Identifying the Causes of Unexplained Dyspnea at High Altitude Using Normobaric Hypoxia with Echocardiography.

Exposure to high altitude results in hypobaric hypoxia, leading to physiological changes in the cardiovascular system that may result in limiting symptoms, including dyspnea, fatigue, and exercise intolerance. However, it is still unclear why some patients are more susceptible to high-altitude symptoms than others. Hypoxic simulation testing (HST) simulates changes in physiology that occur at a specific altitude by asking the patients to breathe a mixture of gases with decreased oxygen content. This study aimed to determine whether the use of transthoracic echocardiography (TTE) during HST can detect the rise in right-sided pressures and the impact of hypoxia on right ventricle (RV) hemodynamics and right to left shunts, thus revealing the underlying causes of high-altitude signs and symptoms. A retrospective study was performed including consecutive patients with unexplained dyspnea at high altitude. HSTs were performed by administrating reduced FiO2 to simulate altitude levels specific to patients' history. Echocardiography images were obtained at baseline and during hypoxia. The study included 27 patients, with a mean age of 65 years, 14 patients (51.9%) were female. RV systolic pressure increased at peak hypoxia, while RV systolic function declined as shown by a significant decrease in the tricuspid annular plane systolic excursion (TAPSE), the maximum velocity achieved by the lateral tricuspid annulus during systole (S' wave), and the RV free wall longitudinal strain. Additionally, right-to-left shunt was present in 19 (70.4%) patients as identified by bubble contrast injections. Among these, the severity of the shunt increased at peak hypoxia in eight cases (42.1%), and the shunt was only evident during hypoxia in seven patients (36.8%). In conclusion, the use of TTE during HST provides valuable information by revealing the presence of symptomatic, sustained shunts and confirming the decline in RV hemodynamics, thus potentially explaining dyspnea at high altitude. Further studies are needed to establish the optimal clinical role of this physiologic method.

Pulmonary Function in Human Spaceflight.

Human spaceflight is entering a time of markedly increased activity fueled by collaboration between governmental and private industry entities. This has resulted in successful mission planning for destinations in low Earth orbit, lunar destinations (Artemis program, Gateway station) as well as exploration to Mars. The planned construction of additional commercial space stations will ensure continued low Earth orbit presence and destinations for science but also commercial spaceflight participants. The human in the journey to space is exposed to numerous environmental challenges including increased gravitational forces, microgravity, altered human physiology during adaptation to weightlessness in space, altered ambient pressure, as well as other important stressors contingent on the type of mission and destination. This chapter will cover clinically important aspects relevant to lung function in a normally proceeding mission; emergency scenarios such as decompression, fire, etc., will not be covered as these are beyond the scope of this review. To date, participation in commercial spaceflight by those with pre-existing chronic medical conditions is very limited, and hence, close collaboration between practicing pulmonary specialists and aerospace medicine specialists is of critical importance to guarantee safety, proper clinical management, and hence success in these important endeavors.

Visual Vestibular Conflict Mitigation in Virtual Reality Using Galvanic Vestibular Stimulation.

