Which reference equation should we use for interpreting spirometry values for First Nations Australians? A cross-sectional study.

OBJECTIVES: To evaluate the suitability of the Global Lung Function Initiative (GLI)-2012 other/mixed and GLI-2022 global reference equations for evaluating the respiratory capacity of First Nations Australians. DESIGN, SETTING: Cross-sectional study; analysis of spirometry data collected by three prospective studies in Queensland, the Northern Territory, and Western Australia between March 2015 and December 2022. PARTICIPANTS: Opportunistically recruited First Nations participants in the Indigenous Respiratory Reference Values study (Queensland, Northern Territory; age, 3-25 years; 18 March 2015 - 24 November 2017), the Healthy Indigenous Lung Function Testing in Adults study (Queensland, Northern Territory; 18 years or older; 14 August 2019 - 15 December 2022) and the Many Healthy Lungs study (Western Australia; five years or older; 10 October 2018 - 7 November 2021). MAIN OUTCOME MEASURES: Goodness of fit to spirometry data for each GLI reference equation, based on mean Z-score and its standard deviation, and proportions of participants with respiratory parameter values within 1.64 Z-scores of the mean value. RESULTS: Acceptable and repeatable forced expiratory volume in the first second (FEV1) values were available for 2700 First Nations participants in the three trials; 1467 were classified as healthy and included in our analysis (1062 children, 405 adults). Their median age was 12 years (interquartile range, 9-19 years; range, 3-91 years), 768 (52%) were female, and 1013 were tested in rural or remote areas (69%). Acceptable and repeatable forced vital capacity (FVC) values were available for 1294 of the healthy participants (88%). The GLI-2012 other/mixed and GLI-2022 global equations provided good fits to the spirometry data; the race-neutral GLI-2022 global equation better accounted for the influence of ageing on FEV1 and FVC, and of height on FVC. Using the GLI-2012 other/mixed reference equation and after adjusting for age, sex, and height, mean FEV1 (estimated difference, -0.34; 95% confidence interval [CI], -0.46 to -0.22) and FVC Z-scores (estimated difference, -0.45; 95% CI, -0.59 to -0.32) were lower for rural or remote than for urban participants, but their mean FEV1/FVC Z-score was higher (estimated difference, 0.14; 95% CI, 0.03-0.25). CONCLUSION: The normal spirometry values of healthy First Nations Australians may be substantially higher than previously reported. Until more spirometry data are available for people in urban areas, the race-neutral GLI-2022 global or the GLI-2012 other/mixed reference equations can be used when assessing the respiratory function of First Nations Australians.

Association of Gas Diffusing Capacity of the Lung for Carbon Monoxide with Cardiovascular Morbidity and Survival in a Disadvantaged Clinical Population.

PURPOSE: Low diffusing capacity of the lung for carbon monoxide (DLCO) and spirometry values are associated with increased mortality risk. However, associations between mortality risk and cardiovascular disease with the transfer coefficient of the lung for carbon monoxide (KCO) and alveolar volume (VA) are unknown. This cohort study: (i) evaluated whether DLCO, KCO, and VA abnormalities are independently associated with cardiovascular morbidity and/or elevated mortality risk and, (ii) compared these associations with those using spirometry values. METHODS: Gas-diffusing capacity and spirometry data of 1165 adults seen at specialist respiratory outreach clinics over an 8-year period (241 with cardiovascular disease; 108 deceased) were analysed using multivariable Cox and logistic regression. RESULTS: DLCO, KCO, and VA values below the lower limit of normal (< - 1.64 Z-scores) were associated with elevated cardiovascular disease prevalence [respective odds ratios of 1.83 (95% CI 1.31-2.55), 1.56 (95% CI 1.08-2.25), 2.20 (95% CI 1.60-3.01)] and increased all-cause mortality risk [respective hazard ratios of 2.99 (95% CI 1.83-4.90), 2.14 (95% CI 1.38-3.32), 2.75 (95% CI 1.18-2.58)], after adjustment for factors including age, personal smoking, and respiratory disease. Compared to similar levels of spirometry abnormality, DLCO, KCO, and VA were associated with similar or greater mortality risk, and similar cardiovascular disease prevalence. Analysis of only those patients with clinical normal spirometry values (n = 544) showed these associations persisted for DLCO. CONCLUSION: Low DLCO, KCO, and VA measurements are associated with cardiovascular disease prevalence. As risk factors of all-cause mortality, they are more sensitive than spirometry even among patients with no diagnosed respiratory disease.

