Simultaneous measurement of inhaled air and exhaled breath by double multicapillary column ion-mobility spectrometry, a new method for breath analysis: results of a feasibility study

Abstract

The high sensitivity of the methods applied in breath analysis entails a high risk of detecting analytes that do not derive from endogenous production. Consequentially, it appears useful to have knowledge about the composition of inhaled air and to include alveolar gradients into interpretation. The current study aimed to standardise sampling procedures in breath analysis, especially with multicapillary column ion-mobility spectrometry (MCC-IMS), by applying a simultaneous registration of inhaled air and exhaled breath. A "double MCC-IMS" device, which for the first time allows simultaneous analysis of inhaled air and exhaled breath, was developed and tested in 18 healthy individuals. For this, two BreathDiscovery instruments were coupled with each other. Measurements of inhaled air and exhaled breath in 18 healthy individuals (mean age 46±10.9 years; nine men, nine women) identified 35 different volatile organic compounds (VOCs) for further analysis. Not all of these had positive alveolar gradients and could be regarded as endogenous VOCs: 16 VOCs had a positive alveolar gradient in mean; 19 VOCs a negative one. 12 VOCs were positive in >12 of the healthy subjects. For the first time in our understanding, a method is described that enables simultaneous measurement of inhaled air and exhaled breath. This facilitates the calculation of alveolar gradients and selection of endogenous VOCs for exhaled breath analysis. Only a part of VOCs in exhaled breath are truly endogenous VOCs. The observation of different and varying polarities of the alveolar gradients needs further analysis.

Conflict of interest statement

Conflict of interest: M. Westhoff has nothing to disclose. M. Friedrich is member of the staff of Braun Melsungen AG, Branch Dortmund, Center of Competence Breath Analysis, Dortmund. J.I. Baumbach is member of the staff of Braun Melsungen AG, Branch Dortmund, Center of Competence Breath Analysis, Dortmund.

Copyright ©The authors 2022.

Figures

FIGURE 1

Schematic experimental setup consisting of two BreathDiscovery, two REDMON and two SpiroScout instruments. The rear SpiroScout was turned around 180° and connected to the proximal one. Each SpiroScout was linked to one BreathDiscovery, that is connected to a REDMON which provided the operating gas. The red line indicates the path of the inhaled air moving towards the patient through the SpiroScouts and reaching the BreathDiscovery 01. The blue line shows the path of exhaled breath moving away from the patient and reaching the corresponding BreathDiscovery.

FIGURE 2

Comparison of volume and flows during inspiration and expiration by mirroring them on top of each other. The left y-axis shows the flow, while the right y-axis indicates the volume (flow rate over time). The time in seconds is shown on the x-axis. The flow is proportional to L·s−1 and the volume to litres. Although the instruments are not calibrated, they are equal. Δa and Δb indicate the rise of the flow at expiration and inspiration, respectively. The duration of either expiration or inspiration is indicated by ΔC and ΔD. Each SpiroScout should recognise both directions of flow, even if only one is collected and analysed. The area of the integrals Ex (expiration) and In (inspiration) show that although their flows are mirrored and should be the same, they differ slightly from each other. a.u.: arbitrary units.

FIGURE 3

Three-dimensional spectrum of a) inhaled air and b) exhaled breath. The y-axes indicate the retention time (RT) in seconds; the x-axes the drift time in 1/K0 Vs·cm−2. The third axis, the peak intensity, increases from white to yellow colour. At expiration, peak P1 alone can be visually recognised as more intense compared to the inspiration. However, peak P5 can be seen more intensely during inspiration (cf. black frames). For detailed peak analysis intensities have to be measured and compared.

FIGURE 4

Peak images of all peaks found from all 18 healthy test subjects. The images are created from the peak windows from the three-dimensional spectrum of each measurement. Peak intensities reach from white being the lowest intensity to yellow being the highest. The top 18 rows result from inhaled air (rows at the height of the red arrow); the lower 18 show exhaled breath (rows at the height of the blue arrow). Each column shows one out of 35 peaks, ascending from left to right and starting at peak P0. The black frame circles peak P1. Here the difference between the more intense peaks on inhaled air compared to exhaled breath can be made visually.