No evidence of persisting unrepaired nuclear DNA single strand breaks in distinct types of cells in the brain, kidney, and liver of adult mice after continuous eight-week 50 Hz magnetic field exposure with flux density of 0.1 mT or 1.0 mT.

BACKGROUND: It has been hypothesized in the literature that exposure to extremely low frequency electromagnetic fields (50 or 60 Hz) may lead to human health effects such as childhood leukemia or brain tumors. In a previous study investigating multiple types of cells from brain and kidney of the mouse (Acta Neuropathologica 2004; 107: 257-264), we found increased unrepaired nuclear DNA single strand breaks (nDNA SSB) only in epithelial cells of the choroid plexus in the brain using autoradiographic methods after a continuous eight-week 50 Hz magnetic field (MF) exposure of adult mice with flux density of 1.5 mT. METHODS: In the present study we tested the hypothesis that MF exposure with lower flux densities (0.1 mT, i.e., the actual exposure limit for the population in most European countries, and 1.0 mT) shows similar results to those in the previous study. Experiments and data analysis were carried out in a similar way as in our previous study. RESULTS: Continuous eight-week 50 Hz MF exposure with 0.1 mT or 1.0 mT did not result in increased persisting unrepaired nDNA SSB in distinct types of cells in the brain, kidney, and liver of adult mice. MF exposure with 1.0 mT led to reduced unscheduled DNA synthesis (UDS) in epithelial cells in the choroid plexus of the fourth ventricle in the brain (EC-CP) and epithelial cells of the cortical collecting duct in the kidney, as well as to reduced mtDNA synthesis in neurons of the caudate nucleus in the brain and in EC-CP. CONCLUSION: No evidence was found for increased persisting unrepaired nDNA SSB in distinct types of cells in the brain, kidney, and liver of adult mice after continuous eight-week 50 Hz magnetic field exposure with flux density of 0.1 mT or 1.0 mT.

Electromagnetic interference with implantable cardioverter-defibrillators at power frequency: an in vivo study.

BACKGROUND: The number of implantable cardioverter-defibrillators (ICDs) for the prevention of sudden cardiac death is continuing to increase. Given the technological complexity of ICDs, it is of critical importance to identify and control possible harmful electromagnetic interferences between various sources of electromagnetic fields and ICDs in daily life and occupational environments. METHODS AND RESULTS: Interference thresholds of 110 ICD patients (1-, 2-, and 3-chamber ICDs) were evaluated in a specifically developed test site. Patients were exposed to single and combined electric and magnetic 50-Hz fields with strengths of up to 30 kV·m⁻¹ and 2.55 mT. Tests were conducted considering worst-case conditions, including maximum sensitivity of the device or full inspiration. With devices being programmed to nominal sensitivity, ICDs remained unaffected in 91 patients (83%). Five of 110 devices (5%) showed transient loss of accurate right ventricular sensing, whereas 14 of 31 (45%) of the 2- and 3-chamber devices displayed impaired right atrial sensing. No interference was detected in 71 patients (65%) within the tested limits with programming to maximum sensitivity, whereas 20 of 110 subjects (18%) exhibited right ventricular disturbances and 19 of 31 (61%) subjects exhibited right atrial disturbances. CONCLUSIONS: Extremely low-frequency daily-life electromagnetic fields do not disturb sensing capabilities of ICDs. However, strong 50-Hz electromagnetic fields, present in certain occupational environments, may cause inappropriate sensing, potentially leading to false detection of atrial/ventricular arrhythmic events. When the right atrial/right ventricular interferences are compared, the atrial lead is more susceptible to electromagnetic fields. CLINICAL TRIAL REGISTRATION URL: http://clinicaltrials.gov/ct2/show/NCT01626261. Unique identifier: NCT01626261.

Gastroesophageal Reflux and Body Movement in Infants: Investigations with Combined Impedance-pH and Synchronized Video Recording.

