Nuances and Management of Hilar Submandibular Sialoliths With Combined Transoral Robotic Surgery-Assisted Sialolithotomy and Sialendoscopy

OBJECTIVE

To describe the management, technical nuances, and success rates of transoral robotic surgery (TORS)-assisted sialolithotomy.

STUDY DESIGN

Retrospective database review.

SETTING

Quaternary academic medical center.

METHODS

Between the months of January 2015 and May 2019, patients with hilar submandibular gland stones underwent 2 main variations of TORS-assisted sialolithotomy and sialendoscopy: (1) TORS followed by sialendoscopy for patients with palpable predominantly single stones and (2) either sialendoscopy followed by TORS and sialendoscopy or sialendoscopy followed by TORS only for patients with nonpalpable or multiple stones. Clinical charts were reviewed to collect data, including stone size (imaging review, intraoperative measurement), palpability, duration of operation, TORS variation, operative challenges, symptom improvement, gland preservation rate, and complications.

RESULTS

Thirty-seven patients were identified. Patients were 26 to 80 years old (mean, 57.2 years), and 40.5% were female. Twenty-four patients (64.9%) underwent TORS followed by sialendoscopy; 10 (27.0%), sialendoscopy followed by TORS and sialendoscopy; and 3 (8.1%), sialendoscopy followed by TORS only. The mean stone size was 12.4 mm (range, 4-28 mm). Eleven patients had multiple stones with a mean 4 stones per patient (range, 2-9). Procedural success was 91.9% (34/37) at a mean follow-up of 34.2 weeks (range, 1.4-262.1), and the gland preservation rate was 97.3% (36/37). No patients reported symptoms of lingual nerve injury at 3-month follow-up.

CONCLUSION

TORS combined with sialendoscopy for hilar submandibular gland sialolithiasis allows for improved visualization of critical anatomy, tissue manipulation, and operative flexibility. In our experience, the operative success rate is high, and duration of surgery compares favorably with conventional combined hilar approaches.

Outcomes After Tracheostomy in COVID-19 Patients

OBJECTIVE

To determine the outcomes of patients undergoing tracheostomy for COVID-19 and of healthcare workers performing these procedures.

BACKGROUND

Tracheostomy is often performed for prolonged endotracheal intubation in critically ill patients. However, in the context of COVID-19, tracheostomy placement pathways have been altered due to the poor prognosis of intubated patients and the risk of transmission to providers through this highly aerosolizing procedure.

METHODS

A prospective single-system multi-center observational cohort study was performed on patients who underwent tracheostomy after acute respiratory failure secondary to COVID-19.

RESULTS

Of the 53 patients who underwent tracheostomy, the average time from endotracheal intubation to tracheostomy was 19.7 days ± 6.9 days. The most common indication for tracheostomy was acute respiratory distress syndrome, followed by failure to wean ventilation and post-extracorporeal membrane oxygenation decannulation. Thirty patients (56.6%) were liberated from the ventilator, 16 (30.2%) have been discharged alive, 7 (13.2%) have been decannulated, and 6 (11.3%) died. The average time from tracheostomy to ventilator liberation was 11.8 days ± 6.9 days (range 2-32 days). Both open surgical and percutaneous dilational tracheostomy techniques were performed utilizing methods to mitigate aerosols. No healthcare worker transmissions resulted from performing the procedure.

CONCLUSIONS

Alterations to tracheostomy practices and processes were successfully instituted. Following these steps, tracheostomy in COVID-19 intubated patients seems safe for both patients and healthcare workers performing the procedure.

Comparison of the toxicity of two chelated copper algaecides and copper sulfate to non-target fish

New pesticide products are reviewed by the United States Environmental Protection Agency for possible effects to non-target aquatic organisms. The required toxicity data are for the active ingredient only, and fail to include toxicity of the mixture of other ingredients found in these pesticides. These ingredients may increase the toxicity of the active ingredient to non-target organisms. Our study compares the toxicity of two formulations of chelated copper algaecides with each other, and to a copper sulfate algaecide. We were particularly interested in the effects of a surfactant that is present in one of the formulations. We found that copper becomes less toxic to fish (e.g. fathead minnow 48-h LC50 = 0.90 mg/L) when it is chelated, providing an additional margin of safety to non-target fish compared to copper sulfate. However, inclusion of a surfactant to the formulation resulted in increased toxicity (e.g. fathead minnow 48-h LC50 = 0.30 mg/L).

Isolation of saprophytic basidiomycetes from soil

A method with the combined advantages of soil particle washing, selective inhibitors, and an indicator substrate was developed to isolate saprophytic basidiomycetes from soil. Organic particles were washed from soil and plated on a medium containing lignin, guaiacol, and benomyl, which reduced mold growth and allowed detection of basidiomycetes producing laccase or peroxidase. The 64 soil samples yielded 67 basidiomycete isolates, representing 51 groups on the basis of morphology and physiology. This method should facilitate investigations into the biodiversity of soil basidiomycetes and yield organisms that are useful in bioremediation of soils contaminated with pesticides or other recalcitrant aromatic compounds.

Conversion of biovolume measurements of soil organisms, grown under various moisture tensions, to biomass and their nutrient content

Direct microscopic measurements of biomass in soil require conversion factors for calculation of the mass of microorganisms from the measured volumes. These factors were determined for two bacteria, five fungi, and a yeast isolated from soil. Moisture stress conditions occurring in nature were simulated by growth in two media using shake cultures, on agar plates, and on membranes held at 34, 330, and 1,390 kPa of suction. The observed conversion factors, i.e., the ratio between dry weight and wet volume, generally increased with increasing moisture stress. The ratios for fungi ranged from 0.11 to 0.41 g/cm with an average of 0.33 g/cm. Correction of earlier data assuming 80% water and a wet-weight specific gravity of 1.1 would require a conversion factor of 1.44. The dry-weight specific gravity of bacteria and yeasts ranged from 0.38 to 1.4 g/cm with an average of 0.8 g/cm. These high values can only occur at 10% ash if no more than 50% of the cell is water, and a specific conversion factor to correct past data for bacterial biomass has not yet been suggested. The high conversion factors for bacteria and yeast could not be explained by shrinkage of cells due to heat fixing, but shrinkage during preparation could not be completely discounted. Moisture stress affected the C, N, and P content of the various organisms, with the ash contents increasing with increasing moisture stress. Although further work is necessary to obtain accurate conversion factors between biovolume and biomass, especially for bacteria, this study clearly indicates that existing data on the specific gravity and the water and nutrient content of microorganisms grown in shake cultures cannot be applied when quantifying the soil microbial biomass.

A comparison of the toxicity of synergized and technical formulations of permethrin, sumithrin, and resmethrin to trout

Synthetic pyrethroids often have synergists added to improve effectiveness, yet decisions regarding the use of these pesticides are often based upon toxicity tests using technical material without the synergist, piperonyl butoxide. We conducted toxicity tests with brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) to compare the toxicity of synergized and technical formulations of permethrin, sumithrin, and resmethrin. We found a significant increase in toxicity in the synergized permethrin formulation using traditional 24, 48, and 96-h tests, relative to tests with the technical formulation. However, there was little difference in toxicity between synergized and technical sumithrin until 48 h had elapsed. Many test fish were strongly intoxicated by either formulation of permethrin or sumithrin, but the synergized formulations of both chemicals affected fish at lower concentrations. Intoxication was potentially severe enough to reduce the survival of these fish in the wild. Following short (6-h) exposures, we also found a larger difference in the number of fish that died or became intoxicated between the synergized and technical formulations of permethrin and sumithrin. Finally, we tested the ability of exposed fish to swim against a current. Fish exposed for 6 h to synergized permethrin and resmethrin had far less swimming stamina than those exposed to technical formulations. We found no difference in the effect on swimming between the synergized and technical formulation of sumithrin. In general, the synergized formulations of these chemicals appeared to cause a faster response than the technical formulations. This response increases the lethal and sublethal impacts of the insecticides. We also found that sumithrin was the least toxic of the three pyrethroids. Since the maximum application rate of sumithrin is half that of the other two pyrethroids, the potential risk to wild trout in streams may be reduced.

