Mark R. Campbell

Risk of herniated nucleus pulposus among U.S. astronauts.

INTRODUCTION Astronauts have complained of back pain occurring during spaceflight, presumably due to the elongation of the spine from the lack of gravity. Herniated nucleus pulposus (HNP) is known to occur in aviators exposed to high Gz and has been diagnosed in several astronauts in the immediate post-spaceflight period. It is unknown whether astronauts exposed to microgravity are at added risk for developing HNP in the post-spaceflight period due to possible in-flight intervertebral disc changes. METHODS For a preset study period, incidence rates of HNP were compared between the U.S. astronaut population and a matched control population not involved in spaceflight using the Longitudinal Study of Astronaut Health database. Using a Weibull survival model, time trends of the risk of HNP prior to and after spaceflight were compared within the astronaut group. HNP incidences in other populations that have previously been reported in the literature were also compared with results in this study. RESULTS The incidence of HNP was 4.3 times higher in the U.S. astronaut population (N=321) compared to matched controls (N=983) not involved in spaceflight. For astronauts, there was relatively more HNP in the cervical region of the spine (18 of 44) than for controls (3 of 35); however, there was no clear increase of HNP incidence in those astronauts who were high performance jet aircraft pilots. There was evidence suggesting that the risk is increased immediately after spaceflight. CONCLUSIONS Astronauts are at higher risk of incurring HNP, especially immediately following spaceflight.

Endoscopic surgery in weightlessness: The investigation of basic principles for surgery in space

BACKGROUND: Performing a surgical procedure in weightlessness, also called 0-gravity (0-g), has been shown to be no more difficult than in a 1-g environment if the requirements for the restraint of the patient, operator, surgical hardware, are observed. The performance of laparoscopic and thorascopic procedures in weightlessness, if feasible, would offer several advantages over the performance of an open operation. Concerns about the feasibility of performing minimally invasive procedures in weightlessness have included impaired visualization from the absence of gravitational retraction of the bowel (laparoscopy) or thoracic organs (thoracoscopy) as well as obstruction and interference from floating debris such as blood, pus, and irrigation fluid. The purpose of this study was to determine the feasibility of performing laparoscopic and thorascopic procedures and the degree of impaired surgical endoscopic visualization in weightlessness. METHODS: From 1993 to 2000, laparoscopic and thorascopic procedures were performed on 10 anesthetized adult pigs weighing approximately 50 kg in the National Aeronautics and Space Administration (NASA) Microgravity Program using a modified KC-135 airplane. The parabolic simulation system for advanced life support was used in this project, and 20 to 40 parabolas were used for laparoscopic or thorascopic investigation, each containing approximately 30 s of 0-g alternating with 2-g pullouts. The animal model was restrained in the supine position on a floor-level Crew Medical Restraint System, and the abdominal cavity was insufflated with carbon dioxide. The intraabdominal and intrathoracic anatomy was visualized in the 1-g, 0-g, and 2-g periods of parabolic flight. Bleeding was created in the animals, and the behavior of the blood in the abdominal and thoracic cavities was observed. In the thoracic cavity, gas insufflation and mechanical retraction was used at times unilaterally to decrease pulmonary ventilation enough to increase the thoracic domain. RESULTS: Visualization was improved in laparoscopy, from tethering of the bowel by the elastic mesentery, and from the strong tendency for debris and blood to adhere to the abdominal wall because of surface tension forces. The lack of adequate thoracic domain made thorascopy more difficult. Fluid in the thoracic cavity did not impair visualization because the fluid at 0-g does not loculate posteriorly, but disperses along the thoracic wall and mediastinal reflections. CONCLUSIONS: Performing minimally invasive procedures instead of open surgical procedures in a weightless environment has theoretical advantages, especially in the ability to prevent cabin atmosphere contamination from surgical fluids (blood, pus, irrigation). Visualization will become more important and practical as the endoscopic hardware is miniaturized from its current form, as endoscopic technology becomes more advanced, and as more surgically capable medical crew officers are present in future long-duration space exploration missions.