How Many Maneuvers Should We Do for Maximal Inspiratory and Expiratory Muscle Pressure Testing in Children: A Retrospective Review in Children with Cystic Fibrosis.

OBJECTIVES: Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) could be useful clinical parameters in monitoring many conditions including cystic fibrosis (CF). However, current protocols for undertaking the measurements lack standardization including the number of repeated attempts to achieve best values. We aimed to (a) determine the optimum number of attempts to achieve best MIP/MEP values, and (b) evaluate if the number of attempts is consistent across two different test days. METHODS: We analyzed data of a previous randomized controlled trial involving the effect of singing on respiratory muscle strength in 35 children with CF. On two different days (T1, T2) children performed MIP/MEP with at least ten attempts each to achieve < 10% repeatability. RESULTS: All children achieved repeatable MIP/MEP values within 10-11 attempts with 24 (68.6%) and 26 (74.3%) of these achieving best values of MIP and MEP, respectively, at attempts 6-11. Median values of the pressures by three, five, eight and all attempts significantly increased with more attempts (all p < 0.05). At T2, 56% required fewer attempts to achieve best values, but 32% required more attempts, indicating that the number of attempts required was inconsistent between test days. CONCLUSION: It is likely that at least ten attempts (best two within < 10% variability) is required to achieve best and reliable MIP/MEP in children with CF. A larger sample size in children with CF and various conditions is required to consolidate these findings.

Determinants and Follow-up of Lung Function Data from a Predominantly First Nations Cohort of Adults Referred to Specialist Respiratory Outreach Clinics in Regional and Remote Queensland.

PURPOSE: Northern Territory (NT)-based clinical service data suggest substantial lung function impairment amongst First Nations adults as young as 18-40 years. Our objectives were to describe the burden of disease and lung function of adults living in regional-remote Queensland, identify determinants of lung function, and evaluate the impact of a specialist respiratory outreach service on lung function. METHODS: Retrospective 8-year cohort study (February 2012-March 2020) of 1113 First Nations Australian adults (and 648 non-First Nations adults) referred to respiratory outreach clinics in regional-remote Queensland. RESULTS: In the combined cohort, the forced expiratory volume in 1 s (FEV1) was clinically abnormal for 54% of First Nations patients (51% of non-First Nations patients), forced vital capacity (FVC) for 46% (36%), FEV1/FVC% for 30% (36%), and gas diffusing capacity (DLCO) for 44% (37%). A respiratory diagnosis was assigned by a respiratory physician in 78% of First Nations (76% non-First Nations) patients. Smoking, household smoke exposure, underweight BMI, and respiratory disease were associated with reduced lung function. In the 40% of patients (709/1765) followed up, FEV1 and FVC significantly improved (mean change: zFEV1 = 0.15 [95% CI 0.10-0.20]; zFVC = 0.25 [0.20, 0.31]), and FEV1/FVC% significantly reduced (mean = - 0.10 [95%CI - 0.07 to - 0.03]), with no significant change in DLCO. Patients with COPD had lower FEV1 improvement, whilst underweight and obese patients had lower FVC improvement. CONCLUSION: Regional-remote First Nations adult Queenslanders have higher lung function than previously reported, with no lung function decline observed at follow-up visit, including for those with respiratory disease.

Global Lung Function Initiative-2012 'other/mixed' spirometry reference equation provides the best overall fit for Australian Aboriginal and/or Torres Strait Islander children and young adults.

BACKGROUND AND OBJECTIVE: Ethnic-specific reference equations are recommended when performing spirometry. In the absence of appropriate reference equations for Australian Aboriginal and/or Torres Strait Islanders (Indigenous), we determined whether any of the existing Global Lung Function Initiative (GLI)-2012 equations were suitable for use in Indigenous children/young adults. METHODS: We performed spirometry on 1278 participants (3-25 years) who were identified as Aboriginal, Torres Strait Islander or 'both'. Questionnaires and medical records were used to identify 'healthy' participants. GLI2012_DataConversion software was used to apply the 'Caucasian', 'African-American' and 'other/mixed' equations. RESULTS: We included 930 healthy participants. Mean z-scores for forced expiratory volume in 1 s (FEV1 ) and forced vital capacity (FVC) were lower than the Caucasian predicted values (range: -0.53 to -0.60) and higher than African-American (range: 0.70 to 0.78) but similar to other/mixed (range: 0.00 to 0.08). The distribution of healthy participants around the upper and lower limits of normal (~5%) fit well for the other/mixed equation compared to the Caucasian and African-American equations. CONCLUSION: Of the available GLI-2012 reference equations, the other/mixed reference equation provides the best overall fit for Indigenous Australian children and young adults (3-25 years). Healthy data from additional communities and adults around Australia will be required to confirm generalizability of findings.

