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Biomedical subjects

P G Linaweaver

Publications and source records attributed to P G Linaweaver.

13 recordsLinked to original sources
PubMed1979

Immersion vs pressure-breathing and diaphragmatic function in the upright position.

In seven anesthetized dogs, immersion in the upright position to mid-neck level (IM) was compared to pressure breathing (PB) under dry conditions during constant-stimulus diaphragmatic contraction (EPS). The comparison was in terms of EPS-induced changes in alveolar pressure under static condition (Pmus); EPS-induced tidal volume (VT); and the VT/Pmus ratio (C'). It was found that at iso-lung volume (V): (a) Pmus was greater in IM than in PB, the difference increased at higher V; (b) VT was greater in IM than in PB, but the VT difference (deltaVT) did not parallel that in Pmus; VT was maximum at a V equal to approximately 90% of FRC in air (FRCd) and decreased below and above this volume; (c) during both IM and PB, the VT-V relationship reflected a biphasic relationship of C' to V and appeared to be inherent to the upright position.

Animals↗
PubMed1978

Diving experience and emotional factors related to the psychomotor effects of nitrogen narcosis.

Simple and complex psychomotor performance were tested among 21 Navy divers under normal conditions and during nitrogen narcosis in simulated dives to 170 ft of sea water. Complex psychomotor performance was impaired significantly during narcosis, while simple psychomotor performance remained essentially normal. Differences between baseline scores for complex psychomotor performance (pre- and post-dive combined) and scores obtained from the two combined testing sessions administered during narcosis were correlated with official Navy records of diving experience and self-reported moods. None of the diving experience measures was associated significantly with these difference scores. The moods of Fatigue and Happiness were, however, correlated significantly with impairment. These results indicate that, although previous experience with nitrogen narcosis and diving tasks do not mediate the performance effects of nitrogen narcosis, the complex psychomotor effects nitrogen narcosis are related to emotional traits.

Adult↗
PubMed1977

Diaphragmatic function during immersion.

Diaphragmatic function during immersion to midneck level was studied in upright mongrel dogs, using constant electrophrenic stimulation. Effectiveness of diaphragmatic contraction was analyzed in terms of inspired volume (VT) (with airways open), and change in intrathoracic pressure (Pmus) (with the respiratory system occluded). Hydrostatic compression of the immersed body decreased functional residual capacity (FRC) to 55% base-line value (FRCO), resulting in a 2.8-fold increase in Pmus. In spite of this Pmus increase, VT often decreased during immersion, averaging only 83% VTO (base-line value in air). Hence, immersion was associated with a marked stiffening of the respiratory system. The Pmus increase during immersion persisted after restoration of FRC to FRCO, and was related to diaphragmatic length being greater in water than in air under condition of iso-lung volume. In all, there were three factors affecting diaphragmatic function during immersion: FRC reduction, change in thoracic configuration, and stiffening of the respiratory system.

Animals↗
PubMed1976

Occupational differences between conventional and saturation divers.

Diving experiences of 53 Divers First Class attending the U.S. Navy Saturation Diver Training Program were compared to 155 Divers First Class performing routine operational dives. The two groups were matched for years of diving experience, total number of dives, and total number of SCUBA dives. The Diving Experience Questionnaire (DEQ), which consisted of 43 items dealing with specific diving conditions and activites, was used to document the diving backgrounds of the two groups. Five of the 43 items were found to significantly and uniquely differentiate between the two groups. Those attending the Saturation Diving Program a) made more dives between 46-61 m (151-200 ft), b) had more experience with semiclosed-circuit SCUBA, c) attended more deep-diving training courses, d) made fewer dives in water warmer than 70 degrees F, and e) had fewer specialized qualifications outside deep diving. The multiple regression analysis which differentiated between the two groups resulted in an R of 0.48. These five items indicate that volunteering for saturation diving is consistent or congruent with past deep-diving experience, while remaining in conventional diving is congruent with previous shallow-water experience. These results indicate that the DEQ may be a highly useful method of differentiating between experienced divers.

Diving↗
PubMed1976

Associations between psychological factors and pulmonary toxicity during intermittent oxygen breathing at 2 ATA.

Associations between the psychological and pulmonary effects of breathing intermittent oxygen at 2 ATA were examined among four experienced divers. A fifth diver, who served as a control, breathed only normoxic nitrogen. Psychological tests included digit span, short-term memory for easy and difficult word associations, simple and complex psychomotor performance, and reported moods. The criterion of oxygen toxicity was the total hours of intermittent oxygen exposure tolerated before developing a 10% reduction in vital capacity. Short-term memory for difficult word associations and self-reported moods of Activity, Depression, Fatigue, and Happiness were found to be significantly correlated with this criterion of oxygen toxicity. Part of the impairment found on these measures, however, was probably related to the absence of adequate sleep and rest as evidenced by the worsened performance of the control diver over the 15-h testing period. The results replicated the findings of earlier research on the psychological effects of continuous oxygen breathing under hyperbaric conditions and at 1 ATA, and may indicate that oxygen intesifies the effects of other stressors such as fatigue. In addition, the results showed that reported moods may be important indicators of impending pulmonary toxicity during intermittent oxygen exposure.

Activities of Daily Living↗
PubMed1976

Blood viscosity in man following decompression: correlations wiht hematocrit and venous gas emboli.

Whole blood viscosities were measured in U.S. Navy personnel before and after chamber compressions to 5 ATA (132FSW) and 7.4 ATA (210 FSW) by a new method described here. Bubble scores as a quantitative measure of venous gas emboli were determined during decompression and for 30 min thereafter. Hematocrit was measured both before and after each dive. There were five cases of decompression sickness in the two groups. No significant changes in whole blood viscosity, or hematocrit, were noted either in the group that was affected by decompression sickness or in all of the subjects taken as a group. No correlations between total bubble score and changes in viscosity or hematocrit could be made. These results imply that no major changes in viscosity occur in the usual forms of decompression sickness encountered in human beings.

Blood Viscosity↗
PubMed1976

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.

Adult↗
PubMed1976

Gas phase separation during decompression in man: ultrasound monitoring.

During two dive series, one to 132 fsw and one to 210 fsw, Doppler ultrasonic bubble detectors were used to monitor venous gas bubbles in divers during decompression and for 30 min thereafter. Various decompression schedules were used. Bubble scores were evaluated by independent listerners to tape recordings in a blind manner. A significant increase in bubble scores throughout the stages of decompression and postdecompression was demonstrated as well as a statistically significant relationship between bubble score and decompression sickness. A reduction in mean bubble score was found in divers who made an additional deep decompression stop that was unrelated to the extension of the decompression time. The implications of these findings are discussed.

Adult↗
PubMed1975

Psychological characteristics of deep submergence vehicle personnel.

The personality and developmental characteristics of U.S. Navy Deep Submergence Vehicle (DSV) personnel, including operators and crews, were documented and compared to the characteristics of U.S. Navy divers. The results show that DSV operators (DSV Oprs) had a significantly less asocial developmental pattern than divers, while developmental experiences of DSV crews (DSV Crs) were similar to those of divers. Personality measures (EPPS) indicate that both DSV Oprs and DSV Crs are presently more sociable as adults than divers and would probably be more effective in situations involving small group interaction. The modifications which have occurred in the behavior of DSV Crs may be related to experience in the highly interpersonal DSV situation. The findings also show that DSV Oprs prefer to take fewer risks than divers, while the DSV Crs are more like divers in risk-taking behavior. The implications of this research to DSV mission effectiveness are discussed.

Adult↗