Measurement of polarization observables T, P, and H in π0 and η photoproduction off quasi-free nucleons.

The target asymmetry T, recoil asymmetry P, and beam-target double polarization observable H were determined in exclusive π0 and η photoproduction off quasi-free protons and, for the first time, off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the γp→π0p and γp→ηp reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the ηn system at W=1.68GeV. A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the S11(1535) and S11(1650) resonances within the S11-partial wave.

A randomized, prospective evaluation of noninvasive ventilation for acute respiratory failure.

We compared noninvasive positive-pressure ventilation (NPPV), using bilevel positive airway pressure, with usual medical care (UMC) in the therapy of patients with acute respiratory failure (ARF) in a prospective, randomized trial. Patients were subgrouped according to the disease leading to ARF (chronic obstructive pulmonary disease [COPD], a non-COPD-related pulmonary process, neuromuscular disease, and status postextubation), and were then randomized to NPPV or UMC. Thirty-two patients were evaluated in the NPPV group and 29 in the UMC group. The rate of endotracheal intubation (ETI) was significantly lower in the NPPV than in the UMC group (6.38 intubations versus 21.25 intubations per 100 ICU days, p = 0.002). Mortality rates in the intensive care unit (ICU) were similar for the two treatment groups (2.39 deaths versus 4.27 deaths per 100 ICU days, p = 0.21, NPPV versus UMC, respectively). Patients with hypoxemic ARF in the NPPV group had a significantly lower ETI rate than those in the UMC group (7.46 intubations versus 22.64 intubations per 100 ICU days, p = 0.026); a similar trend was noted for patients with hypercapnic ARF (5.41 intubations versus 18.52 intubations per 100 ICU days, p = 0.064, NPPV versus UMC, respectively). Patients with ARF in the non-COPD category had a lower rate of ETI with NPPV than with UMC (8.45 intubations versus 30.30 intubations per 100 ICU days, p = 0.01). Although the rate of ETI was lower among COPD patients receiving NPPV, this trend did not reach statistical significance (5.26 intubations versus 15.63 intubations per 100 ICU days, p = 0.12, NPPV versus UMC, respectively). In conclusion, NPPV with bilevel positive airway pressure reduces the rate of ETI in patients with ARF of various etiologies.

Thrombolytic therapy of pulmonary embolism: a comprehensive review of current evidence.

Pulmonary embolism (PE) is a common disorder that is accompanied by significant morbidity and mortality. Although anticoagulation is the standard treatment for PE, thrombolytic therapy, with its ability to produce rapid clot lysis, has long been considered an attractive alternative. Although many studies have been performed over the past three decades, however, the indications for the use of thrombolytic agents in patients with PE remain controversial. In this article, we review the medical literature and provide evidence-based guidelines for the use of thrombolytic therapy. We will also discuss the practical aspects of PE thrombolysis.

A 3-year multi-institutional experience with the liposhaver.

OBJECTIVE: To report a 3-year multi-institutional clinical experience with the liposhaver in facial plastic surgery. DESIGN: Nonrandomized, nonblinded, multi-institutional evaluation of the liposhaver in a clinical setting. INTERVENTIONS: Seventy-two patients who presented for facial plastic surgical procedures underwent surgery with the liposhaver. Seventy-six liposhaving procedures and 74 concomitant procedures were performed. Standardized preoperative and postoperative photographs were obtained. OUTCOME MEASURE: Subjective evaluation by the surgeons who performed the procedures. RESULTS: The liposhaver was used successfully in all cases. The fat was cleanly shaved and the contour results were even, without dimpling or significant asymmetry. Operative time was comparable to that of conventional liposuction. There were no cases of facial nerve injury and no evidence of increased bleeding intraoperatively. Two male patients had small postoperative hematomas in the immediate postoperative period that were successfully treated with conservative measures. An additional patient developed a small hematoma on postoperative day 5 that was effectively treated with needle aspiration and a pressure dressing. CONCLUSION: This 3-year multi-institutional report suggests that the liposhaver continues to offer a precise alternative to conventional liposuction.

The accuracy of pneumotachograph measurements during mechanical ventilation.

We hypothesized that differences between the conditions under which a pneumotachograph (PT) is calibrated and those during data collection might lead to large errors in measured flow and volume during mechanical ventilation. A Fleisch No. 1 and Fleisch No. 2 and a screen PT were connected to "ideal" tubing configurations that optimized flow characteristics, and to ventilator tubing with and without a Y-connector and endotracheal (ET) tube. Each PT was also evaluated after water had accumulated in its resistive element. Air was passed through each PT configuration, using both a continuous and a pulsatile flow pattern, and collected in a water-seal spirometer. "Measured" and "true" flow and volume were determined from the PT and the spirometer, respectively. Measured flow and volume were falsely low when the PT was adapted to ventilator tubing. Addition of a Y-connector and ET tube caused measured flow and volume to increase, and, in some cases the relationship between measured and true flow became nonlinear. Water accumulation in the PT did not lead to measurement errors. We conclude that when a PT is used during mechanical ventilation, tubing geometry must be identical during calibration and data collection, and that calibration should be performed over the entire range of relevant flows.

Patient work of breathing during pressure support and volume-cycled mechanical ventilation.

