Elevated Environmental Carbon Dioxide Exposure Confounding Physiologic Events in Aviators?

INTRODUCTION: Physiological events (PEs) are a growing problem for US military aviation with detrimental risks to safety and mission readiness. Seeking causative factors is, therefore, of high importance. There is no evidence to date associating carbon dioxide (CO2) pre-flight exposure and decompression sickness (DCS) in aviators. MATERIALS AND METHODS: This study is a case series of six aviators with PE after being exposed to a rapid decompression event (RDE) with symptoms consistent with type II DCS. The analysis includes retrospective review of flight and environmental data to further assess a possible link between CO2 levels and altitude physiologic events (PEs). IRB approval was obtained for this study. RESULTS: This case series presents six aviators with PE after being exposed to a rapid decompression event (RDE) with symptoms consistent with type II DCS. Another three aviators were also exposed to a RDE, but remained asymptomatic. All events involved tactical jet aircraft flying at an average of 35,600' Mean Sea Level (MSL) when a RDE occurred, Retrospective reviews led to the discovery that the affected individuals were exposed, pre-flight, to poor indoor air quality demonstrated by elevated levels of measured CO2. CONCLUSION: PEs are a growing safety concern for the aviation community in the military. As such, increasing measures are taken to ensure safety of flight and completion of the mission. To date, there is no correlation of CO2 exposure and altitude DCS. While elevated CO2 levels cannot be conclusively implicated as causative, this case series suggests a potential role of CO2 in altitude DCS through CO2 direct involvement with emboli gas composition, as well as pro-inflammatory cascade. Aviators exposed to elevated CO2 in poorly ventilated rooms developed PE symptoms consistent with DCS, while at the same command, aviators that were exposed to a well ventilated room did not. This report is far from an answer, but does demonstrate an interesting case series that draws some questions about CO2's role in these aviator's DCS experience. Other explanations are plausible, including the accurate diagnosis of DCS, health variables amongst the aviators, and differences in aircraft and On-Board Oxygen Generation Systems (OBOGS). For a better understanding, the role of environmental CO2 and pre-flight exposure as a risk of DCS should be reviewed.

An Assessment of Flight Surgeon Confidence to Perform En Route Care.

INTRODUCTION: En Route Care (ERC) is often an ad hoc mission for the USN. In a review of 428 Navy patient transports, a Flight Surgeon (FS) was the sole provider or a member of crew in 118 of the transports. Naval FSs receive approximately 4 hours of didactic ERC training during their 24-week Naval FS course. Regardless, an FS may be caring for a critically ill patient in a helicopter. We conducted a survey to evaluate FS confidence in their ability to perform ERC and to establish their understanding of the training of Search and Rescue Medical Technicians (SMT). MATERIALS AND METHODS: A convenience sample of FSs completed a needs analysis survey as part of a process improvement project. Flight Surgeons surveyed were actively assigned or had been assigned within the past year to a squadron with Search and Rescue/MEDEVAC capabilities. RESULTS: A total of 25 surveys were completed. An average of 13 (range 0-100) patient transport missions were performed by the respondents. Twenty-five percent reported feeling confident in their ability to provide ERC without senior level direction, while 41% stated they would require direction. Nearly 70% of the FSs surveyed expressed "minimal" or less understanding of the training of the SMT. CONCLUSIONS: Our survey results reveal most FSs are confident in neither their ability to perform ERC nor the ability of their hospital corpsman to provide care during patient movement.

Changes in Cytokines, Sensory Tests, and Self-reported Pain Levels After Manual Treatment of Low Back Pain.

