title: A Comparison of Different Techniques for Interfacing Capnography With Adult and Pediatric Supplemental Oxygen Masks.
abstract: BACKGROUND
  Accurately measuring the partial pressure of end-tidal CO2(PETCO2) in non-intubated patients is problematic due to dilution of expired CO2at high O2flows and mask designs that may either cause CO2rebreathing or inadequately capture expired CO2. We evaluated the performance of 2 capnographic O2masks (Cap-ONE and OxyMask) against a clinically expedient method using a standard O2mask with a flow-directed nasal cannula used for capnography (CapnoLine) in a spontaneous breathing model of an adult and child under conditions of normal ventilation, hypoventilation, and hyperventilation.
  
  
  METHODS
  An ASL-5000 simulator was attached to a manikin face with a catheter port, through which various CO2/air mixtures were bled into the ASL-5000 to achieve a PETCO2of 40, 65, and 30 mm Hg. Both PETCO2and inspired PCO2were measured at O2flows of 5, 10, 15, and 20 L/min (adult model) and 2, 4, 6, 8, and 10 L/min (pediatric model).
  
  
  RESULTS
  PETCO2decreased to varying degrees as O2flow increased, depending upon the breathing pattern. Although all devices appeared to perform reasonably well under normal and hyperventilation conditions, the clinically expedient method was associated with substantially more CO2rebreathing. PETCO2usually deteriorated more under simulated hypoventilation, regardless of the measurement method.
  
  
  CONCLUSIONS
  Both of the specially designed O2capnography masks provided reasonably stable PETCO2without significant CO2rebreathing at the commonly used O2flows. Because of their open design, PETCO2measured at high O2flows may produce artificially lower readings that may not reflect arterial CO2levels compared with lower O2flows.
authors.affiliation: Respiratory Care Services, Department of Anesthesia and Perioperative Care, University of California, San Francisco at Zuckerberg San Francisco General Hospital, San Francisco, California. Justin.Phillips@ucsf.edu.
authors.forename: Justin S
authors.initials: JS
authors.lastname: Phillips
authors.affiliation: Respiratory Care Services, Department of Anesthesia and Perioperative Care, University of California, San Francisco at Zuckerberg San Francisco General Hospital, San Francisco, California.
authors.forename: Lance P
authors.initials: LP
authors.lastname: Pangilinan
authors.affiliation: Respiratory Care Services, Department of Anesthesia and Perioperative Care, University of California, San Francisco at Zuckerberg San Francisco General Hospital, San Francisco, California.
authors.forename: Earl R E
authors.initials: ER
authors.lastname: Mangalindan
authors.affiliation: Respiratory Care Services, Department of Anesthesia and Perioperative Care, University of California, San Francisco at Zuckerberg San Francisco General Hospital, San Francisco, California.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Booze
authors.affiliation: Respiratory Care Services, Department of Anesthesia and Perioperative Care, University of California, San Francisco at Zuckerberg San Francisco General Hospital, San Francisco, California.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Kallet
mesh_terms: D000328:Adult; D000072601:Cannula; D019296:Capnography / Q000295:instrumentation* / Q000379:methods; D002245:Carbon Dioxide / Q000032:analysis*; D002648:Child; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology; D007040:Hypoventilation / Q000503:physiopathology; D008168:Lung / Q000502:physiology; D008397:Masks; D008954:Models, Biological; D010100:Oxygen / Q000008:administration & dosage*; D010313:Partial Pressure; D012119:Respiration
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen
keywords: end-tidal carbon dioxide; oxygen therapy; sidestream capnography; volumetric capnography