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PubMed1992

The effect of measurement conditions on MCG inverse solutions.

A magnetic inverse solution that uses a single current dipole in a homogeneous volume conductor with realistic torso shape was tested numerically to establish the effect of magnetic noise, number of measurement points, and torso size on the localization accuracy. Seven different sites of cardiological interest were selected as locations for the source dipole. The three components of the magnetic field were calculated as if measured by second order gradiometers, Gaussian noise was added, and Monte Carlo tests performed for inverse solutions using a single field component, or all three combined. It was found that for any of the single component solutions, and a signal-to-noise ratio of 100, 25 measuring points are sufficient for good accuracy; just 12 points are needed if all three components are used together. If, however, the torso size of the inverse solution is different from that of the field data by 10 or 20%, a larger error occurs, even for 56 measurement points and no noise. In this case, the field component orthogonal to the measurement grid, Bz, yields better results than the other two components, or even all three combined. We conclude that a multichannel system measuring the z component of the magnetic field in about 30 locations would be the best choice to locate a dipolar source, provided the torso of the field data is closely matched by the model used in the inverse solution. To this effect, scaling of the torso model can easily be included in the computation. Imaging techniques could be used to accommodate different torso shapes.

Bias↗
PubMed1996

On the contribution of volume currents to the total magnetic field resulting from the heart excitation process: a simulation study.

Data from a simulation study of volume current contribution to the total magnetic field produced in the heart excitation process is presented. Contributions from different tissue types are analyzed and effects of torso size are studied. A high resolution finite element model of an adult male torso composed of 19 tissue types is used. It has detailed description of tissue geometries and therefore is well suited for analyzing the contribution of the primary and secondary currents to the magnetic field. The computed results show major contribution of volume currents from blood, myocardium, and lungs and less significant contribution from liver, muscle, and other tissues. The contribution to the volume currents from the blood in the ventricles was highest. These simulations suggest that contribution to the total magnetic field due to volume currents flowing in tissues other than blood could be accounted for by simply multiplying the total field values by a constant. Values of these multipliers would be based on the tissue type and time in the excitation cycle. Effects of torso size on the computed magnetic fields are also evaluated. Our data shows that a torso extending approximately 3 cm above and below the heart produces field patterns similar to a larger torso model extending from top of guts to the bottom of neck. Thus a shorter torso model would be sufficient for cardiac magnetic field analysis. These results are of interest for future modeling of magnetocardiograms and solving the inverse problem.

Adult↗
PubMed1991

An assessment of variable thickness and fiber orientation of the skeletal muscle layer on electrocardiographic calculations.

This paper assesses the effectiveness of including variable thickness and fiber orientation characteristics of the skeletal muscle layer in calculations relating epicardial and torso potentials. A realistic model of a canine torso which includes extensive detail about skeletal muscle layer thickness and fiber orientation is compared with two other uniformly anisotropic models: one of constant thickness and the other of variable thickness. First, transfer coefficients are calculated from the model data. Then torso potentials for each model are calculated from the transfer coefficients and measured epicardial potentials. The comparison of calculated and observed torso potentials indicates that a simple model consisting of a uniformly anisotropic skeletal muscle layer of 1.0-1.5 cm constant thickness significantly improves the model. However, if photographic slices of the canine torso are used to introduce more detailed data about the variation in skeletal muscle thickness and fiber orientation into the model, the agreement and between calculated and measured torso potentials decreased, although a finite element mesh of over 5000 nodes was used to describe the skeletal muscle in the more detailed model. One source of error increase was considered to be due to numerical discretization and could be reduced with a much finer mesh or by utilizing higher order polynomials to represent the potential distribution within each finite element. However, the results presented in this paper show that high precision computation (64-bit word length) on the mainframe IBM 3081 with an attached FPS-164 gives a slow rate of improvement with reduced discretization intervals and that utilizing higher order polynomials within each finite element gives an even slower rate of improvement.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Estimation of regional cutaneous cold sensitivity by analysis of the gasping response.