Resilience of mycorrhizal fungi on defoliated and fertilized hybrid poplars

We examined the effects of fertilization and gypsy moth defoliation of hybrid poplar (Populus ×canadensis Moench 'Eugenei') on ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) fungal colonization, ECM richness, and ECM composition in the summers of 1997 and 1998. The factorial experiment included two levels of defoliation (defoliated and control) and fertilization (100 kg N·ha–1and control). Gypsy moth (Lymantria dispar L.) populations were manipulated to obtain defoliation in the summer of 1996, 1997, and 1998; fertilization subplots were fertilized with NH4NO3(100 kg N·ha–1) in the spring of these years. There were no significant effects of defoliation on ECM or AM colonization in either year; there was a significant (p ≤ 0.05) decline in AM colonization in fertilized plots in 1997 and a significant interaction between defoliation and fertilization effects on ECM colonization in 1997. In the nondefoliated plots, ECM fungal colonization increased, whereas AM colonization decreased because of fertilization. In the defoliated plots, neither ECM nor AM colonization was affected by fertilization. ECM community composition and richness were unchanged by any treatment. The small and transient effects of defoliation and fertilization on poplar AMs and ECMs demonstrate the tolerance of these early-successional trees to defoliation and their ability to rapidly use high levels of available nitrogen.Key words: Populus, nitrogen, ectomycorrhizas, arbuscular mycorrhizas, ectomycorrhizas, Lymantria dispar (gypsy moth), defoliation.

Breast self-examination and death from breast cancer: a meta-analysis

Breast self-examination (BSE) is widely recommended for breast cancer prevention. Following recent controversy over the efficacy of mammography, it may be seen as an alternative. We present a meta-analysis of the effect of regular BSE on breast cancer mortality. From a search of the medical literature, 20 observational studies and three clinical trials were identified that reported on breast cancer death rates or rates of advanced breast cancer (a marker of death) according to BSE practice. A lower risk of mortality or advanced breast cancer was only found in studies of women with breast cancer who reported practising BSE before diagnosis (mortality: pooled relative risk 0.64, 95% CI 0.56-0.73; advanced cancer, pooled relative risk 0.60, 95% CI 0.46-0.80). The results are probably due to bias and confounding. There was no difference in death rate in studies on women who detected their cancer during an examination (pooled relative risk 0.90, 95% CI 0.72-1.12). None of the trials of BSE training (in which most women reported practising it regularly) showed lower mortality in the BSE group (pooled relative risk 1.01, 95% CI 0.92-1.12). They did show that BSE is associated with considerably more women seeking medical advice and having biopsies. Regular BSE is not an effective method of reducing breast cancer mortality.

Longitudinal trends in exercise capacity and health status after pulmonary rehabilitation in patients with COPD

Pulmonary rehabilitation (PR) programmes produce initial improvements in exercise tolerance and health status in patients with chronic obstructive pulmonary disease (COPD). However, there is limited data on the longer term effects of PR. This study has examined whether the initial benefits gained in exercise tolerance and health status may be maintained after a 1-year follow-up programme. Sixty-six patients with COPD were assessed with the MRC Dyspnoea Scale and found to be moderately disabled due to dyspnoea (MRC Grades 3 and 4). These patients were then randomised to an 8 week outpatient programme of either exercise training and education (Exercise group) or to education alone (Control group). Exercise performance was assessed with the shuttle walking test and health status assessed with two disease-specific measures, the St Georges Respiratory Questionnaire and the Chronic Respiratory Disease Questionnaire. After PR, all patients were invited to attend monthly follow-up sessions for 1 year. Fifty-six patients were available for follow-up immediately after the programme and were assessed at 6 months and 1 year. This study has shown that the patients in the Exercise group maintained improvements in exercise capacity and health status up to 6 months after an 8 week programme. At 1 year there was a significant difference between the Exercise and Control groups in terms of exercise tolerance due to a considerable decline experienced by the Control group. However, neither group had maintained improvements in health status at 1 year. Further study is required to assess whether benefit may be sustained for a longer period using alternative follow-up strategies.

An evaluation of the reliability and sensitivity of the London Chest Activity of Daily Living Scale (LCADL)

We have previously reported the validity of a new assessment tool; the London Chest Activity of Daily Living Scale (LCADL). This work investigates the reliability and responsiveness of that measure. Reliability was assessed in 19 patients with stable severe chronic obstructive pulmonary disease (COPD); median age (range) 66 (55-79) years, FEV1 mean (SD) 0.91 (0.29) l, by test-retest 4 weeks apart. Responsiveness was assessed in 59 patients; median age (range) 66 (38-84) years, FEV1 mean (SD) 0.87 (0.30) l, who had undergone at least 6 weeks of pulmonary rehabilitation. Test-retest scores of the LCADL showed a strong relationship with one another, Intraclass correlation coefficient Icc=0.93 95%CI (0.82-0.97) demonstrating evidence of good reliability. With the exception of the Domestic component, all domains of the LCADL showed a statistically significant reduction in dyspnoea during ADLs after pulmonary rehabilitation. There was a statistically significant improvement in the total LCADL score (mean difference (95% CI) -5.91 (from -9.23 to -2.60) after rehabilitation. These data support the use of the LCADL as an outcome measure in COPD which is valid, reliable and responsive to change.

Effects of agronomic treatments on structure and function of ammonia-oxidizing communities

The aim of this study was to determine the effects of different agricultural treatments and plant communities on the diversity of ammonia oxidizer populations in soil. Denaturing gradient gel electrophoresis (DGGE), coupled with specific oligonucleotide probing, was used to analyze 16S rRNA genes of ammonia oxidizers belonging to the beta subgroup of the division Proteobacteria by use of DNA extracted from cultivated, successional, and native deciduous forest soils. Community profiles of the different soil types were compared with nitrification rates and most-probable-number (MPN) counts. Despite significant variation in measured nitrification rates among communities, there were no differences in the DGGE banding profiles of DNAs extracted from these soils. DGGE profiles of DNA extracted from samples of MPN incubations, cultivated at a range of ammonia concentrations, showed the presence of bands not amplified from directly extracted DNA. Nitrosomonas-like bands were seen in the MPN DNA but were not detected in the DNA extracted directly from soils. These bands were detected in some samples taken from MPN incubations carried out with medium containing 1,000 microg of NH(4)(+)-N ml(-1), to the exclusion of bands detected in the native DNA. Cell concentrations of ammonia oxidizers determined by MPN counts were between 10- and 100-fold lower than those determined by competitive PCR (cPCR). Although no differences were seen in ammonia oxidizer MPN counts from the different soil treatments, cPCR revealed higher numbers in fertilized soils. The use of a combination of traditional and molecular methods to investigate the activities and compositions of ammonia oxidizers in soil demonstrates differences in fine-scale compositions among treatments that may be associated with changes in population size and function.

