title: Frequency dependence of capnography in anesthetized rabbits.
abstract: Aspirative capnography may be of help to diagnose early childhood asthma, but clinical usefulness in young children is limited by the relatively high respiratory rate. This study aimed to characterize the [Formula: see text] time course during airway constriction in 8 anesthetized rabbits, artificially ventilated at 30, 60 and 80breaths/min. Methacholine was inhaled to double the respiratory resistance measured at 8Hz by the forced oscillation technique. The capnogram shape changed in response to both methacholine and ventilatory frequency. Slope of phase II, the peak of first-order time derivative and trough of the second-order time derivative of the [Formula: see text] signal, were significantly attenuated after methacholine compared with baseline at all breathing rates (p<0.02). Moreover, significant correlations between respiratory reactance and resistance were observed with the phase III slope and the angle described by phase II and phase III (p<0.01). It is concluded that capnography may be useful to identify acute airway changes related to bronchoconstriction, even at high breathing frequencies.
authors.affiliation: Service d'explorations fonctionnelles pédiatriques, Hôpital d'Enfants, CHU de Nancy, France.
authors.forename: I
authors.initials: I
authors.lastname: Ioan
authors.forename: B
authors.initials: B
authors.lastname: Demoulin
authors.forename: C
authors.initials: C
authors.lastname: Duvivier
authors.forename: A L
authors.initials: AL
authors.lastname: Leblanc
authors.forename: C
authors.initials: C
authors.lastname: Bonabel
authors.forename: F
authors.initials: F
authors.lastname: Marchal
authors.forename: C
authors.initials: C
authors.lastname: Schweitzer
authors.forename: S
authors.initials: S
authors.lastname: Varechova
mesh_terms: D000403:Airway Resistance / Q000187:drug effects / Q000502:physiology; D000758:Anesthesia; D000818:Animals; D016084:Bronchoconstriction / Q000187:drug effects / Q000502:physiology*; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D019296:Capnography; D016210:Methacholine Chloride / Q000494:pharmacology; D011817:Rabbits; D012119:Respiration / Q000187:drug effects; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride
keywords: Artificial ventilation; Asthma; Bronchoconstriction; Expired CO(2); