Prophylactic surgery prior to extended-duration space flight: is the benefit worth the risk?

This article explores the potential benefits and defined risks associated with prophylactic surgical procedures for astronauts before extended-duration space flight. This includes, but is not limited to, appendectomy and cholecystesctomy. Furthermore, discussion of treatment during space flight, potential impact of an acute illness on a defined mission and the ethical issues surrounding this concept are debated in detail.

Health challenges including behavioral problems in long-duration spaceflight.

Over the past 60 years, our ability to live and work in space has evolved. From short sojourns in small spacecraft to landing on the moon and residing in an orbiting international space station, we have learned to adapt to an extreme environment and safely return home. Human missions to the Moon, Mars, and exploration of deep space are different. This paper summarizes the challenges of providing medical care, specifically mental health care during long-duration flights. Considerable information about challenges that crews bound for Mars will face is available. Literature regarding this issue is summarized. This manuscript provides a short historical summary of long-duration spaceflight to date; the challenges including limited communication with mission controllers on Earth; and, a summary of the behavioral impacts space flight has had on humans. A look at how the future autonomous systems might support physical and mental health when definitive care is millions of miles away, is also provided. Human spaceflight to Mars or other distant sites will require new approaches to mission preparedness and inflight medical support systems. Exploration class missions will be more autonomous than anything deployed until now. The concepts of telemedicine that have aptly supported crews from the 1960s to the present will no longer be in real-time. While communication between Earth and Mars is possible, it will be characterized by significant time delays. Mars-based crews will need to have systems onboard and on Mars to support all health and performance issues.

Hydrogen sulfide inhalation injury.

Hydrogen sulfide is a colorless, noxious gas with the distinctive smell of rotten eggs. This compound is a powerful reducing agent that is encountered in a number of industrial processes. When hydrogen sulfide is present, it exposes workers to the potentially lethal effects of the rapid hypoxemia that results from exposure to this agent. The "warning sign" is the characteristic smell of rotten eggs; this smell should alert anyone in the area that a potentially serious risk exists. The immediate removal of the victim and administration of high-flow oxygen is essential. Neurologic sequelae may require anticonvulsants and care must be exercised to observe for cardiac, hepatic, and renal insufficiency. Depending on the concentration, hydrogen sulfide can rapidly overcome a potential victim.

The "Airmedical F.A.S.T." for trauma patients--the initial report of a novel application for sonography.

BACKGROUND: While established as an initial screening tool for the evaluation of injured patients at the trauma center, sonographic evaluation of the patient in the prehospital setting remains untested. The purpose of this study was to determine the feasibility of this procedure during prehospital helicopter transport. METHODS: Two qualified flight surgeons performed all imaging studies. Confirmatory endpoints were documented for all images obtained in flight. RESULTS: For this preliminary study, 100 patients are presented; 84 studies were analyzed; 16 were excluded due to patient weight (8), hemodynamic instability (6), or problems with machine calibration (2). Sensitivity was 81.3%; specificity was 100%. The positive predictive value was 100%; the negative predictive value was 95.7%. The accuracy was 96.4%. CONCLUSION: Sonographic studies obtained during air-medical transport are of similar quality and consistency as those obtained in the emergency department. The ability to detect hemoperitoneum in the field may challenge traditional algorithms for prehospital care as a result.

Central retinal artery occlusion by proxy: a cause for sudden blindness in an airline passenger.

The use of gas media in ophthalmologic procedures is relatively commonplace. Scleral buckle and pneumatic retinopexy procedures using air-gas mediums are a widely accepted treatment for retinal detachment. We present a patient who had a scleral buckle with pneumatic retinopexy performed and subsequently flew in a commercial airliner 2 wk later. The patient experienced sudden blindness due to central retinal artery occlusion brought about by expansion of the air bubble when the aircraft reached cruise altitude and a cabin pressure of 8000 ft. The intraocular pressure exceeded the central artery pressure thereby collapsing the artery. The patient's symptoms were relieved when an onboard flight surgeon identified the problem and the cabin pressure was reset to 2000 ft. Flying after an ophthalmic procedure that incorporates intraocular gas may have complications due to the bubble expansion in accordance with Boyle's Law. The ophthalmologic surgeon must be diligent in forewarning patients of the potential complications of flying for weeks to months after a procedure that utilizes intraocular gas.

Automotive airbag-induced second-degree chemical burn resulting in Staphylococcus aureus infection.

A young woman did not seek emergency treatment after a minor automobile collision as she thought that she had been spared serious injury by the inflation of the driver's-side airbag. She had a benign-looking erythema on her neck which, over the next several days, became a second-degree chemical burn infected with Staphylococcus aureus. The burn and subsequent infection took several weeks to heal and the patient had to endure a prolonged course of antibiotics, nonsteroidal antiinflammatory drugs, and continued irrigation. This case exemplifies why alkali chemical burns from an automotive airbag should be treated aggressively, despite their benign appearance, as they may take several days to evolve. Physicians should be warned that careful follow-up examination of patients seen in the hospital emergency department or in the physician's office is necessary to abate any hidden sequelae. Of course, the opportunity to decrease morbidity is lost if the patient does not seek emergency treatment.

