Electronic Pressure Transducer Research Articles

Invasive validation of central blood pressure measurements using a suprasystolic monitor

Abstract Interest in the assessment of Central Blood Pressure (cBP) is steadily growing since it is a better predictor of myocardial infarction, stroke, or death than Peripheral Blood Pressure (pBP). However, pBP remains the first line for the diagnosis of hypertension (HTN) due to the ease and speed of the measurement. We sought to validate a new method to estimate cBP from brachial sphygmomanometer measurements. We estimated cBP using a sphygmomanometer that can record, after conventional pBP measurements, the pressure in the cuff maintained at a constant suprasystolic pressure. cBP is calculated using a method based on applying a physics-based model of the left subclavian artery to the brachial arterial branch to the suprasystolic brachial artery pressure waveforms. We compared this noninvasive estimated cBP to an invasive gold-standard measurement during cardiac catheterization. After clinically indicated cardiac catheterization requiring a haemodynamic assessment of a moderate coronary artery stenosis by Fractional Flow Reserve (FFR), the wire that incorporates a high fidelity electronic pressure transducer was positioned into the guiding catheter left in the ascending aorta. Simultaneous measurements were performed with a cuff placed on the patient's left arm. The output signals were recorded in a custom-based acquisition system. The comparison was obtained on the same 10 seconds recorded by the cuff and the pressure wire. The goal will be to reach 85 patients as recommended by the ARTERY Society Task Force. It recommends as an accuracy criterion to achieve a mean difference ≤ 5 mmHg with a standard deviation (SD) ≤ 8 mmHg, which are the standards adopted for this study. Patients with aortic stenosis, atrial fibrillation, or frequent (supra)ventricular extrasystoles were excluded. A total of 197 pairs of measured-estimated cBP were analysed in 78 patients with a mean age of 63 ± 8 yo, 75% of whom were men, 70% had hypertension, 26% fdiabetes, 93% dyslipidemia, 41% were tobacco users and 14% suffered from clinical peripheral artery diseases without history of revascularization. The median (InterQuartiles 25-75%) pBP was 123 [112 134] / 70 [64 77] mmHg. Measured cBP was 102 [92 11] / 78 [70 84] mmHg with a central augmentation index of 34 [23 44] %. The mean difference between estimated and measured systolic cBP was 4.9 ± 6.5 mmHg, while it was -3.9 ± 5.8 mmHg for diastolic cBP, meeting the prespecified accuracy criteria. In conclusion, our approach based on an exact matching and comparison of non-invasive suprasystolic arm cuff measurements and high-fidelity aortic BP validates that an estimation of central aortic blood pressure that can be easily carried out in daily practice and might improve HTN management. It remains to be demonstrated that more cardiovascular complications will be avoided by guiding the antihypertensive therapy with cBP instead of pBP measurements.Bland-Altman of estimated - measured cBP

EXPERIMENTAL AND NUMERICAL EVALUATION OF AN IN-FLIGHT ANGLE OF ATTACK MEASUREMENT SYSTEM FOR HIGH POWER MODEL ROCKETS

The angle of attack (α) affects the drag, flight path, and flight stability during rocket ascent. This work proposes an in-flight α measurement system based on pressure measurements at the surface of the nosecone for low apogee rockets. An electronic micro differential pressure transducer was selected to measure the pressure difference between selected points in the rocket’s nosecone. Wind tunnel tests were performed to correlate the α with the sensor output at low Mach numbers (Ma ≃ 0.08). The experimental results were further used as a reference for the construction of CFD models of the external flow in the rocket’s nosecone with the aim of predicting the measurements in an extended Mach number range (up to Ma ≃ 0.7). The numerical results allowed for an extended model correlating α with the differential pressure transducer output (Ch). The estimate of model’s errors completes the analysis.

Differential-pressure fiber-optic airflow sensor for wind tunnel testing.

