Browsing by Subject "MSNA"
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Item A CASE FOR A STANDARDIZED METHOD FOR THE NORMALIZATION OF MUSCLE SYMPATHETIC NERVE ACTIVITY AMPLITUDE(2013-04-12) White, DanielPurpose: MSNA has no agreed upon standard for analysis. For example, mean burst strength (MBS), total activity (TA) and total MSNA (TMSNA) rely on amplitude measurements assigned arbitrary units which are highly dependent on the method of normalization. We investigated the hypothesis that computer algorithms used for automatic normalization of MSNA amplitudes differ from those obtained with manual normalization leading to erroneous interpretations. Methods: MSNA from healthy human subjects (n=8, 2 female) was obtained by microneurography of the peroneal nerve while resting quietly in a 30* semi-recumbent position. Data was analyzed by 3 different normalization methods (Min-Max Auto (MM), Mean Auto (MA), and Rectified Manual (RM)). MSNA is quantified as burst frequency (BF), burst incidence (BI), MBS, TA, and TMSNA. Results: There were no differences in BF or BI between the three analysis methods. However, significant differences were detected between MM and RM in MBS, TA and TMSNA (p=0.002, p=0.009, and p=0.004). Rankings according to activity were not different between MM and RM but were different in MA compared to either MM or RM. Conclusions: There is an overwhelming need to standardize the analysis of MSNA. The current study points out that the variables BF and BI can be compared across studies. However, our data identify that the RM normalization is the only method to quantify MBS, TA and TMSNA for cross-study comparisons.Item Inhibitory Rib-Raising and Microneurographic Measurement of Sympathetic Nervous System Activity(2007-05-01) Kinzler, Damien W.; Michael Smith; Russell Gamber; Hollis KingThe clinical effectiveness of osteopathic manipulative therapy (OMT) techniques that are designed to address the autonomic nervous system (ANS) are untested to current research standards. As the concept of “autonomic imbalance” is frequently ascribed as the etiology of various pathologic conditions, it is paramount to undertake basic research into not only efficacy but also possible mechanistic actions and origins. Osteopathic physicians often utilize treatment regimens and techniques for which the given mechanism of action is simply attributed to “balancing the autonomics”. This intuitive concept may finally be at the threshold where enough basic science exists to justify clinical investigations. Osteopathic manual manipulative techniques have shown effectiveness in the treatment of various musculoskeletal conditions and have been shown to lower perceived pain; supporting the use of manual therapy as an effective treatment modality. A brief review yields the following within just the last four years: Eisenhart showed positive range-of-motion outcomes after ankle sprain in the emergency department. Biondi reviews the usefulness of cervical manipulation for tension headache and McReynolds demonstrated an equivalent decrease in acute neck with OMT versus intramuscular ketolac in an emergency department setting, although the dosing was not maximal. German researchers have shown effectiveness in chronic epicondylopathia humeri radialis and research has led to the demonstration of lowered post-operative pain in hip or knee arthroplasty. There has also been decreased post-operative pain medication reported in hysterectomy when compared with a control group. OMT has demonstrated a decrease in fibromyalgia symptoms when used with standard care over standard care alone. Low back pain, perhaps the most extensively studied diagnosis in which OMT has been evaluated, has reported numerous positive outcomes including lower levels of narcotic use and decreased pain in both double-blinded and meta-analysis studies, although there is still considerable debate within this area. There has also been favorable outcomes associated with the management of gain in Parkinson’s disease and preliminary work has shown the efficacy in treatment of carpal tunnel syndrome. Most of the aforementioned musculoskeletal conditions are not amenable to traditional therapies and have a high-cost burden on the economy. Traditional treatments generally have a “wait and see” approach combined with analgesics which may not cause harm, but hampers quality of life and income in the interim. The cost effectiveness of OMT is still in the preliminary stages, but