End-tidal Carbon Monoxide Research Articles

End-tidal carbon monoxide concentrations measured within 48 hours of birth predict hemolytic hyperbilirubinemia.

To determine, among neonates at-risk for hyperbilirubinemia, whether measuring end-tidal carbon monoxide concentration (ETCOc) twice before 48 hours could identify those who would develop hyperbilirubinemia and differentiate hemolytic vs. non-hemolytic causes. Prospective study on neonates meeting criteria "at-risk for hyperbilirubinemia." Routine bilirubin measurements and 10-day follow-up were used to categorize neonates as; (1) normal (no hyperbilirubinemia, all bilirubins <95th percentile of Bhutani nomogram), (2) having hemolytic hyperbilirubinemia (bilirubin ≥95th percentile, DAT+, elevated retic, or G6PD+), or (3) having non-hemolytic hyperbilirubinemia. 386 neonates were enrolled. 321 (83%) did not develop hyperbilirubinemia and 65 (17%) did, of which 29 were judged hemolytic and 36 non-hemolytic. High ETCOc differentiated the hemolytic group (p < 0.001). First-day ETCOc correlated with bilirubin and with reticulocyte count (r = 0.896 and 0.878) and sensitivity and specificity for predicting hyperbilirubinemia were excellent (83% and 95%). ETCO measurement in the first 48 hours after birth predicts hemolytic hyperbilirubinemia.

Erythrokinetic mechanism(s) causing the "late anemia" of hemolytic disease of the fetus and newborn.

A transfusion-requiring "late anemia" can complicate the management of neonates convalescing from hemolytic disease of the fetus and newborn (HDFN). This anemia can occur in any neonate after HDFN but is particularly prominent in those who received intrauterine transfusions and/or double-volume exchange transfusions. Various reports describe this condition as occurring based on ongoing hemolysis, either due to passive transfer of alloantibody through breast milk or persistence of antibody not removed by exchange transfusion. However, other reports describe this condition as the result of inadequate erythrocyte production. Both hypotheses might have merit, because perhaps; (1) some cases are primarily due to continued hemolysis, (2) others are primarily hypoproductive, and (3) yet others result from a mixture of these two mechanisms. We propose prospective collaborative studies that will resolve this issue by serially quantifying end-tidal carbon monoxide. Doing this will better inform the assessment and treatment of neonates recovering from HDFN.

Carbon monoxide as a clinical marker of hemolysis.

Carbon monoxide (CO)-based tests have precisely measured hemolysis for over 40 years. End-tidal CO was the primary marker in clinical hematology research, followed by carboxyhemoglobin. Quantification of CO reflects heme oxygenases degrading heme in a 1:1 stoichiometric ratio, making CO a direct marker of hemolysis. CO in alveolar air can be quantified using gas chromatography, whose high resolution allows detecting mild and moderate levels of hemolysis. CO can be elevated in active bleeding, resorbing hematoma, and smoking. Clinical acumen and other markers remain necessary to diagnose the cause of hemolysis. CO-based tests constitute an opportunity for bench-to-bedside technology transfer.

Higher ETCOc predicts longer phototherapy treatment in neonatal hyperbilirubinemia.

This study aimed to evaluate the predictive performance of end-tidal carbon monoxide corrected to ambient carbon monoxide (ETCOc) values phototherapy in neonates with significant hyperbilirubinemia. A prospective study was conducted on neonates with significant hyperbilirubinemia who received phototherapy between 3 and 7 days of life. The breath ETCOc and serum total bilirubin of the recruited infants were measured on admission. The mean ETCOc at admission in 103 neonates with significant hyperbilirubinemia was 1.70 ppm. The neonates were categorized into two groups: phototherapy duration ≤72 h (n = 87) and >72 h (n = 16) groups. Infants who received phototherapy for >72 h had significantly higher ETCOc (2.45 vs. 1.60, P = 0.001). The cutoff value of ETCOc on admission for predicting longer phototherapy duration was 2.4 ppm, with a sensitivity of 62.5% and specificity of 88.5%, yielding a 50% positive predictive value and a 92.7% negative predictive value. ETCOc on admission can help predict the duration of phototherapy in neonates with hyperbilirubinemia, facilitate clinicians to judge disease severity, and make clinical communication easier and more efficient.

