The obesity paradox in COPD describes protective effects of obesity on lung pathology and inflammation. However, the underlying relationships between obesity, diet and disease outcomes in COPD are not fully understood. In this study we measured the response to dietary fatty acids upon markers of inflammation and remodelling in human lung cells from people with and without COPD. Pulmonary fibroblasts were challenged with ω-3 polyunsaturated fatty acids (PUFAs), ω-6 PUFAs, saturated fatty acids (SFAs) or the obesity-associated cytokine TNFα. After 48–72 h release of the pro-inflammatory cytokines interleukin (IL)-6 and CXCL8 was measured using ELISA and mRNA expression and deposition of the extracellular matrix (ECM) proteins fibronectin, type I collagen, tenascin and perlecan were measured using qPCR or ECM ELISA, respectively. Challenge with the ω-6 PUFA arachidonic acid (AA), but not ω-3 PUFAs or SFAs, resulted in increased IL-6 and CXCL8 release from fibroblasts, however IL-6 and CXCL8 release was reduced in COPD (n = 19) compared to non-COPD (n = 36). AA-induced cytokine release was partially mediated by downstream mediators of cyclooxygenase (COX)-2 in both COPD and non-COPD. In comparison, TNFα-induced IL-6 and CXCL8 release was similar in COPD and non-COPD, indicating a specific interaction of AA in COPD. In patients with or without COPD, regression analysis revealed no relationship between BMI and cytokine release. In addition, AA, but not SFAs or ω-3 PUFAs reduced the basal deposition of fibronectin, type I collagen, tenascin and perlecan into the ECM in COPD fibroblasts. In non-COPD fibroblasts, AA-challenge decreased basal deposition of type I collagen and perlecan, but not fibronectin and tenascin. This study shows that AA has disease-specific effects on inflammation and ECM protein deposition. The impaired response to AA in COPD might in part explain why obesity appears to have less detrimental effects in COPD, compared to other lung diseases.

Obesity is associated with reduced operating lung volumes that may contribute to increased airway closure during tidal breathing and abnormalities in ventilation distribution. We investigated the effect of obesity on the topographical distribution of ventilation before and after methacholine-induced bronchoconstriction using single-photon emission computed tomography (SPECT)-computed tomography (CT) in healthy subjects. Subjects with obesity ( n = 9) and subjects without obesity ( n = 10) underwent baseline and postbronchoprovocation SPECT-CT imaging, in which Technegas was inhaled upright and followed by supine scanning. Lung regions that were nonventilated (Vent_non), low ventilated (Vent_low), or well ventilated (Vent_well) were calculated using an adaptive threshold method and were expressed as a percentage of total lung volume. To determine regional ventilation, lungs were divided into upper, middle, and lower thirds of axial length, derived from CT. At baseline, Vent_nonand Vent_lowfor the entire lung were similar in subjects with and without obesity. However, in the upper lung zone, Vent_non(17.5 ± 10.6% vs. 34.7 ± 7.8%, P < 0.001) and Vent_low(25.7 ± 6.3% vs. 33.6 ± 5.1%, P < 0.05) were decreased in subjects with obesity, with a consequent increase in Vent_well(56.8 ± 9.2% vs. 31.7 ± 10.1%, P < 0.001). The greater diversion of ventilation to the upper zone was correlated with body mass index ( r_s = 0.74, P < 0.001), respiratory system resistance ( r_s = 0.72, P < 0.001), and respiratory system reactance ( r_s = −0.64, P = 0.003) but not with lung volumes or basal airway closure. Following bronchoprovocation, overall Vent_nonincreased similarly in both groups; however, in subjects without obesity, Vent_nononly increased in the lower zone, whereas in subjects with obesity, Vent_nonincreased more evenly across all lung zones. In conclusion, obesity is associated with altered ventilation distribution during baseline and following bronchoprovocation, independent of reduced lung volumes.NEW & NOTEWORTHY Using ventilation SPECT-computed tomography imaging in healthy subjects, we demonstrate that ventilation in obesity is diverted to the upper lung zone and that this is strongly correlated with body mass index but is independent of operating lung volumes and of airway closure. Furthermore, methacholine-induced bronchoconstriction only occurred in the lower lung zone in individuals who were not obese, whereas in subjects who were obese, it occurred more evenly across all lung zones. These findings show that obesity-associated factors alter the topographical distribution of ventilation.

FOT parameters have good long-term repeatability in patients with stable obstructive airways disease, facilitating its ability to detect sensitive changes in airways disease. Novel cut-off values presented may help determine clinically significant change.https://bit.ly/3emL7FI

In older non-smokers with asthma and fixed airflow obstruction, X₅ measured by oscillometry reflects dynamic rather than static compliance. Distinguishing between dynamic and static compliance is important as they are due to different factors.https://bit.ly/3th0uEr

Oscillometry is increasingly adopted in respiratory clinics, but many recommendations regarding measurement settings and quality control remain subjective. The aim of this study was to investigate the optimal number of measurements and acceptable within-session coefficient of variation (CoV) in health, asthma and COPD.15 healthy, 15 asthma and 15 COPD adult participants were recruited. Eight consecutive 30-s measurements were made using an oscillometry device, from which resistance at 5 Hz (Rrs₅) was examined. The effect of progressively including a greater number of measurements onRrs₅and its within-session CoV was investigated. Data were analysed using one-way repeated-measures ANOVA with Bonferronipost hoctest.The CoV(Rrs₅) of the first three measurements was 6.7±4.7%, 9.7±5.7% and 12.6±11.2% in healthy, asthma and COPD participants, respectively. Both meanRrs₅and CoV(Rrs₅) were not statistically different when progressively including four to eight measurements. Selecting the three closestRrs₅values over an increasing number of measurements progressively decreased the CoV(Rrs₅). In order for ≥95% of participants to fall within a target CoV(Rrs₅) of 10%, four or more, five and six measurements were needed in health, asthma and COPD, respectively.Within-session variability of oscillometry is increased in disease. Furthermore, the higher number of measurements required to achieve a set target for asthma and COPD patients may not be practical in a clinical setting. Provided technical acceptability of measurements is established,i.e.by removing artefacts and outliers, then a CoV of 10% is a marker of quality in most patients, but we suggest higher CoVs up to 15–20% should still be reportable.