Tension pneumothorax

The diagnosis of tension pneumothorax has typically been taught as the presence of hemodynamic compromise with an expanding intrapleural space air mass. This may occur quickly or gradually, depending on the degree of lung injury and respiratory state of the patient. Experimentally, tension pneumothorax is a multifactorial event that manifests a state of central hypoxemia, compensatory mechanisms, and mechanical compression on intrathoracic structures. Studies using animal models suggest that over hypotension is a delayed finding that immediately precedes cardiorespiratory collapse. Recognition of early signs and symptoms associated with tension pneumothorax, e.g., progressive hypoxemia, tachycardia, and respiratory distress, can alert medical personnel to the need for rapid decompression before physiologic decompensation.

The lack of association between hypertension and hypothyroidism in a primary care setting

This work examines the association between hypertension and hypothyroidism in geriatric patients seen at a primary care medical office. One hundred and twenty-two geriatric patients with elevated thyroid stimulating hormone (TSH) levels were selected for the study. An equal number of euthyroid geriatric individuals were selected from the same clinic for comparison. We found no differences in mean diastolic blood pressure (DBP) in the euthyroid and hypothyroid groups (80.1 mm Hg vs 78.9 mm Hg, P = 0.25). Additionally, there was no significant association between having hypertension (defined as having an elevated DBP or receiving treatment for hypertension at the time of the index visit) and level of TSH (P = 0.33). Logistic regression did show that race, gender, body mass index and renal function were significantly associated with the presence of hypertension. Lastly, there was not a significant association between level of TSH and DBP as determined by regression (P = 0.97). In conclusion, in this population of geriatric patients we did not find hypertension to be associated with the presence of hypothyroidism.

Patient-physician E-mail communication

A significant number of Oklahomans are using computers and have e-mail access either at home or at work. Consecutive patients seen by 23 family physician members of the Oklahoma Physicians Research/Resource Network (OKPRN) were queried regarding their use of computers and access to e-mail. The numbers are higher in urban and suburban areas than in medium and smaller towns and rural areas. Of those who have e-mail access now or are planning to get it within six months, a substantial majority would like to use this medium to interact with their family physician. Potential uses for e-mail technology and problems to be overcome are discussed.

Domestic violence in the emergency department: how do women prefer to disclose and discuss the issues?

The purpose of this study was to survey women presenting to the emergency department (ED) and determine from them how best to identify and discuss issues of domestic violence (DV). An anonymous 10-question survey was given to ambulatory females presenting to the ED. It was conducted at two affiliated university hospital EDs, one an urban trauma center (ED 1) and the other an ED in an affluent suburban setting (ED 2). Two hundred forty-three women responded (73% response), 153 (63%) from ED 1 and 90 (37%) from ED 2. There were 21 women (9%) currently being abused, and 109 (45%) were past victims. Of all victims, 40 (36%) would only divulge DV if asked directly, 28 (25%) would volunteer this information without being asked, and 12 (11%) would not report DV even if asked. Of women who would reveal DV only if asked directly, 52 (45%) felt very comfortable disclosing this to an ED physician, although only 27 (24%) would reveal DV at a triage encounter. Of past or current victims, 43 (39%) would not disclose DV if they knew that ED personnel were required to report it. In conclusion, the ED is an appropriate setting to discuss DV issues. A significant percentage of women will disclose DV only if asked directly about it. Many victims of DV feel very comfortable discussing DV with ED physicians and nurses, although they may be less likely to reveal DV incidents at a triage encounter. Mandatory reporting laws may be an impediment to identifying cases of abuse.

The pathophysiology of tension pneumothorax in ventilated swine

It remains unclear as to whether the cardiovascular collapse observed in tension pneumothorax (TP) is strictly a mechanical pressure-related phenomenon or secondary to hypoxemia. This study describes the pathophysiologic changes associated with a surgically induced progressive TP in a ventilated swine model. With a balloon occlusion catheter surgically placed into the pleural space, progressive volumes of pneumothorax were created in six anesthetized pigs on positive-pressure ventilation. Air was introduced into the right hemithorax in 100-mL increments every 4-5 min, with measurements of heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), mean intrapleural pressure (MIP), oxygen saturation (O2%), arterial blood gas (ABG), and cardiac output (C.O.). With the induced progressive TP, results showed that O2% measures decreased immediately and continued to decline throughout the experiment to levels below 50% prior to cardiovascular collapse. The MAP and HR remained relatively stable until approximately 57% total lung capacity progressive TP (600 mL) was reached. At this point, a significant decline in MAP and increase in HR was noted, indicating tension physiology. The C.O. showed a small but significant decrease after 200 mL of air was injected, with a progressive decline after this point. At > 97% total lung capacity TP, lethal cardiovascular collapse occurred in all animals and was associated with an abrupt drop in C.O., HR, and MAP. There was a concurrent equalization of MIP with CVP at the point of collapse. Arterial blood gas measures correlated with O2% trends during the trials. We conclude that the findings of this study support the alternative hypothesis that significant hypoxemia occurs early and precedes hypotension in ventilated animals with TP. Occlusive mechanical compression, suggested by equalization of MIP and CVP, is probably a late event.

