INTRODUCTION: Computerized color contrast sensitivity (CS) tests that aim to determine presence, type, and severity of color vision deficiency have been developed and are available, but data on agreement between tests is lacking. The purpose of the present study was to determine data agreement between three computerized color vision tests.METHODS: A total of 50 subjects, 25 color vision normal (CVN) and 25 color vision deficient (CVD), were tested with the Konan CCT-HD^®, NCI, and a modified version of the Innova CCT. Sensitivity and specificity were compared across systems as well as differences in log CS values and how these relate to standards used to classify occupational performance.RESULTS: Each test showed 100% sensitivity for detection of hereditary red-green CVDs as well as type (protan vs. deutan). Each test showed 100% specificity for confirming normal red-green color vision in CVNs. Innova CCT and NCI showed 100% specificity in CVNs and CVDs for S cone CS. Konan CCT-HD^® showed 96% specificity in CVNs and 92% in CVDs for S cone CS.DISCUSSION: These findings indicate that each test reliably identifies hereditary CVD and confirms normal color vision. However, the three tests differ slightly in log CS values used to determine pass/fail scores of red-green color vision using a 100-point scale, and all show that protans consistently score lower than deutans on cone CS. Hence, depending on the criterion used in occupational settings, a single score may not prove equitable for individuals who have a protan deficiency.Lovell J, Rabin J. A comparison between three computer-based cone specific color vision tests. Aerosp Med Hum Perform. 2023; 94(2):54–58.

BACKGROUND: Unexplained physiological events (PE), possibly related to hypoxia and hyperventilation, are a concern for some air forces. Physiological monitoring could aid research into PEs, with measurement of arterial oxygen saturation (S_po₂) often suggested despite potential limitations in its use. Given similar physiological responses to hypoxia and hyperventilation, the present study characterized the cardiovascular and respiratory responses to each.METHODS: Ten healthy subjects were exposed to 55 mins of normobaric hypoxia simulating altitudes of 0, 8000, and 12,000 ft (0, 2438, and 3658 m) while breathing normally and voluntarily hyperventilating (doubling minute ventilation). Respiratory gas analysis and spirometry measured end-tidal gases (P_ETo₂ and P_ETco₂) and minute ventilation. S_po₂ was assessed using finger pulse oximetry. Mean arterial, systolic, and diastolic blood pressure were measured noninvasively. Cognitive impairment was assessed using the Stroop test.RESULTS: Voluntary hyperventilation resulted in a doubling of minute ventilation and lowered P_ETco₂, while altitude had no effect on these. P_ETo₂ and S_po₂ declined with increasing altitude. However, despite a significant drop in P_ETo₂ of 15.2 mmHg from 8000 to 12,000 ft, S_po₂ was similar when hyperventilating (94.7 ± 2.3% vs. 93.4 ± 4.3%, respectively). The only cardiovascular response was an increase in heart rate while hyperventilating. Altitude had no effect on cognitive impairment, but hyperventilation did.DISCUSSION: For many cardiovascular and respiratory variables, there is minimal difference in responses to hypoxia and hyperventilation, making these challenging to differentiate. S_po₂ is not a reliable marker of environmental hypoxia in the presence of hyperventilation and should not be used as such without additional monitoring of minute ventilation and end-tidal gases.Haddon A, Kanhai J, Nako O, Smith TG, Hodkinson PD, Pollock RD. Cardiorespiratory responses to voluntary hyperventilation during normobaric hypoxia. Aerosp Med Hum Perform. 2023; 94(2):59–65.

BACKGROUND: As part of a larger project to provide recommendations regarding limitations and best practices for shifting aviators from day to night operations, a study was conducted to assess the efficacy of high energy visible (HEV) light to shift the circadian rhythm in humans. The study attempted to replicate the patterns of military aviators who could be required to shift abruptly from day to night flight operations.METHODS: Simulated flight performance and salivary melatonin levels of 10 U.S. military aviators were collected over a 3-night period using a within-subject dim light melatonin onset (DLMO) study design. Data were collected in a laboratory with participants returning home to sleep following each of the three evenings/nights of data collection. Light treatment included a single 4-h exposure of blue-enriched white light (∼1000 lux) on night 2. Data collected included melatonin levels, light exposure, sleepiness, cognitive workload, and simulated flight performance.RESULTS: The average delay in melatonin onset was 1.32 ± 0.37 h (range: 53 min to 1 h 56 min). Sleepiness (P = 0.044) and cognitive workload (P = 0.081) improved the night following the light treatment compared to the baseline. No systematic differences were identified in flight performance.DISCUSSION: The HEV light treatment successfully delayed the circadian phase of all participants even though participants’ ambient light levels (including daylight) outside the laboratory were not controlled. These findings were used to develop circadian synchronization plans for aviators who are asked to transition from day to night operations. These plans will be assessed in a follow-on study in an operational unit.Shattuck NL, Matsangas P, Reily J, McDonough M, Giles KB. Using light to facilitate circadian entrainment from day to night flights. Aerosp Med Hum Perform. 2023; 94(2):66–73.