The aim of this paper was to investigate the temporal association of gastroesophageal reflux (GER) and body movement in infants. GER were registered by combined impedance-pH, documentation of body movement was done by video. Videorecording time (Vt) was divided into "resting time" and "movement time" and analyzed for occurrence of GER. Association was defined as movement 1 minute before/after the beginning of a GER. Statistical evaluation was by Fisher's exact test. In 15 infants, 341 GER were documented during Vt (86 hours). 336 GER (99%) were associated with movement, only 5 episodes (1%) occured during resting time. Movement was significantly associated with the occurrence of GER (P < .0001). There is a strong temporal association between GER and body movement in infants. However, a clear distinction between cause and effect could not be made with the chosen study design. Combined impedance-pH has proven to be the ideal technique for this approach.

Evaluation of oesophageal mucosa integrity by the intraluminal impedance technique.

BACKGROUND: Oesophageal intraluminal impedance is currently used for assessment of reflux in gastro-oesophageal reflux disease (GORD). Oesophageal mucosa integrity may have a key role in heartburn perception in non-erosive reflux disease (NERD). Severe erosive oesophagitis is associated with low impedance baseline. We hypothesised that impedance baseline measurements could be used to evaluate changes in oesophageal mucosa integrity in man. METHODS: We measured oesophageal impedance baseline before, during and after acid perfusion in rabbits and healthy subjects. Transepithelial resistance (TER) was determined and dilated intercellular spaces (DIS) were assessed in isolated rabbit oesophageal mucosa. Impedance baseline was measured retrospectively at different levels of the oesophagus in impedance-pH recordings from asymptomatic volunteers and patients with GORD. RESULTS: In healthy subjects and rabbits, impedance baseline dropped dramatically during perfusion of control solution (pH 7.2) but after perfusion, impedance recovered. In rabbits, after perfusion with saline pH 1.5 and 1.0 impedance values remained a 39.1 ± 7.0% and 63.9 ± 6.5% (p < 0.05) lower respectively. There was a positive correlation between in vivo basal impedance and in vitro TER values (r = 0.72, p = 0.0021). Tissue showed no erosions but both acidic solutions induced DIS. In healthy subjects, after perfusion with saline pH 2.0 and 1.0 the impedance baseline remained lower a 21.9 ± 6.5% and 52.7 ± 5.0%, (p < 0.0001) respectively. Patients with GORD have a lower impedance baseline than healthy volunteers at the distal oesophagus. CONCLUSIONS: Impedance baseline measurements might be used to evaluate the status of the oesophageal mucosa and to study the role of the impaired mucosal integrity in acid-induced heartburn in healthy volunteers and in patients with GORD.

Millicurrent stimulation of human articular chondrocytes cultivated in a collagen type-I gel and of human osteochondral explants.

BACKGROUND: Here we investigate the effect of millicurrent treatment on human chondrocytes cultivated in a collagen gel matrix and on human osteochondral explants. METHODS: Human chondrocytes from osteoarthritic knee joints were enzymatically released and transferred into a collagen type-I gel. Osteochondral explants and cell-seeded gel samples were cultivated in-vitro for three weeks. Samples of the verum groups were stimulated every two days by millicurrent treatment (3 mA, sinusoidal signal of 312 Hz amplitude modulated by two super-imposed signals of 0.28 Hz), while control samples remained unaffected. After recovery, collagen type-I, type-II, aggrecan, interleukin-1beta, IL-6, TNFalpha and MMP13 were examined by immunohistochemistry and by real time PCR. RESULTS: With regard to the immunostainings 3 D gel samples and osteochondral explants did not show any differences between treatment and control group. The expression of all investigated genes of the 3 D gel samples was elevated following millicurrent treatment. While osteochondral explant gene expression of col-I, col-II and Il-1beta was nearly unaffected, aggrecan gene expression was elevated. Following millicurrent treatment, IL-6, TNFalpha, and MMP13 gene expression decreased. In general, the standard deviations of the gene expression data were high, resulting in rarely significant results. CONCLUSIONS: We conclude that millicurrent stimulation of human osteoarthritic chondrocytes cultivated in a 3 D collagen gel and of osteochondral explants directly influences cell metabolism.

Effects of pulsed and sinusoid electromagnetic fields on human chondrocytes cultivated in a collagen matrix.

