Muscle weakness, health status and frequency of exacerbations in chronic obstructive pulmonary disease.

BACKGROUND: Multiple factors contribute to muscle weakness and reduced muscle mass in chronic obstructive pulmonary disease (COPD) and this impacts patients' quality of life. One factor implicated in this process is systemic inflammation, an accompaniment of acute exacerbations. Recurrent exacerbations are associated with lower health status. This study examines the relationship between muscle weaknesses, health status and exacerbation frequency in a cohort of patients with COPD. METHODS: This is an observational study of 188 (95 female) patients with COPD attending two hospital clinics in the northeast of England between 2004 and 2007. We measured spirometry, body mass index, health status (St George's Respiratory Questionnaire) and grip strength and recorded Medical Research Council dyspnoea scores and the frequency of exacerbations in the previous year. RESULTS: Patients were aged 72.5±8.3 years (data expressed as mean±SD) with Medical Research Council score of 3.6±0.8, forced expiratory volume in one second (FEV(1)) of 49.2±21.5 per cent predicted and a total St George's Respiratory Questionnaire score of 72.2±15.5. Grip strength, expressed as per cent predicted, was 72.0±21.8 in men and 81.0±18.2 in women. Exacerbations ranged from zero to five in the previous year and there were associations of reduced grip strength with exacerbation frequency (χ(2)=9.634; p=0.0019) and lower health status (χ(2)=34.00; p<0.001). CONCLUSION: Our data clearly demonstrate that reduction in grip strength occurs more frequently and to a greater extent in patients with a history of frequent exacerbations and is associated with reduced health status.

Developing a real time sensing system to monitor bacteria in wound dressings.

Infection control is a key aspect of wound management strategies. Infection results in chemical imbalances and inflammation in the wound and may lead to prolonged healing times and degradation of the wound surface. Frequent changing of wound dressings may result in damage to healing tissues and an increased risk of infection. This paper presents the first results from a monitoring system that is being developed to detect presence and growth of bacteria in real time. It is based on impedance sensors that could be placed at the wound-dressing interface and potentially monitor bacterial growth in real time. As wounds can produce large volumes of exudate, the initial system reported here was developed to test for the presence of bacteria in suspension. Impedance was measured using disposable silver-silver chloride electrodes. The bacteria Staphylococcus aureus were chosen for the study as a species commonly isolated from wounds. The growth of bacteria was confirmed by plate counting methods and the impedance data were analysed for discernible differences in the impedance profiles to distinguish the absence and/or presence of bacteria. The main findings were that the impedance profiles obtained by silver-silver chloride sensors in bacterial suspensions could detect the presence of high cell densities. However, the presence of the silver-silver chloride electrodes tended to inhibit the growth of bacteria. These results indicate that there is potential to create a real time infection monitor for wounds based upon impedance sensing.

Analytical model of peptide mass cluster centres with applications.

BACKGROUND: The elemental composition of peptides results in formation of distinct, equidistantly spaced clusters across the mass range. The property of peptide mass clustering is used to calibrate peptide mass lists, to identify and remove non-peptide peaks and for data reduction. RESULTS: We developed an analytical model of the peptide mass cluster centres. Inputs to the model included, the amino acid frequencies in the sequence database, the average length of the proteins in the database, the cleavage specificity of the proteolytic enzyme used and the cleavage probability. We examined the accuracy of our model by comparing it with the model based on an in silico sequence database digest. To identify the crucial parameters we analysed how the cluster centre location depends on the inputs. The distance to the nearest cluster was used to calibrate mass spectrometric peptide peak-lists and to identify non-peptide peaks. CONCLUSION: The model introduced here enables us to predict the location of the peptide mass cluster centres. It explains how the location of the cluster centres depends on the input parameters. Fast and efficient calibration and filtering of non-peptide peaks is achieved by a distance measure suggested by Wool and Smilansky.

Spot urinary creatinine excretion in pervasive developmental disorders.

BACKGROUND: Excretion of creatinine in urine represents the end-point of endogenous energy transfer from stored adenosine triphosphate in skeletal and cardiac muscle. Measurement of urinary creatinine is commonly used to correct for total urine concentration. Various quantitative measures of compounds suspected to be either pathological to, or indicative of, possible therapeutic interventions for Pervasive Developmental Disorders (PDD) have relied extensively on spot creatinine as a ratio quantity, although this important metabolite has not been exclusively studied within this population. METHODS: Levels of urinary creatinine in spot urine samples were analyzed for a group of children diagnosed with PDD (n=24; median age, 75 months; range, 39-137 months) and a control group (n=50; median age, 109 months; range, 59-140 months). Diagnosis of PDD was confirmed using the Autism Diagnostic Interview-Revised. Samples were collected and analyzed blind for creatinine content using an improved Jaffe's reaction method. RESULTS: Controlling for sample pH and body mass index, a significant decrease in urinary creatinine concentration was found in the PDD group compared to controls using a Mann-Whitney two-tailed ranks test (P=0.001). CONCLUSION: Further studies of protein catabolism and renal function in autism are required to ascertain the relevance of decreased spot urinary creatinine excretion identified in this preliminary study. Issues regarding the use of single urine creatinine measurements and associated confounding variables are discussed in light of the findings, together with recommendations to use other internal or external standards for the quantification of urinary compounds in PDD research.

Investigation into postoperative endophthalmitis and lessons learned.

PURPOSE: To describe an approach to the investigation of a series of endophthalmitis cases to determine whether there was a true outbreak. SETTING: Outpatient facility, Sunderland, England. METHODS: Different approaches to statistical analysis of the probability of infrequent events being due to chance occurrence are described. Potential factors leading to an outbreak were reviewed. RESULTS: Bayesian statistical analysis was shown to be appropriate in the determination of an endophthalmitis outbreak. The only factor found to account for the outbreak was the operating surgeon's recent abandonment of subconjunctival antibiotic prophylaxis. This decision was based on the absence of good evidence that subconjunctival antibiotic injection is effective in prophylaxis. These endophthalmitis cases demonstrate that the absence of evidence for effect is not the same as there being no effect. CONCLUSIONS: Bayesian statistical analysis has a place in determining whether an outbreak has occurred. Withdrawing treatment simply on the basis of a lack of good evidence can lead to undesirable outcomes.