BACKGROUND: Obstructive sleep apnea syndrome (OSAS) is a major problem in aviation medicine because it is responsible for sleepiness and high cardiovascular risk, which could jeopardize flight safety. Residual sleepiness after the treatment is not a rare phenomenon and its management is not homogenous in aviation medicine. Thus, we decided to perform a study to describe this management and propose guidelines with the help of the literature.METHODS: This is a retrospective study including all aircrew members with a history of OSAS who visited our aeromedical center between 2011 and 2018. Residual sleepiness assessment was particularly studied.RESULTS: Our population was composed of 138 aircrew members (mean age 50.1 ± 9.6 yr, 76.8% civilians, 80.4% pilots); 65.4% of them had a severe OSAS with a mean Epworth Sleepiness Scale (ESS) at 8.5 ± 4.7 and a mean apnea hypopnea index of 36.2 ± 19.2/h. Of our population, 59.4% performed maintenance of wakefulness tests (MWT) and 10.1% had a residual excessive sleepiness. After the evaluation, 83.1% of our population was fit to fly.DISCUSSION: An evaluation of treatment efficiency is required in aircrew members with OSAS. Furthermore, it is important to have an objective proof of the absence of sleepiness. In this case, ESS is not sufficient and further evaluation is necessary. Many tests exist, but MWT are generally performed and the definition of a normal result in aeronautics is important. This evaluation should not be reserved to solo pilots only.Monin J, Rebiere E, Guiu G, Bisconte S, Perrier E, Manen O. Residual sleepiness risk in aircrew members with obstructive sleep apnea syndrome. Aerosp Med Hum Perform. 2023; 94(2):74–78.

INTRODUCTION: Aircrew in-flight bladder relief remains an understudied stressor; specifically the effects of withholding urination on flight-relevant cognitive performance. This quasi-experimental study investigated whether voluntary urinary retention over a 3-h period negatively impacted cognitive performance.METHODS: We assessed vigilance using the psychomotor vigilance task (PVT) and measured the P3b event-related potential (ERP) in response to PVT stimuli. We also measured working memory (WM) performance using a change detection task and assessed the contralateral delay activity during the WM task using electroencephalography (EEG). Subjects (N = 29) completed a baseline test on both tasks, following bladder voiding and immediately after consuming 0.75 L of water. Subjects performed tasks at 1, 2, and 3 h post-void and urgency to void one’s bladder was assessed regularly. A total of 17 subjects were able to complete the entire study protocol. Repeated-measures ANOVAs assessed changes in PVT and WM outcomes.RESULTS: Reaction time (RT) on the PVT was significantly impaired (5% slower) with longer urinary retention time and showed a 2.5-fold increase in the number of lapses (RT > 500 ms) with increased retention time. Together these results indicate that sustained attention was impaired with increased voluntary urine retention. We did not see significant changes in WM performance with our manipulations. Additionally, neural measures acquired with EEG for both tasks did not show any significant effect.DISCUSSION: As measured with the PVT, sustained attention was impaired during 3 h of voluntary urinary retention, highlighting the need for further development of adequate bladder relief systems in military aviation.Griswold CA, Vento KA, Blacker KJ. Voluntary urinary retention effects on cognitive performance. Aerosp Med Hum Perform. 2023; 94(2):79–85.

BACKGROUND: A diagnosis in acute abdomen may remain elusive especially when the cause is rare. We report this interesting case of a fighter pilot presenting with acute abdominal pain. The case posed significant challenges in reaching the correct diagnosis of abdominal crunch syndrome. The syndrome is rare with only seven reports in the literature so far. To the best of our knowledge, this is the first ever report of this condition in an aircrew.CASE REPORT: A 37-yr-old pilot presented with severe upper abdominal pain and sweating. During examination, he developed bradycardia and was admitted with a presumptive diagnosis of acute coronary syndrome. Investigations revealed no myocardial ischemia on ECG, transaminitis, raised CPK, CKMB, and LDH. A CECT scan of chest and abdomen was normal. A GI surgery consult was sought where we connected the transaminitis and raised CPK and considered the possibility of rhabdomyolysis. On specific inquiry, the aviator gave history of unaccustomed exercise with a vigorous session of abdominal crunches a day prior. Thus, a diagnosis of abdominal crunch syndrome was concluded.DISCUSSION: The aviator did not associate his vigorous exercise with the occurrence of pain and, therefore, did not mention it. It would have avoided unnecessary investigations and delay in treatment. From the aeromedical safety aspect, had the aviator flown on the day he developed pain, there was a possibility of developing severe pain exacerbated by the G force and G suit and sudden in-flight incapacitation. From the perspective of the aircrew, it is advisable that they avoid sudden, unaccustomed exercise.Kumar A, Kaistha S. Abdominal crunch syndrome creates a diagnostic challenge in treating a pilot with acute upper abdominal pain. Aerosp Med Hum Perform. 2023; 94(2):86–89.

BACKGROUND: In spaceflight, acute urinary retention (AUR) could develop as a sequela of medication use, urinary tract infection, urolithiasis, or intentional urine holding. While AUR is generally treated with bladder decompression, urinary catheterization could be difficult operationally in terms of training and proficiency, supplies, and lack of space or privacy. This report discusses a case in which tamsulosin and lorazepam were used successfully on an offshore ship while awaiting medical evacuation, a situation that could arise in remote locations where aerospace operations are conducted.CASE REPORT: A 52-yr-old man with hypertension and obstructive sleep apnea but no formal diagnosis of benign prostatic hyperplasia was unable to urinate for over 16 h while on a deep-sea fishing vessel approximately 200 nmi offshore. By phone, the physician providing remote medical direction diagnosed AUR in the setting of possible infection and prescribed acetaminophen, ciprofloxacin, and a trial of tamsulosin as the ship did not have any medical personnel trained to perform urinary catheterization and there were no catheter supplies available. Lorazepam was later added for anxiolysis and potential smooth muscle relaxation. Within 1 h of initial medication administration, the patient successfully voided a large quantity of urine, which tested positive for infection by urine dipstick. The patient was continued on antibiotics and evacuated to a medical facility onshore for further management.DISCUSSION: Pharmacological treatment could be considered as a temporizing measure where operational constraints limit the ability to perform urinary catheterization to relieve acute urinary retention.Law J, Cardy V. Pharmacological relief of acute urinary retention in a remote environment. Aerosp Med Hum Perform. 2023; 94(2):90–93.