A differential-pressure fiber-optic airflow (DPFA) sensor based on Fabry-Perot (FP) interferometry for wind tunnel testing is proposed and demonstrated. The DPFA sensor can be well coupled with a Pitot tube, similar to the operation of the differential diaphragm capsule in the airspeed indicator on the aircraft. For differential pressure sensing between total pressure and static pressure in the airflow, an FP cavity is formed between the sensing diaphragm and a fiber end-face, and a tubule is inserted into the FP cavity. According to the principle of differential pressure derived from Bernoulli's equation, the airflow velocity can be determined by monitoring the change of the FP cavity length. The experimental results demonstrate that a DPFA sensor with 0∼11 kPa measurable range, 826.975 nm/kPa sensitivity, and 0.008% (0.89 Pa) resolution can be realized. Combined with a 100 Hz-sweep frequency self-developed white light interferometric (WLI) interrogator and a Pitot tube, the DPFA sensor can be used for measuring the airflow velocity of 2.0∼119.24 m/s with an accuracy of 0.61%. The system is applied to the analysis of the flat-plate boundary layer, a wind tunnel experimental model, where the results are consistent with those of the theoretical analysis and from the standard electronic pressure transducer. With the large measurable range, high sweep frequency, and high precision, the system has potential application value for wind tunnel experimental investigation and in-flight measurement of airspeed.

Feasibility of a Portable Abdominal Insufflation Device for Controlling Intraperitoneal Bleeding After Abdominal Blunt Trauma.

Uncontrolled bleeding contributes to 30% to 40% of trauma-related deaths and is the leading cause of potentially preventable deaths. Currently, there is no effective method available to first responders for temporary control of noncompressible intraabdominal bleeding while patients are transported to the hospital. Our previous studies demonstrated that abdominal insufflation provides effective temporary bleeding control. The study aims to prove the feasibility (insufflation to a target pressure) and safety (cardiovascular and respiratory effects) of a novel portable abdominal insufflation device (PAID) designed to control the intraperitoneal bleeding caused by abdominal trauma. The PAID prototype is based on a patented design and manufactured via additive manufacturing. PAID contains a 16-g CO2 cartridge and an electronic pressure transducer. PAID was tested on a bench top and a swine animal model. For the animal model study, the intraperitoneal pressure as well as cardiorespiratory parameters (hearth rate, SpO2 [peripheral capillary oxygen saturation], and blood pressure) were continuously monitored during the insufflation procedure. The prototype functioned according to specifications on both bench top and animal models. CO2 insufflation of the peritoneal cavity was delivered up the target 20 mm Hg and maintained for 30 minutes from 1 or 2 cartridges in the swine model. No intraoperative incidents were registered, and all the recorded physiological parameters were within normal limits. The PAID prototype is a feasible, easy to use device that provides quick, controlled, and safe insufflation of the peritoneal cavity. Future studies will focus on testing the next-generation, semiautomatic PAID prototype in a severe intraabdominal injury model.

Retinal venous pressure is higher than the airway pressure and the intraocular pressure during the Valsalva manoeuvre.

The aims of this prospective experimental study were to explore the influence of the Valsalva manoeuvre (VM) on retinal venous pressure (RVP) in human volunteers in a university setting and to establish correlations for RVP with the increase in airway pressure (∆AirP) and in intraocular pressure (∆IOP). In total, 31 healthy young volunteers (age: 24±1.7years) were investigated. The instruments used included a dynamic contour tonometer, a contact lens dynamometer (Imedos) and an electronic pressure transducer for measuring airway pressure. The following measurements were successively performed in left eyes: tonometry, dynamometry, repeated simultaneous dynamometry and airway pressure measurement during the VM and tonometry during the VM. The pressures obtained during the VM were determined at 10, 20 and 30seconds after onset of the VM by linear interpolation. The pressures (in mmHg) at baseline and during the VM (median and range with outliers) were as follows: ∆AirP: 10seconds: 10.0 (7.5); 20seconds: 12.5 (11.0); and 30seconds: 11.0 (10.0); and RVP: Start: 17.1 (2.4); 10seconds: 26.0 (7.5); 20seconds: 25.0 (6.5); and 30seconds: 24.0 (6.0). During the VM, the RVP was significantly increased compared with the ∆AirP (p=0.0017). The IOP during the VM was 13.5 (2.7), and the increase in IOP (∆IOP) was 0.8 (5.6). During the VM, the RVP was increased compared with the ∆AirP. The increase in RVP (∆RVP) was significantly greater than the ∆IOP. During the VM, the calculated retinal perfusion pressure may be more strongly reduced by the ∆RVP than by the ∆IOP. These properties may influence retinal and optic nerve head pathophysiology.

