Hyperoxia and Hypoxic Hypoxia Effects on Simple and Choice Reaction Times.

Introduction: Effects of exposure to hyperoxia (PiO2 > 105 mmHg), normoxia (PiO2 95-105 mmHg) and hypoxia (PiO2 < 95 mmHg) on simple and choice reaction performance tasks were evaluated.

Methods: Ten subjects performed simple and choice reaction time tests (SRT and CRT, respectively) at ground level for 40 min (20 min normoxic, 20 min hyperoxic, randomly assigned), 3048 m (10,000 ft) for 75 min (15 min hyperoxic, 60 min hypoxic), 4572 m (15,000 ft) for 60 min (15 min hyperoxic, 45 min hypoxic), and 6096 m (20,000 ft) for 35 min (15 min hyperoxic, 20 min hypoxic). SRT and CRT tests were also conducted at ground level 1 h after normoxic rest (recovery) to assess any recovery time effect on these psychomotor tasks.

Recurrence of Neurological Deficits in an F/A-18D Pilot Following Loss of Cabin Pressure at Altitude.

Introduction: Supersonic, high altitude aviation places its pilots and aircrew in complex environments, which may lead to injury that is not easily diagnosed or simply treated. Decompression illness (either venous or arterial) and environmental conditions (e.g.

Cognition Effects of Low-Grade Hypoxia.

Introduction: The effects of low-grade hypoxia on cognitive function are reported in this paper. The study compared cognitive function during short exposures at four different altitudes.

Methods: Ninety-one subjects were exposed to simulated altitudes of ground level, 1524, 2438, and 3658 m (5000, 8000, and 12,000 ft) in the Brooks City-Base altitude pressure chamber in a balanced design.

Pathophysiology, prevention, and treatment of ebullism.

Introduction: Ebullism is the spontaneous evolution of liquid water in tissues to water vapor at body temperature when the ambient pressure is 47 mmHg or less. While injuries secondary to ebullism are generally considered fatal, some reports have described recovery after exposure to near vacuum for several minutes. The objectives of this article are to review the current literature on ebullism and to present prevention and treatment recommendations that can be used to enhance the safety of high altitude activities and space operations.

Altitude decompression sickness incidence among U-2 pilots: 1994-2010.

Introduction: The U-2 aircraft exposes its pilots to cabin pressures equivalent to 29,500 ft (8992 m) during flight, placing them at risk for decompression sickness (DCS). Historical data documenting DCS in the U-2 pilot community is lacking. This study assesses how rates and types of DCS have changed temporally in the U-2 flight program.

Neurological altitude decompression sickness among U-2 pilots: 2002-2009.

Introduction: Compared to the previous 47 yr, U-2 pilots reported an increased number of altitude decompression sickness (DCS) incidents with central nervous system (CNS) manifestations during 2002-2009. Due to increasing incident severity during military operations, the U.S.

Fifty years of decompression sickness research at Brooks AFB, TX: 1960-2010.

Unlabelled: INTRODUCTION, FACILITIES, AND METHODS: Decompression sickness (DCS) occurring in hypobaric environments related to aviation or spaceflight was a major focus of research at Brooks AFB/City-Base, TX, throughout the period 1960-2010. Multiple hypobaric chambers and extensive support facilities were built for research on altitude DCS using both human subjects and animal models. Areas of study included symptomatology, incidence, prediction, and prevention of DCS.

Air break during preoxygenation and risk of altitude decompression sickness.

Introduction: To reduce the risk of decompression sickness (DCS), current USAF U-2 operations require a 1-h preoxygenation (PreOx). An interruption of oxygen breathing with air breathing currently requires significant extension of the PreOx time. The purpose of this study was to evaluate the relationship between air breaks during PreOx and subsequent DCS and venous gas emboli (VGE) incidence, and to determine safe air break limits for operational activities.

Headache and altitude decompression sickness: joint pain or neurological pain?

Introduction: Exposure to reduced ambient pressure may result in decompression sickness (DCS). Headache is among the DCS symptoms encountered and is usually regarded as neurological DCS, which is traditionally classified as serious DCS. Since cranial sutures may be considered joints, it is possible that some headaches are actually joint pain and when associated with decompression sickness need not be neurological DCS.

Decompression sickness during simulated extravehicular activity: ambulation vs. non-ambulation.

Background: Extravehicular activity (EVA) is required from the International Space Station on a regular basis. Because of the weightless environment during EVA, physical activity is performed using mostly upper-body movements since the lower body is anchored for stability. The adynamic model (restricted lower-body activity; non-ambulation) was designed to simulate this environment during earthbound studies of decompression sickness (DCS) risk.

Partial pressure of nitrogen in breathing mixtures and risk of altitude decompression sickness.

Background: Many aircraft oxygen systems do not deliver 100% O2. Inert gases can be present at various levels. The purpose of this study was to determine the effect of these inert gas levels on decompression sickness (DCS).

Altitude decompression sickness susceptibility: influence of anthropometric and physiologic variables.

Introduction: There is considerable variability in individual susceptibility to altitude decompression sickness (DCS). The Air Force Research Laboratory Altitude DCS Research Database consists of extensive information on 2980 altitude exposures conducted with consistent procedures and endpoint criteria. We used this database to quantify the variation in susceptibility and determine if anthropometric and/or physiologic variables could be used to predict DCS risk.