Culturally Appropriate Outreach Specialist Respiratory Medical Care Improves the Lung Function of Children in Regional and Remote Queensland.

BACKGROUND AND OBJECTIVES: Indigenous Respiratory Outreach Care (IROC) is a culturally appropriate specialist respiratory service established to deliver multidisciplinary respiratory care to regional and remote Queensland communities. Our objective was to evaluate the impact of an outreach specialist respiratory service on the spirometry of children attending IROC clinics, particularly Indigenous children with asthma and bronchiectasis. METHODS: Retrospective single-arm cohort study of 189 children who performed spirometry at twelve sites across regional and remote Queensland between October 2010 and December 2017. Each child's baseline spirometry was compared to their best spirometry at follow-up visit occurring within (1) 12 months of their most recent visit with at least 12 months of specialist care and; (2) each year of their first 3 years of care. RESULTS: Forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) z-scores improved significantly across the whole group from baseline to follow-up (change in z-scores (Δz) of FEV1 = 0.38, 95% CI 0.22, 0.53; ΔzFVC = 0.36, 95% CI 0.21, 0.51). In subgroup analyses, lung function significantly improved in Indigenous children (n = 141, ΔzFEV1 = 0.37, 95% CI 0.17, 0.57; ΔzFVC = 0.36, 95% CI 0.17, 0.55) including those with asthma (n = 117, ΔzFEV1 = 0.41, 95% CI 0.19, 0.64; ΔzFVC = 0.46, 95% CI 0.24, 0.68) and bronchiectasis (n = 38, ΔzFEV1 = 0.33, 95% CI 0.07, 0.59; ΔzFVC = 0.26, 95% CI - 0.03, 0.53). Significant improvements in FEV1 and FVC were observed within the first and second year of follow-up for Indigenous children, but not for non-Indigenous children. CONCLUSION: The IROC model of care in regional and remote settings leads to significant lung function improvement in Indigenous children with asthma and bronchiectasis.

Respiratory health profile of Indigenous Australian children and young adults.

AIM: National data report respiratory illness to be the most common chronic illness in Australian Indigenous people aged <35 years but multi-centre data on specific diseases is sparse. Respiratory health is now known to be an independent predictor of future all-cause mortality and cardiovascular disease. We aimed to describe the respiratory health profile (clinical and spirometry data) of randomly recruited Indigenous Australian children and young adults from several sites. METHODS: As part of the Indigenous Respiratory Reference Values study, 1278 Australian Indigenous children and young adults (aged 3-25 years) were recruited from nine communities (Queensland, n = 8; Northern Territory, n = 1). Self-reported and medical records were used to ascertain respiratory history. Participants were classified as 'healthy' if there was no current/previous respiratory disease history. Spirometry was performed on all participants and assessed according to forced expiratory volume at 1 s impairment. RESULTS: Medical history data were available for 1245 (97.4%) and spirometry for 1106 participants (86.5%). Asthma and bronchitis were the most commonly reported respiratory conditions (city/regional 19.5% and rural/remote 16.8%, respectively). Participants with a history of any respiratory disease or those living in rural/remote communities had lower lung function compared to the 'healthy' group. Almost 52.0% of the entire cohort had mild-moderate forced expiratory volume at 1 s impairment (47.7% in 'healthy' group, 58.5% in 'respiratory history' group). CONCLUSION: The high prevalence of poor respiratory health among Indigenous Australian children/young adults places them at increased risk of future all-cause mortality and cardiovascular disease. Respiratory assessments including spirometry should be part of the routine evaluation of Indigenous Australians.

How does parent/self-reporting of common respiratory conditions compare with medical records among Aboriginal and Torres Strait Islander (Indigenous) children and young adults?

