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Biomedical subjects

R H Sandler

Publications and source records attributed to R H Sandler.

At least 19 recordsLinked to original sources
PubMed2005

Computerised analysis of auscultatory sounds associated with vascular patency of haemodialysis access.

Vascular access for renal dialysis is a lifeline for about 120 000 individuals in the United States. Stethoscope auscultation of vascular sounds has some utility in the assessment of access patency, yet can be highly skill-dependent. The objective of the study was to identify acoustic parameters that are related to changes in vascular access patency. The underlying hypothesis is that stenoses of haemodialysis access vessels or grafts cause vascular sound changes that are detectable using computerised data acquisition and analysis. Eleven patients participated in the study. Their vascular sounds were recorded before and after angiography, which was accompanied by angioplasty in most patients. The sounds were acquired using two electronic stethoscopes and then digitised and analysed on a personal computer. Vessel stenosis changes were found to be associated with changes in acoustic amplitude and/or spectral energy distribution. Certain acoustic parameters correlated well (correlation coefficient = 0.98, p < 0.0001) with the change in the degree of stenosis, suggesting that stenosis severity may be predictable from these parameters. Parameters also appeared to be sensitive to modest diameter changes (> 20%), (p < 0.005, Wilcoxon rank sum test). These results suggest that computerised analysis of vascular sounds may be useful in vessel patency surveillance. Further testing using longitudinal studies may be warranted.

Arteriovenous Shunt, Surgical↗
PubMed2005

Breath sound changes associated with malpositioned endotracheal tubes.

Endotracheal tubes (ETTs) are used to establish airway access in patients with ventilatory failure and during general anaesthesia. Tube malpositioning can compromise respiratory function and can be associated with increased morbidity and mortality. Clinical assessment of ETT position normally involves chest auscultation, which is highly skill-dependent and can be misleading. The objective of this pilot study was to investigate breath sound changes associated with ETT malpositioning. Breath sounds were acquired in six human subjects over each hemithorax and over the epigastrium for tracheal, bronchial and oesophageal intubations. When the ETT was in the oesophagus, the acoustic energy ratio between epigastrium and chest surface increased in all subjects (p < 0.04). In addition, ETT placement in the right mainstem bronchus decreased the acoustic energy ratio between the left and right hemithoraxes in all subjects (p < 0.04). A baseline measurement of this energy ratio was needed for bronchial intubation identification. However, using this ratio after bandpass filtering (200-500 Hz) did not require a baseline value, which would increase the utility of this method for initial ETT placement. These results suggest that computerised analysis of breath sounds may be useful for assessment of ETT positioning. More studies are needed to test the feasibility of this approach further.

Acoustics↗
PubMed2002

Use of abdominal percussion for pneumoperitoneum detection.

Pneumoperitoneum refers to free air within the abdominal cavity that typically signifies serious abdominal pathology such as a perforated gut. The principal hypothesis of the study was that abdominal structure alterations due to pneumoperitoneum cause diagnostic changes in the sounds induced by abdominal percussion. The current pilot study investigated these changes in a mongrel dog model. Abdominal percussion was performed at baseline and after creation of pneumoperitoneum states. The resulting acoustic events were acquired, digitised and analysed. The event attack and decay rates and dominant frequencies during decay decreased with pneumoperitoneum (p = 0.084, 0.014 and 0.004, respectively; Wilcoxon signed-rank test). Simple theoretical models were constructed and predicted the observed decrease in resonant frequencies with increasing air pocket size. The results suggested that the normal and the 1,000 ml pneumoperitoneum states can be separated using thresholds of the attack and decay rates and resonant frequency (specificity = 80%, 100% and 100%, and sensitivity = 100%, 100% and 100%, respectively). Separating the control and the 500 ml pneumoperitoneum cases may be also possible (specificity = 80%, 100%, 100% and sensitivity = 50%, 70% and 90%, respectively), but separating the two levels of pneumoperitoneum was not feasible using the current approach. Therefore analysis of abdominal percussion sounds may prove useful for pneumoperitoneum detection, but not for distinguishing different levels of that condition.

Abdomen↗
PubMed2002

Pneumothorax detection using pulmonary acoustic transmission measurements.