OAFP starts practice-based resource/research network

The Oklahoma Academy of Family Physicians, in collaboration with the University of Oklahoma Health Sciences Center, has established a primary care practice-based research network with thirteen family practice offices currently participating. The practices are connected to each other and to the Health Sciences Center campuses in Oklahoma City and Tulsa by electronic mail and have begun their first research project involving the diagnosis and treatment of brown recluse spider bites in the primary care setting.

Stab wound to the chest with acute pericardial tamponade

A 21-year-old male presented to the trauma unit after he was stabbed once with a knife in the left anterior chest. The patient was awake and combative, very intoxicated, with a systolic blood pressure of 90 mmHg by palpation and a heart rate of 110 beats per min. Physical examination revealed distended neck veins, a single 1.5 cm stab wound to the left parasternal area at the third ICS (noted by clip on x-ray, Fig. 1), poorly auscultated heart sounds, and palpable femoral pulses that went away with inspiration. Chest radiograph (Fig. 1) showed a "pear-shaped" cardiac silhouette, though not markedly enlarged, and a significant left hemothorax. A diagnosis of acute pericardial tamponade was made, and the patient was taken immediately to the operating room for thoracotomy and successful repair of a stab wound of the right ventricle. Figure 2 (courtesy of Richard Wolfe, MD, Massachusetts General Hospital, Boston, MA) presents an example of an echocardiogram depicting a pericardial effusion. Pericardial fluid is imaged as a black (hypoechoic) crescent area separating the apex of the heart from the pericardium, seen as a white ring (arrow) at the inferior aspect of the scan. Tamponade is defined sonographically as the presence of both pericardial effusion (PE) and diastolic collapse of the right ventricle. Figure 3 (courtesy of Michael H. Picard, MD, of Harvard Medical School, Boston, MA) demonstrates the collapse of the right ventricular outflow track (RVOT) and its position relative to the left ventricle (LV), the left atrium (LA), and the aortic valve (AV).

Airbag safety: deployment in an automobile crash with a fall from height

Airbag restraint systems have demonstrated a significant reduction in mortality in motor vehicle crashes (MVCs). While airbag devices are effective primarily in frontal or near-frontal impacts, little is known about the efficacy of these devices in nonfrontal types of collisions. Moreover, there are reports of injuries specific to airbag deployment that have led some investigators to question the benefit of such devices. This article reports a rollover MVC with a considerable fall from height in which lap/shoulder belts were used in addition to airbag deployment that resulted in protection of the driver from injury. The outcome of this case continues to support the combination of belt and airbag restraint systems as the most effective occupant protection in both frontal and nonfrontal types of MVCs.

Ciguatera fish poisoning. A southern California epidemic

Ciguatera fish poisoning results from the bioconcentration of a variety of toxins produced by marine dinoflagellates. Signs and symptoms vary widely, but it usually presents as gastrointestinal and neurologic complaints beginning shortly after the ingestion of fish containing the toxins. Symptoms may persist for months and sometimes even years. Although cases have been reported throughout the United States, epidemics are most common along tropical and subtropical coasts and usually involve the ingestion of large carnivorous fish. We review the literature and report the first epidemic of 25 cases of ciguatera fish poisoning presenting to area hospitals in Southern California that were successfully tracked by the Department of Health Services and isolated to fish caught off the coast of Baja California, Mexico.

Prehospital needle aspiration and tube thoracostomy in trauma victims: a six-year experience with aeromedical crews

The use of prehospital tube thoracostomy (TT) for the treatment of suspected tension pneumothorax (TPtx) in trauma patients is controversial. A study is presented that reviews a 6-year experience with the use of needle catheter aspiration (NA) and chest tubes performed in the field by air medical personnel. Prehospital flight charts and hospital records from 207 trauma patients who underwent one or both of these procedures in the field were retrospectively reviewed. The clinical indications used to determine treatment are presented for both procedures. Improvement in clinical status of patients observed by flight personnel were similar for both treatment groups (54% for NA, 61% for TT). Thirty-two (38%) of the TT patients had failed NA attempts prior to chest tube placement. Average time on scene (T.O.S.) was significantly greater for the TT group (25.7 min versus 20.3 min for NA group). Fewer patients were pronounced dead on arrival (D.O.A.) with TT treatment compared to NA alone (7% versus 19%, respectively). Injury severity scores, number of hospital complications, length of stay (L.O.S.), and total hospital costs were not different between the two groups. There were no cases of lung damage or empyema formation associated with prehospital TT treatment. Overall mortality was similar for both groups. From these data, we conclude that NA is a relatively rapid intervention in the treatment of suspected TPtx in the prehospital setting; however, TT is an effective adjunct for definitive care without increasing morbidity or mortality. A better understanding of the physiology of intrapleural air masses is needed to determine the most effective decompression requirements prior to aeromedical transport.

