caused by VND (Venous Needle Dislodgement). The disruption is detected by evaluating presence/absence of cross-talk pulses at the pressure sensor, where the cross-talk pulses originate from one or more pulse generators in the extracorporeal blood processing apparatus and have propagated on a propagation path in a direction downstream of the pumping device through the blood return device, the blood vessel access and the blood withdrawal device to the pressure sensor.
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| 5. |
- Holmer, Mattias, et al.
(author)
-
Detection of Needle Dislodgement Using Extracorporeal Pressure Signals : A Feasibility Study
- 2020
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In: ASAIO Journal. - 1538-943X. ; 66:4, s. 454-462
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Journal article (peer-reviewed)abstract
- Venous needle dislodgement (VND) during dialysis is a rarely occurring adverse event, which becomes life-threatening if not handled promptly. Because the standard venous pressure alarm, implemented in most dialysis machines, has low sensitivity, a novel approach using extracted cardiac information to detect needle dislodgement is proposed. Four features are extracted from the arterial and venous pressure signals of the dialysis machine, characterizing the mean venous pressure, the venous cardiac pulse pressure, the time delay, and the correlation between the two pressure signals. The features serve as input to a support vector machine (SVM), which determines whether dislodgement has occurred. The SVM is first trained on a set of laboratory data, and then tested on another set of laboratory data as well as on a small data set from clinical hemodialysis sessions. The results show that dislodgement can be detected after 12-17 s, corresponding to 24-143 ml blood loss. The standard venous pressure alarm used in clinical routine only detects 50% of the VNDs, whereas the novel method detects all VNDs and has a false alarm rate of 0.12 per hour, provided that the amplitude of the extracted cardiac pressure signal exceeds 1 mmHg. The results are promising; however, the method needs to be tested on a larger set of clinical data to better establish its performance.
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| 6. |
- Holmer, Mattias, et al.
(author)
-
Detection of ventricular premature beats based on the pressure signals of a hemodialysis machine
- 2018
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In: Medical Engineering and Physics. - : Elsevier BV. - 1350-4533. ; 51, s. 49-55
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Journal article (peer-reviewed)abstract
- Monitoring of ventricular premature beats (VPBs), being abundant in hemodialysis patients, can provide information on cardiovascular instability and electrolyte imbalance. In this paper, we describe a method for VPB detection which explores the signals acquired from the arterial and the venous pressure sensors, located in the extracorporeal blood circuit of a hemodialysis machine. The pressure signals are mainly composed of a pump component and a cardiac component. The cardiac component, severely overshadowed by the pump component, is estimated from the pressure signals using an earlier described iterative method. A set of simple features is extracted, and linear discriminant analysis is performed to classify beats as either normal or ventricular premature. Performance is evaluated on signals from nine hemodialysis treatments, using leave-one-out crossvalidation. The simultaneously recorded and annotated photoplethysmographic signal serves as the reference signal, with a total of 149,686 normal beats and 3574 VPBs. The results show that VPBs can be reliably detected, quantified by a Youden's J statistic of 0.9, for average cardiac pulse pressures exceeding 1 mmHg; for lower pressures, the J statistic drops to 0.55. It is concluded that the cardiac pressure signal is suitable for VPB detection, provided that the average cardiac pulse pressure exceeds 1 mmHg.
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| 7. |
- Holmer, Mattias, et al.
(author)
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Determining Heart Activity Present in the Pressure Sensors of a Dialysis Machine
- 2013
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In: Computing in Cardiology. - 2325-8861. ; , s. 217-220
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Conference paper (peer-reviewed)abstract
- Determination of heart status during dialysis can im- prove patient monitoring. Pressure sensors in the dialysis machine measures the heart pulses that propagates in the body and enter the extracorporeal blood circuit. A peri- staltic blood pump, located in the same circuit, introduces strong periodic pressure pulses that interfere with the much weaker cardiac component. These signal characteristics make the extraction of the heart activity challenging. In the present study, we explore the possibility to extract and analyze the cardiac component using simulated data. The accuracy of the timing of each heartbeat is analyzed. Ad- ditionally, the heart component is extracted from patient pressure recordings, and compared to the heart rate com- puted from a photoplethysmogram. The results show that heart timings can be accurately determined using the pres- sure sensors of a dialysis machine.