Randomized controlled trial of domiciliary noninvasive positive pressure ventilation and physical training in severe chronic obstructive pulmonary disease

The addition of noninvasive positive pressure ventilation (NPPV) to an exercise training (ET) program in severe chronic obstructive pulmonary disease (COPD) may produce greater benefits in exercise tolerance and quality of life than after training alone. Forty-five patients with severe stable COPD-mean (SD) FEV(1) 0.96 (0.31) L, Pa(O(2)) 65.4 (9.07) mm Hg, Pa(CO(2)) 45.6 (7.89) mm Hg-were randomized to domiciliary NPPV + ET (n = 23) or ET alone (n = 22). Exercise capacity and health status were assessed at baseline and after an 8-wk training program. There was a significant improvement in mean shuttle walk test (SWT) in the NPPV + ET group: from 169 (112) to 269 (124) m (p = 0.001), compared with the ET group: 205 (100) to 233 (123) m (p = 0.19); mean difference (95% confidence interval [CI]): 72 (12.9 to 131) m. Repeated measures analysis of variance (ANOVA) showed that the differences between the two groups became evident only in the final 4 wk of the training program with a mean end study difference (95% 1CI) of 65.8 (17.1 to 114) m. There was a significant improvement in the Chronic Respiratory Disease Questionnaire (CRDQ) of mean (SD) 24.0 (17.4) (p = < 0.001) in the NPPV + ET group and 11.8 (15.8) (p = 0.003) points in the ET group; mean difference: 12.3 (1.19 to 23.4). Only the NPPV + ET group demonstrated a significant improvement in arterial oxygenation; mean difference: 3.70 mm Hg (0.37 to 7.27). This study suggests that domiciliary NPPV can be used successfully to augment the effects of rehabilitation in severe COPD.

Greenhouse gases in intensive agriculture: contributions of individual gases to the radiative forcing of the atmosphere

Agriculture plays a major role in the global fluxes of the greenhouse gases carbon dioxide, nitrous oxide, and methane. From 1991 to 1999, we measured gas fluxes and other sources of global warming potential (GWP) in cropped and nearby unmanaged ecosystems. Net GWP (grams of carbon dioxide equivalents per square meter per year) ranged from 110 in our conventional tillage systems to -211 in early successional communities. None of the annual cropping systems provided net mitigation, although soil carbon accumulation in no-till systems came closest to mitigating all other sources of GWP. In all but one ecosystem, nitrous oxide production was the single greatest source of GWP. In the late successional system, GWP was neutral because of significant methane oxidation. These results suggest additional opportunities for lessening the GWP of agronomic systems.

Greenhouse gases in intensive agriculture: contributions of individual gases to the radiative forcing of the atmosphere

Agriculture plays a major role in the global fluxes of the greenhouse gases carbon dioxide, nitrous oxide, and methane. From 1991 to 1999, we measured gas fluxes and other sources of global warming potential (GWP) in cropped and nearby unmanaged ecosystems. Net GWP (grams of carbon dioxide equivalents per square meter per year) ranged from 110 in our conventional tillage systems to -211 in early successional communities. None of the annual cropping systems provided net mitigation, although soil carbon accumulation in no-till systems came closest to mitigating all other sources of GWP. In all but one ecosystem, nitrous oxide production was the single greatest source of GWP. In the late successional system, GWP was neutral because of significant methane oxidation. These results suggest additional opportunities for lessening the GWP of agronomic systems.

Acute exacerbations of chronic obstructive pulmonary disease are accompanied by elevations of plasma fibrinogen and serum IL-6 levels

BACKGROUND

Respiratory tract infections may acutely increase risk from coronary heart disease (CHD), though the mechanisms have not been defined. Patients with chronic obstructive pulmonary disease (COPD) are prone to repeated exacerbations that are often associated with respiratory infections. These patients also have increased cardiovascular morbidity and mortality. We hypothesized that transient acute increases in plasma fibrinogen, an independent risk factor for CHD, could occur at COPD exacerbation (mediated through a rise in IL6) and thereby provide a mechanism linking respiratory infection to risk of coronary heart disease.

METHODS

93 COPD patients [mean (SD) age 66.8 (8.1) years] were followed regularly over one year, with daily diary card monitoring of respiratory symptoms and peak expiratory flow rate (PEFR); 67 patients [mean FEV1 1.06 (0.44) l, FVC 2.43 (0.79) l] were seen during 120 exacerbations. At each visit spirometry was measured and blood samples taken for plasma fibrinogen and Interleukin-6 (IL-6) levels.

RESULT

At baseline, the mean (SD) plasma fibrinogen was elevated at 3.9 (0.67) g/l in the 67 patients with exacerbations during the study and the median (IQR) IL-6 at 4.3 (2.4 to 6.8) pg/ml. Plasma fibrinogen increased by 0.36 (0.74) g/l at exacerbation (p <0.001). with IL-6 levels rising by 1.10 (-2.73 to 6.95) pg/ml (p = 0.008). There was a relation between the changes in fibrinogen at exacerbation and IL-6 levels (r = 0.348, p <0.001). Multiple regression revealed significantly greater rises in fibrinogen when exacerbations were associated with purulent sputum (b = 0.34 g/l; p = 0.03), increased cough (b = 0.31 g/l, p = 0.019) and symptomatic colds (b = 0.228; p = 0.024).

CONCLUSIONS

Plasma fibrinogen levels were elevated in stable patients with COPD and may contribute to the increased cardiovascular morbidity and mortality in these patients. COPD exacerbations increased serum IL-6 levels, leading to a rise in plasma fibrinogen. Thus acute rather than chronic infection may have a role in predisposing to coronary heart disease or stroke.

Supplemental oxygen during pulmonary rehabilitation in patients with COPD with exercise hypoxaemia

BACKGROUND

Supplemental oxygen in patients with chronic obstructive pulmonary disease (COPD) and exercise hypoxaemia improves exercise capacity and dyspnoea. However, the benefit of oxygen during pulmonary rehabilitation in these patients is still unknown.

METHODS

Twenty five patients with stable COPD (mean (SD) forced expiratory volume in one second (FEV(1)) 0.76 (0.29) l and 30.0 (9.89)% predicted, arterial oxygen tension (PaO(2)) 8.46 (1.22) kPa, arterial carbon dioxide tension (PaCO(2)) 6.32 (1.01) kPa) and significant arterial desaturation on exercise (82.0 (10.4)%) were entered onto a pulmonary rehabilitation programme. Patients were randomised to train whilst breathing oxygen (OT) (n = 13) or air (AT) (n = 12), both at 4 l/min. Assessments included exercise tolerance and associated dyspnoea using the shuttle walk test (SWT) and Borg dyspnoea score, health status, mood state, and performance during daily activities.

RESULTS

The OT group showed a significant reduction in dyspnoea after rehabilitation compared with the AT group (Borg mean difference -1.46 (95% CI -2.72 to -0.19)) but there were no differences in other outcome measures: SWT difference -23.6 m (95% CI -70.7 to 23.5), Chronic Respiratory Disease Questionnaire 3.67 (95% CI -7.70 to 15.1), Hospital Anxiety and Depression Scale 1. 73 (95% CI -2.32 to 5.78), and London Chest Activity of Daily Living Scale -2.18 (95% CI -7.15 to 2.79). At baseline oxygen significantly improved SWT (mean difference 27.3 m (95% CI 14.7 to 39.8) and dyspnoea (-0.68 (95% CI -1.05 to -0.31)) compared with placebo air.

CONCLUSIONS

This study suggests that supplemental oxygen during training does little to enhance exercise tolerance although there is a small benefit in terms of dyspnoea. Patients with severe disabling dyspnoea may find symptomatic relief with supplemental oxygen.