Regional cutaneous sensitivity to cooling was assessed in males by separately immersing four discrete skin regions in cold water (15 degrees C) during head-out immersion. The response measured was gasping at the onset of immersion; the gasping response appears to be the result of a nonthermoregulatory neurogenic drive from cutaneous cold receptors. Subjects of similar body proportions wore a neoprene "dry" suit modified to allow exposure to the water of either the arms, upper torso, lower torso, or legs, while keeping the unexposed skin regions thermoneutral. Each subject was immersed to the sternal notch in all four conditions of partial exposure plus one condition of whole body exposure. The five cold water conditions were matched by control immersions in lukewarm (34 degrees C) water, and trials were randomized. The magnitude of the gasping response was determined by mouth occlusion pressure (P0.1). For each subject, P0.1 values for the 1st min of immersion were integrated, and control trial values, although minimal, were subtracted from their cold water counterpart to account for any gasping due to the experimental design. Results were averaged and showed that the highest P0.1 values were elicited from whole body exposure, followed in descending order by exposures of the upper torso, legs, lower torso, and arms. Correction of the P0.1 response for differences in exposed surface area (A) and cooling stimulus (delta T) between regions gave a cold sensitivity index [CSI, P0.1/(A.delta T)] for each region and showed that the index for the upper torso was significantly higher than that for the arms or legs; no significant difference was observed between the indexes for the upper and lower torso.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Influence of localized auxiliary heating on hand comfort during cold exposure.

There is a need for a hand-heating system that will keep the hands warm during cold exposure without hampering finger dexterity. The purpose of this study was to examine the effects of torso heating on the vasodilative responses and comfort levels of cooled extremities during a 3-h exposure to -15 degreesC air. Subjects were insulated, but their upper extremities were left exposed to the cold ambient air. The effect of heating the torso [torso-heating test (THT)] on hand comfort was compared with a control condition in which no torso heating was applied, but Arctic mitts were worn [control test (CT)]. The results indicate that mean finger temperature, mean finger blood flow, mean toe temperature, mean body skin temperature, body thermal comfort, mean finger thermal comfort, and rate of body heat storage were all significantly (P < 0.05) higher on average (n = 6) during THT. Mean body heat flow was significantly (P < 0.05) lower during THT. There were no significant differences (P >/= 0.05) in rectal temperature between CT and THT. Mean unheated body skin temperature and mean unheated body heat flow (both of which did not include the torso area in the calculation of mean body skin temperature and mean body heat flow) were also calculated. There were no significant differences (P >/= 0.05) in mean unheated body skin temperature and mean unheated body heat flow between CT and THT. It is concluded that the application of heat to the torso can maintain finger and toe comfort for an extended period of time during cold exposure.

Adult↗
PubMed2003

Imaging electrocardiographic dispersion of depolarization and repolarization during ischemia: simultaneous body surface and epicardial mapping.

BACKGROUND: Myocardial ischemia creates abnormal electrophysiological substrates that result in life-threatening ventricular arrhythmias. Identifying patients at risk of such abnormalities by use of body surface electrical measures is controversial. We investigated the sensitivity of torso measures, recorded simultaneously with epicardial electrograms, to changes in dispersion of depolarization and repolarization during localized ventricular ischemia. METHODS AND RESULTS: Ventricular epicardial electrograms were recorded from 5 anesthetized pigs with a 127-electrode sock. A controllable suture snare was used to ligate the left anterior descending coronary artery (LAD). The chest was reclosed, and a vest with 256 ECG electrodes was fitted to the torso. Simultaneous arrays of epicardial electrograms and torso ECGs were recorded during LAD occlusion and reperfusion. Activation-recovery intervals (ARIs), QTu and RTu dispersion (where u indicates upstroke), and QRST integrals were calculated, and these data were fitted to anatomically customized computational models of the swine ventricular epicardium and torso. LAD occlusion caused the epicardial ARI dispersion to steadily increase, whereas the location of shortest ARI shifted from the posterobasal ventricular tissue (control) to the anteroapical myocardium, distal to the suture snare. These changes were associated with a steady increase in the torso RTu dispersion as the shortest RTu interval moved from the right shoulder (control) to the sternum. QTu and RTu dispersion determined from the 12-lead ECG did not consistently reflect the myocardial changes. CONCLUSIONS: Although changes in myocardial repolarization dispersion resulting from localized ischemia are not reliably reflected in temporal indices derived from the 12-lead ECG, they can be readily identified with high-resolution torso ECG mapping.

Animals↗
PubMed2000

Evaluating the role of physical and radiographic examinations in assessing bullet tract termination for gunshot victims.