Although several effects of electromagnetic fields (EMFs) on articular cartilage have been reported in recent studies, the use of EMFs to treat osteoarthritis remains a matter of debate. In an in vitro study, human chondrocytes harvested from osteoarthritic knee joints were released from their surrounding matrix and transferred in defined concentration into a 3D matrix (type-I collagen gel). The cultivation, performed under standard conditions, lasted up to 14 days. During this time, treatment groups were continuously exposed to either sinusoid or pulsed electromagnetic fields (PEMFs). The PEMFs revealed the following characteristics: maximum magnetic flux density of 2 mT, frequency of the bursts of 16.7 Hz with each burst consisting of 20 pulses. Similarly, the sinusoid EMFs also induced a maximum flux density of 2 mT with a frequency of 50 Hz. Control groups consisting of equal number of samples were not exposed to EMF. Immunohistological examinations of formalin-fixed, paraffin-embedded samples revealed positive staining for type-II collagen and proteoglycans in the immediate pericellular region with no differences between the two different treatment groups and the control groups. With increasing cultivation time, both type-II collagen and aggrecan gene expression declined, but no significant differences in gene expression were found between the treatment and control groups. In conclusion, using our in vitro setting, we were unable to detect any effects of pulsed and sinusoidal magnetic fields on human adult osteoarthritic chondrocytes.

Demodulation in tissue, the relevant parameters and the implications for limiting exposure.

In the biomedical literature there are a number of reports that speculate about possible effects in the body due to the demodulation of electromagnetic fields. However, only few interactions in amplitude-modulated or even pulse-modulated electromagnetic waves are fundamentally plausible and have been demonstrated to occur in humans. The following observations fall into this specific category: thermal effects of amplitude- or pulse-modulated microwaves; demodulation of amplitude- or pulse-modulated electromagnetic waves in cell membranes; and demodulation of amplitude- or pulse-modulated electromagnetic fields in the electronics of implants such as cardiac pacemakers or cardioverter defibrillators. The possible consequences of these effects for the organism, their probability of occurrence in everyday life field conditions, and, consequently, the implications for limiting exposure are very different. Microwave hearing is a harmless effect which is perceived by humans only in strong fields with high peak power densities of more than 100 mW cm(-2). In normal residential or occupational environments the peak power density of even the strongest microwave sources is only around 1 mW cm(-2). Demodulation of pulse-modulated electromagnetic fields in the cell membranes decreases the stimulation threshold of nerves and muscles and can introduce numerous adverse effects ranging from perception of pain to dangerous cardiac fibrillations. The stimulation and demodulation effects are restricted to carrier frequencies up to several MHz. In experiments with 900 and 1,800 MHz packets with lengths of up to 100 ms and applied powers of up to 100 W, neither a direct stimulation of superficial nerves and muscles nor the conditioning of an electrical current stimulus could be confirmed. Pulse-modulated electromagnetic waves are demodulated in the electronic circuits of implants and can inhibit cardiac pacemakers and introduce cardiac arrest in this way. The highest sensitivity results from repetition rates of pulses below 100 Hz. The preceding two implications should be considered in the elaboration of new general guidelines limiting the exposure for healthy as well as for sick persons in the future.

Short-term elevation of intracranial pressure does neither influence duodenal motility nor frequency of bolus transport events: a porcine model.

BACKGROUND: Patients with traumatic brain injuries and raised intracranial pressure (ICP) display biphasic response with faster gastric emptying during the early stage followed by a prolonged gastric transit time later. While duodenal contractile activity plays a pivotal role in transpyloric transit we investigated the effects of raised intracranial pressure on duodenal motility during the early phase. In order to exclude significant deterioration of mucosal blood supply which might also influence duodenal motility, luminal microdialysis was used in conjunction. METHODS: During general anaesthesia, 11 pigs (32-37 kg, German Landrace) were instrumented with both a luminal catheter for impedancometry and a luminal catheter for microdialysis into the proximal duodenum. Additionally, a catheter was inserted into the left ventricle to increase the intracranial pressure from baseline up to 50 mmHg in steps of 10 mmHg each hour by injection of artificial cerebrospinal fluid. At the same time, duodenal motility was recorded continuously. Duodenal luminal lactate, pyruvate, and glucose concentrations were measured during physiological state and during elevated intracranial pressure of 10, 20, 30, 40, and 50 mmHg in six pigs. Five pigs served as controls. RESULTS: Although there was a trend towards shortened migrating motor cycle (MMC) length in pigs with raised ICP, the interdigestive phase I-III and the MMC cycle length were comparable in the groups. Spontaneous MMC cycles were not disrupted during intracranial hypertension. The mean concentration of lactate and glucose was comparable in the groups, while the concentration of pyruvate was partially higher in the study group than in the controls (p < 0.05). This was associated with a decrease in lactate to pyruvate ratio (p < 0.05). CONCLUSION: The present study suggests that a stepwise and hourly increase of the intracranial pressure of up to 50 mmHg, does not influence duodenal motility activity in a significant manner. A considerable deterioration of the duodenal mucosal blood flow was excluded by determining the lactate to pyruvate ratio.

