The Presence of Blood in a Strain Gauge Pressure Transducer Has a Clinical Effect on the Accuracy of Intracranial Pressure Readings

IMPORTANCE

Patients admitted with cerebral hemorrhage or cerebral edema often undergo external ventricular drain (EVD) placement to monitor and manage intracranial pressure (ICP). A strain gauge transducer accompanies the EVD to convert a pressure signal to an electrical waveform and assign a numeric value to the ICP.

OBJECTIVES

This study explored ICP accuracy in the presence of blood and other viscous fluid contaminates in the transducer.

DESIGN

Preclinical comparative design study.

SETTING

Laboratory setting using two Natus EVDs, two strain gauge transducers, and a sealed pressure chamber.

PARTICIPANTS

No human subjects or animal models were used.

INTERVENTIONS

A control transducer primed with saline was compared with an investigational transducer primed with blood or with saline/glycerol mixtures in mass:mass ratios of 25%, 50%, 75%, and 100% glycerol. Volume in a sealed chamber was manipulated to reflect changes in ICP to explore the impact of contaminates on pressure measurement.

MEASUREMENTS AND MAIN RESULTS

From 90 paired observations, ICP readings were statistically significantly different between the control (saline) and experimental (glycerol or blood) transducers. The time to a stable pressure reading was significantly different for saline vs. 25% glycerol (< 0.0005), 50% glycerol (< 0.005), 75% glycerol (< 0.0001), 100% glycerol (< 0.0005), and blood (< 0.0005). A difference in resting stable pressure was observed for saline vs. blood primed transducers (0.041).

CONCLUSIONS AND RELEVANCE

There are statistically significant and clinically relevant differences in time to a stable pressure reading when contaminates are introduced into a closed drainage system. Changing a transducer based on the presence of blood contaminate should be considered to improve accuracy but must be weighed against the risk of introducing infection.

Non-Nutritive Suck Parameters Measurements Using a Custom Pressure Transducer System

The non-nutritive suck (NNS) device is a transportable, user-friendly pressure transducer system that quantifies infants' NNS behavior on a pacifier. Recording and analysis of the NNS signal using our system can provide measures of an infant's NNS burst duration (s), amplitude (cmH2O), and frequency (Hz). Accurate, reliable, and quantitative assessment of NNS has immense value in serving as a biomarker for future feeding, speech-language, cognitive, and motor development. The NNS device has been used in numerous research lines, some of which have included measuring NNS features to investigate the effects of feeding-related interventions, characterizing NNS development across populations, and correlating sucking behaviors with subsequent neurodevelopment. The device has also been used in environmental health research to examine how exposures in utero can influence infant NNS development. Thus, the overarching goal in research and clinical utilization of the NNS device is to correlate NNS parameters with neurodevelopmental outcomes to identify children at risk for developmental delays and provide rapid early intervention.

Resuscitative endovascular balloon occlusion of the aorta management guided by a novel handheld pressure transducer

BACKGROUND

Management of noncompressible truncal hemorrhage using resuscitative endovascular balloon occlusion of the aorta (REBOA) requires arterial pressure monitoring that can be logistically challenging in austere or emergency settings. Novel pressure transducer devices such as the Centurion Compass device (CD) (Medline, Northfield, IL) offer an alternative to traditional monitoring systems. We sought to assess the feasibility of maintaining permissive hypotension during intermittent REBOA in a porcine model guided by CD monitoring.

METHODS

Eight Yorkshire swine underwent 20% hemorrhage with an uncontrolled iliofemoral vascular injury. Time-based intermittent zone 1 REBOA was performed with volume-based resuscitation to maintain permissive hypotension. Proximal mean arterial pressures (MAPs) from a carotid arterial line (AL) were obtained and compared with CD readings from the proximal REBOA port. The operator was blinded to AL MAP, and the REBOA was managed with exclusively the CD.

RESULTS

Mean survival time was 100 minutes (range, 41-120 minutes) from injury. Arterial line and CD measurements were closely correlated (r = 0.94, p < 0.001). Bland-Altman analysis for comparison of clinical measurements demonstrated a mean difference of 6 mm Hg (95% confidence interval, -22 to 34 mm Hg) for all MAPs, with a mean difference of 3 mm Hg (95% confidence interval, -6 to 12 mm Hg) in a clinically relevant MAP of <65 mm Hg subset.

CONCLUSION

The CD represents a miniaturized and portable arterial pressure monitor that provides an accurate alternative to logistically burdensome AL monitoring to guide REBOA use. The device is highly accurate even at hypotensive pressures and can be used to guide intermittent REBOA strategies.

Potential damage in pulmonary arterial hypertension: An experimental study of pressure-induced damage of pulmonary artery

Pulmonary arterial hypertension (PAH) is associated with elevated pulmonary arterial pressure. PAH prognosis remains poor with a 15% mortality rate within 1 year, even with modern clinical management. Previous clinical studies proposed wall shear stress (WSS) to be an important hemodynamic factor affecting cell mechanotransduction, growth and remodeling, and disease progress in PAH. However, WSS in vivo is typically at most 2.5 Pa and a doubt has been cast whether WSS alone can drive disease progress. Furthermore, our current understanding of PAH pathology largely comes from small animals' studies in which caliber enlargement, a hallmark of PAH in humans, is rarely reported. Therefore, a large-animal experiment on pulmonary arteries (PAs) is needed to validate whether increased pressure can induce enlargement of PAs caliber. In this study, we use an inflation testing device to characterize the mechanical behavior, both nonlinear elastic behavior and irreversible damage of porcine arteries. The parameters of elastic behavior are estimated from the inflation test at a low-pressure range before and after over-pressurization. Then, histological images are qualitatively examined for medial and adventitial layers. This study sheds light on the relevance of pressure-induced damage mechanism in human PAH.

A Wireless Implantable Passive Intra-Abdominal Pressure Sensing Scheme via Ultrasonic Imaging of a Microfluidic Device

In this article, we demonstrate a wireless and passive physiological pressure sensing scheme that utilizes ultrasound imaging of an implantable microfluidic based pressure sensitive transducer. The transducer consists of a sub-mm scale pressure sensitive membrane that covers a reservoir filled with water and is connected to a hydrophobic micro-channel. Applied pressure onto the transducer deflects the membrane and pushes the water from the reservoir into the channel; the water's travelling distance in the channel is a function of the applied pressure, which is quantitatively measured by using a 40 MHz ultrasound imaging system. The sensor presents a linear sensitivity of 42 kPa/mm and a spatial resolution of 1.2 kPa/30 μm in the physiological range of abdominal compartment syndrome. Reliability assessments of the transducer confirm its ability to remain functional after more than 600 cycles of pressure up to 55 kPa over the course of 2 days. Ex vivo experimental results verify the practical capability of the technology to effectively measure pressures under a 15 mm thick porcine skin. It is anticipated that this technology can be applied to a broad range of implantable pressure measurement, by simply tuning the thickness of the thin polydimethylsiloxane membrane and the geometry of the reservoir.

