Increased Arterial Carboxyhemoglobin Concentrations in Chronic Obstructive Pulmonary Disease

Lipid metabolism reprogramming in chronic obstructive pulmonary disease

Chronic Obstructive Pulmonary Disease (COPD) is a complex and diverse respiratory disorder, characterized by ongoing respiratory symptoms and restricted airflow. The major clinical manifestations typically encompass chronic cough, sputum production, and wheezing. The main pathological characteristics involve infiltration of inflammatory cells, overproduction of mucus, and damage to the alveolar walls. The underlying causes of COPD are complex and remain incompletely elucidated, thought to originate from the combined effect of various factors. Lipids, as hydrophobic molecules, fulfill three fundamental functions: energy storage, membrane biosynthesis, and signal transduction. Lipid metabolism is intricately intertwined with various metabolic pathways and plays a pivotal role in the complex pathogenesis of COPD. Delving into lipid metabolism, as well as the particular modifications and roles of lipid molecules in cells, is of paramount importance in the context of COPD. This review primarily aims to elucidate the role of fatty acid metabolism in the onset and progression of COPD. Additionally, it examines the potential of lipid metabolism reprogramming as a promising therapeutic approach, illuminating new paths for the management and treatment of this disabling respiratory condition.

Association of blood carboxyhemoglobin levels with mortality and neurological outcomes in out-of-hospital cardiac arrest

Background

Carbon monoxide (CO), produced endogenously by heme oxygenase-1, plays a crucial role in the immune system by mitigating cellular damage under stress. However, the significance of carboxyhemoglobin (COHb) levels after out-of-hospital cardiac arrest (OHCA) is not well understood. This study aimed to explore the association between COHb levels at hospital arrival and within the first 24 h post-arrival with 30-day mortality and neurological outcomes in patients who experienced OHCA.

Methods

This single-center, retrospective study analyzed data from adult patients who experienced OHCA seen at Okayama University Hospital from 2019 to 2023. The patients were assigned to one of two study groups based on COHb levels (0.0% or ≥0.1%) upon hospital arrival. The primary outcome was 30-day mortality.

Results

Among the 560 eligible patients who experienced OHCA, 284 (50.7%) were in the COHb 0.0% group and 276 (49.3%) were in the COHb ≥ 0.1% group. The 30-day mortality was significantly higher in the COHb 0.0% group compared to the COHb ≥ 0.1% group (264 [92.9%] vs. 233 [84.4%]). Multivariable logistic regression showed that the COHb 0.0% group was associated with 30-day mortality (adjusted ORs: 2.24, 95% CIs: 1.10-4.56). Non-survivors at 30 days who were admitted to the intensive care unit had lower COHb levels at hospital arrival (0.0% vs. 0.2%) and lower mean COHb levels during the first 24 h post-arrival (0.7% vs. 0.9%) compared to survivors.

Conclusions

COHb levels of 0.0% were linked to worse outcomes in patients experiencing OHCA, warranting further research on the prognostic implications of COHb in this context.

Investigation on the relationship between hemoglobin concentration and stroke risk: a bidirectional Mendelian randomization study

Background

The relationship between hemoglobin concentration and stroke has garnered significant interest in the research community. However, findings from published observational epidemiological studies on this relationship have been inconclusive. By using publicly available genome-wide association study (GWAS) aggregated statistics, a two-sample Mendelian randomization analysis is conducted to explore the causal relationship between hemoglobin concentration and stroke.

Methods

Summary statistics data from UK Biobank for hemoglobin concentration and from the FinnGen R9 and MEGASTROKE consortium for stroke are used. A series of quality control steps are taken to select eligible instrumental SNPs closely related to exposure. In order to make the conclusion more robust and reliable, several robust analysis methods are employed including inverse variance weighted, weighted median, MR-Egger regression, which are based on different assumptions of two-sample MR Analysis. Meanwhile, sensitivity analyses such as pleiotropy test and MR-Egg regression, are performed to mitigate horizontal pleiotropy and heterogeneity.

Results

The two-sample Mendelian randomized study indicates a negative association between hemoglobin concentration and stroke, suggesting that hemoglobin concentration acts as a protective factor against stroke. From the FinnGen database, there is a negative association between hemoglobin concentration and stroke, with an odds ratio (OR) of 0.82 and a 95% confidence interval (CI) of 0.73-0.92, p = 0.0006. Similarly, the MEGASTROKE database findings reinforce this observation. The negative association between hemoglobin concentration and stroke (OR: 0.91, 95%CI: 0.83-1.00, p = 0.040), ischemic stroke (OR: 0.87, 95%CI: 0.79-0.96, p = 0.004), and cardiogenic stroke (OR: 0.82, 95% CI: 0.69-0.99, p = 0.039) further suggests that higher hemoglobin levels might confer a protective effect against these conditions.

Conclusion

Hemoglobin concentration serves as a protective factor against stroke, and managing abnormal hemoglobin levels can effectively reduce the incidence of stroke.

U-Shaped Association Between Carboxyhemoglobin and Mortality in Patients With Acute Respiratory Distress Syndrome on Venovenous Extracorporeal Membrane Oxygenation

Background

Carbon monoxide (CO) is an endogenous signaling molecule that activates cytoprotective programs implicated in the resolution of acute respiratory distress syndrome (ARDS) and survival of critical illness. Because CO levels can be measured in blood as carboxyhemoglobin, we hypothesized that carboxyhemoglobin percent (COHb%) may associate with mortality.

OBJECTIVES

To examine the relationship between COHb% and outcomes in patients with ARDS requiring venovenous extracorporeal membrane oxygenation (ECMO), a condition where elevated COHb% is commonly observed.

DESIGN

Retrospective cohort study.

SETTING

Academic medical center ICU.

PATIENTS

Patients were included that had ARDS on venovenous ECMO.

MEASUREMENTS AND MAIN RESULTS

We examined the association between COHb% and mortality using a Cox proportional hazards model. Secondary outcomes including ECMO duration, ventilator weaning, and hospital and ICU length of stay were examined using both subdistribution and causal-specific hazard models for competing risks. We identified 109 consecutive patients for analysis. Mortality significantly decreased per 1 U increase in COHb% below 3.25% (hazard ratio [HR], 0.35; 95% CI, 0.15-0.80; p = 0.013) and increased per 1 U increase above 3.25% (HR, 4.7; 95% CI, 1.5-14.7; p = 0.007) reflecting a nonlinear association (p = 0.006). Each unit increase in COHb% was associated with reduced likelihood of liberation from ECMO and mechanical ventilation, and increased time to hospital and ICU discharge (all p < 0.05). COHb% was significantly associated with hemolysis but not with initiation of hemodialysis or blood transfusions.

CONCLUSIONS

In patients with ARDS on venovenous ECMO, COHb% is a novel biomarker for mortality exhibiting a U-shaped pattern. Our findings suggest that too little CO (perhaps due to impaired host signaling) or excess CO (perhaps due to hemolysis) is associated with higher mortality. Patients with low COHb% may exhibit the most benefit from future therapies targeting anti-oxidant and anti-inflammatory pathways such as low-dose inhaled CO gas.

