Pressure Monitoring Research Articles

ОЦІНКА ЗМІН ФУНКЦІОНАЛЬНОГО СТАНУ СЕРЦЕВОСУДИННОЇ СИСТЕМИ У ЛІКАРІВ-ХІРУРГІВ В ЗАЛЕЖНОСТІ ВІД ВІКУ ТА СТАЖУ РОБОТИ ПРИ ДОБОВОМУ МОНІТОРИНГУ АРТЕРІАЛЬНОГО ТИСКУ

ОЦІНКА ЗМІН ФУНКЦІОНАЛЬНОГО СТАНУ СЕРЦЕВОСУДИННОЇ СИСТЕМИ У ЛІКАРІВ-ХІРУРГІВ В ЗАЛЕЖНОСТІ ВІД ВІКУ ТА СТАЖУ РОБОТИ ПРИ ДОБОВОМУ МОНІТОРИНГУ АРТЕРІАЛЬНОГО ТИСКУ

Systemic and CSF Interleukin-1α Expression in a Rabbit Closed Cranium Subarachnoid Hemorrhage Model: An Exploratory Study.

Background: The inflammatory pathway in cerebrospinal fluid (CSF) leads to delayed cerebral vasospasm (DCVS) and delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH). The role of IL-1α has never been evaluated in a rabbit SAH model. The aim of our study is to analyze systemic and CSF changes of IL-1α, and to evaluate potential associations with the onset of DCVS in a rabbit closed cranium SAH model. Methods: 17 New Zealand white rabbits were randomized into two groups, SAH (n = 12) and sham (n = 5). In the first group, SAH was induced by extracranial-intracranial shunting from the subclavian artery into the cerebral cistern of magna under intracranial pressure (ICP) monitoring. The sham group served as a control. The CSF and blood samples for IL-1α measurement were taken at day zero before SAH induction and at day three. Results: There was a significant increase of ICP (p = 0.00009) and a decrease of cerebral perfusion pressure (CPP) (p = 0.00089) during SAH induction. At follow up, there was a significant increase of systemic IL-1α in the SAH as compared with the sham group (p = 0.042). There was no statistically significant difference in the CSF values in both groups. The CSF IL-1α values showed a correlation trend of DCVS. Conclusions: Systemic IL-1α levels are elevated after SAH induction in a rabbit SAH model.

The dynamics of blood pressure within 12 months after carotid artery stenting in patients with stenotic carotid lesions

Aim. To assess the dynamics of blood pressure (BP) and determine the predictors of the hypotensive effect after carotid artery stenting (CAS).Material and methods. The analysis included 99 patients who underwent CAS in a period of March 2014 and May 2016. Inclusion criteria: (1) the presence of 50% symptomatic or 70% asymptomatic stenosis of the carotid artery (according to NASCET criteria), (2) follow-up for at least 1 year, (3) measurement and recording of BP at four points: 24 hours before surgery, 1 hour, 24 hours and 12 months after surgery. Results. According to office measurement of BP, the average systolic/diastolic pressure was 117,11/60,75, 119,73/60,75, 134,75/70,48 mm Hg after 1 hour, one day and 12 months after the intervention, respectively. In comparison with the average numbers of BP before the intervention, 148,13/89,52 mm Hg there was a significantly significant decrease in BP levels after CAS (p<0,01). According to the results of daily monitoring of blood pressure, a statistically important decrease in blood pressure was observed after 1 year of observation (p<0,01) (136,52/76,84 compared with 145,91/87,63 before the intervention). Dissociated circle of Willis (odds ratio=10,37, 95% confidence interval, from 3,64 to 29,52; p<0,001) and the occurrence of intraoperative hypotension (odds ratio =3,62, 95% confidence interval, from 1,16 to 11,28; p<0,027) were predictors of a persistent decrease in BP after CAS. Conclusion. The obtained results indicated the need for more thorough conservative postoperative management, especially for patients with a dissociated circle of Willis. It is also necessary to achieve the target blood pressure values by individualized correction of antihypertensive therapy.

