A nationwide cross-sectional study on congenital heart diseases and symptoms of sleep-disordered breathing among Japanese Down's syndrome people.

OBJECTIVE: It is well known that people with Down's syndrome (DS) frequently complicate with congenital heart diseases (CHDs). Patients with heart diseases often have sleep-disordered breathing as a co-morbidity (SDB) which worsens the heart diseases. However, the relationship between SDB and CHDs in DS people has not yet been fully elucidated. The aim of this study was to establish the association between SDB and CHDs in DS people using data from a large nationwide questionnaire survey in Japan. METHODS: We conducted a cross-sectional questionnaire survey of a randomly selected sample of 2,000 DS people and their caregivers throughout Japan to examine the associations between observed signs of SDB and CHDs in DS people. The questionnaire included the presence of SDB symptoms (snoring, apnea, arousal, nocturia, and napping) and CHDs (the presence and types of CHDs). RESULTS: Of the 1,222 replies received from the caregivers, 650 reported complications of some type of CHDs. The observed apnea tended to be higher among DS people with CHDs than those without CHDs (OR=1.28, 95% CI=0.97-1.70, p=0.09). DS people with tetralogy of Fallot reported significantly more frequent apnea than those without CHDs (OR=3.10, 95% CI=1.36-7.05, p<0.01). CONCLUSION: SDB prevailed among DS people with severe CHDs, such as tetralogy of Fallot. Careful attention to the signs of SDB in such patients may lead to earlier clinical intervention removing the vicious cycle between SDB and CHDs.

Water adsorption-desorption isotherms of two-dimensional hexagonal mesoporous silica around freezing point.

Zr-doped mesoporous silica with a diameter of approximately 3.8 nm was synthesized via an evaporation-induced self-assembly process, and the adsorption-desorption isotherms of water vapor were measured in the temperature range of 263-298 K. The measured adsorption-desorption isotherms below 273 K indicated that water confined in the mesopores did not freeze at any relative pressure. All isotherms had a steep curve, resulting from capillary condensation/evaporation, and a pronounced hysteresis. The hysteresis loop, which is associated with a delayed adsorption process, increased with a decrease in temperature. Furthermore, the curvature radius where capillary evaporation/condensation occurs was evaluated by the combined Kelvin and Gibbs-Tolman-Koening-Buff (GTKB) equations for the modification of the interfacial tension due to the interfacial curvature. The thickness of the water adsorption layer for capillary condensation was slightly larger, whereas that for capillary evaporation was slightly smaller than 0.7 nm.

Acquiring non-censored rib fracture data during dynamic belt loading.

The purpose of this paper is to present a method to determine the exact timing of all rib fractures during dynamic belt loading tests on the thorax of human cadavers. In order to generate non-censored rib fracture data, a total of 47 strain gages were placed throughout the thorax of two human cadavers (1 male, 1 female). In order to simulate thoracic loading from a severe car crash, a table-top belt loading device was developed that utilizes a servo-hydraulic test machine to apply a dynamic input. The belt load pulse was configured to result in 40% chest compression through a 150 ms load and unload cycle. Potentiometers and accelerometers measured the chest compression and acceleration at three locations, load cells in line with the belt provided belt loads, and load cells on the posterior side of the thorax measured the reaction loads. The time histories of each strain gage were analyzed to determine the time of fracture which could then be compared directly to the reaction loads and chest displacements at that exact time, thereby creating a non-censored data set. In both cadavers, all fractures (20 for female and 12 for male) occurred within the first 35% compression of the thorax. By utilizing this technique, the exact timing of an injury level can be characterized relative to the mechanical parameters.

Biomechanical response of the human clavicle subjected to dynamic bending.

The purpose of this study was to determine the biomechanical response of human clavicles when subjected to dynamic three-point bending. A total of 10 human cadaver clavicles were tested at an anatomical impact of 0 degrees relative to the transverse plane. Each clavicle was instrumented with a strain gage located under the impactor. Two load cells were used to capture the impactor and reaction loads. The average failure load was 732 +/- 175 N and the average failure moment was 28.3 +/- 7.8 m. The average failure strain was 19738 +/- 2927 microstrain. Using the cross-sectional geometry properties of each bone obtained from CT scans and the strain gage data, the average elastic modulus was 20.8 +/- 5.7 GPa for the linear region of the loading phase. The data presented in this paper is useful to understand clavicle fractures as well as to develop advanced human computational models.

