Gunshot wounds: 2. Radiology

Radiologists can contribute substantially to the evaluation and treatment of the patient with a gunshot wound. Plain films, CT, angiography, and sometimes MR imaging are used to localize the missile, determine what path it followed in the body, assess missile and bone fragmentation, and identify missile emboli. If the peritoneal cavity was entered by a bullet, a laparotomy is required. Missiles subject to magnetic forces can complicate MR imaging. Certain locations of missile fragments predispose to lead poisoning or lead arthropathy. Angiography is useful for both diagnosis and treatment. Both angiographic hemostasis and percutaneous foreign body removal may be used.     

Abdominal stab wounds: Self-inflicted wounds versus assault wounds

Intentional penetrating wounds, self inflicted or inflicted by others, are increasingly common. As a result, it can be difficult for the forensic examiner to determine whether the cause is self-inflicted or not. This type of trauma has been studied from a psychological perspective and from a surgical perspective but the literature concerning the forensic perspective is poorer. The objective of this study was to compare the epidemiology of abdominal stab wounds so as to distinguish specific features of each type. This could help the forensic scientist to determine the manner of infliction of the wound.We proposed a retrospective monocentric study that included all patients with an abdominal wound who were managed by the visceral surgery department at Angers University Hospital. Demographic criteria, patient history, circumstances and location of the wound were noted and compared. A comparison was drawn between group 1 (self inflicted wound) and group 2 (assault).This study showed that the only significant differences are represented by the patient's prior history and the circumstances surrounding the wound, i.e. the scene and time of day. In our study, neither the site, nor the injuries sustained reveal significant clues as to the origin of the wound. According to our findings, in order to determine the cause, the forensic examiner should thus carefully study the circumstances and any associated injuries.     

UHMS position statement: topical oxygen for chronic wounds.

A small body of literature has been published reporting the application of topical oxygen for chronic non-healing wounds . Frequently, and erroneously, this form of oxygen administration has been referred to as "topical hyperbaric oxygen therapy" or even more erroneously "hyperbaric oxygen therapy." The advocates of topical oxygen claim several advantages over systemic hyperbaric oxygen including decreased cost, increased safety, decreased complications and putative physiologic effects including decreased free radical formation and more efficient delivery of oxygen to the wound surface. With topical oxygen an airtight chamber or polyethylene bag is sealed around a limb or the trunk by either a constriction/tourniquet device or by tape and high flow (usually 10 liters per minute) oxygen is introduced into the bag and over the wound. Pressures just over 1.0 atmospheres absolute (atm abs) (typically 1.004 to 1.013 atm abs) are recommended because higher pressures could decrease arterial/capillary inflow. The premise for topical oxygen, the diffusion of oxygen into the wound adequate to enhance healing, is attractive (though not proven) and its delivery is certainly less complex and expensive than hyperbaric oxygen. When discussing the physiology of topical oxygen, its proponents frequently reference studies of systemic hyperbaric oxygen suggesting that mechanisms are equally applicable to both topical and systemic high pressure oxygen delivery. In fact, however, the two are very different. To date, mechanisms of action whereby topical oxygen might be effective have not been defined or substantiated. Conversely, cellular toxicities due to extended courses of topical oxygen have been reported, although, again these data are not conclusive, and no mechanism for toxicity has been examined scientifically. Generally, collagen production and fibroblast proliferation are considered evidence of improved healing, and these are both enhanced by hyperbaric oxygen therapy. Paradoxically, claims of decreased collagen production and fibroblast inhibition in wounds subjected to topical oxygen have been reported in studies of topical oxygen as a benefit of topical oxygen therapy. The literature on topical oxygen is mostly small case series or small controlled but not randomized trials. Moreover, the studies generally are not aimed at specific ulcer types, but rather at "chronic wounds." This non-specific approach is recognized as a major design flaw in any study of therapies designed to improve impaired wound healing. The only randomized trial for topical oxygen in diabetic foot ulcers actually showed a tendency toward impaired wound healing in the topical oxygen group. Contentions that topical oxygen is superior to hyperbaric oxygen are not proven. There are potentially plausible mechanisms that support both possibly beneficial and detrimental effects of topical oxygen therapy, and thus well designed and executed basic science research and clinical trials are clearly needed. There is some ongoing research in regard to the role of topical oxygen at established wound laboratories. Neither CMS nor other third party payors recognize or reimburse for topical oxygen. Therefore, the policy of the Undersea and Hyperbaric Medical Society in regard to topical oxygen is stated as follows: 1. Topical oxygen should not be termed hyperbaric oxygen since doing so either intentionally or unintentionally suggests that topical oxygen treatment is equivalent or even identical to hyperbaric oxygen. Published documents reporting experience with topical oxygen should clearly state that topical oxygen not hyperbaric oxygen is being employed. 2. Mechanisms of action or clinical study results for hyperbaric oxygen cannot and should not be co-opted to support topical oxygen since hyperbaric oxygen therapy and topical oxygen have different routes and probably efficiencies of entry into the wound and their physiology and biochemistry are necessarily different. 3. The application of topical oxygen cannot be recommended outside of a clinical trial at this time based on the volume and quality of scientific supporting evidence available, nor does the Society recommend third party payor reimbursement. 4. Before topical oxygen can be recommended as therapy for non-healing wounds, its application should be subjected to the same intense scientific scrutiny to which systemic hyperbaric oxygen has been held.     