Vessel wall stiffness parameters and left ventricle remodeling in patients receiving renal replacement therapy

Aim. To perform a comparative assessment of vessel wall stiffness parameters and left ventricle (LV) remodeling in groups of patients with arterial hypertension (AH) receiving renal replacement therapy (RRT) and patients with hypertensive heart disease. Material and methods. One hundred fifty eight people were examined: 32 patients on program hemodialysis (PG), 37 — after kidney transplantation (KT), 69 — with essential hypertension and 20 healthy volunteers. All patients underwent 24-hour blood pressure (BP) monitoring with an assessment of the parameters of daily vessel wall stiffness, aortic pressure and Mand B-mode echocardiography. Results. In groups of patients with PG and after KT, the central and peripheral blood pressure did not differ significantly. When comparing with the group of essential hypertension in RRT patients, with similar values of office systolic and diastolic BP, higher average values of peripheral and central BP were determined. An increase in the values of the pulse wave velocity in the aorta of more than 10 m/s was observed only in RRT patient groups. In all groups of patients with AH, BP and vessel wall Conclusion. Patients receiving RRT have higher values of the average daily pulse wave velocity in the aorta, central BP and a longer period of an increase in the pulse wave velocity in the aorta during the day, higher vessel wall stiffness values, and less pronounced LV spherification than in patients with hypertensive heart disease and comparable values of office BP.

Comparison between central and ambulatory blood pressure measurements in early detection of end organ damage: a single-center prospective non-randomized controlled trial

BackgroundBoth ambulatory blood pressure (AMBP) and non-invasive central blood pressure (NCBP) monitoring could be used as predictors for early detection of hypertensive end organ damage (EOD). However, the comparison between these two methods needs more clarification. Our cross-sectional study included 100 hypertensive patients with a mean age of 47.52 ± 8.35 years on regular antihypertensive treatment for ≥ 1 year (50 controlled, 50 uncontrolled). We compared associations, sensitivity, and specificity of EOD parameters with office, AMBP, and NCBP measurements. We measured left ventricular mass index (LVMI), carotid intimal medial thickness (CIMT), ankle-brachial index (ABI), serum creatinine, glomerular filtration rate (GFR), and pulse wave velocity (PWV).ResultsWe found a significant relation between SBP of NCBP, AMBP and LVMI, and CIMT, PWV, and GFR respectively (P < 0.05) while office SBP showed no significant relation. Systolic AMBP showed a high sensitivity to ABI (98%) and CIMT (92%) while systolic NCBP had 92% specificity and DBP showed 90% sensitivity for ABI.ConclusionAMBP and NCBP show a significant relation to LVMI, CIMT, PWV, and GFR with little superiority of central BP while office BP does not. Systolic ABPM has high sensitivity to ABI and CIMT and systolic NCBP has a high sensitivity and specificity to ABI.

Measurement of ambulatory venous pressure and column interruption duration in normal volunteers

BackgroundAmbulatory venous pressure (AMVP) measurement is considered the gold standard in evaluating calf pump function in chronic venous disease. The AMVP protocol was standardized in the 1970s with pressure monitoring through the dorsal foot vein. This technique was based on the belief that it represents calf venous pressure dynamics owing to rapid equilibration in the superficial and deep systems. This notion is subject to some doubt not only on theoretical grounds, but also owing to a lack of clinical correlation in a segment of the population with chronic venous disease. Our aims were to (1) examine if AMVP measured simultaneously through the dorsal foot vein (DFV) and the great saphenous vein (GSV) would be similar and (2) attempt to devise a noninvasive substitute via duplex measurement for the AMVP test. MethodsThe study was conducted in 76 limbs in 38 normal volunteers. Simultaneous AMVP measurements in DFV and GSV were made in 28 of these normal limbs. Column interruption duration (CID) after calf pump ejection was measured by monitoring duplex resumption of flow in the tibial veins and GSV after calf ejection. The return of AMVP back to baseline implies column restoration. The venous refill time therefore represents the CID via the pressure method. The pressure and duplex methods of CID were compared in the GSV. ResultsKey AMVP parameters (percent drop and venous refill time) significantly differed in DFV and GSV, showing a lack of pressure equilibration. CID measured by duplex in GSV was not significantly different from pressure-derived CID in the same vein. ConclusionsAMVP measured through the DFV does not reflect calf pump generated pressure events in GSV. A duplex method of measuring CID in GSV and posterior tibial vein is described. Duplex-derived CID is not significantly different from pressure-derived CID in the GSV.