AIM: Self-reporting and/or data from medical records are frequently used in studies to ascertain health history. Data on the discrepancies between these information sources is lacking for Indigenous Australians. This study reports such data for selected respiratory and atopic conditions common among Indigenous Australians. METHODS: Data were extracted from the Indigenous respiratory reference value study, a multicentre cross-sectional study of Indigenous children and young adults (3-25 years) between June 2015 and November 2017. Only those living in rural/remote regions were included. Self-reported history was collected from parents (if participants <18 years) or participants. Medical records were manually reviewed. Participants with incomplete data (missing self-reported and/or medical record information) were excluded. Agreement between sources was examined using Cohen's kappa. RESULTS: Of 1097 participants, 889 (97.1% <18 years) had sufficient self-reported and medical record histories for comparison. Asthma was self-reported by 15.7% of participants and was reported in medical records for 10.3% (κ = 0.53, 95% confidence interval (CI) 0.45-0.61). For bronchiectasis, the reported rates were 1.5 and 0.7% (κ = 0.52, 95% CI 0.25-0.80), pneumonia 1.1 and 5.8% (κ = 0.15, 95% CI 0.02-0.27), allergic rhinitis 6.6 and 0.6% (κ = 0.05, 95% CI -0.03, 0.13) and eczema 5.8 and 6.2% (κ = 0.30, 95% CI 0.18-0.42). CONCLUSIONS: Within our cohort, agreement was moderate for asthma and bronchiectasis, fair for eczema and poor for pneumonia and allergic rhinitis. These results highlight the challenges associated with how best to obtain an accurate health history within Australian Indigenous rural/remote communities. Generalisability of findings and contributions of poor health knowledge and/or poor medical record documentation need further exploration.

Spirometry reference values in Indigenous Australians: a systematic review.

OBJECTIVES: To evaluate published spirometry data for Australian Aboriginal and Torres Strait Islander (Indigenous) peoples to determine (i) whether their ethnicity influenced spirometry results; and (ii) if any reliable spirometry reference values exist for Indigenous Australians. STUDY DESIGN: Systematic review of published and grey literature. DATA SOURCES: PubMed and Cochrane Library databases, references of included articles and appropriate grey literature. Last searches were conducted in April 2016. STUDY SELECTION: We included any study that performed spirometry on healthy Indigenous Australians and compared their results with those from people of European ancestry. Two authors independently screened titles and abstracts and then reviewed potentially relevant full-text articles for possible inclusion. We used PRISMA systematic review reporting methods to collate data. DATA SYNTHESIS: Of a possible 125 studies, 18 full-text articles were reviewed, but only nine fulfilled the inclusion criteria. None specified Torres Strait Islander inclusion. All studies reported lower spirometry values (as much as 30% lower) for Aboriginal people compared with non-Indigenous people. Five studies developed spirometry reference values for Indigenous Australians; however, none adhered to all participant inclusion and exclusion criteria outlined by the American Thoracic Society and European Respiratory Society. Hence, reported results and subsequent reference values may not be a true representation of spirometry values in healthy Indigenous people. CONCLUSIONS: The lower spirometry values reported for Indigenous Australians may be due to study limitations. Furthermore, there are currently no reliable spirometry reference values for Indigenous Australians that adhere to current guidelines. Developing a set of Indigenous Australian reference values will improve the accuracy of test interpretation and aid in the diagnosis of respiratory disease in this population.

Clinical determinants for State-Trait Anxiety Inventory of the parents of children with respiratory problems.

BACKGROUNDS: Understanding factors associated with anxiety of parents/carers of children with respiratory problems is clinically important yet there is relative paucity of data. In 106 children seen in the respiratory clinic of a pediatric hospital, we evaluated (a) the determinants for parental anxiety and (b) whether the anxiety scores correlate with quality-of-life (QoL) scores in the subset with chronic cough. METHODS: We opportunistically re-analyzed data of our main study that examined the benefits of using spirometry for pediatric respiratory consultation where parents completed an anxiety questionnaire (State-Trait Anxiety Inventory, STAI) pre- and postconsultation. A subset (children with chronic cough) also completed the parent-proxy quality-of-life (PC-QoL) tool. We computed the association between clinical characteristics and anxiety scores using multivariable regression and between the two patient-reported outcome measures using Spearman's correlation. RESULTS: The majority of parents/carers were women (n = 89, 84%). Most children (mean age = 10.9 years, SD = 3.7 years) were previously seen at the clinic (n = 67, 63.2%). In multivariate regression, parental anxiety score was significantly associated with reported presence of cough [coefficient ß = 17.31 (95% confidence interval 9.62, 25.1)] and lower forced expiratory volume in first second (FEV1 )/forced vital capacity (FVC) [-3.88 (-7.05, -0.71)] at preconsultation, but associated with cough only [coefficient ß = 12.04 (5.24, 18.84)] at postconsultation, all p < .05. STAI strongly correlated with PC-QoL scores at pre- but only modestly at postconsultation (rs = -.63 and -.39, respectively, p < .05). CONCLUSION: Parental anxiety levels of children attending respiratory clinics are influenced by the presence of cough and low FEV1 /FVC of their child and are associated with poorer QoL. These highlight the need for on-going research to reduce parental anxiety focusing on cough and lung function indices.

