Biomedical subjects

Kenneth Davis

Publications and source records attributed to Kenneth Davis.

8 recordsLinked to original sources

PubMed2005

The impact of previous surgical manipulation of subcutaneous sarcoma on oncologic outcome.

UNLABELLED: We prospectively followed 106 consecutive patients referred for surgical treatment of nonmetastatic subcutaneous soft tissue sarcoma to assess whether prior surgical manipulation had an impact on local control and/or disease-free survival. 10 patients had no previous surgical treatment; 11 had only a previous biopsy, 75 had a previous attempted excision, and 10 were referred after the tumor had recurred locally. Histologic grade was inversely associated with overall survival and disease-free survival. Of the 75 patients with previous attempted excision, 22 (29%) had gross residual disease, 27 (36%) had microscopic residual disease, and 26 (35%) had no identifiable residual disease. The 5-year metastasis-free survival was 88%. Local control was obtained in 100% of patients without previous surgical manipulation, 89% of those with previous surgery, and 60% of those who were referred after a local relapse had been recognized. Cox proportional hazards analysis revealed that larger tumor size negatively impacted disease-free survival in those patients who were treated with previous attempted excision. Of those patients with tumors 4 cm or larger and a previous unplanned sarcoma excision, disease-free survival was lower than in those patients referred without previous attempted excision. LEVEL OF EVIDENCE: Prognostic study, Level I-2 (prospective study). See the Guidelines for Authors for a complete description of levels of evidence.

Adolescent↗

PubMed2004

Tedlar bag sampling technique for vertical profiling of carbon dioxide through the atmospheric boundary layer with high precision and accuracy.

Carbon dioxide is the most important greenhouse gas other than water vapor, and its modulation by the biosphere is of fundamental importance to our understanding of global climate change. We have developed a new technique for vertical profiling of CO2 and meteorological parameters through the atmospheric boundary layer and well into the free troposphere. Vertical profiling of CO2 mixing ratios allows estimates of landscape-scale fluxes characteristic of approximately100 km2 of an ecosystem. The method makes use of a powered parachute as a platform and a new Tedlar bag air sampling technique. Air samples are returned to the ground where measurements of CO2 mixing ratios are made with high precision (< or =0.1%) and accuracy (< or =0.1%) using a conventional nondispersive infrared analyzer. Laboratory studies are described that characterize the accuracy and precision of the bag sampling technique and that measure the diffusion coefficient of CO2 through the Tedlar bag wall. The technique has been applied in field studies in the proximity of two AmeriFlux sites, and results are compared with tower measurements of CO2.

Altitude↗

PubMed2004

Biophysical characterization of the catalytic domain of guanine nucleotide exchange factor BopE from Burkholderia pseudomallei.

BopE is a type III secreted protein from Burkholderia pseudomallei, the aetiological agent of melioidosis. Like its Salmonella homologues SopE and SopE2, BopE is a guanine nucleotide exchange factor for Rho GTPases. It is thought that, in order to be secreted by the type III system, proteins must be unfolded or only partially folded. As part of a study of B. pseudomallei virulence proteins, we have expressed, purified and characterized the catalytic domain of BopE (amino acids 78-261). Analytical ultracentrifugation experiments in conjunction with analytical size exclusion chromatography show that BopE(78-261) is monomeric in aqueous solution. CD spectroscopy indicates that the protein is predominantly alpha-helical, with predicted secondary structure composition of 59% alpha-helix and 7% beta-strand. NMR spectroscopy confirms that BopE(78-261) adopts a single, stable conformation. In differential scanning calorimetry experiments, thermal denaturation of BopE(78-261) (T(m) 52 degrees C) is reversible. Also, the secondary structure composition of BopE(78-261) changes little over a range of pH values from 3.5 to 10.5. BopE may therefore fold spontaneously to a functional form upon secretion into the host cell cytoplasm, and retains a native or native-like fold in varied environments. These properties are likely to be advantageous for a secreted bacterial effector protein.

Amino Acid Sequence↗

PubMed2004

Low-dose inhaled nitric oxide in patients with acute lung injury: a randomized controlled trial.

