Hydrogen Cyanide In Breath Research Articles

On the importance of accurate quantification of individual volatile metabolites in exhaled breath

It is argued that shortcomings of certain approaches to breath analysis research based on superficial interpretation of non-quantitative data are inadvertently inhibiting the progression of non-invasive breath analysis into clinical practice. The objective of this perspective is to suggest more clinically profitable approaches to breath research. Thus, following a discourse on the challenges and expectations in breath research, a brief indication is given of the analytical techniques currently used for the analysis of very humid exhaled breath. The seminal work that has been carried out using GC-MS revealed that exhaled breath comprises large numbers of trace volatile organic compounds, VOCs. Unfortunately, analysis of these valuable GC-MS data is mostly performed using chemometrics to distinguish the VOC content of breath samples collected from patients and healthy controls, and reliable quantification of the VOCs is rarely deemed necessary. This limited approach ignores the requirements of clinically acceptable biomarkers and misses the opportunity to identify relationships between the concentrations of individual VOCs and certain related physiological or metabolic parameters. Therefore, a plea is made for more effort to be directed towards the positive identification and accurate quantification of individual VOCs in exhaled breath, which are more physiologically meaningful as best exemplified by the quantification of breath nitric oxide, NO. Support for the value of individual VOC quantification is illustrated by the SIFT-MS studies of breath hydrogen cyanide, HCN, a biomarker of Pseudomonas aeruginosa infection, breath acetic acid as an indicator of airways acidification in cystic fibrosis patients, and n-pentane as a breath biomarker of inflammation in idiopathic bowel disease patients. These single VOCs could be used as non-invasive monitors of the efficacy of therapeutic intervention. The increase of breath methanol following the ingestion of a known amount of the sweetener aspartame impressively shows that accurate breath analysis is a reliable indicator of blood concentrations. However, using individual VOCs for specific disease diagnosis does have its problems and it is, perhaps, more appropriate to see their concentrations as proxy markers of general underlying physiological change. We dedicate this perspective to Lars Gustafsson for his seminal work on breath research and especially for his pioneering work on nitric oxide measurements in exhaled breath in asthma, which best shows the utility and value of the quantification of individual breath biomarkers on which this perspective focuses.

SERS spectroscopy for detection of hydrogen cyanide in breath from children colonised with P. aeruginosa

There is a need for a fast and non-invasive tool to detect Pseudomonas aeruginosa airway colonisation in cystic fibrosis (CF) patients unable to expectorate.

Exhaled breath hydrogen cyanide as a marker of early Pseudomonas aeruginosa infection in children with cystic fibrosis.

Hydrogen cyanide is readily detected in the headspace above Pseudomonas aeruginosa cultures and in the breath of cystic fibrosis (CF) patients with chronic (P. aeruginosa) infection. We investigated if exhaled breath HCN is an early marker of P. aeruginosa infection.233 children with CF who were free from P. aeruginosa infection were followed for 2 years. Their median (interquartile range) age was 8.0 (5.0–12.2) years. At each study visit, an exhaled breath sample was collected for hydrogen cyanide analysis. In total, 2055 breath samples were analysed. At the end of the study, the hydrogen cyanide concentrations were compared to the results of routine microbiology surveillance.P. aeruginosa was isolated from 71 children during the study with an incidence (95% CI) of 0.19 (0.15–0.23) cases per patient-year. Using a random-effects logistic model, the estimated odds ratio (95% CI) was 3.1 (2.6–3.6), which showed that for a 1- ppbv increase in exhaled breath hydrogen cyanide, we expected a 212% increase in the odds of P. aeruginosa infection. The sensitivity and specificity were estimated at 33% and 99%, respectively.Exhaled breath hydrogen cyanide is a specific biomarker of new P. aeruginosa infection in children with CF. Its low sensitivity means that at present, hydrogen cyanide cannot be used as a screening test for this infection.

