Apnoeic diving safety--experimental approaches to oxygen augmentation.

A study was undertaken to determine whether a volume of oxygen injected from a 100 ml syringe and inhaled during a 10 m ascent would be exhaled again fully or partially by two experienced male divers. Each performed one apnoeic dive with and another without O2 augmentation. Analyses of mouth gas showed that the injected O2 had disappeared when the divers reached the surface. Any movement of the injected O2 to the alveoli through an open glottis probably resulted from simple diffusion as well as from agitation and mixing of gases by simulated respiratory activity. High-frequency positive-pressure ventilation applied by several authors, whereby sufficient gas exchange is achieved by oscillating small tidal volumes at frequencies of up to 900 per minute, may substantiate this possibility. The injected O2 was found also to have disappeared from the alveolar gas, shown by a comparison of O2 fraction differences between augmented and non-augmented dives. Injection and inhalation of the additional O2 will raise the partial pressure of O2 in the alveoli and increase oxygen transfer across the alveolar membrane into the blood, with more molecules being taken up within seconds during the ascent time. O2 augmentation in larger volumes during apnoeic diving could lead to a burst lung and must be regarded with suspicion. There is evidence that O2 augmentation by means of a small syringe attached to a trained diver's snorkel will help prevent apnoeic blackout.

Apnoeic diving safety - experimental approaches to oxygen augmentation.

Oxygen augmentation during ascent for distressed apnoeic divers has recently been both advocated and criticized. Experiments involving 111 apnoeic divers have been conducted, shedding light on diving safety when oxygen augmentation is used at the onset of the apnoeic black-out, and are summarized in this report. It is maintained that black-out sets in gradually during ascent, taking the form of progressive tunnel vision, leaving scope for rational action by a distressed diver before complete loss of consciousness. By triggering a device (e.g. a 50 - 100 ml syringe) loaded with oxygen by means of pressure or otherwise at the onset of symptoms of hypoxic black-out during a 10 m dive, unconsciousness is believed to be delayed. This is because it takes a diver 12 seconds to rise to the surface from 10 m, while the lung-brain circulation time, inferred from textbook lung-ear circulation times for oxyhaemoglobin, is approximately 5.2 seconds. Since the oxygen is injected into the trachea by force and because of simulated involuntary ventilatory activity which dynamically mixes mouth and alveolar gas during apnoeic diving stress, the injected oxygen is believed to be quickly delivered at the alveoli. Such gas injection was shown to raise the amount of oxygen available to the diver by 25 - 50%. Intrathoracic pressure increases could ensure delivery of enough oxygen to the capillaries to delay unconsciousness. Recommendations for using the syringe at present apply only to 10 m dives and do not exclude use of other safety devices currently in use by divers or envisaged for their safety.

A field application of exercise testing in ischaemic heart disease.

When values before and after a walking programme were compared in 6 subjects who had had a myocardial infarction, it was found that there was a statistically significant improvement in VO2max, the respective means being 1,66 (+/- 0,57) and 2,07 (+/- 0,25) l/min. Blood pressures recorded during stress testing are shown; these served as guides in terminating exercise. Co-operation between the doctor, the physiotherapist and the physical educator was so productive that it is felt that greater interdisciplinary understanding in the rehabilitation field is highly desirable.

[The influence of sports injuries on sport participation and work]. / Die invloed van sportbeserings op sportdeelname en werk.

The incidence and complications of sport injuries in athletics, basketball, gymnastics, hockey, netball, cricket, tennis and soccer were analysed from questionnaire responses of 239 sport participants in Pretoria. Lower limb injuries were most common (73%). Torn tendomuscular organs represented 29,3% of the total number of injuries; sprains, strains and dislocations 35,9%; and fractures 20,5%. Medical treatment was sought by 62,8% of the patients. A total of 60,7% of the subjects was advised to suspend further participation in sport, but 30,6% failed to do so and more than half of these again sustained injuries. Those who were booked off from work totalled 18,0%, but a further 4,5% stayed away from work voluntarily.

Immunological tests for LH and FSH in urine.

The addition of 100 g/l NaCl and 200 mg/l nitrofurantoin to 24-h urine samples destined for determination of LH and FSH with haemagglutination tests, proved to be an adequate preservative in comparison to chilling.

Prescribing exercise--walking and jogging.

The family doctor is the ideal person to lead his patients back to a form of existence which is more dynamic and health-promoting than their customary way of life. Many basic fears of doctors are unfounded, for it is not difficult to acquire a knowledge of the ergological principles involved in natural movement and sport. Patients should be guided into 'forgetting' about their ailments, but at the same time remembering their limitations. The prescription of sensible forms of exercise, e.g. walking and jogging, is advocated. Some tried and sensible programmes are given.