Annals of biomedical engineering
-
Comparative Study
Estimation of breathing rate from respiratory sinus arrhythmia: comparison of various methods.
Although respiratory sinus arrhythmia (RSA) is a well-known and often studied phenomenon, methods to estimate (average) respiratory rate from heart rate variability via RSA have been investigated and published only sparsely. We reinvestigate three published techniques and contrast them to our own approaches. All methods were also evaluated for respiration signals to yield approximations of the true breathing rate for comparison. ⋯ Results show that the RSA of young supine subjects yields good approximations of mean respiratory rate in the case of time series longer than 1 min, while the estimations become noticeably less accurate for elderly persons. Our own "advanced counting method" produced the best results, and in addition principally permits even the definition of instantaneous respiratory rates. Consequently, it is recommended for further investigations.
-
Biomechanical studies using postmortem human subjects (PMHS) in lateral impact have focused primarily on chest and pelvis injuries, mechanisms, tolerances, and comparison with side impact dummies. A paucity of data exists on the head-neck junction, i.e., forces and moments, and cranial angular accelerations. The objective of this study was to determine lateral impact-induced three-dimensional temporal forces and moments at the head-neck junction and cranial linear and angular accelerations from sled tests using PMHS and compare with responses obtained from an anthropomorphic test device (dummy) designed for lateral impact. ⋯ Fractures to the head-neck complex were not identified in PMHS tests. Peak cranial angular accelerations were suggestive of mild traumatic brain injury with potential for loss of consciousness. Findings from this study with a limited dataset are valuable in establishing response corridors for side impacts and evaluating side impact dummies used in crashworthiness and safety-engineering studies.
-
The spinal cord may be injured through various spinal column injury patterns (e.g., burst fracture, fracture dislocation); however, the relationship between column injury pattern and cord damage is not well understood. A three-dimensional finite element model of a human cervical spine and spinal cord segment was developed, verified using published experimental data, and used to investigate differences in cord strain distributions during various column injury patterns. ⋯ For a dislocation injury, as would occur in a fracture dislocation, an anterior displacement of C5 corresponding to 30% of the sagittal dimension of the vertebral body resulted in high peak strain values adjacent to the shearing vertebrae and increased strains in the lateral columns compared to contusion. This model includes more anatomical details compared to previous studies and provides a baseline for mechanical comparisons in spinal cord injury.
-
The extension of neurites on 2D collagen-coated substrates and within 3D collagen gels is based on various chemical and mechanical environmental factors. However, extrapolating results from 2D studies to 3D environments are difficult, especially with regard to neural outgrowth. The aim of this study was to investigate the effects of inhibitory molecules on nerve growth in 3D environments as compared to 2D surfaces. ⋯ In contrast, on 2D surfaces, both RGD peptides reduced the number of cells expressing neurites, but cRGD still exhibited superior inhibition of neurite expression. Further evaluation of cRGD results revealed that the peptide altered neurite growth vs. stiffness to a more linear relationship that is more typical of non-adhesive environments. Overall, these results further demonstrate the importance of peptide confirmation and sequence when investigating cell behavior in 3D environments.
-
Micropattern dimensions can significantly influence neurite outgrowth orientation, rate, and length. Laminin micropatterns of various widths from 10 to 50 microm at 10 microm intervals separated by 40 microm spaces were generated on poly(methyl methacrylate) surfaces using microscale plasma-initiated patterning (microPIP). Dissociated dorsal root ganglion (DRG) neurons were seeded on the micropatterned surfaces and cultured for 24 h in serum-free media. ⋯ Neurites at 40 microm laminin pattern widths demonstrated the fastest outgrowth rates and were highly oriented. The 40 microm laminin dimension is wide enough to provide sufficient laminin amounts for neuron growth and narrow enough to efficiently guide neurites. Based on these results, adhesive protein micropatterns of 40 microm dimensions are recommended when investigating DRG neurons.