Focused assessment with sonography for trauma in weightlessness: a feasibility study

BACKGROUND The Focused Assessment with Sonography for Trauma (FAST) examines for fluid in gravitationally dependent regions. There is no prior experience with this technique in weightlessness, such as on the International Space Station, where sonography is currently the only diagnostic imaging tool. STUDY DESIGN A ground-based (1 g) porcine model for sonography was developed. We examined both the feasibility and the comparative performance of the FAST examination in parabolic flight. Sonographic detection and fluid behavior were evaluated in four animals during alternating weightlessness (0 g) and hypergravity (1.8 g) periods. During flight, boluses of fluid were incrementally introduced into the peritoneal cavity. Standardized sonographic windows were recorded. Postflight, the video recordings were divided into 169 20-second segments for subsequent interpretation by 12 blinded ultrasonography experts. Reviewers first decided whether a video segment was of sufficient diagnostic quality to analyze (determinate). Determinate segments were then analyzed as containing or not containing fluid. A probit regression model compared the probability of a positive fluid diagnosis to actual fluid levels (0 to 500 mL) under both 0-g and 1.8-g conditions. RESULTS The in-flight sonographers found real-time scanning and interpretation technically similar to that of terrestrial conditions, as long as restraint was maintained. On blinded review, 80% of the recorded ultrasound segments were considered determinate. The best sensitivity for diagnosis in 0 g was found to be from the subhepatic space, with probability of a positive fluid diagnosis ranging from 9% (no fluid) to 51% (500 mL fluid). CONCLUSIONS The FAST examination is technically feasible in weightlessness, and merits operational consideration for clinical contingencies in space.

Laparoscopic surgery in weightlessness

AbstractBackground: Performing a surgical procedure in weightlessness has been shown not to be any more difficult than in a 1g environment if the requirements for the restraint of the patient, operator, and surgical hardware are observed. The feasibility of performing a laparoscopic surgical procedure in weightlessness, however, has been questionable. Concerns have included the impaired visualization from the lack of gravitational retraction of the bowel and from floating debris such as blood. Methods: In this project, laparoscopic surgery was performed on a porcine animal model in the weightlessness of parabolic flight. Results: Visualization was unaffected due to the tethering of the bowel by the elastic mesentery and the strong tendency for debris and blood to adhere to the abdominal wall due to surface tension forces. Conclusions: There are advantages to performing a laparoscopic instead of an open surgical procedure in a weightless environment. These will become important as the laparoscopic support hardware is miniaturized from its present form, as laparoscopic technology becomes more advanced, and as more surgically capable crew medical officers are present in future long-duration space-exploration missions.

Endoscopic surgery and telemedicine in microgravity: developing contingency procedures for exploratory class spaceflight

OBJECTIVES The risk of a urinary calculus during an extended duration mission into the reduced gravity environment of space is significant. For medical operations to develop a comprehensive strategy for the spaceflight stone risk, both preventive countermeasures and contingency management (CM) plans must be included. METHODS A feasibility study was conducted to demonstrate the potential CM technique of endoscopic ureteral stenting with ultrasound guidance for the possible in-flight urinary calculus contingency. The procedure employed the International Space Station/Human Research Facility ultrasound unit for guide wire and stent localization, a flexible cystoscope for visual guidance, and banded, biocompatible soft ureteral stents to successfully stent porcine ureters bilaterally in zero gravity (0g). RESULTS The study demonstrated that downlinked endoscopic surgical and ultrasound images obtained in 0g are comparable in quality to 1g images, and therefore are useful for diagnostic clinical utility via telemedicine transmission. CONCLUSIONS In order to be successful, surgical procedures in 0g require excellent positional stability of the operating surgeon, assistant, and patient, relative to one another. The technological development of medical procedures for long-duration spaceflight contingencies may lead to improved terrestrial patient care methodology and subsequently reduced morbidity.

Intra-abdominal pressure effects on porcine thoracic compliance in weightlessness: implications for physiologic tolerance of laparoscopic surgery in space.

Objective:Laparoscopic surgery (LS) is envisioned as an option for spaceflight, but requires intra-abdominal hypertension (IAH) to create the surgical domain. Prolonged weightlessness induces physiologic deconditioning that questions the ability of ill or injured astronauts to tolerate IAH. On earth, IAH results in marked ventilatory embarrassment. As there has been no previous study of physiologic changes related to LS in weightlessness, we studied anesthetized pigs in parabolic flight. Design:Parabolic flight research laboratory. Subjects:Five anesthetized Yorkshire pigs. Interventions:Subjects were transported from an animal care facility and secured aboard an aircraft capable of generating hypergravity and weightlessness. Mechanical ventilation was performed using pressure control and positive end-expiratory pressure at 15 and 2 cm H2O, respectively; rate 12 breaths/min. Three abdominal conditions were used during LS: insufflation to produce IAH, abdominal wall retraction (AWR), and no abdominal wall manipulation (baseline). During each parabola breath by breath-tidal volumes (Vt) were recorded by a transport ventilator (HT-50 Newport Medical). Measurements and Main Results:Least square means (LS-means) of weight corrected Vt (milliliter per kilogram) by gravity (g) and abdominal condition were determined using a mixed effects model for repeated measures analysis. Increasing gravity (g) consistently reduced Vt (p = 0.0011) as did insufflation (p < 0.0001). In 1g, Vt (LS-mean 13.7, 95% confidence interval [CI]: 12.4–15.0) was relatively unaffected by AWR (LS-mean 12.8, 95% CI: 11.5–14.00), but markedly decreased by IAH (LS-mean 10.00, 95% CI: 8.9–11.1), an effect accentuated in hypergravity (LS-mean 8.1, 95% CI: 6.4–9.8). In weightlessness, Vt reduction during insufflation was near obviated (LS-mean 12.3, 95% CI: 10.6–14.1), and AWR regularly but inconsistently increased the Vt above 1g baseline (LS-mean 13.7, 95% CI: 11.7–15.8). Conclusions:Weightlessness protects against thoracic compliance changes that are inherent in IAH during induced pneumoperitoneum in gravity. The technique-related physiologic cost of performing LS in space deconditioned astronauts should be incorporated into design concepts for space surgery systems.