An evolutionary machine learning for pulmonary hypertension animal model from arterial blood gas analysis

Pulmonary hypertension (PH) is a rare and fatal condition that leads to right heart failure and death. The pathophysiology of PH and potential therapeutic approaches are yet unknown. PH animal models' development and proper evaluation are critical to PH research. This work presents an effective analysis technology for PH from arterial blood gas analysis utilizing an evolutionary kernel extreme learning machine with multiple strategies integrated slime mould algorithm (MSSMA). In MSSMA, two efficient bee-foraging learning operators are added to the original slime mould algorithm, ensuring a suitable trade-off between intensity and diversity. The proposed MSSMA is evaluated on thirty IEEE benchmarks and the statistical results show that the search performance of the MSSMA is significantly improved. The MSSMA is utilised to develop a kernel extreme learning machine (MSSMA-KELM) on PH from arterial blood gas analysis. Comprehensively, the proposed MSSMA-KELM can be used as an effective analysis technology for PH from arterial Blood gas analysis with an accuracy of 93.31%, Matthews coefficient of 90.13%, Sensitivity of 91.12%, and Specificity of 90.73%. MSSMA-KELM can be treated as an effective approach for evaluating mouse PH models.

Carboxyhemoglobin Does Not Predict the Need of Mechanical Ventilation and Prognosis during COPD Exacerbation

Background

Carboxyhemoglobin (COHb) is a complex formed by the binding of carbon monoxide to hemoglobin in blood. Higher COHb levels have been associated with poor prognosis in a variety of pulmonary disorders. However, little is known regarding the prognostic significance of COHb among individuals with chronic obstructive pulmonary disease (COPD) exacerbation.

Methods

In a retrospective study, we evaluated associations of venous COHb levels on hospital admission with the need for invasive mechanical ventilation, in-hospital mortality, and rehospitalization, among 300 patients hospitalized for COPD exacerbation in internal medical wards.

Results

Rates of in-hospital death and 1-year recurrent hospitalizations were 11.0% and 59.6%, respectively. COHb levels were not significantly associated with in-hospital mortality (OR = 0.82, P=0.25, 95% CI 0.59–1.15) or with 1-year rehospitalizations (OR = 0.91, P=0.18, 95% CI 0.79–1.04). The mean COHb level did not differ significantly between patients who needed invasive mechanical ventilation and those who were not invasively mechanically ventilated during the current hospitalization (2.01 ± 1.42% vs. 2.19 ± 1.68%, P=0.49).

Conclusions

Among patients hospitalized with COPD exacerbation in internal medicine wards, COHb levels on admission were not associated with invasive mechanical ventilation treatment, rehospitalizations, or mortality.

Endogenous Carboxyhemoglobin Level Variation in COVID-19 and Bacterial Sepsis: A Novel Approach?

Background: The increased production of carbon monoxide (CO) in sepsis has been proven, but the blood level variations of carboxyhemoglobin (COHb) as a potential evolutionary parameter of COVID-19 and sepsis/septic shock have yet to be determined. This study aims to evaluate the serum level variation of COHb as a potential evolutionary parameter in COVID-19 critically ill patients and in bacterial sepsis. Materials and method: A prospective and observational study was conducted on two groups of patients: the bacterial sepsis group (n = 52) and the COVID-19 group (n = 52). We followed paraclinical parameters on Day 1 (D1) and Day 5 (D5) of sepsis/ICU admission for COVID-19 patients. Results: D1 of sepsis: statistically significant positive correlations between: COHb values and serum lactate (p = 0.024, r = 0.316), and total bilirubin (p = 0.01, r = 0.359). In D5 of sepsis: a statistically significant positive correlations between: COHb values and procalcitonin (PCT) (p = 0.038, r = 0.402), and total bilirubin (p = 0.023, r = 0.319). D1 of COVID-19 group: COHb levels were statistically significantly positively correlated with C-reactive protein CRP values (p = 0.003, r = 0.407) and with PCT values (p = 0.022, r = 0.324) and statistically significantly negatively correlated with serum lactate values (p = 0.038, r = −0.285). Conclusion: COHb variation could provide rapid information about the outcome of bacterial sepsis/septic shock, having the advantages of a favorable cost-effectiveness ratio, and availability as a point-of-care test.

Carboxyhaemoglobin levels and free-radical-related diseases in prematurely born infants

BACKGROUND

Carboxyhaemoglobin (COHb) levels may reflect the level of early oxidative stress which plays a role in mediating free-radical-related diseases in prematurely born infants.

AIM

To assess the relationship of COHb levels in the first seven days of after birth to the development of bronchopulmonary dysplasia (BPD) and other free-radical-related diseases.

STUDY DESIGN

Retrospective analysis of routinely performed COHb via blood gas samples of infants born at less than 30 weeks of gestation admitted to a tertiary neonatal intensive care unit was undertaken.

SUBJECTS

One hundred and four infants were included with a median (range) gestational age of 27.4 (22.4-29.9) weeks and a birthweight of 865 (395-1710) grams.

OUTCOMES

The maximum COHb per infant per day was recorded for the first 28 days and BPD and other free-radical-related diseases including intraventricular haemorrhage (IVH) were noted. The severity of BPD, requirement for home oxygen on discharge and survival to discharge were also recorded.

RESULTS

Infants who developed BPD (n = 76) had significantly higher COHb levels in the first seven days [1.7% (0.3-6.8)] compared to those that did not develop BPD [1.6% (0.9-3.8); p = 0.001]. Higher COHb levels in the first seven days after birth were also observed in infants with grade three/four IVH [n = 20; 1.9% (1.0-6.8)] compared to those without [1.6% (0.3-5.6); p < 0.001]. COHb levels, however, were not associated with the duration of ventilation, BPD severity or survival to discharge.

CONCLUSION

Higher COHb levels in prematurely born infants were associated with the development of BPD and IVH.

Is endogenous carboxyhaemoglobin level a useful biomarker of clinical course and prognosis in COVID-19 patients?

OBJECTIVE

SARS-CoV-2 has caused nearly 4 million confirmed cases of COVID-19 worldwide in the approximately 4 months since it emerged in Wuhan, China in December 2019. Comorbidities increase morbidity and mortality in COVID-19, and many laboratory parameters have been associated with mortality. The aim of the present study was to identify the relationship between endogenous carboxyhaemoglobin (COHb) level and the clinical course and prognosis of COVID-19.

METHODS

The study included 48 non-smokers or ex-smokers aged 18 years or older who presented to the emergency department, were diagnosed with COVID-19 by real-time PCR analysis of nasopharyngeal swab sample and were treated in the pulmonary diseases ward of the Atatürk University hospital after 24 March 2020 and 15 April 2020. The patients' laboratory parameters and demographic data were analysed retrospectively.

RESULTS

Prothrombin time and C-reactive protein (CRP), troponin-I, and D-dimer levels decreased in COVID-19 patients during follow-up (P = .024, P = .001, P = .001, P = .001), while PaO₂ /FiO₂ ratio and COHb increased (P = .002, P = .001). COHb level at admission was significantly lower in patients who developed macrophage activation syndrome (MAS), acute respiratory distress syndrome (ARDS), and those who died compared with the other patients (P = .002, P = .001). COHb level on day 5 of treatment was significantly higher in patients with ARDS and patients who died (P = .001, P = .001). Significant correlations were detected between COHb level and CRP (r=-0.425, P = .001), ferritin (r = -.395, P = .001) and PaO₂ /FiO₂ ratio (r = .431, P = .001).