Oxygen and acceleration.

Significant numbers of high performance fighter aircraft continue to be lost due to acceleration (Gz)-induced loss of consciousness. This is due to the rapid onset of high sustained Gz which results in the sudden loss of blood flow to the brain. Present research efforts to extend Gz tolerance are directed toward the maintenance of cerebral blood flow, i.e. straining maneuvers, anti-G suits, tilt seats. The purpose of this paper is to review the present situation and discuss the potential benefit of breathing 100% oxygen at high pressure. Basic science evidence and experience with hyperbaric oxygen in the clinical setting suggest that if the oxygen concentration in the brain tissue is increased, prior to the onset of Gz, additional time of useful consciousness may be realized. The advanced tactical fighter, now in the design stage, will have a sustained Gz capability of 12-14 Gz. This is above human tolerance at the present time and provides an impetus for future acceleration research. Continued aircraft loss due to Gz loss of consciousness will remain an operational problem in aerospace pathology in the 1990s and beyond.     

Suicidal stab wounds of the throat.

Suicide by stabbing one's throat remains very rare and very few cases have been reported in the forensic literature. In such cases, the important distinction is between suicide and homicide. The direction of stab wounds, their depth, site and number have particular importance in helping to recognize suicide. Suicide when attempted by transfixion of the neck in middle aged and elderly adults often reveals a definite resolution to kill oneself.     

Gunshot wounds: 1. Bullets, ballistics, and mechanisms of injury

The nature and severity of a bullet wound depend on the characteristics of the bullet and of the tissues through which it travels. In addition to the mass and velocity of the bullet, its orientation and whether it fragments or deforms affect the nature of the wound. Two major mechanisms of wounding are described: crushing and stretching of tissue. Understanding the mechanisms by which bullets disrupt tissue can help physicians to evaluate and treat wounds.     

Gunshot wounds: Radiology and wound ballistics

Bullets of equal wounding potential may produce wounds of very different severity. Wounding is an interaction between the missile and the tissue. When attempting to predict wound severity, focusing on missile velocity while forgetting either the properties of the tissue wounded or the missile’s mass and construction leads to very poor predictions. Fortunately, all the poor predictions commonly made are of little consequence as it is the condition of the patient, not the type of firearm or missile used, that determines the treatment needed. Tissue crush and tissue stretch by displacement (temporary cavitation) are the only wounding mechanisms of missiles. Tissue stretch is tolerated very differently by different tissues. Missiles can embolize. Missile type, direction of fire, and order of shots can sometimes be assessed radiologically. Lead bullets or fragements in joints cause lead synovitis, mechanical arthritis, and sometimes lead poisoning. When possible, they should be removed. For shotgun wounds, steel shot may be ferromagnetic and is important to recognize prior to magnetic resonance imaging. Steel shot stays round and does not deform like lead shot. The "billiard ball effect" may compromise assessment of range unless correlated with skin physical examination. This article was presented at the Annual Meeting of the American Society of Emergency Radiology, Scottsdale, Arizona, on March 27, 1995.     