Gastric fullness, physical activity, and proximal extent of gastroesophageal reflux.

OBJECTIVES: Proximal extent of gastroesophageal reflux (PER) is relevant for symptoms in GERD patients. It has been suggested that PER is determined by the volume of the refluxate that, in turn, might depend on the degree of gastric fullness. Abdominal straining, during ambulation, increases the likelihood of gastroesophageal reflux. We assessed the influence of gastric fullness and ambulation on proximal extent of reflux. METHODS: PER was assessed in 37 patients with GERD undergoing ambulatory pH impedance monitoring. In 14 controls and 19 GERD patients, esophageal pH impedance and gastric emptying were also studied simultaneously in stationary conditions. We compared PER during fasting, early postprandial (before half emptying), and late postprandial periods in ambulatory and stationary conditions. RESULTS: More reflux episodes reached the proximal esophagus in the postprandial period compared to fasting (60%+/-4 vs 29%+/-3, p<0.05). In stationary conditions, early postprandial reflux reached higher proximal extent than late postprandial reflux (15+/-3% vs 8+/-4%, p<0.05). The proportion of reflux events reaching the proximal esophagus was significantly higher in ambulatory than in stationary conditions (29+/-5% vs 15+/-3%, p<0.05). CONCLUSION: Compared to fasting, reflux episodes occurring after the meals are more likely to reach higher proximal extent, particularly so during the early postprandial period. The highest proportion of postprandial proximal reflux occurred in ambulatory condition. These findings suggest that reducing meal volumes and early postprandial physical activity might contribute to decrease proximal extent of reflux and postprandial GERD symptoms.

Characteristics of oesophageal bolus transport in patients with mild oesophagitis.

OBJECTIVE: Patients with gastroesophageal reflux disease (GORD) frequently have oesophageal motility disturbance. However, detailed data about bolus transport characteristics in these patients are still lacking. In the present study the new technology of concurrent impedance manometry was applied for characterization of oesophageal motor function in patients with mild GORD. METHODS: Oesophageal motility testing was performed in 25 patients with mild GORD (group 1) as compared to 25 healthy subjects (group 2) employing the technique of concurrent impedancometry and manometry. Oesophageal motility as well as patterns and parameters of bolus transport after the swallowing of saline or yogurt were analysed. RESULTS: According to manometry the velocity of the contraction wave was similar in both groups. Mid-distal contraction amplitude in group 1 was still in the normal range but significantly lower than in group 2 (57.4+/-4.5 mmHg vs 91.4+/-7.5 mmHg for saline, and 47+/-4.1 vs 80.7+/-9.4 mmHg for yogurt). According to impedance measurements, bolus transport was significantly slower (3.6+/-0.1 vs 4.0+/-0.1 cm/s for saline and 3.0+/-0.1 vs 3.2+/-0.1 cm/s for yogurt), and post-deglutitive impedance was significantly lower in group 1: 2110 omega+/-116 omega versus 2542 omega+/-152 omega (P<0.01) with saline and 1862 omega+/-108 omega versus 2348 omega+/-148 omega with yogurt (P<0.01). GORD patients showed several pathological bolus transport patterns, which were not observed in healthy subjects. Gastroesophageal liquid reflux was observed between the swallows. CONCLUSIONS: In patients with mild GORD concurrent impedancometry and manometry is sufficiently sensitive for the detection of minor oesophageal dysmotility. Several pathological features have been characterized including delayed bolus transport, impaired propulsive volume clearance, pathological transport patterns and pathological reflux patterns.