CONCLUSIONS

COHb level may be an easily accessible biomarker that guides early follow-up and treatment planning to avoid ARDS, MAS and mortality in COVID-19.

Regulation of inflammation by the antioxidant haem oxygenase 1

Haem oxygenase 1 (HO-1), an inducible enzyme responsible for the breakdown of haem, is primarily considered an antioxidant, and has long been overlooked by immunologists. However, research over the past two decades in particular has demonstrated that HO-1 also exhibits numerous anti-inflammatory properties. These emerging immunomodulatory functions have made HO-1 an appealing target for treatment of diseases characterized by high levels of chronic inflammation. In this Review, we present an introduction to HO-1 for immunologists, including an overview of its roles in iron metabolism and antioxidant defence, and the factors which regulate its expression. We discuss the impact of HO-1 induction in specific immune cell populations and provide new insights into the immunomodulation that accompanies haem catabolism, including its relationship to immunometabolism. Furthermore, we highlight the therapeutic potential of HO-1 induction to treat chronic inflammatory and autoimmune diseases, and the issues faced when trying to translate such therapies to the clinic. Finally, we examine a number of alternative, safer strategies that are under investigation to harness the therapeutic potential of HO-1, including the use of phytochemicals, novel HO-1 inducers and carbon monoxide-based therapies.

Role of methemoglobin and carboxyhemoglobin levels in predicting COVID-19 prognosis: an observational study

World Health Organization has declared coronavirus disease-19 (COVID-19) as a pandemic. Although there are studies about this novel virus, our knowledge is still limited. There is limited information about its diagnosis, treatment and prognosis. We aimed to investigate the effect of methemoglobin and carboxyhemoglobin levels on the prognosis of COVID-19. In this observational study, patients who were diagnosed with COVID-19 during March 1–April 31, 2020 in a secondary-level state hospital in Turkey were included in the study. COVID-19 diagnosis was confirmed with reverse transcription polymerase chain reaction method, with nasal, oral or sputum specimens. During the period this study was performed, 3075 patients were tested for COVID-19 and 573 of them were hospitalized. Among the hospitalised patients, 23.2% (133) of them had a positive polymerase chain reaction result for COVID-19. A total of 125 patients, 66 (52.8%) males and 59 (47.2%) females, with an average age of 50.2 ± 19.8 years, were included in the study. The most common findings in chest radiogram were ground-glass areas and consolidations, while one-third of the patients had a normal chest radiogram. Computed thorax tomography was performed for 77.6% (97/125) of the patients. The 24.7% of computed tomographies (24/97) did not reveal any pathological findings, and the most common findings were ground-glass appearance and consolidation. Those who needed intensive care had statistically significantly lower platelet count (P = 0.011) and higher lactate dehydrogenase levels (P < 0.001). No statistically significant difference was found in carboxyhemoglobin (P = 0.395) and methemoglobin (P = 1.000) levels. We found that carboxyhemoglobin and methemoglobin levels had no effect on COVID-19 prognosis, but low platelet level played a role in predicting COVID-19 prognosis. This study was approved by the Ethical Committee of Harran University Faculty of Medicine on May 11, 2020 with approval No. 09.

Protocol for the cultural adaptation of pulmonary rehabilitation and subsequent testing in a randomised controlled feasibility trial for adults with chronic obstructive pulmonary disease in Sri Lanka

INTRODUCTION

International guidelines recommend pulmonary rehabilitation (PR) should be offered to adults living with chronic obstructive pulmonary disease (COPD), but PR availability is limited in Sri Lanka. Culturally appropriate PR needs to be designed and implemented in Sri Lanka. The study aims to adapt PR to the Sri Lankan context and determine the feasibility of conducting a future trial of the adapted PR in Sri Lanka.

METHODS AND ANALYSIS

Eligible participants will be identified and will be invited to take part in the randomised controlled feasibility trial, which will be conducted in Central Chest Clinic, Colombo, Sri Lanka. A total of 50 participants will be recruited (anticipated from April 2021) to the trial and randomised (1:1) into one of two groups; control group receiving usual care or the intervention group receiving adapted PR. The trial intervention is a Sri Lankan-specific PR programme, which will consist of 12 sessions of exercise and health education, delivered over 6 weeks. Focus groups with adults living with COPD, caregivers and nurses and in-depth interviews with doctors and physiotherapist will be conducted to inform the Sri Lankan specific PR adaptations. After completion of PR, routine measures in both groups will be assessed by a blinded assessor. The primary outcome measure is feasibility, including assessing eligibility, uptake and completion. Qualitative evaluation of the trial using focus groups with participants and in-depth interviews with PR deliverers will be conducted to further determine feasibility and acceptability of PR, as well as the ability to run a larger future trial.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the ethics review committee of Faculty of Medical Sciences, University of Sri Jayewardenepura, Sri Lanka and University of Leicester, UK. The results of the trial will be disseminated through patient and public involvement events, local and international conference proceedings, and peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ISRCTN13367735.

Admission Carboxyhemoglobin: Is It a Marker for Burn Patient Outcomes?

BACKGROUND

Carbon monoxide is a gas produced by the combustion of hydrocarbon products that binds to heme molecules, 240 times more than oxygen, producing carboxyhemoglobin (COHb). As a result of its high affinity, there is shift of the oxyhemoglobin dissociation curve, compromising oxygen transport and delivery to tissues. Our study aim was to evaluate COHb elevation on admission as a predictor of worse outcomes in burn patients.

METHODS

This is a 10-year retrospective review of the American Burn Association Burn Registry from 2002 to 2011. We stratified the patients into 2 groups: adult patients with normal COHb on admission (group 1) versus elevated COHb (group 2). Elevated COHb levels were defined as greater than 10% on the first arterial blood gas. Outcome measures included in-hospital mortality rate, hospital length of stay (LOS), intensive care unit LOS (ICU-LOS), and ventilator days. χ and t test analyses were used with significance defined as a P value of less than 0.05.

RESULTS

A total of 6365 burn patients meet our inclusion criteria. There were 5775 patients in group 1 and 590 patients in group 2. Group 1 had an average age of 39.29 years compared with 42.62 years in group 2. The total body surface area was higher in group 1 compared with group 2 (6.24 vs 4.65) and with a statistically significant increase in partial thickness burns at 4.97 in group 1 compared with 3.27 in group 2. There was no statistically significant difference between the 2 groups in terms of full thickness total body surface area. The hospital LOS was significantly higher in group 2 compared with group 1 (15.34 vs 9.66). There was a significantly higher ICU-LOS at 12.89 days in group 2 compared with 4.01 in the group 1 (P = 0.0001, t test). There were higher ventilator days in group 2 at 9.23 than those in group 1 at 2.05 (P < 0.0001, t test). The in-hospital mortality was also significantly higher in group 2 at 15.59% than in group 1 at 1.33% (P = 0.0001, χ).