Development and validation of a standardized measure of activity of daily living in patients with severe COPD: the London Chest Activity of Daily Living scale (LCADL)

Activities of daily living (ADL) may be severely restricted in patients with COPD and assessment requires evaluation of the impact of disability and handicap on daily life. This study is concerned with the development and validation of a standardized 15-item questionnaire to assess routine ADL. Sixty (33 male, 27 female) patients with severe COPD, mean (SD) FEV1 0.91 (0.43) l, median (range) age 70 (50-82) years, completed a 59-item ADL list previously generated by open-ended interview and by literature review. Patients also performed the Shuttle Walk Test (SWT), and completed the St George's Respiratory Questionnaire (SGRQ), the Nottingham Extended Activity of Daily Living Questionnaire (EADL) and the Hospital Anxiety and Depression score (HAD). Criteria for item reduction in the development of The London Chest ADL scale (LCADL) consisted of removal of items where the majority of respondents showed no limitation in the activity (n = 19), where there was no association with perception of global health (n = 9), where an association with age or gender was detected (n = 4), or where items showed poor reliability on test re-test (n = 9). Fifteen items were identified as core activities of daily living. The LCADL was then compared with other measures of health status in these patients. There were good correlations with the SGRQ activity and impact components (p=0.70; P<0.0001) and (p=0.58; P<0.0001), respectively, and EADL (p=0.45; P<0.001), and a moderate correlation with HAD anxiety (p=0.28; P<0.03). There was a significant relationship between the SWT and LCADL (p=0.58; P<0.0001), suggesting a relationship between impaired exercise performance and lower ADL scores. There was evidence of high internal consistency of the questionnaire with Chronbach's alpha of 0.98. These findings suggest that the LCADL scale is a valid tool for the assessment of ADL in patients with severe COPD.

Quantitative analysis of ammonia oxidising bacteria using competitive PCR

Culture-based methods for enumeration, such as most probable number (MPN) methodologies, have proved inefficient due to difficulties in the isolation and cultivation of ammonia oxidising bacteria in the laboratory. Biases are associated with the isolation of bacteria in selective media and organisms cultivated in the laboratory may not be truly representative of those in the environment. In this study, we developed a competitive PCR (cPCR)-based method based on the amplification of 16S rRNA genes specific for the beta-subgroup proteobacterial ammonia oxidising bacteria for enumeration of these organisms. Populations in both agricultural soils and estuarine sediments were quantified by traditional MPN and by cPCR. The numbers of ammonia oxidisers for both sample types were significantly underestimated by conventional MPN and were 1-3 orders of magnitude lower than those obtained by cPCR. Higher numbers of ammonia oxidisers found in fertilised plots in agricultural soils by the cPCR technique were not observed in MPN estimates. It was necessary to construct a separate standard curve for each sample type as differences in DNA extraction, quantity and purity had a significant bearing on the ease of PCR of both competitor and target DNA.

Atrial fibrillation after coronary artery bypass surgery: a model for preoperative risk stratification

BACKGROUND

Atrial fibrillation (AF) occurs in 20% to 40% of patients after CABG. Identification of patients vulnerable for arrhythmia will allow targeting of those most likely to benefit from prophylactic therapy. The aim of the present study was to evaluate accuracy of a prospectively defined signal-averaged P-wave duration (SAPD) cutoff and additional preoperative characteristics for the prediction of AF after CABG.

METHODS AND RESULTS

Patients undergoing elective isolated CABG were recruited to the present prospective study. SAPD was recorded in all patients. Filtered signals from 3 orthogonal leads were combined in a vector analysis, and total SAPD was measured preoperatively. Postoperative in-hospital AF occurred in 92 (28.2%) of 326 patients. Patients who developed AF were older (65.9 versus 61.7 years of age; P<0.0005) and had longer SAPD (158 versus 145 ms; P<0.0005) than non-AF patients. Incidence of AF increased in patients > or =75 years of age and increased progressively throughout the range of SAPD. Stepwise logistic regression analysis of preoperative variables identified that SAPD >155 ms (odds ratio, 5.37; 95% CI, 3.10 to 9.30; P<0.0005), advanced age (odds ratio, 1. 53; 95% CI, 1.26 to 1.86 per 5-year increase in age; P<0.0005), and male sex (odds ratio, 2.88; 95% CI, 1.30 to 6.40; P<0.01) independently predicted AF. Prospectively defined SAPD >155 ms predicted AF with positive and negative predictive accuracy of 49% and 84%, respectively.

CONCLUSIONS

A combination of prolonged SAPD, advanced age, and male sex identifies patients at high risk for development of AF after CABG.

Usefulness of the Medical Research Council (MRC) dyspnoea scale as a measure of disability in patients with chronic obstructive pulmonary disease

BACKGROUND

Methods of classifying chronic obstructive pulmonary disease (COPD) depend largely upon spirometric measurements but disability is only weakly related to measurements of lung function. With the increased use of pulmonary rehabilitation, a need has been identified for a simple and standardised method of categorising disability in COPD. This study examined the validity of the Medical Research Council (MRC) dyspnoea scale for this purpose.

METHODS

One hundred patients with COPD were recruited from an outpatient pulmonary rehabilitation programme. Assessments included the MRC dyspnoea scale, spirometric tests, blood gas tensions, a shuttle walking test, and Borg scores for perceived breathlessness before and after exercise. Health status was assessed using the St George's Respiratory Questionnaire (SGRQ) and Chronic Respiratory Questionnaire (CRQ). The Nottingham Extended Activities of Daily Living (EADL) score and Hospital Anxiety and Depression (HAD) score were also measured.

RESULTS

Of the patients studied, 32 were classified as having MRC grade 3 dyspnoea, 34 MRC grade 4 dyspnoea, and 34 MRC grade 5 dyspnoea. Patients with MRC grades 1 and 2 dyspnoea were not included in the study. There was a significant association between MRC grade and shuttle distance, SGRQ and CRQ scores, mood state and EADL. Forced expiratory volume in one second (FEV1) was not associated with MRC grade. Multiple logistic regression showed that the determinants of disability appeared to vary with the level of disability. Between MRC grades 3 and 4 the significant covariates were exercise performance, SGRQ and depression score, whilst between grades 4 and 5 exercise performance and age were the major determinants.

CONCLUSIONS

The MRC dyspnoea scale is a simple and valid method of categorising patients with COPD in terms of their disability that could be used to complement FEV1 in the classification of COPD severity.

Comparative diversity of ammonia oxidizer 16S rRNA gene sequences in native, tilled, and successional soils

Autotrophic ammonia oxidizer (AAO) populations in soils from native, tilled, and successional treatments at the Kellogg Biological Station Long-Term Ecological Research site in southwestern Michigan were compared to assess effects of disturbance on these bacteria. N fertilization effects on AAO populations were also evaluated with soils from fertilized microplots within the successional treatments. Population structures were characterized by PCR amplification of microbial community DNA with group-specific 16S rRNA gene (rDNA) primers, cloning of PCR products and clone hybridizations with group-specific probes, phylogenetic analysis of partial 16S rDNA sequences, and denaturing gradient gel electrophoresis (DGGE) analysis. Population sizes were estimated by using most-probable-number (MPN) media containing varied concentrations of ammonium sulfate. Tilled soils contained higher numbers than did native soils of culturable AAOs that were less sensitive to different ammonium concentrations in MPN media. Compared to sequences from native soils, partial 16S rDNA sequences from tilled soils were less diverse and grouped exclusively within Nitrosospira cluster 3. Native soils yielded sequences representing three different AAO clusters. Probes for Nitrosospira cluster 3 hybridized with DGGE blots from tilled and fertilized successional soils but not with blots from native or unfertilized successional soils. Hybridization results thus suggested a positive association between the Nitrosospira cluster 3 subgroup and soils amended with inorganic N. DGGE patterns for soils sampled from replicated plots of each treatment were nearly identical for tilled and native soils in both sampling years, indicating spatial and temporal reproducibility based on treatment.