Measurement and analysis of the water hammer in ram pump

This paper presents the results of experimental research of the phenomena occurring in water ram during a single cycle of its operation. Apart from a brief introduction and description of the test stand and data recording system, the work includes a broad interpretation of the obtained results. Based on the pressure waveforms recorded in two characteristic zones of the device and its detailed analysis, the single cycle of water ram is divided into three main stages: acceleration, pumping, and backflow. The waveforms of phenomena in each of these steps were considered separately. In discussion, some of the issues were supported with additional measurements, including Fourier analysis of signals from the electronic pressure transducers. The main topic of discussion based on the results recorded for the impulse valve, is supplemented by the comments that take into account the results obtained for the impulse valve (flap check valve) and for the others two (self-made) impulse valves. In the final part, in a graphic form presented is the interpretation of the phenomena occurring during one work cycle of water ram. The motivation of this work was to supplement the knowledge concerning the water hammer waveform in ram pump.

A low-cost electronic tensiometer system for continuous monitoring of soil water potential

A low cost system for measuring soil water potential and data logging was developed on the basis of an Arduino microcontroller board, electronic pressure transducers and water-filled tensiometers. The assembly of this system requires only minimal soldering, limited to the wiring of the power supply and the pressure sensors to the microcontroller board. The system presented here is, therefore, not only inexpensive, but also suited for easy reproduction by users with only basic technical skills. The utility and reliability of the system was tested in a commercial apple orchard.

A low-cost electronic tensiometer system for continuous monitoring of soil water potential

A low cost system for measuring soil water potential and data logging was developed on the basis of an <em>Arduino</em> microcontroller board, electronic pressure transducers and water-filled tensiometers. The assembly of this system requires only minimal soldering, limited to the wiring of the power supply and the pressure sensors to the microcontroller board. The system presented here is, therefore, not only inexpensive, but also suited for easy reproduction by users with only basic technical skills. The utility and reliability of the system was tested in a commercial apple orchard.

A clinical comparison between a non–invasive blood pressure monitor using high definition oscillometry (Memodiagnostic MD 15/90 Pro) and invasive arterial blood pressure measurement in anaesthetized dogs

ObjectiveTo compare high definition oscillometry (HDO) to invasive blood pressure measurement in anaesthetized dogs. Study designProspective, clinical trial. AnimalsFifty dogs weighing 1.95–79 kg (mean 23.5 kg). Materials and methodsAnaesthetic and peri–anaesthetic management was chosen according to each dog's physical status and anaesthetist's preference. Direct arterial blood pressure measurements were performed using a catheter placed in the dorsal pedal artery and an electronic pressure transducer connected to a multiparameter monitor. Non–invasive blood pressure measurements were performed using an appropriately sized cuff placed around the tail base. Comparisons between the two methods were made using Bland and Altman plots. The data are reported as mean bias (lower, upper limits of agreement). Further analysis was performed after separating the data into the following categories based on invasive mean arterial blood pressure (MAP): high (MAP > 100 mmHg), medium (70 mmHg < MAP < 100 mmHg) and low (MAP < 70 mmHg) blood pressure (BP). The two methods were compared as used clinically. ResultsEight hundred measurement pairs for invasive and HDO BP readings were compared. Overall, the HDO measured lower values for SAP and DAP but higher for MAP than the invasive method. The lowest bias (upper, lower limits of agreement) were obtained for MAP, −1 (−22, 19) mmHg. The biggest discrepancy between the methods was reflected by a large bias (limits of agreement) 5 (−34, 45) mmHg, was for SAP. The results for DAP were between those for SAP and MAP with a bias (limits of agreement) of 3 (−20, 27) mmHg. When the values were separated into the pressure range categories the HDO measured higher in the high, medium and low BP groups, with the exception of SAP in the low BP group. ConclusionsWhen considering the mean bias, the accuracy of HDO compared well with direct arterial blood pressure, but the precision was poor, as determined by wide limits of agreement. Clinical relevanceUsing trends and serial measurements rather than a single measurement for clinical decision making is recommended with both methods, when used as reported here.

