Measurement of cardiac output by the foreign gas method using nitrous oxide.

Although he apparently never used it himself, Fick in 1870 elaborated the well known principle, bearing his name, for measuring cardiac output. He expressed it in the same form as it is presently used, i.e. that if one knows the amount of oxygen taken up by the lungs per unit time (or the amount of carbon dioxide eliminated also per unit time) and the difference in concentrations of oxygen (or carbon dioxide) between the arterial and the venous blood, then one can calculate the amount of blood flowing through the lung during that time. [...

Work-Related Respiratory Disorders in Persons Employed in Quebec Cotton Textile Mills – 1980 to 1995

Byssinosis, a chronic lung disease of cotton mill workers, is characterized by repeated episodes of reversible airway obstruction, which can lead to permanent alterations of lung function. When this occurs in Quebec the worker must be removed from further exposure in accordance with the provincial compensation rules. The current Quebec Occupational Safety and Health Regulation has a permissible exposure limit of 500 μg/m3, resulting in a prevalence rate of byssinosis of 2% to 5% in cotton workers. In this study the incidence of new respiratory disorders in persons employed in Quebec cotton mills from 1980 to 1995 was assessed and factors that identified byssinosis cases were analyzed. Incidence of the disease was assessed on the basis of cases referred to the Commission de Santé & Sécurité au travail du Québec (Quebec Workers’ Compensation Board) from all Quebec textile plants. Analyses of age, years of employment, job description, smoking history, bronchial reactivity and lung function before and at work were used for diagnostic purposes. Incidence of new byssinosis cases from 1990 to 1995 was 2.8 cases per year per 5000 workers, slightly above the incidence from 1980 to 1989, at 1.7 cases per year. The incidence of chronic cases was stable at 1.5 cases per year, whereas that of early cases increased from 0.3 cases per year (1980 to 1989) to 1.25 cases per year (1990 to 1995). In comparison with chronic byssinosis cases, the average time of work before symptom appearance was 17±4 versus 32±1 years, P<0.001. Bronchial reactivity to methacholine (PC20) at work was below 2 mg/mL in 100% of byssinosis cases versus 14% in subjects not diagnosed with byssinosis. Decreases in forced expiratory volume in 1 s (FEV1) at work averaged 30% in the byssinosis and 6% in the nonbyssinosis subjects; peak flow rates were not different between those with and those without byssinosis. Early byssinosis cases were from three distinct plants in different townships, and 45% of cases worked in cardroom occupations. PC20 equal to or less than 2 mg/mL at work was strongly associated with the decrease in FEV1 during a work shift. In conclusion, current cotton processing work in Quebec is associated with a significant incidence of byssinosis. PC20 of 2 mg/mL or less at work was closely associated with airflow limitation at work

Point-of-care urine tests for smoking status and isoniazid treatment monitoring in adult patients.

Poor adherence to isoniazid (INH) preventive therapy (IPT) is an impediment to effective control of latent tuberculosis (TB) infection. TB patients who smoke are at higher risk of latent TB infection, active disease, and TB mortality, and may have lower adherence to their TB medications. The objective of our study was to validate IsoScreen and SmokeScreen (GFC Diagnostics, UK), two point-of-care tests for monitoring INH intake and determining smoking status. The tests could be used together in the same individual to help identify patients with a high-risk profile and provide a tailored treatment plan that includes medication management, adherence interventions, and smoking cessation programs.200 adult outpatients attending the TB and/or the smoking cessation clinic were recruited at the Montreal Chest Institute. Sensitivity and specificity were measured for each test against the corresponding composite reference standard. Test reliability was measured using kappa statistic for intra-rater and inter-rater agreement. Univariate and multivariate logistic regression models were used to explore possible covariates that might be related to false-positive and false-negative test results. IsoScreen had a sensitivity of 93.2% (95% confidence interval [CI] 80.3, 98.2) and specificity of 98.7% (94.8, 99.8). IsoScreen had intra-rater agreement (kappa) of 0.75 (0.48, 0.94) and inter-rater agreement of 0.61 (0.27, 0.90). SmokeScreen had a sensitivity of 69.2% (56.4, 79.8), specificity of 81.6% (73.0, 88.0), intra-rater agreement of 0.77 (0.56, 0.94), and inter-rater agreement of 0.66 (0.42, 0.88). False-positive SmokeScreen tests were strongly associated with INH treatment.IsoScreen had high validity and reliability, whereas SmokeScreen had modest validity and reliability. SmokeScreen tests did not perform well in a population receiving INH due to the association between INH treatment and false-positive SmokeScreen test results. Development of the next generation SmokeScreen assay should account for this potential interference

Example of an indeterminate SmokeScreen result.

<p>Original urine colour (no colour change)  =  negative test result. Dark blue-purple IsoScreen test  =  positive test result. Orange-pink SmokeScreen test  =  positive test result. Dark blue SmokeScreen test (not orange-pink)  =  indeterminate test result.</p

Example of a IsoScreen and SmokeScreen negative test result.

<p>Original urine colour (no colour change)  =  negative test result. Dark blue-purple IsoScreen test  =  positive test result. Orange-pink SmokeScreen test  =  positive test result. Any other colour change  =  indeterminate test result.</p

Summary of validity and reliability measures for IsoScreen.

<p>Summary of validity and reliability measures for IsoScreen.</p

INH Intake Reference Standard scoring system.

<p>INH Intake Reference Standard scoring system.</p

Summary of validity and reliability measures of SmokeScreen.

<p>Summary of validity and reliability measures of SmokeScreen.</p

Example of a SmokeScreenpositivetest result.

<p>Original urine colour (no colour change)  =  negative test result. Dark blue-purple IsoScreen test  =  positive test result. Orange-pink SmokeScreen test  =  positive test result. Any other colour change  =  indeterminate test result.</p