Functional Gene Hybridization Patterns of Terrestrial Ammonia-Oxidizing Bacteria

Abstract The biochemical pathway and genetics of autotrophic ammonia oxidation have been studied almost exclusively in Nitrosomonas europaea. Terrestrial autotrophic ammonia-oxidizing bacteria (AAOs), however, comprise two distinct phylogenetic groups in the beta-Proteobacteria, the Nitrosomonas and Nitrosospira groups. Hybridization patterns were used to assess the potential of functional probes in non-PCR-based molecular analysis of natural AAO populations and their activity. The objective of this study was to obtain an overview of functional gene homologies by hybridizing probes derived from N. europaea gene sequences ranging in size from 0.45 to 4.5 kb, and labeled with 32P to Southern blots containing genomic DNA from four Nitrosospira representatives. Probes were specific for genes encoding ammonia monooxygenase (amoA and amoB), hydroxylamine oxidoreductase (hao), and cytochrome c-554 (hcy). These probes produced hybridization signals, at low stringency (30 degreesC), with DNA from each of the four representatives; signals at higher stringency (42 degreesC) were greatly reduced or absent. The hybridization signals at low stringency ranged from 20 to 76% of the total signal obtained with N. europaea DNA. These results indicate that all four functional genes in the ammonia oxidation pathway have diverged between the Nitrosomonas and Nitrosospira groups. The hao probe produced the most consistent hybridization intensities among the Nitrosospira representatives, suggesting that hao sequences would provide the best probes for non-PCR-based molecular analysis of terrestrial AAOs. Since N. europaea can also denitrify, an additional objective was to hybridize genomic DNA from AAOs with probes for Pseudomonas genes involved in denitrification. These probes were specific for genes encoding heme-type dissimilatory nitrite reductase (dNir), Cu-type dNir, and nitrous oxide reductase (nosz). No hybridization signals were observed from probes for the heme-type dNir or nosz, but Nitrosospira sp. NpAV and Nitrosolobus sp. 24-C hybridized, under low-stringency conditions, with the Cu-type dNir probe. These results indicate that AAOs may also differ in their mechanisms and capacities for denitrification.

Randomized controlled trial of pulmonary rehabilitation in severe chronic obstructive pulmonary disease patients, stratified with the MRC dyspnoea scale

This study tested the hypothesis that severity of respiratory disability may affect the outcome of pulmonary rehabilitation. In this randomized, controlled study, 126 patients with chronic obstructive pulmonary disease (COPD) were stratified for dyspnoea using the Medical Research Council (MRC) dyspnoea score into MRC3/4 (Moderate) (n=66) and MRC 5 (Severe) dyspnoeic (n=60) groups. The patients were randomly assigned to an eight week programme of either exercise plus education (Exercise group) or education (Control group). Education and exercise programmes for the moderately dyspnoeic patients were carried out in a hospital outpatient setting. Severely dyspnoeic patients were all treated at home. Those in the Exercise group received an individualized training programme. There was a significant improvement in shuttle walking distance in the moderate dyspnoeic group, who received exercise training; baseline (mean+/-SEM) 191+/-22 m, post-rehabilitation 279+/-22 m (p<0.001). There was no improvement in exercise performance in the severely dyspnoeic patients receiving exercise. Neither group of control patients improved. Health status, assessed by the Total Chronic Respiratory Disease Questionnaire score, increased in the moderately dyspnoeic patients receiving exercise from 80+/-18 to 95+/-17 (p<0.0001) after rehabilitation. Much smaller changes were seen in the other three groups. Improvement in exercise performance and health status in patients with chronic obstructive pulmonary disease after an exercise programme depends on the initial degree of dyspnoea.

Using nasal intermittent positive pressure ventilation on a general respiratory ward

OBJECTIVES

To assess the use of nasal intermittent positive pressure ventilation (NIPPV) in treating acute-on-chronic respiratory failure in a general medical ward.

DESIGN

Retrospective analysis of clinical outcome.

SETTING

A general medical ward of a tertiary respiratory medicine referral centre.

SUBJECTS

Altogether 75 patients admitted with acute exacerbations of chronic respiratory failure and treated NIPPV.

MAIN OUTCOME MEASURES

Blood gas tensions determined at admission to hospital and during NIPPV, tolerance of NIPPV and mortality.

RESULTS

During treatment with NIPPV, the mean (SD) PaO2 increased rapidly by 2.31 (3.58) kPa (p < 0.0001), while the mean PaCO2 fell by 1.07 (1.74) kPa (p < 0.0001) and the mean pH increased by 0.03 (0.07) (p = 0.001). Altogether 57 (76%) of patients tolerated NIPPV, and (9.3%) died in hospital. Improvement in PaO2 was more noticeable in patients with chronic obstructive pulmonary disease (+3.13 (3.49) kPa, p < 0.0001) than in those with restrictive chest wall disease (+1.20 (3.07) kPa, p = 0.25) or obstructive sleep apnoea (+0.18 (3.64), p = 0.88). The reduction in PaCO2 was similar in all three groups.

CONCLUSIONS

In routine treatment of unselected patients with acute-on-chronic respiratory failure who are being cared for on a general ward, NIPPV rapidly improves hypoxaemia and hypercapnia, is well tolerated and is associated with low mortality.

Effect of exacerbation on quality of life in patients with chronic obstructive pulmonary disease

Exacerbations occur commonly in patients with moderate or severe chronic obstructive pulmonary disease (COPD) but factors affecting their severity and frequency or effects on quality of life are unknown. We measured daily peak expiratory flow rate (PEFR) and daily respiratory symptoms for 1 yr in 70 COPD patients (52 male, 18 female, mean age [+/- SD] 67.5 +/- 8.3 yr, FEV1 1.06 +/- 0.45 L, FVC 2.48 +/- 0.82 L, FEV1/FVC 44 +/- 15%, FEV1 reversibility 6.7 +/- 9.1%, PaO2 8.8 +/- 1.1 kPa). Quality of life was measured by the St. George's Respiratory Questionnaire (SGRQ). Exacerbations (E) were assessed at acute visit (reported exacerbation) or from diary card data each month (unreported exacerbation). In 61 (87%) patients there were 190 exacerbations (median 3; range, 1 to 8) of which 93 (51%) were reported. There were no differences in major symptoms (increase in dyspnea, sputum volume, or purulence) or physiological parameters between reported and unreported exacerbations. At exacerbation, median peak flow fell by an average of 6.6 L/min (p = 0.0003). Using the median number of exacerbations as the cutoff point, patients were classified as infrequent exacerbators (E = 0 to 2) or frequent exacerbators (E = 3 to 8). The SGRQ Total and component scores were significantly worse in the group that had frequent exacerbations: SGRQ Total score (mean difference = 14.8, p < 0.001), Symptoms (23.1, p < 0.001), Activities (12.2, p = 0.003), Impacts (13.9, p = 0.002). However there was no difference between frequent and infrequent exacerbators in the fall in peak flow at exacerbation. Factors predictive of frequent exacerbations were daily cough (p = 0.018), daily wheeze (p = 0.011), and daily cough and sputum (p = 0.009) and frequent exacerbations in the previous year (p = 0.001). These findings suggest that patient quality of life is related to COPD exacerbation frequency.

Changing pattern of respiratory tuberculosis in the UK in adult patients from the Indian subcontinent

BACKGROUND

Clinical observations over a 12 year period have suggested a changing pattern of adult respiratory tuberculosis in patients from the Indian subcontinent in two districts of the United Kingdom with a high incidence of tuberculosis.

