Breath Analysis

Giorgio Pennazza,Marco Santonico

• Publisher: Academic Press
• Year: 2018
• ISBN:
  9780128145630
• Topic: Biological Sciences
• Subtopic: Biotechnology
• Index: Biological Sciences

Breath Analysis presents state-of-the-art research in this specialized field, also offering guidance on how best to design the technology and conduct analysis. The book primarily focuses on the diagnosis of lung cancer, asthma and Chronic Obstructive Pulmonary Diseases. The reliability, consistency and utility of the results from breath analysis depends on exhaled breath sampling procedures and tools, gas sensor array technology (sensing material and transducer), and finally, medical pertinence and interpretation. The book gives step-by-step procedures and discusses best practice solutions for problems in sample collection, sensor technology, clinical assessment, medical interpretation and data analysis.

The book's primary audience would include biomedical engineers and medical doctors, but it is also useful for hospital technicians, hospital and biomedical SME leading figures, and those in PhD level Engineering and Medicine.

• Presents an overview of existing breath analysis technology, along with their pros and cons
• Provides a tool for mapping, bridging and translating different approaches and available devices
• Covers best practices and procedures for exhaled breath collection

1

Introduction. Breathprinting: What, Why, How

Giorgio Pennazza; Marco Santonico Unit of Electronics for Sensor Systems, Department of Engineering, Campus Bio-Medico University of Rome, Rome, Italy

Abstract

What is breathprinting? How can breathprinting be useful in a medical context? How can state-of-the-art breathprinting be performed? “The answer is blowing in the wind¹”: the breath is volatile; indeed, elusive, and intrinsically complex. This book tries to make this point, and this first chapter represents its introduction. The main message of the chapter is that breathprinting is effective when the target application is well defined, and the best experimental chain is tailored to the application needs. The crucial points include merging and harmonizing the features of the available technologies, both for exhaled breath sampling and analysis; finalizing the experiment with a thoughtful data fusion between clinical and sensor data; and building up a wide network of the main scientific groups and of the stakeholders supporting an international multicenter study.

Keywords

Exhaled breath; Breathprinting; Sensor array; Analytical chemistry; Multivariate data analysis; Noninvasive diagnosis

1 Introduction

Physicians sometimes work as detectives: when looking for clues beneath symptoms and test results, they’re trying to find the killer, and catch it with the correct diagnosis. A best practice for a detective should be to prevent a crime; this means, for a physician, to prevent diseases by identifying early symptoms and knowing the possible causes. Thus, disease knowledge and prevention are the key points for timely and correct diagnoses. This hard work is mainly supported by physicians’ expertise, and by instrumental evidence, in which technology plays a fundamental role.

Diagnostic instruments, in general, have the aim of revealing altered conditions of certain parameters (e.g., blood analysis, spirometry) or of presenting a “global picture” or pattern (e.g., computed tomography, X-rays), with respect to a standard healthy condition (or nondiseased). Very often the access to this information is invasive or minimally invasive, thus lowering the frequency of the monitoring, and affecting the efficacy of the preventive action. Among biological fluids exhaled, breath is accessible with a minimally invasive collection procedure. Exhaled breath represents, also, a rich source of information about the individual's health [1, 2]. Conversely, exhaled breath is a very complex biological fluid, also containing other information about different sources that could affect the patient's health: habits, food and beverage uptake, and environmental factors [3]. Also, when focusing on the patient's health, many comorbidities could influence exhaled breath composition [4, 5]. Additionally, the collection procedure can affect the representativeness of the sample [5, 6].

Before illustrating the technologies for exhaled breath sampling and measurement, and before discussing their effectiveness, it is mandatory to define what exhaled breath analysis is.

This chapter is intended to be a sort of “extended summary” of the book, introducing the reader to different parts of the work. The idea of this introduction is to guide a researcher, interested in one or more of these aspects, to design his/her experiments by composing the elements for a specific application using state-of-the-art know-how, critical data points, and available technology.

2 What: Definition and Background

The analysis of exhaled breath is an examination procedure that is intrinsically noninvasive (minimally invasive in case of forced exhalation) that can be used for the diagnosis, prognosis, and monitoring of many pathologies and disease conditions. It is performed with different technological approaches for exhaled breath collection and measurement [7, 8]. This definition is composed of three parts: what (the sample, exhaled breath); why (the target application); and how (the technology). These three aspects are covered in this section and the next two.

What is exhaled breath? Exhaled breath is a complex mixture containing more than 3000 volatile organic compounds (VOCs) [8]. The possible sources of such VOCs are [4–6, 8]: inhaled compounds (related to the environment); food intake; metabolic processes (diseased and normal); inflammatory processes; genomic or structural changes (disease-induced or physiological) in the lung epithelium; cancerous cells; abnormal metabolism or altered redox status; bacterial populations in the oral cavity, lungs, and gut.

What is the output of the analysis of exhaled breath, and how can it be used? The output of such a complex mixture of VOCs can be provided in two different modalities: a list of alleged compounds, or a pattern (a fingerprint, a profile) [8, 9]. The utilization (via suitable elaboration) of these outputs depends on the target application: is the research looking for specific VOCs? Or is it addressing a characterization via a pattern of VOCs (a sort of exhaled breath classification, or clustering based on fingerprints)?

Considering the huge number of VOCs composing exhaled breath, it is difficult to obtain a complete list of them without performing successive analyses of the same sample with different settings of the instrument. The different settings allow testers to focus on different compound families. Thus, the question is: when VOCs identification is the main goal, should it be the result of a complete characterization of exhaled breath, or is the investigation looking for specific markers?

The definition of breath analysis contains a multiplicity of compounds originated by a multiplicity of different sources. It also contains a multiplicity of different techniques, methods, and technologies pertaining to engineering and analytical chemistry, and often inspired and designed by the harmonic fusion of these two disciplines. Exhaled breath analysis produces multidimensional data arrays, which require a multiplicity of different techniques for data analysis. And a decomposition process can indeed provide the definition of exhaled breath, in the same way that a prism affects light (see Fig. 1): the light is unique because it is focused on a specific goal. But this alignment, addressed to a specific target, is the result of a multidisciplinary integration.

Fig. 1 Overview of the measure chain developed for a breath analysis application. The multidisciplinary background is integrated in the experiment's design, and harmonized by the target application, which asks for specific arrangements among the available ones. The proposed analogy with light says that when the experiment is well focused on the goal, it means that the parameters used for the instrument settings to convey and direct the light are well defined. Moreover, light's composition is known in all its components.

Multiplicity is the keyword of breath analysis, because it deals with multidimensional data, obtained with a variety of different technologies, treated with many different approaches, addressed to different targets, and interpreted via a multidisciplinary study. This keyword tells you that the research context of breath analysis is rich, but complex. Selecting a specific target,...