Development of reference equations for the six-minute walk distance of school-aged Nigerian children

BACKGROUND: The six-minute walk test (6MWT), a simple, reliable and valid test that uses the distance walked in six minutes (six-minute walk distance, 6MWD) to quantify functional exercise capacity, is widely used in chronic cardiopulmonary and non-cardiopulmonary disorders. However, th absence of reference standards for Nigerian school-aged children limits its utility in this age group OBJECTIVES: To develop normative values and equations for the 6MWT of school-aged Nigerian children METHODS: In a cross-sectional study, healthy Nigerian children aged 6-11 years in Lagos completed 6MWT on 20-meter straight outdoor courses in their schools following standardized guidelines. Potential predictors: demographic (age, sex), anthropometric (height, weight, chest circumference, leg length) and physiological data [pre-walk, immediate post-walk and 5th-minute post-walk heart rate (HR), oxygen saturation (SpO2), systolic blood pressure (SBP), diastolic blood pressure (DBP) and rating of perceived exertion (RPE)] and the difference between pre-walk and post-walk HR (HR change), SpO2 (SpO2 change), SBP (SBP change), DBP (DBP change) and RPE (RPE change). Primary outcomes:six-minute walk distance (6MWD) in meters. RESULTS: Overall, 627 pupils (52.1% girls) walked 504.6 (66.6) m (95% CI: 499.4, 509.8), ranging from 326.6 to 673.0 m; boys walking 16 m longer (p=0.002). Stepwise linear regression yielded 6MWD=347.9+14(Age in years)+1.6(HR change)+17.6(sex; male=1, female=0)+1.2(SBP change);R square=0.25.Previously published reference equations mostly over-estimated Nigerian children's 6MWD. CONCLUSION: The reference values and equations, after validation in other Nigerian geographic populations, may be useful for the functional evaluation of Nigerian children aged 6-11 years with chronic childhood disorders.

Implications of using the GLI-2012, GOLD and Australian COPD-X recommendations in assessing the severity of airflow limitation on spirometry among an Indigenous population with COPD: an Indigenous Australians perspective study

BackgroundAssessment of airflow limitation (AFL) is crucial in the clinical evaluation of patients with chronic obstructive pulmonary disease (COPD). However, in the absence of normative reference values among adult Australian Indigenous population, the implications of utilising the Global Lung Function Initiative (GLI-2012), Global Initiative for Chronic Obstructive Lung Disease (GOLD) and the Australian concise COPD-X recommended severity classifications is not known. Moreover, spirometry values (forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1)) are observed to be 20%–30% lower in an apparently healthy Indigenous population in comparison to Caucasian counterparts.MethodsAdult Indigenous patients diagnosed to have COPD on spirometry (postbronchodilator (BD) FEV1/FVC <0.7 ((GOLD, (COPD-X)) and ≤lower limit of normal (others/mixed reference equations) for GLI-2012) were assessed for AFL severity classifications on Post-BD FEV1 values (mild, moderate, severe, very severe) as per the recommended classifications.ResultsFrom a total of 742 unique patient records of Indigenous Australians, 253 were identified to have COPD via GOLD/COPD-X criteria (n=238) or GLI-2012 criteria (n=238) with significant agreeance between criteria (96%, κ=0.901). Of these, the majority were classified as having moderate or severe/very-severe AFL with significant variability across classification criteria (COPD-X (40%–43%), GOLD (33%–65%), GLI-2012 (18%–75%)). The FVC and FEV1 values also varied significantly between classification criterion (COPD-X/GOLD/GLI-2012) within the same AFL category, with COPD-X ‘moderate’ AFL almost matching ‘severe’ AFL categorisation by GOLD or GLI-2012.ConclusionsHealth professionals caring for Indigenous patients with COPD should be aware of the clinical implications and consequences of utilising various recommended AFL classifications in the absence of validated spirometry reference norms among adult Indigenous patients.

