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We aimed to investigate whether changes in prefrontal cortex (PFC) oxyhemoglobin (O 2 Hb) and deoxyhemoglobin (HHb) associates with inspiratory muscle effort during inspiratory threshold loading (ITL) in healthy participants. Participants performed an incremental ITL. Breathing pattern, partial pressure of end-tidal CO 2 (P ET CO 2 ), mouth pressure and O 2 Hb and HHb over the right dorsolateral PFC, sternocleidomastoid (SCM), and diaphragm/intercostals (Dia/IC) were monitored. Fourteen healthy participants (8 men; 29 ± 5 years) completed testing. Dyspnea was higher post- than pre-ITL (5 ± 1 vs. 0 ± 1, respectively; P<0.05). PFC O 2 Hb increased (P < 0.001) and HHb decreased (P = 0.001) at low loads but remained stable with increasing ITL intensities. PFC total hemoglobin increased at task failure compared to rest. SCM HHb increased throughout increasing intensities. SCM and Dia/IC total hemoglobin increased in the at task failure compared to rest. P ET CO 2 did not change (P = 0.528). PFC is activated early during the ITL but does not show central fatigue at task failure despite greater dyspnea and an imbalance of SCM oxygen demand and delivery., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Background: During acute bronchial obstruction, despite a higher work of breathing, blood supply and oxygen availability may be reduced in intercostal muscles because of mechanical constraints. This hypothesis was assessed in healthy subjects breathing with and without expiratory load (ETL)., Methods: Eleven men (24 ± 2 years) breathed at rest for 5 min in unloaded condition and for 20 min through a 20-cmH 2 O ETL. Tissue saturation index (TSI) and changes (Δ) in concentration of total and oxy-haemoglobin ([tHb] and [O 2 Hb]) were measured in the seventh intercostal space by near-infrared spectroscopy., Results: [tHb] and [O 2 Hb] decreased with ETL (-5.16 μM and -3.54 μM; p < 0.05). TSI did not vary. Negative correlations were observed between Δ[O 2 Hb] and changes in expiratory flow rate (ΔVt/Te) and between ΔTSI and Δ V˙E (r = -0.78 and -0.74; p ≤ 0.01)., Conclusion: Despite decreases in Hb concentrations, saturation in oxygen was not reduced with ETL in intercostal muscles, suggesting a satisfactory ventilatory and/or hemodynamic arrangement., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Procalcitonin (PCT) concentrations increase during bacterial infections and could improve diagnosis of pneumonia and risk stratification in patients with acute dyspnea., Methods: PCT concentrations were measured <24 h of admission in 310 patients with acute dyspnea and compared to C-reactive protein (CRP) and white blood cells (WBC) in the total cohort and the subset of patients with concomitant acute heart failure (HF)., Results: We diagnosed pneumonia in 16 out of 140 patients with acute HF (11%) and in 45 out of 170 patients with non-HF-related dyspnea (27%). PCT concentrations were higher in patients with pneumonia vs. patients without pneumonia, both among acute HF patients (median 2.79 [Q1-3 0.18-5.80] vs. 0.10 [0.07-0.14] ng/mL, p < .001) and non-HF patients (0.22 [Q1-3 0.13-0.77] vs. 0.07 [0.05-0.10] ng/mL, p < .001). CRP and WBC were also higher in patients with pneumonia in both groups, but among acute HF patients, only PCT concentrations were associated with pneumonia in multivariate analysis. In patients with acute HF, receiver-operating statistics area under the curve (ROC-AUC) to diagnose pneumonia was 0.90 (95% CI 0.81-0.98) for PCT, 0.84 (0.73-0.94) for CRP, and 0.72 (0.57-0.87) for WBC. The corresponding ROC-AUCs among patients with non-HF-related dyspnea were 0.88 (0.82-0.93), 0.94 (0.90-0.98), and 0.79 (0.72-0.87), respectively. During a median follow-up of 823 days (Q1-3 471-998) 114 patients died, and PCT and CRP, but not WBC concentrations were associated with all-cause mortality., Conclusion: In acute HF patients, PCT concentrations were superior to CRP