Fig. 2. Beat-to-beat arterial pressure and heart rate during a stand test after a short flight (top) and a tilt test after a long flight (bottom) in one subject. In the top panel the horizontal arrow indicates that the entire 10 minutes of upright posture was maintained without presyncopal symptoms or hemodynamic instability. Note that after an initial rise and recovery, heart rate varied around 50 to 60 bpm during upright posture. In contrast, after the long flight (bottom), the interrupted horizontal line indicates that presyncopal symptoms occurred, associated with a sudden drop in both pressure and heart rate. (No blood work was available on this subject.)