CONCLUSIONS

Elevated COHb on admission was associated with an increased hospital and ICU-LOS, average ventilator days, and in-hospital mortality. The presence of elevated COHb of greater than 10% on an initial arterial blood gas suggests worse outcomes and increased need of resource utilization during the index hospital admission.

Low-Dose Carbon Monoxide Inhibits Rhinovirus Replication in Human Alveolar and Airway Epithelial Cells

Carbon monoxide (CO) and nitric oxide (NO) exhibit physiological properties that include the activation of guanylate cyclase. NO inhibits replication of rhinovirus (RV), a major cause of the common cold and exacerbation of bronchial asthma and chronic obstructive pulmonary disease. However, the anti-rhinoviral effects of CO remain unclear. This study investigated whether the exogenous application of low-dose CO could inhibit RV replication in human alveolar and airway epithelial cells. A549 human lung carcinoma cells with alveolar epithelial features and primary cultures of human tracheal epithelial (HTE) cells were pretreated with CO (100 ppm) and infected with a major group RV, type 14 RV (RV14). CO exposure reduced RV14 titers in the supernatants and RV RNA levels in A549 and HTE cells. The treatment with a guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, reversed the inhibitory effects of CO exposure on RV14 replication in A549 cells. Pretreatment of A549 cells with 8-Br-cGMP, a cell-permeable cGMP analog, caused the decrease in RV14 replication, while CO exposure increased cGMP production. CO exposure also increased the expression levels of interferon (IFN)-γ mRNA and protein. In contrast, pretreatment with CO did not increase DNA fragmentation and did not reduce the expression of intercellular adhesion molecule-1, the RV14 receptor, or the number of acidic endosomes, through which RV RNA enters the cytoplasm. These findings suggest that low-dose CO may decrease RV14 replication in alveolar and airway epithelial cells. IFN-γ production, which is induced by CO exposure via guanylate cyclase activation-mediated cGMP production, may be involved in RV14 replication inhibition.

The influence of anemia on one-year exacerbation rate of patients with COPD-PH

BACKGROUND

Anemia is prevalent not only in COPD but also in pulmonary hypertension. We postulated that anemia may have certain prognostic value in COPD concomitant with PH due to COPD (COPD-PH).

METHODS

We performed a 12-month prospective investigation to follow up COPD patients with or without PH assessed by right heart catheterization. Eligible patients were enrolled, stratified into COPD-PH-anemia group (n = 40), COPD-PH group (n = 42), COPD-anemia group (n = 48), and COPD group(n = 50), and then followed up for 12 months.

RESULTS

After the follow-up, for both of the actual variation value and variation rate, the increase of NT-pro BNP (P<0.001; P = 0.03) and CAT score (P = 0.001; 0.002), as well as the decrease of PaO₂ (P = 0.03; 0.086) and Peak VO₂ (P = 0.021; 0.009) in COPD-PH-anemia group were highest among four groups. The cumulative one-year survival rates were similar among four groups (P = 0.434). The cumulative exacerbation-free rate was lowest in COPD-PH-anemia group among four groups (P<0.001). Hemoglobin was an independent promoting factor for the probability of hospitalization due to exacerbation ≧ 1/year in patients with COPD-PH-anemia [HR 3.121(2.325-5.981); P<0.001].

CONCLUSIONS

Anemia is a promoting factor for the worsening of exercise capacity, deterioration of hypoxemia, declining of life quality, and aggravation of exacerbations in patients with COPD-PH-anemia, by contrast with COPD-PH, COPD-anemia, and COPD.

[Biomarkers of Smoking - Which Cut-Off Values Should be Used?]

Biomarkers of Smoking - Which Cut-Off Values Should be Used? Abstract. Verification of smoking status by means of biomarkers is important for treatment decisions of patients with smoking-related diseases. Cotinine is currently the best biomarker to document nicotine consumption. A low cost alternative method to determine smoking status is by measurement of carboxyhemoglobin (CO-Hb) in the exhaled breath. The main disadvantage of CO-Hb is the short half-life. The appropriate cut-off value for active nicotine consumption in Switzerland is 50 ng/ml or higher cotinine in the urine or 10 ng/ml and 12 ng/ml in serum and saliva, respectively. CO-Hb levels greater than 2 % indicate smoking with high probability, levels above 3 % with very high probability.

Carboxyhemoglobin Levels Induced by Cigarette Smoking Outdoors in Smokers

INTRODUCTION

Non-invasive screening of carboxyhemoglobin saturation (SpCO) in the emergency department to detect occult exposure is increasingly common. The SpCO threshold to consider exposure in smokers is up to 9%. The literature supporting this cutoff is inadequate, and the impact of active smoking on SpCO saturation remains unclear. The primary objective was to characterize baseline SpCO in a cohort of smokers outdoors. Secondary objectives were to explore the impact of active smoking on SpCO and to compare SpCO between smokers and non-smokers.

METHODS

This was a prospective cohort pilot study in two outdoor urban public areas in the USA, in a convenience sample of adult smokers. SpCO saturations were assessed non-invasively before, during, and 2 min after cigarette smoking with pulse CO-oximetry. Analyses included descriptive statistics, correlations, and a generalized estimating equation model.

RESULTS

Eighty-five smokers had mean baseline SpCO of 2.7% (SD 2.6) and peak of 3.1% (SD 2.9), while 15 controls had SpCO 1.3% (SD 1.3). This was a significant difference. Time since last cigarette was associated with baseline SpCO, and active smoking increased mean SpCO. There was correlation among individual smokers' SpCO levels before, during, and 2 min after smoking, indicating smokers tended to maintain their baseline SpCO level.

CONCLUSIONS

This study is the first to measure SpCO during active smoking in an uncontrolled environment. It suggests 80% of smokers have SpCO ≤ 5%, but potentially lends support for the current 9% as a threshold, depending on clinical context.

Use of carboxyhemoglobin as a biomarker of environmental CO exposure: critical evaluation of the literature

Carbon monoxide (CO) poisoning is the primary cause for access to emergency department (ED) services for more than 50,000 persons in Europe and the USA every year. CO poisoning diagnosis is based on multiple factors and is usually confirmed by high carboxyhemoglobin (COHb) levels in the blood. We conducted a systematic evaluation of literature to investigate the usefulness of COHb as a biomarker of environmental CO exposure. We conducted an electronic search in Medline, Embase, and the Cochrane Library databases. We selected studies reporting high or low environmental CO concentrations, as well as COHb levels in exposed subjects presenting in ED or staying at home. We included 19 studies, but only 7 studies reported environmental CO concentration and proved a correlation between COHb and CO exposure in healthy and non-smoker subjects only. However, confounding factors were often incompletely assessed. The main symptoms reported were headache, nausea, vertigo and vomiting. COHb data stored in healthcare databases were used in six studies and provided useful information about symptoms, CO sources and patient characteristics. Most studies were classified at risk of bias. This review indicates that COHb is the most commonly used biomarker to assess CO exposure and seems to be useful. Further studies are needed to establish the reliability of COHb as a biomarker and/or explore other possible biomarkers. Surveillance systems of the general population, correlated with geographical locations and other confounding factors, could be important for CO exposure monitoring and the development of focused prevention programs.