Comparison of extraocular and intraocular pressure transducers for measurement of transient intraocular pressure fluctuations using continuous wireless telemetry

The optimal approach for continuous measurement of intraocular pressure (IOP), including pressure transducer location and measurement frequency, is currently unknown. This study assessed the capability of extraocular (EO) and intraocular (IO) pressure transducers, using different IOP sampling rates and duty cycles, to characterize IOP dynamics. Transient IOP fluctuations were measured and quantified in 7 eyes of 4 male rhesus macaques (NHPs) using the Konigsberg EO system (continuous at 500 Hz), 12 eyes of 8 NHPs with the Stellar EO system and 16 eyes of 12 NHPs with the Stellar IO system (both measure at 200 Hz for 15 s of every 150 s period). IOP transducers were calibrated bi-weekly via anterior chamber manometry. Linear mixed effects models assessed the differences in the hourly transient IOP impulse, and transient IOP fluctuation frequency and magnitude between systems and transducer placements (EO versus IO). All systems measured 8000-12,000 and 5000-6500 transient IOP fluctuations per hour > 0.6 mmHg, representing 8-16% and 4-8% of the total IOP energy the eye must withstand during waking and sleeping hours, respectively. Differences between sampling frequency/duty cycle and transducer placement were statistically significant (p < 0.05) but the effect sizes were small and clinically insignificant. IOP dynamics can be accurately captured by sampling IOP at 200 Hz on a 10% duty cycle using either IO or EO transducers.

Electroactive polymer-based inner vessel-wall pressure transducer capable of integration with a PTA balloon catheter for examining blood vessel health

This study presents a state-of-the-art soft and biocompatible transducer capable of detecting vessel inner-wall pressure for biomedical applications. The device includes a 3D electroactive polymer core element encapsulated by polydimethylsiloxane with an ellipsoidal structure. The device produces a voltage output when its sensing mechanism experiences different pressures, resulting in deformation at different orientations. Thus, it can be employed to detect the pressure exerted by inner vessel walls of different stiffness values. The output voltage is induced by the strain experienced by the sensing mechanism of the device without the need for any external electrical power source. The core element, which is made of an ionic polymer-metal composite, possesses a unique hollow design; this allows a catheter to pass through, and the core element can be anchored at an arbitrary position on the catheter. We also demonstrate that the fabricated device can be integrated with a medically used percutaneous transluminal angioplasty balloon catheter to form a smart sensing module. This module can detect different levels of fat accumulation around the inner wall of a blood vessel phantom. Evaluating vessel blockage and stiffness using the signals acquired from the developed device is discussed.

Benefit of Contact Force-Guided Catheter Ablation for Treating Premature Ventricular Contractions

We evaluated whether an irrigated contact force-sensing catheter would improve the safety and effectiveness of radiofrequency ablation of premature ventricular contractions originating from the right ventricular outflow tract. We retrospectively reviewed the charts of patients with symptomatic premature ventricular contractions who underwent ablation with a contact force-sensing catheter (56 patients, SmartTouch) or conventional catheter (59 patients, ThermoCool) at our hospital from August 2013 through December 2015. During a mean follow-up of 16 ± 5 months, 3 patients in the conventional group had recurrences, compared with none in the contact force group. Complications occurred only in the conventional group (one steam pop; 2 ablations suspended because of significantly increasing impedance). In the contact force group, the median contact force during ablation was 10 g (interquartile range, 7-14 g). Times for overall procedure (36.9 ± 5 min), fluoroscopy (86.3 ± 22.7 s), and ablation (60.3 ± 21.4 s) were significantly shorter in the contact force group than in the conventional group (46.2 ± 6.2 min, 107.7 ± 30 s, and 88.7 ± 32.3 s, respectively; P <0.001). In the contact force group, cases with a force-time integral <560 gram-seconds (g-s) had significantly longer procedure and fluoroscopy times (both P <0.001) than did those with a force-time integral ≥560 g-s. These findings suggest that ablation of premature ventricular contractions originating from the right ventricular outflow tract with an irrigated contact force-sensing catheter instead of a conventional catheter shortens overall procedure, fluoroscopy, and ablation times without increasing risk of recurrence or complications.

Interference Between Pressure-Wire and Deployed Coronary Stents: Insights from a Bench Test

BACKGROUND

While several complications related to pressure-wire (PW) have been reported, mechanistic justification has not always been offered. Furthermore, interference between a PW and a protruding side-branch stent has not been previously reported. The purpose of this study was to evaluate interference between PW-pullback from a main-branch with a protruded ostial stent deployed in a side-branch.

METHODS

In a polyurethane bifurcation vessel model, PW-pullback was performed in a main-branch following protruded ostial stenting in a side-branch. Tested PWs included PressureWire X, Comet, OptoWire, and Verrata. For each PW, pullback was performed through the same proximal cell of the protruded stent 20 times. Interference during PW-pullback was objectively analyzed with a fiberscope placed at the distal main-branch and classified into 3 grades according to the interaction with stent strut.

RESULTS

There were significant differences in the rate of interference between the PWs. No-interference, interference without strut traction, and interference with strut traction (i.e. stent deformation) were observed as follows: 17/20, 3/20, and 0/20 in PressureWire X; 19/20, 1/20, and 0/20 in Comet; 8/20, 10/20, and 2/20 in OptoWire; and 13/20, 2/20, and 5/20 in Verrata, respectively (p for any differences: <0.001). Visually identifiable major stent deformation was observed once in OptoWire due to the deep concave sensor window and twice in Verrata due to the proximal gap between the sensor and coiled-wire.

CONCLUSIONS

PW-pullback in the main-branch after side-branch ostial stenting should be carefully performed to avoid stent deformation. Consideration on the specific mechanical features of the PW is also essential.

A Case-Based Illustration of the Use of Microcatheter Pressure Transduction for Confirmation of Distal Wire Position in Complex Percutaneous Coronary Intervention

Determining distal wire position during chronic total occlusion percutaneous coronary intervention can be challenging. We describe a novel technique that can help confirm distal true lumen wire position. A microcatheter is advanced distally over the wire and after removing the guidewire, it is connected to a manifold for pressure transduction: an arterial waveform is indicative of intra-luminal position.

Ambulatory Fontan pressure monitoring: Results from the implantable hemodynamic monitor Fontan feasibility cohort (IHM-FFC)

BACKGROUND

Implantable invasive hemodynamic monitoring (IHM) using the CardioMEMS™ HF system has been shown to reduce heart failure (HF) hospitalizations. IHMs have not yet been used in congenital heart disease (CHD). We aimed to evaluate feasibility and mid-term outcomes of IHM use in the single ventricle/Fontan population.

METHODS

Six adult Fontan patients (>1 HF admission, NYHA FC >3) were enrolled (30 ± 7 years old, mean pulmonary artery pressure (mPA) 16 ± 4.7 mm Hg). Heart failure mediated events (HFME) were evaluated for 12 months: CV medication change, hospital admission, paracentesis, and change in orthotopic heart transplant (OHT) listing status.

