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Aims: The aim was to evaluate whether standardised exercise performance during the incremental shuttle walk test (ISWT) can be used to assess disease severity in children and young people (CYP) with chronic conditions, through (1) identifying the most appropriate paediatric normative reference equation for the ISWT, (2) assessing how well CYP with haemophilia and cystic fibrosis (CF) perform against the values predicted by the best fit reference equation and (3) evaluating the association between standardised ISWT performance and disease severity., Methods: A cross-sectional analysis was carried out using existing data from two independent studies (2018-2019) at paediatric hospitals in London,UK. CYP with haemophilia (n=35) and CF (n=134) aged 5-18 years were included. Published reference equations for standardising ISWT were evaluated through a comparison of populations, and Bland-Altman analysis was used to assess the level of agreement between distances predicted by each equation. Associations between ISWT and disease severity were assessed with linear regression., Results: Three relevant reference equations were identified for the ISWT that standardised performance based on age, sex and body mass index (Vardhan, Lanza, Pinho). A systematic proportional bias of standardised ISWT was observed in all equations, most pronounced with Vardhan and Lanza; the male Pinho equation was identified as most appropriate. On average, CYP with CF and haemophilia performed worse than predicted by the Pihno equation, although the range was wide. Standardised ISWT, and not ISWT distance alone, was significantly associated with forced expiratory volume in 1 s in CYP with CF. Standardised ISWT in CYP with haemophilia was slightly associated with haemophilia joint health score, but this was not significant., Conclusions: ISWT performance may be useful in a clinic to identify those with worsening disease, but only when performance is standardised against a healthy reference population. The development of validated global reference equations is necessary for more robust assessment., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Cystic fibrosis (CF) is commonly characterised by thick respiratory mucus. From diagnosis, people with CF are prescribed daily physiotherapy, including airway clearance techniques (ACTs). ACTs consume a large proportion of treatment time, yet the efficacy and effectiveness of ACTs are poorly understood. This study aimed to evaluate associations between the quality and quantity of ACTs and lung function in children and young people with CF., Methods: Project Fizzyo, a longitudinal observational cohort study in the UK, used remote monitoring with electronic pressure sensors attached to four different commercial ACT devices to record real-time, breath-by-breath pressure data during usual ACTs undertaken at home over 16 months in 145 children. ACTs were categorised either as conformant or not with current ACT recommendations based on breath pressure and length measurements, or as missed treatments if not recorded. Daily, weekly and monthly associations between ACT category and lung function were investigated using linear mixed effects regression models adjusting for clinical confounders., Results: After exclusions, 45 224 ACT treatments (135 individuals) and 21 069 days without treatments (141 individuals) were analysed. The mean±sd age of participants was 10.2±2.9 years. Conformant ACTs (21%) had significantly higher forced expiratory volume in 1 s (FEV 1 ) (mean effect size 0.23 (95% CI 0.19-0.27) FEV 1 % pred per treatment) than non-conformant (79%) or missed treatments. There was no benefit from non-conformant or missed treatments and no significant difference in FEV 1 between them (mean effect size 0.02 (95% CI -0.01-0.05) FEV 1 % pred per treatment)., Conclusions: ACTs are beneficial when performed as recommended, but most people use techniques that do not improve lung function. Work is needed to monitor and improve ACT quality and to increase the proportion of people doing effective airway clearance at home., Competing Interests: Conflicts of interest: G. Davies reports personal UKRI fellowship, UKRI and NIHR grants, speaker honoraria from Chiesi Ltd, and speaker honoraria, consulting fees and participation on a board from Vertex Pharmaceuticals, outside the submitted work. S. Stanojevic reports consulting fees from Chiesi Ltd, speaker fees from Vyaire Medical, participation on a board for Ndd technologies, and leadership role from the European Respiratory Society and the American Thoracic Society, outside the submitted work. The remaining authors have no potential competing interests to disclose., (Copyright ©The authors 2023.)

Children and young people with CF (CYPwCF) get advice about using positive expiratory pressure (PEP) or oscillating PEP (OPEP) devices to clear sticky mucus from their lungs. However, little is known about the quantity (number of treatments, breaths, or sets) or quality (breath pressures and lengths) of these daily airway clearance techniques (ACTs) undertaken at home. This study used electronic pressure sensors to record real time breath-by-breath data from 145 CYPwCF (6-16y) during routine ACTs over 2 months. ACT quantity and quality were benchmarked against individual prescriptions and accepted recommendations for device use. In total 742,084 breaths from 9,081 treatments were recorded. Individual CYPwCF maintained consistent patterns of ACT quantity and quality over time. Overall, 60% of CYPwCF did at least half their prescribed treatments, while 27% did fewer than a quarter. About 77% of pre-teens did the right number of daily treatments compared with only 56% of teenagers. CYPwCF usually did the right number of breaths. ACT quality (recommended breath length and pressure) varied between participants and depended on device. Breath pressures, lengths and pressure-length relationships were significantly different between ACT devices. PEP devices encouraged longer breaths with lower pressures, while OPEP devices encouraged shorter breaths with higher pressures. More breaths per treatment were within advised ranges for both pressure and length using PEP (30-31%) than OPEP devices (1-3%). Objective measures of quantity and quality may help to optimise ACT device selection and support CYPwCF to do regular effective ACTs., Competing Interests: Conflict of interest statement All authors declare that they have no conflicts of interest., (Copyright © 2022. Published by Elsevier B.V.)

Introduction: Daily physiotherapy is believed to mitigate the progression of cystic fibrosis (CF) lung disease. However, physiotherapy airway clearance techniques (ACTs) are burdensome and the evidence guiding practice remains weak. This paper describes the protocol for Project Fizzyo, which uses innovative technology and analysis methods to remotely capture longitudinal daily data from physiotherapy treatments to measure adherence and prospectively evaluate associations with clinical outcomes., Methods and Analysis: A cohort of 145 children and young people with CF aged 6-16 years were recruited. Each participant will record their usual physiotherapy sessions daily for 16 months, using remote monitoring sensors: (1) a bespoke ACT sensor, inserted into their usual ACT device and (2) a Fitbit Alta HR activity tracker. Real-time breath pressure during ACTs, and heart rate and daily step counts (Fitbit) are synced using specific software applications. An interrupted time-series design will facilitate evaluation of ACT interventions (feedback and ACT-driven gaming). Baseline, mid and endpoint assessments of spirometry, exercise capacity and quality of life and longitudinal clinical record data will also be collected.This large dataset will be analysed in R using big data analytics approaches. Distinct ACT and physical activity adherence profiles will be identified, using cluster analysis to define groups of individuals based on measured characteristics and any relationships to clinical profiles assessed. Changes in adherence to physiotherapy over time or in relation to ACT interventions will be quantified and evaluated in relation to clinical outcomes., Ethics and Dissemination: Ethical approval for this study (IRAS: 228625) was granted by the London-Brighton and Sussex NREC (18/LO/1038). Findings will be disseminated via peer-reviewed publications, at conferences and via CF clinical networks. The statistical code will be published in the Fizzyo GitHub repository and the dataset stored in the Great Ormond Street Hospital Digital Research Environment., Trial Registration Number: ISRCTN51624752; Pre-results., Competing Interests: Competing interests: GD reports personal lecture fees from Chiesi Limited for an invited talk on Project Fizzyo at an educational event. All other authors report no conflicts of interest in relation to this protocol., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)