An End-Tidal Carbon Monoxide Nomogram for Term and Late-Preterm Chinese Newborns

To establish a reference nomogram for end-tidal CO corrected for ambient CO (ETCOc) levels in term and late-preterm Chinese newborns and then assess its efficacy to identify hemolytic hyperbilirubinemia. We conducted a prospective study by measuring concurrent ETCOc and total serum bilirubin (TSB) or transcutaneous bilirubin (TcB) levels collected postnatally at 12, 24, 48, 72, 96, and 120hours of age. ETCOc at the 25th, 50th, 75th, and 95th percentiles at each epoch were used to construct the reference nomogram. We then explored the ability of predischarge ETCOc and TSB/TcB metrics to predict the development of hyperbilirubinemia requiring phototherapy in early postnatal period and jaundice readmission in late postnatal period. Our nomogram, based on 990 measurements from 455 infants who were not nonhemolytic, displayed a steady line within 3 postnatal days, followed by a subsequent decline. From a cohort of infants with a serial ETCOc measurements (n=130) and those readmitted (n=21), we found that ETCOc and TSB/TcB ≥75th percentile can identify most hemolytic hyperbilirubinemia between 12 and 72hours after birth with an area under the curve (AUC) of 0.741. An ETCOc ≥1.7ppm alone between 96 and 120hours after birth can identify most hemolytic hyperbilirubinemia with an AUC of 0.816. In addition, 90.5% of readmitted infants had an ETCOc ≥75th percentile. An ETCOc reference nomogram during the first 5 postnatal days in nonhemolytic term and late-preterm newborns can be used to identify hemolytic hyperbilirubinemia requiring phototherapy in the early postnatal period and readmission in the late postnatal period.

Breath Carbon Monoxide Levels in Different Forms of Smoking

Bidi, cigarette, hookah and chillum are common modes of tobacco smoking in India. Many people consider hookah and chillum smoking less toxic because smoke is filtered through water or wet cloth. We evaluated the toxicity of tobacco smoking by measuring end-tidal carbon monoxide (eCO) levels after various modes of smoking. Eighteen healthy smokers who smoked bidi, cigarette, hookah and chillum on six days were studied. They smoked one bidi, one cigarette, five minutes hookah, one serve (15 minutes) hookah, five minutes chillum and one serve (15 minutes) chillum on six days randomly. The eCO values were measured before initiation of smoking and for a period of one hour after the smoking session. Increase in eCO values in comparison to baseline after different modes of smoking was compared. In comparison to baseline, mean eCO levels were raised by 4.94 (0.96) parts per million (ppm) immediately and 4.17 (1.07) ppm 60 minutes after cigarette smoking. Bidi smoking caused slightly less increase in mean eCO levels (3.17 [0.82]). One serve of hookah and chillum smoking caused elevation of mean eCO values by almost eight-folds higher than that of cigarette smoking. Five minutes of smoking with hookah (22.18 [5.29]) and one serve of hookah (33.0 [8.76]) and chillum (40.14 [12.73]) caused significantly higher values of mean increase in eCO in comparison to cigarette smoking (p<0.001). With regard to eCO levels, hookah and chillum smoking are much more toxic than cigarette smoking.

Reference intervals for end-tidal carbon monoxide of preterm neonates.

We constructed reference intervals for end-tidal carbon monoxide (ETCOc) levels of neonates 28 0/7 to 34 6/7 weeks gestation in order to assess hemolytic rate. This is a prospective four-NICU study in Bangkok, Thailand, and Utah, USA. Of 226 attempted measurements, 92% were successful. Values from day 1 through 28 were charted and upper (>95th percentile) reference interval limits calculated. During the entire 28 days, the ETCOc upper reference intervals from babies in Bangkok were higher than those in Utah (p < 0.01). No differences were found due to sex, or earliest vs. latest gestation at birth (both p > 0.1). Similar to term neonates, preterm neonates in Bangkok and Utah had higher ETCOc values during the first 48 h after birth than thereafter (p < 0.01). Using this methodology, and the reference interval chart, the hemolytic rate of preterm infants ≥28 weeks can be assessed.

