Effects of continuous positive airway pressure in acute asthma

We studied flow changes, airway pressures, breathing patterns and subjective sensation during tidal breathing on continuous positive airway pressure (CPAP) in 21 acutely ill asthmatic patients and 19 controls. The measurements obtained at various levels of CPAP were compared to the value at zero end-expiratory pressure. The fractional inspiratory time (TI/TTOT) was significantly reduced in both the patients and the control group (p less than 0.01). Patients noticed the best sensation of comfort at CPAP of 5.3 +/- (SD) 2.8 and the control group at 1.6 +/- 2.5. We noted a reduction in peak tidal expiratory flow and an increase in late-phase expiratory flow during tidal breathing in both groups although these changes were not statistically significant. There was improvement in sensation of comfort during low to medium levels of CPAP in acutely ill asthmatics. We conclude that low to medium levels of CPAP may be beneficial in acute asthma by assisting inspiratory muscles. As CPAP is increased, the beneficial effects of increased end-expiratory flow rate may be offset by the reduction in peak tidal expiratory flow rates.     

Calculating rabies virus neutralizing antibodies titres by flow cytometry

The determination of the rabies neutralizing antibody (VNA) response after immunization against rabies is an acceptable index of the efficacy of a vaccine and a successful treatment. Several tests have been developed in attempt to improve the assessment of VNA, from mice inoculation to cell-culture fluorescence inhibition tests. All of them, however, present special difficulties in terms of reading or accuracy. The present study describes a neutralization test performed in cell-culture appraised by flow cytometry (FC). Serial dilutions of the serum samples were mixed in vitro with rabies virus before the addition of BHK-21 cells. After 24h-incubation, cells were released by trypsin treatment, fixed and permeabilized with a p-formaldehyde solution and stained with a rabies virus nucleocapsid protein-specific antibody conjugate. The percentage of virus infection inhibition caused by specific antibodies present in the serum were evaluated in a Beckton Dickinson FACSCalibur flow cytometer. A correlation curve between the IU/ml content and the percentage of infective inhibition was built with a reference serum and the VNA titers of serum samples were obtained by extrapolation. Titers obtained by FC and standard test showed an effective pairing results (p < 0.01), with a correlation coefficient (r) = 0.7. These results permit to envisage the FC as a suitable technique to evaluate VNA in sera from immunized animals and likely in human serum samples. Nevertheless, new studies comparing FC to gold-standard techniques are required for determining the FC values of Sensibility and Specificity.     

Liposome-encapsulated amphotericin B for treatment of disseminated candidiasis in neutropenic mice

The relative efficacies of free amphotericin B (Amp B) and liposome-encapsulated Amp B (L-AmpB) in the treatment of established Candida albicans infection in mice rendered neutropenic with cyclophosphamide were studied. AmpB was entrapped in multilamellar liposomes composed of dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol in a molar ratio of 7:3. Infected mice treated with single doses of 3 mg L-AmpB/kg of body weight had an increased survival time compared with those injected with either single (dose, 0.8 mg/kg) or multiple doses (dose, 0.8 mg/kg daily for five days) of free AmpB. When treatment was delayed beyond three days postinfection, neither single nor multiple doses of free AmpB resulted in increased survival, whereas treatment with single-dose L-AmpB (dose, 4 mg/kg) showed efficacy when delayed as much as four days postinfection. Five days postinfection only higher doses (dose, 5.6 mg-11.2 mg/kg) of L-AmpB improved survival time and the renal impairment present in the infected animals. These data provided a rational basis for using high-dose L-AmpB to treat fungal diseases in humans, particularly in neutropenic patients.     

Does sterile or nonsterile technique make a difference in wounds healing by secondary intention?

After observing inconsistencies in care of acute surgical wounds healing by secondary intention and reviewing the potential cost savings of implementing clean dressing change technique policies, surgical nurses at a university-based medical center monitored supply usage and infection rates of these wounds using a nonexperimental, longitudinal study design. Staff from two acute care surgical units provided data for 3 months before and 3 months after standardization of wound care to a clean wound care technique. All adult patients requiring dressing changes three times per day with normal saline moistened gauze of their open surgical wound(s) participated in the study. Before changing the wound care procedures, nine (9) of 1,070 (0.84%) admissions to the two surgical units had a surgical site infection. During the 3 months following implementation of clean wound care protocols, eight (8) surgical site infections were documented in 963 admissions (rate.83%). Dressing supply costs were $380 less. In this study, using nonsterile wound care procedures for wounds healing by secondary intention did not negatively impact infection rates and saved supply costs.     

Examiner standardization for caries studies.

Examiners in clinical control programs customarily undergo an intensive period of training to standardize their interpretation of diagnostic criteria. Data are presented summarizing examiner error rates in calibration examinations and reversal rates in a field study.     

Lesions of the basal forebrain alter stimulus-evoked metabolic activity in mouse somatosensory cortex

The role that acetylcholine plays in processing sensory stimuli is beginning to be characterized; however, morphological correlates of cholinergic effects on activity patterns in sensory cortex are not available. To study this problem, unilateral neurotoxic lesions that depleted the necortex of acetylcholine were made in the basal forebrains of mice. The aim of these experiments was to study the effect of cholinergic depletion on stimulus-evoked activity in the barrel field of the mouse somatosensory cortex. One month following the lesion, 2-deoxyglucose (2DG) experiments were conducted on the lesioned and on normal mice while the animal received bilateral stimulation to the C3 whisker. The tissue was processed for acetylcholinesterase and cytochrome oxidase histochemistry and 2DG autoradiography. Evaluation of the column-like 2DG label evoked in the somatosensory cortex revealed that the activity on the lesioned side was significantly reduced in dimension and intensity from that in the normal hemisphere. On the normal side, the activated barrels averaged 641 microns in tangential width, were 76.5% above background in density, and extended from lamina I-V. On the lesioned side, the activated barrels were 485 microns in tangential width, 65.4% above background in density, and extended from lamina II-V. In other cortical regions, outside the stimulus-evoked barrel field, 2DG activity values were similar on the normal and lesioned side. Additionally, both the pattern and intensity of the cytochrome oxidase staining within the barrel field displayed no differences in either hemisphere. These studies suggest that acetylcholine plays a significant role in the processing of somatosensory information. Neurotoxic lesions that diminish cortical cholinergic innervation cause a reduction of stimulus-evoked activity levels, while underlying metabolic activity is either not affected or recovers over time.