Breath analysis using external cavity diode lasers: a review

Abstract

Most techniques that are used for diagnosis and therapy of diseases are invasive. Reliable noninvasive methods are always needed for the comfort of patients. Owing to its noninvasiveness, ease of use, and easy repeatability, exhaled breath analysis is a very good candidate for this purpose. Breath analysis can be performed using different techniques, such as gas chromatography mass spectrometry (MS), proton transfer reaction-MS, and selected ion flow tube-MS. However, these devices are bulky and require complicated procedures for sample collection and preconcentration. Therefore, these are not practical for routine applications in hospitals. Laser-based techniques with small size, robustness, low cost, low response time, accuracy, precision, high sensitivity, selectivity, low detection limit, real-time, and point-of-care detection have a great potential for routine use in hospitals. In this review paper, the recent advances in the fields of external cavity lasers and breath analysis for detection of diseases are presented.

On-Line Analysis of Exhaled Breath

“…There are several excellent reviews on optical spectroscopic methods for breath analysis, some of them quite recent [114][115][116][117] . Predominantly, absorption spectroscopy in the mid or near infrared is employed, while there are hardly any applications of Raman spectroscopy and UV/VIS spectroscopy related to exhaled breath analysis 118,119 .…”

Breathprinting and Early Diagnosis of Lung Cancer

“…An intriguing scenario on the use of this technology for exhaled breath fingerprinting is provided by the implementation of real-time breath analysis through proton-transfer-reaction mass spectrometry (PTR-MS), proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS), or selected ion flow tube MS. 9,73 In these systems, the gas sample interacts with excess ion charges (i.e., hydronium ions), resulting in the attendant transfer of ions to the VOCs which are then analyzed with GC-MS. 15 No need for sample collection or preconcentration procedures is contemplated with the above techniques which, however, remain far from being suitable for routine use in the clinical setting. 74 In this context, two technological developments may pave the way to the development of the entire breath analytic process in a real-time mode: matrix-assisted laserenhanced desorption/ionization and secondary nanoelectrospray ionization MS. 74,75 These techniques are based on the concept of obtaining ionization of macromolecules contained in VOCs into analytes which are then accelerated into the MS. 74,75 A major hurdle against the wide implementation of the above techniques into clinical practice is that this instrumentation is bulky and requires complex sampling and pre-concentration methods. 74 In this setting, an important technological advancement is represented by the optical measurements of VOCs through the application of laser absorption techniques to obtain spectral fingerprints expressed in ranges of ultraviolet to mid-infrared frequencies with detection levels ranging from parts per million to parts per billion.…”

“…74 In this context, two technological developments may pave the way to the development of the entire breath analytic process in a real-time mode: matrix-assisted laserenhanced desorption/ionization and secondary nanoelectrospray ionization MS. 74,75 These techniques are based on the concept of obtaining ionization of macromolecules contained in VOCs into analytes which are then accelerated into the MS. 74,75 A major hurdle against the wide implementation of the above techniques into clinical practice is that this instrumentation is bulky and requires complex sampling and pre-concentration methods. 74 In this setting, an important technological advancement is represented by the optical measurements of VOCs through the application of laser absorption techniques to obtain spectral fingerprints expressed in ranges of ultraviolet to mid-infrared frequencies with detection levels ranging from parts per million to parts per billion. 76,77 Examples of this concept are tunable diode laser absorption spectroscopy (TDLAS) and cavity ringdown spectroscopy (CRDS) with its variants (i.e., integrated cavity output spectroscopy, cavity enhanced absorption spectroscopy, and cavity leak-out absorption spectroscopy).…”

Vacuum Ultraviolet Absorption Spectroscopy Analysis of Breath Acetone Using a Hollow Optical Fiber Gas Cell

“…A variety of optical analysis methods have been proposed to solve the above problems [ 9 , 10 , 11 ]. Optical methods are usually advantageous over GC-MS methods with respect to size and cost.…”