Improvement Initiative: End-Tidal Carbon Monoxide Measurement in Newborns Receiving Phototherapy

To determine, as part of our Utah Newborn Nursery Bilirubin Management Program, whether end-tidal carbon monoxide concentration (ETCOc) measurements in all newborns in our nursery receiving phototherapy were associated with outcomes related to the management of hyperbilirubinemia, including time (hours after birth) when phototherapy was initiated, total duration of phototherapy during the nursery stay, repeat phototherapy treatments, and hospital readmission for phototherapy. We performed a planned interim analysis of a component of our program in which we measured ETCOc noninvasively using CoSense on each newborn in our nursery receiving phototherapy and recorded specific outcomes related to phototherapy management. Of 1856 newborns admitted to our nursery in a 6-month period in 2020, 170 (9.8%) were treated with phototherapy. An ETCOc reading was successfully obtained in 145 of 151 attempts (96%). Higher ETCOc values were associated with earlier institution of phototherapy and longer duration of phototherapy. For every 1-ppm increase in ETCOc, phototherapy was started 9hours earlier (95% CI, 3.3-14.8; P=.002) and was administered for an additional 9.3hours (95% CI, 4.1-14.6; P<.001). Three newborns were readmitted to the hospital for intensive phototherapy; while in the nursery, all 3 had an elevated ETCOc (2.2, 2.6, and 2.9ppm). Our findings provide answers to questions raised in the 2004 American Academy of Pediatrics bilirubin guidelines. In our neonatal nursery, measuring ETCOc in all phototherapy recipients was feasible and safe, and the results were associated with multiple aspects of phototherapy management. Higher ETCOc values predicted earlier and longer phototherapy courses.

Neonatal hyperbilirubinemia management: Clinical assessment of bilirubin production

The predominant cause of elevated total/plasma bilirubin (TB) levels is from an increase in bilirubin production primarily because of ongoing hemolysis. If undiagnosed or untreated, the risk for developing extreme neonatal hyperbilirubinemia and possibly bilirubin-induced neurological dysfunction (BIND) is increased. Since carbon monoxide (CO) and bilirubin are produced in equimolar amounts during the heme catabolic process, measurements of end-tidal CO levels, corrected for ambient CO (ETCOc) can be used as a direct indicator of ongoing hemolysis. A newly developed point-of-care ETCOc device has been shown to be a useful for identifying hemolysis-associated hyperbilirubinemia in newborns. This review summarizes the biology of bilirubin production, the clinical utility of a novel device to identify neonates undergoing hemolysis, and a brief introduction on the use of ETCOc measurements in a cohort of neonates in China.

Noninvasive Detection of Hemolysis with ETCOc Measurement in Neonates at Risk for Significant Hyperbilirubinemia

Background: Hemolytic hyperbilirubinemia due to blood group incompatibility or glucose-6-phosphate dehydrogenase deficiency (G6PD) is a common cause of significant hyperbilirubinemia. Hemolysis in a hyperbilirubinemic infant increases the risk of bilirubin neurotoxicity. A new portable device (CoSense) can rapidly detect breath end-tidal carbon monoxide corrected to ambient carbon monoxide (ETCOc). ETCOc levels are surrogate markers of hemoglobin breakdown and bilirubin production. Objective: The aim was to evaluate the association between ETCOc values and hemolysis and its relevance in neonates at risk for significant hyperbilirubinemia. Methods: A prospective study was conducted among newborn infants born at more than 35 weeks and with a birth weight greater than 2,000 g with a G6PD deficiency, blood group incompatibility, or clinical jaundice needing phototherapy during the first 7 days of life. The recruited infants had their breath ETCOc measured twice, first on the day of recruitment and then again on the following day. Results: Fifty infants completed this study. Their mean ETCOc was 1.61 (±0.56) ppm. There was a linear correlation (r = 0.89) between increasing ETCOc values and reticulocyte counts (RC). Sixteen newborns with ABO incompatibility had a significantly higher mean ETCOc of 1.98 ppm (±0.71) as compared to 1.43 (±0.38) ppm in the nonhemolytic hyperbilirubinemia (NHH) group (n = 25) (p = 0.002). This was suggestive of hemolysis as shown by the significantly higher RC of 6.90% (±3.38) compared to 4.68 (±1.26) in the NHH group (p <0.005). Neonates with an ETCOc level ≥1.8 ppm had a higher RC, a lower hemoglobin level, higher serum bilirubin levels, and a rapid rise in serum bilirubin and needed a longer duration of phototherapy. ETCOc values ≥1.8 ppm were suggestive of hemolysis (RC ≥6%), with a sensitivity of 90% and a specificity of 83%. Conclusion: Higher ETCOc values ≥1.8 ppm are suggestive of hemolysis and they are associated with significant hyperbilirubinemia.