P197 The Incidence Of New Pseudomonas Aeruginosa Infection In Children With Cystic Fibrosis

Introduction Pseudomonas aeruginosa (PA) is one of the most important pathogens in cystic fibrosis (CF). Although there is a wealth of data about the prevalence of chronic PA infection, there is a paucity of evidence about the incidence of new PA infection. Methods The SPACE (Sensitivity and specificity of PA detection using the hydrogen Cyanide concentration of Exhaled breath) study investigated if exhaled breath hydrogen cyanide is an early marker of PA infection in children with CF. Breath samples, clinical data and microbiology samples were collected at each out-patient appointment from a large cohort of children with CF who had not isolated PA for >12 months. This abstract reports the PA acquisition data. Results 233 children were followed for a median of 2.0 (1.7–2.3) years. The median (IQR) age was 8.0 (5.0–12.2) years. 71 children isolated PA during the study period. The incidence rate (95% CI) of new PA infections was 0.15 (0.10–0.22) cases per patient year for those that had never previously isolated PA and 0.19 (0.13–0.27) cases per patient year for those that had been free from PA for >12 months. This rate varied between 0.08 (0.04–0.18) and 0.28 (0.14–0.49) cases per patient year at the 8 recruiting centres. 42% of children were asymptomatic at the time of PA acquisition. The median (IQR) number of antibiotic courses per patient year varied between the centres: 0.6 (0.2–1.3) to 3.6 (3.1–4.2) for oral and 0.0 (0–0) to 0.4 (0–1.2) for intravenous. Conclusions This is the first prospective study to report the incidence of new PA infection in a large cohort of children with CF, considered to be free of PA airway infection. Incidence rate was higher in children who had isolated PA previously. The variation between centres is not easily explained and needs further investigation. Acknowledgments We would like to thank the Principal Investigators, research nurses and co-ordinators at each of the recruiting centres as well as the children and their families.

Physiologically based pharmacokinetic modeling of hydrogen cyanide levels in human breath.

Hydrogen cyanide (HCN) is a potent and fast-acting toxin increasingly recognized as an important cause of death in fire victims. Prompt diagnosis and treatment of cyanide poisoning are essential to avoid fatalities. Unfortunately, there are at present few rapid diagnostic methods. A noninvasive methodology would be to use HCN in exhaled air as a marker for systemic exposure. To explore this possibility, we developed a preliminary physiologically based pharmacokinetic model. The model suggests that breath HCN levels following inhalation exposure at near-lethal and lethal conditions are 0.1-1ppm, i.e., one to two orders of magnitude higher than the background breath level of about 0.01ppm in unexposed subjects. Hence, our results imply that breath analysis may be used as a rapid diagnostic method for cyanide poisoning.

Hydrogen cyanide concentrations in the breath of adult cystic fibrosis patients with and without Pseudomonas aeruginosa infection

Elevated concentrations of hydrogen cyanide (HCN) have been detected in the headspace of Pseudomonas aeruginosa (PA) cultures and in the breath of children with cystic fibrosis (CF) and PA infection. The use of mouth-exhaled breath HCN as a marker of PA infection in adults is more difficult to assess as some without PA infection generate HCN in their mouths. The analysis of breath exhaled via the nose, thereby avoiding volatile compounds produced in the mouth, will demonstrate elevated concentrations of HCN in adult CF patients chronically infected with PA. Using selected ion flow mass spectrometry (SIFT-MS), the mouth and the nose-exhaled breaths of 20 adult CF patients; 10 with chronic PA infection and 10 free from PA infection, were analysed for HCN. Acetone and ethanol were also measured as controls. SIFT-MS allows direct sampling and analysis of single breath exhalations, obviating the need to collect samples into bags or onto traps, which can compromise samples. HCN was detected in the mouth-exhaled breath of patients in both groups and in the nose-exhaled breath of patients with chronic PA infection. The difference in median (IQR) nose-exhaled HCN between the groups is statistically significant (11 (0.8–18) ppbv versus 0 (0–3.2) ppbv, p = 0.03). The concentrations of acetone and ethanol in nose-exhaled and mouth-exhaled breath are in keeping with previous studies. HCN in nose-exhaled breath is a biomarker of chronic airway infection with PA in adults with CF. Its application as a non-invasive diagnostic test for early PA infection warrants further investigation.

