Background: The spirometric reference values are of great importance for diagnosis and treatment of lung diseases. At present, there are no spirometric reference values for First Nations children and adolescents living in Canada. Objectives: The objectives of the present study were (1) to identify the flexible and efficient statistical method to derive lung function reference equations that can be used to obtain the predicted values and Lower Limit of Normal (LLN) for lung function in children and adolescents, and (2) to obtain prediction equations for FVC, FEV1 and FEV1=FVC for First Nations children and adolescents living in rural Saskatchewan, Canada. Methods: Spirometric results from a prospective cohort study, "First Nations Lung Health Project" were used to identify 130 healthy non-smoking children and adolescents. The predicted values and LLN of spirometric indices [Forced Vital Capacity (FVC), Forced Expiratory Volume at one second (FEV1) and FEV1 and FVC ratio (FEV1=FVC)] were calculated for school-going children and adolescents ages 6-17 years. The subjects participating in the study were from two Cree First Nations on-reserve communities located in rural Saskatchewan, Canada. All lung function values were reviewed by a respirologist for acceptability of the test. Following an extensive literature review, the Generalized Additive Models for Location, Scale and Shape (GAMLSS) was identified as a flexible statistical tool to model the lung function variables. The lung function indices were assumed to follow a Box-Cox-Cole-Green (BCCG) distribution with median, , coe ffcient of variation and skewness . Akaike Information Criteria (AIC) approach was used to obtain the reference models. The LLN was calculated by taking the fifth percentile of the prediction equations of the lung function variables. The above approach is recommended for the prediction of lung function of multi-ethnic people aged 3-95 years from different ethnic groups by the Global Lung Function Initiative (GLI). Results: Significant differences were observed in lung function (FVC, FEV1 and FEV1=FVC) and anthropometric measurements between both boys and girls. Therefore, fitting separate equations for both sexes are justified. In GLI, polynomial bases of order 6-7 were used for modeling the meadian, coefficient of variation and skewness . In this study, lower order polynomial bases (up to order 4) were enough to obtain the reference models. In GLI, the polynomial bases were divided by 100 to let it lie within 0 to 1. In this study, the polynomials were divided by 20 to lie these between 0 and 1. The predicted values of FVC was higher than the values for FEV1 in both boys and girls. Therefore the values of FEV1=FVC ratios is less than 100% in this population. In girls, the difference between the curves of FVC and FEV1 was smaller compared to boys. Thus, the total volume of air for girls during exhalation are close to the volume of air exhaled at the first second. The estimated curves showed that the models fitted the lung function data reasonably well. Conclusions: The results in this study showed that the optimum model for the prediction of lung function were almost similar to the ones used by GLI for the prediction of lung function of all-age multi-ethnic populations.The predicted values and LLN values of the lung function variables reported in this study can be recommended to health-care providers for the use in diagnosis respiratory diseases in First Nations children and adolescents in rural Saskatchewan. Small sample (n < 150) was a limitation of this study. This study limitation can be overcome by including more individuals from the follow-up study, which will be conducted in 2016.

Spirometry is the most important tool in diagnosing pulmonary disease and is the most frequently performed pulmonary function test. Respiratory disease is also one of the greatest causes for morbidity and mortality on the Hopi Nation, but no specific reference equations exist for this unique population. The purpose of this study was to determine if population reference equations were necessary for these children and, if needed, to create new age and race-specific pulmonary nomograms for Hopi children. Two hundred and ninety-two healthy children, ages 4-13 years, attending Hopi Nation elementary schools in Arizona, were asked to perform spirometry for a full battery of pulmonary volumes and capacities of which the following were analyzed: forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), FEV1 % (FEV1/FVC), FEF25-75% and peak expiratory flow rate (PEFR). Spirometric data from Navajo children living in the same geographical region as the Hopi children were compared as well as spirometric data from common reference values used for other ethnic groups in the USA. Spirometry tests from 165 girls and 127 boys met American Thoracic Society quality control standards. We found that the natural log of height, body mass and age were significant predictors of FEV1, FVC, and FEF25-75% in the gender-specific models and that lung function values all increased with height and age as expected. The predictions using the equations derived for Navajo, Caucasian, Mexican-American, African-American youth were significantly different (P ≤ 0.05) from the predictions derived from the Hopi equations for all of the variables across both genders, with the exceptions of Hopi versus Navajo FEV1/FVC in the males and Hopi versus Caucasians FEF25-75% in the females. Thus it would appear for this population important to have specific formulae to provide more accurate reference values.