RESULTS

The IHM device was successfully placed in all participants. In total there were 671 IHM transmissions and 25(3.7%) HFME. The mean PA pressure across all episodes was 18.2 ± 6.6 mm Hg (range 6-40 mm Hg). Higher mPA pressures were associated with greater odds of having a HFME (OR 1.17 [1.09, 1.25], p < 0.0001). Mean PA pressure had good ability to discriminate transmissions associated with HFME (AUC 0.76 [0.654, 0.866]), with mean PA pressures >24 mm Hg or individual mPA change >4 mm Hg, best discriminating transmissions associated with HFME.

CONCLUSIONS

In the first feasibility series of adult Fontan patients undergoing CardioMEMS™ implantation we demonstrate early technical success and no device-related adverse events. We propose that ambulatory mean PA pressures >24 mm Hg or individual mPA change >4 mm Hg may be associated with more HFME. Further large-scale studies in this population are recommended.

Sensor-actuator component for a Floating Mass Transducer-based fully implantable hearing aid

We propose a novel system based on the Floating Mass Transducer (FMT) to be used as the active component of a fully implantable, Vibrant Soundbridge-like middle ear implant. The new system replaces the external microphone used in the currently available design with an implantable piezoelectric sensor that is inserted into the incudostapedial joint and picks up the vibrations transmitted to the long process of the incus. The FMT is coupled to the round window of the cochlea. We characterize the system by measuring the gain in intracochlear sound pressure using laser Doppler vibrometry at a surgically installed "third window" into the cochlea of six temporal bones. Closed-loop feedback oscillations limit the system's available output. We show that using an adaptive control algorithm, a mean functional gain of up to 40 dB is achieved, which is similar to Soundbridge functional gain. The concept matches the FMT's one-point fixation philosophy and offers several advantages over other designs, namely an easy and time-efficient surgery, reversibility of implantation, and natural hearing for the prospective patient.

Sex Differences in Adenosine-Free Coronary Pressure Indexes: A CONTRAST Substudy

OBJECTIVES

The goal of this study was to investigate sex differences in adenosine-free coronary pressure indexes.

BACKGROUND

Several adenosine-free coronary pressure wire indexes have been proposed to assess the functional significance of coronary artery lesions; however, there is a theoretical concern that sex differences may affect diagnostic performance because of differences in resting flow and distal myocardial mass.

METHODS

In this CONTRAST (Can Contrast Injection Better Approximate FFR Compared to Pure Resting Physiology?) substudy, contrast fractional flow reserve (cFFR), obtained during contrast-induced submaximal hyperemia, the instantaneous wave-free ratio (iFR), and distal/proximal coronary pressure ratio (Pd/Pa) were compared with fractional flow reserve (FFR) in 547 men and 216 women. Using FFR ≤0.8 as a reference, the diagnostic performance of each index was compared.

RESULTS

Men and women had similar diameter stenosis (p = 0.78), but women were less likely to have FFR ≤0.80 than men (42.5% vs. 51.5%, p = 0.04). Sensitivity was similar among cFFR, iFR, and Pd/Pa when comparing women and men, respectively (cFFR, 77.5% vs. 75.3%; p = 0.69; iFR, 84.9% vs. 79.4%; p = 0.30; Pd/Pa, 78.8% vs. 77.3%; p = 0.78). cFFR was more specific than iFR or Pd/Pa regardless of sex (cFFR, 94.3% vs. 95.8%; p = 0.56; iFR, 75.6% vs. 80.1%; p = 0.38; Pd/Pa, 80.6% vs. 78.7%; p = 0.69). By receiver-operating characteristic curve analysis, cFFR provided better diagnostic accuracy than resting indexes irrespective of sex (p ≤ 0.0001).

CONCLUSIONS

Despite the theoretical concern, the diagnostic sensitivity and specificity of cFFR, iFR, and Pd/Pa did not differ between the sexes. Irrespective of sex, cFFR provides the best diagnostic performance.

Contact-force-guided vs. contact-force-blinded catheter ablation of typical atrial flutter: a prospective study

Aims

It remains unknown whether contact force (CF) sensing technology is of value for cavotricuspid isthmus (CTI) ablation. We prospectively evaluated procedural parameters and outcomes of CF-guided vs. CF-blinded CTI ablation for typical atrial flutter (AFL).

Methods and results

A total of 70 consecutive patients (62.5 ± 10.9 years) undergoing CTI ablation for AFL were prospectively enrolled, 35 in CF-blinded and 35 in CF-guided groups. A CF-sensing catheter (power 25-35 W) was used in all. In the CF-guided group, CF target range was 10-25 g, whereas in the CF-blinded group, the operator was blinded to CF. The isthmus was divided into anterior, middle, and posterior segments for region-specific CF analysis. The procedural endpoint of bidirectional isthmus block following a 20-min observation period was achieved in all. A trend towards lower fluoroscopy and procedure duration was observed when the CF-guided group was compared with the CF-blinded group. The total radiofrequency (RF) energy delivery time required to achieve bidirectional block was significantly lower in the CF-guided vs. CF-blinded group [10.0 min (IQR 8.3;15.1) vs. 15.9 min (IQR 9.6;24.7), P= 0.0020], with a significant inverse correlation between CF and total RF delivery time (r = -0.36; P= 0.0027). Mean CF measurements significantly increased from anterior to posterior anatomical zones of CTI in the CF-blinded group (ANOVA P= 0.0466).

Conclusions

Catheter ablation of AFL guided by real-time CF assessment results in a significant reduction in total RF delivery time. Real-time CF measurements facilitate the maintenance of homogenous efficient contact all along the CTI, particularly in the anterior segment where CF is generally lower.

A Super-Capacitive Pressure Sensor for a Urethral Catheter

Urinary incontinence can be due to neuromuscular or structural problems in either the bladder or the urethra. Urodynamics is often used to analyze the patientspecific cause of urinary incontinence. In urodynamics, a challenging part of the studies involves measurement of the urethral (contact) pressure profile. Here we present an instrumented urethral catheter that is equipped with a novel super-capacitive pressure transducer that is highly sensitive to the applied pressure. A solid ionic electrolyte is used to create a high capacitance device. Through an innovative design the solid electrolyte is made and bounded to a 3d printed soft balloon and then assembled on a 6 Fr urethral catheter. In this paper the design, fabrication and evaluation of the highly-sensitive instrumented catheter's performance are discussed.

Medial Compartment Decompression by Proximal Fibular Osteotomy: A Biomechanical Cadaver Study

Medial compartment knee osteoarthritis is a painful and debilitating disease. A proximal fibular osteotomy is a novel, simple surgical technique that may reduce pain and improve function for patients with osteoarthritis. The purpose of this biomechanical cadaver study was to determine what effect proximal fibular osteotomy had on knee joint and ankle pressures and tibia strain. Ten matched pairs of cadaver legs were tested in compression to 1.1 times body weight comparing intact and with proximal fibular osteotomy at 0°, 15°, and 30° of flexion. Sensors were inserted into the knee and ankle joint to measure pressure, force, and contact area. Strain was measured with a strain gage on the anterior medial tibia. In the medial compartment, the peak force, contact area, and pressure all decreased from intact to after fibular osteotomy, with significant differences at 15° of flexion (P<.05). There were no significant differences in the lateral compartment for any measures. In the ankle joint, the peak force and pressure decreased from intact to after fibular osteotomy at all 3 flexion angles. There were no significant changes in strain in the tibia. Proximal fibular osteotomy decreases the pressure in the medial compartment of the knee, which may reduce knee pain and improve function in patients with medial compartment knee osteoarthritis. [Orthopedics. 2018; 41(4):e496-e501.].