Developing Fractional Exhaled Nitric Oxide Predicted and Upper Limit of Normal Values for a Disadvantaged Population.

BACKGROUND: Fractional exhaled nitric oxide (Feno), used as a biomarker, is influenced by several factors including ethnicity. Normative data are essential for interpretation, and currently single cutoff values are used in children and adults. RESEARCH QUESTION: Accounting for factors that influence Feno, (1) what are appropriate predicted and upper limit of normal (ULN) Feno values in an underserved population (First Nations Australians), (2) how do these values compare with age-based interpretive guidelines, and (3) what factors influence Feno and what is the size of the effect? STUDY DESIGN AND METHODS: Feno data of First Nations Australians (age < 16 years, n = 862; age ≥ 16 years, n = 348) were obtained. Medical history using participant questionnaires and medical records were used to define healthy participants. Flexible regression using spline functions, as used by the Global Lung Function Initiative, were used to generate predicted and ULN values. RESULTS: Look-up tables for predicted and ULN values using age (4-76 years) and height (100-200 cm) were generated and are supplied with a calculator for clinician use. In healthy First Nations children (age < 18 years), ULN values ranged between 25 and 60 parts per billion (ppb) when considering only biologically plausible age and height combinations. For healthy adults, ULN values ranged between 39 and 88 ppb. Neither the current Feno interpretation guidelines, nor the currently recommended cutoff of 50 ppb for First Nations children 16 years of age or younger were appropriate for use in this cohort. Our modelling revealed that predicted and ULN values of healthy participants varied nonlinearly with age and height. INTERPRETATION: Because single pediatric, adult, or all-age Feno cutoff values used by current interpretive guidelines to define abnormality fail to account for factors that modify Feno values, we propose predicted and ULN values for First Nations Australians 4 to 76 years of age. Creating age- and height-adjusted predicted and ULN values could be considered for other ethnicities.

Does routine spirometry impact on clinical decisions and patient-related outcome measures of children seen in respiratory clinics: an open-label randomised controlled trial.

INTRODUCTION: There is limited evidence on the efficacy of using spirometry routinely in paediatric practice for improving outcomes. OBJECTIVE: To determine whether the routine use of spirometry alters clinical decisions and patient-related outcome measures for children managed by respiratory paediatricians. METHODS: We undertook a parallel open-label randomised controlled trial involving children (aged 4-18 years) able to perform spirometry in a specialist children's hospital in Australia. Children were randomised to either routine use of spirometry (intervention) or clinical review without use of spirometry (control) for one clinic visit. The primary outcomes were the (a) proportion of children with 'any change in clinical decisions' and (b) 'change score' in clinical decisions. Secondary outcomes were change in patient-related outcome measures assessed by State-Trait Anxiety Inventory (STAI) and Parent-Proxy QoL questionnaire for paediatric chronic cough (PC-QoL). RESULTS: Of 136 eligible children, 106 were randomised. Compared with controls, the intervention group had significantly higher proportion of children with 'any change in clinical decisions' (n=54/54 (100%) vs n=34/52 (65.4%), p<0.001) and higher clinical decision 'change score' (median=2 (IQR 1-4) vs 1 (0-2), p<0.001). Also, improvement was significantly greater in the intervention group for overall STAI score (median=-5 (IQR -10 to -2) vs -2.5 (-8.5, 0), p=0.021) and PC-QoL social domain (median=3 (IQR 0 to 5) vs 0 (-1, 1), p=0.017). CONCLUSION: The routine use of spirometry in children evaluated for respiratory issues at clinical outpatient review is beneficial for optimising clinical management and improving parent psychosocial well-being. REGISTRATION: Australia and New Zealand Clinical Trials Registry ACTRN12619001686190.

The effect of early childhood respiratory infections and pneumonia on lifelong lung function: a systematic review.