Knowledge of the path of a bullet and how it terminates is critical for expeditious assessment and optimal management of patients with gunshot wounds. To assess the accuracy of physical examination and X-rays in these patients, a prospective study was undertaken for all gunshot victims seen for a 1-year period on a single trauma service. The paramedics and trauma surgeons' physical examinations were evaluated for whether a bullet tract could be accurately categorized as 1) through and through, 2) graze, 3) palpable under dermis, or 4) retained (ie, not palpable). The impact of X-rays was assessed with regard to how it affected the trauma surgeons' categorization. A total of 78 patients were seen with a total of 120 bullet tracts. Seventy-seven per cent were injured by assault, and 64 per cent were shot with a 9-mm or .38-caliber handgun. Twenty of 60 (33%) bullet tracts on the torso terminated with a missile that was palpable under dermis, but only 2 of 10 neck (20%), 1 of 28 extremity (4%), and 1 of 22 head/face (5%) did so. Paramedics evaluated 15 torso bullet tracts that ended palpable under dermis, of which they detected 5 (33%). Upon initial examination, the trauma surgeon detected 11 of 20 torso bullet tracts that ended palpable under dermis (55%), and detected 14 of the 20 after X-rays were done (70%). Overall, obtaining X-rays changed the categorization for 15 of 111 bullet tracts (13%). We conclude that bullet tracts on the torso result in a subcutaneously palpable bullet one-third of the time, much more frequently than in other body regions. Paramedics only detect one-third of subcutaneously palpable missiles on the torso. X-rays change the categorization of bullet tracts infrequently. We recommend that a careful examination of the skin of the torso to detect palpable missiles be incorporated into the secondary survey of patients with wounds to that body region.

Allied Health Personnel↗
PubMed1999

Isoflurane indirectly depresses middle latency auditory evoked potentials by action in the spinal cord in the goat.

PURPOSE: The auditory evoked potential (AEP) has been proposed as a method to determine depth of anesthesia, as AEPs are generated in the thalamus and cerebral cortex. Because general anesthesia, in part, relies on anesthetic action in the spinal cord, we hypothesized that isoflurane would have indirect depressant effects on the AEP because of its action in the spinal cord. METHODS: Six goats were anesthetized with isoflurane and the jugular veins and carotid arteries isolated to permit cerebral bypass and differential delivery of isoflurane to the head and torso. The AEPs were determined by delivering binaural clicks at 9 Hz, and measuring the evoked response from electrodes placed in the skull and scalp. Isoflurane was maintained at 0.8% in the head while the torso isoflurane was alternated between 0.3% and 1.3%, and the AEP determined at each torso concentration. RESULTS: At isoflurane 0.3% delivered to the torso, the peak-to-trough amplitude of the mid-latency AEP waves designated as N14/P24 was 0.337+/-0.185 microV and the N36 wave amplitude was 0.115+/-0.054 microV. When torso isoflurane was 1.3%, these waves decreased to 0.297+/-0.186 microV and 0.066+/-0.037 microV, respectively (P<0.05). The latency of the N14 wave increased slightly (from 13.7+/-2.6 msec to 14.4+/-2.8 msec, P<0.05) but the latencies of the other waves were unchanged. CONCLUSIONS: Isoflurane action in the spinal cord indirectly alters the AEP, however, the effect is small. These data suggest that isoflurane can depress the transmission of afferent information from the spinal cord to thalamus, midbrain and cerebral cortex.

Anesthetics, Inhalation↗
PubMed2001

Relationships between seat properties and human subject kinematics in rear impact tests.

The mitigation of whiplash associated disorders (WAD) has received increased priority in the last 10 years. Although the exact mechanism(s) for WAD causation have not been established, several have been proposed and it is likely the mechanism(s) are associated with the kinematics of the head relative to the torso. It follows that automotive seat designs that address reductions in certain head-torso kinematics may lead to a reduction in WAD potential. Seat properties that may have an effect on head-neck kinematics include geometry, stiffness and energy absorption. This study evaluated the performance of five seats with varying properties, including the new Volvo 'WHIPS' seat. Seat properties such as geometry relative to the occupant's head, dynamic and static stiffness, and energy absorption were determined via component testing. A new prototype dynamic seat test, which used a pendulum and seat back pan, was evaluated. Human subject impact tests were conducted using three occupants in rear impacts with velocity changes of 4 and 8 km/h. Potentially relevant occupant kinematic parameters were identified, and then correlated with seat properties in an attempt to determine any relative influence of seat properties on potential WAD mechanisms. Two higher velocity human subject tests using the Volvo Whiplash Injury Protection System (WHIPS) seat were also conducted. Vertical and horizontal head to head restraint distances were found to be most influential on occupant head-neck kinematics. Horizontal and vertical head to head restraint offsets were significantly correlated with rearward translational motion of the head center of gravity relative to the upper torso across all occupants. Rearward offset was also significantly correlated with rearward rotation of the head relative to upper torso, while vertical offset was significantly correlated with head acceleration relative to the upper torso during the flexion phase of the impact. Seat constitutive properties such as stiffness and energy absorption were not significantly correlated with occupant head-neck kinematics. The new dynamic seat test posed problems in data interpretation, and suggestions for improvement are made. The Volvo 'WHIPS' seat proved to be very effective in reducing many potential WAD associated head-neck kinematics. The two increased severity impacts activated the additional protective energy absorption elements in the seat, and no injuries were sustained by the occupants.