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| 8. |
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| 9. |
- Holmer, Mattias, et al.
(author)
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Extracting a Cardiac Signal From the Extracorporeal Pressure Sensors of a Hemodialysis Machine
- 2015
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In: IEEE Transactions on Biomedical Engineering. - 1558-2531. ; 62:5, s. 1305-1315
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Journal article (peer-reviewed)abstract
- Although patients undergoing hemodialysis treatment often suffer from cardiovascular disease, monitoring of cardiac rhythm is not performed on a routine basis. Without requiring any extra sensor, this study proposes a method for extracting a cardiac signal from the built-in extracorporeal venous pressure sensor of the hemodialysis machine. The extraction is challenged by the fact that the cardiac component is much weaker than the pressure component caused by the peristaltic blood pump. To further complicate the extraction problem, the cardiac component is difficult to separate when the pump and heart rates coincide. The proposed method estimates a cardiac signal by subtracting an iteratively refined blood pump model signal from the signal measured at the extracorporeal venous pressure sensor. The method was developed based on simulated pressure signals, and evaluated on clinical pressure signals acquired during hemodialysis treatment. The heart rate estimated from the clinical pressure signal was compared to that derived from a photoplethysmographic reference signal, resulting in a difference of 0.07 +/- 0.84 beats/min. The accuracy of the heartbeat occurrence times was studied for different strengths of the cardiac component, using both clinical and simulated signals. The results suggest that the accuracy is sufficient for analysis of heart rate and certain arrhythmias.
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| 10. |
- Holmer, Mattias, et al.
(author)
-
Heart Rate Estimation from Dual Pressure Sensors of a Dialysis Machine
- 2015
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In: 2015 Computing in Cardiology Conference (CinC). - 2325-8861. ; 42, s. 29-32
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Conference paper (peer-reviewed)abstract
- Dialysis patients often suffer from cardiovascular dis- eases, motivating the use of continuous monitoring of car- diac activity in clinical routine. Cardiac pressure pulses propagate through the vascular system and enter the ex- tracorporeal blood circuit of a dialysis machine, where the pulses are captured by pressure sensors. The cardiac pulses are obscured by the much stronger pressure pulses originating from the peristaltic blood pump. We have pre- viously shown that a cardiac signal can be extracted from the venous pressure signal. However, that method has been found to perform less well at very low cardiac pressure pulse amplitudes. In the present study, we propose a novel method which addresses this issue by using the signals from both the arterial and the venous pressure sensors. The method is compared to the previous method on clini- cal data using a photoplethysmogram as reference. The re- sults suggests that heart rate can be estimated more accu- rately from pressure signals with lower cardiac signal am- plitude when both arterial and venous pressure are used, compared to when only the venous signal is used.
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| 11. |
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| 12. |
- Holmer, Mattias, et al.
(author)
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On-line Heart Rate Monitoring Using the Extra-corporeal Pressure Sensors of a Dialysis Machine
- 2012
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In: Biomedical engineering – 2012 : proceedings of international conference. - 2029-3380.
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Conference paper (peer-reviewed)abstract
- Heart rate can be extracted from the extracorporeal venous pressure signal of a dialysis machine. The results are of comparable accuracy and reliability to the ones obtained by the PPG reference signal from a pulse oximeter. Difficulties that occur during heart rate estimation were determined, and some can be overcome by a slight adjustment of blood flow rate. The described techniques, after being implemented into the dialysis machines, would help to improve current hemodialysis safety throughout the treatment by on-line monitoring of the cardiac activity.
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| 13. |
- Olde, Bo
(creator_code:cre_t)
-
Filtering of a time-dependent pressure signal
- 2015
-
Patent (other academic/artistic)abstract
- A device removes first pulses in a pressure signal of a pressure sensor which is arranged in a fluid containing system to detect the first pulses, which originate from a first pulse generator, and second pulses, which originate from a second pulse generator. The first pulse generator is known to operate in a sequence of pulse cycles, each pulse cycle resulting in at least one first pulse. The device repetitively obtains a current data sample, calculates corresponding a reference value and subtracts the reference value from the current data sample. The reference value is calculated as a function of other data sample(s) in the same pressure signal.; These data sample(s) may be either cycle-synchronized so as to have a corresponding location in one or more other pulse cycles (e.g. in a preceding pulse cycle) as the current data sample, or be located in proximity to the current data sample. The fluid containing system may include an extracorporeal blood flow circuit, e.g. as part of a dialysis machine, and a cardiovascular system of a human patient.