there is evidence supporting a superior cost benefit ratio when compared to standard care and since many of these conditions have no other proven treatment modality available patients will often try anything over nothing. The evaluation of OMT addressing clear autonomic dysfunction is limited. This study closes a small part of that gap by examining the proposed physiologic mechanism of OMT and its’ interaction with the ANS. Small studies have documented changes, namely heart rate variability, in autonomic processes in healthy individuals while other, older studies have found benefit in clinical variables. With few exceptions however, most of these studies lacked a particular technique protocol. Operators were free to use whatever intervention that they chose and most of these studies were not performed under rigorous testing methods with a randomized design. The technique that was evaluated (inhibitory rib-raising) has a documented history from the origins of osteopathic medicine in the United States, and is currently taught to students in osteopathic medical schools as part of their medical education curriculum. Rib-raising is most often taught to enhance the mechanical motion of the ribs, but other paradigms utilize this technique to either enhance or inhibit sympathetic nervous system (SNS) activity. The evaluation of inhibitory rib-raising or its’ proposed mechanism of action has never been rigorously scrutinized to modern scientific standards. The current study was designed to address that gap with both direct and indirect measurement of SNS variable in healthy individuals with the hypothesis that there would be a time-dependent, graded reduction in measured sympathetic nervous system activity (MSNA) in healthy individuals undergoing cold-pressor stimulus.Item Mechanisms of Chemoreflex Control of Muscle Sympathetic Nerve Activity and Blood Pressure in Humans(2004-05-01) Hardisty, Janelle M.; Smith, Michael; Shi, Xiangrong; Clark, MichaelHardisty, Janelle M., Mechanisms of Chemoreflex Control of Muscle Sympathetic Nerve Activity and Blood Pressure in Humans. Doctor of Philosophy (Integrative Physiology), May 2004. The mechanisms linking obstructive sleep apnea (OSA) and cardiovascular disease are not fully understood; however, studies report patients with OSA exhibit chronic elevations in muscle sympathetic nerve activity (MSNA). This appears to be due to altered chemoreflex control of MSNA, mediated primarily by hypoxia. Yet, a correlation between degree of hypoxia and chemoreflex control of MSNA is unknown. Therefore, it was evaluated whether degree of hypoxia occurring during apnea determines the sympathoexcitatory and blood pressure responses, and whether these responses are augmented in OSA patients. Additionally, it was studied whether altered chemoreflex function in OSA patients is predictive of blood pressure response to apnea. In a clinical setting, the blood pressure response to voluntary apnea was determined to evaluate whether this could be used as a non-invasive measure of chemoreflex gain in OSA. Finally, the effect of hyperoxia on MSNA was studied to determine whether 15 min of hyperoxia, following intermittent hypoxic apnea, reverses the elevation of MSNA and altered chemoreflex control of MSNA. Consistent with the hypotheses, a relationship between MSNA responses, blood pressure response and level of hypoxia were determined. MSNA and peak systolic pressure responses were augmented in OSA subjects (p≤0.05 and p≤0.05, respectively), as well as, chemoreflex gain (p≤0.05). Clinically, peak systolic pressure responses to apnea were augmented in OSA patients (p˂0.001). Finally, basal MSNA and chemoreflex control of MSNA, following hyperoxia, was not different from baseline through 180 min of recovery (p=0.940 and p=0.278, respectively). These data support the hypotheses that chemoreflex gain is predicative of the blood pressure response; and furthermore, the MSNA and blood pressure responses to hypoxic apnea are augmented in OSA. Additionally, peak systolic pressure responses to voluntary apnea are augmented in OSA. Additionally, peak systolic pressure responses to voluntary apnea are augmented in OSA patients and could possibly be used as a marker of chemoreflex gain. Moreover, these data support the hypothesis that hyperoxia can reverse basal sympathoexcitation and augmented chemoreflex control of MSNA, associated with hypoxic apnea, supporting that elevations in MSNA are hypoxia mediated.