Forelimb and hindlimb forces in walking and galloping primates.

One trait that distinguishes the walking gaits of most primates from those of most mammalian nonprimates is the distribution of weight between the forelimbs and hindlimbs. Nonprimate mammals generally experience higher vertical peak substrate reaction forces on the forelimb than on the hindlimb. Primates, in contrast, generally experience higher vertical peak substrate reaction forces on the hindlimb than on the forelimb. It is currently unclear whether this unusual pattern of force distribution characterizes other primate gaits as well. The available kinetic data for galloping primates are limited and present an ambiguous picture about peak-force distribution among the limbs. The present study investigates whether the pattern of forelimb-to-hindlimb force distribution seen during walking in primates is also displayed during galloping. Six species of primates were video-recorded during walking and galloping across a runway or horizontal pole instrumented with a force-plate. The results show that while the force differences between forelimb and hindlimb are not significantly different from zero during galloping, the pattern of force distribution is generally the same during walking and galloping for most primate species. These patterns and statistical results are similar to data collected during walking on the ground. The pattern of limb differentiation exhibited by primates during walking and galloping stands in contrast to the pattern seen in most nonprimate mammals, in which forelimb forces are significantly higher. The data reported here and by Demes et al. ([1994] J. Hum. Evol. 26:353-374) suggest that a relative reduction of forelimb vertical peak forces is part of an overall difference in locomotor mechanics between most primates and most nonprimate mammals during both walking and galloping.

Trabecular bone in the bird knee responds with high sensitivity to changes in load orientation.

Wolff's law of trajectorial orientation proposes that trabecular struts align with the orientation of dominant compressive loads within a joint. Although widely considered in skeletal biology, Wolff's law has never been experimentally tested while controlling for ontogenetic stage, activity level, and species differences, all factors that may affect trabecular bone growth. Here we report an experimental test of Wolff's law using a within-species design in age-matched subjects experiencing physiologically normal levels of bone strain. Two age-matched groups of juvenile guinea fowl Numida meleagris ran on a treadmill set at either 0 degrees (Level group) or 20 degrees (Incline group), for 10 min per day over a 45-day treatment period. Birds running on the 20 degrees inclined treadmill used more-flexed knees than those in the Level group at midstance (the point of peak ground reaction force). This difference in joint posture enabled us to test the sensitivity of trabecular alignment to altered load orientation in the knee. Using a new radon transform-based method for measuring trabecular orientation, our analysis shows that the fine trabecular bone in the distal femur has a high degree of correspondence between changes in joint angle and trabecular orientation. The sensitivity of this response supports the prediction that trabecular bone adapts dynamically to the orientation of peak compressive forces.

Influences of limb proportions and body size on locomotor kinematics in terrestrial primates and fossil hominins.

During locomotion, mammalian limb postures are influenced by many factors including the animal's limb length and body mass. Polk (2002) compared the gait of similar-sized cercopithecine monkeys that differed limb proportions and found that longer-limbed monkeys usually adopt more extended joint postures than shorter-limbed monkeys in order to moderate their joint moments. Studies of primates as well as non-primate mammals that vary in body mass have demonstrated that larger animals use more extended limb postures than smaller animals. Such extended postures in larger animals increase the extensor muscle mechanical advantage and allow postures to be maintained with relatively less muscular effort (Polk, 2002; Biewener 1989). The results of these previous studies are used here to address two anthropological questions. The first concerns the postural effects of body mass and limb proportion differences between australopithecines and members of the genus Homo. That is, H. erectus and later hominins all have larger body mass and longer legs than australopithecines, and these anatomical differences suggest that Homo probably used more extended postures and probably required relatively less muscular force to resist gravity than the smaller and shorter-limbed australopithecines. The second question investigates how animals with similar size but different limb proportions differ in locomotor performance. The effects of limb proportions on gait are relevant to inferring postural and locomotor differences between Neanderthals and modern Homo sapiens which differ in their crural indices and relative limb length. This study demonstrates that primates with relatively long limbs achieve higher walking speeds while using lower stride frequencies and lower angular excursions than shorter-limbed monkeys, and these kinematic differences may allow longer-limbed taxa to locomote more efficiently than shorter-limbed species of similar mass. Such differences may also have characterized the gait of Homo sapiens in comparison to Neanderthals, but more experimental data on humans that vary in limb proportions are necessary in order to evaluate this question more thoroughly.

Adaptive and phylogenetic influences on musculoskeletal design in cercopithecine primates.

