Dynamic Range of Luminance Perception in Acute Hypobaric Hypoxia.

Rizzi, Alessandro, Alice Plutino, Diego Vecchi, Anton Giulio Guadagno, and Marco Lucertini. Dynamic range of luminance perception in acute hypobaric hypoxia. High Alt Med Biol. 23:313-318, 2022.-The effects of acute hypobaric hypoxia, as potentially experienced in high altitude flight, on the detection of low contrast targets within a high dynamic range (DR) of luminance were investigated. The tests were performed after 10 minutes of adaptation to an ambient luminance level of 0.2 lx. Twenty-four individuals were exposed to hypobaric hypoxia at an altitude of 18,000 ft (5,490 m) inside a hypobaric chamber and were asked to identify the darkest one perceived from a grid of progressively less luminous patches. The results were compared with those obtained by the same subjects at sea level. The results indicate a global reduction of the DR perception during hypoxia, with a mean decrease of 0.023 cd/m2 (standard deviation ±0.064), which resulted statistically significant (p < 0.05). No significant correlations with oxygen saturation levels were observed. These findings might have practical applications in the design of cockpit's instruments, especially those dedicated to night-time flight missions at high altitudes.

A Controversial Assessment of Fitness to Fly After a Traumatic Brain Injury.

INTRODUCTION: After traumatic brain injury (TBI), cognitive, behavioral alterations and seizures frequently occur. Beside instrumental examinations, neuropsychological testing is the common clinical practice for detecting cognitive deficits. However, in highly skilled individuals, subtle changes with a large impact on fitness to fly may be neglected.CASE REPORT: A 28-yr-old Italian Air Force pilot with almost 700 flying hours suffered a TBI. After 2 yr of cognitive retraining programs, as the neuropsychological evaluation executed in a public hospital was within the standards and repeated EEGs had all been normal, the pilot was allowed to resume flying duties. During the refresh flight training, he was not considered proficient for solo flight and was again referred to the Institute of Aerospace Medicine (IMAS), where, due to the absence of a neuropsychologist, the pilot was referred to a public hospital. Again, he was within the normal range and received a fitness to fly with limitations. Nevertheless, the flight instructors noticed the presence of cyclic errors. Consequently, he was sent for a third time to the IMAS, where the cooperation between a neuropsychologist and a flight surgeon allowed a tailored testing.DISCUSSION: With a proper evaluation, the subject showed deficits in topographic visuospatial learning and in prospective memory. After 5 yr, he was finally declared permanently unfit to fly. Specific neuropsychological batteries, simulated flight tests, and aeromedical evaluations are described here.Verde P, Guadagno AG, D'Angelo A, Vitalone R, Di Vita A, Piccardi L. A controversial assessment of fitness to fly after a traumatic brain injury. Aerosp Med Hum Perform. 2022; 93(2):116-122.

Cerebral vascular response in airmen exposed to hypobaric hypoxia.

INTRODUCTION: Cerebral vascular response via local and reflex adjustments is part of the integrated response to hypoxia and is coupled with changes in systemic vascular resistances that allow a redistribution of blood flow toward the brain. The cerebral vascular response in airmen exposed to simulated high altitude is not clear, thus we sought to investigate this aspect. METHODS: Four healthy military airmen were exposed to simulated high altitude in a hypobaric chamber according to a standard training protocol. Blood saturation (SpO2) and blood flow velocity with transcranial Doppler from the left middle cerebral artery (Vm) were continuously recorded. Pulsatility Index (PI), resistance index (RI), and systolic/diastolic ratio (S/D ratio) were computed. Alternate hypoxia-hyperoxia trials for 2 and 1 min, respectively, were used to assess the cerebrovascular response. RESULTS: Acute hypoxia induced an increase in Vm that promptly recovered when the oxygen supply was restored (mean increase of 5.5% at 18,000 ft and 17.2% at 25,000 ft). Alternate hypoxia-hyperoxia at 25,000 and 18,000 ft elicited changes in both SpO2 and Vm. In hypoxia, PI significantly decreased (mean decrease o" 25.6% at 18,000 ft and 39.5% at 25,000 ft), as did RI (mean decrease of 18.7% at 18,000 ft and 34.4% at 25,000 ft), while S/D ratio increased. DISCUSSION: The standard altitude training protocol induced a transient cerebrovascular response. The response was as expected, with hypoxia-induced vasodilation and opposite changes when breathing pure oxygen.

Assessment of gravitational stress on heart rate variability during maneuvers on high performance jet flights.

The Push-Pull Effect (PPE) is a physiological phenomenon defined as a reduction of +Gz tolerance induced by a previous exposure to a -Gz acceleration, that may lead to loss of consciousness. Aim of this study was to evaluate, for the first time, the cardiac rhythm changes associated with PPE during real flights. Data were collected in 3 pilots during flights on the Aermacchi MB- 339-CD aircraft. In each flight, lasting about 60 minutes, ECG, respiration and 3D accelerations were recorded by a new smart garment (the MagIC System). The flight protocol included a maneuver eliciting a reference +5Gz acceleration for 15 seconds (Ref+5G), followed, after a while, by a push-pull maneuver with a profile characterized by a 5-s acceleration at -1Gz (PP-1G) and, with a 1G/s onset, by 15 seconds at +5Gz (PP+5G), so to induce the push-pull gravitational stress. From each ECG recording, a beat-by-beat RR Interval (RRI) series was derived. RRI mean, standard deviation (SDNN) and the RRI Root Mean Square of Successive Difference (RMSSD) were estimated in each pilot during the Ref+5G and the PP+5G maneuvers. As compared with Ref+5G, all pilots displayed significant reductions in RRI mean, SDNN and RMSSD during PP+5G. These findings are compatible with a PP-induced enhancement in the sympathetic drive to the heart -as shown by the reduction in RRI mean and SDNN- and a concomitant deactivation of the parasympathetic control as shown by the reduction in RMSSD.