Acceleration↗
PubMed1999

Radiation safety with breast sentinel node biopsy.

BACKGROUND: Sentinel lymph node biopsy with Technetium 99m sulfur colloid (Tc99m) is an evolving technique that offers the potential for improved staging of breast cancer with decreased morbidity. However, the use of radioactive materials in the operating room generates significant concern about radiation exposure. The purpose of this study was to evaluate radiation exposure to operating room personnel, pathologist, and equipment from specimens during breast sentinel lymph node biopsy. METHODS: Twenty patients were injected with 0.7 to 1.1 mCi of Tc99m sulfur colloid 1.5 to 3 hours before sentinel lymph node biopsy. A calibrated Geiger counter was used to measure dose rates from the breast injection site before skin incision (n = 20), lumpectomy specimens (n = 8), and sentinel nodes (n = 20) at distances of 3, 30, and 300 cm. This represented exposure to the surgeon's hands, surgeon's torso, and scrub nurse, respectively. Exposure to the pathologist's hands and torso was represented as dose-rate measurements from lumpectomy and nodal specimens. The operative instruments, trash receptacles, suction canisters, pathology slides, and cryostat machines were measured at 3 cm at the conclusion of each procedure. Specimens or equipment emitting radiation doses equal to background levels (0.04 mRem/h) were exempt from special handling and disposal. RESULTS: The highest exposure rate was to the surgeon's hands from the breast injection site before skin incision (34.25 mRem/h). Exposure to the surgeon's torso measured 1.33 mRem/h, and exposure to the scrub nurse's torso measured 0.15 mRem/h from the injection site. Exposure to the pathologist's hands was 18.62 and 0.06 mRem/h from the lumpectomy specimen and sentinel node, respectively. Exposure to the pathologist's torso measured 0.34 and 0.04 mRem/h from the lumpectomy specimen and sentinel node, respectively. One hundred percent of lumpectomy specimens measured above the exempt level. Thirty-two of 46 (70%) sentinel lymph nodes emitted radiation equal to the exempt background level. Seventeen of 20 trash receptacles (85%) and 4 of 12 (33%) suction canisters measured equal to background levels. All operative instruments, pathology slides, and cryostat machines were equal to background levels. CONCLUSIONS: Radiation exposure to operating room personnel, pathologists, and operative equipment during a breast sentinel node biopsy using Tc99m is minimal. A primary surgeon can perform 2,190 hours, a scrub nurse 33,333 hours, and a pathologist 14,705 hours of procedural work before surpassing Occupational Safety and Health Administration limits. Operative instruments, pathology slides, and cryostat machines do not require special handling. All lumpectomy specimens should be stored for decontamination until the dose rate equals background levels. Intraoperative dose-rate monitoring allows selective decontamination of nodal specimens, trash receptacles, and suction canisters, which decreases disposal time and cost.

Air Pollutants, Radioactive↗
PubMed1996

Accurate anatomical location of war injuries: analysis of the Lebanon war fatal casualties and the proposition of new principles for the design of military personal armour system.