BACKGROUND: Virtual reality (VR) is an effective technique to reduce cost and increase fidelity in training programs. In VR, visual and vestibular cues are often in conflict, which may result in simulator-induced motion sickness. The purpose of this study is to investigate the integration of Galvanic Vestibular Stimulation (GVS) with a VR flight training simulator by assessing flight performance, secondary task performance, simulator sickness and presence.METHODS: There were 20 participants who performed 2 separate VR flight simulation sessions, with and without GVS (control). Flight performance, secondary task performance, and electrogastrogram were measured during VR flight simulation. The standardized simulator sickness and presence questionnaires were administered.RESULTS: Electrogastrogram measures such as dominant power instability coefficient (DPIC) and percentages of bradygastric waves (%B) were lower in the GVS session than the control session in the flight simulation (DPIC: 0.44 vs. 0.54; %B: 21.2% vs. 30.5%) and postflight (DPIC: 0.38 vs. 0.53; %B: 22.8% vs. 31.4%) periods. Flight performance (#hit-gates) was improved in the GVS session compared to the control (GVS: 17, Control: 15.5). Secondary task performance (%hits) was improved with GVS for the Easy task (GVS: 55.5%, Control: 43.1%).DISCUSSION: This study demonstrates the potential of synchronizing GVS with visual stimuli in VR flight training to reduce visual-vestibular sensory conflict to improve fidelity and performance. These results provide initial evidence, but continued research is warranted to further understand the benefits and applications of GVS in VR simulator training.Pradhan GN, Galvan-Garza RC, Perez AM, Stepanek J, Cevette MJ. Visual vestibular conflict mitigation in virtual reality using galvanic vestibular stimulation. Aerosp Med Hum Perform. 2022; 93(5):406-414.

Bellagio II Report: Terrestrial Applications of Space Medicine Research.

AbstractINTRODUCTION: For over 50 yr, investigators have studied the physiological adaptations of the human system during short- and long-duration spaceflight exposures. Much of the knowledge gained in developing health countermeasures for astronauts onboard the International Space Station demonstrate terrestrial applications. To date, a systematic process for translating these space applications to terrestrial human health has yet to be defined.METHODS: In the summer of 2017, a team of 38 international scientists launched the Bellagio ll Summit Initiative. The goals of the Summit were: 1) To identify space medicine findings and countermeasures with highest probability for future terrestrial applications; and 2) To develop a roadmap for translation of these countermeasures to future terrestrial application. The team reviewed public domain literature, NASA databases, and evidence books within the framework of the five-stage National Institutes of Health (NIH) translation science model, and the NASA two-stage translation model. Teams then analyzed and discussed interdisciplinary findings to determine the most significant evidence-based countermeasures sufficiently developed for terrestrial application.RESULTS: Teams identified published human spaceflight research and applied translational science models to define mature products for terrestrial clinical practice.CONCLUSIONS: The Bellagio ll Summit identified a snapshot of space medicine research and mature science with the highest probability of translation and developed a Roadmap of terrestrial application from space medicine-derived countermeasures. These evidence-based findings can provide guidance regarding the terrestrial applications of best practices, countermeasures, and clinical protocols currently used in spaceflight.Sides MB, Johnston SL III, Sirek A, Lee PH, Blue RS, Antonsen EL, Basner M, Douglas GL, Epstein A, Flynn-Evans EE, Gallagher MB, Hayes J, Lee SMC, Lockley SW, Monseur B, Nelson NG, Sargsyan A, Smith SM, Stenger MB, Stepanek J, Zwart SR; Bellagio II Team. Bellagio II report: terrestrial applications of space medicine research. Aerosp Med Hum Perform. 2021; 92(8):650669.

Oculometric Feature Changes During Acute Hypoxia in a Simulated High-Altitude Airdrop Scenario.

BACKGROUND: Severe acute hypoxia results in a rapid deterioration of cognitive functioning and thus poses a risk for human operations in high altitude environments. This study aimed at investigating the effects of oxygen system failure during a high-altitude high-opening (HAHO) parachute jump scenario from 30,000 ft (9144 m) on human physiology and cognitive performance using a noncontact eye-tracking task.METHODS: Nine healthy male volunteers (ages 27-48) were recruited from the Norwegian Special Operations Commandos. Eye-tracking data were collected to derive information on cognitive performance in the context of rapid dynamic changes in pressure altitude while performing a modified King-Devick test. The baseline data was collected at 8000 ft (2438 m) while breathing 100% oxygen during decompression. For every test, the corresponding arterial blood gas analysis was performed.RESULTS: The study subjects endured severe hypoxia, which resulted in significant prolongations of fixation time (range: 284.1-245.6 ms) until 23,397 ft (131 m) and fixation size (range: 34.6-32.4 mm) until 25,389 ft (7739 m) as compared to the baseline (217.6 ± 17.8 ms and 27.2 ± 4.5 mm, respectively). The increase in the saccadic movement and decrease in the saccadic velocity was observed until 28,998 ft and 27,360 ft (8839 and 8339 m), respectively.DISCUSSION: This is the first study to investigate cognitive performance from measured oculometric variables during severe hypobaric hypoxia in a simulated high-altitude airdrop mission scenario. The measurement of altered oculometric variables under hypoxic conditions represents a potential avenue to study altered cognitive performance using noncontact sensors that can derive information and serve to provide the individual with a warning from impending incapacitation.Pradhan GN, Ottestad W, Meland A, Kåsin JI, Høiseth LØ, Cevette MJ, Stepanek J. Oculometric feature changes during acute hypoxia in a simulated high-altitude airdrop scenario. Aerosp Med Hum Perform. 2021; 92(12):928-936.