Influence of low frequency electric fields on anti- and pro-coagulability of the vascular endothelium: new insights into high-voltage electrical injury.

After high-voltage electric injury, patients often show tissue necrosis and thrombosis of blood vessels even remote from entry and exit site of electrical current. In this study, plasma levels of TAT, F(1+2), PAI-1, and t-PA were determined in vivo in three patients with high-voltage injury for 96 hours after trauma. In order to analyse a possible effect on haemostasis related to endothelial cell damage, protein S, TF, ET-1, PGI(2), NO, t-PA, and PAI-1 were determined for 72 hours in vitro in cell culture supernatant of HUVECs that had been exposed to 1, 10, 30, and 50 electric field periods of 50 Hz with field strength of 60 V/cm and duration of 20 ms. Furthermore, expression of thrombomodulin was immunohistochemically analysed. Clotting activation could be observed in our patients by increased levels of F(1+2) and TAT between 12 and 72 hours after injury, whereas fibrinolysis was disturbed due to high PAI-1. One patient presented thrombosis of vessels by day 3. In vitro, PAI-1 increased significantly (p<0.05) in medium of cells with an application of 30 and 50 periods between 2 and 48 hours. Between 4 and 72 hours, the concentration of t-PA was significantly lower (p<0.05) in the medium of HUVECs exposed to 10, 30, and 50 periods, whereas there was a significant increase (p<0.05) in the concentration of TF in the cell groups with an application of 30 and 50 periods. 24, 48, and 72 hours after injury, there was just weak or no staining for thrombomodulin in HUVECs with an application of 30 and 50 periods. The disturbed balance between clotting system and fibrinolysis seen in vitro after electric injury might explain the clinical observation of a progressive thrombosis of blood vessels after electric injury leading to tissue loss.

Inter- and intraobserver agreement for gastroesophageal reflux detection in infants using multiple intraluminal impedance.

The multiple intraluminal impedance (MII) technique is a new method that allows pH-independent gastroesophageal reflux detection via changes in impedance caused by a liquid bolus inside the esophagus. We wanted to know whether this technique yields objective and reproducible results. Twenty 3- to 6-hour recordings of MII from 19 preterm infants (median gestational age at birth 30 weeks, range 24-34 weeks; age at study 26 days, range 13-93 days) were divided into 23-second segments and analyzed for reflux episodes by three investigators; one investigator analyzed the data set twice. Observer agreement was assessed using kappa statistics. Each investigator analyzed 16,627 23-second segments, with a median of 854 (range 486-979) segments per recording. Median kappa values for the 20 recordings were 0.79, 0.83, and 0.83 for the three pairs of investigators and 0.84 for the repeated scoring procedure. MII recordings could be analyzed with a high level of inter- and intraobserver agreement.

Impedance characteristics of normal oesophageal motor function.

OBJECTIVE: To obtain detailed data about the correlation between oesophageal peristalsis and bolus transport for clinical oesophageal motility testing. METHODS: Oesophageal motility testing was performed in 25 healthy subjects by using the newly developed technique of concurrent impedancometry and manometry. Parameters of oesophageal motility and bolus transport as well as the correlation between transit and motility were analysed after swallowing saline or yogurt. RESULTS: Detailed data about bolus transport and oesophageal motility could be obtained during a single investigation step. Air was observed in front of the bolus in 76% of the swallows. Resting baseline impedance was significantly higher in the oesophagus than in the stomach (2832+/-118 Omega vs 688+/-119 Omega). The deglutitive impedance gradient was 222+/-26 Omega for saline and 482+/-38 Omega for yogurt. Bolus propagation velocity and bolus transit time as impedance parameters of bolus transport discriminated fluid from semisolid bolus (4.0+/-0.1 cm/s vs 3.2+/-0.1 cm/s and 9.9+/-0.2 s vs 11.5+/-0.2 s, for saline vs yogurt), while contraction wave amplitude as a manometry parameter of oesophageal motor function did not (91.4+/-7.5 mmHg vs 80.7+/-9.4 mmHg, for saline vs yogurt). There was a poor correlation between bolus propagation velocity and contraction wave amplitude. CONCLUSIONS: Impedance parameters of normal oesophageal motor function have been characterized. Impedancometry and manometry provide different but complementary data about oesophageal motor function. Concurrent impedancometry and manometry allows detailed monitoring of oesophageal motility and bolus transit, which may open new perspectives for comprehensive oesophageal motility testing.

