BACKGOUND: The accuracy of a disposable blood pressure transducer (DBPT) is determined by its physical properties: natural frequency (NF) and damping coefficient (DC). We planned this study to investigate whether the NF and DC of a DBPT are altered by attaching extended catheters and evaluated changes of these physical properties over time. METHODS: Fifteen DBPT sets were connected to a monitor and recorder set. These sets were divided into three groups; five sets had catheters of normal length (Group 1), five sets had 50 cm extended catheters (Group 2), and five sets had 100 cm extended catheters (Group 3). The NF and DC of each system were measured using the fast flush (FF) test. After the DBPT sets were installed, the FF test was performed for each group at five time intervals: 4, 24, 48, 72, and 96 hours. RESULTS: The NF of Groups 2 and 3 decreased and their DC increased compared to those of Group 1. Whereas the NF of Group 3 increased over time, those of Groups 1 and 2 did not. The DC of Groups 2 and 3 decreased over time, but remained unchanged over time for Group 1. When the FF test was done at intervals longer than 24 hours, it was found that the NF, but not the DC, increased for all groups. CONCLUSIONS: Attention should be paid to interpret blood pressure using DBPTs measured by extended catheters and using DBPTs for long periods of time without FFs.
Blood Pressure ; Catheters* ; Transducers ; Transducers, Pressure*

Esophageal retrograde peristalsis is known to be absent normally. This rare finding, if it happens, usually suggests a possibility that proximal ends of the manometric catheter are connected to the pressure transducers in a reverse order. We report a case showing repeated retrograde peristalsis during an esophageal manometric examination due to an inadventently hooked catheter in the esophagus during insertion. We suggest that if a retrograde peristalsis is repeatedly observed during a manometric session, an erroneous recording due to a hooked catheter in the esophageal lumen should be considered as one possibility.
Catheters* ; Esophagus* ; Peristalsis* ; Transducers, Pressure

PURPOSE: To assess the biomechanical effects and effectiveness of an interspinous spinal spacer (ISS) on the intradiscal pressure using in vitro biomechanical tests. MATERIALS AND METHODS: Six calf spine specimens (less than 2 weeks of age, L1-L5) were divided to two groups the intact and the surgery groups (n=3 each). For the surgery group, an ISS made from PMMA (Greek pi=12-mm) were inserted into the space between the spinous processes of L3-L4. The intradiscal pressures at the various regions of the annulus (anterior, posterior, and posterolateral locations) and the nucleus pulposus were measured using the four pressure transducers under pure compression (700 N) and extension loads (700 N+7.5 Nm). RESULTS: An increase in pressure was observed from neutral to extension at the posterior and posterolateral annulus. After inserting the ISS, the changes in pressure at the adjacent disc levels (L2-L3, L4-L5) were negligible regardless of the loading conditions (p>0.05). However, at the implanted level (L3-L4) statistically significant changes in the pressure were found under extension loading at the nucleus pulposus, posterior and posterolateral regions of the annulus with a pressure drop from 1.48 MPa, 1.42 MPa, 1.71 MPa to 1.11 MPa, 0.961 MPa, 1.08 MPa, at the respective locations (p<0.05). The relative percentage decrease were 25%, 31.7%, and 36.8%. CONCLUSION: On the implanted level, these results showed that the insertion of the ISS with PMMA can effectively reduce the intradiscal pressures by at least 25% quite uniformly over the intravertebral disc during extension. More effective reduction was observed at the posterolateral location. The pressure changes at the adjacent levels were negligible in contrast to the abnormal pressure changes that are frequently reported after conventional rigid fusion. This suggests that the likelihood of adjacent level degeneration after surgery can be minimized using the ISS insertion.
Polymethyl Methacrylate ; Spinal Stenosis* ; Spine ; Transducers, Pressure