Comparison of End Tidal Carbon Monoxide Levels between Conventional Cigarette, Electronic Cigarette and Heated Tobacco Product among Asiatic Smokers

Background Electronic nicotine delivery systems (ENDS) and heated tobacco products (HTPs) are noncombustible tobacco products which have been found to generate aerosols containing lower levels of Harmful and Potentially Harmful Constituents (HPHCs) in comparison to conventional cigarettes. Objective: This quasi experimental study measured and compared the end tidal carbon monoxide (eCO) levels of participants after use of ENDS, HTPs and conventional cigarettes. Methods: In total 45 smokers, each smoking at least 10 conventional cigarettes per day for 5 years participated in the study. Based on their preference, participants used only one of the tobacco products (ENDS, HTPs, or conventional cigarette) and were briefed about the product use based on manufacturer’s instructions. The eCO levels were obtained at baseline, followed by 5, 10, 15, 30 and 45 min respectively after the product use. Results: There was significant increase in eCO levels for conventional cigarettes as compared to other modes. Peak eCO levels of 20.2 ± 0.86 ppm, 8.8 ± 1.56 ppm and 6.0 ± 1.36 ppm was achieved at 30 min, 15 min and 10 min for conventional cigarettes, ENDS and HTPs respectively. However, the levels were significantly lower in ENDS and HTPs. Conclusion: Even though ENDS and HTPs may have produced significantly lower eCO than conventional cigarettes, the significantly increasing levels over time from baseline which was not shown before is a cause of concern. As of now, their use as an alternate to cigarettes needs to be considered under regulatory framework.

Endtidal carbonmonoxide and carboxyhemoglobin for prediction of significant hyperbilirubinemia in healthy Indian neonates &gt;35 weeks of gestation

Background: Endtidalcarbonmonoxide (ETCOc) and Carboxyhemoglobin (COHB) levels correlate well to bilirubin production and an availability of non-invasive point of care (POC) device in predicting significant hyperbilirubinemia is of great advantage when compared to measurement of serum bilirubin. Objective of the study is to measure a value of ETCOc and COHB in the early neonatal period for the prediction of significant hyperbilirubinemia.Methods: This was the descriptive Cross Sectional Study. ETCOc and COHB were measured 12th hourly for 72 hours followed by TSB in whom the TCB was &gt;14mg/dl. Neonates were classified as jaundiced whose TSB values were in phototherapy range as per AAP Recommendations. Receiver Operative Curves (ROC) were created by appropriate statistical software for ETCOc and COHb to predict significant hyperbilirubinemia. The Sensitivity, Specificity, Positive predictive value, Negative predictive value and likelihood ratios of each was determined and the correlation between ETCOc and COHb levels, ETCOc and TCB, COHB and TCB at different hours of age was evaluated.Results: Among the total 320 infants, 156 of them developed significant hyperbilirubinemia. The ETCOc and COHB level at 60 hours of age was the most predictive of significant hyperbilirubinemia by ROC analysis. ETCOc cut-off of 1.65 ppm at 60 hours of age has a sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio and negative likelihood ratio of 84.6%, 80.5%, 80.5% and 84.6%, 4.33 and 0.19. COHB cut-off of 1.32 ppm at 60 hours of age has a sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio and negative likelihood ratio of 84.6%, 81%, 80% and 84.2%, 4.34 and 0.19.ETCOc had a maximum correlation with COHB at 48 hours of age.Conclusions: An increased level of Endtidalcarbonmonoxide and Carboxyhemoglobin in the early neonatal period is useful as a screening test for prediction of significant hyperbilirubinemia.