Effects of thickened feeding on gastroesophageal reflux in infants: a placebo-controlled crossover study using intraluminal impedance.

OBJECTIVE: Thickening of formula feedings is part of the therapeutic approach for gastroesophageal reflux (GER) in infants. However, its mechanism of action, especially regarding the occurrence of nonacid (pH >4) GER, has not yet been clearly described. The aim of this randomized, placebo-controlled crossover study was to examine the influence of formula thickened with carob (St. John's bread) bean gum on acid and nonacid GER. METHODS: Infants with recurrent regurgitation and without other symptoms were fed alternately (A-B-A-B-A-B) with thickened (A) and nonthickened (B) but otherwise identical formula. Documentation of GER episodes during the study was performed by simultaneous intraesophageal impedance measurement (intraluminal electrical impedance; IMP) and pH monitoring. The IMP technique is able to detect bolus movements inside a luminal organ. The use of multiple measuring segments on a single catheter allowed the analysis of direction, height, and duration of the bolus transport. Continuous videorecording and visual surveillance of regurgitation frequency and amount resulted in a severity score. RESULTS: Fourteen infants (42 +/- 32 days old) were examined during 6 feeding intervals each for a total measuring time of 342 hours. A total of 1183 GER episodes and 83 episodes of regurgitation were registered. Regurgitation frequency (15 vs 68 episodes) and amount (severity score 0.6 vs 1.8) were significantly lower after feedings with thickened formula. The difference regarding the occurrence of GER documented by IMP was also pronounced (536 vs 647 episodes). Although not statistically significant, maximal height reached by the refluxate in the esophagus was decreased after thickened feedings. Mean GER duration and the frequency of acid (pH <4) GER were not altered. CONCLUSIONS: Thickened feeding has a significant effect on the reduction of regurgitation frequency and amount in otherwise healthy infants. This effect is caused by a reduction in the number of nonacid (pH >4) GER episodes, but also because of a decrease of mean reflux height reached in the esophagus. However, the occurrence of acid GER is not reduced. The combination of IMP and pH monitoring allows the complete registration and description of these GER episodes. Thickening of formula feedings with carob bean gum is an efficient therapy for uncomplicated GER in infants.

Detection of small bolus volumes using multiple intraluminal impedance in preterm infants.

BACKGROUND: Multiple intraluminal impedance (MII) is a new technique that allows detection of reflux and swallows via changes in impedance caused by a liquid bolus inside the esophagus. The method is independent of pH. The authors studied the ability of this technique to detect the small bolus volumes potentially occurring in young infants. METHODS: Ten preterm infants (median gestational age at birth, 33 weeks; range, 25-36 weeks; age at study, 9 days; range, 2-39 days) underwent 10 instillations each of 0.1 mL to 0.5 mL saline while MII was recorded via a 2.4-mm nasogastric catheter. MII signals were analyzed for swallows, defined as a decrease in impedance starting within 1 minute. From the liquid instillation in the most proximal channel and extending downward, impedance changes during these induced swallows were compared with those occurring during spontaneous swallows. RESULTS: All 100 liquid instillations resulted in a typical impedance pattern, occurring after a median interval of 4.4 seconds (range, 1.8-8.9 seconds). The decrease in impedance was more pronounced than after spontaneous swallows (30% vs. 24%, P < 0.03) and extended downward more rapidly (12.3 cm/s vs. 5.8 cm/s, P < 0.01). CONCLUSION: Bolus transport of small liquid volumes can be detected via MII.

Influence of nasogastric tubes on gastroesophageal reflux in preterm infants: a multiple intraluminal impedance study.