Depressurization in military aircraft: rates, rapidity, and health effects for 1055 incidents.

Introduction: Aircraft cabin depressurization is a rare event but one which demands attention because of the grave potential for aircrew incapacity in flight. The purpose of the current study was to determine rates of depressurization incidents for U.S.

Altitude decompression sickness between 6858 and 9144 m following a 1-h prebreathe.

Introduction: The zero prebreathe altitude threshold for developing 5% decompression sickness (DCS) symptoms in men has been reported to be 6248 m (20,500 ft). However, such an altitude threshold when 1 h of oxygen prebreathe is used has not been well documented and was the primary purpose of this study.

Methods: The 51 male human subjects were exposed to 9144 m (30,000 ft), 8382 m (27,500 ft), 7620 m (25,000 ft), and/or 6858 m (22,500 ft) for 8 h.

Central nervous system decompression sickness and venous gas emboli in hypobaric conditions.

Introduction: Altitude decompression sickness (DCS) that involves the central nervous system (CNS) is a rare but potentially serious condition. Identification of early symptoms and signs of this condition might improve treatment.

Methods: We studied data from 26 protocols carried out in our laboratory over the period 1983-2003; all were designed to provoke DCS in a substantial proportion of subjects.

Altitude decompression sickness at 7620 m following prebreathe enhanced with exercise periods.

Introduction: Over 80% altitude decompression sickness (DCS) was reported during a 4-h exposure with mild exercise to 7620 m (25,000 ft) without prebreathe. Prebreathe for more than 1 h would be necessary to reduce the DCS risk below 40%. Use of a single period of exercise to enhance prebreathe effectiveness has been successfully tested and used during some U-2 operations.

Decompression sickness risk model: development and validation by 150 prospective hypobaric exposures.

Introduction: High altitude exposure has an inherent risk of altitude decompression sickness (DCS). A predictive DCS model was needed to reduce operational risk. To be operationally acceptable, such a theoretical model would need to be validated in the laboratory using human subjects.

Altitude decompression sickness symptom resolution during descent to ground level.

Introduction: Altitude decompression sickness (DCS) is a health risk associated with the conduct of high altitude airdrop operations, high altitude reconnaissance, future fighter operations, hypobaric chamber training, unpressurized flight, and extravehicular activity (EVA) in space. The treatment for DCS includes the provision of 100% oxygen (O2) at ground level (GLO) and/or hyperbaric oxygen therapy (HBO). In this paper we examine the effect of repressurization to ground level from hypobaric conditions on DCS symptoms.

Staged decompression to 3.5 psi using argon-oxygen and 100% oxygen breathing mixtures.

Introduction: The current extravehicular activity (EVA) space suit at 4.3 psia causes hand and arm fatigue and is too heavy for Martian EVA. A 3.

The risk of altitude decompression sickness at 12,000 m and the effect of ascent rate.

Introduction: Loss of aircraft cabin pressurization can result in very rapid decompression rates. The literature contains reports of increased or unchanged levels of altitude decompression sickness (DCS) resulting from increasing the rate of decompression. We conducted two prospective exposure profiles to quantify the DCS risk at 12,192 m (40,000 ft), and to determine if there was a greater DCS hazard associated with a much higher rate of decompression than typically used during past DCS studies.

Case history of serious altitude decompression sickness following rapid rate of ascent.

Neurologic and respiratory decompression sickness (DCS) symptoms occurring in the same individual represent complications rarely observed in altitude research. A case is presented of multi-symptom serious DCS resulting from exposure to 12,192 m (40,000 ft). Following 90 min of preoxygenation, the patient was decompressed in a hypobaric chamber from ground level to 12,192 m in 30 s.

Gender not a factor for altitude decompression sickness risk.

Introduction: Early, retrospective reports of the incidence of altitude decompression sickness (DCS) during altitude chamber training exposures indicated that women were more susceptible than men. We hypothesized that a controlled, prospective study would show no significant difference.

Methods: We conducted 25 altitude chamber decompression exposure profiles.

Enhancement of preoxygenation for decompression sickness protection: effect of exercise duration.

Introduction: Since strenuous exercise for 10 min during preoxygenation was shown to provide better protection from decompression sickness (DCS) incidence than resting preoxygenation, a logical question was: would a longer period of strenuous exercise improve protection even further?

Hypothesis: Increased strenuous exercise duration during preoxygenation increases DCS protection.

Methods: There were 60 subjects, 30 men and 30 women, who were exposed to 9,144 m (4.3 psia) for 4 h while performing mild, upper body exercise.

Decompression sickness latency as a function of altitude to 25,000 feet.

Introduction: Current Air Force Instructions (AFIs) allow flight of unrestricted duration in unpressurized aircraft up to 25,000 ft. Supplemental oxygen is required to prevent hypoxia, but decompression sickness (DCS) is not adequately considered in current oxygen use guidelines. Recent information from the Air Force Research Laboratory (AFRL) DCS database, combined with a projected increase in exposure to these altitudes under proposed USAF missions, suggests that DCS may be operationally significant in certain circumstances.