Determinants of Carboxyhemoglobin Levels and Relationship with Sepsis in a Retrospective Cohort of Preterm Neonates

Carboxyhemoglobin levels in blood reflect endogenous carbon monoxide production and are often measured during routine blood gas analysis. Endogenous carbon monoxide production has been reported to be increased during sepsis, but carboxyhemoglobin levels have not been thoroughly evaluated as a biomarker of sepsis. We sought to determine whether carboxyhemoglobin levels were elevated during sepsis in a high risk population of premature neonates. We conducted a retrospective cohort study of 30 infants in two neonatal intensive care units using electronic medical and laboratory records. The majority of infants were extremely premature and extremely low birth weight, and 25 had at least one episode of sepsis. We collected all carboxyhemoglobin measurements during their in-patient stay and examined the relationship between carboxyhemoglobin and a variety of clinical and laboratory parameters, in addition to the presence or absence of sepsis, using linear mixed-effect models. We found that postnatal age had the most significant effect on carboxyhemoglobin levels, and other significant associations were identified with gestational age, hemoglobin concentration, oxyhemoglobin saturation, and blood pH. Accounting for these covariates, there was no significant relationship between the onset of sepsis and carboxyhemoglobin levels. Our results show that carboxyhemoglobin is unlikely to be a clinically useful biomarker of sepsis in premature infants, and raise a note of caution about factors which may confound the use of carbon monoxide as a clinical biomarker for other disease processes such as hemolysis.

Carboxyhemoglobin Formation in Preterm Infants Is Related to the Subsequent Development of Bronchopulmonary Dysplasia

OBJECTIVE

To evaluate the usefulness of carboxyhemoglobin (CO-Hb) levels as a biomarker to predict the development and severity of bronchopulmonary dysplasia (BPD).

METHODS

Twenty-five infants born at <33 wk of gestational age or with a birth weight of <1,500 g were enrolled. CO-Hb levels were measured between postnatal days 5 and 8, 12 and 15, 19 and 22, and 26 and 29. Urinary levels of 8-hydroxydeoxyguanosine (8-OHdG), advanced oxidation protein products, and Nε-(hexanoyl) lysine were measured between postnatal days 5 and 8 and 26 and 29. Receiver operating characteristic (ROC) analysis was used to compare the biomarkers' predictive values.

RESULTS

Compared with infants in the no-or-mild BPD group, infants with moderate-to-severe BPD exhibited higher CO-Hb levels during the early postnatal period and higher 8-OHdG levels between postnatal days 5 and 8. Using ROC analysis to predict the development of moderate-to-severe BPD, the area under the curve (AUC) for CO-Hb levels between postnatal days 5 and 8 was higher than AUCs for the urinary markers.

CONCLUSIONS

CO-Hb levels during the early postnatal period may serve as a practical marker for evaluating oxidative stress and the severity of subsequently developing BPD.

Carbon monoxide in exhaled breath testing and therapeutics

Carbon monoxide (CO), a low molecular weight gas, is a ubiquitous environmental product of organic combustion, which is also produced endogenously in the body, as the byproduct of heme metabolism. CO binds to hemoglobin, resulting in decreased oxygen delivery to bodily tissues at toxicological concentrations. At physiological concentrations, CO may have endogenous roles as a potential signaling mediator in vascular function and cellular homeostasis. Exhaled CO (eCO), similar to exhaled nitric oxide (eNO), has been evaluated as a candidate breath biomarker of pathophysiological states, including smoking status, and inflammatory diseases of the lung and other organs. eCO values have been evaluated as potential indicators of inflammation in asthma, stable COPD and exacerbations, cystic fibrosis, lung cancer, or during surgery or critical care. The utility of eCO as a marker of inflammation and its potential diagnostic value remain incompletely characterized. Among other candidate 'medicinal gases' with therapeutic potential, (e.g., NO and H2S), CO has been shown to act as an effective anti-inflammatory agent in preclinical animal models of inflammatory disease, acute lung injury, sepsis, ischemia/reperfusion injury and organ graft rejection. Current and future clinical trials will evaluate the clinical applicability of this gas as a biomarker and/or therapeutic in human disease.

Virus infection-induced bronchial asthma exacerbation

Infection with respiratory viruses, including rhinoviruses, influenza virus, and respiratory syncytial virus, exacerbates asthma, which is associated with processes such as airway inflammation, airway hyperresponsiveness, and mucus hypersecretion. In patients with viral infections and with infection-induced asthma exacerbation, inflammatory mediators and substances, including interleukins (ILs), leukotrienes and histamine, have been identified in the airway secretions, serum, plasma, and urine. Viral infections induce an accumulation of inflammatory cells in the airway mucosa and submucosa, including neutrophils, lymphocytes and eosinophils. Viral infections also enhance the production of inflammatory mediators and substances in airway epithelial cells, mast cells, and other inflammatory cells, such as IL-1, IL-6, IL-8, GM-CSF, RANTES, histamine, and intercellular adhesion molecule-1. Viral infections affect the barrier function of the airway epithelial cells and vascular endothelial cells. Recent reports have demonstrated augmented viral production mediated by an impaired interferon response in the airway epithelial cells of asthma patients. Several drugs used for the treatment of bronchial asthma reduce viral and pro-inflammatory cytokine release from airway epithelial cells infected with viruses. Here, I review the literature on the pathogenesis of the viral infection-induced exacerbation of asthma and on the modulation of viral infection-induced airway inflammation.

Breath biomarkers in diagnosis of pulmonary diseases

Breath analysis provides a convenient and simple alternative to traditional specimen testing in clinical laboratory diagnosis. As such, substantial research has been devoted to the analysis and identification of breath biomarkers. Development of new analytes enhances the desirability of breath analysis especially for patients who monitor daily biochemical parameters. Elucidating the physiologic significance of volatile substances in breath is essential for clinical use. This review describes the use of breath biomarkers in diagnosis of asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), lung cancer, as well as other pulmonary diseases. A number of breath biomarkers in lung pathophysiology will be described including nitric oxide (NO), carbon monoxide (CO), hydrogen peroxide (H₂O₂) and other hydrocarbons.

Carboxyhemoglobin levels in medical intensive care patients: a retrospective, observational study

Introduction

Critical illness leads to increased endogenous production of carbon monoxide (CO) due to the induction of the stress-response enzyme, heme oxygenase-1 (HO-1). There is evidence for the cytoprotective and anti-inflammatory effects of CO based on animal studies. In critically ill patients after cardiothoracic surgery, low minimum and high maximum carboxyhemoglobin (COHb) levels were shown to be associated with increased mortality, which suggests that there is an 'optimal range' for HO-1 activity. Our study aimed to test whether this relationship between COHb and outcome exists in non-surgical ICU patients.

Methods

We conducted a retrospective, observational study in a medical ICU at a university hospital in Vienna, Austria involving 868 critically ill patients. No interventions were undertaken. Arterial COHb was measured on admission and during the course of treatment in the ICU. The association between arterial COHb levels and ICU mortality was evaluated using bivariate tests and a logistic regression model.