Comparison of end-tidal carbon monoxide measurements with direct antiglobulin tests in the management of neonatal hyperbilirubinemia.

Determine whether management of neonatal hyperbilirubinemia differs if one used end-tidal carbon monoxide (CO) corrected for ambient CO (ETCOc) measurements instead of direct antiglobulin test (DAT) results to assess the severity of hemolysis. Retrospective chart review of infants with total bilirubin and ETCOc levels measured from July 2016 to August 2018. The reported treatment is the hypothetical management infants might have received had there been strict adherence to American Academy of Pediatrics guidelines, rather than the actual management they received. Only 27.2% of 191 DAT(+) infants were hemolyzing based on ETCOc, while 29.1% of DAT (-) infants were hemolyzing based on ETCOc. Management of 18 (9.4%) infants differed depending if ETCOc or DAT were used to determine hemolysis. Eight fewer infants would have received phototherapy if ETCOc was used. ETCOc is a more accurate determinant of hemolysis in the newborn, and its use can lead to less phototherapy.

Normal Hemoglobin Concentrations in Obstructive Sleep Apnea and Associated Neocytolysis-Mediated Hemolysis and Inflammation Mediated Suppression of Expected Elevated Hemoglobin

Obstructive sleep apnea (OSA) is characterized by chronic intermittent hypoxia (CIH) caused by recurrent episodes of upper airway obstruction during sleep. Chronic hypoxia increases red blood cell volume (RBCV) and hemoglobin concentration (Hb) in order to improve tissue oxygen delivery. However, the prevalence of increased Hb in OSA was only 1.7% (9 out of 527 patients) in our prior study (Gangaraju et al Blood 2016 128:2444). The reasons for this relative lack of discernable erythrocytosis is not yet fully understood. Further, the studies of possible changes in RBC and plasma volume in OSA are lacking. We collected blood samples from OSA patients before and after 3 months of continuous positive airway pressure (CPAP) treatment. We estimated erythropoietic activity by measuring erythropoietin (EPO) and reticulocyte count. EPO levels and reticulocytes were higher in OSA patients compared to controls; CPAP treatment normalized these levels. Time spent below sPO2 89% correlated with EPO levels (r=0.3434 and p=0.0403) indicating that episodes of hypoxia augmented erythropoiesis. However, Hb remained normal, leading us to hypothesize that augmented erythropoietic stimulus in OSA is counterbalanced by either 1) increase of hemolysis or 2) erythropoietic resistance to EPO. Hemolysis was detected in some but not all OSA patients by end-tidal carbon monoxide (ETCO), a product of heme catabolism; however, the instrument's limited sensitivity precluded detection of mild hemolysis. We previously showed that hypoxia-increased RBCV is transiently overcorrected upon rapid return to normoxia by preferential destruction of young red cells -neocytolysis. Neocytolysis is caused by excessive accumulation of reactive oxygen species (ROS) from increased retention of mitochondria in reticulocytes and decreased catalase in young RBCs (1). In our OSA subjects, we found that mitochondrial mass and mitochondrial ROS were higher in reticulocytes. Further, ROS were higher in B- cells, T-cells, monocytes, and granulocytes compared to controls. After CPAP treatment, these values normalized and catalase mRNA and enzyme activity also increased. These results support neocytolysis as one of the factors that prevent the increase of Hb in OSA. OSA also induces inflammation, a factor known to inhibit erythropoiesis, in part by induction of hepcidin which inhibits release of iron from macrophages. IL-6 and TNF transcript levels in granulocytes were higher in OSA compared to controls and normalized after CPAP treatment. Hepcidin levels were higher in OSA compared to controls. Hepcidin levels were correlated with inflammatory markers, IL-6 levels were inversely correlated with EPO levels, and iron and transferrin saturation levels were lower in OSA, inversely correlating with elevated hepcidin. The normal Hb does not rule out the presence of polycythemia, as increased RBCV could be offset by concomitant increase in plasma volume resulting in a normal Hb concentration. This was recently demonstrated in Tibetan Sherpas living in hypoxic high altitude who have normal Hb but increased RBCV and plasma volume (PV) (2). One can determine RBCV and PV by inhaling known amount of CO and measuring increments of carboxyhemoglobin together with Hb and hematocrit. We recently obtained the required instrumentation (OpCO, DETALO INSTRUMENTS, Denmark), and are currently correlating our clinical and biochemical measurement with OSA subjects' RBCV and PV to either confirm presence of hypoxia-induced polycythemia or conclusively rule it out. We conclude that the absence of elevated Hb in OSA is attributable not only to neocytolysis but also to the suppression of erythropoiesis by inflammation. 1) Song J, Yoon D, Christensen RD., Horvathova M,Thiagarajan P, and Prchal JT. HIF mediated increased ROS from reduced mitophagy and decreased catalase causes neocytolysis. J Mol. Med., (Berl). 2015 Aug., PMID: 26017143. 2) Stembridge M et all. The overlooked significance of plasma volume for successful adaptation to high altitude in Sherpa and Andean natives. Proc Natl Acad Sci U S A.2019 Jul 29. [Epub ahead of print]. Disclosures Lundby: Detalo: Other: CEO and founder. Ganz:Intrinsic LifeSciences: Consultancy, Equity Ownership.

