title: The Use of Pulse Oximetry to Determine Hypoxemia in Acute Exacerbations of COPD.
abstract: BACKGROUND
  There is little evidence that the guideline-recommended oxygen saturation of 92% is the best cut-off point for detecting hypoxemia in COPD exacerbations.
  
  
  OBJECTIVE
  To detect and validate pulse oximetry oxygen saturation cut-off values likely to detect hypoxemia in patients with aeCOPD, to explore the correlation between oxygen saturation measured by pulse oximetry and hypoxemia or hypercapnic respiratory failure.
  
  
  METHODS
  Cross-sectional study nested in the IRYSS-COPD study with 2,181 episodes of aeCOPD recruited between 2008 and 2010 in 16 hospitals belonging to the Spanish Public Health System. Data collected include determination of oxygen saturation by pulse oximetry upon arrival in the emergency department (ED), first arterial blood gasometry values, sociodemographic information, background medical history and clinical variables upon ED arrival. Logistic regression models were performed using as the dependent variables hypoxemia (PaO2 < 60 mmHg) and hypercapnic respiratory failure (PaO2 < 60 mmHg and PaCO2 > 45). Optimal cut-off points were calculated.
  
  
  RESULTS
  The correlation coefficient between oxygen saturation and pO2 measured by arterial blood gasometry was 0.89. The area under the curve (AUC) for the hypoxemia model was 0.97 (0.96-0.98) and the optimal cut-off point for hypoxemia was an oxygen saturation of 90%. The AUC for hypercapnic respiratory failure was 0.90 (0.87-0.92) and the optimal cut-off point was an oxygen saturation of 88%.
  
  
  CONCLUSIONS
  Our results support current recommendations for ordering blood gasometry based on pulse oximetry oxygen saturation cut-offs for hypoxemia. We also provide easy to use formulae to calculate pO2 from oxygen saturation measured by pulse oximetry.
authors.affiliation: a Unidad de Investigación, Hospital Galdakao-Usansolo (Osakidetza)-Red de Investigación en Servicios de Salud en Enfermedades Crónicas (REDISSEC) , Galdakao , Bizkaia , Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Garcia-Gutierrez
authors.affiliation: a Unidad de Investigación, Hospital Galdakao-Usansolo (Osakidetza)-Red de Investigación en Servicios de Salud en Enfermedades Crónicas (REDISSEC) , Galdakao , Bizkaia , Spain.
authors.forename: Anette
authors.initials: A
authors.lastname: Unzurrunzaga
authors.affiliation: b Departamento de Matemática Aplicada y Estadística e Investigación Operativa-Universidad del País Vasco UPV/EHU-Red de Investigación en Servicios de Salud en Enfermedades Crónicas (REDISSEC), Leioa , Bizkaia.
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Arostegui
authors.affiliation: a Unidad de Investigación, Hospital Galdakao-Usansolo (Osakidetza)-Red de Investigación en Servicios de Salud en Enfermedades Crónicas (REDISSEC) , Galdakao , Bizkaia , Spain.
authors.forename: Jose María
authors.initials: JM
authors.lastname: Quintana
authors.affiliation: c Servicio de Urgencias , Hospital Galdakao-Usansolo , Galdakao , Bizkaia , Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Pulido
authors.affiliation: c Servicio de Urgencias , Hospital Galdakao-Usansolo , Galdakao , Bizkaia , Spain.
authors.forename: Maria Soledad
authors.initials: MS
authors.lastname: Gallardo
authors.affiliation: d Servicio de Respiratorio - Red de Investigación en Servicios de Salud en Enfermedades Crónicas (REDISSEC), Hospital Galdakao-Usansolo (Osakidetza) , Galdakao , Bizkaia , Spain.
authors.forename: Cristóbal
authors.initials: C
authors.lastname: Esteban
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000175:diagnosis* / Q000209:etiology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000150:complications*; D012372:ROC Curve; D012131:Respiratory Insufficiency / Q000175:diagnosis* / Q000209:etiology; D013030:Spain
keywords: diagnosis; emergency department; respiratory failure; validation