Isobaric bubble growth: a consequence of altering atmospheric gas.

During certain treatments of decompression sickness following dives made with compressed air, the U.S. Navy advocates breathing helium-oxygen mixtures. However, stable nitrogen bubbles created within gelatin by decompression have been found to enlarge when the atmosphere was switched from nitrogen to helium without changing ambient pressure. This suggests that decompression sickness would be worsened by switching from nitrogen to helium in the breathing gas mixture.

A critical assessment of the roles of circulating hydrogen ion and lactate in the production of exercise-induced asthma.

To evaluate the roles of circulating hydrogen ion and lactate in the production of exercise-induced asthma, two experiments were performed. In the first, we exercised six asthmatic subjects to exhaustion on a bicycle ergometer while recording arterial pH at periodic intervals. Multiple aspects of pulmonary mechanics were measured before and after the work load. After recovery, the identical procedures were repeated, but sufficient quantities of sodium bicarbonate were infused to keep the pH at the pre-exercise level. In both experiments, statistically identical attacks of asthma were induced. To study the effect of lactate, five subjects were exercised on several occasions in order to determine the lowest level of work, and hence arterial lactate, that was reproducibly associated with an acute asthma attack. When this was known, sufficient quantities of sodium lactate were infused into the resting subjects so as to equal or exceed the amount produced with exercise. Pulmonary mechanics were not altered with this intervention. These findings demonstrate that lactic acidemia is not the cause of exercise-induced asthma.

Influence of heat and humidity on the airway obstruction induced by exercise in asthma.

We examined the degree of airway obstruction that developed in eight asthmatics who exercised while breathing air under four conditions: (a) ambient room temperature and water content; (b) body temperature and ambient water content; (c) ambient room temperature fully saturated; and (d) body temperature fully saturated. These test conditions were performed in random order. Multiple aspects of pulmonary mechanics were measured before and 5 min after exercise. When air at ambient conditions was inhaled, the expected airway obstruction developed after exercise, and all variables changes significantly from their pre-challenge values. Heating the air to body temperature did not influence this response. Increasing the humidity at ambient temperatures significantly blunted the response, and by inhaling body temperature, fully saturated air completely prevented it from occurring. Thus, the water content of inspired air is an important variable in the development of exercise induced asthma.

Dietary carbohydrate, muscle glycogen, and exercise performance during 7 d of training.

The effects of moderate- or high-carbohydrate diets on muscle glycogen and performance in runners and cyclists over 7 consecutive days of training were determined. Muscle biopsies were performed on 4 separate days before exercise for 1 h at 75% peak oxygen consumption (VO2) followed by five, 1-min sprints. After the training session on day 7, subjects ran or cycled to exhaustion at 80% peak VO2. Muscle glycogen for cyclists and runners was maintained with the high-carbohydrate diet but was reduced 30-36% (P < 0.05) with the moderate-carbohydrate diet. All subjects completed all training sessions, and there were no differences in times to exhaustion on day 7. For cyclists and runners, consuming a moderate-carbohydrate diet over 7 d of intense training reduces muscle glycogen but has no apparent deleterious effect on training capability or high-intensity exercise performance. A high-carbohydrate diet maintains muscle glycogen, but this has no apparent benefit on training capability or high-intensity exercise performance.

Central venous catheter insertion by femoral vein: safety and effectiveness for the pediatric patient.

Prospective observations made during surveillance of routine central venous catheterizations for hemodynamic monitoring were evaluated to determine the safety and effectiveness of femoral insertion of central venous catheters and to demonstrate the feasibility of teaching pediatric residents to perform this procedure. During a 19-month period of observation, 29 pediatric patients requiring a central venous catheter underwent attempted percutaneous femoral vein catheterization. Femoral catheterization was successful in 86% of patients attempted, and insertions by pediatric residents were successful in 68% of patients attempted. Arterial puncture was the only significant complication of insertion, occurring in 14%, and was not associated with adverse sequelae. During 33 months of observations, complications of indwelling femoral central venous catheters did not significantly exceed the frequency for internal and external jugular, subclavian, and antecubital central venous catheters. During more than 4 years of observation, the significant complications associated with indwelling femoral central venous catheters were swelling of the leg or documented thrombosis in 11% of 74 critically ill patients. These observations indicate safety and effectiveness of femoral central venous catheters which compares favorably to central venous catheter insertion by other routes. In contrast to previous reports of central venous catheter insertion via subclavian and internal jugular veins, we observed no cardiorespiratory compromise as a result of femoral central venous catheter complications. Skill in this technique is a feasible educational goal for pediatric residents.

Predictability of mitral regurgitation detected by Doppler echocardiography in patients referred for cardiac transplantation.

