Electrocardiographic changes during exercise in asymptomatic men: 3-year follow-up.

Electrocardiographic (ECG) changes during maximal bicycle exercise and risk factors for coronary heart disease (CHD) were studied in 510 male civic employees who were followed for 3 years. Clinical CHD developed in 15 (24.6 percent) of the 61 men with an ischemic exercise ECG on the initial examination and in 11 (2.4 percent) of the 449 subjects with a normal initial exercise ECG. A normal maximal exercise ECG is no guarantee that severe CHD does not exist and that a subject will not soon sustain major myocardial damage; and an ischemic exercise ECG does not necessarily indicate underlying CHD. In the former group angina was the most frequent clinical CHD episode; in the latter group, infarction. Among those with an abnormal initial exercise ECG, CHD was most likely to develop in association with a poor exercise capacity. Subjects with subsequent clinical CHD and those with abnormal ECGs after 3 years tended to have a higher frequency of risk factors; subjects whose abnormal ECGs reverted to normal after 3 years tended to have a lower frequency of risk factors.     

Lung volumes during +Gz acceleration and the effects of positive pressure breathing and chest counter-pressure

The advent of agile fast jet aircraft has initiated the research and development of enhanced systems to protect man against high +Gz acceleration. As part of such an enhanced system, the breathing of a pressurised gas mixture under +Gz is likely to become routine during the next decade in many of the world's air forces. This procedure, termed positive pressure breathing for G protection (PBG), typically uses breathing pressures of up to 65 mmHg in order to elevate intra-thoracic arterial blood pressure. In this way the fall in head level arterial blood pressure under +Gz acceleration is minimised. Consciousness is therefore preserved, with the aim of reducing the incidence of G Induced Loss of Consciousness (G-LOC). The aim of the research reported here is to assess the viability of the experimental technique and to gather preliminary data on the changes in lung volume subdivisions under PBG (specifically VC, ERV and the VC/ERV ratio).