Supplemental CO2 improves oxygen saturation, oxygen tension, and cerebral oxygenation in acutely hypoxic healthy subjects.

Oxygen is viewed in medicine as the sole determinant of tissue oxygenation, though carbon dioxide homeostasis is equally important and clinically often ignored. The aims of this study were as follows: (a) to examine the effects of different acute hypoxic conditions on partial pressure of arterial oxygen ( PaO2 ), arterial oxygen saturation of hemoglobin ( SaO2 ), and regional cerebral saturation of hemoglobin (rSO2 ); and (b) to evaluate supplemental CO2 as a tool to improve oxygenation in acutely hypoxic individuals. We hypothesized that exposure to gas mixtures with added CO2 would improve oxygenation in hypoxic human subjects. Twenty healthy subjects were exposed to 5-min intervals of two gas mixtures: hypoxic gas mixture containing 8% oxygen, and a CO2 -enriched mixture containing 8% oxygen plus either 3% or 5% CO2 . Ten subjects received the 3% CO2 -enriched mixture, and the remaining 10 subjects received the 5% CO2 -enriched mixture. The order of exposure was randomized. Blood gases, pulse oximetry, end-tidal CO2 , and cerebral oximetry were measured. Compared to the purely hypoxic gas group, PaO2 was increased in the 3% and 5% CO2 -enriched groups by 14.9 and 9.5 mmHg, respectively. Compared to pure hypoxia, SaO2 was increased in the 3% and 5% CO2 -enriched groups by 16.8% and 12.9%, respectively. Both CO2 -enriched gas groups had significantly higher end-exposure rSO2 and recovered to baseline rSO2 within 1 min, compared to the pure hypoxic gas group, which returned to baseline in 5 min. These results suggest that in acutely hypoxic subjects, CO2 supplementation improves blood oxygen saturation and oxygen tension as well as cerebral oxygenation measures.

Myocardial adaptability in young and older-aged sea-level habitants sojourning at Mt Kilimanjaro: are cardiac compensatory limits reached in older trekkers?