The Study of the Fixed Dose Combination of Lisinopril with Prolonged Indopamide (FIXLINDA) with Daily Blood Pressure Monitoring and Diuresis in Hypertensive Patients

Аim. To study the efficacy, tolerability and safety of using a fixed dose combination of an ACE inhibitor lisinopril with a prolonged-action diuretic indapamide in patients with degree 1-2 hypertension.Material and methods. Patients (n = 32) with uncontrolled 1-2 degrees hypertension, moderate or high cardiovascular risk, without severe comorbid diseases, who were prescribed a fixed dose combination of lisinopril (5, 10 or 20 mg) and indapamide (1.5 mg) were included in the observational study. All patients had home monitoring of blood pressure and diuresis, as well as assessment of subjective tolerance of treatment and registration of adverse events within 3 months of observation. Assessment of changes in circadian fluctuations in blood pressure and diuresis, the frequency of achieving the target blood pressure at the outpatient stage, as well as the subjective tolerance of treatment and adverse events during a three-month follow-up.Results. Target blood pressure was achieved in 44.5% of patients taking the fixed dose combination of lisinopril 5 mg + prolonged-acting indapamide1.5 mg; 76.9% – in patients taking the combination of lisinopril 10 mg + indapamide 1.5 mg; 78,6% – in patients taking the combination of lisinopril 20 mg + indapamide 1.5 mg. The achieved antihypertensive effect was characterized by daily circadian stability, accompanied by an improvement in the initially impaired day and night diuretic profile (increase in the share of daytime diuresis by 29.6% and 22.3% with a decrease in the share of nighttime diuresis by 35% and 49% when using a combination with lisinopril 5 and 10 mg, respectively). The treatment was well tolerated by patients and did not cause the development of serious adverse events. Reported adverse events (non-intense dry cough, headache, general weakness) were transient and did not require correction or withdrawal of treatment.Conclusion. The fixed dose combination of the ACE inhibitor lisinopril (5, 10 or 20 mg) and the long-acting thiazide-like diuretic indapamide (1.5 mg) had good antihypertensive efficacy with improved circadian blood pressure and diuresis profiles, acceptable tolerance and safety of treatment, as well as a simple choice of doses of the drug components.

Medical adherence in hypertensive patients treated by triple fixed-dose combination of amlodipine / indapamide / perindopril arginine (results of the Study DOKAZATEL’STVO)

Objective. To estimate changes in medication adherence in patients treated with fixed-dose combination of amlodipine / indapamide / perindopril arginine included in DOKAZATEL’STVO observational study.Design and methods. Effects of the fixed-dose combination of amlodipine / indapamide / perindopril arginine on medication adherence were assessed in 1554 patients who filled in the questionnaire at baseline and at the last visit. Primary outcomes of the study included the change in the office and ambulatory (home blood pressure (BP) monitoring) systolic and diastolic BP from baseline to 3 months and rate of the achievement of target BP &lt; 140/90 mmHg after 3-month treatment. Adherence was assessed by special questionnaire.Results. The fixed-dose combination of amlodipine / indapamide / perindopril arginine resulted in the decrease in systolic BP by 39.5 mmHg and diastolic BP by 18.8 mmHg after 3 months. Target office BP &lt; 140/90 mmHg was achieved in 87 %. High adherence at baseline was observed in 7,1 % patients, after 3 months of treatment — in 38,3 % (p &lt; 0,001). Mean adherence score increased from 2,9 ± 1,6 to 5,0 ± 1,1 (p &lt; 0,001). Study drug intake was associated with increase in motivation and awareness from 38 % to 95,4 % and from 19,8 % to 67,3 %, respectively (p &lt; 0,001 for trend).Conclusions. The administration of the fixed-dose combination of amlodipine / indapamide / perindopril arginine was associated with well tolerated BP decrease and significant increase in medication adherence and motivation even in the absence of specific targeted interventions.