Alpha-chymotrypsin solutions, 200 unit/ml and 1,000 unit/ml, were injected into the anterior chamber of albino rabbit eyes fonowed by irrigation with normal saline after 3 minutes. Intraocular pressure was recorded by pressure transducer and pressure decay curve analysis was made to calculate the outflow facility according to the method of Eisenlohr and Langham. The follow-up periods were 30 days after the injection of the enzyme solution. By the injection of 0.25 ml of 200 unit/ml solution in 7 eyes, intraocular pressure showed almost no changes throughout the observation period. Outflow facility showed transient decrease during the first 3 to 5 days in some eyes. After the injection of 0.25 ml of 1,000 unit/ml solution in 3 eyes, transient elevation of the intraocular pressure was noted associated with decrease in outflow facility. In one eye, a marked rise in ocular pressure was found All the changes in intraocular pressure and outflow facility returned to the pre-treatment level within 30 days. It was concluded that high concentration of the alpha-chymotrypsin solution injected into the anterior chamber might cause disturbances in trabecular function causing elevation in intraocular pressure.
Anterior Chamber ; Follow-Up Studies ; Intraocular Pressure ; Transducers, Pressure

Gas tamponade is sometimes necessary after vitrectomy. Accurate measurement of intraocular pressure(IOP) in gas-filled eye is important, but is hard to get in operating table, because of lack of a good measuring device. Schiotz tonometry is the only possible method, but it usually gives a lower value than real, because gas-filled eye has a greater compressibility. But if the Schiotz tonometry can give a consistant value in relation to the real value, one can assume a true IOP by simply converting the value, and it will help the vitrectomy surgeon. Vitrectomy with or without lensectomy were done in 7 pigmented rabbits, and fluidair exchange were done at the end of the surgery. Intraocular pressure was monitored by an air infusion system, and true IOP was measured by a transducer from the anterior chamber. Schiotz tonometry was done ar each 5mmHg IOP level, and the values were compared. Schiotz tonometry always gave a lower pressure, and the discrepancy seemed to be greater in aphakic eye, and when the heavier plunger weight were used. Conversion equation was suggested, and their reliability was discussed.
Anterior Chamber ; Intraocular Pressure* ; Manometry ; Operating Tables ; Rabbits ; Transducers ; Vitrectomy*

It has been shown from medical researches that many diseases are major causes of foot morbidity, which are deeply related to the abnormality of the plantar pressure distribution. In this respect, we made a new type of conductive rubber sensor and designed a dynamic contact pressure measuring system of plantar-pressure distribution with 251 testing points successfully. It includes the multipoint conductive rubber sensor, the interface circuit and the computer data collecting and progressing system. The measuring system can give the intuitional and full-scale image results with the full-court, real time testing. Also in this paper are introduced the design of the system, the testing results, and its applications in primary medical studies.
Biomechanical Phenomena ; Equipment Design ; Foot ; anatomy & histology ; physiology ; Humans ; Pressure ; Stress, Mechanical ; Transducers, Pressure ; Walking ; physiology

There are two contradictive opinions of the therapeutic administration of Ginseng in the conditions of cerebrovascular accident and/or hypertensive heart diseases. This experimental study was performed to observe the effects of the Ginseng extract on the blood pressure(BP) and intracranial pressure(ICP) at the same time. Seven mongrel cats were used. ICP was measured with epidural ballon and pressure transducer, and BP with intraarterial catheter via female routs. Both were continuously recorded by polygrapher. 1. In a normal condition, a single intravenous injection of Ginseng 100mg/kg induced immediate reduction of BP for 30~45 second. Intracranial pressure, however, showed delayed elevation for 50~60 second. 2. Even in a condition of increased ICP or induced cardiac hypertension, the results were the same as in above-described normal condition.
Animals ; Blood Pressure* ; Catheters ; Cats* ; Female ; Heart Diseases ; Humans ; Hypertension ; Injections, Intravenous ; Intracranial Pressure* ; Panax* ; Stroke ; Transducers, Pressure

