Effect of posture on lung ventilation distribution and associations with structure in children with cystic fibrosis

Ramsey, Kathryn; McGirr, Caroline; Stick, Stephen M.; Hall, Graham L.; Simpson, Shannon J.

doi:10.1016/j.jcf.2017.01.013

Cited by 14 publications

(25 citation statements)

References 27 publications

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“…The effect of posture on LCI in children with CF has recently been assessed [ 5 ]. This study compared CF children with mild disease to healthy controls (HC) and showed that LCI in the supine posture was elevated when compared to sitting and that supine LCI correlated better than sitting LCI with metrics derived from high resolution computed tomography (HRCT).…”

Section: Introductionmentioning

confidence: 99%

“…Further to the work of Ramsey et al [ 5 ], the aim of this study therefore was to compare LCI and the phase III slope parameters S cond and S acin , sitting and supine, in children with a range of CF lung disease as well as in HC, and to measure the extent to which changing lung volume affects the change in LCI. We hypothesised that supine posture would firstly reduce lung volume (FRC) with a resultant effect on gas mixing, but also that there would be an additional effect of posture on ventilation heterogeneity within the lungs.…”

Section: Introductionmentioning

confidence: 99%

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Supine posture changes lung volumes and increases ventilation heterogeneity in cystic fibrosis

et al. 2017

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IntroductionLung Clearance Index (LCI) is recognised as an early marker of cystic fibrosis (CF) lung disease. The effect of posture on LCI however is important when considering longitudinal measurements from infancy and when comparing LCI to imaging studies.Methods35 children with CF and 28 healthy controls (HC) were assessed. Multiple breath washout (MBW) was performed both sitting and supine in triplicate and analysed for LCI, Scond, Sacin, and lung volumes. These values were also corrected for the Fowler dead-space to create ‘alveolar’ indices.ResultsFrom sitting to supine there was a significant increase in LCI and a significant decrease in FRC for both CF and HC (p<0.01). LCI, when adjusted to estimate ‘alveolar’ LCI (LCIalv), increased the magnitude of change with posture for both LCIalv and FRCalv in both groups, with a greater effect of change in lung volume in HC compared with children with CF. The % change in LCIalv for all subjects correlated significantly with lung volume % changes, most notably tidal volume/functional residual capacity (Vtalv/FRCalv (r = 0.54,p<0.001)).ConclusionThere is a significant increase in LCI from sitting to supine, which we believe to be in part due to changes in lung volume and also increasing ventilation heterogeneity related to posture. This may have implications in longitudinal measurements from infancy to older childhood and for studies comparing supine imaging methods to LCI.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Supine posture changes lung volumes and increases ventilation heterogeneity in cystic fibrosis

et al. 2017

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“…More broadly, these results suggest that elevated MBW indices induced by airway constrictions are more variable in general, which is observed experimentally in CF and asthma patients through the increased sensitivity of LCI to posture [36,37], as well increased inter-patient variability [38].…”

Section: Discussionmentioning

confidence: 56%

“…More broadly, these results suggest that elevated MBW indices induced by airway constrictions are more variable in general, which is observed experimentally through the increased variance in LCI measured in CF and asthma patients [46], as well as an increased sensitivity of LCI to posture which affects the distribution of ventilation due to gravity [47,48]. This latter affect can be understood by perturbing acinar elastance, which affects their rate of ventilation.…”

Section: Discussionmentioning

confidence: 69%

“…Other assumptions made in the model are likely to affect predicted MBW outcomes. Most significantly, we have neglected the effects of gravity/posture on inter-regional variation, as well as mechanical coupling of the lung units, which are both predicted to affect fractional ventilation and MBW indices in simulations [40,17,41,42] and experiments [43,44,48]. The lack of mechanical coupling means that the predicted asynchrony between lung regions may be exaggerated compared to reality, which could indicate why the range of predicted S cond values is notably wider than the increase measured between healthy volunteers and CF patients [50].…”