In this study we present a new approach to the design of the military personal armour system (MPAS). This approach is based on a computerized analysis of the exact anatomical location of 405 penetrating war injuries (290 shrapnel and 115 bullet injuries) in 164 soldiers killed in the Lebanon war. All the penetrating injuries (hits) were plotted on a computerized image of the human body. About 90 per cent of all hits were to the front of the body; 55 per cent of all hits were to the left side. About 45 per cent of all hits were to the torso, which is slightly more than the torso's proportion of total body-surface area (36 per cent). Of all hits to the torso, 64 per cent of the shrapnel hits and 73.3 per cent of the bullet hits were limited to the front mid torso (T4 to T9). The head at the level of the helmet received 9 per cent of all hits, most of which were over the frontal bones (72.4 per cent). The body part with the greatest density of penetrating injuries was the face, with 22.2 per cent of all penetrating wounds, and in particular the mid face, from the level of the lips to the level of the zygomatic bones, was especially vulnerable, sustaining 10 per cent of all the penetrating wounds. These findings suggest several possible modifications in the standard MPAS: an additional protective device over the front mid torso may be incorporated; the face may be protected by a transparent and lightweight face-shield; a horizontal margin added to the standard helmet may protect the upper face from missiles from above; a chin cover may protect the lower face.

Blast Injuries↗
PubMed1984

Temporal evolution of body surface map patterns following acute inferior myocardial infarction.

We studied the evolution of body-surface potential map (BSPM) patterns in 32 patients following first acute inferior myocardial infarction. Initial BSPMs were obtained at a mean of 79 hours post-infarction; follow-up BSPMs, a mean of eight months post-infarction. Temporal area-of-difference maps, constructed by subtracting initial from follow-up group-mean BSPMs, revealed reciprocal changes over the superior and inferior torso for both Q-zone and ST-segment time-integral distributions. The temporal changes in Q-zone patterns were small but definite: over the inferior torso there was a relative gain in Q-zone values and, over the superior torso, a relative decrease. In contrast, there were marked spatial and quantitative changes of ST-segment distributions during the follow-up period. Over the superior torso, particularly anteriorly, there was a gain in ST-segment values; over the inferior torso, a decrease. With the small temporal changes in Q-zone time-integral distributions, individual Q-zone maps continued to reflect a pattern of inferior myocardial infarction at follow-up. In contrast, the marked temporal changes in ST-segment time-integral distributions resulted in individual map patterns at follow-up that were nearly indistinguishable from normal ST-segment maps. The relatively small changes in depolarization time-integral patterns during the early post-infarction period suggest that the Q-zone patterns of the acute phase of myocardial infarction reflect near-irreversible or completed myocardial damage. The marked normalization of repolarization time-integral patterns during the recovery phase suggests, however, that there are also considerable areas of myocardium-at-risk during the early phase of the infarction process which stabilize with time.

Adult↗
PubMed1999

Noninvasive indices of repolarization and its dispersion.

In experimental studies using Langendorff perfused, isolated canine hearts immersed in a torso-shaped electrolytic tank we studied repolarization and its dispersion using direct epicardial measurements and newly derived, noninvasive body surface indices. Activation recovery intervals (ARIs) measured from 64 epicardial sites based on differences between activation times (ATs) and recovery times (RTs) provided direct measures of repolarization. The indirect, torso surface indices were derived from inflections of the root-mean-square (RMS) voltage of the torso tank surface electrocardiograms recorded simultaneously with the epicardial data. For cycle lengths ranging from 300 to 900 ms, and electrolyte temperatures ranging from 32 degrees C to 40 degrees C we calculated mean, variance, and range of ATs, RTs, and ARIs from the epicardium. From epicardial and torso surface RMS waveforms, we used times of R and T peaks and their differences to estimate mean ATs, RTs, and ARIs, respectively. The RMS T wave width as determined from the second derivative inflections on either side of the T peak served as an estimate of the dispersion of RTs. In parallel studies, we showed that the direct measures of repolarization and its dispersion were reflected in RMS waveforms generated from the epicardial electrograms themselves. In this study, we confirm that the torso and epicardial RMS waveforms reflect comparable information for estimating repolarization and its dispersion. Furthermore, the derived measures provide a method to assess mean ARIs and dispersion of RTs on a beat-to-beat basis and during abnormal (ectopic ventricular) activation sequences.

Animals↗
PubMed1997

Comparison of two repositioning devices used during radiation therapy for Hodgkin's disease.

