ABSTRACT
Tactical aviation imposes unprecedented physical challenges including repetitive exposure to hypergravity, hyperoxia, increased work of breathing, and profound cognitive workloads. Each stressor evokes outcomes ranging from musculoskeletal duress and atelectasis to physical and cognitive fatigue, the latter among the foremost threats to aviators. Whereas sleep loss is traditionally considered the primary cause of fatigue in aviators, converging experimental, observational, and medical studies have identified biochemical mechanisms promoting onset of fatigue. Those mechanisms, which fundamentally differ from sleep loss, revolve around increased proinflammatory cytokines, produced and released in response to tissue injury, chronic inflammatory disorders, allergens, or physical duress. This study's objective was to inform our understanding of potential relationships between serum levels of proinflammatory cytokines and onset of fatigue within a cohort of aviators who experience multiple high-performance sorties on a daily basis. Methods: Active duty and reservist T-6A Texan II instructor pilots were studied on three separate days across their week-long flying schedule. Data collected included a physical assessment, subjective fatigue levels, venous blood samples for measures of chemistry and serum analytes, and urine samples for specific gravity. Results: Twenty-three persons were studied, of which 22 fulfilled minimum study requirements of completing two sorties. The study cohort was comprised of primarily males, age 37.95 ± 4.73 years with a BMI of 26.63 ± 3.15 kg/m2. Of 37 measurable serum analytes, 20 differed significantly (p < 0.05) between baseline values with those measured at the study endpoint. Thirteen of the aviators reported increased fatigue scores across their flying schedule whereas nine did not. Eleven blood serum analytes were associated with increasing levels of fatigue. Discussion: Fatigue in aviators has been attributed almost solely to sleep loss, nocturnal sorties, or disrupted circadian rhythmicity. In contrast, our study findings suggest an alternative mechanism that can promote onset of fatigue: increased blood levels of proinflammatory cytokines. Specific mechanisms triggering synthesis and release of those cytokines and other analytes are yet to be determined. However, their expression patterns suggest responses to both chronic and acute inflammation, hyperoxia, or bronchopulmonary responses to inspiration of dry gas, positive airway pressure, or perhaps atelectasis.
ABSTRACT
Several classification systems are in use for Legg-Calvé-Perthes disease. Three of them: Catterall, Salter Thompson and Herring (Lateral Pillar) are most commonly used. There has been debate on which is most reliable. The purpose of this paper was to systematically analyse the literature when the classifications were compared. The Ovid (Medline) Database was used and the MeSH terms Perthes Classification and Reliability were inserted. Eleven studies were retrieved but only five were suitable for analysis as they attempted to compare the classifications. Most studies used kappa agreements as the principal outcome measure, although intraclass coefficients and percentage agreements were also used. Only four studies assessed for both intraobserver reproducibility and interobserver reliability. A further study from the references appendages was found to be suitable, and was included in the analysis. Kappa ranged from poor to fair (Salter Thompson), fair to moderate (Catterall) and moderate to good (Herring). The outcome from Legg-Calvé-Perthes disease is extremely variable. Inconsistent interpretation of the plain films may explain this, although it is likely this is multifactorial. The papers in this study show that on balance, the Lateral Pillar classification was most reliable, probably secondary to ease of use. A persistent theme was that the subchondral fracture line in the Salter Thompson system was difficult to interpret and not always present. It also showed that whilst reliability and reproducibility tended to improve with experience, disagreement was not always restricted to more junior personnel. Each classification has its merits but reliability and reproducibility remains unsatisfactory. Digital technology in the future may help delineate the lesions better and improve agreement.