and WBC to diagnose concurrent pneumonia., (Copyright © 2018 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background: Circulating fibroblast growth factor 23 (FGF23) concentrations have been linked to left ventricular remodeling and unfavorable cardiovascular outcomes, but whether FGF23 is associated with heart failure (HF) diagnosis and outcome in unselected patients with dyspnea is unknown. Accordingly, we assessed the diagnostic and prognostic properties of FGF23 in patients presenting to the emergency department with acute dyspnea., Methods and Results: FGF23 was measured in 314 patients admitted with acute dyspnea and the diagnostic and prognostic merit was compared to that of N-terminal pro-B-type natriuretic peptide (NT-proBNP). The diagnosis of acute HF was adjudicated by two independent physicians. Circulating FGF23 concentrations on hospital admission were higher in patients with acute HF vs. patients with non-HF related dyspnea: median 3.60 (IQR 1.24-8.77) vs. 1.00 (0.43-2.20) pmol/L; P<0.001. The receiver-operating statistics area under the curve for acute HF diagnosis was 0.750 (0.699-0.797) for FGF23 and 0.853 (0.809-0.890) for NT-proBNP. Adjusting for clinical risk indices and cardiac biomarkers in multivariate Cox regression analysis, admission FGF23 concentrations were associated with mortality in the total study population (hazard ratio [HR] per 1 SD in ln FGF23 1.74 [1.40-2.16]). FGF23 also reclassified patients into their correct risk strata on top of clinical variables significantly associated with outcomes in the total cohort (net reclassification index 0.386 [0.161-0.612]). In patients with acute HF, both admission FGF23 and NT-proBNP concentrations were associated with mortality., Conclusion: Circulating FGF23 concentrations provide incremental prognostic information to established risk indices in patients with acute dyspnea, but do not improve diagnostic accuracy over NT-proBNP measurements., (Copyright © 2017 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background: Few studies have investigated the short-term respiratory effects of ambient air pollution in chronic obstructive pulmonary disease (COPD) patients in the context of high pollution levels in Asian cities., Methods: A panel of 23 stable COPD patients was repeatedly measured for biomarkers of airway inflammation including exhaled nitric oxide (FeNO) and exhaled hydrogen sulfide (FeH2S) (215 measurements) and recorded for daily respiratory symptoms (794person-days) in two study periods in Beijing, China in January-September 2014. Daily ambient air pollution data were obtained from nearby central air-monitoring stations. Mixed-effects models were used to estimate the associations between exposures and health measurements with adjustment for potential confounders including temperature and relative humidity., Results: Increasing levels of air pollutants were associated with significant increases in both FeNO and FeH2S. Interquartile range (IQR) increases in PM2.5 (76.5μg/m(3), 5-day), PM10 (75.0μg/m(3), 5-day) and SO2 (45.7μg/m(3), 6-day) were associated with maximum increases in FeNO of 13.6% (95% CI: 4.8%, 23.2%), 9.2% (95% CI: 2.1%, 16.8%) and 34.2% (95% CI: 17.3%, 53.4%), respectively; and the same IQR increases in PM2.5 (6-day), PM10 (6-day) and SO2 (7-day) were associated with maximum increases in FeH2S of 11.4% (95% CI: 4.6%, 18.6%), 7.8% (95% CI: 2.3%, 13.7%) and 18.1% (95% CI: 5.5%, 32.2%), respectively. Increasing levels of air pollutants were also associated with increased odds ratios of sore throat, cough, sputum, wheeze and dyspnea., Conclusions: FeH2S may serve as a novel biomarker to detect adverse respiratory effects of air pollution. Our results provide potential important public health implications that ambient air pollution may pose risk to respiratory health in the context of high pollution levels in densely-populated cities in the developing world., (Copyright © 2016 Elsevier Ltd. All rights reserved.)