INTRODUCTION: High-altitude ascent induces left (LV) and right (RV) ventricular adaptations secondary to hypoxia-related hemodynamic and myocardial alterations. Since cardiopulmonary decrements observed with aging (e.g., decreased LV compliance and increased pulmonary vascular resistance) may limit cardiac plasticity, this study examined myocardial adaptability throughout an 11 day sojourn to 5893 m in young and older-aged trekkers. METHODS AND RESULTS: Echocardiography was performed on 14 young (8 men; 32 ± 5 years) and 13 older-aged (8 men; 59 ± 5 years) subjects on non-trekking days (Day 0: 880 m; Day 3: 3100 m; Day 8: 4800 m; Day 12/post-climb: 880 m). RV systolic pressure (mmHg) was systematically higher in older-aged subjects (p < 0.01) with similar progressive increases observed during ascent for young and older subjects, respectively (Day 0: 18 ± 1 vs 20 ± 2; Day 3: 25 ± 2 vs 29 ± 3; Day 8: 30 ± 2 vs 35 ± 2). Estimates of LV filling pressure (E/E') were systematically higher in older subjects (p < 0.01) with similar progressive decreases observed during ascent for young and older-aged subjects, respectively (Day 0: 5.6 ± 0.3 vs 6.7 ± 0.5; Day 3: 5.1 ± 0.2 vs 6.1 ± 0.3; Day 8: 4.7 ± 0.3 vs 5.4 ± 0.3). Overall, RV end-diastolic and end-systolic area increased at altitude (p < 0.01), while LV end-diastolic and end-systolic volume decreased (p < 0.01). However, all RV and LV morphological measures were similar on Day 3 and Day 8 (p > 0.05), and returned to baseline post-climb (p > 0.05). Excluding mild LV dilatation in some older-aged trekkers on Day 8/Day 12 (p < 0.01), altitude-induced morphological and functional adaptations were similar for all trekkers (p > 0.05). CONCLUSION: Altitude-induced myocardial adaptations are chamber specific, secondary to RV and LV hemodynamic alterations. Despite progressive hemodynamic alterations during ascent, morphological and functional cardiac perturbations plateaued, suggesting rapid myocardial adaptation which was mostly comparable in young and older-aged individuals.

Discovering Oculometric Patterns to Detect Cognitive Performance Changes in Healthy Youth Football Athletes.

In this paper, we focus on the application of oculometric patterns extracted from raw eye movements during a mental workload task to assess changes in cognitive performance in healthy youth athletes over the course of a typical sport season. Oculometric features pertaining to fixations and saccades were measured on 116 athletes in pre- and post-season testing. Participants were between 7 and 14 years of age at pre-season testing. Due to varied developmental rates, there were large interindividual performance differences during a mental workload task consisting of reading numbers. Based on different reading speeds, we classified three profiles (slow, moderate, and fast) and established their corresponding baselines for oculometric data. Within each profile, we describe changes in oculomotor function based on changes in cognitive performance during the season. To visualize these changes in multidimensional oculometric data, we also present a multidimensional visualization tool named DiViTo (diagnostic visualization tool). These experimental, computational informatics and visualization methodologies may serve to utilize oculometric information to detect changes in cognitive performance due to mild or severe cognitive impairment such as concussion/mild traumatic brain injury, as well as possibly other disorders such as attention deficit hyperactivity disorders, learning/reading disabilities, impairment of alertness, and neurocognitive function.

The influence of thoracic gas compression and airflow density dependence on the assessment of pulmonary function at high altitude.

The purpose of this report was to illustrate how thoracic gas compression (TGC) artifact, and differences in air density, may together conflate the interpretation of changes in the forced expiratory flows (FEFs) at high altitude (>2400 m). Twenty-four adults (10 women; 44 ± 15 year) with normal baseline pulmonary function (>90% predicted) completed a 12-day sojourn at Mt. Kilimanjaro. Participants were assessed at Moshi (Day 0, 853 m) and at Barafu Camp (Day 9, 4837 m). Typical maximal expiratory flow-volume (MEFV) curves were obtained in accordance with ATS/ERS guidelines, and were either: (1) left unadjusted; (2) adjusted for TGC by constructing a "maximal perimeter" MEFV curve; or (3) adjusted for both TGC and differences in air density between altitudes. Forced vital capacity (FVC) was lower at Barafu compared with Moshi camp (5.19 ± 1.29 L vs. 5.40 ± 1.45 L, P < 0.05). Unadjusted data indicated no difference in the mid-expiratory flows (FEF25-75% ) between altitudes (∆ + 0.03 ± 0.53 L sec-1 ; ∆ + 1.2 ± 11.9%). Conversely, TGC-adjusted data revealed that FEF25-75% was significantly improved by sojourning at high altitude (∆ + 0.58 ± 0.78 L sec-1 ; ∆ + 12.9 ± 16.5%, P < 0.05). Finally, when data were adjusted for TGC and air density, FEFs were "less than expected" due to the lower air density at Barafu compared with Moshi camp (∆-0.54 ± 0.68 L sec-1 ; ∆-10.9 ± 13.0%, P < 0.05), indicating a mild obstructive defect had developed on ascent to high altitude. These findings clearly demonstrate the influence that TGC artifact, and differences in air density, bear on flow-volume data; consequently, it is imperative that future investigators adjust for, or at least acknowledge, these confounding factors when comparing FEFs between altitudes.