METHODS

Details of all patients for the period 1981-92 residing in the Newham and Blackburn districts aged 15 and over whose ethnic origin was from the Indian subcontinent (n = 1308) were analysed by stepwise logistic regression to determine the relationship between sputum smear positivity, sputum culture positivity, and isolated mediastinal lymphadenopathy, year of notification, age, sex, ethnic group (Indian or Pakistani), and whether the patient had visited the Indian subcontinent within the last three years.

RESULTS

The proportion of cases who were smear positive rose over the 12 years of the study, as did the proportion of culture positive cases. The proportion with isolated mediastinal lymphadenopathy fell. These changes took place in both districts. They were not explained by demographic changes in age, sex, or ethnic group, nor was there evidence that smear and culture positivity increased in those who had recently visited India or Pakistan.

CONCLUSIONS

The pattern of tuberculosis in adult patients originating from the Indian subcontinent has altered over time towards that seen in the white population in the UK.

One-stop chest pain clinic can identify high cardiac risk

The aim of this study was to record prognosis for patients with stable chest pain referred for outpatient cardiac assessment. All 660 patients in the study had a normal resting ECG and no history of myocardial infarction, unstable angina or coronary revascularisation. Main outcome measures were all-cause mortality, non-fatal ischaemic events and coronary revascularisation. Cardiac chest pain was diagnosed in 182 patients (28%). It was more frequent in patients with recent onset of symptoms (< 6 months), patients over 50, white patients, and patients with hypertension or diabetes. The mean follow-up was 622 +/- 338 days. Among survivors, 37% continued to suffer from symptoms (cardiac group: 59 (35.1%); non-cardiac group: 177 (38.4%)). When all hard events were considered, event-free survival (95% confidence interval) for the cardiac group was 90.9% (86.7-95.2%) at six months, 88.9% (84.2-93.6%) at one year, and 83.6% (77.5-89.7%) at two years. Corresponding figures for the non-cardiac group at the same time points were better (p < 0.0001): 98.5% (97.4-99.6%), 97.5% (96.1-99.0%) and 96.6% (94.7-98.5%), respectively. In conclusion, the use of clinical criteria in a cardiac outpatient clinic, backed up by simple non-invasive investigations, can reliably identify a population at high risk of subsequent cardiac events.

Does long-term oxygen therapy affect quality of life in patients with chronic obstructive pulmonary disease and severe hypoxaemia?

Long-term oxygen therapy (LTOT) improves survival in patients with hypoxaemic chronic obstructive pulmonary disease (COPD), but previous studies using general health measures have shown no effect on quality of life (QoL). In this study, the effect of LTOT on QoL was assessed using a disease-specific health measure, the St George's Respiratory Questionnaire (SGRQ). Twenty three hypoxaemic COPD patients (15 females and 8 males) were studied before and after starting LTOT: median age 71 (range 47-82) yrs, mean (SD) forced expiratory volume in one second (FEV1) 0.75 (0.22) L, arterial oxygen tension (Pa,O2) 6.95 (0.75) kPa, arterial carbon dioxide tension (Pa,CO2) 6.52 (1.21) kPa. A control group comprised 18 COPD patients (6 females and 12 males) with less severe hypoxaemia: median age 72 (range 58-85) yrs, FEV1 0.94 (0.33) L, Pa,O2 8.17 (0.94) kPa, Pa,CO2 6.02 (0.75) kPa. QoL was measured at baseline, 2 weeks, 3 and 6 months. The LTOT group had higher SGRQ total scores than controls (p<0.05) at all visits, implying lower QoL. Repeated measures analysis of variance showed no effect of LTOT on QoL over 6 months (F=0.43, p=0.79). In this study we detected no change in quality of life using a disease-specific health measure in patients with severe chronic obstructive pulmonary disease using an oxygen concentrator to provide long-term oxygen therapy.

Applicability of intermittent global ischemia for repeat coronary artery operations

Despite the increasing popularity of cardioplegic techniques there is no consensus as to the optimal myocardial protective technique for first-time or repeat coronary artery bypass grafting. Intermittent global ischemia was used in 159 consecutive patients (142 male; 17 female) undergoing repeat coronary artery bypass grafting during a 6-year period (1987 to 1992). The median age of the patients was 60 years (90% confidence interval: 47 to 70 years) and the median interval from the first operation was 9 years (90% confidence interval: 2 to 14 years). One third of the patients required emergency (within 24 hours) or urgent (within 7 days) operations because of failure of symptoms to resolve with medical therapy. Compared with events at the initial operation there was an increased prevalence of impaired ventricular function (ejection fraction < 50%) and increased use of the internal thoracic artery (48% versus 9%). Two of 12 patients who required emergency operations died in the hospital, which resulted in an overall mortality rate at 30 days of 1%. Intraaortic balloon pump support was required in five patients (3%) and cardiac dose inotropic support in 21% of patients for up to 24 hours after operation. There was definite electrocardiographic evidence of infarction in 11 patients (7%). The mean postoperative blood loss, without aprotinin, was 627 ml (standard deviation 327 ml) and two patients required reexploration because of bleeding. Five patients had a hemiparesis (3%) and a further four patients (3%) had a mild or transient postoperative focal neurologic deficit. The median postoperative hospital stay was 9 days (90% confidence interval: 7 to 20 days) although 10% of patients required a hospital stay in excess of 21 days. No patient was lost to follow-up. The median (and interquartile range) period of follow-up was 1.6 (1 to 3) years. Eight patients died in the follow-up period, which resulted in an estimated survival of 80% at 5 years. At a mean follow-up period of 2 years (and with or without antianginal medication) 83% of patients had no or minimal angina, 12% had angina on moderate exertion, and 5% had angina on minimal exertion. In comparison with other current series of repeat coronary revascularization our results suggest that repeat coronary artery bypass grafting can be done with intermittent global ischemia with early and intermediate results at least equivalent to those obtained with cardioplegic methods.

Nasal pressure support ventilation plus oxygen compared with oxygen therapy alone in hypercapnic COPD

Non-invasive ventilation has been used in chronic respiratory failure due to chronic obstructive pulmonary disease (COPD), but the effect of the addition of nasal positive-pressure ventilation to long-term oxygen therapy (LTOT) has not been determined. We report a randomized crossover study of the effect of the combination of nasal pressure support ventilation (NPSV) and domiciliary LTOT as compared with LTOT alone in stable hypercapnic COPD. Fourteen patients were studied, with values (mean +/- SD) of Pao2 of 45.3 +/- 5.7 mm Hg, PaCO2 of 55.8 +/- 3.6 mm Hg, and FEV1 of 0.86 +/- 0.32 L. A 4 wk run-in period (on usual therapy) was followed by consecutive 3-mo periods of: (1) oxygen therapy alone, and (2) oxygen plus NPSV in randomized order. Assessments were made during run-in and at the end of each study period. There were significant improvements in daytime arterial PaO2 and PaCO2, total sleep time, sleep efficiency, and overnight PaCO2 following 3 mo of oxygen plus NPSV as compared with run-in and oxygen alone. Quality of life with oxygen plus NPSV was significantly better than with oxygen alone. The degree of improvement in daytime PaCO2 was correlated with the improvement in mean overnight PaCO2. Nasal positive-pressure ventilation may be a useful addition to LTOT in stable hypercapnic COPD.