Mitral regurgitation (MR) is common in patients with congestive heart failure (CHF), but the frequency in relation to the origin of ventricular dilatation has not been established. In 50 patients referred for cardiac transplantation, MR was assessed by Doppler echocardiography and the findings were compared with clinical information. Dilatation of the left ventricle, left atrium and mitral anulus was analyzed in 25 patients with respect to cause of CHF. All 50 patients had MR of at least moderate severity, regardless of cause (idiopathic dilated cardiomyopathy in 36, coronary artery disease in 14), length of symptoms (20 +/- 19 months, less than 6 months in 13 patients) or presence of murmurs (absent in 13 patients). Comparison of patients with nonischemic cardiomyopathy to those with ischemic heart disease revealed larger left ventricular volumes (215 +/- 81 vs 131 +/- 60 ml in systole, p less than 0.05) and left atrial volumes (124 +/- 70 vs 70 +/- 35 ml, p less than 0.05). Mitral anular dilatation was present only in patients with idiopathic cardiomyopathy (diameters 3.6 +/- 0.4 vs 3.1 +/- 0.2 cm, p less than 0.05). The frequency of significant MR in these patients with CHF suggests that it may have a major role in decompensation and in the therapeutic response.

A technique to treat wrestlers' auricular hematoma without interrupting training or competition.

Auricular hematoma is a common injury occurring among high school and collegiate wrestlers. Conventional pressure dressings applied over the auricle make it impossible for the athlete to continue to train and to compete, resulting in a high degree of noncompliance. We describe a technique that permits treatment of the hematoma while the athlete continues to train. It involves an incision and drainage followed by the immediate application of a pressure dressing sutured to the auricle. This approach was used to treat 24 auricular hematomas in 19 wrestlers. The analysis demonstrates a low complication rate and documents a rapid return to competition.

Auricular injury and the use of headgear in wrestlers.

Questionnaires designed to assess attitudes and use of headgear were completed by 537 Division I collegiate wrestlers. Only 35.2% of the wrestlers wore headgear all of the time during practice as opposed to 92.4% during competition, which was a statistically significant difference. The most common reason for not wearing headgear was discomfort (35%). There were 482 participating in nonschool team events, and 203 (42%) described headgear use as "seldom or never." However, there was a statistically significant difference of developing auricular hematoma while wearing headgear (26%) vs not wearing headgear (52%). There were 208 (39%) who reported a permanent auricular deformity resulting from an injury that occurred with (10.6%) or without (26.6%) headgear. These results suggest that headgear provides only partial protection and that nonuse is widespread, causing a surprisingly high frequency of permanent auricular deformities.

Illness and absence among wrestlers, swimmers, and gymnasts at a large university.

The object of this study was to document the prevalence of illness and absence in members of three men's intercollegiate athletic teams: varsity wrestling, swimming, and gymnastics. Team members (N = 87) were interviewed weekly in January and February during 8 weeks of their competitive season. Symptoms, signs, and their duration were recorded on a standard form, as well as the number of days of absence from at least one class or team practice or competition. Mean prevalence of illness was 54 per 100 persons during the first 5 weeks of the study and 30 per 100 persons during the last 3 weeks. Eight-six percent of the athletes had at least one respiratory illness during the 8 week period and 40% reported skin problems. There were no significant differences among teams for respiratory or skin problems. Gastrointestinal symptoms were significantly more frequent among swimmers than among wrestlers or gymnasts (chi 2 = 16.1, df = 2, P less than 0.001). During an illness, an athlete was less likely to miss class than practice or competition (chi 2 = 5.33, df = 1, P less than 0.05). We conclude that there were no significant differences in the prevalence of illness among the three teams except that swimmers had more gastrointestinal problems as well as a transient syndrome associated with abnormal water quality (pH) in the swimming pool.

Management of orbital blow-out fractures. Case reports and discussion.

Blow-out fractures are fractures of the orbital floor or medial wall that occur as a consequence of blunt trauma. Impact increases the intraorbital pressure, forcing the nondistensible orbital contents through the orbital floor. The fracture is commonly caused by impact from a baseball or tennis ball. However, any blunt trauma to the orbit, as from a knee or elbow, can result in a blow-out fracture. The characteristic clinical findings include double vision, a sunken globe, and numbness in the distribution of the infraorbital nerve. Sometimes, the only sign of a blow-out fracture is the abrupt inflation of periorbital tissue with air when the patient blows his nose. Standard evaluation of these fractures includes history, physical examination, and radiographs. Some patients benefit from computed tomography (CT), which can be both diagnostic and prognostic. Blow-out fractures do not often produce serious sequelae, and the current trend is toward no treatment. However, it is imperative to rule out any serious injury to the eye itself that would require emergency treatment.

Psychological moods and subjectively perceived behavioral and somatic changes accompanying anabolic-androgenic steroid use.