PURPOSE: Patients irradiated for Hodgkin's disease are fixed in an immobilization cradle to improve repositioning. In the early 1990s, we changed our cradle system from a "short" upper torso cradle to an extended near-total body cradle that also includes the lower torso and thighs. In this study, we assess the impact of the extended cradle on the reproducibility of patient repositioning during irradiation of Hodgkin's disease. METHODS AND MATERIALS: A total of 782 port films of 56 patients treated immediately before and after the change-over were studied to assess positioning reproducibility. Patients treated prior to 1993 were positioned in the short cradle, while those treated 1993 and later were positioned in the extended cradle. All treatment were delivered via anterior and posterior fields and treatment areas above and below the diaphragm were considered separately and together. All treatment fields were simulated and the field shape was designed on anterior and posterior radiographs. Discrepancies in field placement between the simulation radiographs and subsequent port films were noted by a radiation oncologist and requests for position adjustment (both translational and rotational shifts) were noted. The number, magnitude, and direction of any physician-requested position adjustment on port films were retrospectively reviewed. For the purpose of scoring the frequency of field misplacements, when an adjustment was noted on two port films taken during the same treatment session (i.e., a left shift on both an anterior and a posterior port film), it was scored as only one event. A two-tailed chi-square test was used to compare the differences in requested shifts in the two patient groups. RESULTS: The study population consisted of 56 patients (31 short and 25 extended cradle) representing 92 treatment sites. A total of 782 port films representing 450 treatment setups were analyzed (292 above and 158 below the diaphragm). When all port films above the diaphragm (mostly mantle fields) are considered, position adjustments were requested in 13.4% (21 out of 157) of treatment setups with the upper torso cradle and in 5.9% (8 out of 135) of treatment setups with the extended cradle (p = 0.054). When all port films below the diaphragm (mostly paraaortic/spleen and pelvic fields) are considered, position adjustments were requested in 33.8% (27 out of 80) of treatment setups with the upper torso cradle and in 16.7 % (13 out of 78) of treatment setups with the extended cradle (p = 0.056). A reduction in the frequency of both translational and rotational adjustments were seen. When both treatment sites are combined, position adjustments were requested in 20.3% (48 out of 237) of treatment setups with the upper torso cradle and in 9.9% (21 out of 213) of treatment setups when the extended cradle was used (p = 0.0086). CONCLUSIONS: The extended cradle provides superior repositioning of patients undergoing radiation therapy for Hodgkin's disease. Differences observed in setup accuracy in this study underscore the importance of aggressive immobilization of patients with Hodgkin's disease. Increased accuracy of daily setup may provide an opportunity to improve the therapeutic ratio both by increased likelihood of tumor control and decreased risk of normal tissue complications.

Equipment Design↗
PubMed1994

Biomagnetic localization of electrical current sources in the human heart with realistic volume conductors using the single-current-dipole model.

The boundary element method was applied in order to investigate the localization accuracy for focal sources measured from MCG data. Various homogeneous volume conductor models were composed: the individually shaped torso, a scaled standard torso, an unscaled standard torso, a scaled cuboid and a scaled ellipsoid. We implemented these models in single-dipole inverse solution techniques. High resolution multichannel data were analysed from two patients showing ventricular extrasystoles and two patients suffering from Wolff-Parkinson-White syndrome. Moreover, we report the localization of shallow- and deep-lying catheters (depth 9 cm and depth 17.5 cm below the measurement grid). Using an individually shaped homogeneous torso yields a localization error of less than 3 cm even for the deepest sources (mean error 2.4 cm). Probability-based dipole localization shows that the remaining error could only partly be explained by data noise statistics. Therefore it seems to be due to either inner inhomogeneities or the inadequacy of the single current dipole or a combination of the two. Thus clinically useful localization accuracy in the millimetre range requires more sophisticated volume conductor and source models. The evaluation of measurement data and simulation study shows that a scaled cuboid model can provide nearly the same localization accuracy as the individually shaped torso model. Single dipole reconstruction with this model is computationally faster than that with the individually shaped model of the human body and is fast enough for use in clinical applications.

Arrhythmias, Cardiac↗
PubMed2004

Efficacy of side air bags in reducing driver deaths in driver-side collisions.

Side air bags, a relatively new technology designed to protect the head and/or torso in side-impact collisions, are becoming increasingly common in automobiles. Their efficacy in preventing US driver deaths among cars struck on the near (driver's) side was examined using data from the Fatality Analysis Reporting System and the General Estimates System. Risk ratios for driver death per nearside collision during 1999-2001 were computed for head/torso and torso-only side air bags in cars from model years 1997-2002, relative to cars without side air bags. Confounding was addressed by adjusting nearside risk ratios for front- and rear-impact mortality, which is unaffected by side air bags. Risk ratios were 0.55 (95% confidence interval: 0.43, 0.71) for head/torso air bags and 0.89 (95% confidence interval: 0.79, 1.01) for torso-only air bags. Risk was reduced when cars with head/torso air bags were struck by cars/minivans (significant) or pickup trucks/sport utility vehicles (nonsignificant). Risk was reduced in two-vehicle collisions and among male drivers and drivers aged 16-64 years. Protective effects associated with torso-only air bags were observed in single-vehicle crashes and among male and 16- to 64-year-old drivers. Head/torso side air bags appear to be very effective in reducing nearside driver deaths, whereas torso-only air bags appear less protective.