Reference Values of Forced Vital Capacity and Expiratory Flow in High-Level Cyclists

Several studies have demonstrated that spirometric theoretical values may not be applicable to the high-level sports population. No reference values exist for high-level professional cyclists. We aimed to establish predictive spirometric values by reference equations. One hundred and forty-five French Caucasian high-level professional cyclists, aged 18–38, performed basic anthropometric assessment and spirometry during the medical evaluation at the beginning of the sport season. Measured values were compared with theoretical values. Predictive equations were established from anthropometric parameters to explain variations of spirometric parameters. High-level cyclists had significantly higher spirometric values than the theoretical values established from a general population, except for forced expiratory volume in one second (FEV1), forced vital capacity (FVC) and forced expiratory flow (FEF) at 25% of FVC. Only FVC and FEV1 were well predicted from body height. The FVC variation of 43.5% is explained by body height and weight. The FEV1 variation of 25.8% is explained only by body height. High-level cycling is associated with important respiratory adaptations depending on the body height and the sport specificity: intensive and prolonged endurance training. These findings are interesting for clinical individual application to diagnose obstructive disease and test reversibility with bronchodilator drugs.

Impact of using different predictive equations on the prevalence of chronic byssinosis in textile workers in Pakistan

ObjectiveByssinosis remains a significant problem among textile workers in low/middle-income countries. Here we share our experience of using different prediction equations for assessing ‘chronic’ byssinosis according to the standard WHO classification using measurements of forced expiratory volume in 1 s (FEV1).MethodsWe enrolled 1910 workers in a randomised controlled trial of an intervention to improve the health of textile workers in Pakistan. We included in analyses the 1724 (90%) men who performed pre-bronchodilator spirometry tests of acceptable quality. We compared four different equations for deriving lung function percentage predicted values among those with symptoms-based byssinosis: the third US National Health and Nutrition Examination Survey (NHANES-III, with ‘North Indian and Pakistani’ conversion factor); the Global Lung Function Initiative (GLI, ‘other or mixed ethnicities’); a recent equation derived from survey of a western Indian population; and one based on an older and smaller survey of Karachi residents.Results58 men (3.4%) had symptoms-based byssinosis according to WHO criteria. Of these, the proportions with a reduced FEV1 (<80% predicted) identified using NHANES and GLI; Indian and Pakistani reference equations were 40%, 41%, 14% and 12%, respectively. Much of this variation was eliminated when we substituted FEV1/forced vital capacity (FVC) ratio (<lower limit of normality) as a measure of airway obstruction.ConclusionAccurate measures of occupational disease frequency and distribution require approaches that are both standardised and meaningful. We should reconsider the WHO definition of ‘chronic’ byssinosis based on changes in FEV1, and instead use the FEV1/FVC.

Spirometric reference equations for Cameroonians aged 4 to 89 years derived using lambda, mu, sigma (LMS) method

Background Spirometric reference values are well known in several ethnic groups but the normative spirometric values of blacks living in Africa have been less studied. The purpose of this study is to establish normative spirometric equations from a representative population of Cameroonian children and adults and compare these equations with those developed by the Global Lung Initiative (GLI) and in Nigerians. Methods Spirometric data from healthy Cameroonians aged 4–89 years randomly collected between 2014 and 2018 were used to derive reference equations using generalized additive model for location (mu), shape (lambda) and scale (sigma). Results A total of 625 children and adolescents (290 males and 335 females) and 1152 adults (552 males and 600 females) were included in the study. The prediction equation for spirometric index was written as: M = Exp[a0 + a1*ln (Height) + a2*ln (Age) + Mspline, Mspline was age related spline contribution]. Applying the GLI standards for African Americans resulted in overall values greater than those found in our study for forced expiratory volume in 1s (FEV1) and forced vital capacity (FVC). These values were very close in children and adolescents while the values obtained with the GLI equations for African Americans were significantly higher in adults. FEV1/FVC ratio in our study was similar for adult males but lower in adult females (88% vs 85%, difference = + 3.5%) when applying Nigerian standards. Conclusions FEV1 and FVC of the Cameroonian infant and adolescent population are very close to those of black Americans. However, FEV1 and FVC of Cameroonian adults are significantly lower than those of black American adults. These equations should allow a more suitable interpretation of spirometry in the Cameroonian population.