Subjective Narcosis Assessment Scale: measuring the subjective experience of nitrogen narcosis.

BACKGROUND: The interaction of subjective experiences and objective measures of neuropsychological performance during hyperbaric exposure has received less attention in the literature, in part due to the shortage of available and appropriately standardized measures. OBJECTIVE: This study aimed to describe the psychometric properties of a modified version of the Subjective High Assessment Scale when used in the hyperbaric context, by exploring internal reliability, factor structure, associations with psychological variables and simple cognitive delayed recall, and the effect of task focus on the recall of subjective experience. METHOD: Seventy qualified divers completed dry hyperbaric chamber dives to 607.95 kPa, and completed ratings of their subjective experiences. Some also completed a delayed recall task and psychological measures prior to their dives. RESULTS: The scale displayed good internal consistency, with four meaningful factors emerging. It showed some significant but small associations with trait anxiety and transient mood states, and a small to moderate correlation with recall performance. There was no significant effect of task focus on self-report of subjective experiences. CONCLUSION: The modified scale, renamed the Subjective Narcosis Assessment Scale here, has useful psychometric properties, and promising potential for future use.

Neuroendocrine and psychological assessment in a guinness 10 days scuba dive.

This study was designed to evaluate physiological and psychological stress parameters in 2 professional trained scuba divers, using a unique physiopathologic model, offered by the guinness 240 hours scuba dive. Two scuba dive masters have spent 240 hours at 6 - 8 meters depth (26.4 ft) in Ponza Island water (Italy). Blood samples were collected daily in the underwater bell; samples were carried out of water in waterproof bags. Breath samples were collected, measuring ethylene release. Psychological assessment was performed using the State and Trait Anxiety Inventory and the Zung self-rating depression scale. In the studied subjects, cortisol and prolactin showed physiological pulsatile secretion. Breath ethylene didn't exceed normal values. At the start of the study, no subjects showed high levels of state anxiety, trait anxiety and current depression. Psychometric scales scores remained steady during the diving period and no subjects showed anxiety and/or depression and/or panic symptoms during the time of observation. The present study shows that, although the long-time diving, well trained professional divers did not develop anxiety and/or depression. No subject discontinued the diving due to occurred psychological disorders or systemic events. The present report shows that the long-term diving permanence is possible, at least in well trained scuba divers.

The nontechnical causes of diving accidents: can U.S. Navy divers learn from other industries?

Although U.S. Navy diving is remarkably safe, because of the high-risk environment in which military divers work, accidents and mishaps do occur. Failures in leadership and situation awareness (particularly in risk and time assessment) were found to be the two most common causes of fatal and nonfatal U.S. Navy diving accidents and near misses. Responses to an attitude survey showed that junior divers want to ask questions, but senior divers do not desire to be questioned. In other high reliability industries (e.g. aviation, medicine) methods have been developed to identify, analyze and mitigate human error. The relevance of these techniques for U.S. Navy diving are discussed.

The reduced oxygen breathing paradigm for hypoxia training: physiological, cognitive, and subjective effects.

UNLABELLED: The current training program for hypoxia familiarization requires a low-pressure chamber that places aviator trainees at risk for decompression sickness. A cost-effective reduced oxygen-breathing (ROB) paradigm that decreases oxygen (O2) concentration leading to normobaric hypoxia was assessed as an alternative to the hypobaric chamber. PURPOSE: To help establish the validity of the ROB paradigm, this report documents cognitive performance, cardiopulmonary and subjective changes during ROB exposure. METHODS: Performance on a two-dimensional tracking task, as well as BP, heart rate, end-tidal carbon dioxide (ETCO2), O2 saturation, and subjective reports of hypoxia symptoms were observed in 12 U.S. Navy divers during exposure to normoxic air followed by one of four experimental gas mixtures per session. All participants received all gas conditions that differed in their relative concentrations of O2 and nitrogen (6.20/93.80, 7.00/93.00, 7.85/92.15, and 20.85/79.15% O2/N2). RESULTS: ROB caused increases in tracking task error (p < 0.0001). ROB also increased heart rate (p < 0.001) and systolic BP (p = 0.004), and decreased ETCO2 and O2 saturation (p < 0.0001). Finally, subjects responded to ROB-induced hypoxia with higher subjective symptom ratings (p < 0.0001). CONCLUSIONS: These data are consistent with those expected from hypoxic states and support the validity of the ROB paradigm for hypoxia training. Future validation studies comparing a ROB device with hypobaric chambers are needed.

Assessment of vertical excursions and open-sea psychological performance at depths to 250 fsw.

A series of 10 two-man descending vertical excursion dives was carried out in the open sea from an ocean-floor habitat off the coast of Puerto Rico by four aquanauts saturated on a normoxic-nitrogen breathing mixture at a depth of 106 fsw. The purpose of these dives was two-fold: to validate laboratory findings with respect to decompression schedules and to determine whether such excursions would produce evidence of adaptation to nitrogen narcosis. For the latter, tests designed to measure time estimation, short-term memory, and auditory vigilance were used. The validation of experimental excursion tables was carried out without incidence of decompression sickness. Although no signs of nitrogen narcosis were noted during testing, all subjects made significantly longer time estimates in the habitat and during the excursions than on the surface. Variability and incomplete data prevented a statistical analysis of the short-term memory results, and the auditory vigilance proved unusable in the water.