The effect of saddle nose width and cutout on saddle pressure distribution and perceived discomfort in women during ergometer cycling

The objectives were 1) to design and produce two novel unpadded bicycle saddles with a wide/medium width and partial nose cutout; 2) to investigate the responses on pressure distribution and perceived discomfort in female cyclists. For comparison, a standard saddle was also tested. Nineteen female cyclists pedaled on an ergometer cycle for 20 min with each saddle in a counterbalanced order. A pressure mat measured saddle interface pressure. Discomfort ratings were collected using a visual analogue scale. Total mean saddle pressure remained similar across saddles. The wide saddle increased anterior and decreased posterior mean saddle pressure as compared with the standard (p < .002) and the medium saddle (p < .001). Significantly increased ischial tuberosity discomfort was found for the novel saddles (p < .001), while crotch discomfort was not significantly different between saddles. The medium width saddle appeared to be the best compromise since increased crotch discomfort was avoided and saddle pressures were redistributed. Such design may be suggested as an alternative to traditional saddles for women reporting discomfort in the perineal region.

Uncertainty of speech level parameters measured with a contact-sensor-based device and a headworn microphone

This work estimates the uncertainty contributions of speech level parameters measured with a contact-sensor-based device and a headworn microphone. Four contributions are considered: (1) instrumental uncertainty, related to device calibration; (2) method repeatability and (3) reproducibility, estimated through repeated measurements without and with device repositioning, respectively; (4) source reproducibility, due to the variability of human speech. To ascertain changes in speech production, differences between measures should be at least higher than the expanded uncertainty. In the case of device repositioning, the expanded uncertainty combines contributions (1), (3), and (4). When the device is not repositioned, it combines contributions (2) and (4).

Analysis of epidural waveform for cervical epidural steroid injections confirmed with fluoroscopy

The identification of epidural space with loss of resistance (LOR) is commonly performed. But it lacks specificity. Epidural pressure waveform analysis (EPWA) provides a simple confirmative adjunct for LOR. If the needle is located within the epidural space, measurement of the pressure at its tips shows a pulsatile waveform. Previous studies demonstrated satisfactory sensitivity and specificity of EPWA. However, success or failure of epidural injection was confirmed by the pinprick test, which is limited for patients in the setting of the pain clinic. In this study, we evaluated the sensitivity, specificity, as well as positive and negative predictive values of EPWA for cervical epidural steroid injection (CESI) confirmed by fluoroscopy.One hundred and five CESIs of 75 patients suffering from neck and radicular arm pain of over 3 months duration were enrolled. The physician injected 5 mL of normal saline after a feeling of satisfactory LOR. Saline filled extension tubing, connected to a pressure transducer, was attached to the needle. A 3 mL bolus of contrast medium was injected to confirm the success of CESI.The incorrect identification of epidural space with LOR (false LOR) was 29.5%. Of these 31 failed CESIs, 2 showed epidural waveform and 29 did not. The sensitivity, specificity, positive and negative predictive value of EPWA was 94.5%, 93.5%, 97.2%, and 87.7%, respectively.EPWA shows satisfactory reliability and is a simple adjunct to decrease false LOR for CESI. Further confirmative studies are required before its routine use in clinical practice.

The quantitative evaluation of the relationship between the forces applied to the palm and carpal tunnel pressure

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy occurring in upper limbs. The etiology, however, has not been fully understood yet. Median nerve could be compressed by either increase of carpal tunnel pressure (CTP) or direct impingement when it is forced toward to carpal ligament especially in wrist flexion leading to CTS development. Thus, the increase of carpal tunnel pressure is considered an important role in CTS development. It has been identified that forces applied to the palm would affect the CTP. However, the quantitative relationship between palmar contact force and CTP is not known. The purpose of this study was to quantitatively evaluate the relationship between palmar contact force and CTP. Eight human cadaveric hands were used. The CTP was measured with a diagnostic catheter-based pressure transducer inserted into the carpal tunnel. A custom made device was used to apply forces to the palm for the desired CTP. Palmar contact forces corresponding to the determined CTP level were recorded respectively. The testing was repeated with different ranges of tension applied to the flexor digitorum superficialis tendon of the third finger. The tensions were constant at 50 g for the other flexor tendons and median nerve. The results showed that CTP increased linearly with the force applied to the palm. When CTP was 30 mmHg, mean values of the contact force to the palm was 293 g (SD: 15.2) including all tensions. These results would help to understand the effect of daily activities with hands on CTP.

Evaluation of an experimental electrohydraulic discharge device for extracorporeal shock wave lithotripsy: Pressure field of sparker array

In this paper, an extracorporeal shock wave source composed of small ellipsoidal sparker units is described. The sparker units were arranged in an array designed to produce a coherent shock wave of sufficient strength to fracture kidney stones. The objective of this paper was to measure the acoustical output of this array of 18 individual sparker units and compare this array to commercial lithotripters. Representative waveforms acquired with a fiber-optic probe hydrophone at the geometric focus of the sparker array indicated that the sparker array produces a shock wave (P⁺ ∼40-47 MPa, P^- ∼2.5-5.0 MPa) similar to shock waves produced by a Dornier HM-3 or Dornier Compact S. The sparker array's pressure field map also appeared similar to the measurements from a HM-3 and Compact S. Compared to the HM-3, the electrohydraulic technology of the sparker array produced a more consistent SW pulse (shot-to-shot positive pressure value standard deviation of ±4.7 MPa vs ±3.3 MPa).

Vibration transmission of the spine during walking is different between the lumbar and thoracic regions in older adults

Background

fractures occur more commonly in the thoracic than in the lumbar spine. Physical activity complemented with pharmacological interventions has been advocated as a preventive measure for osteoporosis. However, walking has been shown to produce only a small improvement in spinal bone mineral density. The characteristics of vibration transmission during walking at the lumbar and thoracic spines may be different, and this may help explain the relative incidence of fractures in the two spine regions.

Objective

to determine how mechanical vibration is transmitted in the lumbar and thoracic spines in older adults with and without osteoporosis.

Methods

16 young healthy adults, 19 older adults without osteoporosis and 41 adults with osteoporosis were recruited. Inertial sensors were attached to the skin over the lumbar and thoracic spines for recording the vibration transmitted during level walking. Vibration characteristics were compared across lumbar and thoracic spines and across groups.

Results

the lumbar spine generally amplified the vibration transmitted during walking, whereas the thoracic spine exhibited a much smaller amplification effect, except at the lowest frequency. The magnitude of vibration was generally reduced in the older spines. Osteoporosis had minimal effects on vibration transmission.