PURPOSE: To evaluate changes in the ciliary sulcus size, anterior chamber depth (ACD) and anterior chamber angle (ACA) during accommodation using an ultrasound biomicroscope (UBM). METHODS: Twenty-seven eyes of 27 healthy subjects were studied. We examined refractive error and intraocular pressure, measured the horizontal distance of the ciliary sulcus, ACD, and ACA at distant fixation and near fixation using a UBM (50 MHz transducer, model P45 UBM plus, Paradigm(R), Kent, U. K.). RESULTS: The subjects included 16 males and 6 females. The mean age of the subjects was 20.5 years (age range, 19-22 years), and mean spherical equivalent was -2.86+/-1.67 diopters. At distant fixation, horizontal ciliary sulcus size was 11.75+/-0.56 mm, ACD was 3.15+/-0.17 mm, and ACA was 38.5+/-4.2 . At near fixation, horizontal ciliary sulcus size was 11.34+/-0.65 mm, ACD was 2.92+/-0.15 mm, and ACA was 44.5+/-5.7 . CONCLUSIONS: During accommodation, horizontal ciliary sulcus size and ACD significantly decreased and ACA increased in the patients.
Anterior Chamber* ; Female ; Humans ; Intraocular Pressure ; Male ; Microscopy, Acoustic* ; Phakic Intraocular Lenses ; Refractive Errors ; Transducers ; Ultrasonography*

BACKGROUND: This study was performed to investigate optimal central venous pressure (CVP) or pulmonary artery occlusion pressure (PAOP) transducer levels in supine and prone positions in pediatric patients. METHODS: Chest tomography images of 213 children aged ≤ 10 years were reviewed. Distances from the back to the uppermost blood level of both atria and their ratios to the largest anteroposterior (AP) diameter of the thorax were calculated for the supine position. For the prone position, same distances and ratios were calculated from the anterior chest. Subgroup analysis was performed to evaluate if there were significant differences in each ratio according to age. RESULTS: In the supine position, the ratio of the uppermost blood level of the right atrium (RA) and left atrium (LA) to the largest AP diameter of the thorax was 80–85% and 60–65%, respectively. The ratio of the most posterior blood level of the RA and LA to largest AP diameter of thorax was 45–50% and 55–60%, respectively, from the anterior chest in the prone position. Subgroup differences in each ratio were within the range of 5%. CONCLUSIONS: In pediatric patients, CVP and PAOP transducers should be differently placed according to supine and prone positions. The influence of age was minimal on the level of each transducer.
Central Venous Pressure* ; Child ; Heart Atria ; Humans ; Prone Position* ; Pulmonary Artery* ; Supine Position ; Thorax ; Transducers*

OBJECTIVES: The sensitivity and accuracy of thermistor airflow signal has been debated. The purposes of this study were to compare apnea-hypopnea index(AHI) detected from a conventional thermistor signal and a nasal pressure transducer of airflow(NPT), to evaluate the value of NPT for the diagnosis of upper airway resistance syndrome (UARS), and to measure airway pressure fluctuations which produced respiratory arousals in UARS by naso-oro-esophageal manometer catheter. The subjects were 30 patients with obstructive sleep apnea syndrome [mild(540), 10), and 6 UARS patients. Airway resistance arousal in this study was defined as arousals which were not associated with apnea or hypopnea of thermistor signal, but showed significant decrease of nasal airflow pressure just before arousal and a prompt recovery of nasal airflow pressure after arousal, The airway pressure fluctuations were measured during 260 airway resistance arousals observed in 10 patients with OSAS, 2 with UARS. RESULTS: Mean AHIs of patients with OSAS were 33.4 by thermistor and 48.4 by NPT. The AHIs of mild, moderate and severe OSAS group were 10.2, 32.1, 65.4 respectively by thermistor and 23.1, 45.9, 76.4 by NPT. The mean AHI of patients with UARS was 3.2 by tehrmistor and 108 by NPT. The mean AHI of patients with nonspecific arousals was 2.7 by thermistor and 4.4 by NPT. The mean airway pressure changes during resiratory arousals of different groups were 8.7 cmH2O in mild OSAS, 11.4 cmH2O in moderate OSAS, 24.7 cmH2O in severs OSAS and 6.6 cmH2O in UARS. CONCLUSION: The nasal pressure transducer of airflow was more sensitive and accurate for assessing respiratory disturbances of patients with OSAS and was extremely helpful for the diagnosis of UARS without esophageal pressure monitoring. From the results, we would like to propose carefully the NPT diagnostic criteria for sleep disordered breathing as follows : NPT-AHI 5-15->UARS, 15-35->mild OSAS, 35-55->moderate OSAS and >55 ->severe OSAS.
Airway Resistance* ; Apnea ; Arousal ; Catheters ; Diagnosis ; Humans ; Sleep Apnea Syndromes ; Sleep Apnea, Obstructive* ; Transducers, Pressure