Spirometry is the most important tool in diagnosing pulmonary disease and is the most frequently performed pulmonary function test. Since respiratory disease is the single greatest cause for morbidity and mortality on the Navajo Nation, the purpose of this study was to create newage and race-specific pulmonary nomograms for Navajo children. Five hundred fifty-eight healthy children, ages 6-14 years, attending Navajo Nation elementary schools in Arizona, were asked to perform spirometry to develop population-specific and tribe-specific nomograms for forced vitalcapacity (FVC), forced expiratory volume in 1 sec (FEV1), and FEV1 Ratio (FEV1/FVC). Spirometry tests from 284 girls and 274 boys met American Thoracic Society quality control standards. Lung function values, except for FEV1/FVC, all increased with height. The lower limit of the normal range for FEV1/FVC was 80%. The spirometry reference equations from the healthyboys and girls were developed. Height and the natural log of height were significant predictors of FEV1, FVC, and FEF25-75% in the gender-specific models. The resulting population-specific spirometry reference equations should be used when testing Navajo children ages 6-14 years. However, the use of the NHANES III spirometry reference equations for Caucasian children may not result in significant misclassification in clinical settings providing that a maximal effort is given by the Navajo child being tested.

Background Since anthropometric variables are critical to the creation of pulmonary nomograms for FVC, FEV1, and other volumes and capacities, it is logical that anthropometric variables also influence the values of the maximal respiratory pressures (MRPs). Since nomograms are race-specific, it is important that tribe-specific tables of normal maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) be developed. To date normal tables for MRPs do not exist for Navajo children. Objective Therefore the purpose of this study was to derive MRP normative reference values for Navajo children in the age range of 6-14 years. Methods - Participants and Measurements A cross-sectional study was undertaken with a representative sample of 534 healthy children, ages 6-14 years, attending Navajo Nation elementary schools in Arizona. MIP and MEP were measured. Results Test results from 275 girls and 259 boys met American Thoracic Society quality control standards and showed that MRPs all increased with height. Mean MIP in cm H2O was 77 for boys and 67 for girls with lower limits of 44 and 40, respectively. Mean MEP in cm H2O was 75 for boys and 66 for girls with the lower limits of 42 and 38, respectively. Conclusion Since the data were collected from the population of interest, the resulting MIP and MEP reference equations should be used when testing Navajo children ages 6-14 years.

Background Since anthropometric variables are critical to the creation of pulmonary nomograms for FVC, FEV1, and other volumes and capacities, it is logical that anthropometric variables also influence the values of the maximal respiratory pressures (MRPs). Since nomograms are race-specific, it is important that tribe-specific tables of normal maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) be developed. To date normal tables for MRPs do not exist for Navajo children. Objective Therefore the purpose of this study was to derive MRP normative reference values for Navajo children in the age range of 6-14 years. Methods - Participants and Measurements A cross-sectional study was undertaken with a representative sample of 534 healthy children, ages 6-14 years, attending Navajo Nation elementary schools in Arizona. MIP and MEP were measured. Results Test results from 275 girls and 259 boys met American Thoracic Society quality control standards and showed that MRPs all increased with height. Mean MIP in cm H2O was 77 for boys and 67 for girls with lower limits of 44 and 40, respectively. Mean MEP in cm H2O was 75 for boys and 66 for girls with the lower limits of 42 and 38, respectively. Conclusion Since the data were collected from the population of interest, the resulting MIP and MEP reference equations should be used when testing Navajo children ages 6-14 years.