Combination of Exhaled Breath Analysis with Parallel Lung Function and FeNO Measurements in Infants

Abstract

Breath analysis by secondary electrospray ionization-high resolution mass spectrometry (SESI-HRMS) offers the possibility to measure comprehensive metabolic profiles. The technology is currently being deployed in several clinical settings in Switzerland and China. However, patients are required to exhale directly into the device located in a dedicated room. Consequently, clinical implementation in patients incapable of performing necessary exhalation maneuvers (e.g., infants) or immobile (e.g., too weak, elderly, or in intensive care) remains a challenge. The aim of this study was to develop a method to extend such breath analysis capabilities to this subpopulation of patients by collecting breath samples remotely (offline) and promptly (within 10 min) transfer them to SESI-HRMS for chemical analysis. We initially assessed the method in adults by comparing breath mass spectra collected offline with Nalophan bags against spectra of breath samples collected in real time. In total, 13 adults provided 176 pairs of real-time and offline measurements. Lin’s concordance correlation coefficient (CCC) was used to estimate the agreement between offline and real-time analyses. Here, 1249 mass spectral features (55% of total detected) exhibited Lin’s CCC > 0.6. Subsequently, the method was successfully deployed to analyze breath samples from infants (n = 16), obtaining as a result SESI-HRMS breath profiles. To demonstrate the clinical feasibility of the method, we measured in parallel other clinical variables: (i) lung function, which characterizes the breathing patterns, and (ii) nitric oxide, which is a surrogate marker of airway inflammation. As a showcase, we focused our analysis on the exhaled oxidative stress marker 4-hydroxynonenal and its association with nitric oxide and minute ventilation.

Preservation of exhaled breath samples for analysis by off-line SESI-HRMS: proof-of-concept study

“…All samples were collected and analyzed in the same room. The exhaled breath collection was carried out by means of the off-line device described by Decrue et al [30], which consists of a Nalophan® bag of approximately 2 l volume and 700 cm 2 surface (Nalophan® NA, 20 ± 5 µm thick, Kalle) coupled at one end to a mouthpiece (Hudson RCI®) and at the other end to a tube (Rotilabo® PTFE, 6 mm, 8 mm, length 90 mm, Carl Roth®) connected to a valve (VHK2-08F-08F, SMC Switzerland). The Nalophan® bags were prepared the day before the visit of the subjects.…”

“…Exhaled breath samples were analyzed using a SESI ion source (SuperSESI, FIT, Spain) coupled to a high resolution mass spectrometer (Q-Exactive Plus, Thermo Fisher Scientific, Germany) following the protocol described above [27,30,36]. Once the storage period had been completed, the exhaled breath contained in the Nalophan® bags was infused into the ion source.…”

“…intensive care patients, neonates, infants, etc). Therefore, especially for non-cooperative passive patients, it is a container required to collect the exhaled breath samples that subsequently can be transported to the analytical platform [30]. In this regard, PTR-MS and SIFT-MS techniques have been successfully employed in several studies to analyze exhaled air previously stored in gas sampling bags of different type [5,[31][32][33].…”

“…In this regard, PTR-MS and SIFT-MS techniques have been successfully employed in several studies to analyze exhaled air previously stored in gas sampling bags of different type [5,[31][32][33]. Along the same lines, we have recently presented the first protocol for off-line breath analysis using SESI-HRMS being successfully tested in both adults and neonates [30]. Moreover, the conventional real-time method was compared with the new off-line method (breath samples were collected in Nalophan® bags and quickly analyzed within 10 min of collection) by computation of the Lin's Concordance Correlation Coefficient (Lin's CCC) [34], and 1249 m/z signals with Lin's CCC > 0.6 were identified [30].…”

“…Once the applicability of the off-line method has been checked [30], the present paper describes a pilot study which evaluated the conservation of the exhaled breath samples in Nalophan® bags over time under different conditions (room temperature and dry ice), in order to optimize the management and handling of the sample storage as well as its effect on the reproducibility and repeatability of breath analysis by SESI-HRMS. Room temperature and dry ice storage conditions were selected as being compatible for easy and economical transport of exhaled breath samples collected at different locations (e.g.…”