To assess physiological and psychological states accompanying anabolic-androgenic steroid use, male weight lifters 1) were interviewed regarding their physical training and the patterns and effects of any drug use; 2) completed a written physical and medical history questionnaire, a Profile of Mood States questionnaire, and the Buss-Durkee Hostility Inventory; and 3) were physically examined, including a blood sample and urinalysis. Subjects were divided into current anabolic-androgenic steroid users (N = 12), previous users (N = 14), and nonusers (N = 24). Current and previous users reported the following changes associated with anabolic-androgenic steroid use: increases in enthusiasm, aggression, and irritability; changes in insomnia, muscle size, muscle strength and density; faster recovery from workouts and injuries; and changes in libido. We were unable to confirm these interview and physical and medical history questionnaire responses using standardized and well-accepted psychological inventories. There were no significant differences among groups for any Profile of Moods factor, total mood disturbance, total Buss-Durkee Hostility Inventory score, or any subscale. For current users, there were no significant correlations between either total weekly drug dose or length of time on the current cycle of anabolic-androgenic steroids and any individual scale of the Profile of Mood States, Buss-Durkee Hostility Inventory, Profile of Mood States total mood disturbance, or composite Buss-Durkee Hostility Inventory score. Furthermore, anabolic-androgenic steroid users did not differ in their responses on these inventories from nonusers or from general population norms.(ABSTRACT TRUNCATED AT 250 WORDS)

Anabolic steroids.

Anabolic-androgenic steroid hormones are used by athletes in an attempt to improve performance. Side effects include decreased testosterone and sperm production, acne, balding, and increased aggression. The long-term effects are not known.

Bubble formation within decompressed hen's eggs.

Decompression sickness follows a reduction in ambient pressure and is a result of bubble formation in blood or tissues. The origin of such bubbles is the subject of considerable controversy, and a number of mechanisms have been proposed to account for them. In testing these mechanisms, freshly-laid hen's eggs provide a particularly intriguing model--namely, an intact biological system in which bubbles form readily and many of the proposed processes are excluded.

Marijuana smoking and cold tolerance in man.

Ten men who were marijuana users served as subjects in a study of the effects of marijuana smoking on response to cold. Cold water (28 degrees C for 60 min) and cold air (20 degrees C for 120 min) mediums were utilized with three exposures in each medium. The three exposures followed smoking marijuana, smoking placebo, and a no-smoking control period. Additionally, a breathhold experiment preceded and followed the four smoking periods. Marijuana and placebo smoke were inhaled from a spirometer with each man receiving the smoke of 0.739 g of marijuana and placebo. Smoking marijuana did not greatly modify body heat content, since rectal temperature and most peripheral temperatures were not altered. However, temperatures over voluntary muscles likely to be involved in shivering were elevated. Heat production also greatly increased after marijuana, suggesting that it had stimulated shivering. Marijuana also produced tachycardia and abolished apneic bradycardia. The mechanism of this action is not clear, but some sympathetic involvement is indicated.

Will your practice skills be fit for the 21st century?

The year is 2001-just 3 years from now and the true beginning of the new millennium. It turns out that computers do not practice medicine, physicians still do. Primary care physicians are no longer called "gatekeepers" (which made it sound as if they fixed rusty hinges). They are both numerous and popular because they see the big picture, the whole patient and they don't restrict the flow of patients to specialists. Many take care of entire families.

How to prevent death in weight-cutting wrestlers.

One advantage of wrestling as a varsity sport in high school and college is its weight-class system. Little guys are as valuable as big guys. Ask a wrestler why he chose the sport and he is likely to tell you, "Because I'm too small to play football."

Weight training: strength for everyone.

In prehistoric times, competitive swimmers never lifted weights. The conventional wisdom was that weight training would make their muscles too bulky and would slow them down. This turned out to be untrue. Weight training made swimmers stronger and they moved through the water like trout.

Gluing minor skin wounds.

Super Glue (Pacer Technology, Rancho Cucamonga, California) and Krazy Glue (Elmer's Products, Inc, Columbus, Ohio) revolutionized home improvement. A small drop instantly bonds most things together, including your thumb and index finger.

Activating internal medicine.

Until the past few years, it seemed to me that most physicians who were trained in internal medicine, as I was, were uninterested in anything that moved faster than 3 miles per hour. Not so, now. At the American College of Physicians (ACP) annual meeting last month on San Diego's spectacular harbor, the sessions on sports medicine were jammed. People who were not in their seats 10 minutes early were kept out in the hallway by fire marshals. Why all the interest?

Toward better concussion management.

For assessing brain function in the conscious athlete, neuropsychological testing, the subject of ongoing clinical research, promises to be a quantum leap ahead of traditional neurologic assessments (see the news brief "Baseline Neurologic Testing Grows"). For the past 50 years, we've been forced to use not-so-subtle tests like subtracting serial sevens, which many athletes-and doctors-can't do even in their normal mental state.