Conclusions

the larger amplification of vibration in the lumbar spine may explain the lower incidence of vertebral fractures in this region when compared to the thoracic spine. Ageing alters the transmission of vibration in the spine while osteoporosis has minimal effects. Future research should determine the characteristics of vibration transmitted through the thoracic spine during other physical activities.

Variability of the Pressure Measurements Exerted by the Tip of Laryngoscope During Laryngeal Sensory Testing: A Clinical Demonstration

PURPOSE

Clinicians often test laryngeal sensation by touching the laryngeal mucosa with the tip of a flexible laryngoscope. However, the pressure applied to the larynx by using this touch method is unknown, and the expected responses elicited by this method are uncertain. The variability in pressure delivered by clinicians using the touch method was investigated, and the subject responses to the touches were also reported.

METHODS

A fiberoptic pressure sensor passed through the working channel of a laryngoscope, with its tip positioned at the distal port of the channel. Two examiners each tested 8 healthy adults. Each examiner touched the mucosa covering the left arytenoid 3 times. The sensor recorded the pressure exerted by each touch. An investigator noted subject responses to the touches. From the recorded videos, the absence or presence of the laryngeal adductor reflex in response to touch was judged.

RESULTS

Pressure values obtained for 46 of the 48 possible samples ranged from 17.9 mmHg to the measurement ceiling of 350.0 mmHg. The most frequently observed response was positive subject report followed by the laryngeal adductor reflex.

CONCLUSION

Pressure applied to the larynx by using the touch method was highly variable, indicating potential diagnostic inaccuracy in determining laryngeal sensory function.

An MRI-Guided Telesurgery System Using a Fabry-Perot Interferometry Force Sensor and a Pneumatic Haptic Device

This paper presents a surgical master-slave teleoperation system for percutaneous interventional procedures under continuous magnetic resonance imaging (MRI) guidance. The slave robot consists of a piezoelectrically actuated 6-degree-of-freedom (DOF) robot for needle placement with an integrated fiber optic force sensor (1-DOF axial force measurement) using the Fabry-Perot interferometry (FPI) sensing principle; it is configured to operate inside the bore of the MRI scanner during imaging. By leveraging the advantages of pneumatic and piezoelectric actuation in force and position control respectively, we have designed a pneumatically actuated master robot (haptic device) with strain gauge based force sensing that is configured to operate the slave from within the scanner room during imaging. The slave robot follows the insertion motion of the haptic device while the haptic device displays the needle insertion force as measured by the FPI sensor. Image interference evaluation demonstrates that the telesurgery system presents a signal to noise ratio reduction of less than 17% and less than 1% geometric distortion during simultaneous robot motion and imaging. Teleoperated needle insertion and rotation experiments were performed to reach 10 targets in a soft tissue-mimicking phantom with 0.70 ± 0.35 mm Cartesian space error.

Automated Compression Device for Viscoelasticity Imaging

Noninvasive measurement of tissue viscoelastic properties is gaining more attention for screening and diagnostic purposes. Recently, measuring dynamic response of tissue under a constant force has been studied for estimation of tissue viscoelastic properties in terms of retardation times. The essential part of such a test is an instrument that is capable of creating a controlled axial force and is suitable for clinical applications. Such a device should be lightweight, portable, and easy to use for patient studies to capture tissue dynamics under external stress. In this paper, we present the design of an automated compression device for studying the creep response of materials with tissue-like behaviors. The device can be used to apply a ramp-and-hold force excitation for a predetermined duration of time and it houses an ultrasound probe for monitoring the creep response of the underlying tissue. To validate the performance of the device, several creep tests were performed on tissue-mimicking phantoms, and the results were compared against those from a commercial mechanical testing instrument. Using a second-order Kelvin-Voigt model and surface measurement of the forces and displacements, retardation times T1 and T2 were estimated from each test. These tests showed strong agreement between our automated compression device and the commercial mechanical testing system, with an average relative error of 2.9% and 12.4%, for T1 and T2, respectively. Also, we present the application of compression device to measure local retardation times for four different phantoms with different size and stiffness.

A Novel Wearable Apparatus to Measure Fingertip Forces in Manipulation Tasks Based on MEMS Barometric Sensors

Artificial tactile sensing is a challenging research topic in robotics, motor control, and rehabilitation engineering encompassing multi-disciplinary skills and different technologies. This paper presents the development of a wearable tactile thimble system using MEMS barometric sensors and flexible printed circuit board. Barometric sensors were carefully processed to make them able to transduce contact forces. Thumb, index, and medium fingers were equipped with an array of six sensing elements each, covering the central, lateral, and medial aspects of the fingertip. The sensor integration, signal read-out and processing, hardware architecture of the device, along with the calibration protocol, were described. The test results showed adequate sensitivity at very low forces with an almost linear transduction range up to about 4N (RMSE: 0.04N). Tests on object manipulation tasks highlighted the value of the proposed system demonstrating the ability of measuring both the force amplitude and contact points, demonstrating the suitability of barometric sensors for tactile applications.

Pavement type and wear condition classification from tire cavity acoustic measurements with artificial neural networks

Tire road noise is the major contributor to traffic noise, which leads to general annoyance, speech interference, and sleep disturbances. Standardized methods to measure tire road noise are expensive, sophisticated to use, and they cannot be applied comprehensively. This paper presents a method to automatically classify different types of pavement and the wear condition to identify noisy road surfaces. The methods are based on spectra of time series data of the tire cavity sound, acquired under normal vehicle operation. The classifier, an artificial neural network, correctly predicts three pavement types, whereas there are few bidirectional mis-classifications for two pavements, which have similar physical characteristics. The performance measures of the classifier to predict a new or worn out condition are over 94.6%. One could create a digital map with the output of the presented method. On the basis of these digital maps, road segments with a strong impact on tire road noise could be automatically identified. Furthermore, the method can estimate the road macro-texture, which has an impact on the tire road friction especially on wet conditions. Overall, this digital map would have a great benefit for civil engineering departments, road infrastructure operators, and for advanced driver assistance systems.

Diagnostic accuracy of a hybrid approach of instantaneous wave-free ratio and fractional flow reserve using high-dose intracoronary adenosine to characterize intermediate coronary lesions: Results of the PALS (Practical Assessment of Lesion Severity) prospective study

OBJECTIVES

We sought to investigate the diagnostic accuracy of instantaneous wave-free ratio (iFR) and high-dose intracoronary adenosine fractional flow reserve (IC-FFR) compared with classical intravenous adenosine fractional flow reserve (IV-FFR) to assess coronary stenosis severity. The usefulness of two hybrid strategies combining iFR and high-dose IC-FFR was also evaluated.

BACKGROUND

Physiological assessment of intermediate coronary stenoses to guide revascularization is currently recommended.

METHODS

Consecutive real-world patients with angiographically intermediate coronary stenosis (40-80% diameter stenosis) were prospectively included in the PALS (Practical Assessment of Lesion Severity) study. In every target lesion iFR, high-dose IC-FFR and IV-FFR were systematically measured to assess the accuracy of an hybrid sequential approach combining iFR and IC-FFR.