Results

Minimum COHb levels were slightly lower in non-survivors compared to survivors (0.9%, 0.7% to 1.2% versus 1.2%, 0.9% to 1.5%; P = 0.0001), and the average COHb levels were marginally lower in non-survivors compared to survivors (1.5%, 1.2% to 1.8% versus 1.6%, 1.4% to 1.9%, P = 0.003). The multivariate logistic regression analysis revealed that the association between a low minimum COHb level and increased mortality was independent of the severity of illness and the type of organ failure.

Conclusions

Critically ill patients surviving the admission to a medical ICU had slightly higher minimum and marginally higher average COHb levels when compared to non-survivors. Even though the observed differences are statistically significant, the minute margins would not qualify COHb as a predictive marker for ICU mortality.

A new strategy with proton pump inhibitors for the prevention of acute exacerbations in COPD

Acute exacerbations of chronic obstructive pulmonary disease (COPD), an acute worsening of respiratory symptoms, generally result in a poor prognosis. Successful prevention and management of such exacerbations is thus important for patient care. Viral infection, primarily with rhinovirus (RV), is the foremost cause of exacerbations in COPD patients. Proton pump inhibitors (PPIs) have been reported to inhibit RV infection in human airway epithelial cells in vitro. Furthermore, clinical trials of PPIs in patients with COPD resulted in a reduction in rates of both common cold and COPD exacerbations. In this review, we discuss the significance of COPD exacerbations, summarize a published trial of the effect of low-dose PPIs on COPD exacerbations, and postulate a mechanism for this effect.

Exhaled carbon monoxide in airway diseases: from research findings to clinical relevance

Breath tests have gained increasing interest in recent years mainly driven by the unmet clinical need to monitor airway diseases and to obtain information of unravelled aspects of respiratory disorders. Carbon monoxide is present in the exhaled breath and has been suggested to reflect ongoing oxidative stress, even if there are some confounding factors limiting its clinical usefulness. Increased concentration of exhaled carbon monoxide has been demonstrated in different acute and chronic airway diseases including allergic rhinitis, asthma, bronchiectasis, and post transplant bronchiolitis obliterans syndrome. Although exhaled carbon monoxide might not prove as a clinically useful biomarker of airway diseases, its measurement has helped to understand the place of heme oxygenase activity in allergic and non-allergic airway diseases. The scope of this review is the exciting field of exhaled carbon monoxide in airway diseases.

Evaluation of inhaled carbon monoxide as an anti-inflammatory therapy in a nonhuman primate model of lung inflammation

Carbon monoxide (CO) confers anti-inflammatory protection in rodent models of lung injury when applied at low concentration. Translation of these findings to clinical therapies for pulmonary inflammation requires validation in higher mammals. We have evaluated the efficacy of inhaled CO in reducing LPS-induced lung inflammation in cynomolgus macaques. LPS inhalation resulted in profound neutrophil influx and moderate increases in airway lymphocytes, which returned to baseline levels within 2 wk following exposure. CO exposure (500 ppm, 6 h) following LPS inhalation decreased TNF-α release in bronchoalveolar lavage fluid but did not affect IL-6 or IL-8 release. Lower concentrations of CO (250 ppm, 6 h) did not reduce pulmonary neutrophilia. Pretreatment with budesonide, a currently used inhaled corticosteroid, decreased LPS-induced expression of TNF-α, IL-6, and IL-8, and reduced LPS-induced neutrophilia by ∼84%. In comparison, CO inhalation (500 ppm, for 6 h after LPS exposure) reduced neutrophilia by ∼67%. Thus, inhaled CO was nearly as efficacious as pretreatment with an inhaled corticosteroid at reducing airway neutrophil influx in cynomolgus macaques. However, the therapeutic efficacy of CO required relatively high doses (500 ppm) that resulted in high carboxyhemoglobin (COHb) levels (>30%). Lower CO concentrations (250 ppm), associated with anti-inflammatory protection in rodents, were ineffective in cynomolgus macaques and also yielded relatively high COHb levels. These studies highlight the complexity of interspecies variation of dose-response relationships of CO to COHb levels and to the anti-inflammatory functions of CO. The findings of this study warrant further investigations for assessing the therapeutic application of CO in nonhuman primate models of tissue injury and in human diseases. The study also suggests that akin to many new therapies in human diseases, the translation of CO therapy to human disease will require additional extensive and rigorous proof-of-concept studies in humans in the future.

Endogenous carbon monoxide production in disease

Carbon monoxide (CO) in tissues and cells can originate from inhalation of CO or endogenously. Endogenous production, carboxyhemoglobin (COHb) formation, and exhaled CO levels are influenced by physiological factors, including disease. It is suggested that endogenous CO production can be used as a biomarker for oxidative and inflammatory processes. Also, endogenous CO can contribute to increased body burden of CO, which may both disrupt normal CO signaling cascades and increase the risk of CO toxicity.

Bench-to-bedside review: Carbon monoxide--from mitochondrial poisoning to therapeutic use

Carbon monoxide (CO) is generated during incomplete combustion of carbon-containing compounds and leads to acute and chronic toxicity in animals and humans depending on the concentration and exposure time. In addition to exogenous sources, CO is also produced endogenously by the activity of heme oxygenases (HOs) and the physiological significance of HO-derived CO has only recently emerged. CO exerts vasoactive, anti-proliferative, anti-oxidant, anti-inflammatory and anti-apoptotic effects and contributes substantially to the important role of the inducible isoform HO-1 as a mediator of tissue protection and host defense. Exogenous application of low doses of gaseous CO might provide a powerful tool to protect organs and tissues under various stress conditions. Experimental evidence strongly suggests a beneficial effect under pathophysiological conditions such as organ transplantation, ischemia/reperfusion, inflammation, sepsis, or shock states. The cellular and molecular mechanisms mediating CO effects are only partially characterized. So far, only a few studies in humans are available, which, however, do not support the promising results observed in experimental studies. The protective effects of exogenous CO may strongly depend on the pathological condition, the mode, time point and duration of application, the administered concentration, and on the target tissue and cell. Differences in bioavailability of endogenous CO production and exogenous CO supplementation might also provide an explanation for the lack of protective effects observed in some experimental and clinical studies. Further randomized, controlled clinical studies are needed to clarify whether exogenous application of CO may turn into a safe and effective preventive and therapeutic strategy to treat pathophysiological conditions associated with inflammatory or oxidative stress.

Carbocisteine inhibits oxidant-induced apoptosis in cultured human airway epithelial cells

BACKGROUND AND OBJECTIVE

Increased oxidant levels have been associated with exacerbations of COPD, and L-carbocisteine, a mucolytic agent, reduces the frequency of exacerbations. The mechanisms underlying the inhibitory effects of L-carbocisteine on oxidant-induced COPD exacerbations were examined in an in vitro study of human airway epithelial cells.

METHODS

In order to examine the antioxidant effects of L-carbocisteine, human tracheal epithelial cells were treated with L-carbocisteine and exposed to hydrogen peroxide (H(2)O(2)). Cell apoptosis was assessed using a cell death detection ELISA, and the pathways leading to cell apoptosis were examined by measurement of caspase-3 and caspase-9 by western blot analysis with fluorescent detection.