Spontaneous shutoff of desflurane vaporizer

To the Editor: We would like to report the intraoperative failure of a desflurane vaporizer. The incident occurred as a 57-yearold man underwent parathyroid surgery. After induction and intubation, anesthesia was maintained with 5 % inhaled desflurane, using a Tec 6 Plus vaporizer (GE Healthcare Japan Co., Tokyo, Japan), via a semiclosed circuit with a 3 l/min fresh gas flow. Approximately 7 min into the case, the ‘‘no output’’ vaporizer alarm sounded and the desflurane concentration in the anesthesia circuit began to fall. We immediately turned off the vaporizer. After several seconds, the vaporizer automatically reset but within several minutes, the ‘‘no output’’ error occurred again. The surgery was then completed using sevoflurane, without assessing the depth of anesthesia. The patient emerged from anesthesia uneventfully, with no recollection of the intraoperative events. We purchased the vaporizer 2 months prior to the incident; it was used almost every day for 2 months. Although clinical engineers and anesthesiologists maintain anesthetic machines and circuits, vaporizers are not inspected usually in our operating rooms. According to the manufacturer’s technical department, 10 incidences of initial failure have been confirmed in 431 products since the vaporizer’s 2011 release in Japan. The vaporizer was exchanged at no charge following this initial failure. Afterward, the manufacturer reported to us that the failure of an electronic pressure transducer caused this incident. They recommended the immediate use of alternative anesthetics if the ‘‘no output’’ error recurred. Reports of spontaneous shutoff during surgery of a correctly mounted desflurane vaporizer have not previously been published [1–3]. Unlike conventional mechanical vaporizers, the desflurane vaporizer has sophisticated electronic components. As a fail-safe, it completely halts agent output if an electronic failure occurs. Since the washout for desflurane is more rapid than that for other inhalation agents, patients emerge from anesthesia soon after shutoff of the vaporizer. The incidence of initial failure reported by the manufacturer seems relatively high. This case serves to emphasize the importance of fully understanding the features of equipment that is in frequent use [4].

Macro-mechanical modeling of blast-wave mitigation in foams. Part II: reliability of pressure measurements

A phenomenological study of the process occurring when a plane shock wave reflected off an aqueous foam column filling the test section of a vertical shock tube has been undertaken. The experiments were conducted with initial shock wave Mach numbers in the range \(1.25\le {M}_\mathrm{s} \le 1.7\) and foam column heights in the range 100–450 mm. Miniature piezotrone circuit electronic pressure transducers were used to record the pressure histories upstream and alongside the foam column. The aim of these experiments was to find a simple way to eliminate a spatial averaging as an artifact of the pressure history recorded by the side-on transducer. For this purpose, we discuss first the common behaviors of the pressure traces in extended time scales. These observations evidently quantify the low frequency variations of the pressure field within the different flow domains of the shock tube. Thereafter, we focus on the fronts of the pressure signals, which, in turn, characterize the high-frequency response of the foam column to the shock wave impact. Since the front shape and the amplitude of the pressure signal most likely play a significant role in the foam destruction, phase changes and/or other physical factors, such as high capacity, viscosity, etc., the common practice of the data processing is revised and discussed in detail. Generally, side-on pressure measurements must be used with great caution when performed in wet aqueous foams, because the low sound speed is especially prone to this effect. Since the spatial averaged recorded pressure signals do not reproduce well the real behaviors of the pressure rise, the recorded shape of the shock wave front in the foam appears much thicker. It is also found that when a thin liquid film wet the sensing membrane, the transducer sensitivity was changed. As a result, the pressure recorded in the foam could exceed the real amplitude of the post-shock wave flow. A simple procedure, which allows correcting this imperfection, is discussed in detail.