RESULTS

A total of 106 patients with 121 intermediate coronary lesions were analyzed. Both, iFR and IC-FFR showed a significant correlation with IV-FFR (iFR: r = 0.60, 95%CI 0.48-0.70; IC-FFR: r = 0.88; 95%CI: 0.83-0.92). High-dose IC-FFR provided lower FFR values than IV-FFR (0.81 ± 0.08 vs. 0.82 ± 0.09, P = 0.25). Using a receiver-operating-characteristic curve an optimal iFR threshold of 0.91 for the screening test was identified. A sequential test strategy (initial iFR followed by IC-FFR only in lesions with iFR <0.91) yielded an excellent diagnostic accuracy (96.7%, 95%CI 96.7-99.1%) with a sensitivity, specificity, positive and negative predicted values of 100%, 94.7%, 91.8%, and 100%, respectively. A hybrid approach using the previously described iFR gray zone (0.85-0.94) also provided an excellent diagnostic accuracy (95%, 95%CI: 89.5-98.1%).

CONCLUSIONS

In patients with intermediate coronary lesions a hybrid strategy by using a sequential approach of iFR and high-dose IC-FFR, provided a very good diagnostic performance to identify physiologically significant stenoses. © 2017 Wiley Periodicals, Inc.

A preliminary investigation into the design of pressure cushions and their potential applications for forearm robotic orthoses

BACKGROUND

Load cells are often used in rehabilitation robotics to monitor human-robot interaction. While load cells are accurate and suitable for the stationary end-point robots used in rehabilitation hospitals, their cost and inability to conform to the shape of the body hinder their application in developing affordable and wearable robotic orthoses for assisting individuals in the activities of daily living. This exploratory work investigates the possibility of using an alternative technology, namely compliant polymeric air cushions, to measure interaction forces between the user and a wearable rigid structure.

METHODS

A polymeric air cushion was designed, analyzed using a finite element model (FEM), and tested using a bench-top characterization system. The cushions underwent repeatability testing, and signal delay testing from a step response while increasing the length of the cushion's tubes. Subsequently, a 3D printed wrist brace prototype was integrated with six polymeric air cushions and tested in static conditions where a volunteer exerted isometric pronation/supination torque and forces in vertical and horizontal directions. The load measured by integrating data recorded by the six sensors was compared with force data measured by a high quality load cell and torque sensor.

RESULTS

The FEM and experimental data comparison was within the error bounds of the external differential pressure sensor used to monitor the pressure inside the cushion. The ratio obtained experimentally between the pressure inside the pressure cushion and the 8 N applied load deviated by only 1.28% from the FEM. A drift smaller than 1% was observed over 10 cycles. The rise times of the cushion under an 8 N step response for a 0.46, 1.03, and 2.02 m length tube was 0.45, 0.39, and 0.37 s. Tests with the wrist brace showed a moderate root mean square error (RMSE) between the force estimated by the pressure cushions and the external load cells. Specifically, the RMSE was 13 mNm, 500 mN, and 1.24 N for forearm pronation/supination torque, vertical force, and horizontal force, respectively.

CONCLUSIONS

The use of compliant pressure cushions was shown to be promising for monitoring interaction forces between the forearm and a rigid brace. This work lays the foundation for the future design of an array of pressure cushions for robotic orthoses. Future research should also investigate the compatibility of these polymeric cushions for data acquisition during functional magnetic resonance imaging in shielded rooms.

Shock formation and nonlinear saturation effects in the ultrasound field of a diagnostic curvilinear probe

Newer imaging and therapeutic ultrasound technologies may benefit from in situ pressure levels higher than conventional diagnostic ultrasound. One example is the recently developed use of ultrasonic radiation force to move kidney stones and residual fragments out of the urinary collecting system. A commercial diagnostic 2.3 MHz C5-2 array probe has been used to deliver the acoustic pushing pulses. The probe is a curvilinear array comprising 128 elements equally spaced along a convex cylindrical surface. The effectiveness of the treatment can be increased by using higher transducer output to provide a stronger pushing force; however nonlinear acoustic saturation can be a limiting factor. In this work nonlinear propagation effects were analyzed for the C5-2 transducer using a combined measurement and modeling approach. Simulations were based on the three-dimensional Westervelt equation with the boundary condition set to match low power measurements of the acoustic pressure field. Nonlinear focal waveforms simulated for different numbers of operating elements of the array at several output power levels were compared to fiber-optic hydrophone measurements and were found to be in good agreement. It was shown that saturation effects do limit the acoustic pressure in the focal region of a diagnostic imaging probe.

Assessment of trans-aortic pressure gradient using a coronary pressure wire in patients with mechanical aortic and mitral valve prostheses

Accurate evaluation of trans-aortic valvular pressure gradients is challenging in cases where dual mechanical aortic and mitral valve prostheses are present. Non-invasive Doppler echocardiographic imaging has its limitations due to multiple geometric assumptions. Invasive measurement of trans-valvular gradients with cardiac catheterization can provide further information in patients with two mechanical valves, where simultaneous pressure measurements in the left ventricle and ascending aorta must be obtained. Obtaining access to the left ventricle via the mitral valve after a trans-septal puncture is not feasible in the case of a concomitant mechanical mitral valve, whereas left ventricular apical puncture technique is associated with high procedural risks. Retrograde crossing of a bileaflet mechanical aortic prosthesis with standard catheters is associated with the risk of catheter entrapment and acute valvular regurgitation. In these cases, the assessment of trans-valvular gradients using a 0.014˝ diameter coronary pressure wire technique has been described in a few case reports. We present the case of a 76-year-old female with rheumatic valvular heart disease who underwent mechanical aortic and mitral valve replacement in the past. She presented with decompensated heart failure and echocardiographic findings suggestive of elevated pressure gradient across the mechanical aortic valve prosthesis. The use of a high-fidelity 0.014˝ diameter coronary pressure guidewire resulted in the detection of a normal trans-valvular pressure gradient across the mechanical aortic valve. This avoided a high-risk third redo valve surgery in our patient. © 2017 Wiley Periodicals, Inc.

Source levels and call parameters of harbor seal breeding vocalizations near a terrestrial haulout site in Glacier Bay National Park and Preserve

Source levels of harbor seal breeding vocalizations were estimated using a three-element planar hydrophone array near the Beardslee Islands in Glacier Bay National Park and Preserve, Alaska. The average source level for these calls was 144 dB_RMS re 1 μPa at 1 m in the 40-500 Hz frequency band. Source level estimates ranged from 129 to 149 dB_RMS re 1 μPa. Four call parameters, including minimum frequency, peak frequency, total duration, and pulse duration, were also measured. These measurements indicated that breeding vocalizations of harbor seals near the Beardslee Islands of Glacier Bay National Park are similar in duration (average total duration: 4.8 s, average pulse duration: 3.0 s) to previously reported values from other populations, but are 170-220 Hz lower in average minimum frequency (78 Hz).