Extraction of implantable cardiac devices: the role of transesophageal echocardiography monitoring

Introduction Background: Data for the utility of continuous trans-esophageal echocardiography (TEE) monitoring during trans venous lead extraction remain scarce. Removal of the implanted transvenous lead system can be a significantly complex procedure, facing main complications. Our objective: the retrospective assessment of the TEE in the monitoring during trans venous lead extraction of implantable cardiac devices (pacemaker and implantable cardiac defibrillator). Methods From November 2013 to November 2018 the transvenous lead extraction of 93 leads in 50 patients was reviewed. Lead extraction techniques combined traction and mechanical approach by the same surgeon. Extraction procedures were performed under general anesthesia either total intravenous or inhalation anesthesia. Invasive arterial line blood pressure and continuous TEE monitoring were performed. TEE images of different projections were acquired and stored before and immediately after the extraction of each lead. Results From the 50 patients (mean age 58.9 years, 64% male, 1.86% lead per patient) which had the following indication: lead dysfunction (24%), upgrade (8%), infection (54%), or other (14%). The lead extraction was complete for 69 out of 93 leads (74.19%), partial extraction was for 24 leads out of 93 leads (25.80%). General anesthesia by total intravenous (30%) and inhalation anesthesia (70%). New TEE findings following TEE were observed in 7 of 50 cases (14%). Two cases which had new mild tricuspid regurgitation without the need of re-intervention, new appearance or worsening of tricuspid regurgitation in three cases which needed non-emergency re-intervention and pericardial effusion in two cases. No cases needed rescue surgery. In all other cases, TEE findings did not entail immediate diagnostic or therapeutic measures. Discussion New findings necessitating immediate therapeutic measures occurred zero cases, no mortality, yet all patients with new TEE findings had strict observational control. We suggest TEE monitoring during trans venous lead extraction, as it provides useful real-time information and should be standard of care monitoring during lead extraction, to guide trans operative and postoperative management. TEE presents some non-negligible risks associated with its use and is a costly procedure, such investment, however, may have a high return in terms of increased patient safety.

Safety and effectiveness of lumacaftor-ivacaftor in adults with cystic fibrosis: A single-center Canadian experience

RATIONALE: Lumacaftor-ivacaftor (LUM-IVA) was approved for use in Canada in January 2016. Observational studies have reported a higher incidence of treatment-emergent adverse events (AEs) leading to treatment discontinuation compared to clinical trials. There is still limited data about long-term tolerability and rates of discontinuation in patients who would not have met clinical trial eligibility criteria. OBJECTIVE: To assess the long-term safety and effectiveness of LUM-IVA in a real-world setting. METHODS: We conducted a single-center retrospective cohort study at St. Paul’s Hospital (Vancouver, Canada). We tracked changes in percent-predicted FEV1 (ppFEV1), body mass index (BMI), sweat chloride concentration, blood pressure (BP) and pulmonary exacerbations pre- and post-initiation of LUM-IVA. We noted AEs and treatment discontinuations. RESULTS: Of 22 patients who started on LUM-IVA as part of routine clinical care, 10 (45%) discontinued therapy after a median of 3.3 months. At initiation, median (IQR) ppFEV1 was 40.1% (32.7%, 55.9%). Respiratory-related symptoms were the most common AEs (59%). We observed a statistically significant increase in BP (p = 0.004). Respiratory-related symptoms and increased BP were the most common reasons for treatment discontinuation, including one instance of hypertensive emergency. There was no change in the median rate of ppFEV1 decline or BMI change despite a statistically significant decrease in sweat chloride concentration 3 months’ post-initiation (p < 0.001). CONCLUSION: The rate of LUM-IVA discontinuation in this adult cystic fibrosis (CF) cohort was high and similar to other observational studies, but we also report cases of increased BP leading to treatment discontinuation. We recommend long-term monitoring of blood pressure for patients on LUM-IVA.