RESULTS

The proportion of apoptotic cells in human tracheal epithelium was increased in a concentration- and time-dependent manner, following exposure to H(2)O(2). Treatment with L-carbocisteine reduced the proportion of apoptotic cells. In contrast, H(2)O(2) did not increase the concentration of LDH in supernatants of epithelial cells. Exposure to H(2)O(2) activated caspase-3 and caspase-9, and L-carbocisteine inhibited the H(2)O(2)-induced activation of these caspases. L-carbocisteine activated Akt phosphorylation, which modulates caspase activation, and the inhibitors of Akt, LY294002 and wortmannin, significantly reversed the inhibitory effects of L-carbocisteine on H(2)O(2)-induced cell apoptosis.

CONCLUSIONS

These findings suggest that in human airway epithelium, L-carbocisteine may inhibit cell damage induced by H(2)O(2) through the activation of Akt phosphorylation. L-carbocisteine may have antioxidant effects, as well as mucolytic activity, in inflamed airways.

Effects of the menstrual cycle on lung function variables in women with asthma

RATIONALE

Angiogenesis is a defining pathologic feature of airway remodeling and contributes to asthma severity. Women experience changes in asthma control over the menstrual cycle, a time when vessels routinely form and regress under the control of angiogenic factors. One vital function modulated over the menstrual cycle in healthy women is gas transfer, and this has been related to angiogenesis and cyclic expansion of the pulmonary vascular bed.

OBJECTIVES

We hypothesized that changes in gas transfer and the pulmonary vascular bed occur in women with asthma over the menstrual cycle and are associated with worsening airflow obstruction.

METHODS

Twenty-three women, 13 with asthma and 10 healthy control subjects, were evaluated over the menstrual cycle with weekly measures of spirometry, gas transfer, nitric oxide, hemoglobin, factors affecting hemoglobin binding affinity, and proangiogenic factors.

MEASUREMENTS AND MAIN RESULTS

Airflow and lung diffusing capacity varied over the menstrual cycle with peak levels during menses that subsequently declined to nadir in early luteal phase. In contrast to healthy women, changes in lung diffusing capacity (DL(CO)) were associated with changes in membrane diffusing capacity and DL(CO) was not related to proangiogenic factors. DL(CO) did not differ between the two groups, although methemoglobin and carboxyhemoglobin were higher in women with asthma than in healthy women.

CONCLUSIONS

Women with asthma experience cyclic changes in airflow as well as gas transfer and membrane diffusing capacity supportive of a hormonal effect on lung function.

Outpatient pulmonary rehabilitation in patients with chronic obstructive pulmonary disease

Objective

To evaluate an entirely outpatient-based program of pulmonary rehabilitation in patients with chronic obstructive pulmonary disease COPD, using St.George’s Respiratory questionnaire (SGRQ), the 6-minutes walking test (6-MWT) and BODE index as the primary outcome measures.

Methods

A prospective, parallel-group controlled study of an outpatient rehabilitation program in 80 patients with COPD (67 men and 13 women; mean age 64.8 ± 10.6 years; FEV₁, 42.8% ± 7.6% of the predicted value. The active group (n = 40) took part in a 14-week rehabilitation program [3 h/wk, 1.5 h of education and exercise and 1.5 h of cycling]. The control group (n = 40) was reviewed routinely as medical outpatients. The following evaluations were carried out at study entry and after14 weeks: (1) pulmonary function studies; (2) 6-minutes walking test 6MWT; (3) quality of life; and (4) BODE index.

Results

The following patients completed the study: 35 patients (87.5%) from the active group (mean age, 63.7 ± 11.9 years; mean forced expiratory volume in one second (FEV₁), 41.9 ± 2.6% of the predicted value); and 36 patients (88%) from the control group (mean age, 65.9 ± 10.3 years; mean FEV₁, 43.33 ± 3.6% of the predicted value). We found no changes in pulmonary function parameters in the active group and the control one at 14weeks. On the other hand, there were significant changes within the components of the SGRQ (12.3 for the score total) for the patients of the active group but not for the patients of the control one (only 1.5 for the score total), we observed also a significant increase in the distance of the 6-MWT in the patients of the active group but not for the patients of the control one, and finally a decrease of two points (from 6 to 4) was noted in the score of the active group’s BODE index without any change in the control group’s one.

Conclusion

An outpatient-based of 14-week rehabilitation program significantly improved the quality of life and exercise tolerance without any change in the pulmonary function in patients with moderate COPD, and there was also a large decrease in the risk of death in rehabilitated patients as measured using the BODE index.

Exhaled carbon monoxide as a biomarker of inflammatory lung disease

Carbon monoxide (CO) can be detected on the exhaled breath of humans. Exhaled CO (E-CO) originates from the inspiration of ambient CO and from endogenous metabolic sources that include heme metabolism catalyzed by heme oxygenase (HO) enzymes. HO occurs in both constitutive (HO-2) and inducible (HO-1) forms; the latter responds to pro-inflammatory or pro-oxidative stimuli. E-CO may arise in the airways from inducible HO-1 activity in the bronchial epithelium, alveolar macrophages and other lung cell types, as a consequence of local inflammation, and from the alveolae in equilibrium with carboxyhemoglobin (Hb-CO) in the pulmonary circulation. Elevations in Hb-CO in turn may reflect increases in ambient CO, as well as increased HO activity in systemic tissues. E-CO increases dramatically in active smokers and can be used to monitor the smoking habit. Elevations in E-CO have been observed in critically ill or post-surgical patients and those with various pulmonary diseases associated with inflammation, including chronic obstructive pulmonary disease (COPD), asthma, cystic fibrosis and infections. Despite improvements in the standardization and sensitivity of methods to detect E-CO, the predictive value of this measurement as a diagnostic tool remains unclear.

Protective functions of heme oxygenase-1 and carbon monoxide in the respiratory system

The respiratory system, including the lung and upper airways, succumbs to injury and disease through acute or chronic exposures to adverse environmental agents, in particular, those that promote increased oxidative or inflammatory processes. Cigarette smoke and other forms of particulate or gaseous air pollution, allergens, microorganisms infections, and changes in inspired oxygen may contribute to lung injury. Among the intrinsic defenses of the lung, the stress protein heme oxygenase-1 constitutes an inducible defense mechanism that can protect the lung and its constituent cells against such insults. Heme oxygenases degrade heme to biliverdin-IXalpha, carbon monoxide, and iron, each with candidate roles in cytoprotection. At low concentrations, carbon monoxide can confer similar cyto and tissue-protective effects as endogenous heme oxygenase-1 expression, involving antioxidative, antiinflammatory, antiproliferative, and antiapoptotic effects. Lung protection by heme oxygenase-1 or its enzymatic reaction products has been demonstrated in vitro and in vivo in a number of pulmonary disease models, including acute lung injury, cigarette smoke-induced lung injury/chronic obstructive pulmonary disease, interstitial lung diseases, ischemia/reperfusion injury, and asthma/airway inflammation. This review summarizes recent findings on the functions of heme oxygenase-1 in the respiratory system, with an emphasis on possible roles in disease progression and therapies.

