2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
blood flow during baroreflex stimulation.
METHODS
Eight healthy male athletes and eight non-athletes were tested (wearing only shorts) at
an ambient temperature of 28ºC±0.2ºC and relative humidity of 40%. Subject were
tested in a supine position with the lower body below iliac crest placed in a LBNP
box. A rubber seal and band were attached to the inside of the box to maintain airtight
condition between the abdomen and box. After all variables had stabilized (60 min),
the LBNP was applied randomly for 5 min either at 150 or 300 mmH2O. We used a
commercially available reversed air pump to draw air from the box, and adjusted the
pressure by varying the diameter of air vent valves (Figure 1).
Forearm blood flow was measured using two methods. (A) Venous occlusion
plethysmography using a mercury-in-Silastic tube strain gauge (10 g tension) around
the mid point of the left forearm. (B) Laser Doppler flowmetry (ALF-2100, Advance,
Tokyo). To measure forearm blood flow, a 5 cm cuff was applied to the wrist and
inflated to 250 mmHg. Blood flow to fingers was blocked, and after checking that the
needle of the recorder was about to stop swinging, 40-50 mmHg was applied for 15
seconds to a regular size cuff placed around the upper arm to block venous return. The
formula below gives a calculation of the volume of blood flow based on the change of
volume per unit time. Pressure for the upper arm was dropped to zero afterwards to
remove vein congestion.
Forearm blood flow =2 x 100 x Tn x V/G x (α/ρ)
where G: the circumference of a forearm (mm)
Tn: tangent of G increase due to the increase in the volume of venous blood flow
V: chart speed (mm/ min)
(α/ρ): change on the chart (mm) at the time of 1 mm change in strain gauge .
Finger blood flow was measured using a mercury-in-Silastic strain gauge (10 g
tension) around the center of an index-finger (2) . Heart rate was measured using an
electrocardiogram (AT-600 G, Nihon Kohden, Tokyo). Blood pressure during
exercise was recorded from the right upper arm (at the same level as the heart). At an
application of each LBNP intensity, systolic and diastolic blood pressures were
measured automatically (Omron Healthcare Co., Ltd.: HEM-757 Fuzzy) for 3.5 min
during the latter period of the application.
RESULTS
Figure 2 illustrates the time course of changes in finger and forearm blood flows,
starting from rest, during applications of LBNP, and during recovery. For the both the
athletes and the non-athletes, finger blood flow and forearm blood flow decreased
after the onset of LBNP application, but rapidly recovered to almost the same levels
44
To Vacuum
Pump
Manometer
150,300mmH 2 O
Fig.1 Experimental set up
Blood Pressure
Heart Rate
Finger Blood Flow
T es
Forearm Blood Flow