Correlating Multi-dimensional Oculometrics with Cognitive Performance in Healthy Youth Athletes.

There is a need for a practical objective measure to detect mild changes in cognitive performance as early signs of concussion in youth or other special populations. In this paper, we propose a novel correlation model that establishes the relationship between oculometrics extracted from raw eye movements during a mental workload task and cognitive performance. We assessed differences in cognitive performance in terms of age for youth athletes based on oculometrics pertaining to fixations and saccades. In this cross-sectional study, oculometrics were measured on 440 healthy youth athletes aged 7 to 15 years. Oculometrics pertaining to fixations (fixation time, fixation size, and surface area of fixation) and saccades (total saccadic amplitude, average saccadic amplitude, and saccadic velocity) were measured and compiled into a multivariate oculometric database by age. We discovered that the combined power of fixations and saccades provided the strongest correlation with cognitive performance-a finding that is evident across all ages as well as all levels of mental workload difficulty. Specifically, the combined observations of fixation time, saccadic velocities, and saccadic amplitudes provided us an understanding of cognitive performance during different levels of mental workload difficulty across all age groups. This study is the first step towards establishing normative, multi-dimensional oculometrics for fixations and saccades in young athletes (7 to 15 years) who are at risk for concussion in sports and recreational activities.

Acute hypoxia in a simulated high-altitude airdrop scenario due to oxygen system failure.

High-Altitude High Opening (HAHO) is a military operational procedure in which parachute jumps are performed at high altitude requiring supplemental oxygen, putting personnel at risk of acute hypoxia in the event of oxygen equipment failure. This study was initiated by the Norwegian Army to evaluate potential outcomes during failure of oxygen supply, and to explore physiology during acute severe hypobaric hypoxia. A simulated HAHO without supplemental oxygen was carried out in a hypobaric chamber with decompression to 30,000 ft (9,144 m) and then recompression to ground level with a descent rate of 1,000 ft/min (305 m/min). Nine subjects were studied. Repeated arterial blood gas samples were drawn throughout the entire hypoxic exposure. Additionally, pulse oximetry, cerebral oximetry, and hemodynamic variables were monitored. Desaturation evolved rapidly and the arterial oxygen tensions are among the lowest ever reported in volunteers during acute hypoxia. PaO2 decreased from baseline 18.4 (17.3-19.1) kPa, 138.0 (133.5-143.3) mmHg, to a minimum value of 3.3 (2.9-3.7) kPa, 24.8 (21.6-27.8) mmHg, after 180 (60-210) s, [median (range)], N = 9. Hyperventilation with ensuing hypocapnia was associated with both increased arterial oxygen saturation and cerebral oximetry values, and potentially improved tolerance to severe hypoxia. One subject had a sharp drop in heart rate and cardiac index and lost consciousness 4 min into the hypoxic exposure. A simulated high-altitude airdrop scenario without supplemental oxygen results in extreme hypoxemia and may result in loss of consciousness in some individuals.NEW & NOTEWORTHY This is the first study to investigate physiology and clinical outcome of oxygen system failure in a simulated HAHO scenario. The acquired knowledge is of great value to make valid risk-benefit analyses during HAHO training or operations. The arterial oxygen tensions reported in this hypobaric chamber study are among the lowest ever reported during acute hypoxia.