STUDY DESIGN: Unbalanced 3-factor design with repeated measures on 1 factor. OBJECTIVE: To determine the effect of manual treatment (MT) on cytokine and pain sensations in those with and without low back pain (LBP). SUMMARY OF BACKGROUND DATA: Evidence suggests that MT reduces LBP but by unknown mechanisms. Certain cytokines have been elevated in patients with LBP and may be affected by MT. METHODS: Participants aged 20-60 years with chronic LBP or without LBP were recruited and randomly assigned to MT, sham ultrasound treatment, or no treatment groups. Venous blood samples were collected and pain levels assessed at baseline, 1 hour later, and 24 hours later. Blood was analyzed for interleukin (IL)-1ß, IL-6, tumor necrosis factor-α, and C-reactive protein. Pain levels were measured by pressure pain threshold (PPT), mechanical detection threshold (MDT), dynamic mechanical allodynia, and self-report. RESULTS: Forty (30 women, age 36±11 y) participants completed the study, 33 with LBP (13 MT, 13 sham ultrasound treatment, and 7 no treatment) and 7 without LBP. Participants with or without LBP could not be differentiated on the basis of serum cytokine levels, PPT, or MDT (P≥0.08). There were no significant differences between the groups at 1 hour or 24 hours on serum cytokines, PPT, or MDT (P≥0.07). There was a significant decrease from baseline in IL-6 for the no treatment (LBP) group (P=0.04), in C-reactive protein for the sham ultrasound treatment group (P=0.03), in MDT for all 3 LBP groups (P≤0.02), and in self-reported pain for the MT and sham ultrasound treatment groups (P=0.03 and 0.01). CONCLUSIONS: Self-reported pain was reduced with MT and sham ultrasound treatment 24 hours after treatment, but inflammatory markers within venous circulation and quantitative sensory tests were unable to differentiate between study groups. Therefore, we were unable to characterize mechanisms underlying chronic LBP.

Fluticasone as Treatment for Cluster Headaches in a Navy Aircrew Member.

Cluster headaches (CHs) are one of the most debilitating of all the identified headache syndromes. Their pathogenesis is poorly understood, which has made their treatment challenging. Various medicines and modalities have been put forth in an effort to minimize the symptoms, but none have proven to be consistently reliable. For the active duty military aviator with CHs, this is further compounded by the administrative restrictions to use many of those medications secondary to their unwanted and potentially dangerous side effects. We present a case of refractory CH in an active duty air crewman, treated with fluticasone, which resulted in a remarkable reduction in symptoms allowing him to resume his primary flight duties. We propose that fluticasone's effectiveness in improving his CH symptoms stems from its anti-inflammatory properties.

Manual Therapy for Chronic Low Back Pain in an F-5 Pilot.

INTRODUCTION: Low back pain (LBP) in the aviator can be a significant safety risk because of distraction during flight. Flight Surgeons are tasked with seeking out appropriate medical care that reduces pilot risk while providing squadron-specific mission support. CASE: An F-5 pilot presented with chronic LBP seeking nonpharmacological and noninvasive therapy. After 3 days of manual treatment that corrected sacral, pelvic, and lumbar dysfunction, this pilot reported greater than 80% reduction in overall pain and was able to return to flight. DISCUSSION: Although underreported, a radiographic study and multiple case reports, identify LBP as a significant problem among tactical air (tac air) pilots. As such, LBP can become an in-flight distraction increasing the risk of a mishap. Benefits of osteopathic manipulative therapy (OMT) as an adjunct to treatment of LBP in civilian population were recently demonstrated. This case identified a tac air pilot with chronic LBP that responded to three OMT sessions focused at the sacrum, lumbar, and pelvis. CONCLUSION: The use of manual therapy in the form of OMT significantly reduced this pilot's pain in three visits and maintained flight status per aeromedical waiver guidelines.

Chloramphenicol and acute esophagitis in the emergency department.