Ambulatory oxygen therapy in stable kyphoscoliosis

Patients with chronic obstructive pulmonary disease (COPD) may benefit from ambulatory oxygen; however, the effect of exercise on arterial oxygen saturation (Sa,O2) in patients with kyphoscoliosis and of correction with ambulatory oxygen have not been previously reported. Twelve patients with stable kyphoscoliosis (mean (SD) Cobb angle 79 (26) degrees) were studied, with mean (SD) arterial oxygen tension (Pa,O2) 8.96 (0.93) kPa, arterial carbon dioxide tension (Pa,CO2) 6.52 (0.66), forced expiratory volume in one second (FEV1) 0.90 (0.15) L, forced vital capacity (FVC) 1.34 (0.46) L. Six-minute walking tests with oximetry and visual analogue scores (VAS) for breathlessness were performed on air (baseline), and with cylinders containing air and oxygen at 2 L-min-1. Cylinder walks were in random order, with patients blinded to cylinder content. Patients showed oxygen desaturation at each stage of the study. At baseline, oxygen desaturation during exercise was correlated with deterioration in VAS breathlessness scores. Ambulatory oxygen produced significant improvements in desaturation, breathlessness scores and recovery time compared to baseline and air cylinder walks. There was no relationship between baseline desaturation and changes in walking distance. Although exercise desaturation, breathlessness and recovery times were significantly improved with ambulatory oxygen at 2 L.min-1, walking distance was unaffected. We conclude that patients with moderate to severe kyphoscoliosis have significant oxygen desaturation on exercise and should thus routinely receive oximetry on exercise and assessment for ambulatory oxygen therapy.

Ambulatory oxygen therapy in stable kyphoscoliosis

Patients with chronic obstructive pulmonary disease (COPD) may benefit from ambulatory oxygen; however, the effect of exercise on arterial oxygen saturation (Sa,O2) in patients with kyphoscoliosis and of correction with ambulatory oxygen have not been previously reported. Twelve patients with stable kyphoscoliosis (mean (SD) Cobb angle 79 (26) degrees) were studied, with mean (SD) arterial oxygen tension (Pa,O2) 8.96 (0.93) kPa, arterial carbon dioxide tension (Pa,CO2) 6.52 (0.66), forced expiratory volume in one second (FEV1) 0.90 (0.15) L, forced vital capacity (FVC) 1.34 (0.46) L. Six-minute walking tests with oximetry and visual analogue scores (VAS) for breathlessness were performed on air (baseline), and with cylinders containing air and oxygen at 2 L-min-1. Cylinder walks were in random order, with patients blinded to cylinder content. Patients showed oxygen desaturation at each stage of the study. At baseline, oxygen desaturation during exercise was correlated with deterioration in VAS breathlessness scores. Ambulatory oxygen produced significant improvements in desaturation, breathlessness scores and recovery time compared to baseline and air cylinder walks. There was no relationship between baseline desaturation and changes in walking distance. Although exercise desaturation, breathlessness and recovery times were significantly improved with ambulatory oxygen at 2 L.min-1, walking distance was unaffected. We conclude that patients with moderate to severe kyphoscoliosis have significant oxygen desaturation on exercise and should thus routinely receive oximetry on exercise and assessment for ambulatory oxygen therapy.

Use of a network of long-term experiments for analysis of soil carbon dynamics and global change: the North American model

Soils contain a large proportion of the carbon (C) in the terrestrial biosphere, yet the role of soils as a sink or a source of net atmospheric C flux is uncertain. In agricultural systems, soil C is highly influenced by management practices and there is considerable interest in adapting management systems to promote soil C sequestration, thereby helping to mitigate atmospheric CO2 increases. Long-term field experimental sites represent a unique source of information on soil C dynamics, and networks of such sites provide a key ingredient for making large-scale assessments of soil C change across ranges in climate and soil conditions and management regimes. Currently, there are collaborative efforts to develop such site networks in Australia, Europe, and North America. A network of long-term experiments in North America was established to provide baseline information on the effects of management (i.e. tillage, crop rotations, fertilisation, organic amendments) on soil organic matter. Historical data on soils, primary productivity, climate, and management were synthesised by scientists from the individual field sites, representing a total of 35 long-term field experiments. An additional cross-site soil sampling campaign was carried out to provide uniform comparisons of soil C and nitrogen (N), both within and across sites. Long-term field experiments are a principle component necessary for regional assessments of soil C dynamics. We describe a general methodology for combining long-term data with process-oriented simulation models and regional-level, spatially resolved databases. Such analyses are needed to assess past and present changes in soil C at regional to global scales and to make projections of the potential impacts of changes in climate, CO2, and landuse patterns on soil C in agroecosystems.

Nasal ventilation in acute exacerbations of chronic obstructive pulmonary disease: effect of ventilator mode on arterial blood gas tensions

BACKGROUND

There are no controlled trials of the use of different modes of nasal intermittent positive pressure ventilation (NIPPV) in patients with exacerbations of chronic obstructive pulmonary disease (COPD). This study describes the effect on blood gas tensions of four different modes of nasal ventilation.

METHODS

Twelve patients with acute exacerbations of COPD were studied (mean (SD) FEV1 0.59 (0.13) l, PaO2 (air) 5.10 (1.12) kPa, PaCO2 9.28 (1.97) kPa, pH 7.32 (0.03)). Each patient underwent four one-hour periods of nasal ventilation in randomised order: (a) inspiratory pressure support 18 cm H2O; (b) pressure support 18 cm H2O+positive end expiratory pressure (PEEP) 6 cm H2O (IPAP+EPAP); (c) continuous positive airway pressure (CPAP) 8 cm H2O; and (d) volume cycled NIPPV. Arterial blood samples were obtained before each period of ventilation and at one hour.

RESULTS

Pressure support, CPAP, and volume cycled NIPPV all produced significant improvements in PaO2; there was no difference between these three modes. The change in PaO2 with IPAP+EPAP did not reach statistical significance. None of the modes produced significant changes in mean PaCO2; patients with higher baseline levels tended to show a rise in PaCO2 whereas those with lower baseline levels tended to show a fall.

CONCLUSIONS

Although PaO2 improved in all patients there are differences in efficacy between the modes, while the changes in PaCO2 were variable. The addition of EPAP conferred no advantage in terms of blood gas tensions.

Domiciliary oxygen cylinders: indications, prescription and usage

Oxygen therapy for use in the home can be prescribed in two forms: oxygen concentrators are used to provide long term domiciliary oxygen therapy (LTOT), and oxygen cylinders are used to provide oxygen intermittently for relief of symptoms. In this study prescription and usage of oxygen cylinders in the home were assessed. All patients using oxygen cylinders at home in the London Borough of Tower Hamlets in October 1992 were studied. A questionnaire was sent to each patient; further information was obtained from a questionnaire to the general practitioner and from hospital notes where available. Patients with a diagnosis of chronic obstructive pulmonary disease (COPD) were visited at home to measure oxygen saturation levels (SaO2). The main outcome measures were the proportion of oxygen cylinder users who had undergone a full respiratory assessment and the number who might benefit from LTOT. There were 56 patients using oxygen intermittently, 77% with COPD of which 28% had an SaO2 < or = 92%. In these 56 patients 27% had not been assessed by a hospital physician for their chest disease, 58% used their oxygen at least once a day and on average these patients used three cylinders each per month. Most patients using oxygen cylinders at home have a diagnosis of COPD and use oxygen regularly for short term relief of breathlessness; many have not been assessed by a respiratory physician. Measurement of SaO2 suggested that a significant minority might benefit from LTOT and would certainly warrant further evaluation.