Arterial carboxyhemoglobin level and outcome in critically ill patients

OBJECTIVE

Arterial carboxyhemoglobin is elevated in patients with critical illness. It is an indicator of the endogenous production of carbon monoxide by the enzyme heme oxygenase, which modulates the response to oxidant stress. The objective was to explore the hypothesis that arterial carboxyhemoglobin level is associated with inflammation and survival in patients requiring cardiothoracic intensive care.

DESIGN

Prospective, observational study.

SETTING

A cardiothoracic intensive care unit.

PATIENTS

All patients admitted over a 15-month period.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Arterial carboxyhemoglobin, bilirubin, and standard biochemical, hematologic, and physiologic markers of inflammation were measured in 1,267 patients. Associations were sought between levels of arterial carboxyhemoglobin, markers of the inflammatory response, and clinical outcome. Intensive care unit mortality was associated with lower minimum and greater maximal carboxyhemoglobin levels (p < .0001 and p < .001, respectively). After adjustment for age, gender, illness severity, and other relevant variables, a lower minimum arterial carboxyhemoglobin was associated with an increased risk of death from all causes (odds risk of death, 0.391; 95% confidence interval, 0.190-0.807; p = .011). Arterial carboxyhemoglobin correlated with markers of the inflammatory response.

CONCLUSIONS

Both low minimum and high maximum levels of arterial carboxyhemoglobin were associated with increased intensive care mortality. Although the heme oxygenase system is protective, excessive induction may be deleterious. This suggests that there may be an optimal range for heme oxygenase-1 induction.

Carbon monoxide in sepsis

Despite modern practices in critical care medicine, sepsis or systemic inflammatory response syndrome remains a leading cause of morbidity and mortality in the intensive care unit. Thus, the need to identify new therapeutic tools for the treatment of sepsis is urgent. In this context, carbon monoxide has become a promising therapeutic molecule that can potentially prevent uncontrolled inflammation in sepsis. In humans, carbon monoxide arises endogenously from the degradation of heme by heme oxygenase enzymes. Both endogenously synthesized and exogenously applied carbon monoxide can exert antiinflammatory and antiapoptotic effects in cells and tissues. Based on these properties, carbon monoxide, when applied at low concentration, conferred protection in a variety of cellular and rodent models of sepsis, and furthermore reduced morbidity and mortality in vivo. Therefore, application of carbon monoxide may have a major impact on the future of sepsis treatment. This review summarizes evidence for salutary effects of carbon monoxide in sepsis of various organs, including lung, heart, kidney, liver, and intestine, and discusses the potential translation of the data into human clinical trials.

[Carbon monoxide--poison or potential therapeutic?]

Carbon monoxide (CO) is much more than just a toxic gas. Carbon monoxide is produced endogenously by the enzyme heme oxygenase and has important functions under physiological and pathophysiological conditions. Recent studies suggested antioxidative, anti-inflammatory, antiproliferative, anti-apoptotic, and vasodilating characteristics. Regarding clinically-relevant diseases in anesthesiology and critical care medicine, such as adult respiratory distress syndrome (ARDS), sepsis, or during organ transplantation, cytoprotective properties have been demonstrated by low-dose CO in experimental models. In view of a potential CO application in future human studies, this review discusses what is known to date about CO as it relates to functional, protective and toxic aspects.

Increased intestinal luminal carbon monoxide gas in patients with ulcerative colitis

Summary

Background

Recent studies in models of inflammatory bowel disease have demonstrated that heme oxygenase‐1 (HO‐1) induction, or its by‐products in this process such as carbon monoxide (CO), plays an important role in the intestinal inflammation. However, the distribution of HO‐1 in intestinal mucosa and the concentration of intestinal luminal CO in humans have not yet been investigated.

Aim

To detect the HO‐immunopositive cells in the intestine of normal subjects and in patients with ulcerative colitis (UC) and to measure intestinal luminal CO gas contents using gas chromatography.

Materials and Methods

The expression of HO‐1 in the intestine was determined using immunohistochemistry. Human colonic gas was collected using colonoscopy from healthy volunteers and patients with UC. Analysis of intestinal luminal gas was performed using a newly developed portable gas chromatograph.

Results

Immunopositive staining for HO‐1 was localized in the inflammatory cells, mainly mononuclear cells, and the number of cells that accepted stain was greater in patients with UC. CO level in the intestinal lumen significantly increased in patients in the active stage of UC.

Conclusion

These findings indicate that the HO‐CO system is induced in UC.

Heme oxygenase-1, a potential biomarker of chronic silicosis, attenuates silica-induced lung injury

RATIONALE

Heme oxygenase-1 (HO-1), a rate-limiting enzyme in heme catabolism, has antioxidative, antiapoptotic, and antiinflammatory activities. We examined whether HO-1 might be involved in silicosis.

OBJECTIVES

To investigate whether HO-1 can reduce silicosis in mice and humans.

METHODS AND MEASUREMENTS

Silicosis was studied using a murine model, and in 46 male patients. Serum HO-1 and 8-hydroxydeoxyguanosine (a marker of oxidative stress) were measured by enzyme-linked immunosorbent assay. Levels of HO-1 were measured by immunohistochemistry and immunoblotting.

MAIN RESULTS

Serum HO-1 levels were significantly elevated in patients with silicosis compared with age-matched control subjects or patients with chronic obstructive pulmonary disease. Serum HO-1 levels also correlated inversely with serum 8-hydroxydeoxyguanosine levels and positively with vital capacity and forced expiratory volume in one second in patients with silicosis. HO-1 was present in the lungs of humans and mice with silicosis, especially at sites of silica particle deposition. In mice, silica exposure was associated with acute leukocyte infiltration, leading to development of silicotic lung lesions. The inflammation was suppressed by treatment with hemin, an inducer of HO-1, and enhanced by zinc protoporphyrin, an inhibitor of HO-1.

CONCLUSIONS

Pulmonary HO-1 expression is increased in silicosis. HO-1 suppresses reactive oxygen species activity, and subsequent pathologic changes, thereby attenuating disease progression.

Increased intestinal luminal carbon monoxide gas in patients with ulcerative colitis

Summary

Background

Recent studies in models of inflammatory bowel disease have demonstrated that heme oxygenase‐1 (HO‐1) induction, or its by‐products in this process such as carbon monoxide (CO), plays an important role in the intestinal inflammation. However, the distribution of HO‐1 in intestinal mucosa and the concentration of intestinal luminal CO in humans have not yet been investigated.

Aim

To detect the HO‐immunopositive cells in the intestine of normal subjects and in patients with ulcerative colitis (UC) and to measure intestinal luminal CO gas contents using gas chromatography.

Materials and Methods

The expression of HO‐1 in the intestine was determined using immunohistochemistry. Human colonic gas was collected using colonoscopy from healthy volunteers and patients with UC. Analysis of intestinal luminal gas was performed using a newly developed portable gas chromatograph.

Results

Immunopositive staining for HO‐1 was localized in the inflammatory cells, mainly mononuclear cells, and the number of cells that accepted stain was greater in patients with UC. CO level in the intestinal lumen significantly increased in patients in the active stage of UC.

Conclusion

These findings indicate that the HO‐CO system is induced in UC.