Abstract
Breath analysis is a powerful technique for detection of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Nitric oxide (NO), nitrous oxide (N2O), carbon dioxide (CO2) and carbon monoxide (CO) present in breath sample acts a marker for respiratory disease. A system is proposed to design a Breath Analyser instrument. Its subsystems consist of a compact fast response laser system for analysis of multiple gases by infrared absorption. For quantitative analysis of trace gases in human breath, patient’s breath sample is collected inside a gas chamber. Two ends of gas chamber are mounted with concave mirrors with special type of mirror holders which have two angle adjustment piezo actuators. Angle adjustment piezo actuators are used to compensate for any angular misalignment in order of micro radians. Third piezo actuator is used for expansion of laser resonator. Special mirror holder consists of three plates which are supported with guide pins. Mirror is mounted on tilt plate which can be rotated in vertical and horizontal direction with the help of two piezo actuators. This mirror holder structure is made of stainless steel and can be used in any type of air and vacuum environment. It is found that for linear misalignment given to any mirror of optical cavity, the angular misalignment exists and vice versa. Thus artifact elimination of laser cavity is sensitive process. With three piezo actuator based special mirror holders, a precise measurement of laser absorption can be done.
Highlights
Breathing is a complex process of gas exchange by diffusion of gasses over the lung capillaries.Exhaled breath contains thousands of molecules, which are at the level of parts per billion or even parts per trillion [1,2]
Once the beam enters inside two mirror resonator it gets reflected from another concave mirror and continues to do so
The reflected light from optical cavity contains the information of resonance
Summary
Breathing is a complex process of gas exchange by diffusion of gasses over the lung capillaries. Exhaled breath contains thousands of molecules, which are at the level of parts per billion (ppb) or even parts per trillion (ppt) [1,2]. These molecules can provide important information about functioning of respiratory system. A patient’s breath sample is collected inside a gas cell and wavelength of laser is tuned with respect to absorption peak for particular gas. According to Lambert-Beer’s law [2], The transmitted light intensity depends of path of laser within gas sample and absorption strength of gas molecules. An optical resonator system can be used for detection of particular gases within breath sample. The following Table 1. shows list of disease associated with particular gas molecules
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