14C Allocation in tree-soil systems

We studied whole-tree C allocation with special emphasis on the quantification of C allocation to roots and root respiration. To document seasonal patterns of C allocation, 2-year-old hybrid poplar trees greater than 3 m tall were labeled with (14)CO(2) in a large Plexiglas chamber in the field, in July and September. Climate and CO(2) concentration were controlled to track ambient conditions during labeling. Individual tree canopy CO(2) assimilation averaged 3.8 micromol CO(2) m(-2) s(-1) (12.9 g C day(-1) tree(-1)) in July and 6.2 micromol CO(2) m(-2) s(-1) (9.8 g C day(-1) tree(-1)) in September. Aboveground dark respiration was 12% of net daytime C fixation in July and 15% in September. Specific activity of root-soil respiration peaked 2 days after labeling and stabilized to less than 5% of maximum 2 weeks later. Low specific activity of root-soil respiration and a labeled pool of root C demonstrated that current photosynthate was the primary source of C for root growth and maintenance during the growing season. Root respiration averaged 20% of total soil respiration in both July and September based on the proportion of labeled C respired to labeled C fixed. In July, 80% of the recovered (14)C was found above ground and closely resembled the weight distribution of the growing shoot. By September, 51% of the recovered (14)C was in the root system and closely resembled the weight distribution of different size classes of roots. The finding that the distribution of biomass and (14)C were similar verified that the C introduced during labeling followed normal seasonal translocation pathways. Results are compared to smaller scale labeling studies and the suitability of the approach for studying long-term C fluxes is discussed.

Characteristics of patients with drug resistant and drug sensitive tuberculosis in East London between 1984 and 1992

BACKGROUND

The aim of this study was to investigate retrospectively factors associated with drug resistant tuberculosis at the London Chest Hospital.

METHODS

The microbiology results for patients with tuberculosis at the hospital for the period 1984-92 were reviewed, together with case notes and chest radiographs of all patients with drug resistant tuberculosis and of 101 patients with drug sensitive tuberculosis notified during the same period as a control group.

RESULTS

Culture positive pulmonary tuberculosis occurred in 292 patients. Drug resistant strains were isolated from 20 patients (6.8%). Ten of the 292 (3.4%) had strains resistant to a single drug and nine (3.1%) had resistance to more than one first line drug. One patient had strains resistant to isoniazid and capreomycin. Strains resistant to more than one drug were all resistant to isoniazid and rifampicin. In five patients these strains were also resistant to pyrazinamide and in two they were resistant to streptomycin. Single drug resistant strains were resistant to isoniazid (nine patients) or streptomycin (one patient). Among the risk factors studied previous treatment for tuberculosis was the most significant association with drug resistant tuberculosis (7/9) for patients with resistance to more than one drug; 5/11 for single drug resistance compared with 6/101 patients in the drug sensitive group (odds ratio 22.8). Other risk factors were bilateral disease at presentation (odds ratio 8.5), and disease at a young age (odds ratio 1.03).

CONCLUSIONS

Previous treatment for tuberculosis and bilateral disease at presentation were found to be more commonly associated with cases of drug resistant than with drug sensitive tuberculosis.

Nemesis revisited: tuberculosis infection in a New York City men's shelter

In November 1990, a screening was conducted to determine the point prevalence of tuberculosis infection in a volunteer sample of homeless men (n = 161) living in a congregate shelter in New York City. Of those for whom we have results (n = 134), 79% were positive for tuberculosis. The mean length of shelter stay from date of shelter entry was 31.8 months and was significantly associated with the tuberculosis infection rate. The findings suggest that crowded living conditions and the presence of a stable resident pool in crowded congregate shelters may be associated with transmission of tuberculosis infection.

Assessment and follow up of patients prescribed long term oxygen treatment

BACKGROUND

Prescription and use of long term oxygen treatment were audited in a large group of patients after more than five years of use of the guidelines for its prescription.

METHODS

Patients with a concentrator were interviewed at home with a structured questionnaire in three family health service authorities in East London. Stable oxygen saturation (SaO2) breathing air and oxygen, forced expiratory volume in one second (FEV1) and current and previous dated concentrator meter readings were recorded. A further questionnaire was sent to each patient's general practitioner. Hospital case notes of patients who did not meet the criteria for long term oxygen treatment at reassessment were reviewed.

RESULTS

A total of 176 patients were studied; 84% had chronic obstructive lung disease and 19% admitted to continued smoking; 140 patients had seen a respiratory physician but results of respiratory assessment were available to their general practitioner in fewer than 54 cases. FEV1 was < 1.5 1 in 158 patients but in 67 SaO2 was less than 91% breathing air, mainly in patients with chronic obstructive lung disease who had been inadequately assessed. Daily oxygen was prescribed for a median of 15 (range 4-24) hours and measured daily use was 15 (0-24) hours; 74% of patients used more than 12 hours. Only 35 patients had problems with oxygen treatment, but 29 had an undercorrected SaO2 of less than 92% when using their concentrator.

CONCLUSIONS

Guidelines for prescription of long term oxygen treatment are largely followed and most patients complied with treatment. Increased communication about respiratory state is required between hospital doctors and general practitioners. Patients need regular reassessments to ensure that hypoxaemia is corrected and that oxygen is appropriately prescribed.

Randomised controlled trial of nasal ventilation in acute ventilatory failure due to chronic obstructive airways disease

Acute exacerbations of chronic obstructive airways disease (COAD) are a common cause of admission to hospital, and have a high mortality. Nasal intermittent positive pressure ventilation (NIPPV) has been used successfully in patients with respiratory failure due to neuromuscular and skeletal disorders, but the outcome of treatment in patients with COAD is less well known. We carried out a prospective randomised controlled trial of conventional treatment versus conventional treatment plus NIPPV, in 60 patients with acute ventilatory failure due to exacerbations of COAD. For the NIPPV group there was a rise in pH, compared with a fall in the controls (mean difference of change between the groups 0.046 [95% CI 0.06-0.02, p < 0.001]), and a larger fall in PaCO2 (mean difference in change between the groups 1.2 kPa [95% CI 0.45 to 2.03, p < 0.01]). Median visual analogue scores over the first 3 days of admission showed less breathlessness in the NIPPV group (2.3 cm [range 0.1-5.5]) than in the control group (4.5 cm [range 0.9-8.8]) (p < 0.025). Survival rates at 30 days were compared for intention-to-treat and efficacy populations. In the efficacy mortality comparison, mortality in the NIPPV group was reduced: 1/26 vs 9/30 (relative risk = 0.13, CI = 0.02-0.95, p = 0.014). This effect was less in the intention-to-treat analysis: 3/30 vs 9/30 (relative risk = 0.33, CI = 0.10-1.11, p = 0.106). In patients with acute ventilatory failure due to COAD who received NIPPV there was a significant rise in pH, a reduction in PaCO2 and breathlessness, and reduced mortality.

Comparison of nasal pressure support ventilation with nasal intermittent positive pressure ventilation in patients with nocturnal hypoventilation

Nasal intermittent positive pressure ventilation (NIPPV) provides effective ventilatory support in patients with nocturnal hypoventilation. Nasal pressure support ventilation (NPSV), which only provides ventilation in response to patient triggering, may also be effective, simpler, and cheaper, but has not been evaluated. NIPPV and NPSV were compared in 12 patients with nocturnal hypoventilation, requiring domiciliary ventilatory support. The patients were studied on three consecutive nights, in random order: a control night without ventilation and a night on each mode of ventilatory support using the bilevel positive airway pressure (BiPAP) ventilator. Both NIPPV and NPSV significantly increased mean arterial oxygen saturation (SaO2) compared to the control night (NIPPV mean increase 4.1%; 95% confidence interval (CI) 2.2 to 6.1, NPSV 4.4%; CI 2.1 to 6.6) with no significant difference between the two modes. The percentage of the study night spent below 90% SaO2 was significantly reduced by both ventilator modes compared to the control night (median reduction on NIPPV 37%; CI -54 to -10, reduction on NPSV 31%; CI -53 to -9, with no significant difference between NPSV and NIPPV. NPSV was as effective as NIPPV in patients with nocturnal hypoventilation, which suggests that these patients are able to trigger the ventilator adequately. The lower cost of NPSV will make it accessible to more patients with chronic lung disease.