Even with its broad spectrum and low cost, concern over chloramphenicol's adverse effects limited its use in the United States during the 1980s. Reports from United Kingdom and China in the 1990s demonstrated a low incidence of blood dyscrasias with the topical preparation of chloramphenicol, and showed continued good efficacy and low cost. Today, topical chloramphenicol is being used by some groups within otolaryngology and ophthalmology in the United States. As a result, emergency physicians are once again considering chloramphenicol-induced side effects in patients presenting to the emergency department. To date, there have been no published reports associating chest pain, dyspnea with chloramphenicol use, and there has only been one report of fungal esophagitis associated with topical chloramphenicol. We present a 31-year-old woman, 4 months status post tympanoplasty with a modified radical canal wall down mastoidectomy due to a cholesteatoma involving the epitympanum who had a residual tympanic membrane defect. She presented to the emergency department with chest "burning", with no other symptoms shortly after starting treatment with an insufflated combination antibiotic containing chloramphenicol. After ruling out cardiopulmonary or vascular etiology, she was treated successfully with a gastrointestinal cocktail cocktail for presumed esophagitis secondary to newly prescribed chloramphenicol.

Fever evaluation cost and time to treatment in the general surgery patient can be reduced by using a fever practice guideline.

OBJECTIVES: Evaluation of surgical patients with fever and leukocytosis (FAL) for an infection source often results in unnecessary laboratory and radiographic tests. The average cost of an FAL work-up ranges from $2200 to $5600. Lack of a systematic approach drives costs higher than necessary. We evaluated differences in time to treatment and costs using usual methods of FAL work-ups versus FAL work-ups using an established fever practice guideline (FPG). METHODS: In phase I, a retrospective electronic chart review was conducted for 82 adult surgery patients who underwent FAL work-ups to determine time from initial temperature presentation to fever treatment and total cost per fever evaluation. In phase II, an established FPG was applied to 30 intensive care unit patients from the original group of 82 using phase I data points. Differences in cost and time to treatment were compared using a paired t-test. RESULTS: Mean time to fever treatment decreased from 51.57 hours pre-FPG use to 11.23 hours afterward (p < 0.001), a 78% reduction in time to definitive treatment. Mean cost of FAL work-up decreased from $1,009.73 without FPG use to $399.00 with a 60% reduction in costs. CONCLUSIONS: Using a standardized FPG, FAL work-up time to treatment and cost can be significantly reduced.

Ultrasonic vocalization production of preweanling rats: effects of central and peripheral administration of alpha2-adrenoceptor agonists.

Stimulation of alpha2-adrenoceptors increases the ultrasonic vocalization production of preweanling rats, however it is not known whether these critical alpha2-adrenoceptors are located peripherally or centrally. In a series of three experiments, ultrasonic vocalizations were measured after 11-day-old rats had been administered clonidine or 2-[2,6-diethylphenylamino]-2-imidazole (ST-91) either systemically (i.p.) or into the third ventricle (i.c.v.). These particular alpha2-adrenoceptor agonists were chosen because clonidine is lipophilic and enters the central nervous system, while ST-91 is hydrophilic and does not readily cross the blood-brain barrier. In the third experiment, clonidine- (1 microg, i.c.v.) and ST-91-induced (15 microg, i.c.v.) ultrasonic vocalizations were measured after systemic injection of the alpha2-adrenoceptor antagonist yohimbine (0.5 or 1 mg/kg, i.p.). Results showed that central administration of both clonidine and ST-91 increased the ultrasonic vocalization production of 11-day-old rats, whereas peripheral administration of only clonidine, and not ST-91, increased ultrasonic vocalizations. These results indicate that the alpha2-adrenoceptors mediating ultrasonic vocalization production are located in the central nervous system. Yohimbine fully attenuated clonidine-induced ultrasonic vocalizations but only partially attenuated ST-91-induced vocalizations. This pattern of results may have been due to the differential selectivity of clonidine and ST-91 for alpha2-adrenoceptor subtypes (alpha2A, alpha2B, and alpha2C) or imidazoline receptors. When combined with past research, the present results are consistent with the hypothesis that centrally located alpha2-adrenoceptors are a component of a neural system that mediates ultrasonic vocalization production.