Inhaled carbon monoxide increases vasodilation in the microvascular circulation

Preeclampsia (PE) is characterized by systemic maternal endothelial dysfunction. Changes in endothelial reactivity have been reported before the onset of clinical signs of PE, and continuing into the post-partum period. Women who smoke during pregnancy have a 33% reduced risk of developing PE. This reduced risk is hypothesized to be, in part, attributed to carbon monoxide (CO), a by-product of cigarette combustion and a known endogenous vasodilator. Determining the vascular effects of CO in healthy women, may inform how CO can improve endothelial function and have promise as a novel therapeutic for PE. As part of a pilot study to determine the vascular effects of CO, the aim of this study was to measure microvascular vasodilation following low-dose CO inhalation. Non-pregnant women inhaled ambient room air or 250 ppm CO for 24 min during microvascular assessment using laser speckle contrast imaging. Changes in vascular flux were measured in the forearm before, during, and following a three-minute arterial occlusion. CO inhalation increased end-tidal breath CO (EtCO) (9.1 ± 1.9 vs. 1.8 ± 0.7 ppm, p < 0.05) and increased microvascular vasodilation, measured as difference of maximum level/resting level ratio (mean difference 0.476, 95% confidence interval (CI) = 0.149–0.802 vs. 0.118, 95% CI = −0.425–0.662, p < 0.05). Women who inhaled CO had a longer time to half recovery of endothelial function following arterial occlusion, compared to controls (hazard ratio 0.29, 95% CI = 0.10–0.91, p = 0.033). Inhalation of CO moderately increased EtCO and resulted in an increased microvascular response, suggesting that CO may have potential as a therapeutic for PE.

Pathophysiology of Obstructive Sleep Apnea (OSA) - Blood Cells' Reactive Oxygen Species and Inflammation Prevent Polycythemia