Automated setup for ex vivo larynx experiments

Ex vivo larynx experiments are limited in time due to degeneration of the laryngeal tissues. In order to acquire a significant and comparable amount of data, automatization of current manual experimental procedures is desirable. A computer controlled, electro-mechanical setup was developed for time-dependent variation of specific physiological parameters, including adduction and elongation level of the vocal folds and glottal flow. The setup offers a standardized method to induce defined forces on the laryngeal cartilages. Furthermore, phonation onset is detected automatically and the subsequent measurement procedure is automated and standardized to improve the efficiency of the experimental process. The setup was validated using four ex vivo porcine larynges, whereas each validation measurement series was executed with one separate larynx. Altogether 31 single measurements were undertaken, which can be summed up to a total experimental time of about 4 min. Vocal fold elongation and adduction lead both to an increase in fundamental frequency and subglottal pressure. Measurement procedures like applying defined subglottal pressure steps and onset-offset detection were reliably executed. The setup allows for a computer-based parameter control, which enables fast experimental execution over a wide range of laryngeal configurations. This maximizes the number of measurements and reduces personal effort compared with manual procedures.

Social sounds produced by franciscana dolphins, Pontoporia blainvillei (Cetartiodactyla, Pontoporiidae)

Franciscana dolphin (Pontoporia blainvillei) whistles were documented for the first time during 2003-2013 in Babitonga Bay estuary, South Brazil, together with burst pulses. Recordings were made from small boats under good sea conditions, and recording equipment that allowed analysis of sounds up to 96 kHz. The recordings were made in the presence of 2-31 franciscana dolphins. During 23 h and 53 min, 90 whistles and 51 burst pulse series were recorded. Although Guiana dolphins (Sotalia guianensis) inhabit nearby waters, none were observed in the area during the recordings. The authors recorded ten types of whistles. The initial frequency varied between 1.6 and 94.6 kHz, and the final frequency varied between 0.7 and 94.5 kHz; the authors were not able to determine if dolphin whistles exceeded the 96 kHz recording limit of the authors' equipment, although that is likely, especially because some whistles showed harmonics. Whistle duration varied between 0.008 and 0.361 s. Burst pulses had initial frequencies between 69 and 82.1 kHz (77 ± 3.81). These results showed that P. blainvillei produces whistles and burst pulses, although they seem to be produced infrequently.

Influence of the marvelous™ three-way stopcock on the natural frequency and damping coefficient in blood pressure transducer kits

Two types of Planecta™ ports are commonly used as sampling ports in blood pressure transducer kits: a flat-type port (FTP) and a port with a three-way stopcock (PTS). Recently, a new type of three-way stopcock (Marvelous™) has been released as a Planecta™ counterpart, but its effects on the frequency characteristics and reliability of blood pressure monitoring have not been investigated. We assessed the influence of the Marvelous™ stopcock on the frequency characteristics of the pressure transducer kit. The basic pressure transducer kit, DT4812J, was modified by replacing one or two of the original three-way stopcocks with Marvelous™ stopcocks. The frequency characteristics (i.e., natural frequency and damping coefficient) of each kit were determined using wave parameter analysis software, and subsequently evaluated on a Gardner chart. Replacement of the original blood pressure transducer kit stopcocks with Marvelous™ stopcocks decreased the natural frequency (48.3 Hz) to 46.3 Hz or 44.8 Hz, respectively; the damping coefficient was not significantly changed. Plotting the data on a Gardner chart revealed that the changes fell within the adequate dynamic response region, indicating they were within the allowable range. Insertion of Marvelous™ stopcocks slightly affects the natural frequency of the pressure transducer kit, similar to inserting a PTS. The results indicate that the Marvelous™ stopcock is useful for accurate monitoring of arterial blood pressure, and may be recommended when insertion of two or more closed-loop blood sampling systems is necessary.

Evaluation of knee joint forces during kneeling work with different kneepads

The main purpose of this study is to determine knee joint forces resulting from kneeling work with and without kneepads to quantify how different kneepads redistribute force. Eleven healthy males simulated a tile setting task to different locations during six kneepad states (five different kneepad types and without kneepad). Peak and average forces on the anatomical landmarks of both knees were obtained by custom force sensors. The results revealed that kneepad design can significantly modify the forces on the knee joint through redistribution. The Professional Gel design was preferred among the five tested kneepads which was confirmed with both force measurements and participants' responses. The extreme reaching locations induced significantly higher joint forces on left knee or right knee depending on task. The conclusion of this study is that a properly selected kneepad for specific tasks and a more neutral working posture can modify the force distribution on the knees and likely decrease the risk of knee disorders from kneeling work.

Comparing otoacoustic emissions evoked by chirp transients with constant absorbed sound power and constant incident pressure magnitude

Human ear-canal properties of transient acoustic stimuli are contrasted that utilize measured ear-canal pressures in conjunction with measured acoustic pressure reflectance and admittance. These data are referenced to the tip of a probe snugly inserted into the ear canal. Promising procedures to calibrate across frequency include stimuli with controlled levels of incident pressure magnitude, absorbed sound power, and forward pressure magnitude. An equivalent pressure at the eardrum is calculated from these measured data using a transmission-line model of ear-canal acoustics parameterized by acoustically estimated ear-canal area at the probe tip and length between the probe tip and eardrum. Chirp stimuli with constant incident pressure magnitude and constant absorbed sound power across frequency were generated to elicit transient-evoked otoacoustic emissions (TEOAEs), which were measured in normal-hearing adult ears from 0.7 to 8 kHz. TEOAE stimuli had similar peak-to-peak equivalent sound pressure levels across calibration conditions. Frequency-domain TEOAEs were compared using signal level, signal-to-noise ratio (SNR), coherence synchrony modulus (CSM), group delay, and group spread. Time-domain TEOAEs were compared using SNR, CSM, instantaneous frequency and instantaneous bandwidth. Stimuli with constant incident pressure magnitude or constant absorbed sound power across frequency produce generally similar TEOAEs up to 8 kHz.

Investigation of low back and shoulder demand during cardiopulmonary resuscitation

Limited research has examined the effect of different compression-ventilation ratios on the ergonomic demand of performing cardiopulmonary resuscitation (CPR) over time. This study aimed to compare the biomechanical demand of performing continuous chest compression CPR (CCC-CPR) and standard CPR (30:2 compression to breath ratio). Fifteen CPR certified individuals performed both standard CPR and CCC-CPR, randomly assigned, for three 2-min periods. Trunk and upper limb muscle activation, lumbar spine posture and compression force applied to a testing mannequin chest were measured throughout each CPR trial. No differences in muscle activation of spine posture were observed, however chest compression force decreased over the two minutes (p < 0.0001). Further, this drop in force was larger and initiated immediately during the CCC-CPR trials. This immediate drop in force during the CCC-CPR trials may be an anticipatory adjustment in order to be able to sustain continuous compressions for the full 2 min duration.

