Pneumomediastinum following intubation in COVID-19 patients: a case series.

The number of patients requiring tracheal intubation rose dramatically in March and April 2020 with the COVID-19 outbreak. Our thoracic surgery department has seen an increased incidence of severe pneumomediastinum referred for surgical opinion in intubated patients with COVID-19 pneumonitis. Here we present a series of five patients with severe pneumomediastinum requiring decompression therapy over a 7-day period in the current COVID-19 outbreak. We hypothesise that the mechanism for this is the aggressive disease pathophysiology with an increased risk of alveolar damage and tracheobronchial injury, along with the use of larger-bore tracheal tubes and higher ventilation pressures. We present this case series in order to highlight the increased risk of this potentially life-threatening complication among the COVID-19 patient cohort and offer guidance for its management to critical care physicians.

Nucleon Structure Functions from Operator Product Expansion on the Lattice.

Deep-inelastic scattering, in the laboratory and on the lattice, is most instructive for understanding how the nucleon is built from quarks and gluons. The long-term goal is to compute the associated structure functions from first principles. So far this has been limited to model calculations. In this Letter we propose a new method to compute the structure functions directly from the virtual, all-encompassing Compton amplitude, utilizing the operator product expansion. This overcomes issues of renormalization and operator mixing, which so far have hindered lattice calculations of power corrections and higher moments.

A comparison of prediction equations for the estimation of body fat percentage in non-obese and obese older Caucasian adults in the United States.

OBJECTIVES: The predictive capabilities of skinfold regression equations are limited across populations and current equations may not be well suited for the prediction of body fat in older adults or obese Americans. The goal of this study was to compare percent body fat (%BF) predicted by several skinfold regression equations to %BF determined by Dual-Energy X-ray Absorptiometry (DXA) in obese and non-obese Caucasian men and women in the United States over the age of 65 years. DESIGN: A block design was used with two blocks: obesity (non-obese/obese) and gender (male/female). All subjects underwent the same testing procedures in one visit. SETTING: University of Pittsburgh Clinical and Translation Research Center. PARTICIPANTS: Seventy-eight older healthy adults were recruited for participation. MEASUREMENTS: Actual percent body fat was determined from a whole body DXA scan. Estimated percent body fat (%BF) was calculated using skinfold measurements and established regression equations. The predictive accuracy of the regression equations was evaluated by comparing the estimated %BF to the actual %BF measured with DXA using a within subject ANOVA (α=0.05). This was done within subgroups: obese males, obese females, non-obese males and non-obese females. RESULTS: Durnin and Womersly and Jackson and Pollock had reasonably good agreement with DXA in older Caucasian American females and males, respectively. The remaining equations significantly overestimated %BF in older Caucasian American males. Mixed results were found in females with Gause-Nilsson and Jackson and Pollock significantly underestimating %BF, while Visser and Kwok overestimated %BF. CONCLUSION: Numerous factors of a population including age, race, ethnicity, gender and obesity should be considered when selecting a skinfold regression equation to estimate %BF. While Durnin and Womersly and Jackson and Pollock are recommended for predicting %BF in older Caucasian American females and males, respectively, there exists a need to develop accurate regression models that consider obesity, gender, race or ethnicity when predicting %BF in a diverse geriatric American population.

Dynamic postural stability during advancing pregnancy.

UNLABELLED: Pregnant women are at an increased risk of experiencing a fall. Numerous anatomical, physiological, and hormonal alterations occur during pregnancy, but the influence of these factors on dynamic postural stability has not been explored. The purpose of this study was to examine dynamic postural stability in pregnant women during their second and third trimesters as well as in a group of non-pregnant control women. METHODS: Eighty-one women (41 pregnant, 40 controls) participated stood on a force plate that translated anteroposteriorly at small, medium, and large magnitudes. Reaction time and center of pressure (COP) movement during the translations were analyzed. Trimester, perturbation direction, and perturbation magnitude were the independent variables in a mixed-model analysis of variance on each of the following dependent variables: reaction time, initial sway, total sway, and sway velocity. RESULTS: Reaction time to the perturbation was not significantly different between the groups. Initial sway, total sway, and sway velocity were significantly less during the third trimester than during the second trimester and when compared to the non-pregnant controls (P<0.05). No differences were found in any of the measures between the pregnant women in their second trimesters and the control group. CONCLUSION: Alterations in sway responses to perturbations are seen in the third trimester in healthy women with uncomplicated pregnancies. Further study is needed to examine the biomechanical and physiological reasons behind this altered dynamic postural stability.