A computer-assisted technique based on the equation of motion of the respiratory system was used to measure inspiratory work of breathing in 11 patients during pressure support ventilation (PSV) and assisted, volume-cycled mechanical ventilation (AMV). During both modes of ventilation, patient work of breathing was calculated as the difference between the total work performed on the respiratory system (as predicted by the equation of motion) and the work performed by the ventilator. Patient work of breathing during AMV was also calculated as the difference between ventilator work measured during assisted and controlled mechanical breaths. By either method of work calculation, patient work of breathing during AMV was less than previously reported. In addition, when equal tidal volumes were delivered, there was no significant difference between the work performed by the patient during AMV and PSV. Patient work of breathing during PSV was found, however, to vary inversely with the level of pressure support. We conclude that: (1) patient work of breathing during AMV and PSV can be calculated using a computer-assisted technique based on the equation of motion of the respiratory system, and (2) depending on the amount of pressure support provided, patient work of breathing during PSV may be greater than, less than, or equal to the work performed during AMV.

A colorimetric assay for measuring cell-free and cell-bound cholesterol oxidase.

Cholesterol oxidase (cholesterol:oxygen oxidoreductase, EC 1.1.3.6) catalyzes the conversion of sterol delta 5-3 beta-alcohol to the corresponding delta 4-3-ketone with the reduction of oxygen to hydrogen peroxide. Rhodococcus species GK 1, a soil isolated microbe, produces an extracellular and a membrane-bound cholesterol oxidase; the latter is bound to the outer surface of the microbial cell membrane. A simple and sensitive assay is described to measure the two enzyme types; no enzyme extraction is needed for measuring the membrane-bound cholesterol oxidase. In this assay, hydrogen peroxide is reduced by the chromogen 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) in the presence of horseradish peroxidase, and the increased absorbance is followed continuously at 600 nm (epsilon m = 1.82 x 10(4) M-1.cm-1 at pH 7.0 and 30 degrees C). The standardized assay medium contained 46.9 mM sodium-potassium phosphate buffer pH 7.0, 0.16% Triton X-100, 312.5 microM ABTS, 50 micrograms peroxidase (12.5 units at 25 degrees C), 6.25% isopropanol, 306.3 microM cholesterol or other sterols (kept in solution with isopropanol), and cholesterol oxidase. Oxidation of one molecule of cholesterol by cholesterol oxidase gives one molecule of hydrogen peroxide which reacts with two molecules of ABTS. The method is reproducible and the results correlate well with those obtained by measuring the absorbance of delta 4-cholest-3-one at 240 nm (epsilon m = 1.40 x 10(4) M-1.cm-1 at pH 7.0 and 30 degrees C) and by the method of Allain et al. (Clin. Chem. 20, 470-475, 1974).(ABSTRACT TRUNCATED AT 250 WORDS)

Ozone-induced changes in pulmonary function and bronchial responsiveness in asthmatics.

To compare the responses of asthmatic and normal subjects to high effective doses of ozone, nine asthmatic and nine normal subjects underwent two randomly assigned 2-h exposures to filtered, purified air and 0.4 ppm ozone with alternating 15-min periods of rest and exercise on a cycle ergometer (minute ventilation = 30 l.min-1.m-2). Before and after each exposure, pulmonary function and bronchial responsiveness to methacholine were measured and symptoms were recorded. Ozone exposure was associated with a statistically significant decrease in forced vital capacity (FVC), forced expired volume in 1 s (FEV1), percent FEV1 (FEV1%), and forced expired flow at 25-75% FVC (FEF25-75) in both normal and asthmatic subjects. However, comparing the response of asthmatic and normal subjects to ozone revealed a significantly greater percent decrease in FEV1, FEV1%, and FEF25-75 in the asthmatic subjects. The effect of ozone on FVC and symptom scores did not differ between the two groups. In both normal and asthmatic subjects, exposure to ozone was accompanied by a significant increase in bronchial responsiveness. We conclude that exposure to a high effective ozone dose produces 1) increased bronchial responsiveness in both normal and asthmatic subjects, 2) greater airways obstruction in asthmatic than in normal subjects, and 3) similar symptoms and changes in lung volumes in the two groups.

The physiology of spontaneous and mechanical ventilation.

This article provides both an overview of normal ventilation and gas exchange during spontaneous breathing and a review of the alterations of pulmonary physiology that occur with the institution of mechanical ventilation.

Plasma hypoxanthine and exercise.

During exercise, ATP is converted to ADP and AMP to supply energy for muscular contraction. It is then regenerated via various pathways of intermediary metabolism. However, with high levels of exercise, net ATP degradation in muscle occurs. In exercise and other clinical situations, adenine nucleotide degradation leads to an accumulation of degradative purine products including hypoxanthine. In an effort to monitor events of energy metabolism, we examined plasma hypoxanthine levels at various exercise intensities. Peak plasma hypoxanthine levels after maximal exercise (18.9 +/- 2.6 microM, mean +/- SEM) were significantly greater than resting levels (1.1 +/- 0.1 microM; p less than 0.001). Hypoxanthine levels after steady state exercise at 52, 76, and 97% of ventilatory threshold did not exceed resting levels. However, plasma hypoxanthine rose significantly after exercise at 124% of ventilatory threshold (6.3 +/- 1.0 microM; p less than 0.01) and at 152% of ventilatory threshold (17.0 +/- 3.6 microM; p less than 0.001). Exercise at subventilatory threshold intensity (74% of ventilatory threshold) for a prolonged time period, such that total work equaled that performed at 152% of ventilatory threshold, did not elevate hypoxanthine levels (0.46 +/- 0.1 microM) above resting values. We conclude that elevation of plasma hypoxanthine levels occur during exercise at intensities that exceed the ventilatory threshold and indicate that net adenine nucleotide degradation has occurred.