Manipulation of central blood volume and implications for respiratory control function.
The respiratory operating point (ventilatory or arterial PCO2 response) is determined by the intersection point between the controller and plant subsystem elements within the respiratory control system. However, to what extent changes in central blood volume (CBV) influence these two elements and the corresponding implications for the respiratory operating point remain unclear. To examine this, 17 apparently healthy male participants were exposed to water immersion (WI) or lower body negative pressure (LBNP) challenges to manipulate CBV and determine the corresponding changes. The respiratory controller was characterized by determining the linear relationship between end-tidal PCO2 (PetCO2 ) and minute ventilation (Ve) [Ve = S × (PetCO2 - B)], whereas the plant was determined by the hyperbolic relationship between Ve and PetCO2 (PetCO2 = A/Ve + C). Changes in Ve at the operating point were not observed under either WI or LBNP conditions despite altered PetCO2 (P < 0.01), indicating a moving respiratory operating point. An increase (WI) and a decrease (LBNP) in CBV were shown to reset the controller element (PetCO2 intercept B) rightward and leftward, respectively (P < 0.05), without any change in S, whereas the plant curve remained unaltered at the operating point. Collectively, these findings indicate that modification of the controller element rather than the plant element is the major factor that contributes toward an alteration of the respiratory operating point during CBV shifts.
Graduate School of Health Sciences, Morinomiya University of Medical Sciences, Osaka City, Osaka, Japan; Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center Research Institute, Suita City, Osaka, Japan; miyamoto@morinomiya-u.ac.jp.
Tadayoshi
T
Miyamoto
Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Wales, United Kingdom; and.
Damian Miles
DM
Bailey
Graduate School of Health Sciences, Morinomiya University of Medical Sciences, Osaka City, Osaka, Japan;
Hidehiro
H
Nakahara
Graduate School of Health Sciences, Morinomiya University of Medical Sciences, Osaka City, Osaka, Japan;
Shinya
S
Ueda
Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center Research Institute, Suita City, Osaka, Japan;
Masashi
M
Inagaki
Department of Biomedical Engineering, Toyo University, Kawagoe City, Saitama, Japan.
Shigehiko
S
Ogoh
D000293:Adolescent; D000328:Adult; D001810:Blood Volume / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007101:Immersion / Q000503:physiopathology; D008150:Lower Body Negative Pressure; D008297:Male; D012123:Pulmonary Ventilation / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume / Q000502:physiology; D055815:Young Adult
D002245:Carbon Dioxide
central blood volume; head-out water immersion; lower body negative pressure; respiratory control; system analysis