Quantification of hydrogen cyanide (HCN) in breath using selected ion flow tube mass spectrometry—HCN is not a biomarker of Pseudomonas in chronic suppurative lung disease

Hydrogen cyanide (HCN) in exhaled breath has been proposed as a biomarker for airway inflammation, and also a marker of the presence in the airways of specific organisms, especially Pseudomonas aeruginosa. However the production of HCN by salivary peroxidase in the oral cavity increases orally exhaled concentrations, and may not reflect the condition of the lower airways. Using SIFT-MS we aimed to determine an appropriate single-exhalation breathing maneuver which avoids the interference of HCN produced in the oral cavity. We have established that the SIFT-MS Voice200™ is suitable for the online measurement of HCN in exhaled breath. In healthy volunteers a significantly higher end exhaled HCN concentration was measured in oral exhalations compared to nasal exhalations (mean ± SD) 4.5 ± 0.6 ppb versus 2.4 ± 0.3 ppb, p < 0.01. For the accurate and reproducible quantification of end exhaled HCN in breath a nasal inhalation to full vital capacity and nasal exhalation at controlled flow is recommended. This technique was subsequently used to measure exhaled HCN in a group of patients with chronic suppurative lung disease (CSLD) and known microbiological colonization status to determine utility of HCN measurement to detect P. aeruginosa. Median nasal end exhaled HCN concentrations were higher in patients with CSLD (3.7 ppb) than normal subjects (2.0 ppb). However no differences between exhaled HCN concentrations of subjects colonized with P. aeruginosa and other organisms were identified, indicating that breath HCN is not a suitable biomarker of P. aeruginosa colonization.

P88 Is Hydrogen Cyanide a Marker of Burkholderia Cepacia Complex Infection?

IntroductionPseudomonas aeruginosa (PA) was thought to be the only organism found in the cystic fibrosis (CF) lung that produced hydrogen cyanide (HCN). A recent study used a cyanide selective electrode...

An investigation of suitable bag materials for the collection and storage of breath samples containing hydrogen cyanide

The SPACE study will assess exhaled breath hydrogen cyanide (HCN) concentrations as a marker of Pseudomonas aeruginosa (PA) infection in 240 children with cystic fibrosis (CF). It will use off-line selected ion flow tube mass spectrometry (SIFT-MS) analysis and so we needed to investigate which breath sampling bag material to use, the maximum storage time before analysis and the benefit of warming the bag samples. We studied 15 children with CF, 8 had chronic PA infection and 7 did not. Each exhaled directly into the instrument (on-line) and also into two 25 µm thick Nalophan (25N), two 70 µm Nalophan (70N) and two Tedlar® bags. Bags were stored at 20 or 37 °C. HCN concentrations were analysed at 1, 6, 24 and 48 h (off-line). Acetone and water vapour concentrations were also measured in parallel. Correlation between on-line and off-line concentrations measured by SIFT-MS was better for all compounds and bag types at 37 °C. The median (IQR) on-line HCN concentration was 8.9(4.4–13.7) parts per billion by volume, ppbv. Both on-line and off-line HCN concentrations were significantly higher in patients with PA infection than those without. At 37 °C the correlation between on-line and off-line HCN concentrations was good up to 6 h in the 25N bag (R2 = 0.79) and up to 24 h for the 70N and Tedlar bags (R2 = 0.82 and 0.86). The correlation between on- and off-line acetone concentrations at 37 °C was good up to 24 h in 25N, 70N and Tedlar bags (R2 = 0.89, 0.93 and 0.97). In all three types of bag the water vapour concentration fell quickly and by 24 h was equivalent to that of lab air. Samples stored in Tedlar or 70N bags, warmed to 37 °C and analysed within 24 h, give HCN and acetone concentrations which correlate well with on-line measurements.

