PhD defense by Lonnie Petersen

Lonnie Petersen

On Friday April 15th, Lonnie Petersen defended her PhD thesis on the effects of gravitational stress on the circulation.

The aim of this thesis was to investigate gravitational blood volume distribution and effects on regional pressure, especially intracranial pressure. Graded head-up and down tilt was used to manipulate the magnitude and direction of the hydrostatic gradients (study I and study III). However, the only way to abolish hydrostatic gradients altogether is by weightlessness. Therefore weightlessness is a unique research-tool because it provides a control-situation for the effects of gravity and this was used by study II and study IV.

The thesis was based on the following publications:

  1. Petersen LG, Carlsen JF, Nielsen MB, Damgaard M, Secher NH. The hydrostatic pressure indifference point underestimates or- thostatic redistribution of blood in humans. J Appl Physiol. 116: 730–735, 2014.
  2. Petersen LG, Damgaard M, Petersen JCG, Norsk P. Mechanisms of increase in cardiac output during acute weightlessness in hu- mans. J Appl Physiol. 111: 407–411, 2011.
  3. Petersen LG, Petersen JCG, Andresen M, Secher NH, Juhler M. Postural influence on intracranial and cerebral perfusion pres- sure in ambulatory neurosurgical patients. Am J Physiol Regul Integr Comp Physiol. 310: r100–104, 2016.
  4. Lawley JS, Petersen LG, Howden EJ, Sarma S, Cornwell WK, Zhang R, Whitworth LA, Williams M, Levine BD. Effect of grav- ity on the intracranial pressure: Implications for visual impairment in space. Unpublished, manuscript in preparation.

Supervisor and reviewers

The primary thesis supervisor was:

Professor Niels H. Secher
Department of Anaesthesia,
The Copenhagen Muscle Research Centre,
Rigshospitalet, University of Copenhagen, DK

The thesis reviewers were:

  • (Chairperson) Professor Christian Aalkjær
    Department of Biomedical Sciences,
    University of Copenhagen, DK
  • Professor Tobias Wang
    Department of Bioscience,
    Aarhus University, DK
  • Professor Richard Hughson
    Department of Kinesiology,
    Faculty of Applied Health Sciences,
    University of Waterloo, Canada