Interprofessional orientation for health professionals utilising simulated learning: Findings from a pilot study.

We describe a novel, interprofessional educational intervention pilot used to orient new health profession employees through the simulation laboratory. Health profession employees were recruited to engage in a simulation training session that focused on communication, collaboration, and healthcare roles and responsibilities. Learners (N = 11) were divided into two groups with representation from various health disciplines. Each group participated in a simulated patient scenario while the other group actively observed in another classroom. At the end of both sessions, the group reconvened for a debriefing session. Participants were given a survey before and after the training session, to evaluate the content, experience, and value to their practice. The pre- and post-evaluation survey analysis showed improvement in all objectives with a mean (SD) pre-evaluation score of 4.10 (0.40-1.01) and mean (SD) post-evaluation score of 4.73 (0.30-0.81). Results were favourable, and plans to expand this project are under way.

Clinical Use of Pulse Wave Analysis: Proceedings From a Symposium Sponsored by North American Artery.

The use of pulse wave analysis may guide the provider in making choices about blood pressure treatment in prehypertensive or hypertensive patients. However, there is little clinical guidance on how to interpret and use pulse wave analysis data in the management of these patients. A panel of clinical researchers and clinicians who study and clinically use pulse wave analysis was assembled to discuss strategies for using pulse wave analysis in the clinical encounter. This manuscript presents an approach to the clinical application of pulse waveform analysis, how to interpret central pressure waveforms, and how to use existing knowledge about the pharmacodynamic effect of antihypertensive drug classes in combination with brachial and central pressure profiles in clinical practice. The discussion was supplemented by case-based examples provided by panel members, which the authors hope will provoke discussion on how to understand and incorporate pulse wave analysis into clinical practice.

Acute hypoxic hypoxia and isocapnic hypoxia effects on oculometric features.

INTRODUCTION: Visual performance impairment after hypoxia is well recognized in military and civilian aviation. The aims of this study were: 1) to assess oculometric features such as blink metrics, pupillary dynamics, fixations, and saccades as cognitive indicators of early signs of hypoxia; and 2) to analyze the impact of different hypoxic conditions ["hypoxic hypoxia" (HH) and "isocapnic hypoxia" (IH)] on specified oculometrics during mental workloads. METHODS: Oculometric data were collected on 25 subjects under 3 conditions: normoxia, HH (8% O2 + balance N2), and IH (7% O2 + 5% CO2 + balance N2). The mental workload task consisted of reading aloud linear arrays of numbers after exposure to gas mixtures. RESULTS: Blink rates were significantly increased under hypoxic conditions (by +100.7% in HH and by +92.8% in IH compared to normoxia). A faster recovery of blink rate was observed in transitioning from IH (23.6% vs. 76.3%) to normoxia. The percentage change in pupil size fluctuation was increased under HH more than under IH (29% vs. 4.4%). Under HH average fixation time and target area size were significantly higher than under IH. Total saccadic times under hypoxic conditions were significantly increased compared with normoxia. CONCLUSIONS: These results suggest that oculometric changes are indicators of hypoxia, which can be monitored using compact, portable, noninvasive eye-tracking devices in a cockpit analogous environment to detect hypoxia-induced physiological changes in aircrew. Comparative results between HH and IH support the potential role of carbon dioxide in augmenting cerebral perfusion and hence improved tissue oxygen delivery.

Electrogastrographic and autonomic responses during oculovestibular recoupling in flight simulation.