Cancer incidence in the U.S. Air Force: 1989-2002

BACKGROUND: Cancer incidence in U.S. Air Force active duty (AFAD) personnel is unknown. Defining the epidemiology may support more effective prevention and clinical services. METHODS: Standardized incidence ratios (SIRs) for invasive cancer in AFAD personnel during 1989-2002 were determined using U.S. national incidence rates as the reference. SIRs were adjusted for age and race. Cutaneous squamous and basal cell carcinomas (CAs) were excluded. RESULTS: There were 2750 cases: 1986 in men and 764 in women. The all-cancers SIRs were for men, 0.50 (95% CI: 0.48-0.53), and for women, 0.96 (95% CI: 0.89-1.03). Among men, the 10 most frequent cancers (77.6% of total) were, in descending order: melanoma; testicular CA; prostate CA; non-Hodgkin lymphoma; follicular/papillary thyroid CA; Hodgkin's Disease; colorectal CA; brain neuroepithelial CA; and (tied) bladder CA and oral squamous cell CA. Among women, the 10 most frequent cancers (88.1% of total) were, in descending order: breast CA; cervical CA; follicular/papillary thyroid CA; melanoma; Hodgkin's Disease; colorectal CA; (tied) non-Hodgkin lymphoma and ovarian epithelial CA; vulvar CA; and (tied) brain neuroepithelial CA and oral squamous cell CA. Compared with the U.S. population, cancer type-specific SIRs were significantly increased for cervical CA, prostate CA, and vulvar CA (range, 1.44-3.54). SIRs were significantly decreased for bladder CA (men), brain neuroepithelial CA, colorectal CA (men), Hodgkin's Disease (men), non-Hodgkin lymphoma, oral squamous cell CA (men), and testicular CA (range, 0.31-0.68). The remaining SIRs were not significantly different from unity. CONCLUSIONS: The cancer experience of the AFAD population differs substantially from that of the U.S. population.     

Oxygen uptake kinetics during exercise.

The characteristics of oxygen uptake (VO2) kinetics differ with exercise intensity. When exercise is performed at a given work rate which is below lactate threshold (LT), VO2 increases exponentially to a steady-state level. Neither the slope of the increase in VO2 with respect to work rate nor the time constant of VO2 responses has been found to be a function of work rate within this domain, indicating a linear dynamic relationship between the VO2 and the work rate. However, some factors, such as physical training, age and pathological conditions can alter the VO2 kinetic responses at the onset of exercise. Regarding the control mechanism for exercise VO2 kinetics, 2 opposing hypotheses have been proposed. One of them suggests that the rate of the increase in VO2 at the onset of exercise is limited by the capacity of oxygen delivery to active muscle. The other suggests that the ability of the oxygen utilisation in exercising muscle acts as the rate-limiting step. This issue is still being debated. When exercise is performed at a work rate above LT, the VO2 kinetics become more complex. An additional component is developed after a few minutes of exercise. The slow component either delays the attainment of the steady-state VO2 or drives the VO2 to the maximum level, depending on exercise intensity. The magnitude of this slow component also depends on the duration of the exercise. The possible causes for the slow component of VO2 during heavy exercise include: (i) increases in blood lactate levels; (ii) increases in plasma epinephrine (adrenaline) levels; (iii) increased ventilatory work; (iv) elevation of body temperature; and (v) recruitment of type IIb fibres. Since 86% of the VO2 slow component is attributed to the exercising limbs, the major contributor is likely within the exercising muscle itself. During high intensity exercise an increase in the recruitment of low-efficiency type IIb fibres (the fibres involved in the slow component) can cause an increase in the oxygen cost of exercise. A change in the pattern of motor unit recruitment, and thus less activation of type IIb fibres, may also account for a large part of the reduction in the slow component of VO2 observed after physical training.     

Colonography: current status, research directions and challenges. Update 2002

With the introduction of multislice CT technology and faster gradients in MRI, CT and MR colonography are increasingly becoming attractive alternatives for colorectal mass screening. In this article we summarise the current status, research directions, and challenges in CT and MR colonography.