Incidence and Risk Factors for Developing Post-Traumatic Hydrocephalus, Analysis of a Prospective Cohort of 402 Patients

Abstract INTRODUCTION Post-traumatic hydrocephalus (PTH) is a common complication after traumatic brain injury (TBI). PTH incidence and risk factors have principally been derived from retrospective studies or those in the context of hydrocephalus following decompressive craniectomy. The goal of this study was to identify, in a large prospective cohort, the incidence and risk factors for PTH. METHODS This is a single-center retrospective review of a prospectively collected database of patients with severe TBI. PTH was defined as the need for permanent CSF diversion by shunt insertion. Patient demographics, GCS, bleeding patterns, intracranial pressure (ICP) monitoring, and the need for a decompressive craniectomy were considered as explanatory variables. An inverse probability weighted logistic regression model, which considers potential censoring induced by in-hospital mortality, was used as our primary analysis. RESULTS Of the 402 patients included, 40 required permanent CSF for a PTH cumulative incidence of 10% (95% CI: 7.3-13.6). PTH was associated with the need for a decompressive craniectomy [odds ratio (OR): 3.62 (1.62-8.07), P &lt; .01]. Neither age nor gender nor GCS nor bleeding pattern (including intraventricular hemorrhage) was associated with the occurrence of PTH. There were no differences on the initial ICP measurement (10.1 (8.8) vs 9.9 (7.9) mm Hg) or the trend of the ICP between patients who ultimately developed PTH and those who did not. CONCLUSION PTH develops in approximately 10% of patients with severe TBI. Patients who require a decompressive craniectomy are at a higher risk. Neither intracranial hypertension nor intraventricular hemorrhage was a relevant risk factor.

Application of transesophageal echocardiography in anesthesia management in modified morrow operation

Objective To evaluate the application of transesophageal echocardiography (TEE) in anesthesia management of obstructive hypertrophic cardiomyopathy (HOCM) during modified morrow operation and to evaluate the effect of TEE on surgical decision-making. Methods Twenty-one HOCM patients who were admitted into our hospital from March 2015 to March 2019 for TEE were selected. All patients underwent transesophageal ultrasound. The diameter of the narrowest left ventricular outflow tract, and subaortic interventricular septal thickness and length were recorded before and after operation. Continuous Doppler flow velocity was measured at the left ventricular outflow tract and the difference of transvalvular pressure was calculated. At point of mitral valve apex, peak velocity and atrial filling (A) and early filling (E) of mitral valve were recorded on four-chamber level of middle esophagus, E/A(mitral valve E peak velocity divided by A peak velocity ratio). Early diastolic (e′) phase of ventricular lateral wall of mitral annulus with tissue doppler, E/e′ (mitral valve E peak velocity divided by mitral annulus e′) were recorded. Results Intro-operative aerodynamics was stable and no malignant adverse events such as ventricular fibrillation occurred. There were 18 cases of auto-cardiac resuscitation (85%), 3 cases of temporary pacemaker use (15%), while 17 patients (81%) did not need to use positive inotropic drugs after rebound, but could successfully depart from cardiopulmonary bypass at low doses of deoxyepinephrine. The remaining four patients (19%) required low doses of milrinone or combined with deoxyepinephrine or norepinephrine. The cardiopulmonary bypass (CPB) time was (124±45) min and the aortic occlusion time was (85±21) min. The trans-valvular pressure of left ventricular outflow tract decreased to (68±8) mmHg (1 mmHg=0.133 kPa) to (16±6) mmHg by TEE after operation (P 14, and the lateral wall of ventricular septum e′ was<10 cm/s. Conclusions TEE plays an important role in anesthesia management, surgical decision-making and evaluation of operation. For patients with normal systolic function, TEE monitoring of transvalvular pressure through deep transgastric lax is consistent with intraoperative monitoring of transvalvular pressure through catheter. Key words: Transesophageal echocardiography; Modified morrow operation; Obstructive hypertrophic cardiomyopathy; Anesthesia management

Self-blood pressure monitoring as a tool to increase hypertension awareness, adherence to antihypertensive therapy, and blood pressure control.