Biomechanical response of the lumbar spine in dynamic compression.

The purpose of this study was to investigate the biomechanical properties of the human lumbar spine subjected to dynamic compression. A series of six experiments using the lumbar spines from four human cadavers was performed. The first two tests utilized the entire lumbar spine while the remaining four tests used lumbar functional joints to separate the differences in stability. A high rate material testing machine was used to produce the dynamic compression at a displacement rate of 1 m/s. Custom mounting plates were developed to ensure proper anatomical position of the lumbar spine sections. Both tests with the whole lumbar spines resulted in compression fractures at T12 due to combined axial loads of 5009 N and 5911 N and bending moments of 237 Nm and 165 Nm respectively. These failures occurred as the spine behaved in first order buckling which resulted in concentrated loading and bending of the anterior aspects of the vertebral bodies. All tests with functional units resulted in endplate fractures and recorded substantially higher axial loads between 11,203 N and 13,065 N and substantially lower bending moments between 47 Nm and 88 Nm. The results indicate that the mechanical stability of the lumbar spine is critical component in relation to the tolerable compressive loads.

Regional variation in the structural response and geometrical properties of human ribs.

By incorporating material and geometrical properties into a model of the human thorax one can develop an injury criterion that is a function of stress and strain of the material and not a function of the global response of the thorax. Previous research on the mechanical properties of ribs has focused on a limited set of specific ribs. For this study a total of 52 rib specimens were removed from four cadaver subjects. Variation in peak moment by thoracic region was significant (p < 0.01) with average values of 2, 2.9 and 3.9 N-m for the anterior, lateral and posterior regions respectively. Two geometrical properties, radius of gyration and distance from the neutral axis, showed significant variation by region (p < 0.0001) as well as by rib level (p = < 0.01, 0.05). The results of this study can be used to update current models of the human thorax to account for the variation in strength and geometrical properties throughout the rib cage. Accounting for the variation in rib properties by region will improve injury predictive measures and, therefore, the ability to design systems to prevent thoracic injury.

On the fatal crash experience of older drivers.

This study describes the fatal crash experiences of older drivers. Data from two U.S. databases (NASS-CDS and FARS) were used. Several crash, vehicle, and occupant characteristics were compared across age groups, including vehicle type, crash direction (PDOF), severity (DeltaV), and injured body region. A sub-set of 97 fatally injured drivers was chosen for a detailed case study. The mean travel speed, DeltaV, and airbag deployment rate decreased significantly with age (p<0.001 unless noted). Mortality rate increased significantly with age. Older drivers killed were significantly more likely to die of a chest injury (47.3% vs. 24.0% in youngest group) and less likely to die of a head injury (22.0% vs. 47.1% in youngest group). Older drivers were more likely to die at a date after the crash date ("delayed death"), as were males (p=0.003). A 16-year-old driver had a 10.8%-12.0% probability of delayed death, while a 75-year-old had a 20.7%-22.7% probability. For those having a delayed death, the length of the delay increased significantly with age (2.9 days for age 16 vs. 7.9 for age 75). A subjective assessment of the case files indicated that frailty or a pre-existing health condition played a role in 4.3% of the younger drivers' deaths, but 50.0% of the older group.

Material properties of human rib cortical bone from dynamic tension coupon testing.

The purpose of this study was to develop material properties of human rib cortical bone using dynamic tension coupon testing. This study presents 117 human rib cortical bone coupon tests from six cadavers, three male and three female, ranging in age from 18 to 67 years old. The rib sections were taken from the anterior, lateral, and posterior regions on ribs 1 through 12 of each cadaver's rib cage. The cortical bone was isolated from each rib section with a low speed diamond saw, and milled into dog bone shaped tension coupons using a small computer numerical control machine. A high-rate servo-hydraulic Material Testing System equipped with a custom slack adaptor, to provide constant strain rates, was used to apply tension loads to failure at an average rate of 0.5 strains/sec. The elastic modulus, yield stress, yield strain, ultimate stress, ultimate strain, and strain energy density were determined from the resulting stress versus strain curves. The overall average of all cadaver data gives an elastic modulus of 13.9 GPa, a yield stress of 93.9 MPa, a yield strain of 0.88 %, an ultimate stress of 124.2 MPa, an ultimate strain of 2.7 %, and a strain energy density of 250.1 MPa-microstrain. For all cadavers, the plastic region of the stress versus strain curves was substantial and contributed approximately 60 % to the strain energy and over 80 % in the tests with the 18 year old cadaver. The rib cortical bone becomes more brittle with increasing age, shown by an increase in the modulus (p < 0.01) and a decrease in peak strain (p < 0.01). In contrast to previous three-bending tests on whole rib and rib cortical bone coupons, there were no significant differences in material properties with respect to rib region or rib level. When these results are considered in conjunction with the previous three-point bending tests, there is regional variation in the structural response of the human rib cage, but this variation appears to be primarily a result of changes in the local geometry of each rib while the material properties remain nearly constant within an individual.