Effect of reduced hemoglobin concentration on leg oxygen uptake during maximal exercise in humans

Maximum oxygen uptake (VO2max) is affected by hemoglobin concentration ([Hb]). Whether this is simply due to altered convection of O2 into the muscle microcirculation or also to [Hb]-dependent diffusive transport of O2 out of the muscle capillary is unknown in humans. To examine this, seven healthy volunteers performed four maximal cycle exercise bouts at sea level immediately after 8 wk at altitude (3,801 m, barometric pressure 485 Torr), a sojourn designed to increase [Hb]. The first two bouts were at ambient [Hb] of 15.9 +/- 0.7 g/100 ml breathing 21 or 12% O2 in random order. [Hb] was then decreased to a prealtitude level of 13.8 +/- 0.6 g/100 ml by venesection and isovolemic replacement with 5% albumin in 0.9% saline, and the exercise bouts were repeated. At whole body VO2max, PO2, PCO2, pH, and O2 saturation were measured in radial arterial and femoral venous blood. Femoral venous thermodilution blood flow was determined for calculation of leg VO2. Mean muscle capillary PO2 and muscle diffusing capacity (DO2) were computed by Bohr integration between measured arterial and femoral venous PO2. Averaged over both fractional concentrations of inspired O2, leg VO2 at maximum decreased by 17.7 +/- 4.3% as [Hb] was lowered while leg O2 delivery decreased by 17.5 +/- 2.6% and DO2 decreased by 10.7 +/- 2.7% (all P < 0.05). The relative contributions of decreases in leg O2 delivery and DO2 to the decrease in VO2max were computed to be 64 and 36%, respectively. These findings suggest that [Hb] is an important determinant of O2 diffusion rates into working muscle in humans. Possible mechanisms include 1) dependence of DO2 on intracapillary red blood cell spacing, 2) changes in the total rate of dissociation of O2 from [Hb], and 3) increased red blood cell flow heterogeneity as [Hb] is reduced.

Generalist courses in US medical schools and their relationship to career choice

We conducted a survey of required first-year generalist courses offered by US medical schools during 1980, 1985, and 1990 to see if significant growth had occurred in this curricular area and to determine if the presence of these courses was associated with an increase in the percent of graduates selecting family practice as a career option. During the 1980s, only two types of generalist courses were offered by more than 50% of US medical schools, clinical experience and human behavior/psychiatry courses, with significant growth occurring in only two types of generalist courses, ethics and medical humanities courses. The presence of a required clinical experience course in 1985 was associated with a 2% increase in the number of graduates selecting family practice as a career option in 1988.

Hydroxylysine excretion does not indicate collagen damage with downhill running in young men

The purpose of this study was to determine whether urinary excretion of hydroxylysine (HO-Lys) is increased following prolonged, predominantly downhill running. Such an increase would be evidence of exercise-induced collagen damage. Each of ten young men performed a treadmill running test to determine VO2peak (an approximation of VO2max) followed by 60 min of intermittent running on -10% slope. Total urine excreted from 48 h pre-exercise to 96h post-exercise was collected in 8-h samples for measurement of HO-Lys. In addition, both urinary 3-methylhistidine (3-MeHis) excretion and serum creatine kinase (SCK) activity were measured as indicators of muscle tissue damage. In no sampling period was post-exercise HO-Lys excretion altered compared with pre-exercise (e.g., pre-exercise: 82.2 +/- 9.6 mumol.24 h-1, mean +/- SE; 51.0 +/- 3.7 mumol.g creatinine-1; post-exercise: 72.9 +/- 2.0 mumol.24 h-1; 47.0 +/- 1.5 mumol.g creatinine-1). SCK activity was increased (346%) 24 h post-exercise, but not immediately, 48 h, or 72 h post-exercise. 3-MeHis excretion was not altered following exercise. There were no strong associations between HO-Lys excretion and either of the markers of muscle damage. We concluded that no evidence of exercise-induced collagen damage was provided by urinary HO-Lys excretion.