Self-blood pressure monitoring as a tool to increase hypertension awareness, adherence to antihypertensive therapy, and blood pressure control.

Device monitoring in heart failure management: outcomes based on a systematic review and meta-analysis.

Implantable devices have been developed for continuous monitoring of heart failure. We investigated the effect of fluids and hemodynamic monitoring, using these devices, on heart failure clinical outcomes. Literature search was performed January 2000 through May 2017 of studies comparing device monitored patients with control group. Random-effects meta-analysis was used to pool outcomes across the studies. A total of 5,454 patients were included from 14 studies. There was no difference in heart failure (HF)-related admissions rate [odds ratio (OR) 1.25, 95% CI: 0.92-1.69, P=0.15], all-cause mortality (OR 1.21, 95% CI: 0.91-1.61, P=0.20) or combined admission rate and all-cause mortality (OR 1.21, 95% CI: 0.89-1.64, P=0.22) between the device monitored and the control group. In a subgroup analysis including only pressure sensors devices, there was no difference in all-cause mortality (OR 1.04, 95% CI: 0.62-1.74, P=0.89), however, there was a lower admissions rate (OR 1.63, 95% CI: 1.10-2.41, P=0.02). In a subgroup of only impedance monitoring devices, there was no difference in all-cause mortality or admissions rate. Pressure monitoring was associated with lower HF admissions rate. No improvement in these outcomes was noted with impedance monitoring.

Comparison of blood pressure measurements in upper and lower extremities in children less than 1 year of age under general anesthesia

Blood pressure (BP) monitoring can be obtained non-invasively (NIBP) by oscillometry or invasively (IBP) by an arterial cannula. Limited data exists comparing NIBP to IBP and NBIP taken in the upper versus lower extremities in pediatric patients. With BP guiding major therapeutic decisions in pediatric intensive care units, inaccuracies may complicate the timely diagnosis and treatment of hypotension. We aim to evaluate clinically significant errors in NIBP relative to IBP measurements, while secondarily investigating the consistency of upper versus lower extremity NIBP. Using anesthetized patients as a surrogate for mechanically ventilated patients …

Influence of different lying positions on monitoring of central venous pressure in patients with mechanical ventilation: a systematic review

Objective To review systematically the influence of different lying positions on monitoring of central venous pressure (CVP) in patients with mechanical ventilation. Methods Relevant articles published publicly from database establishment date to June, 30th, 2018 in PubMed, Cochrane Library, Embase, Web of Science, CBM, Chinese Academic Journal Full-text Database (CJFD) , Wanfang and VIP Database were searched on computer. Two researchers independently screened and extracted the literature. RevMan 5.3 software was used for meta-analysis of the included studies. Results Nine literatures were included, including 380 subjects. Meta-analysis showed that there were significant statistical differences in CVP values between 30 degree semi-recumbent position and supine position (WMD=-0.70, 95%CI: -1.15--0.24, P=0.003) , and between 45 degree semi-recumbent position and supine position (WMD=-1.34, 95%CI: -1.82--0.86, P<0.001) , and between 60 degree semi-recumbent position and supine position (WMD=-2.96, 95%CI: -3.91--2.00, P<0.001) . Conclusions There are differences between the CVP measurements in the 30°, 45°, 60° hemi-recumbent position and the supine position. To ensure the accuracy of the CVP measurement values in mechanical ventilation patients, we should take the supine position for measurement. Key words: Central venous pressure; Lying position; Monitoring; Mechanical ventilation; Systematic review

E-Knitted Textile with Polymer Optical Fibers for Friction and Pressure Monitoring in Socks.