Pneumothorax is a common clinical condition that can be life threatening. The current standard of diagnosis includes radiographic procedures that can be costly and may not always be readily available or reliable. The objective of this study was to investigate the hypothesis that pneumothorax causes detectable pathognomonic changes in pulmonary acoustic transmission. An animal model was developed whereby 15 mongrel dogs were anaesthetised, intubated and mechanically ventilated. A thoracoscopic trocar was placed into the pleural space for the introduction of air and confirmation of a approximately 30% pneumothorax by direct visualisation. Broadband acoustic signals were introduced into the endotracheal tube, while transmitted waves were measured at the chest surface. Pneumothorax was found consistently to lower the pulmonary acoustic transmission in the 200-1200 Hz frequency band, whereas smaller transmission changes occurred at lower frequencies (p< 0.0001, sign test). The ratio of acoustic energy between low-(< 220 Hz) and high-(550-770 Hz) frequency bands was significantly different in the control and pneumothorax states (p < 0.0001, sign test). This implies that pneumothoraces can be reliably detected using pulmonary acoustic transmission measurements in the current animal model. Further studies are needed to investigate the feasibility of using this technique in humans.

Acoustics↗
PubMed2002

Pneumothorax detection using computerised analysis of breath sounds.

The primary objective of the study was to investigate the effects of pneumothorax (PTX) on breath sounds and to evaluate their use for PTX diagnosis. The underlying hypothesis is that there are diagnostic breath sound changes with PTX. An animal model was created in which breath sounds of eight mongrel dogs were acquired and analysed for both normal and PTX states. The results suggested that pneumothorax was associated with a reduction in sound amplitude, a preferential decrease in high-frequency acoustic components and a reduction in sound amplitude variation during the respiration cycle (p<0.01 for each, using the Wilcoxson signed-rank test). Although the use of diminished sound amplitude for PTX diagnosis assumes availability of baseline measurements, this appears unnecessary for high-frequency reduction or sound amplitude changes over the respiratory cycle. Further studies are warranted to test the clinical feasibility of the method in humans.

Animals↗
PubMed2002

Modeling sound transmission through the pulmonary system and chest with application to diagnosis of a collapsed lung.

A theoretical and experimental study was undertaken to examine the feasibility of using audible-frequency vibro-acoustic waves for diagnosis of pneumothorax, a collapsed lung. The hypothesis was that the acoustic response of the chest to external excitation would change with this condition. In experimental canine studies, external acoustic energy was introduced into the trachea via an endotracheal tube. For the control (nonpneumothorax) state, it is hypothesized that sound waves primarily travel through the airways, couple to the lung parenchyma, and then are transmitted directly to the chest wall. In contradistinction, when a pneumothorax is present the intervening air presents an added barrier to efficient acoustic energy transfer. Theoretical models of sound transmission through the pulmonary system and chest region to the chest wall surface are developed to more clearly understand the mechanisms of intensity loss when a pneumothorax is present, relative to a baseline case. These models predict significant decreases in acoustic transmission strength when a pneumothorax is present, in qualitative agreement with experimental measurements. Development of the models, their extension via finite element analysis, and comparisons with experimental canine studies are reviewed.

Acoustic Stimulation↗
PubMed2001

Acoustic characteristics of air cavities at low audible frequencies with application to pneumoperitoneum detection.

Air accumulations within living organisms are sometimes pathologic. An example is free air within the abdomen from perforation of the intestines (a condition called pneumoperitoneum). The objectives of the described research were to define the acoustic signatures of abdominal air cavities at low frequencies and to investigate the feasibility of using these signatures for pneumoperitoneum diagnosis. The central hypothesis was that low-frequency vibro-acoustic property changes are detectable using broad-band acoustic excitation applied at the abdominal surface. Band-limited white noise (0-3200 Hz) was introduced at the abdominal surface of sedated dogs and response was measured by a surface vibro-acoustic sensor. The transfer function and coherence were estimated from these measurements. The presence of pneumoperitoneum caused increased resonances and anti-resonances (p < 0.01). Measures of the latter parameters were proposed and evaluated to quantitatively measure their magnitude. Resonant spectral peaks of more than 3 dB were consistent with pneumoperitoneum (p < 0.01), and both resonance and anti-resonance increased with condition severity (p < 0.03). The data also suggest a possible reduction in the resonant and anti-resonant frequencies with decreasing air cavity volumes (p = 0.14) as supported by theoretical predictions. Finally, anti-resonance was also found to be associated with a drop in coherence. These findings suggest that the proposed technique may be useful in the diagnosis of pneumoperitoneum.