Background levels and diurnal variations of hydrogen cyanide in breath and emitted from skin

The hydrogen cyanide (HCN) concentration in exhaled human breath and skin gas samples collected with different sampling techniques was measured using near-infrared cavity ring-down spectroscopy. The median baseline HCN concentrations in samples provided by 19 healthy volunteers 2–4 h after the last meal depended on the employed sampling technique: 6.5 parts per billion by volume (ppbv) in mixed (dead space and end-tidal) mouth-exhaled breath collected to a gas sampling bag, 3.9 ppbv in end-tidal mouth-exhaled breath, 1.3 ppbv in end-tidal nose-exhaled breath, 1.0 ppbv in unwashed skin and 0.6 ppbv in washed skin samples. Diurnal measurements showed that elevated HCN levels are to be expected in mouth-exhaled breath samples after food and drink intake, which suggests HCN generation in the oral cavity. The HCN concentrations in end-tidal nose-exhaled breath and skin gas samples were correlated, and it is concluded that these concentrations best reflect systemic HCN levels.

S128 Analysis of volatile biomarkers within exhaled breath for the diagnosis of pneumonia

IntroductionWhilst pneumonia is a common condition affecting both medical and surgical patients there is currently no definitive diagnostic test. One novel approach may be through the non-invasive analysis of volatile...

Background levels of hydrogen cyanide in human breath measured by infrared cavity ring down spectroscopy

Hydrogen cyanide (HCN) in breath has been suggested as a diagnostic tool for cyanide poisoning and for cyanide-producing bacterial infections. To distinguish elevated levels of breath HCN, baseline data are needed. Background levels of HCN were measured in mixed exhaled air from 40 healthy subjects (26 men, 14 women, age 21–61 years; detection limit: 1.5 ppb; median: 4.4 ppb; range <1.5–14 ppb) by near-infrared cavity ring down spectroscopy (CRDS). No correlation was observed with smoking habits, recent meals or age. However, female subjects had slightly higher breath levels of HCN than male subjects. CRDS has not previously been used for this purpose.

Washout kinetics of inhaled hydrogen cyanide in breath

Hydrogen cyanide (HCN) intoxication causes or contributes significantly to many of the fatalities among fire victims. To enable fast treatment of HCN poisoning, a more rapid diagnostic method than currently available is required. One possibility would be measurement in exhaled air. However, as HCN is highly water soluble, it may be absorbed during inhalation and reabsorbed during exhalation. If this, so-called, washin–washout effect is substantial it may interfere with the diagnosis, as a major part of breath HCN may originate from the respiratory tract, due to recent exposure, and not from systemic exposure. The aim of this study was to estimate the importance of the washin–washout effect of HCN. The time-course of cyanide in exhaled air was measured with an electrochemical detector in 10 volunteers during and after a 1 min × 10 ppm exposure to HCN. The experiment revealed an average half-life of 16 s (range 10–24 s) in breath. Extrapolating the results to higher exposures suggests that the contribution from washin–washout from the airways will be negligible even at fatal exposures. The results support the use of breath HCN as a potential indicator of systemic intoxication.

The origin of hydrogen cyanide in breath.

The excretion of hydrogen cyanide in breath and blood concentrations of cyanide were measured in eight normal subjects. There was no correlation between breath and blood levels of cyanide. Furthermore, breath cyanide concentrations calculated from blood values were much lower than measured values, which suggested a local production of hydrogen cyanide in the oropharynx. When saliva was incubated at 37 degrees C hydrogen cyanide was formed in the presence of air but not in a nitrogen atmosphere. No hydrogen cyanide was formed with boiled saliva and the production of hydrogen cyanide by native saliva was inhibited by catalase and by 6-n-propyl-thiouracil. Centrifugation of saliva resulted in a supernatant and a sediment, which were both required for the formation of hydrogen cyanide. Dialysis of the supernatant abolished its cyanide forming ability, which could be restored by addition of thiocyanate. We conclude that most of the hydrogen cyanide found in breath from normal human beings originates from oxidation of thiocyanate by salivary peroxidase in the oropharynx. As a consequence measurements of breath hydrogen cyanide can only be used to detect heavy exposure to cyanide.