To investigate whether a nasogastric tube predisposes to gastroesophageal reflux, 16 preterm infants underwent 48-hour recordings of multiple intraluminal impedance with the catheter tip in the lower esophagus or stomach for 24 hours each. There were 72 (range, 40-145) reflux episodes with the esophageal placement and 122 (range, 60-147) during the gastric position (P <.01).

Esophageal pH monitoring and impedance measurement: a comparison of two diagnostic tests for gastroesophageal reflux.

BACKGROUND: pH monitoring is the standard diagnostic tool for gastroesophageal reflux in infants. However, this method does not document the reflux of all kinds of fluid from the stomach into the esophagus, but only documents acid material. The parameters that define reflux episodes by pH monitoring have been derived empirically from observations of many infants considered healthy and ill. Acid reflux is a continuum, some reflux is normal and doubt exists as to how much reflux is abnormal. In this study, one of the standardized protocols for analyzing pH recordings was evaluated and compared with simultaneously obtained intraesophageal impedance measurement (IMP), a pH-independent method of detecting bolus movement within the esophagus. METHODS: The esophagi of 50 infants with reflux symptoms were measured, using both standard pH probe and multiple-site impedance measurement. A standard protocol for analyzing esophageal pH records was used. The sampling rate for pH values was 15/min. Acid reflux was defined as pH less than 4.0 (threshold pH) for at least 15 seconds (minimal duration) with at least 30 seconds (latency time) between separate episodes. The software used could adjust independently or in combinations the sampling rate and these reflux criteria. Thereby it was determined whether changes in the criteria for acid reflux improved the sensitivity and predictive value of pH monitoring when compared with reflux episodes defined by IMP. RESULTS: During 318 hours of recording in 50 infants, 1,887 episodes of reflux occurred according to IMP. Only 282 (14.9%) of the IMP-determined episodes were acid reflux episodes. No alkaline reflux episodes occurred. Among the 270 pH probe-determined episodes using the standard criteria of acid reflux, only 153 (sensitivity, 54.3%; positive predictive value, 56.7%) were accompanied by unmistakable retrograde bolus movement using IMP measurements. Retrograde bolus movement did not accompany the other 117 episodes. Using a sampling rate of 15/min, a pH threshold of 4.0, a minimal duration of reflux episodes of 8 seconds, and a latency time of 60 seconds, the positive predictive value of pH probe results increased to 60.7%. Variations in the sampling rate or criteria for defining acid reflux did not significantly improve the accuracy of the pH probe results versus IMP-defined episodes. CONCLUSIONS: Most reflux episodes that occur in infants are undetectable by standard pH probe monitoring. pH monitoring does not detect all reflux in the esophagus but is useful for detecting acidity in the esophagus and determining the duration of its presence. Combining pH monitoring with impedance measurement is a valuable diagnostic tool for gastroesophageal reflux in infants.

Mechanically induced electrical potentials of articular cartilage.

While there is increasing evidence that chondrocytes are affected by mechanically induced stimuli, endogenous force-related electrical potentials within articular cartilage have been so far observed only in-vitro. Using a porcine ex-vivo model (German Land Race), 8 knee joints were explanted and exposed to mechanical force (up to 800 N) using a special device. Electrodes were inserted into the cartilage matrix. With an amplifier and an A/D transducer the changes of electrical voltage between the electrodes as well as those of the force were recorded online and simultaneously on a computer. Additionally, we located one pair of electrodes on the surface of the cartilage tissue to detect electrical fields outside the cartilage tissue. In relation to the applied force we observed that electrical potentials derived from inside and outside the articular cartilage showed a correspondence. When an alternating force with an amplitude of 360 N and a frequency of about 0.2 Hz was periodically applied, we measured peak amplitudes ranging from 2.1 to 5.5 mV within the cartilage tissue with electrical negativity within the weight bearing area of the cartilage tissue. The measured voltages depended on the applied force, the location of the electrodes, and on anatomical variations. We found an almost linear relation between the magnitude of the applied force and the recorded voltage. With the help of the electrodes located outside and within the cartilage tissue, we were able to show that force dependent fields are generated inside the cartilage. There are several theories explaining the origin of these electrical phenomena, many of them focusing on the negative charges of the proteoglycans in relation to the flow of interstitial fluid and ions under compression. However, the consequences of these phenomena are yet not clear.