Dynamic postural stability in pregnant fallers and non-fallers.

OBJECTIVE: To compare dynamic postural stability in pregnant women who have fallen during their pregnancies with those who have not, and with a group of non-pregnant women. DESIGN: The study was both longitudinal and cross-sectional. A cohort of pregnant women were followed through their second and third trimesters. A non-pregnant control group was used for comparison. SETTING: University-based laboratory. POPULATION: A total of 81 women (41 pregnant and 40 controls) participated. Twenty-nine pregnant women completed the protocol. METHODS: Data were collected on the pregnant women in the middle of their second and third trimesters. Pregnant women were surveyed about their daily activities, exercise participation, and fall history. Postural reaction time and centre of pressure (COP) movement data, in response to translational perturbations, were collected using a force plate. A mixed-model analysis of variants (ANOVA) was performed on each of the dependent variables (alpha = 0.05). Chi-square analysis was performed to determine if exercise participation altered the likelihood of a subject experiencing a fall (alpha = 0.05). MAIN OUTCOME MEASURES: Reaction time, initial sway, total sway, and sway velocity. RESULTS: Fifty-two percent of our pregnant subjects experienced a fall. Initial sway response, total sway, and sway velocity were smaller in the pregnant fallers than in the non-fallers and control participants (P < 0.05). Thirty-one of the pregnant subjects participated in regular exercise. Sedentary pregnant women were more likely to experience a fall than those who exercised. CONCLUSIONS: Dynamic balance is altered in pregnant women who have fallen compared with non-fallers and controls. Exercise may play a role in fall prevention in pregnant women.

Gait parameters as predictors of slip severity in younger and older adults.

This study investigated the association between slip severity and pre-slip gait characteristics of younger and older subjects. Sixteen younger and eleven older healthy adults walked onto an unexpectedly slippery surface. Slip severity was categorized as either hazardous or non-hazardous using a 1.0 ms peak slip velocity threshold. The results showed that hazardous slips were associated with greater step lengths (normalized by leg length) (SLR), larger and more rapidly changing foot - floor angles (FFA) at heel strike, and increased cadence across the two subject groups. Older subjects were found to walk with shorter SLR and with smaller and more slowly changing FFA at heel strike compared to younger subjects. However, both younger and older subjects experienced hazardous slips at the same rate. A logistic regression model relating SLR and cadence to slip severity predicted that increased SLR and decreased cadence would result in increased probability of hazardous slip (R2 = 0.45, chi2 = 15.30, p<0.01). A second logistic regression model relating FFA with slip severity predicted that increased FFA would result in increased probability of hazardous slip (R2 = 0.53, chi2 = 16.55, p<0.01). These results suggest that gait characteristics prior to foot contact play an important role in the severity of an ensuing slip. The finding that older adults experienced hazardous slips at the same rate as young adults even though their SLR and FFA are smaller suggests that age is also playing a role in other aspects of postural control that impact slip severity.

Documented prevalence of HIV and hepatitis C infection in patients with penetrating trauma.

BACKGROUND: Trauma patients infected with human immunodeficiency virus (HIV) or hepatitis C (HCV) pose specific problems to health-care workers due to the risk of exposure to these agents in blood and other body fluids. Studies of patients with penetrating trauma in the USA have shown a higher prevalence of HIV and HCV infection than the general population. No studies have examined the prevalence of these infections in Australian trauma patients. METHODS: The medical records of all patients presenting to St Vincent's Hospital, Sydney, from January 1994 to December 1998, with a stab wound to the neck, chest or abdomen, or with a gunshot wound to any anatomical site, were retrospectively reviewed. The number of patients with a history of HIV or HCV infection, or with risk factors for these such as male-to-male sexual intercourse and intravenous drug use, were recorded. RESULTS: The medical records of 148 patients with stab wounds to the neck, chest or abdomen, or with gunshot wounds were examined. Risk factors for HIV or HCV infection were recorded in 31 patients (21%). Two patients (1.3%) had a history of HIV infection and a further eight patients (5.4%) were known to have HCV. CONCLUSIONS: There was a high prevalence of risk factors for HIV and HCV in patients with major penetrating wounds at St Vincent's Hospital. The prevalence of documented HIV and HCV infection was subsequently greater than that expected in the general population, highlighting the risks to health-care workers managing these patients.

