Evaluation of the ORTHO-LBNP System
Condition: Orthostatic Hypotension; Ischemia; Hypoxia
MeSH terms: Hypotension, Orthostatic; Hypotension; Ischemia; Hypoxia
Study type: Interventional

Summary: 
      The pilot study aims to evaluate a prototype system that enables military pilots to train
      under conditions of orthostatic hypotension and ischemic hypoxia. Both of these phenomena are
      experienced by aircraft crews of mainly highly maneuverable aircraft, and their syndromes
      include loss of color vision, loss of peripheral vision, blackout and finally G-induced loss
      of consciousness (G-LOC). A motorized tilt table to generate orthostatic (ORTHO) stress
      combined with an automatically controlled lower body negative pressure (LBNP) chamber to
      extort pooling of blood in the lower extremities has been developed in order to obtain new
      knowledge on counteracting the above-mentioned effects and minimizing the risk of their
      occurrence. This will help optimize the selection procedures of candidates with the best
      physiological predispositions to work as military pilots. The system is equipped with modules
      for monitoring biomedical parameters of a subject, including cerebral oxygenation, which
      ensures their safety and provides a source of data for performing advanced analyses. The
      ORTHO-LBNP system has been subjected to comprehensive laboratory tests and after a successful
      testing is ready for a pilot study involving pilots and/or cadets of the Polish Air Force
      Academy (PAFA). It is anticipated that new indicators will be proposed to enable an objective
      assessment of the predispositions to pursue a military pilot career. The prototype system can
      be easily adaptable to the needs of clinical and sports medicine as well as rehabilitation.
    

Detailed description: 
      The pilot study consists of two research scenarios, in which two different sequences of the
      interventions taking the form of the pre-programmed tilt and LBNP profiles are to be
      investigated.

        1. Scenario I is designed to initially verify the potential impact of the prototype system
           on the human body. For this purpose, only basic tilt and LBNP stimuli of relatively
           slowly increasing intensities will be used, and the group of subjects will include only
           subjects with flight experience. Up to 20 PAFA cadets shortly before graduation,
           including women and men, will be involved in the pilot study (experimental arm 1). The
           subjects will be healthy, aged between 20 and 30 years old. Scenario I will take almost
           24 min.

        2. Scenario II is to compare subjects with and without flight experience using rapid tilt
           and LBNP stimuli as well as a push-pull stimulus. Up to 30 subjects including up to 15
           pilots, i.e., flight school adepts shortly after graduation and/or PAFA cadets shortly
           before graduation, and up to 15 students of the Aviation High School in Dęblin, Poland,
           including women and men will be involved in the study (experimental arm 2). The subjects
           will be healthy, aged between 18 and 30 years old. The students of the Aviation High
           School will participate in the study as a reference group, without flight experience.
           Scenario II will take 16 min.

      The pilot study will be carried out in an isolated room in the presence of a physician
      (physiologist), a paramedic and an ORTHO-LBNP system operator. The paramedic will prepare the
      subject for the study by placing on his/her body electrodes and measuring sensors that will
      be removed after completion of the study. The subject will be asked to close his/her eyes
      during the tests and to place his/her hands on the rest. In order to cause the least
      disturbance, no conversation will be held with the subject. Only if disturbing symptoms will
      occur, will the subject immediately report this to the personnel. The physician will
      systematically be observing the subject's cardiogram, his/her HR, continuous non-invasive
      arterial pressure (CNAP) wave, and systolic and diastolic blood pressure (SBP and DBP,
      respectively) in comparison with the changing tilt of the table and negative pressure in the
      chamber. Any time, at the request of the subject or on the instruction of the physician, the
      operator will interrupt the tests. The tilt table then will return to the Trendelenburg
      position if interruption occur during HUT and/or LBNP stimuli, or horizontal position if
      interruption occur during HDT stimulus. At the same time atmospheric pressure will be resumed
      in the chamber.
    

Intervention name(s): Head up tilt (HUT); Lower body negative pressure (LBNP); Head down tilt (HDT); Tilt table; LBNP chamber
Intervention type(s): Other; Other; Other; Device; Device
Intervention description(s): Model of -Gz: HUT up to 75 degrees (maximum); Model of -Gz: LBNP down to -100 mmHg (maximum); Model of +Gz: HDT down to -30 degrees (maximum); Range of tilt angles: -45° to +80°, rate of tilt changes: up to 45°/s; Range of generated underpressure: 0 to -100 mmHg, rate of underpressure changes: up to 20 mmHg/s
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Gz accelerations; Head up tilt (HUT) test; Lower body negative pressure (LBNP) method; Physiological parameters; Variable gravitational stimuli