Accidents, Traffic↗
PubMed1993

Effect of posture on lung and regional chest wall mechanics.

BACKGROUND: Little is known about the extent to which changes in postures in clinical situations affect respiratory mechanics, even in humans with healthy respiratory systems. This study tested the hypothesis that posture has only small effects on overall respiratory system mechanics in healthy subjects, despite changes in parts of the respiratory system in some postures. METHODS: Measurements were made of airway flow, airway and esophageal pressures, and rib cage and abdominal volume displacements (with inductance plethysmography) of awake, healthy subjects, relaxed at functional residual capacity, during external forcing at 0.2 Hz with a tidal volume of 8-10 ml/kg. From these measurements, discrete Fourier transform was used to calculate elastances (E) and resistances (R) of the total respiratory system, lungs, total chest wall, and compartments of the chest wall (rib cage, diaphragm-abdomen, and belly wall). Measurements were made while the subjects were in nine different postures: in six of these, the torso was straight; in three, the torso was bent or twisted. RESULTS: Although changes in mechanics of parts of the respiratory system were evident in certain postures, overall respiratory mechanics were not greatly affected by posture. Changing from sitting to supine decreased E and R of the diaphragm-abdomen about 50% (P < .05), but total chest wall E and R changed only slightly. Lung E increased 24% (P < .05), but total respiratory E did not change (P < .05). Lung and total respiratory R increased 40-50% (P < .05) with this same change in posture. As long as the torso was straight, however, changes in orientation of 30 degrees from the horizontal or a shift to lateral posture resulted in only minor changes in the variables measured. Postures in which the torso was twisted or bent increased E of the total chest wall 20-30% compared to supine (P < .05), due to increases in E of one or more compartments. Respiratory system E also increased, at most 14%. Although lung R decreased 30-45% (P < .05) in these postures compared to supine with a straight torso, chest wall and total respiratory R generally were unchanged. CONCLUSIONS: Changes in respiratory system mechanics over a wide range of postures that may be encountered clinically are relatively small in healthy awake subjects due to adaptability of total chest wall mechanical behavior.

Adult↗
PubMed1995

The effects of lateral trunk bending on muscle recruitments when resisting nonsagittally symmetric bending moments.

STUDY DESIGN: Surface electromyographic activities were measured in 15 subjects as they maintained a static laterally bent trunk posture and resisted sagittally symmetric and asymmetric moments applied to their torsos. The moment magnitudes were 20 and 40 Nm and had transverse plane directional components in 30 degrees increments surrounding the subjects' torsos. OBJECTIVES: To quantify the myoelectric responses from eight trunk muscles as asymmetric loads were applied to the laterally bent torso. SUMMARY OF BACKGROUND DATA: Asymmetric material handling frequently results in lateral bending of the torso. Each of these factors have been linked via epidemiologic investigations to the incidence of low back disorders. Little information is available that describes the response of the trunk muscles when the trunk is bent to the side. METHODS: Subjects stood in a reference frame and adjusted their trunk posture to marks on a video display that indicated when a 20 degrees lateral bend to the right had been achieved. Moments were applied to the torso by connecting weights via cables and pulleys to a chest harness. Electromyographic activities were recorded bilaterally from the erector spinae, latissimus dorsi rectus abdominis, and external oblique muscles. RESULTS: The electromyographic data indicated that the muscles showed the greatest activity when they were in opposition to the applied sagittal and frontal plane moments. The left external oblique showed the greatest response and was sensitive to the widest range of moment direction conditions. All of the muscles, except for the left latissimus dorsi, at times contributed antagonistic moments in the sagittal plane or the frontal plane, or in both planes. These data were compared with previously obtained data from an upright neutral posture. CONCLUSIONS: Statistical analyses indicated that the responses of both external obliques and the left erector spinae to the moment direction conditions were significantly different between the laterally bent and neutral postures.

Abdominal Muscles↗