Obstructive sleep apnea (OSA), characterized by intermittent hypoxia, causes cardiovascular, metabolic, neurocognitive and cancer complications. Hypoxia expands the red cell mass by stimulating erythropoietin (EPO) production; yet in our analysis of 527 OSA patients, <1% had OSA-related polycythemia (Gangaraju et al Blood 2016 128:2444). Typical hypoxia-induced red blood cells (RBCs) mass normalized upon return to normoxia by neocytolysis i.e. preferential destruction of young hypoxia-born RBCs. In an animal model, we demonstrated that neocytolysis is caused by excessive generation of reactive oxygen species (ROS) from increase of mitochondrial retention and accumulation of ROS. ROS increase resulted from decreased antioxidant enzyme catalase mediated by hypoxia-induced miR-21. We hypothesized that polycythemia in OSA was prevented by neocytolysis.It is also well-known that OSA induces systemic inflammation markers including C-reactive protein, IL-6, TNF-α, IL-8, and NF-κb. Inflammation participates in the control of the number of RBCs by inducing hepcidin, the principal regulator of iron metabolism. Increased hepcidin suppresses erythropoiesis by inhibiting iron release from macrophages. Based on this evidence, we also hypothesized that the absence of polycythemia in OSA might be caused by an independent contribution of inflammation-mediated suppression of erythropoiesis.We studied OSA patients before and after treatment with continuous positive airway pressure (CPAP). Increased erythropoiesis was evidenced by increased EPO and reticulocytosis. EPO levels correlated with time spent below sPO2 89 %, indicating that severe OSA patients had more augmented erythropoiesis. However, hematocrit levels were normal. Hemolysis was detected in some but not all OSA patients by end tidal carbon monoxide (a product from heme catabolism). After CPAP treatment, these changes diminished but hematocrits did not change. Conditions favoring neocytolysis were confirmed by increased ROS from expanded reticulocytes' mitochondria which correlated with time spent below sPO2 89 %. Downregulated catalase resulting from increased miR-21 was also detected. Also these changes normalized with CPAP. These results indicate that hemolysis of hypoxia-born RBCs prevents OSA patients from becoming polycythemic. Increased ROS was not only found in reticulocytes but also in leukocytes; these also normalized with CPAP.Expression of inflammatory markers (NFKB1, TNF, and IL6) in granulocytes was higher in OSA compared to controls and normalized by CPAP; these levels correlated with apnea-hypopnea Index (AHI). OSA patients had higher hepcidin levels, correlating with inflammatory marker levels and inversely correlated with EPO. Iron and transferrin saturation levels were lower in OSA compared to controls, inversely correlating with high hepcidin levels. These data indicated that besides neocytolysis, coexistent suppression of erythropoiesis by inflammation contributed to the lack of polycythemia in OSA.In OSA, inflammation mediated increase of ROS in leukocytes is a known causative factor of cardiovascular disease. We now report increase of both ROS and inflammatory markers in leukocytes.We conclude that the absence of polycythemia in OSA is the result of hemolysis via neocytolysis and inflammation-mediated suppression of erythropoiesis. Increased ROS in blood cells and systemic inflammation from OSA-constitute mechanisms likely contributing to the pathophysiology of OSA. DisclosuresGanz:Vifor: Consultancy; Ablynx: Consultancy; Keryx Pharma: Consultancy, Research Funding; Silarus Pharma: Consultancy, Equity Ownership; La Jolla Pharma: Consultancy, Patents & Royalties: Patent licensed to La Jolla Pharma by UCLA; Akebia: Consultancy, Research Funding; Intrinsic LifeScience: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy.

Research progresses of end-tidal carbon monoxide in neonatal hemolytic disease

The end-tidal carbon monoxide concentration reflects the level of endogenous carbon monoxide, which can be used as an index of blood bilirubin and hemolysis.Most studies have confirmed that ETCO contributes to identification of neonatal hemolytic disease early and reducing the risk of development into serious hyperbilirubinemia.This paper mainly reviews the diagnostic value of ETCO in neonatal hemolytic disease. Key words: End-tidal carbon monoxide; Neonate; Hemolysis; Hyperbilirubinemia

Identification of risk for neonatal haemolysis.

To identify neonates at risk of haemolytic hyperbilirubinaemia through near-concurrent measurements of total serum/plasma bilirubin (TB) or transcutaneous bilirubin (TcB) and end-tidal breath carbon monoxide (CO), corrected for ambient CO (ETCOc), an index of bilirubin production and haemolysis. Paired TB/TcB (mg/dL) and ETCOc (ppm) measurements were obtained in newborns (n = 283) at 20 to <60 hours of age in five nurseries. TB/TcB values were assigned TB/TcB percentile risk values using the Bhutani hour-specific nomogram. In infants having two serial TB/TcB measurements (n = 76), TB rate of rise (ROR, mg/dL/h) was calculated. For the entire cohort (n = 283), 67.1% and 32.9% had TB/TcB<75th and ≥75th percentile, respectively. TB/TcB (5.79 ± 1.84 vs 9.14 ± 2.25 mg/dL) and ETCOc (1.61 ± 0.45 vs 2.02 ± 1.35 ppm, p = 0.0002) were different between the groups. About 36.6% of infants with TB/TcB ≥75th percentile had ETCOc ≥ 2.0 ppm. In the subcohort of infants with serial TB/TcB measurements (n = 76), 44.7% and 55.3% had TB/TcB<75th and ≥75th percentile, respectively. TB/TcB (5.28 ± 1.97 vs 9.53 ± 2.78 mg/dL), ETCOc (1.72 ± 0.48 vs 2.38 ± 1.89 ppm, p = 0.05) and TB ROR (0.011 ± 0.440 vs 0.172 ± 0.471 mg/dL/h) were different between the groups. The combined use of TB/TcB percentile risk assessments and ETCOc measurements can identify infants with haemolytic hyperbilirubinaemia. The addition of TB ROR can identify those infants with elimination disorders.