Laboratory analysis of phacoemulsifier compliance and capacity

To compare the compliance and capacity of 7 fluidics modules used by 6 phacoemulsifiers from 3 manufacturers. Jules Stein Eye Institute, Los Angeles, California, USA. Experimental study. Previous-model and current-model phacoemulsifiers from 3 manufacturers were subjected to laboratory analysis of compliance and capacity. Previous-generation models tested included the Legacy Advantec, Whitestar Sovereign Phacoemulsification System, and Millennium Microsurgical System. Current models tested were the Infiniti Vision System with standard and Intrepid cassettes, Whitestar Signature Phacoemulsification System, and Stellaris Vision Enhancement System. To measure compliance, the aspiration line was connected to an electronic pressure transducer and small volumes of fluid were injected or aspirated. To measure capacity, the space between the distal end of the aspiration line and the pump was filled with methylene blue-dyed fluid. The Legacy was the most compliant phacoemulsifier. The old and new Whitestar systems, Millennium system, and Stellaris system showed similar midrange compliances. The Infiniti Vision System with the Intrepid fluidic management system was the least compliant. The Infiniti cassettes had the greatest capacity, which is a detriment from a surge-control perspective, and Signature cassettes had the least capacity. The Infiniti Intrepid system had the lowest compliance of the 6 units tested, which is optimum from a surge-control perspective. All other things being equal, the Infiniti should have the safest occlusion-break surge response. Mr. Injev is an employee of Alcon Laboratories. Dr. Miller is a consultant to and investigator for Alcon Laboratories. Ms. Nejad has no financial or proprietary interest in any material or method mentioned.

Reliability of the Conditioned Pain Modulation Paradigm to Assess Endogenous Inhibitory Pain Pathways

Conditioned pain modulation paradigms are often used to assess the diffuse noxious inhibitory control (DNIC) system. DNICs provide one of the main supraspinal pain inhibitory pathways and are impaired in several chronic pain populations. Only one previous study has examined the psychometric properties of the conditioned pain modulation technique and this study did not evaluate intersession reliability. To evaluate and compare the intra- and intersession reliability of two conditioned pain modulation paradigms using different conditioning stimuli, and to determine the time course of conditioned pain inhibition following stimulus removal. An electronic pressure transducer was used to determine the pressure-pain threshold at the knee during painful conditioning of the opposite hand using the ischemic arm test and the cold pressor test. Assessments were completed twice on one day and repeated once approximately three days later. The two conditioning stimuli resulted in a similar increase in the pressure-pain threshold at the knee, reflecting presumed activation of the DNIC system. Intrasession intraclass correlation coefficients for the cold pressor (0.85) and ischemic arm tests (0.75) were excellent. The intersession intraclass correlation coefficient for the cold pressor test was good (0.66) but was poor for the ischemic arm test (-0.4). Inhibition of the pressure-pain threshold remained significant at 10 min following conditioning, but returned to baseline by 15 min. Within-session reliability of DNIC assessment using conditioned pain modulation paradigms was excellent, but the applicability of assessing pain modulation over multiple sessions was influenced by the conditioning stimulus. The cold pressor test was the superior technique.

The use of an acoustic device to identify the extradural space in standing horses

ObjectiveTo determine the usefulness of an acoustic device to confirm correct placement of extradural needles in horses. Study designProspective experimental study. AnimalsTwelve adult healthy horses weighing between 434 and 640 kg. Materials and methodsHorses were sedated, placed in stocks and subjected to caudal extradural anaesthesia using lidocaine 2%. For extradural puncture an 18 gauge Tuohy needle connected to an acoustic device via an electronic pressure transducer was used. This device allowed recording of the extradural pressure profile and the transformation of pressure changes into an audible signal. Extradural needle advancement was stopped and the local anaesthetic administered when either a sharp decrease in sound pitch occurred or a ‘pop’ sensation was felt. Correct needle placement was assessed clinically by the degree of extradural anaesthesia present using needle prick stimuli, loss of tail tone and occurrence of localized sweating. Descriptive statistical analysis was used for evaluation of the data. ResultsExtradural anaesthesia was successful in nine of 12 horses. In these horses during extradural needle advancement the pitch of the audible signal first increased and abruptly changed to a constant low pitched sound. In the three horses with unsuccessful punctures only a slight decrease of the pitch was noted. A ‘pop’ was clearly distinguished in five of nine horses with successful extradural puncture. In four horses a ‘pop’ was not present despite correct extradural needle placement. In three horses with incorrect needle placement a ‘pop’ was present. In the horses with correct needle positioning the median extradural pressure after the puncture was −0.8 kPa (−6 mmHg). Conclusion and clinical relevanceThe acoustic device is useful to assist in the identification of successful or unsuccessful extradural needle placement in the horse.

