title: C-reactive protein correlates with tissue oxygen availability in patients with stable COPD.
abstract: BACKGROUND
  Arterial oxygen tension, oxygen delivery to tissue, and systemic inflammation are recognized as pivotal factors in the progression of chronic obstructive pulmonary disease (COPD). However, interconnections between systemic inflammation and tissue oxygen availability are scantly investigated. Tissue oxygen availability depends on arterial PaO2, oxygen concentration, hemoglobin oxygen affinity (P50), and hemoglobin oxygen binding capacity (ceHb). As the integrated changes of those indices are summarized by oxygen extraction tension (PaO2x), the objective of this study was to explore the association between C-reactive protein (CRP) blood levels and either PaO2x or each of its determinants, in stable COPD.
  
  
  METHODS
  Blood CRP and oxygen status of arterial blood were measured at rest while breathing room air in 44 moderate to severe stable COPD patients. PaO2x was calculated along the shape of oxygen binding curve as the oxygen tension resulting from removal of 2.3 mmol of oxygen per liter of blood. Multiple linear regression analysis was performed with PaO2, ceHb, and P50 as independent variables, and CRP as the dependent variable, adjusting for age and sex. The analysis was repeated using PaO2x as a sole independent variable.
  
  
  RESULTS
  Multiple linear regression analysis indicated that ceHb, PaO2, and P50, were significant and independent predictors of CRP (R2 = 0.52, p < 0.0001). PaO2x alone was an even stronger predictor of CRP (R2 = 0.62, p < 0.0001).
  
  
  CONCLUSIONS
  These findings indicate that physiological determinants of tissue oxygen availability are independently associated with CRP blood levels. Thus, improvement of tissue oxygen availability is a central therapeutic option to modulate the severity of systemic inflammatory processes in patients with COPD.
authors.affiliation: Department of Pneumology and Biomedical Engineering, Scientific Institute of Montescano, Salvatore Maugeri Foundation IRCCS, Pavia, Italy. simonetta.baldi@fsm.it
authors.forename: Simonetta
authors.initials: S
authors.lastname: Baldi
authors.forename: Gian Domenico
authors.initials: GD
authors.lastname: Pinna
authors.forename: Piera
authors.initials: P
authors.lastname: Mombaruzzo
authors.forename: Milena
authors.initials: M
authors.lastname: Biglieri
authors.forename: Angelo
authors.initials: A
authors.lastname: De Martini
authors.forename: Paolo
authors.initials: P
authors.lastname: Palange
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis*; D002263:Carboxyhemoglobin / Q000032:analysis; D005260:Female; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000209:etiology*; D018836:Inflammation Mediators / Q000097:blood*; D016014:Linear Models; D008297:Male; D008706:Methemoglobin / Q000032:analysis; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010108:Oxyhemoglobins / Q000032:analysis; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000150:complications; D012720:Severity of Illness Index
chemical_list: D015415:Biomarkers; D006454:Hemoglobins; D018836:Inflammation Mediators; D010108:Oxyhemoglobins; D002097:C-Reactive Protein; D008706:Methemoglobin; D002263:Carboxyhemoglobin; D010100:Oxygen