Broad allometric studies of the musculoskeletal system have frequently sought to explain how locomotor variables have been influenced by body mass. To examine animals that vary widely in body mass, these studies have included taxa that differ in their locomotor adaptations and phylogenetic relatedness. Because these sources of diversity could obscure the effects of body mass, this study was designed to test the effects of adaptive differences in limb proportions and phylogeny, as well as body mass, on locomotor kinematics and extensor muscle mechanical advantage. More specifically, two hypotheses were tested in a sample of closely related animals: (i) that, among animals with similar body mass, those with longer limb segments should adopt more extended limb postures to moderate the joint and midshaft bending moments that they experience, and (ii) that body mass will have similar influences on joint posture and joint moments in closely related and diverse mammalian samples. Three-dimensional kinematic and synchronous force-platform data were collected for six individual cercopithecine monkeys ranging in mass from 4kg to 24kg and at a range of walking speeds. Comparisons among three monkeys with similar body mass but different limb segment lengths reveal a significant effect of limb proportion on posture. That is, animals with longer limbs frequently use more extended limb postures and can have correspondingly lower joint moments. The scaling of locomotor variables across the entire sample of closely related monkeys was generally similar to published results for a diverse sample of mammals, with larger monkeys having more extended limb postures, lower joint moments and greater effective mechanical advantage (EMA) for their limb extensor musculature. Ankle EMA, however, did not increase with body mass in the primate sample, suggesting that clade-specific adaptive differences (e.g. the use of arboreal supports by primates) may constrain the effects of body mass.

A comparison of primate, carnivoran and rodent limb bone cross-sectional properties: are primates really unique?

The cross-sectional properties of mammalian limb bones provide an important source of information about their loading history and locomotor adaptations. It has been suggested, for instance, that the cross-sectional strength of primate limb bones differs from that of other mammals as a consequence of living in a complex arboreal environment (Kimura, 1991, 1995). In order to test this hypothesis more rigorously, we have investigated cross-sectional properties in samples of humeri and femora of 71 primate species, 30 carnivorans and 59 rodents. Primates differ from carnivorans and rodents in having limb bones with greater cross-sectional strength than mammals of similar mass. This might imply that primates have stronger bones than carnivorans and rodents. However, primates also have longer proximal limb bones than other mammals. When cross-sectional dimensions are regressed against bone length, primates appear to have more gracile bones than other mammals. These two seemingly contradictory findings can be reconciled by recognizing that most limb bones experience bending as a predominant loading regime. After regressing cross-sectional strength against the product of body mass and bone length, a product which should be proportional to the bending moments applied to the limb, primates are found to overlap considerably with carnivorans and rodents. Consequently, primate humeri and femora are similar to those of nonprimates in their resistance to bending. Comparisons between arboreal and terrestrial species within the orders show that the bones of arboreal carnivorans have greater cross-sectional properties than those of terrestrial carnivorans, thus supporting Kimura's general notion. However, no differences were found between arboreal and terrestrial rodents. Among primates, the only significant difference was in humeral bending rigidity, which is higher in the terrestrial species. In summary, arboreal and terrestrial species do not show consistent differences in long bone reinforcement, and Kimura's conclusions must be modified to take into account the interaction of bone length and cross-sectional geometry.

Intubated pediatric patients requiring transport: a review of patients, indications, and standards.

INTRODUCTION: We could not find any studies of nontertiary care facilities performing intubation for patients requiring transport to definitive pediatric care. The purpose of our study was to determine the current practices of pediatric airway management in the prehospital and transport environments. METHODS: A retrospective analysis of all patients younger than 16 years transported by our flight program during a 2-year period served as the population of interest. The flight records (RN and MD documentation) for intubated patients were analyzed for medications, methods, outcomes, and other descriptive endpoints. As a matter of program policy, all pediatric transports are subjected to peer review in the performance improvement committee. RESULTS: During the review period, 732 patients younger than 16 years (range: 30 days to 15 years) were transported by our flight program. Of the 148 (20%) patients intubated for airway control, 81 were boys (55%), and 67 were girls (45%). Sixteen percent were younger than 1 year, 24% were 1 to 2 years old, 18% were 3 to 5, 20% were 6 to 11, and 22% were 12 to 15. Indicators for intubation included unresponsiveness or arrest, 42 (28%); seizures, 38 (26%); respiratory failure, 28 (19%); decreased level of consciousness (LOC), 14 (9%); airway protection, 13 (9%); combativeness, 11 (7%); and other, 2 (1%). Children were intubated most frequently by the referring physician (92 children, 62% of patients). The flight crew performed 49 (33%) intubations, and EMS staff performed seven (5%). Three children were nasally intubated. Significant variation occurred in medications used, endotracheal tube size and position, and nasogastric decompression. No single group performed better or worse than the others in our review. CONCLUSION: Variability exists in the application of pediatric airway management techniques, including pharmacologic modes and intubation indications.