Looking beyond LCI: Multiple breath washout phase III slope derived indices and their application in chronic respiratory disease in children.

The multiple breath washout (MBW) test is widely reported in the context of Lung Clearance Index (LCI). LCI reflects global ventilation inhomogeneity but does not provide information regarding the localization of disease along the respiratory tree. The MBW-derived normalized phase III slope (SnIII) indices (Scond and Sacin), instead, can distinguish between convective-dependent and diffusion-convection-dependent ventilation inhomogeneity considered to occur within the conductive and acinar airways, respectively. In cystic fibrosis, Scond tends to become abnormal even earlier than LCI and spirometry. The value of Scond and Sacin in clinical practice has been recently explored in other respiratory conditions, including asthma, primary ciliary dyskinesia, bronchopulmonary dysplasia, bronchiolitis obliterans, and sickle cell disease. In this narrative review we offer an overview on the theoretical background, potentialities, and limitations of SnIII analysis in children, including challenges and feasibility aspects. Moreover, we summarize current evidence on the use of SnIII-derived indices across different groups of pediatric chronic respiratory disease and we highlight the gaps in knowledge that need to be addressed in future studies.

Retrospective analysis of referrals for hypoxic challenge testing in children born preterm.

INTRODUCTION: Children with a history of bronchopulmonary dysplasia (BPD) may be at risk of hypoxaemia at altitude, such as during air travel. We have performed preflight hypoxic challenge testing (HCT) since 2006, incorporating British Thoracic Society (BTS) guidance since 2011, to determine which children may require oxygen during air travel. AIMS: We aimed to compare the outcome of HCTs in children with a history of BPD who met the 2011 BTS criteria and those who did not and, in addition to this, to interrogate the data for factors that may predict the outcome of HCT in this population. METHODS: We performed a retrospective analysis of data from HCTs of children with a history of BPD referred 2006-2020. Cases were excluded if the patient had a respiratory comorbidity, was still on oxygen therapy, if the test was a repeat or if the clinical record was incomplete. Descriptive and univariate analysis of the data was performed, and a binary logistic regression model was fitted. RESULTS: There were 79 HCTs, of which 24/79 (30%) did not meet BTS 2011 guidelines referral criteria. The analysis showed a greater proportion of desaturation in the group that did not meet criteria: 46% vs 27% (no statistical significance). Baseline oxygen saturations were higher in those who did not require oxygen during HCT and this variable was significant when adjusted for confounders. CONCLUSIONS: This study found that the current criteria for referral for preflight testing may incorrectly identify those most at risk and highlights the need for further investigation to ensure those most at risk are being assessed prior to air travel.

"You're on mute!" Does pediatric CF home spirometry require physiologist supervision?

INTRODUCTION: The coronavirus disease 2019 (COVID-19) pandemic has accelerated the move towards home spirometry monitoring, including in children. The aim of this study is to determine whether the remote supervision of spirometry by a physiologist improves the technical quality and failure rate of the maneuvers. METHOD: Children with cystic fibrosis who had been provided with NuvoAir home spirometers were randomly allocated to either supervised or unsupervised home spirometry following a detailed training session. Home spirometry was performed every 2 weeks for 12 weeks. Tests were assigned a quality factor (QF) using our laboratory grading system as per American Thoracic Society/European Respiratory Society standards, with tests marked from A to D, or Fail. In our laboratory, we aim for QF A in all spirometry tests, but report results of QF B or C with a cautionary note. QF A was, therefore, the primary outcome, and QF A-C, the secondary outcome. RESULTS: Sixty-one patients were enrolled; 166 measurements were obtained in the supervised group, and 153 in the unsupervised group. Significantly more measurements achieved QF A in the supervised compared to unsupervised group (89% vs. 74%; p = <0.001), while proportions reaching Grade A-C were similar (99% vs. 95%; p = 0.1). All significant declines in spirometry results had a clinical rather than technical reason. Family/patient feedback for both arms was very positive. CONCLUSION: These results suggest that home spirometry in children should ideally be remotely supervised by a physiologist, but acceptable results can be obtained if resources do not allow this, provided that training is delivered and results monitored according to our protocol.