Sympathoexcitation is attenuated during low level lower body negative pressure in subjects who develop pre-syncope

Stephen L. Wasmund, Michael L. Smith, Theodore S. Takata, Jose A. Joglar, Jian Ming Li, Robert C. Kowal, Richard L. Page, Mohamed H. Hamdan

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The purpose of this study was to compare the hemodynamic and sympathetic nerve activity (SNA) responses to graded lower body negative pressure (LBNP) in healthy subjects with either a positive (n = 24, SNA in 8) or a negative (n = 18, SNA in 6) LBNP response. A positive LBNP response was defined as an abrupt drop in systolic blood pressure associated with a decrease in heart rate and/or a decrease in SNA. All positive responses were accompanied by symptoms common to presyncope, defined as lightheadedness, diaphoresis, tunnel vision and/or nausea. If subjects tolerated 30 minutes of LBNP, this was considered a negative response. Comparisons were made between baseline, -10 mmHg (low-level LBNP) and -60 mmHg (high-level LBNP). Baseline SNA and arterial barore flex sensitivity were not different between the 2 groups. However, subjects with pre-syncope had a significantly attenuated SNA response during low-level LBNP (p < 0.05) compared to subjects who did not experience pre-syncope. The hemodynamic data during high-level LBNP were similar until the occurrence of presyncope. Pre-syncope was preceded by a significant decrease in heart rate and SNA. Our findings suggest that subjects with LBNP induced pre-syncope might have an impairment in the cardiopulmonary baroreflex gain function in the setting of a preserved arterial baroreflex gain.

Original languageEnglish (US)
Pages (from-to)208-213
Number of pages6
JournalClinical Autonomic Research
Issue number3
StatePublished - Jun 2003
Externally publishedYes

Bibliographical note

Funding Information:
■ Acknowledgments This work has been supported by an NIH grant to Mohamed Hamdan, MD (R01 HL-65490–01).


  • Autonomic nervous system
  • Baroreceptors
  • Sympathetic nerve activity
  • Syncope


Dive into the research topics of 'Sympathoexcitation is attenuated during low level lower body negative pressure in subjects who develop pre-syncope'. Together they form a unique fingerprint.

Cite this