Structural and material changes in the aging thorax and their role in crash protection for older occupants.

The human body undergoes a variety of changes as it ages through adulthood. These include both morphological (structural) changes (e.g., increased thoracic kyphosis) and material changes (e.g., osteoporosis). The purpose of this study is to evaluate structural changes that occur in the aging bony thorax and to assess the importance of these changes relative to the well-established material changes. The study involved two primary components. First, full-thorax computed tomography (CT) scans of 161 patients, age 18 to 89 years, were analyzed to quantify the angle of the ribs in the sagittal plane. A significant association between the angle of the ribs and age was identified, with the ribs becoming more perpendicular to the spine as age increased (0.08 degrees/year, p=0.012). Next, a finite element model of the thorax was used to evaluate the importance of this rib angle change relative to other factors associated with aging. A three-factor, two-level factorial design was used to assess the relative importance of rib cage morphology ("young" and "old" rib angle), thickness of the cortical shell (thick = "young" and thin = "old"), and the bone material properties ("young" and "old") on the force-deflection response and injury tolerance of the thorax. The simulations showed that the structural and material changes played approximately equal roles in modulating the force-deflection response of the thorax. Changing the rib angle to be more perpendicular to the spine increased the effective thoracic stiffness, while the "old" material properties and the thin cortical shell decreased the effective stiffness. The offsetting effects of these traits resulted in similar effective thoracic stiffness for the "elderly" and baseline thoracic models, which is consistent with cadaver data available in the literature. All three effects tended to decrease chest deflection tolerance for rib fractures, though the material changes dominated (a four- to six-fold increase in elements eliminated using a maximum strain criterion). The primary conclusion, therefore, is that an older person's thorax, relative to a younger, does not necessarily deform more in response to an applied force. The tolerable sternal deflection level is, however, much less.

Defining regional variation in the material properties of human rib cortical bone and its effect on fracture prediction.

This paper presents the results of dynamic material tests and computational modeling that elucidate the effects of regional rib mechanical properties on thoracic fracture patterns. First, a total of 80 experiments were performed using small cortical bone samples from 23 separate locations on the rib cages of four cadavers (2 male, 2 female). Each specimen was subjected to dynamic three-point bending resulting in an average strain rate of 5 +/- 1.5 strain/s. Test coupon modeling was used to verify the test setup. Regional variation was defined by location as anterior, lateral, or posterior as well as by rib level 1 through 12. The specimen stiffness and ultimate stress and strain were analyzed by location and rib level. Second, these material properties were incorporated into a human body computational model. The rib cage was partitioned into anterior, lateral, and posterior segments and the material properties were varied by location using an elastic-plastic material model. A total of 12 simulations with a rigid impactor were performed including 2 separate material assumptions, original and modified rib properties for regional variations, 3 separate impactor velocities, and 2 directions, anterior and lateral. The data from the material tests for all subjects indicate a statistically significant increase in the average stiffness and average ultimate stress for the cortical bone specimens located in the lateral (11.9 GPa modulus, 153.5 MPa ultimate stress) portion of the ribs versus the anterior (7.51 GPa, 116.7 MPa) and posterior (10.7 GPa, 127.7 MPa) rib locations. In addition, the stiffness, ultimate stress, and ultimate strain for all subjects are significantly different by rib level with each variable generally increasing with increasing rib number. The results from the computational modeling for both frontal and lateral impacts illustrate that the location and number of rib fractures are altered by the inclusion of rib material properties that vary by region.