INTRODUCTION: Simulator sickness causes vestibulo-autonomic responses that increase sympathetic activity and decrease parasympathetic activity. The purpose of the study was to quantify these responses through electrogastrography and cardiac interbeat intervals during flight simulation. METHODS: There were 29 subjects that were randomly assigned to 2 parallel arms: (1) oculovestibular recoupling, where galvanic vestibular stimulation was synchronous with the visual field; and (2) control. Electrogastrography and interbeat interval data were collected during baseline, simulation, and post-simulation periods. A simulator sickness questionnaire was administered. RESULTS: Statistically significant differences were observed in percentage of recording time with the dominant frequency of electrogastrography in normogastric and bradygastric domains between the oculovestibular recoupling and control groups. Normogastria was dominant during simulation in the oculovestibular recoupling group. In the control group, the percentage of recording time with the dominant frequency decreased by 22% in normogastria and increased by 20% in bradygastria. The percentage change of the dominant power instability coefficient from baseline to simulation was 26% in the oculovestibular recoupling group vs. 108% in the control group. The power of high-frequency components for interbeat intervals did not change significantly in the oculovestibular recoupling group and was decreased during simulation in the control group. DISCUSSION: Electrogastrography and interbeat intervals are sensitive indices of autonomic changes in subjects undergoing flight simulation. These data demonstrate the potential of oculovestibular recoupling to stabilize gastric activity and cardiac autonomic changes altered during simulator and motion sickness.

Description and preliminary evaluation of a diabetes technology simulation course.

BACKGROUND: We aim to provide data on a diabetes technology simulation course (DTSC) that instructs internal medicine residents in the use of continuous subcutaneous insulin infusion (CSII) and continuous glucose monitoring system (CGMS) devices. METHODS: The DTSC was implemented during calendar year 2012 and conducted in the institution's simulation center. It consisted of a set of prerequisites, a practicum, and completion of a web-based inpatient CSII-ordering simulation. DTSC participants included only those residents in the outpatient endocrinology rotation. Questionnaires were used to determine whether course objectives were met and to assess the satisfaction of residents with the course. Questionnaires were also administered before and after the endocrine rotation to gauge improvement in familiarity with CSII and CGMS technologies. RESULTS: During the first year, 12 of 12 residents in the outpatient endocrinology rotation completed the DTSC. Residents reported that the course objectives were fully met. The mean satisfaction score with the course ranged from 4.0 to 4.9 (maximum, 5), with most variables rated above 4.5. Self-reported familiarity with the operation of CSII and CGMS devices increased significantly in the postrotation survey compared with that on the prerotation survey (both p < .01). CONCLUSIONS: In this pilot program, simulation-based education increased the perceived familiarity of residents with CSII and CGMS technologies. In light of these preliminary findings, the course will continue to be offered, with further data accrual. Future work will involve piloting the DTSC approach among other types of providers, such as residents in other specialties or inpatient nursing staff.

Early detection of hypoxia-lnduced cognitive impairment using the King-Devick test.

INTRODUCTION: Hypoxic incapacitation continues to be a significant threat to safety and operations at high altitude. Noninvasive neurocognitive performance testing is desirable to identify presymptomatic cognitive impairment, affording operators at altitude a tool to quantify their performance and safety. METHODS: There were 25 subjects enrolled in this study. Cognitive performance was assessed by using the King-Devick (K-D) test. The performance of the subjects on the K-D test was measured in normoxia followed by hypoxia (8% 02 equivalent to 7101 m) and then again in normoxia. RESULTS: K-D test completion time in hypoxia for 3 min was significantly longer than the Baseline Test (54.5 +/- 12.4 s hypoxic vs. 46.3 +/- 10.4 s baseline). Upon returning to normoxia the completion time was significantly shorter than in hypoxia (47.6 +/- 10.6 s post test vs. 54.5 +/- 12.4 s hypoxic). There was no statistically significant difference between baseline test and post test times, indicating that all subjects returned to their normoxic baseline levels. SpO2 decreased from 98 +/- 0.9% to 80 +/- 7.8% after 3 min on hypoxic gas. During the hypoxic K-D test, SpO2 decreased further to 75.8 +/- 8.3%. CONCLUSIONS: In this study the K-D test has been shown to be an effective neurocognitive test to detect hypoxic impairment at early presymptomatic stages. The K-D test may also be used to afford a reassessment of traditional measures used to determine hypoxic reserve time.