Incidence of acquired immune deficiency syndrome (AIDS)-related disorders at laparotomy in patients with AIDS.

BACKGROUND: Patients with acquired immune deficiency syndrome (AIDS) present for surgical management of abdominal conditions that are complications of advanced human immunodeficiency virus (HIV) infection or that are caused by other disease not related to AIDS. This study compared the clinical details and postoperative outcomes of patients with AIDS-related diseases found at laparotomy with those of patients with non-AIDS-related disorders. METHODS: The medical records of 30 consecutive patients with AIDS who underwent laparotomy were examined retrospectively. RESULTS: Fourteen patients had AIDS-related pathologies found at laparotomy, 13 had disease processes that were not AIDS related and three had no abnormal findings at laparotomy. Patients with AIDS-related conditions at laparotomy had lower mean body-weight, serum albumin concentration and CD4 lymphocyte count, and required a longer hospital admission than those who had non-AIDS-related disease. The duration of HIV infection and the number of complications and deaths were similar in the two groups. Complications occurred in 21 patients and there were five deaths (30-day mortality rate 17 per cent). CONCLUSION: AIDS-related pathologies are commonly found at laparotomy in patients with HIV/AIDS. An AIDS-related diagnosis does not confer a greater risk of complication or postoperative death than other conditions.

Management of gunshot wounds at a Sydney teaching hospital.

BACKGROUND: Injuries caused by firearms account for only a small percentage of trauma admissions and deaths in Australia but are frequently the subject of media and public attention. The present study examines the epidemiology and management of firearm injuries presenting to St Vincent's Hospital, which is located at the edge of the central business district of Sydney. METHODS: The medical records of all patients presenting to St Vincent's with a gunshot wound (GSW) from January 1988 to December 1998 were analysed. Additional details were acquired from New South Wales State Coroner's Court reports and media archives, especially major newspapers. RESULTS: Seventy-four patients presented to St Vincent's Hospital with 103 GSW. The age (mean +/- SD) was 31+/-11 years. Sixty-seven patients (91%) were male. Alcohol was identified as a factor in 24 cases (32%) while other drugs were indicated in four cases (5%). Ten patients (14%) had intentionally self-inflicted wounds, seven (9%) had accidental wounds and 57 (77%) had wounds that were caused by crime-related violence. Sixty patients (81%) underwent operation for their injury. Thirty complications were seen in 18 patients (24%). Eleven patients (15%) died. The length of hospital stay (mean +/- SEM) was 18+/-9 days. CONCLUSIONS: The incidence of trauma due to firearms has not increased at St Vincent's hospital in the period 1988-98. Most GSW were inflicted in the setting of criminal violence, with a high proportion due to handguns. Patients were mostly young men, and alcohol or other drugs were frequently involved. Outcomes are comparable to other centres managing large volumes of penetrating trauma.

The effect of increasing clamping forces on endothelial and arterial wall damage: an experimental study in the sheep.

PURPOSE: This study aimed to relate the level of physical force applied to the arterial wall by atraumatic clamps to the degree of endothelial and wall damage. METHODS: Sixteen sheep carotid and femoral arteries were each demarcated into four segments 1 cm apart (total 64 segments). Each segment was clamped for 15 min with a standard angled DeBakey vascular clamp. Four levels of force were generated by closing the clamp at three, four, five and six notches of closure. The extent of endothelial injury was assessed by using a dedicated computer assisted image acquisition program to measure the area stained by Evan's blue dye. The extent of damage to the layers of the arterial wall was analyzed and compared by scanning electron microscopy and light microscopy. RESULTS: For femoral arteries, the area of endothelial injury was considerably less for three notch (3.76 +/- 0.28 newtons) and four notch (5.68 +/- 0.29 newtons) closure compared with that for five notch (6.19 +/- 0.31 newtons) and six notch (6.61 +/- 0.16 Newtons) closure (p = 0.01). For carotid arteries, three notch (5.68 +/- 0.28 newtons) closure caused less damage than did four notch (7.98 +/- 0.29 newtons), five notch (9.17 +/- 0.40 newtons) and six notch (9.57 +/- 0.64 newtons) closure (P = 0.02). Scanning electron microscopy confirmed the extent and depth of arterial injury corresponded directly to the forces generated by the vascular clamps. CONCLUSIONS: The closing forces generated by arterial clamps correlated positively with the extent of artery wall injury. Vascular clamps should be applied at the minimum level of force that will arrest blood flow.