Early childhood respiratory infections, including pneumonia, are an important global public health issue, with more than 40 million annual cases resulting in approximately 650 000 deaths. A growing number of published studies have examined the effects of early childhood lower respiratory tract infections (LRTIs) or pneumonia on lung function, particularly as part of large early-life exposure studies. To our knowledge, there is no published systematic review of these data. We searched PubMed, Embase, and Web of Science for studies published between database inception and May 12, 2022. Case-control, cohort, and cross-sectional studies were included if they reported forced expiratory volume in 1 s (FEV1) or forced vital capacity (FVC) values of participants older than 5 years. Article titles and abstracts were screened in Rayyan before retrieval, assessment, and data extraction of the full text. Primary outcome measures were differences in mean FEV1 or FVC values between exposed groups (ie, children aged ≤5 years with LRTIs) and non-exposed groups. This study is registered with PROSPERO, CRD42021265295. Database searches yielded 3070 articles, and 14 studies were included in this systematic review, providing a total of 23 276 participants, including 9969 children and 13 307 adults. Eight of 14 articles reported significant reductions in FEV1 values, and six of 12 studies reported reductions in FVC values in children and adults with a history of early childhood LRTIs or pneumonia, compared with unexposed controls (p<0·05). Most studies reporting reductions in lung function described deficits consistent with a restrictive spirometry pattern. Only two of 14 studies reported data from low-income and middle-income countries or disadvantaged populations in middle-income and high-income countries, and there were scarce data available on the effect of LRTI severity and recurrence on lung function. LRTIs in early childhood could be associated with a restrictive spirometry pattern in later childhood and adulthood. Data are needed from low-income and middle-income nations, and from disadvantaged populations in middle-income and high-income countries in which early childhood respiratory infection burden is disproportionately high. Data are also needed on the effect of LRTI severity and recurrence on future lung function.

Does the routine use of spirometry improve clinical outcomes in children?-A systematic review.

Spirometry provides a quantitative measure of lung function and its use is recommended as an adjunct to enhance pediatric respiratory healthcare in many clinical practice guidelines. However, there is limited evidence confirming the benefits (or otherwise) of using spirometry from either clinician or patient perspectives. This systematic review aimed to determine the impact of spirometry on change in clinical decision making and patient-reported outcome measures. We searched PubMed, Embase, Cochrane Central Register of Controlled Trials, www.clinicaltrials.gov, and World Health Organization International Clinical Trials Registry Platform, from inception to July 2021. We included randomized controlled trials (RCTs) comparing the use versus non-use of spirometry during standard clinical review in children aged <18 years with respiratory problems in clinics. We used Cochrane methodology. The search identified 3475 articles; 8 full-text articles were reviewed but only 1 study fulfilled the inclusion criteria. The single study involved two cluster RCTs of spirometry for children with asthma in general practice. The included study did not find any significant intergroup difference at the 12-month follow-up for asthma-related quality-of-life and clinical endpoints. However, the findings were limited by methodological weaknesses and high risks of bias. With a paucity of data, the clinical benefits of spirometry remain unclear. Thus, there is a clear need for RCTs that provide high-quality evidence to support the routine use of spirometry in children with suspected or known lung disease. Pending the availability of better evidence, we recommend that clinicians adhere to the current clinical practice recommendations.

Pulmonary function of children with tracheomalacia and associated clinical factors.

OBJECTIVES: Spirometry is easily accessible yet there is limited data in children with tracheomalacia. Availability of such data may inform clinical practice. We aimed to describe spirometry indices of children with tracheomalacia, including Empey index and flow-volume curve pattern, and determine whether these indices relate with bronchoscopic features. METHODS: From the database of children with tracheomalacia diagnosed during 2016-2019, we reviewed their flexible bronchoscopy and spirometry data in a blinded manner. We specially evaluated several spirometry indices and tracheomalacia features (cross-sectional lumen reduction, malacic length, and presence of bronchomalacia) and determined their association using multivariable regression. RESULTS: Of 53 children with tracheomalacia, the mean (SD) peak expiratory flow (PEF) was below the normal range [68.9 percent of predicted value (23.08)]. However, all other spirometry parameters were within normal range [Z-score forced expired volume in 1 s (FEV1 ) = -1.18 (1.39), forced vital capacity (FVC) = -0.61 (1.46), forced expiratory flow between 25% and 75% of vital capacity​​​​​​ (FEF25%-75% ) = -1.43 (1.10), FEV1 /FVC = -1.04 (1.08)], Empey Index = 8.21 (1.59). The most common flow-volume curve pattern was the "knee" pattern (n = 39, 73.6%). Multivariable linear regression identified the presence of bronchomalacia was significantly associated with lower flows: FEV1 [coefficient (95% CI) -0.78 (-1.54, -0.02)], FEF25%-75% [-0.61 (-1.22, 0)], and PEF [-12.69 (-21.13, -4.25)], all p ≤ 0.05. Other bronchoscopic-defined tracheomalacia features examined (cross-sectional lumen reduction, malacic length) were not significantly associated with spirometry indices. CONCLUSION: The "knee" pattern in spirometry flow-volume curve is common in children with tracheomalacia but other indices, including Empey index, cannot be used to characterize tracheomalacia. Spirometry indices were not significantly associated with bronchoscopic tracheomalacia features but children with tracheobronchomalacia have significantly lower flow than those with tracheomalacia alone.