Acoustics↗
PubMed2001

Radiation impedance of a finite circular piston on a viscoelastic half-space with application to medical diagnosis.

In a recent study a new analytical solution was developed and validated experimentally for the problem of surface wave generation on a linear viscoelastic half-space by a rigid circular disk located on the surface and oscillating normal to it. The results of that study suggested that, for the low audible frequency range, some previously reported values of shear viscosity for soft biological tissues may be inaccurate. Those values were determined by matching radiation impedance measurements with theoretical calculations reported previously. In the current study, the sensitivity to shear viscoelastic material constants of theoretical solutions for radiation impedance and surface wave motion are compared. Theoretical solutions are also compared to experimental measurements and numerical results from finite-element analysis. It is found that, while prior theoretical solutions for radiation impedance are accurate, use of such measurements to estimate shear viscoelastic constants is not as precise as the use of surface wave measurements.

Elasticity↗
PubMed2000

Detection and analysis of gastrointestinal sounds in normal and small bowel obstructed rats.

This study is aimed at detecting gastrointestinal sounds (GIS) and correlating their characteristics with gastrointestinal (GI) conditions. The central hypotheses are that GIS generation depends on the motility patterns and the mechanical properties of the gut, and that changes in those result in measurable differences in GIS. An animal model which included both healthy rats and those with small bowel obstruction (SBO) was developed. The acoustic bursts of GIS were detected by amplitude thresholding the signal envelope. Three methods of envelope estimation were proposed and evaluated. Envelope estimation using a Hilbert transform was found to produce the best results in the current application. The duration and dominant frequency of each detected GIS event was estimated and clear differences between healthy and diseased rats were discovered. In the control state, GIS events were found to consistently be of relatively short duration (3-65 ms). Although the majority of events in the SBO state had similar short duration, infrequent longer events were also detected and appeared to be pathognomonic. Long duration events (> 100 ms) occurred in each of seven obstructed, but in none of 14 non-obstructed, cases (p < 0.001). It is concluded that GIS analysis may prove useful in the non-invasive, rapid, and accurate diagnosis of SBO.

Animals↗
PubMed2000

Short-term benefit from oral vancomycin treatment of regressive-onset autism.

In most cases symptoms of autism begin in early infancy. However, a subset of children appears to develop normally until a clear deterioration is observed. Many parents of children with "regressive"-onset autism have noted antecedent antibiotic exposure followed by chronic diarrhea. We speculated that, in a subgroup of children, disruption of indigenous gut flora might promote colonization by one or more neurotoxin-producing bacteria, contributing, at least in part, to their autistic symptomatology. To help test this hypothesis, 11 children with regressive-onset autism were recruited for an intervention trial using a minimally absorbed oral antibiotic. Entry criteria included antecedent broad-spectrum antimicrobial exposure followed by chronic persistent diarrhea, deterioration of previously acquired skills, and then autistic features. Short-term improvement was noted using multiple pre- and post-therapy evaluations. These included coded, paired videotapes scored by a clinical psychologist blinded to treatment status; these noted improvement in 8 of 10 children studied. Unfortunately, these gains had largely waned at follow-up. Although the protocol used is not suggested as useful therapy, these results indicate that a possible gut flora-brain connection warrants further investigation, as it might lead to greater pathophysiologic insight and meaningful prevention or treatment in a subset of children with autism.

Administration, Oral↗
PubMed1999

Gastrointestinal sounds and migrating motor complex in fasted humans.