Familial carotid body paragangliomas and sensorineural hearing-loss: a new syndrome.

BACKGROUND: Carotid body paragangliomas are rare tumors that are sometimes familial, the transmission of which is thought to be by genomic imprinting. We have treated a family who exhibited co-inheritance of carotid body paraganglioma and sensorineural hearing-loss, a relationship that has not been previously reported. METHODS: We studied a large Australian family who exhibited familial carotid body paragangliomas, many of whose members also suffered tinnitus or hearing-loss. This relationship was examined by reviewing the medical records of family members with confirmed tumors, carrying out neck ultrasonic scanning or computed tomography on their relatives to look for previously unrecognized tumors, and arranging audiometric testing. This information was used to characterize the type of hearing-loss present in this family and to construct a pedigree for the two traits. RESULTS: The hearing-loss observed in this family was sensorineural in character. Of 15 family members studied over four generations, eight were confirmed positive for both carotid body paraganglioma and sensorineural hearing-loss, two for the tumor only (one of whom did not have his hearing assessed) and one for hearing-loss alone. Four family members were negative for both traits. CONCLUSIONS: The pedigree provides evidence of a previously undescribed association between familial carotid body paraganglioma and sensorineural hearing-loss, a combination that appears to be co-inherited in this family.

Small vessel ischaemia induced by microbead embolization in the sheep hind limb.

BACKGROUND: Peripheral ischaemia may be caused by small vessel disease but there has been no satisfactory experimental model for studying this condition. We have developed a model in which microbeads are embolized to the distal vascular bed of a sheep. This model induces ischaemia proportional to the volume of microbead infusion and allows the pathophysiology and therapy of small vessel occlusion to be studied. METHODS: Gradual reduction of femoral artery blood flow by 50% and 75% in unilateral hind limbs of eight sheep was achieved by slow introduction of latex microbeads (mean size = 400 microns) into the peripheral vascular bed. The other hind limb served as a control. Measurements of blood flow, subcutaneous temperature and arterial and venous blood gases were recorded in both hind limbs after each level of flow reduction. Angiography confirmed small vessel occlusion. Muscle samples were analysed for ultrastructural changes by transmission microscopy. RESULTS: A linear correlation was found between the amount of microbeads infused and the reduction in the blood flow. Significant subcutaneous temperature and venous pO2 changes were observed in the embolized limb at both 50% and 25% flow levels compared to baseline (P < 0.05, ANOVA). Angiography demonstrated abrupt cut-off images of the small vessels. Transmission microscopy showed graded levels of muscle cell damage from ischaemia. CONCLUSIONS: Latex microbead embolization induces reproducible controlled small artery occlusion. The degree of outflow obstruction and the extent of ischaemia can be varied by delivering measured quantities of microbeads. This model should be useful for studying the pathophysiology of ischaemia and for assessing the efficacy of treatment, especially the use of pharmacological agents.

The effect of arterial clamp duration on endothelial injury: an experimental study.

BACKGROUND: Arterial clamp-related endothelial damage was investigated in an animal model to quantify the surface area of endothelial disruption. The influence of the duration of clamp application on this damage was evaluated. METHODS: Four identical angled DeBakey vascular clamps were applied on each of eight carotid arteries in four heparinized adult sheep for durations of 15, 30, 45 and 60 min. The applied clamping forces were measured and kept constant. After the last clamp was removed, the areas of endothelial loss were identified by in vivo staining with Evan's blue dye. The vessels were excised and the blue stained areas measured by computer-assisted analysis. The morphological appearance of the specimens was assessed by scanning electron microscopy. RESULTS: Endothelial damage following clamping for 15 min (10.6 +/- 4.3 mm2) was significantly less than for 30 min (19.0 +/- 4.7 mm2), 45 min (19.8 +/- 4.6 mm2) and 60 min (20.4 +/- 4.9 mm2, P = 0.005), but there were no significant differences between the areas of endothelial loss observed for 30, 45, and 60 min. These results corresponded to the damage seen using scanning electron microscopy, which showed partial disruption of endothelium at 15 min compared to more complete destruction at longer durations. CONCLUSIONS: Evan's blue staining combined with computer-assisted surface area measurement is an accurate method for quantifying endothelial damage. The extent of damage caused by vascular clamps is partly time-dependent, being less for 15 min than for 30 min of clamping, but not significantly increasing for durations greater than 30 min.