The 'knee' pattern in spirometry flow-volume curves in children: Does it relate to tracheomalacia?

BACKGROUND: There is little data on patterns of spirometry curves in children with tracheomalacia but convex inflection on flow-volume curves (identified as the 'knee') is thought to represent tracheomalacia. OBJECTIVES: To determine (a) the prevalence of tracheomalacia in children with the 'knee' pattern on spirometry, and (b) whether spirometry parameters and visual characteristics of the 'knee' can identify presence/absence or severity of tracheomalacia. PATIENTS/METHODS: We reviewed the spirometry undertaken at Queensland Children's Hospital between 2016 and 2019 and retrieved spirometry with the 'knee' pattern in the flow-volume curves. Flexible bronchoscopy videos of these children were reviewed for tracheomalacia diagnosis and severity in a blinded manner. We also evaluated several 'knee' characteristics (onset of inflection, angle of inflection, a scoop before plateau, plateau progression), spirometry parameters and tracheomalacia severity. RESULTS: Of the 78 children with the 'knee', 51 (65.4%) had tracheomalacia. Spirometry values were significantly lower in those with tracheomalacia, compared to those without (predicted FEV1 = 86.1% vs 99.9%, FVC = 95.1% vs 104%, FEF25-75% = 68.6% vs 89.6%, all p < 0.02). A scoop before plateau was significantly associated with tracheomalacia (66.7% vs 40.7%, p = 0.03). There was no significant difference in spirometry parameters or the 'knee' characteristics between children with mild versus moderate-to-severe tracheomalacia. CONCLUSION: Most but not all children with the 'knee' pattern have flexible bronchoscopy-defined tracheomalacia. Those with tracheomalacia had lower spirometry values and the presence of a scoop before plateau was the most characteristic feature. A prospective longitudinal study is required to determine the diagnostic value of spirometry flow-volume curve characteristics in children.

Reducing exacerbations in children and adults with primary ciliary dyskinesia using erdosteine and/or azithromycin therapy (REPEAT trial): study protocol for a multicentre, double-blind, double-dummy, 2×2 partial factorial, randomised controlled trial.

INTRODUCTION: Primary ciliary dyskinesia (PCD) is a rare, progressive, inherited ciliopathic disorder, which is incurable and frequently complicated by the development of bronchiectasis. There are few randomised controlled trials (RCTs) involving children and adults with PCD and thus evidence of efficacy for interventions are usually extrapolated from people with cystic fibrosis. Our planned RCT seeks to address some of these unmet needs by employing a currently prescribed (but unapproved for long-term use in PCD) macrolide antibiotic (azithromycin) and a novel mucolytic agent (erdosteine). The primary aim of our RCT is to determine whether regular oral azithromycin and erdosteine over a 12-month period reduces acute respiratory exacerbations among children and adults with PCD. Our primary hypothesis is that: people with PCD who regularly use oral azithromycin and/or erdosteine will have fewer exacerbations than those receiving the corresponding placebo medications. Our secondary aims are to determine the effect of the trial medications on PCD-specific quality-of-life (QoL) and other clinical outcomes (lung function, time-to-next exacerbation, hospitalisations) and nasopharyngeal bacterial carriage and antimicrobial resistance. METHODS AND ANALYSIS: We are currently undertaking a multicentre, double-blind, double-dummy RCT to evaluate whether 12 months of azithromycin and/or erdosteine is beneficial for children and adults with PCD. We plan to recruit 104 children and adults with PCD to a parallel, 2×2 partial factorial superiority RCT at five sites across Australia. Our primary endpoint is the rate of exacerbations over 12 months. Our main secondary outcomes are QoL, lung function and nasopharyngeal carriage by respiratory bacterial pathogens and their associated azithromycin resistance. ETHICS AND DISSEMINATION: Our RCT is conducted in accordance with Good Clinical Practice and the Australian legislation and National Health and Medical Research Council guidelines for ethical conduct of Research, including that for First Nations Australians. TRIAL REGISTRATION NUMBER: ACTRN12619000564156.

How do Cormic Index profiles contribute to differences in spirometry values between White and First Nations Australian children?