CONTEXT: Inhaled nitric oxide has been shown to improve oxygenation in acute lung injury. OBJECTIVE: To evaluate the clinical efficacy of low-dose (5-ppm) inhaled nitric oxide in patients with acute lung injury. DESIGN AND SETTING: Multicenter, randomized, placebo-controlled study, with blinding of patients, caregivers, data collectors, assessors of outcomes, and data analysts (triple blind), conducted in the intensive care units of 46 hospitals in the United States. Patients were enrolled between March 1996 and September 1999. PATIENTS: Patients (n = 385) with moderately severe acute lung injury, a modification of the American-European Consensus Conference definition of acute respiratory distress syndrome (ARDS) using a ratio of PaO2 to FiO2 of < or =250, were enrolled if the onset was within 72 hours of randomization, sepsis was not the cause of the lung injury, and the patient had no significant nonpulmonary organ system dysfunction at randomization. INTERVENTIONS: Patients were randomly assigned to placebo (nitrogen gas) or inhaled nitric oxide at 5 ppm until 28 days, discontinuation of assisted breathing, or death. MAIN OUTCOME MEASURES: The primary end point was days alive and off assisted breathing. Secondary outcomes included mortality, days alive and meeting oxygenation criteria for extubation, and days patients were alive following a successful unassisted ventilation test. RESULTS: An intent-to-treat analysis revealed that inhaled nitric oxide at 5 ppm did not increase the number of days patients were alive and off assisted breathing (mean [SD], 10.6 [9.8] days in the placebo group and 10.7 [9.7] days in the inhaled nitric oxide group; P =.97; difference, -0.1 day [95% confidence interval, -2.0 to 1.9 days]). This lack of effect on clinical outcomes was seen despite a statistically significant increase in PaO2 that resolved by 48 hours. Mortality was similar between groups (20% placebo vs 23% nitric oxide; P =.54). Days patients were alive following a successful 2-hour unassisted ventilation trial were a mean (SD) of 11.9 (9.9) for placebo and 11.4 (9.8) for nitric oxide patients (P =.54). Days alive and meeting criteria for extubation were also similar: 17.0 placebo vs 16.7 nitric oxide (P =.89). CONCLUSION: Inhaled nitric oxide at a dose of 5 ppm in patients with acute lung injury not due to sepsis and without evidence of nonpulmonary organ system dysfunction results in short-term oxygenation improvements but has no substantial impact on the duration of ventilatory support or mortality.

Administration, Inhalation↗

PubMed2003

Caudate and putamen volumes in good and poor outcome patients with schizophrenia.

Magnetic resonance images of 37 patients with schizophrenia and 37 age- and sex-matched volunteers were acquired. The caudate nucleus and putamen were traced on axial slices from the most superior extent of the caudate to the most inferior point where the caudate and putamen merge. Two subtypes of schizophrenia were compared, the Kraepelinian subtype (n=13), characterized by an unremitting and severe course, and the non-Kraepelinian subtype (n=24), characterized by a remitting course and some periods of self-care. Patients with good outcome schizophrenia had larger relative mean putamen size (0.0129) than poor outcome patients (0.0123) or normal controls (0.0121), but not caudate size. This enlargement was most marked for the dorsal putamen and right hemisphere. Striatal size was not related to whether patients were currently being treated with atypical or typical neuroleptics or whether they had been predominantly treated with typical or atypical neuroleptics over the past 3 years. This suggests the possibility that the expansion of putamen size may be a physiological correlate of neuroleptic responsiveness or that small putamen size at disease onset may be a predictor of outcome.

Adult↗

PubMed2003

Influence of low tidal volumes on gas exchange in acute respiratory distress syndrome and the role of recruitment maneuvers.

