The Changes of the Left Ventricular Contractility and the Cardiac Vector of the Pilot by the Flight Time

To study on the left ventricular contractility and the cardiac vector of fighter pilots, 56 pilots and 15 normal cadets were selected and they were divided into six groups by flight time (hours). To evaluate the left ventricu-lar contractility of subjects, R amplitude of chest V1 , V5 , V6 lead were recorded by ECG, and R-Z interval were recorded by ICG (impedance cardiography). And, to evaluate the cardiac vector of subjects, mean QRS vec-tor of I, II, V2 , V6 lead were recored by ECG. Results of this study are following, 1) Systolic and diastolic blood pressure were decreased against flight time. 2) Sv1 +Rv5 was decreased against flight time; Sv1 +Rv5 was 27.8 mm in 50 hr Group that is the longest among the group, and 23.7 mm in 2,000 hr Group that is the shortest among the groups. V6 /V5 was no significant difference among the groups. 3) R-Z interval was decreased against flight time; R-Z interval was 166.8 X10(-3) sec in 50 hr Group that is the longest among the group, and 154.4 X10(-3) sec in 2,000 hr Group that is the shortest among the groups. 4) In frontal plan, the range of QRS vector axis was +57.3 degrees ~ +78.2 degrees that was deviated to left of body center according to the flight time. In horizon-tal plan, the range of QRS vector axis was -29.6 degrees ~ +47.2 degrees that was deviated to back of body center according to the flight time. In both plan, the amplitude of QRS vector was tend to decreasing against the flight time. Results of this study indicate that the cardiac function of fighter pilots was doubted to degenerate or weaken. Conclusionally, fighter pilots have to increase their cardioventricular fitness by the aerobic training and other methods.

The Cardiac Output and the Cardiac Muscle Contractility During Postural Gradient Changes by Tilt Table in Man

The purpose of this study is to investigate changes of the cardiac output and the cardiac muscle contractility during postural gradient changes in man. Subjects consisted of 15 healthy males that they were aged 23-24 years. The Cardiac output and the contractility were calculated using the impedance cardiogram that were recorded by new apparatus developed in Yonsei Medical Center. The impedance cardiogram was recorded in different 7 gradients which were 0degrees, +/-2degrees, +/- 45degrees and +/-90degrees according to the head position, but it was continuously recorded at each gradient. The each postural gradient was changed after supine resting, 15-20 min, and continued in 5 min. Results of this study were following, 1. The cardiac output was decreased at head up posture (+2degrees, +45degrees and +90degrees) because of decreasing stroke volume. But the cardiac output was increased at head down posture (-2degrees, -45degrees and -90degrees) by increasing stroke volume. 2. The cardiac output was significantly changed at +/-45degrees and +/-90degrees after immediately gradient changes, but it was no significant difference at 0 and +/-2degrees postures from that of supine resting state. 3. At +/-45degrees and +/-90degrees, the cardiac muscle contractility was increased, and in head up posture, amounts of change were more larger than in head down posture.

Changes of cardiac output during treadmill exercise by impedance cardiography

Nine athletes and ten nonathletes were selected randomly to study the changes of cardiac function during exercise by impedance cardiography. The speed of the treadmill was maintained at 3.4 mph, and its grade was increased by 1% (Balke protocol). The exercise was continued until the target heart rate (THR), 85% of maximum oxygen uptake (VO2max). The measured parameters for pre- and post-exercise were stroke volume (SV), heart rate (HR), and cardiac output (CO). Average stroke volume of athletes at pre-exercise, 71.1 ml, was higher than that of nonathletes, 64.6 ml, and stroke volume of the former at post-exercise, 97.0 ml, was also higher than that of the latter, 85.2 ml. Therefore, despite the lower heart rate, cardiac outputs of athletes at pre- and post-exercise, 4.98 and 16.3 L/min, were higher than those of nonathletes, 4.87 and 14.2 L/min. For the second phase of the study, cardiac outputs of three subjects were measured during the continuous treadmill exercise with newly developed electrodes and shoes for minimizing motion artifact. Though there were several studies measuring cardiac output during continuous bicycle exercise, this is thought to be the first study in the world measuring cardiac output during continuous treadmill exercise without aid of ensemble averaging.