BackgroundChanges in exhaled volatile organic compounds (VOCs) can be used to discriminate between respiratory diseases, and increased concentrations of hydrocarbons are commonly linked to oxidative stress. However, the VOCs identified are inconsistent between studies, and translational studies are lacking.MethodsIn this bench-to-bedside study, we captured VOCs in the headspace of A549 epithelial cells after exposure to hydrogen peroxide (H2O2), to induce oxidative stress, using high-capacity polydimethylsiloxane sorbent fibres. Exposed and unexposed cells were compared using targeted and untargeted analysis. Breath samples of invasively ventilated ICU patients (n=489) were collected on sorbent tubes and associated with the inspired oxygen fraction (FiO2) to reflect pulmonary oxidative stress. Headspace samples and breath samples were analysed using gas-chromatography and mass-spectrometry.ResultsIn the cell, headspace octane concentration was decreased after oxidative stress (p=0.0013), while the other VOCs were not affected. 2-ethyl-1-hexanol, showed an increased concentration in the headspace of cells undergoing oxidative stress in untargeted analysis (p=0.00014). None of the VOCs that were linked to oxidative stress showed a significant correlation with FiO2 (Rsrange: −0.015 to −0.065) or discriminated between patients with FiO2≥0.6 or below (AUC range: 0.48 to 0.55).ConclusionDespite a comprehensive translational approach, validation of known and novel volatile biomarkers of oxidative stress was not possible in patients at risk of pulmonary oxidative injury. The inconsistencies observed highlight the difficulties faced in VOC biomarker validation and that caution is warranted in the interpretation of the pathophysiological origin of discovered exhaled breath biomarkers.

Background Early and accurate recognition of respiratory pathogens is crucial to prevent increased risk of mortality in critically ill patients. Microbial-derived volatile organic compounds (mVOCs) in exhaled breath could be used as non-invasive biomarkers of infection to support clinical diagnosis. Methods In this study, we investigated the diagnostic potential of in vitro confirmed mVOCs in the exhaled breath of patients under mechanically ventilation from the BreathDx study. Samples were analysed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Results Pathogens from bronchoalveolar lavage (BAL) cultures were identified in 45/89 patients and S. aureus was the most commonly identified pathogen (n = 15). Out of 19 mVOCs detected in the in vitro culture headspace of four common respiratory pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli), 14 were found in exhaled breath samples. Higher concentrations of two mVOCs were found in the exhaled breath of patients infected with S. aureus compared to those without (3-methylbutanal p < 0.01. AUROC = 0.81-0.87 and 3-methylbutanoic acid p = 0.01. AUROC = 0.79-0.80). In addition, bacteria identified from BAL cultures which are known to metabolise tryptophan (Escherichia coli, Klebsiella oxytoca and Haemophilus influenzae) were grouped and found to produce higher concentrations of indole compared to breath samples with culture-negative (p = 0.034) and other pathogen-positive (p = 0.049) samples. Conclusions This study demonstrates the capability of using mVOCs to detect the presence of specific pathogen groups with potential to support clinical diagnosis. Although not all mVOCs were found in patient samples within this small pilot study, further targeted and qualitative investigation is warranted using multi-centre clinical studies.

Elexacaftor/tezacaftor/ivacaftor (ETI) is a cystic fibrosis (CF) transmembrane conductance regulator modulator, which has shown efficacy in CF patients (≥6 years) with ≥1 Phe508del mutation and a minimal function mutation. In October 2019, ETI became available on compassionate use basis for Dutch CF patients with severe lung disease. Our objective was to investigate safety and efficacy of ETI in this patient group in a real‐life setting. A multicenter longitudinal observational study was conducted to examine changes in FEV 1 , BMI, and adverse events at initiation and 1, 3, 6, and 12 months after starting ETI. The number of exacerbations was recorded in the 12 months before and the 12 months after ETI treatment. Patients eligible for compassionate use had a FEV 1 <40% predicted. Wilcoxon signed‐rank test analyzed changes over time. Twenty subjects were included and followed up for up to 12 months after starting ETI. Treatment was well tolerated with mild side effects reported, namely, rash (15%) and stomach ache (20%) with 80% resolving within 1 month. Mean absolute increase of FEV 1 was 11.8/13.7% ( p ≤ .001) and BMI was 0.49/1.87 kg/m 2 ( p < .001–0.02) after 1/12 months, respectively. In comparison to the number of exacerbations pretrial, there was a marked reduction in exacerbations after initiation. Our findings show long‐term effects of treatment with ETI in patients with severe CF lung disease in a real‐life setting. Treatment with ETI is associated with increased lung function and BMI, less exacerbations, and only mild side effects.