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| 14. |
- Sandberg, Frida, et al.
(author)
-
Estimation of Respiratory Information from the Built-In Pressure Sensors of a Dialysis Machine
- 2014
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In: [Host publication title missing]. - 0276-6574. ; 41, s. 853-856
-
Conference paper (peer-reviewed)abstract
- The purpose of the present study is to determine the feasibility of estimating respiratory information from the built-in pressure sensors of a dialysis machine. The study database consists of simultaneous recordings of pressure signals and capnographic signals from 6 patients during 7 hemodialysis treatment sessions. Respiration rates were estimated using respiratory induced variations in the beat- to-beat interval series of the cardiac component of the pressure signal and respiratory induced baseline varia- tions in the pressure signal, respectively. The estimated respiration rates were compared to a reference respira- tion rate determined from the capnograhpic signal. The root-mean-square error of the estimated respiration rate from the baseline variations of the pressure signal was 2.10 breaths/min; the corresponding error of the estimated res- piration rate from the beat-to-beat interval series of the cardiac component was 4.95 breaths/min. The results sug- gest that it is possible to estimate respiratory information from the pressure sensors.
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| 15. |
- Sandberg, Frida, et al.
(author)
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Monitoring respiration using the pressure sensors in a dialysis machine
- 2019
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In: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 40:2
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Journal article (peer-reviewed)abstract
- OBJECTIVE: Although respiratory problems are common among patients with end-stage renal disease, respiration is not continuously monitored during dialysis. The purpose of the present study is to investigate the feasibility of monitoring respiration using the pressure sensors of the dialysis machine. APPROACH: Respiration induces variations in the blood pressure that propagates to the extracorporeal circuit of the dialysis machine. However, the magnitude of these variations are very small compared to pressure variations induced by the dialysis machine. We propose a new method, which involves adaptive template subtraction and peak conditioned spectral averaging, to estimate respiration rate from the pressure sensor signals. Using this method, an estimate of the respiration rate is obtained every 5th second provided that the signal quality is sufficient. The method is evaluated for continuous monitoring of respiration rate in nine dialysis treatment sessions. MAIN RESULTS: The median absolute deviation between the estimated respiration rate from the pressure sensor signals and a reference capnography recording was 0.02 Hz (1.3 breaths per min). SIGNIFICANCE: Our results suggest that continuous monitoring of respiration using the pressure sensors of the dialysis machine is feasible. The main advantage with such monitoring is that no additional sensors are required which may cause patient discomfort.
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| 16. |
- Solem, Kristian, et al.
(author)
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Prediction of Intradialytic Hypotension Using Photoplethysmography
- 2010
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In: IEEE Transactions on Biomedical Engineering. - 1558-2531. ; 57:7, s. 1611-1619
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Journal article (peer-reviewed)abstract
- Intradialytic hypotension is the most common acute complication during conventional hemodialysis treatment. Prediction of such events is highly desirable in clinical routine for prevention. This paper presents a novel prediction method of acute symptomatic hypotension in which the photoplethysmographic signal is analyzed with respect to changes in amplitude, reflecting vasoconstriction, and cardiac output. The method is based on a statistical model in which the noise is assumed to have Laplacian amplitude distribution. The performance is evaluated on 11 hypotension-prone patients who underwent hemodialysis treatment, resulting in seven events with acute symptomatic hypotension and 17 without. The photoplethysmographic signal was continuously acquired during treatment as was information on blood pressure and oxygen saturation. Using leave-one-out cross validation, the proposed method predicted six out of seven hypotensive events, while producing 1 false prediction out of 17 possible. The performance was achieved when the prediction threshold was chosen to be in the range 57%-65% of the photoplethysmographic envelope at treatment onset.
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