Acceleration-induced electrocardiographic interval changes.

C C Whinnery; J E Whinnery

Home/Archive/PubMed

PubMed · 3345170

Acceleration-induced electrocardiographic interval changes.

C C Whinnery·J E Whinnery

View original source ↗Export metadata ↓

Abstract

The electrocardiographic intervals (PR, QRS, QT, and RR) before, during, and post +Gz stress were measured in 24 healthy male subjects undergoing +Gz centrifuge exposure. The PR and QRS intervals responded in a predictable manner, shortening during stress and returning to baseline resting values post-stress. The QT interval, however, was not observed to be dependent solely on heart rate. Bazett's formula, which was developed to correct for heart rate variability, did not adequately result in a homogeneous correction of the QT interval for each stress-related period. During +Gz stress, the QT was shortened, and the QTc prolonged. The QT interval remained shortened even though the heart rate returned to baseline (with the QTc undercorrected) in the post-stress period. The QT (QTc) interval variations probably reflect the effects of both heart rate and autonomic balance during and after +Gz stress, and may provide a measure of the prevailing autonomic (sympathetic or parasympathetic) tone existing at a given point associated with +Gz stress. These electrocardiographic interval changes define the normal response for healthy individuals. Individuals with exaggerated autonomic responses could be identified by comparing their responses to these normal responses resulting from +Gz stress.

Explore related subjects

Acceleration Aerospace Medicine Electrocardiography Heart Rate Humans Male Journal Article

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

C C Whinnery, J E Whinnery. 1988. Acceleration-induced electrocardiographic interval changes.. https://pubmed.ncbi.nlm.nih.gov/3345170/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2004

Determining cavitation location during lumbar and thoracic spinal manipulation: is spinal manipulation accurate and specific?

STUDY DESIGN: Sixty-four asymptomatic participants, ranging in age from 22 to 49 years, volunteered to act as patients for the study. Twenty-eight different clinicians performed thoracic and lumbar spinal manipulative procedures. The range of clinical experience was 1 to 43 years. OBJECTIVES: The purpose of this study is to first locate the joints that produce an audible sound in response to manipulation (cavitation) during spinal manipulative procedures so that the accuracy and specificity of manipulation can be assessed. SUMMARY OF BACKGROUND DATA: Clinicians utilizing spinal manipulative therapy (SMT) claim to be very specific and accurate with the delivery of their dynamic thrust. It has been suggested that the clinical success of SMT is dependent on the accurate delivery of that therapy to the target spinal joints. METHODS: Asymptomatic participants received SMT to either the thoracic or lumbar regions of their spine. Accelerometers were secured to the skin over the spinal column, and the relative time at which each accelerometer detected the vibration from the cavitation associated with the SMT was used to calculate the source of the vibration. The site of cavitation was then compared with the target location. RESULTS: For lumbar SMT, the average error from target of 124 cavitations in lumbar procedures was 5.29 cm (at least one vertebra away from target), with a range of 0 to 14 cm. Of these cavitations, 57 were deemed to be accurate and 67 were deemed to be inaccurate. The average error from target of 54 cavitations in the thoracic spine was 3.5 cm, with a range of 0 to 9.5 cm. Of these cavitations, 29 were deemed to be accurate and 25 were deemed to be inaccurate. In most cases, individual manipulative procedures were associated with multiple cavitations ranging from 2 to 6. CONCLUSIONS: In the lumbar spine, SMT was accurate about half the time. However, because most procedures were associated with multiple cavitations, in most cases, at least one cavitation emanated from the target joints. In the thoracic spine, SMT appears to be more accurate.

Acceleration↗

PubMed2004

Airflow synchronous with oscillatory acceleration reflects involuntary respiratory muscle activity.

To explore mechanisms causing involuntary airflow synchronous with oscillatory axial whole body acceleration (oscillatory axial acceleration, OAA) such as that during locomotion, we monitored airflow, acceleration, and electromyograms (EMGs) of the rib cage and abdominal muscles in standing subjects undergoing OAA at 3, 6, and 9 Hz at accelerations of 0.1-0.95 g. Subjects relaxed or performed static respiratory maneuvers at constant lung volume with glottis open. Oscillatory airflows (0.01-3.01 s(-1)) synchronous with OAA were not consistent with expectations for a passive respiratory system, and were larger during active respiratory efforts than during relaxation. Peak inspiratory airflow usually preceded peak upward acceleration by 90-180 degrees. In 80% of runs with respiratory muscles voluntarily activated or relaxed, EMGs showed activity synchronous with OAA. Changes in periodic muscle activity coincided with changes in oscillatory airflow. We conclude that periodic muscle activity, probably a reflex response to body wall deformation during OAA, strongly influences the involuntary airflow synchronous with OAA.

Acceleration↗

PubMed2004

In vitro low-speed side collisions cause injury to the lower cervical spine but do not damage alar ligaments.

Whether injuries to the alar ligaments could be responsible for complaints of patients having whiplash injury in the upper cervical spine is still controversially discussed. It is known that these ligaments protect the upper cervical spine against excessive lateral bending and axial rotation movements. The objective of the present in vitro study was therefore to examine whether the alar ligaments or any other structures of the cervical spine are damaged in side collisions. In a specially designed acceleration apparatus, six human osteoligamentous cervical spine specimens were subjected to incremental 90 degrees side collisions from the right (1 g, 2 g, 3 g, etc.) until structural failure occurred. A damped pivot table accounted for the passive movements of the trunk during collision, and a dummy head (4.5 kg) ensured almost physiological loading of the specimens. For quantification of functional injuries, the three-dimensional flexibility of the specimens was tested in a spine tester before and after each acceleration. In all six specimens, structural failure always occurred in the lower cervical spine and always affected the facet joint capsules and the intervertebral discs. In four specimens, this damage occurred during the 2 g collision, while in the other two it occurred during the 3 g and 4 g collision, respectively. The flexibility mainly increased in the lower cervical spine (especially in lateral bending to both sides) and, to a minor extent, in axial rotation. In vitro low-speed side collisions caused functional and structural injury to discoligamentous structures of the lower cervical spine, but did not damage the alar ligaments. Since the effects of muscle forces were not taken into account, the present in vitro study reflects a worst-case scenario. Injury thresholds should therefore not be transferred to reality.

Acceleration↗