Section: Discussionmentioning

confidence: 99%

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Modelling structural determinants of ventilation heterogeneity: a perturbative approach

Whitfield

Horsley

Jensen

2018

Preprint

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We have developed a computational model of gas mixing and ventilation in the human lung represented as a bifurcating network. We have simulated multiple-breath washout (MBW), a clinical test for measuring ventilation heterogeneity in patients with obstructive lung conditions. By applying airway constrictions inter-regionally, we have predicted the response of MBW indices to obstructions and found that they detect a narrow range of severe constrictions that reduce airway radius to between 10% -30% of healthy values. These results help to explain the success of the MBW test to distinguish obstructive lung conditions from healthy controls. Further, we have used a perturbative approach to account for intra-regional airway heterogeneity that avoids modelling each airway individually. We have found, for random airway heterogeneity, that the variance in MBW indices is greater when largemagnitude constrictions are already present, and that the indices become more sensitive to structural heterogeneity when already elevated. This method is a computationally efficient way to probe the lung's sensitivity to structural changes, and to quantify uncertainty in predictions due to random variations in lung mechanical and structural properties. Author summaryThe multiple-breath washout (MBW) test is a clinical test of lung function that measures the efficiency of gas transport and mixing within the lung, and which has proven very sensitive in detecting early disease in cystic fibrosis (CF). In this paper we have developed a computational model of lung function to simulate air movement and gas transport in the lungs and generate MBW outcomes. We have used this to show why MBW is so sensitive to airway blockages similar to those encountered in CF. Importantly, the model incorporates a new and computationally-efficient method that also allows us to account for uncertainty and randomness in lung structure and mechanical properties. This has been used to show how variability of MBW outcomes increases in disease states. The model provides a framework for modelling clinical data, where accounting for uncertainties in inputs is crucial in making clinically meaningful predictions.

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Mucus plugging, air trapping, and bronchiectasis are important outcome measures in assessing progressive childhood cystic fibrosis lung disease

Robinson

Goris

Moss

et al. 2020

Pediatric Pulmonology

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Objective To determine which outcome measures could detect early progression of disease in school‐age children with mild cystic fibrosis (CF) lung disease over a two‐year time interval utilizing chest computed tomography (CT) scores, quantitative CT air trapping (QAT), and spirometric measurements. Methods Thirty‐six school‐age children with mild CF lung disease (median [interquartile range] age 12 [3.7] years; percent predicted forced expiratory volume in 1 second (ppFEV1) 99 [12.5]) were evaluated by serial spirometer‐controlled chest CT scans and spirometry at baseline, 3‐month, 1‐ and 2‐years. Results No significant changes were noted at 3‐month for any variable except for decreased ppFEV1. Mucus plugging score (MPS) and QATA1 and A2 increased at 1‐ and 2‐years. The bronchiectasis score (BS), and total score (TS) were increased at 2‐year. All variables tested with the exception of bronchial wall thickness score, parenchymal score (PS), and ppFEV1, were consistent with longitudinal worsening of lung disease. Multivariate analysis revealed baseline PS, baseline TS, and 1‐year changes in BS and air trapping score were predictive of 2‐year changes in BS. Conclusions MPS and QATA1‐A2 were the most sensitive indicators of progressive childhood CF lung disease. The 1‐year change in the bronchiectasis score had the most positive predictive power for 2‐year change in bronchiectasis.

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Effect of posture on lung ventilation distribution and associations with structure in children with cystic fibrosis

Abstract: Body posture influences lung volumes and ventilation distribution in both healthy children and children with CF. MBW testing in the supine posture strengthened associations with structural lung damage.

Cited by 14 publications

References 27 publications

Supine posture changes lung volumes and increases ventilation heterogeneity in cystic fibrosis

Supine posture changes lung volumes and increases ventilation heterogeneity in cystic fibrosis

Modelling structural determinants of ventilation heterogeneity: a perturbative approach

Mucus plugging, air trapping, and bronchiectasis are important outcome measures in assessing progressive childhood cystic fibrosis lung disease

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