The objective of this paper is to study the ability of polymer optical fiber (POF) to be inserted in a knitted fabric and to measure both pressure and friction when walking. Firstly, POF, marketed and in development, have been compared in terms of the required mechanical properties for the insertion of the fiber directly into a knitted fabric on an industrial scale, i.e. elongation, bending rigidity, and minimum bending radius before plastic deformation. Secondly, the chosen optical fiber was inserted inside several types of knitted fabric and was shown to be sensitive to friction and compression. The knitted structure with the highest sensitivity has been chosen for sock prototype manufacturing. Finally, a feasibility study with an instrumented sock showed that it is possible to detect the different phases of walking in terms of compression and friction.

Pressure Injury Prevention: A Survey.

Pressure injuries are caused by prolonged pressure to an area of the body, which can result in open wounds that descend to the bone. Pressure injuries should not occur in healthcare settings, and yet, they still affect 2.5 million patients in the United States and have an impact on quality of life. Pressure injuries come at a cost of $11 billion in the United States, and 90% of pressure injuries are a secondary condition. In this paper, we survey the literature on preventative techniques to address pressure injures, which we classify into two categories: active prevention strategies and sensor-based risk-factor monitoring. Within each category of techniques, we discuss the literature and assess each class of strategies based on its commercial availability, results of clinical trials when available, the ability for the strategy to save time for healthcare staff, and whether the technique can be tuned to an individual. Based on our findings, the most promising current solutions, supplementary to nursing guidelines, are electrical stimulation, pressure monitoring, and inertial measurement unit monitoring. We also find a need for a clinical software system that can easily integrate with custom sensors, use custom analysis algorithms, and provide visual feedback to the healthcare staff.

Fatigue testing of integrated thin film metal membranes for implantable biomedical pressure sensors

The longevity of thin film membranes is vital for the lifetime monitoring of fluid pressure inside the human body. However, aging and mechanical fatigue of the thin film material hinders the long-term reliability of implantable pressure sensors. Despite this, designers tend to neglect the fatigue life analysis of thin films in the design and fabrication of MEMS pressure sensors. Here, we present a low-cost fatigue testing system, which is custom designed from a modern multimedia speaker and subwoofer system. The subwoofer acts as an acoustic booster to amplify the sound vibrations into large stress amplitudes required for displacing the thin film membranes. A Keyence laser displacement sensor records the displacements of the thin films triggered in response to the sound-based stress amplitudes. A scanning electron microscope (SEM) is used in observing the surfaces of the thin films. An FEA parametric study and the fatigue testing results show significant correlations, except for the displacements values as the input Gaussian random vibrations are exaggerated in the experiments to visualize the bursting nature of the thin film membranes.

Conventional and Specific-Pathogen Free Rats Respond Differently to Anesthesia and Surgical Trauma

Specific-pathogen free (SPF) animals were introduced in the 1960s to minimize disease and infection as variables in biomedical research. Our aim was to examine differences in physiological response in rat colonies bred and housed in a conventional versus SPF facility, and implications for research. Sprague-Dawley rats were anesthetized and catheterized for blood and pressure monitoring, and electrocardiogram (ECG) leads implanted. Hematology was assessed, and coagulation profile using rotational thromboelastometry. Health screening was outsourced to Cerberus Sciences. SPF rats had significantly lower pulse pressure (38% decrease), arrhythmias and prolonged QTc (27% increase) compared to conventional rats. No arrhythmias were found in conventional rats. SPF rats had significantly higher white cell, monocyte, neutrophil and lymphocyte counts, and were hyperfibrinolytic, indicated by EXTEM maximum lysis >15%. Independent assessment revealed similar pathogen exclusion between colonies, with the exception of Proteus in SPF animals. Returning to a conventional facility restored normal host physiology. We conclude that SPF animals displayed an abnormal hemodynamic, hematological and hemostatic phenotype in response to anesthesia and surgery, and provide a number of recommendations to help standardize research outcomes and translation.