title: Effects of acute hypoventilation and hyperventilation on exhaled carbon monoxide measurement in healthy volunteers.
abstract: BACKGROUND
  High levels of exhaled carbon monoxide (eCO) are a marker of airway or lung inflammation. We investigated whether hypo- or hyperventilation can affect measured values.
  
  
  METHODS
  Ten healthy volunteers were trained to achieve sustained end-tidal CO2 (etCO(2)) concentrations of 30 (hyperventilation), 40 (normoventilation), and 50 mmHg (hypoventilation). As soon as target etCO(2) values were achieved for 120 sec, exhaled breath was analyzed for eCO with a photoacoustic spectrometer. At etCO(2) values of 30 and 40 mmHg exhaled breath was sampled both after a deep inspiration and after a normal one. All measurements were performed in two different environmental conditions: A) ambient CO concentration = 0.8 ppm and B) ambient CO concentration = 1.7 ppm.
  
  
  RESULTS
  During normoventilation, eCO mean (standard deviation) was 11.5 (0.8) ppm; it decreased to 10.3 (0.8) ppm during hyperventilation (p < 0.01) and increased to 11.9 (0.8) ppm during hypoventilation (p < 0.01). eCO changes were less pronounced than the correspondent etCO(2) changes (hyperventilation: 10% Vs 25% decrease; hypoventilation 3% Vs 25% increase). Taking a deep inspiration before breath sampling was associated with lower eCO values (p < 0.01), while environmental CO levels did not affect eCO measurement.
  
  
  CONCLUSIONS
  eCO measurements should not be performed during marked acute hyperventilation, like that induced in this study, but the influence of less pronounced hyperventilation or of hypoventilation is probably negligible in clinical practice.
authors.affiliation: Institute of Anaesthesia and Intensive Care, Catholic University of the Sacred Heart, Rome, Italy. f.cavaliere@rm.unicatt.it
authors.forename: Franco
authors.initials: F
authors.lastname: Cavaliere
authors.forename: Carmen
authors.initials: C
authors.lastname: Volpe
authors.forename: Riccardo
authors.initials: R
authors.lastname: Gargaruti
authors.forename: Andrea
authors.initials: A
authors.lastname: Poscia
authors.forename: Michele
authors.initials: M
authors.lastname: Di Donato
authors.forename: Giovanni
authors.initials: G
authors.lastname: Grieco
authors.forename: Umberto
authors.initials: U
authors.lastname: Moscato
mesh_terms: D000328:Adult; D001944:Breath Tests; D002245:Carbon Dioxide / Q000378:metabolism; D002248:Carbon Monoxide / Q000378:metabolism*; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D006985:Hyperventilation / Q000378:metabolism*; D007040:Hypoventilation / Q000378:metabolism*; D008297:Male; D013990:Tidal Volume / Q000502:physiology; D013997:Time Factors; D014797:Vital Capacity / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D002248:Carbon Monoxide