title: Additive Effects of Sinusoidal Lower Body Negative Pressure on Cardiovascular Responses.
abstract: BACKGROUND
  Sinusoidal lower body negative pressure (SLBNP) has been used to investigate the cardiovascular response to slow periodic changes in blood shifts, but measurements of slow fluctuations take a long time if measured for each period of SLBNP separately. Our study aimed to investigate whether the cardiovascular responses to superimposed SLBNP (S-SLBNP), which is expected to reduce the measurement time, are different from responses measured individually.
  
  
  METHODS
  S-SLBNP was configured by superimposing two conventional SLBNPs (C-SLBNP) at 180-s and 30-s periods in the pressure range from 0 to -25 mmHg. As the S-SLBNP has double the static load of C-SLBNP, we also used offset SLBNP (O-SLBNP), which has the same static load level as S-SLBNP. Heart rate (HR), thoracic impedance (Z0), and mean arterial pressure (MAP) were measured from 11 male subjects. The transfer functions of gains from MAP to HR (Gain-HR/MAP) and from Z0 to HR (Gain-HR/Z0) were calculated as indexes of arterial baroreflex and cardiopulmonary baroreflex regulation of HR, respectively.
  
  
  RESULTS
  The Gain-HR/MAP in the 180-s period (2.11 ± 0.17 bpm/mmHg; mean ± SEM) was larger than that of the 30-s period (1.04 ± 0.09 bpm/mmHg); however, there was no significant difference between the SLBNP conditions. The Gain-HR/Z0 in C-SLBNP (9.37 ± 1.47 bpm/ohm) was smaller than that of the other conditions [18.46 ± 2.45 bpm/ohm (O-SLBNP); 16.09 ± 2.29 bpm/ohm (S-SLBNP)].
  
  
  CONCLUSIONS
  Using S-SLBNP could reduce the measurement time needed to examine the arterial baroreflex. However, the cardiopulmonary baroreflex was modified by the static load of SLBNP.Ishibashi K, Oyama F, Yoshida H, Iwanaga K. Additive effects of sinusoidal lower body negative pressure on cardiovascular responses. Aerosp Med Hum Perform. 2017; 88(2):137-141.
authors.forename: Keita
authors.initials: K
authors.lastname: Ishibashi
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Oyama
authors.forename: Hisao
authors.initials: H
authors.lastname: Yoshida
authors.forename: Koichi
authors.initials: K
authors.lastname: Iwanaga
mesh_terms: D062186:Arterial Pressure; D017704:Baroreflex; D001794:Blood Pressure; D002307:Cardiography, Impedance; D064368:Healthy Volunteers; D006339:Heart Rate; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D013997:Time Factors; D055815:Young Adult