OBJECTIVE: We investigated the relationships among gastrointestinal sounds, gastrointestinal manometric findings, and small intestinal transit time in healthy fasted humans. METHODS: Gastrointestinal sounds acquired with two microphones attached to the upper and lower abdominal walls of healthy subjects were quantified with a computer-aided sound analysis program. Antroduodenal contractions were recorded by manometry. Small intestinal transit time was measured by breath hydrogen testing after intraduodenal administration of lactulose. RESULTS: The sum of the gastrointestinal sound amplitudes (sound index) in both the upper and lower abdomen changed with time, coinciding with the gastric phases of the migrating motor complex. The sound indices in the upper and lower abdomen were 59.0+/-24.8 and 98.1+/-21.6 mV/min in phase 1, 95.5+/-27.9 and 127.4+/-34.9 mV/min in phase 2, and 132.8+/-12.4 and 188.5+/-73.4 mV/min in phase 3, respectively. There were no significant differences among motility phases in terms of the mean duration or frequency of each sound event. Intravenous erythromycin induced phase 3 in the stomach and doubled the sound index. Somatostatin analogue induced phase-3-like clustered contractions in the duodenum, but inhibited antral contractions and decreased the sound index. The small intestinal transit time was shorter and the sound index increased after intravenous metoclopramide, compared with controls. Scopolamine delayed small intestinal transit time and decreased the sound index. CONCLUSIONS: This study is the first to document the relationships between gastrointestinal sounds and the migrating motor complex. The chronological relation between antral motility and gastrointestinal sounds, and the dissimilar effects of erythromycin and somatostatin, suggest that antral contractions increase gastrointestinal sounds, perhaps by supplying gas into the intestine.

Adult↗
PubMed1999

Excitation and propagation of surface waves on a viscoelastic half-space with application to medical diagnosis.

An analytical solution is developed for the problem of surface wave generation on a linear viscoelastic half-space by a finite rigid circular disk located on the surface and oscillating normal to it. The solution is an incremental advancement of theoretical work reported in articles focused on seismology. Since the application of interest here is medical diagnostics, the solution is verified experimentally using a viscoelastic phantom with material properties comparable to biological soft tissue. Findings suggest that prior estimates in the literature of the shear viscosity in human soft tissue may not be accurate in the low audible frequency range. Measurement of wave motion on the skin surface caused by internal biological functions or external stimuli has been studied by a few researchers for rapid, nonintrusive diagnosis of a variety of specific medical ailments. It is hoped that the developments reported here will advance these techniques and also provide insight into related diagnostic methods, such as sonoelastic imaging and other methodologies that utilize disease-related variations in tissue shear elasticity or variations in density due to gaseous inclusions.

Diagnosis↗
PubMed1995

Development of pediatric and neonatal parenteral nutrition order forms.

The diversity of nutritional needs within the pediatric population makes ordering parenteral nutrition (PN) for infants and children a difficult task for inexperienced clinicians. A well designed PN order form can simplify this task. Standard PN solutions, tables with age-specific nutrient requirements, and guidelines for advancing substrate may improve PN prescriptions and serve as an educational tool. The development of an optimal PN order form for an institution requires consideration of many factors, including the patient population, requirements of the institution, and the needs of the staff and students. One nutrition support team's experience in developing pediatric PN order forms is described.

Age Factors↗
PubMed1992

Fluoroscopic placement of jejunal feeding tubes.

Over a two-and-one-half year period, 50 children underwent placements of jejunal tubes through a nasal route (NJ, n = 47) or through an existing gastrostomy site (GJ, n = 119). There were four attempted placements (98% success rate). The NJ tubes remained in place an average of 13 days, and the GJ tubes remained in place an average of 37 days. Fluoroscopic time for placement of an NJ tube averaged 6 min (29 cases), and for a GJ tube 8 minutes (91 cases). In spite of the limited retention time, fluoroscopic time, and availability of alternative methods, fluoroscopically placed jejunal feeding tubes are still playing an active role in this institution.

Child, Preschool↗
PubMed1989

Esophageal adenocarcinoma 20 years after esophageal atresia repair.

We report a case of esophageal adenocarcinoma 20 years after esophageal atresia repair. From one case report it is premature to recommend cancer surveillance for all esophageal atresia patients. However, the first survivors are now reaching an age when esophageal cancer related to chronic esophagitis may become more prevalent.

Adenocarcinoma↗