Measurement of the puncture profile and extradural pressure of cattle during extradural anaesthesia

ObjectiveTo measure the pressure profile during caudal extradural puncture and subsequent extradural anaesthesia in cattle and to investigate the presence of extradural pressure waves. Study designProspective experimental study. AnimalsEleven cattle aged 4.1 ± 2.5 years (range 0.8 to 8.8 years), with a body weight of 613 ± 162 kg (range 302–840 kg). MethodsCaudal extradural puncture was performed. To measure the extradural pressure profile, the needle was connected to an electronic pressure transducer placed at the height of the base of the tail. The pressure profile was recorded for 3 minutes following extradural puncture. Lack of resistance to injection of saline was assessed. One minute and 10 minutes after extradural anaesthesia with procaine extradural pressure was recorded. Correct extradural needle placement was assessed by clinical response. ResultsThree minutes after extradural puncture the median pressure was −16 (range −25 to 25) mmHg. Pressure in the extradural space 1 minute after the lack of resistance, 3 seconds after injection, and 10 minutes after injection was −15 (−24 to 33) mmHg, 8 (−17 to 84) mmHg, and −7 (−25 to 27) mmHg respectively. Pressure waves were visible after puncture, after lack of resistance, 3 seconds and 10 minutes after injection, in 4, 6, 8 and 7 cattle respectively. Pressure after testing lack of resistance, after the injection of local anaesthetic, as well as at the end of the measurement, period was significantly higher than baseline. All cattle showed clinical signs indicative of successful extradural needle placement.Conclusion and clinical relevance Extradural pressure was sub-atmospheric in 82% of the animals. Pressure waves were not consistently present before or after extradural injection, which limits their usefulness to confirm correct extradural needle placement. Extradural pressures increase significantly after injection of local anaesthetic solution. However, the clinical significance of the increase in extradural pressures was not clear.

Invasive arterielle Blutdruckmessung mittels eines aneroiden Systems beim Rind

The aim of this study was to compare the results of invasive arterial blood pressure measurement using an electronic pressure transducer (EPT) or an aneroid pressure system (APS) in cattle. A catheter was placed in the auricular artery of 11 adult cattle and connected to a pressure transducer via pressure line. The aneroid system was connected to the same catheter using a three-way stop-cock in the pressure line. On five occasions three consecutive measurements were performed with the APS. The mean blood pressure values of the EPT were recorded before each individual measurement. Values from each device were compared using Passing and Bablok regression of agreement and a Bland and Altman difference plot. One hundred and forty-seven paired measurements were analysed. The average bias between the two methods (EPT vs. APS) was -1.6 mmHg (95 % confidence interval [CI]: -3.0 to -0.2 mmHg). The coefficient of correlation was 1.0084. The aneroid system showed an almost perfect agreement with the EPT. This study shows that it can be used in a clinical setting as well as under field conditions to measure arterial blood pressure in cattle.