Intraperitoneal Gas Insufflation Will Be Required for Laparoscopic Visualization in Space: A Comparison of Laparoscopic Techniques in Weightlessness

BACKGROUND Laparoscopic surgery (LS) is contemplated during long duration space flight, but it typically necessitates intraabdominal hypertension (IAH) from insufflation to create a surgical domain. Because there are spontaneous changes in abdominal wall behavior in weightlessness (0g) that have been previously suggested to increase LS visualization, we studied the comparative laparoscopic visualization between gasless (noGAS), abdominal wall retraction (AWR), and standard 15 mmHg gas insufflation (GAS) during weightlessness. STUDY DESIGN In-flight LS was performed on four anesthetized pigs during weightlessness obtained through parabolic flight in a research aircraft. GAS was studied during 27 parabolas and compared with 20 parabolas using AWR-LS and 12 with noGAS. Pelvic visualization was scored in real time during flight by 2 or 3 surgeons per parabola and postflight through review of compiled digital video disk (DVD) images by 29 independent reviewers. Physical measurements of the sagittal (anterior-posterior) and transverse dimensions of anesthetized pigs were recorded during 39 parabolas. RESULTS Despite consistent increases in the sagittal abdominal dimension in weightlessness (GAS and noGAS), on-board scored visualization in 0g was unchanged for noGAS (p=0.78) and decreased during AWR (p=0.09), compared with 1g. Although AWR was considered feasible in 1g, spontaneous visceral movements reduced the surgical domain in 0g. Neither AWR nor noGAS was believed safe. But visualization during GAS in 0g was increased over that in 1g (p < 0.001). CONCLUSIONS Both noGAS and AWR are impractical in weightlessness. Gas insufflation will be required. With insufflation, visualization and perceived ability to perform LS was improved by weightlessness.

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.

Suborbital commercial spacefl ight crewmember medical issues

As directed by the Council of the Aerospace Medical Association, the Commercial Spaceflight Working Group has developed the following position paper concerning medical issues for commercial suborbital spaceflight crewmembers. This position paper has been approved by the AsMA Council to become a policy of the AsMA.

Manual suturing quality at acceleration levels equivalent to spaceflight and a lunar base.

INTRODUCTION Cutaneous wounds, either from injuries or as a result of surgical incisions, are a likely possibility that future space medicine specialists will need to address. While there has been some prior study of manual suturing in microgravity (0 G), there has been no study of manual suturing in reduced gravity consistent with that of the Moon. METHODS Six separate operators with varying degrees of surgical experience (four trained surgeons, and two non-surgeons) attempted to manually suture wound phantoms during the reduced gravity phases of parabolic flight simulating either 0 G or lunar gravity (0.16 G). Each operator subjectively evaluated the difficulty and relative speed in performing the same task in different environments, serving as their own internal control. There were 20-s periods of 1 G that were carefully timed for each surgeon to compare to the approximately 20 s available for each parabola of either 0 G or 0.16 G. RESULTS Six periods of 1 G were used as controls to perform manual suturing of the phantoms. There were 51 parabolas of 0 G and 67 parabolas of 0.16 G performed by the six operators. As judged subjectively by the operators themselves and by group inspection of the sutured phantoms, there was no qualitative difference in the adequacy of wound closure as judged by suture placement accuracy and wound coaptation. There was consensus, though, that suturing in microgravity was significantly slower, as has been noted in more complex surgical studies. DISCUSSION The technical aspects of wound management during exploration-class missions in prolonged microgravity or lunar missions with reduced gravity (0.16 G) will likely not present challenges beyond those faced in addressing the tremendous logistical and training obstacles to providing experienced and equipped surgeons on-board such a mission.