UNLABELLED: BACKGROUND Use of a low tidal volume (V(T)) strategy in the treatment of acute respiratory distress syndrome can lead to a decrease in oxygenation. This study evaluated the safety and efficacy of a recruitment maneuver (RM) in this setting. METHODS: Twelve patients with acute respiratory distress syndrome were studied within 48 hours of diagnosis. Baseline gas exchange, hemodynamics, and respiratory mechanics were determined and patients were placed on a V(T) of 6 mL/kg. Measurements were repeated and an RM of 30 cm H20 for 40 seconds was performed. Measurements were repeated at 30 minutes and 2 hours post-RM. RESULTS: Decreasing V(T) resulted in a decrease in arterial oxygenation (from 91 +/- 9 mm Hg to 75 +/- 9 mm Hg, p < 0.01), an increase in shunt (from 19 +/- 3.7% to 23 +/- 5%, p < 0.01), and a decrease in lung compliance (from 37 mL/cm H2O to 33 mL/cm H2O, < 0.05). At 30 minutes post-RM, oxygenation improved to 99 +/- 16 mm Hg, shunt decreased to 17 +/- 3%, and lung compliance improved to 39 mL/cm H2O (p < 0.05). Two hours later, oxygenation fell (86 +/- 12 mm Hg), shunt increased (20 +/- 3%), and compliance diminished (36 mL/cm H2O). There were no hemodynamic or barotraumatic complications. CONCLUSION: An RM transiently improves gas exchange during low V(T)ventilation. RMs are well tolerated and no hemodynamic consequences were seen.

Accidents, Traffic↗

PubMed2002

Pelvic fracture in the elderly is associated with increased mortality.

OBJECTIVE: The elderly population is currently the fastest growing sector in America. The purpose of this study was to examine the age-related outcome in patients after blunt pelvic injury. METHODS: All patients admitted with a pelvic fracture during a 5-year period were identified from the trauma registry. Data retrieval included: demographics, shock (BP < 90 mm Hg) on admission, injury severity score (ISS), abbreviated injury score (AIS) for head, chest, and abdomen, intensive care unit (ICU) length of stay (LOS), hospital LOS, and mortality. All pelvic fracture patterns were classified. Patient data were then stratified by age for comparison: young (< 55 years) and elderly (> or = 55 years). Statistical analysis was performed using the Student t test, Wilcoxon rank-sum test, multiple logistic regression analysis, and chi-square test with significance set at P <.05. RESULTS: Three hundred five patients sustained a pelvic fracture (young [n = 248, 81.3%]; elderly [n = 57, 18.7%]). The only predictor of mortality was age. The 2 groups differed by gender (elderly = 54.4% females; young = 62.5% males) but not frequency of shock, ISS, or AIS for head, chest, and abdomen. Motor vehicle collision was the most common mechanism of injury (elderly = 68.4%; young = 73.8%). Lateral compression was the most common fracture pattern in both groups (elderly = 54.4%; young = 45.6%). There was no difference in transfusion (elderly = 2.5 +/- 0.7 vs young = 2.0 +/- 0.3; ns) but the elderly group was more frequently admitted to the ICU (elderly = 61.4% vs young = 46.8%; P =.065). Significantly more of the elderly group had a diagnosis of cardiovascular disease (43.9% vs 10.1%, P <.001) and diabetes mellitus (10.5% vs 2.4%, P <.014). Mortality was significantly greater in the elderly group (12.3% vs 2.3%). CONCLUSION: Elderly patients sustaining a pelvic fracture were more likely to have a lateral compression fracture pattern, longer hospital LOS, and die despite aggressive resuscitation. This difference in outcome should help trauma surgeons recognize that the elderly patient sustaining a pelvic fracture is at increased risk of death.

Adult↗

PubMed2002

Closed-loop mechanical ventilation.

Closed-loop mechanical ventilation encompasses a plethora of techniques, ranging from the very simple to the relatively complex. In the simplest form, closed-loop ventilation is the control of one output variable of the mechanical ventilator based on the measurement of an input variable. An example would be pressure support ventilation, in which flow (output) is constantly changing to maintain pressure (input) constant throughout inspiration. More complex forms of closed-loop ventilation involve measurement of multiple inputs (eg, compliance, oxygen saturation, respiratory rate) to control multiple outputs (eg, ventilator frequency, airway pressure, tidal volume). The latter type of control more closely mimics the ventilatory control and response of human physiology. This review discusses both currently available closed-loop ventilation techniques and those only available outside the United States, along with some cutting-edge techniques that have only limited use. The operation, theoretical advantages, and limitations of each technique are reviewed. When available, the literature supporting or refuting each technique will be reviewed, but, unfortunately, little has been published on certain techniques.

Algorithms↗