Erythrocyte aging as a mechanism of anemia and a biomarker of device thrombosis in continuous-flow left ventricular assist devices

Blood trauma caused by continuous-flow left ventricular assist devices (CF-LVADs) has been associated with device thrombosis and anemia. Accurate in vivo quantification of erythrocyte turnover and its contribution to CF-LVAD complications have yet to be elucidated. We investigated the age (lifespan) of circulating erythrocytes in subjects with CF-LVAD. Erythrocyte lifespan is a quantitative indicator of in vivo erythrocyte turnover that can be accurately derived from measurement of the exhaled carbon monoxide (CO) level. Sixty non-smoking subjects were prospectively enrolled: 25 had a CF-LVAD without thrombosis; 10 had a CF-LVAD with thrombosis; and 25 were normal controls. End-tidal breath CO levels were measured and used to calculate erythrocyte lifespan. The mean erythrocyte lifespan was significantly shorter in CF-LVAD subjects with (29.7 ± 14.9 days) compared to those without (65.0 ± 17.3 days) device thrombosis (p < 0.0001). The lifespans in these 2 groups were significantly shorter compared with normal controls (96.0 ± 24.9 days, both p < 0.0001). A receiver operator curve demonstrated high sensitivity-specificity for use of erythrocyte lifespan to detect device thrombosis (AUC = 0.94). In addition, all CF-LVAD subjects had low hemoglobin (11.8 ± 2.0 g/dl), and their anemia was normochromic normocytic with elevated mean reticulocyte counts. Erythrocyte lifespan correlated significantly with mean corpuscular hemoglobin concentration (r = 0.56, p = 0.0005) and red cell distribution width (r = -0.65, p < 0.001), but not with reticulocyte count (r = 0.27, p = 0.32). Erythrocyte lifespan is substantially reduced in subjects with a CF-LVAD, which was more pronounced in the presence of device thrombosis. The etiology of anemia in CF-LVAD was primarily due to accelerated erythrocyte aging. Further studies are needed to determine whether erythrocyte lifespan could provide a practical means of detecting subtle pre-clinical thrombosis.

Measuring End-Tidal Carbon Monoxide of Jaundiced Neonates in the Birth Hospital to Identify Those with Hemolysis

Background: End-tidal breath carbon monoxide (ETCOc) levels correlate with catabolism of heme, but until recently, this measurement was not readily available for application to neonatology practice. Objectives: We performed a prospective, multihospital, test-of-concept study where ETCOc was measured during the birth hospitalization of neonates with a total bilirubin (TB) value >75th percentile on the Bhutani bilirubin nomogram. This was done to test the feasibility and ease of use of this new device. Methods: Neonates with an elevated ETCOc (with a >95th percentile reference interval previously established) were labeled as having ‘hemolytic jaundice'. We recommended a follow-up TB check <24 h after hospital discharge to these families. Results: One hundred and fifteen neonates were eligible for the study, the parents of 103 provided consent, and measurements were obtained for 100. Sixty-three had normal and 37 had elevated ETCOc values. By means of a direct antiglobulin test (DAT; Coombs), 11 of these 37 were found positive for ABO hemolytic disease; the remaining 26 had other etiologies. Thirty-six of the 37 with an elevated ETCOc had repeat TB monitoring <24 h after discharge home. None of the 100 were rehospitalized for jaundice treatment compared with a rate of 2.99 rehospitalizations per 100 control neonates who had a TB value >75th percentile (p = 0.079). Conclusion: ETCOc measurement is a feasible means of assessing hemolysis in jaundiced neonates during the birth hospitalization. When hemolysis is identified, parents are likely to comply with instructions to bring the infant for a TB checkup <24 h after discharge home.