BACKGROUND: Spirometry values of First Nations Australian children are lower than White children. One explanation relates to differences in the sitting-height/standing-height ratio (Cormic Index), as this accounts for up to half the observed differences in spirometry values between White children and other ethnicities. We investigated whether the Cormic Index of First Nations children differs from White children and if this explains the lower spirometry values of First Nations children. METHODS: First Nations children (n = 619) aged 8-16 years were recruited from nine Queensland communities. Their spirometry and Cormic Index data were compared to that of White children (n = 907) aged 8-16 years from the NHANES III dataset. RESULTS: FEV1 and FVC of First Nations children was 8% lower for children aged 8-11.9 years and 9%-10% lower for children aged 12-16 years. The Cormic Index was statistically lower in the First Nations 8-11.9 years group (median = 0.515, interquartile range [IQR]: 0.506-0.525) compared with White children (0.519, IQR: 0.511-0.527), and this difference was greater in the 12-16 years group (0.505, IQR: 0.492-0.516; 0.520, IQR: 0.510-0.529). Adjusting for age, sex, and standing height, lower Cormic Index of First Nations children accounts for 14% (95% confidence interval [CI]: 7%-21%) of FEV1 and 15% (95% CI: 8%-21%) of FVC differences in the younger group, and 26% (95% CI: 16%-37%) of FEV1 and 31% (95% CI: 19%-42%) of FVC differences in the older group. CONCLUSION: Ethnic differences in Cormic Index partly account for why healthy First Nations Australian children have lower spirometry values than White children. As childhood spirometry values impact adult health, other contributing factors require attention.

Impact of using spirometry on clinical decision making and quality of life in children: protocol for a single centre randomised controlled trial.

INTRODUCTION: Although spirometry has been available for decades, it is underused in paediatric practice, other than in specialist clinics. This is unsurprising as there is limited evidence on the benefit of routine spirometry in improving clinical decision making and/or outcomes for children. We hypothesised that using spirometry for children being evaluated for respiratory diseases impacts on clinical decision making and/or improves patient-related outcome measures (PROMs) and/or quality of life (QoL), compared with not using spirometry. METHODS AND ANALYSIS: We are undertaking a randomised controlled trial (commenced in March 2020) that will include 106 children (aged 4-18 years) recruited from respiratory clinics at Queensland Children's Hospital, Australia. Inclusion criteria are able to perform reliable spirometry and a parent/guardian who can complete questionnaire(s). Children (1:1 allocation) are randomised to clinical medical review with spirometry (intervention group) or without spirometry (control group) within strata of consultation status (new/review), and cough condition (present/absent). The primary outcome is change in clinical decision making. The secondary outcomes are change in PROM scores, opinions regarding spirometry and degree of diagnosis certainty. Intergroup differences of these outcomes will be determined by χ2 test or unpaired t-test (or Mann-Whitney if not normally distributed). Change in outcomes within the control group after review of spirometry will also be assessed by McNemar's test or paired t-test/Wilcoxon signed-rank test. ETHICS AND DISSEMINATION: The Human Research Ethics Committee of the Queensland Children's Hospital approved the study. The trial results will be disseminated through conference presentations, teaching avenues and publications. TRIAL REGISTRATION NUMBER: ACTRN12619001686190; Pre-results.

Associations between lung function and future cardiovascular morbidity and overall mortality in a predominantly First Nations population: a cohort study.

BACKGROUND: Spirometric lung function impairment is an independent predictor of respiratory and cardiovascular disease, and mortality across a broad range of socioeconomic backgrounds and environmental settings. No contemporary studies have explored these relationships in a predominantly regional/remote First Nations population, whose health outcomes are worse than for non-First Nations populations, and First Nations people living in urban centres. METHODS: This was a retrospective cohort study of 1,734 adults (1,113 First Nations) referred to specialist respiratory outreach clinics in the state of Queensland, Australia from February 2012 to March 2020. Regression modelling was used to test associations between lung function and mortality and cardiovascular disease. FINDINGS: At the time of analysis (August 2020), 189 patients had died: 88 (47%) from respiratory causes and 38 (20%) from cardiovascular causes. When compared to patients with forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) Z-scores of >0 to -1, patients with Z-scores <-1 were at elevated mortality risk (HR=3•2, 95%CI 1•4-7•4; HR=2•6, 95%CI 1•3-5•1), and elevated cardiovascular disease risk (OR=1•5, 95%CI 1•1-2•2; OR=1•6, 95%CI 1•2-2•3). FEV1/FVC% Z-scores <-1 were associated with increased overall mortality (HR=1•6, 95%CI 1•1-2•3), but not cardiovascular disease (OR=1•1, 95%CI 0•8-1•4). These associations were not affected by First Nations status. INTERPRETATION: Reduced lung function even within the clinically normal range is associated with increased mortality, and cardiovascular disease in First Nations Australians. These findings highlight the importance of lung function optimisation and inform the need for future investment to improve outcomes in First Nations populations. FUNDING: None.