A pressure regulator for controlling inflatable cuff pressure of tracheal tube was invented, which allowed to superpose the change of patient's ventilatory pressure upon controllable but stable basic cuff pressure according to the change of ambient pressure. This mechanism can be maintained even under rapid change of environmental pressure as OHP. This device comprises the first air-tight chamber with an input port from medical gas source, the second chamber connected to cuff, the third chamber leads to the inside of tracheal tube and the fourth chamber with an orifice open to the air for venting. A diaphragm between the second and the third chambers is connected to a basic cuff pressure regulator so that the pressure in the second chamber can be set at a desired level and also be controlled in response to the pressure change in the third chamber equal to the ventilatory pressure.
Thus, cuff pressure can be maintained as the sum of preset basic pressure and ventilating pressure, and other influences can be eliminated. When medical gas supply pressure falls lower than a certain level, gas discharge from the second chamber to the air through the fourth chamber is automatically blocked by shut-off valve coupled to a small spring and the cuff pressure can be maintained.

View full abstract

It is well known that deep and slow breathing pattern is commonly observed at increased pressure environment. But how this breathing pattern is made is not clear. We compared duration of inspiration （T_I）, expiration （T_E） and depth of breathing at rest for six human subjects with inductance plethysmograph and hotwire flowmeter at 1ATA and 3ATA. Although no difference was seen in amount of the ventilation between 1ATA and 3ATA, increased chest wall movement was observed at 3ATA on the output from inductance plethysmograph. This phenomena was supposed to be due to compensative mechanism of breathing against increased density of breathing gas. When ventilation was enhanced by CO₂ rebreathing method, deep breath due to prolongation of T_I times unchanged V_T/T_I was observed at 3ATA. These data demonstrate that prolongation of both T_I and T_E and T_I×V_T/T_I create slow and deep breathing pattern at 3ATA. This phenomena was supposed to be regulated by neural control of breathing.

View full abstract

Perfluorochemicals （Fluosol DA-20%：FDA20%） was originally developed as a substitute for blood and has specific oxygen carrying capacity which is increased proportional to the rise of PO₂. In this study, FDA20% was used for the treatment of ischemic brain after acute cerebrovascular disease, and pharmacological effect was studied between three groups; group A used FDA20% alone, group B introduced OHP and group C used both FDA20% and OHP. The results were evaluated through regional cerebral blood flow, brain metabolism and Furier analysis of EEG.
FDA20% increased CBF for ischemic brain. The change of EEG was most significant in those received 500ml of FDA20% infusion under OHP. These facts suggested combined use of FDA20% and OHP could be one of the most effective therapies for such ischemic brain lesion.

View full abstract

Basic principles for nursing OHP patients were established, which conisted of three major categories; nursing safety, comfortable treatment and effective support for patients. Standing on these principles, nursing guidelines for OHP, a orientation pamphlet for patients and a communicating chart between nursing station in the ward and hyperbaric unit were designed originally. These nursing guidelines were examined clinically for 37 patients from November 1984 to October 1985.
Neurological disorders indicated for OHP were; motor （20 patients）, consciousness （10）, speech （5） disturbances and disorientation （9）. Due to the effect of new guidelines, 29 patients received OHP without any complication. Among 8 troubled patients, 4 showed claustrophobia or severe otalgia. The other 4 failed to receive beneficial effect of OHP because clinical conditions were getting worse rapidly. These nursing guidelines and orientation pamphlet were testified as useful supplemental materials for OHP.

View full abstract

A questionary survey was carried out for 2,135 Coastal Fisheries Cooperative Associations （CFCA） to obtain updated informations on diving fishermen in Japan. This survey covered their total number, diving purposes and methods. By the end of August of 1986, 2,125 answers were delivered and following results were revealed.
1. There were approximately 16,600 diving fishermen （13,000 male and 3,600 female） in Japan, who were entirely or mainly engaged in diving fishery.
2. Peak of age distribution were between 30s and 50s in male, 40s and 60s in female.
3. Although diving method varied according to the difference of locality, breathhold diving occupied about 64%.
4. To protect body and prevent heat loss during diving, about 93% of divers used wet suits routinely.
5. Common problems CFCA concerned seriously were those relevant to sea resources, poachers and successors.

View full abstract

Hood type oxygen mask was used during HBO in order to realize high oxygen concentration for patient. Transcutaneous PO₂ （TcPO₂） was measured and compared in both hood and face type masks.
Average TcPO₂ was 100mmHg higher in hood type oxygen mask than in face type mask during 2ATA of HBO. Pulse rate decreased obviously in both groups but there was no significant difference between them.

View full abstract

This study was performed to measure actual oxygen tensions in normal and tumor tissues prior to study whether gastric cancer is radiosensitive under HBO condition.
Oxygen tensions in normal and tumor tissues during exposure to normobaric （O₂ 6l/min） and HBO （3 ATA） conditions were measured by poralographic technique in nude mice being transplanted human gastric cancer. In normal tissue which had tumor less than 2cm in diameter, PO₂ was almost equal to non-tarnsplanted mice, but those carried tumor more than 3cm showed lower PO₂. Under normobaric condition, PO₂ in cancer tissues were distictively lower than normal tissue, however, under HBO condition, it was 11 times higher than room air breathing and 13 times higher than normal tissue. There was no differences of PO₂ according to the histological characters of cancer tissue. From these results, it is preferable to perform radiation therapy for gastric cancer under HBO condition.

View full abstract