Direct Measurement of Left Atrial Pressure during Routine Transradial Catheterization

Left atrial pressure indicates the left ventricular filling pressure in patients who have systolic or diastolic left ventricular dysfunction or valvular heart disease. The use of indirect surrogate methods to determine left atrial pressure has been essential in the modern evaluation and treatment of cardiovascular disease because of the difficulty and inherent risks associated with direct methods (typically the transseptal approach). One method that has been widely used to determine left atrial pressure indirectly is Swan-Ganz catheterization, in which a balloon-flotation technique is applied to measure pulmonary capillary wedge pressure; however, this approach has been associated with several limitations and potential risks. Measuring left ventricular end-diastolic pressure has also been widely used as a simple means to estimate filling pressures but remains a surrogate for the gold standard of directly measuring left atrial pressure. We describe a simple, low-risk method to directly measure left atrial pressure that involves the use of standard coronary catheterization techniques during a transradial procedure.

Real-world use of fractional flow reserve in Germany: results of the prospective ALKK coronary angiography and PCI registry

BACKGROUND

There is growing evidence for beneficial prognostic and economic effects of FFR-guided treatment of stable coronary artery disease. We sought to evaluate the real-world use of FFR measurements in patients undergoing elective coronary angiography.

METHODS AND RESULTS

We analyzed the data of the prospective ALKK coronary angiography and PCI registry including data of 38 hospitals from January 2010 to December 2013. A total of 100,977 patients undergoing coronary angiography were included. In 3240 patients (3.2 %) intracoronary pressure measurement was performed. There was a wide range of use of FFR measurement in the different analyzed ALKK hospitals from 0.1 to 8.8 % in elective patients with suspected or known coronary artery disease (median 2.7 %, quartiles 0.9 and 5.3 %), with a successive increase of use over time during the study period. Overall, it was performed in 3.2 % of coronary angiographies. Use in patients with three-vessel disease (2.5 %) and recommendation for bypass surgery (1.6 %) was less frequent. In procedures without PCI, dose area product was higher in the FFR group (2641 cGy × cm² vs. 2368 cGy × cm², p < 0.001), while it was lower in procedures with ad hoc PCI (4676 cGy × cm² vs. 5143 cGy × cm², p < 0.001). The performing center turned out to be the strongest predictor.

CONCLUSIONS

The use of FFR measurement was very heterogeneous between different hospitals and in general relatively low, in particular in patients with multivessel disease or recommendation for bypass surgery, but there was a positive trend during the study period. Technically, FFR measurement was not associated with an increased periprocedural complication rate.

Esophageal Rings and Strictures: Manometric characteristics in patients with food impaction

Purpose: The purpose was to investigate the manometric characteristics in patients with lower esophageal rings or strictures with special reference to food impaction.

Material and Methods: The material comprised 344 patients (158 female and 186 male). Lower esophageal rings or strictures were diagnosed radiologically by the full column technique. Manometry was performed with triple lumen catheters connected to a hydraulic capillary system and external transducers.

Results: Forty patients had rings, and 21 patients strictures. The reference group comprised 283 patients. Dysphagia was seen most frequently in patients with rings. Food impaction was seen only in patients with rings or strictures, whereas chest pain and heartburn appeared with the same incidence in all 3 groups. Non-specific motor disorders were seen most frequently in patients with strictures, but as delayed esophageal emptying with no influence on the tendency to food impaction. Only ring diameter, but not stricture diameter, was of any significance with a higher incidence of food impaction in patients with narrow rings.

Conclusion: Radiology rather than manometry should be the first diagnostic step in patients with benign dysphagia suffering from food impaction.

Glottic Closing Force: Impact of Thyroplasty on Vocal Cord Paralysis in a Pig Model

Reflex glottic closure is an essential component of a normal swallow. A lesion of the unilateral recurrent laryngeal nerve weakens this reflex response, affecting the essential protective functions of the larynx and potentially resulting in aspiration pneumonia, sepsis, or death. Thyroplasty has been advocated to reduce glottic incompetence due to unilateral vocal cord paralysis (UVCP). Although medialization thyroplasty has traditionally been evaluated in terms of its phonatory effect, its role in improving protective glottic closure has never been studied. The present study was designed to evaluate the effect of UVCP and thyroplasty type I on the glottic closing force (GCF). Five male Yorkshire pigs weighing approximately 40 kg were used in this study. Both internal superior laryngeal nerves were simultaneously stimulated with bipolar platinum-iridium electrodes, and the force of evoked glottic closure was measured with a pressure transducer positioned between the vocal cords. Initial pressure readings (GCF) obtained with bilaterally intact recurrent laryngeal nerves served as a control. The GCF was then measured after the right recurrent laryngeal nerve was sectioned to simulate the conditions of UVCP. Finally, thyroplasty type I was performed on the affected side, and the GCF was measured again to evaluate its quantitative effect on reflex glottic closure. The mean GCF was reduced by UVCP to approximately 22.5% (49.71 mm Hg) of the control GCF (220.25 mm Hg). Thyroplasty enhanced the GCF to 57.7% (127.08 mm Hg) of the control GCF. These measures underscore the profound effect that UVCP exerts on the GCF and the limitations of vocal cord medialization in fully restoring it.

Aneurysm Sac Pressure Measurement with a Pressure Sensor in Endovascular Aortic Aneurysm Repair

Aortic endograft surveillance is a necessity for the lifetime of a patient owing to the risk of endoleaks and device complications. The current standard of care for surveillance is radiologic imaging. The most commonly used modality is computed tomographic angiography. Magnetic resonance angiography and ultrasonography have also been used as surveillance tools. These imaging techniques have risks and limitations, and alternative surveillance tools are being investigated. Remote pressure sensing is a promising technology that can provide adjunctive support to the current imaging modalities. The technology is applicable to both abdominal and thoracic endograft implantation and surveillance. It has recently gained clearance from the US Food and Drug Administration for acute aneurysm exclusion during an abdominal endograft insertion. As more data are accumulated, it may be possible for remote pressure sensing to replace current imaging techniques as the sole modality for endograft surveillance.

A bio-inspired real-time capable artificial lateral line system for freestream flow measurements

To enhance today's artificial flow sensing capabilities in aerial and underwater robotics, future robots could be equipped with a large number of miniaturized sensors distributed over the surface to provide high resolution measurement of the surrounding fluid flow. In this work we show a linear array of closely separated bio-inspired micro-electro-mechanical flow sensors whose sensing mechanism is based on a piezoresistive strain-gauge along a stress-driven cantilever beam, mimicking the biological superficial neuromasts found in the lateral line organ of fishes. Aiming to improve state-of-the-art flow sensing capability in autonomously flying and swimming robots, our artificial lateral line system was designed and developed to feature multi-parameter freestream flow measurements which provide information about (1) local flow velocities as measured by the signal amplitudes from the individual cantilevers as well as (2) propagation velocity, (3) linear forward/backward direction along the cantilever beam orientation and (4) periodicity of pulses or pulse trains determined by cross-correlating sensor signals. A real-time capable cross-correlation procedure was developed which makes it possible to extract freestream flow direction and velocity information from flow fluctuations. The computed flow velocities deviate from a commercial system by 0.09 m s(-1) at 0.5 m s(-1) and 0.15 m s(-1) at 1.0 m s(-1) flow velocity for a sampling rate of 240 Hz and a sensor distance of 38 mm. Although experiments were performed in air, the presented flow sensing system can be applied to underwater vehicles as well, once the sensors are embedded in a waterproof micro-electro-mechanical systems package.