Measurement of impulse from the close-in explosion of doped charges using a pendulum

This paper presents an investigation into the use of a pendulum device for evaluating the energy and hence the impulse transferred to structures from detonating doped and undoped high explosives at ranges of generally less than 0.5 m. For such close-in explosions, evaluating the load delivered by either computer modelling techniques or experiments involving the use of electronic pressure transducers may not be possible. This is because adequate mathematical representation of the events close to a detonating charge may not be available and the expense associated with the use of instrumentation that would be at risk of destruction or at least severe damage could be prohibitive. In the study reported here, a robust pendulum was designed that could be used repeatedly to provide an evaluation of explosive charge output at close range. Once its effectiveness had been demonstrated with standard condensed high explosive charges, it was then used to study the effects of incorporating different materials in the explosive. The purpose of doping the charges in this way was to determine whether the system was capable of discriminating between different charge formulations and, if so, to assess how the additives used for doping affected explosive performance. It was found that doping with fine particles of either barium sulphate or copper oxide increased the amount of energy and impulse delivered to the pendulum from the charge. In contrast, however, doping with dolomite reduced the amount of energy and impulse transferred.

Contemporary Rhinomanometry

By contrast with the smoked drum and other mechanical systems, modern electronic rhinomanometers provide superior sensitivity and frequency response. They enable accurate measurement of nasal airflow resistance to be made and are commercially available. In addition to a rhinomanometer, nasal airflow measurements require a face mask fitted with a flow measuring device (a pneumotach connected to an electronic differential pressure transducer) or, as an alternative to a face mask, a head-out body plethysmograph. Concurrently with nasal respiratory airflow, transnasal pressures between the nostril and pharynx are measured via nasal or oral tubing by a second differential pressure transducer. The transduced electronic analogue signals are digitized, and nasal airflow resistances are computed from the ratio between transnasal pressure and airflow. At a single sitting, a series of measurements with modern rhinomanometry can determine (1) the response to topical decongestant of the mucovascular contribution to nasal airflow resistance at the time of examination and (2) in the decongested nose, the presence, side, site, and severity of structural obstruction. Rhinomanometry is not "medically necessary" in assessment of all cases of nasal obstructive symptoms, but, in many situations, it can provide valuable objective information in compliance with the requirements of evidence-based medicine. This article includes a table listing situations in which rhinomanometry is particularly useful.

Characterization of quartz Bourdon-type high-pressure transducers

The characteristics of commercially available pressure monitors were evaluated. The pressure range of these pressure monitors is up to 100 MPa and the resolution of the transducer is 0.1 kPa. The pressure monitor includes a quartz Bourdon-type high-precision electronic pressure transducer inside the body. The sensing element of the transducer is a precision quartz crystal resonator and the frequency of oscillation varies with pressure-induced stress. In total, six pressure monitors were prepared for this study. During 15 months, the six monitors were calibrated simultaneously using a hydraulic pressure balance 11 times in total. The effects on the readings of the monitors by setting parameters and environmental conditions were evaluated. The important characteristics for the pressure transducer such as the temperature coefficient of the span reading and long-term stability were also evaluated quantitatively. From the evaluation results, the behaviours of the transducers during the period were well characterized. The standard deviation of the relative deviations from the least-squares best-fitting function for each pressure transducer was less than 6 × 10−6 in the pressure range of 30 MPa to 100 MPa and had a maximum of 11 × 10−6 at 10 MPa. In this article, the details of the characterization are described.

Contact stresses in the knee joint in deep flexion

The contact stresses in the knee that arise from activities involving deep flexion have not been given due consideration in view of social and cultural practice amongst many Asians that frequently cause the engagement of these activities. Excessively large stresses (>25 MPa) can cause cartilage damage and may be the precursor to the development of degenerative disease of the joint. In this study, forces in the knee derived from previous studies of human walking and squatting were applied to five cadaver knees that underwent quasi-static mechanical testing. This was conducted using a materials-testing machine and a custom-made apparatus that allowed secure and consistent loading of the knee specimen in flexion beyond 120°. A thin-film electronic pressure transducer was inserted into the cadaver tibiofemoral joint space to measure force and area. Throughout the various positions simulating specific phases of walking, it was found that stresses peaked to 14 MPa (standard deviation was 2.5 MPa). In deep flexion, the peak stresses were significantly larger by over 80%, reaching the damage limits of cartilage. The results from this biomechanical study suggest that the adequacy of articular cartilage to support loads in the knee joint during deep flexion may be questionable.