Skin antisepsis during steady-state hyperbaric exposure and subsequent decompression.

A custom-made container for the transfer of bacteriological sampling pads was used in a trial to test the feasibility of human skin disinfection during saturation or steady-state diving and subsequent decompression. Analysis of the results of colony counting and typing from 6 days of pre- and postcleansing samples taken during a recent saturation dive indicates that the skin of hyperbaric chamber occupants can be effectively sterilized in the event of a need to prepare for anesthetic or surgical procedures while still under pressure. A separate survey was also made to establish any pattern of change in bacterial flora of the chamber interior during the trial. Results of this survey are briefly discussed.

Delayed cerebral edema complicating cerebral arterial gas embolism: case histories.

A disquieting and rarely described feature of the treatment of arterial gas embolism (AGE) is the high incidence of relapse following good to excellent initial responses to recompression therapy. This paper includes a discussion of the issues involved in the etiology and clinical approach to the specific problem of relapse and relates experience from selected clinical cases to a modified therapeutic approach that has been introduced into Royal Navy diving and submarine medicine practice. It illustrates how and why current treatment procedures have been expressly designed to minimize the incidence of relapse and to modify favorably the pathophysiological responses (particularly vasogenic cerebral edema) associated with cerebral AGE.

Function of the Oxford Ventilator at high pressure.

The Penlon Oxford Ventilator functioned well to 6 atmospheres absolute in an air environment and to 31 atmospheres absolute in an oxyhelium environment, as assessed remotely utilising a lung ventilator performance analyser. It features easily comprehensible controls and functions, and its use in prolonged ventilatory support could be taught to non-anaesthetists with relative ease. In addition to its relative simplicity, it is reliable, readily available, and requires only fitting with a male Schrader valve for use at high pressures. The ventilator is recommended for ventilatory support under extreme hyperbaric conditions.

A pilot study of skin disinfection in the hyperbaric environment.

An opportunity was taken to carry out a pilot on human skin disinfection during a recent long-term saturation dive at extremely high pressure. Despite a number of difficulties, results were sufficiently encouraging to suggest that, given ideal conditions, sterilization of the skin in preparation for surgical or anesthetic procedures, or both, in a hyperbaric environment is possible.

Urinary excretion of water and electrolytes during open-sea saturation diving to 850 fsw.

The dive was carried out in the open sea to a depth of 850 fsw (26.7 ATA) for 6 days (DD 1--6) in the saturated mode, with personnel transfer capsule (PTC) excursions between 0 and 150 fsw and diver excursions between 0 and 50 fsw from the saturation base. Each diver had two excursion dives on alternate days. Although each PTC excursion lasted approximately 7 h, the actual time spent in the water averaged 10.5 min per diver. For 12 divers, daily excretion of water, electrolytes, aldosterone, and antidiuretic hormone (ADH) was studied, along with plasma composition (including prolactin), before, during, and after hyperbaric exposure. A significant increase in urine flow was observed on DD2--4 (1604 ml/day predive vs. 2300 ml/day on DD 4; P less than 0.05), after which the degree of diuresis decreased to about 1800 ml/day. Urine osmolality changed inversely with urine flow, with the lowest value of 532 mOsm/kg on DD 4. During the postdive period, both urine flow and urine osmolality returned to the predive level. The endogenous creatinine clearance was maintained at about 200 liters/day throughout the dive. The fractional excretion of Na+ remained unchanged while that of K+ increased significantly during hyperbaric exposure, thus decreasing the urinary Na+/K+ ratio. The fractional excretion of total osmotic substances showed a small hyperbaric exposure. Body weight decreased progressively during the initial 4 days of pressure exposure, equalling 2.6 kg on DD 4. These findings suggest that the observed diuresis may be accompanied by a net loss of body water. Neither the plasma prolactin level nor urinary excretion of aldosterone and ADHshowed any consistent change throughout the dive. It thus appears that, although there is a small osmotic component, the observed diuresis is primarily due to the ADH-independent inhibition of fre water reabsorption from the collecting duct by means of a mechanism yet to be identified.

Venous gas bubbles: production by transient, deep isobaric counterdiffusion of helium against nitrogen.

When awake goats were subjected to isobaric gas switching from saturation (17 hours) on 4.7 atmospheres of nitrogen (0.3 atmosphere of oxygen) to 4.7 atmospheres of helium (0.3 atmosphere of oxygen), bubbles detected by 5-megahertz Doppler ultrasound in the posterior vena cava 20 to 60 minutes after the switch continued for 4 hours. Similar experiments carried out at 6.7 atmospheres of inert gas and 0.3 atmosphere of oxygen produced more bubbles for as long as 12 hours after the gas switch. This is believed to be the first objective demonstration of the phenomenon of deep isobaric supersaturation under transient operational diving conditions at relatively shallow diving depths. Detection of bubbles by Doppler ultrasound confirms the potential importance of the phenomenon to shallow saturation diving and holds promise for better quantitification of its effects as well as those of its counterpart, isobaric undersaturation, which can confer a decompression advantage.

Hematologic changes in man during decompression: relations to overt decompression sickness and bubble scores.

In order to determine whether asymtomatic gas phase separation causes hematologic abnormalities, studies were carried out following two dive series, one to 210 feet of sea water (FSW) for 50 min and the other to 132 FSW for 30 min. Studies included white and red cell count, red cell indices, platelet count, ESR, fibrinogen, fibrin split products, prothrombin time, partial thromboplastin time, coagulation factors II, V, VII, VIII, and X, clot retraction, platelet aggregation and adhesion, euglobulin lysis time, and platelet factor III. Changes were seen in platelet and white cell count, prothrombin time and partial thrombo-plastin time. White cell count was the only variable which correlated with total bubble score. The results are presented and implications of the findings discussed.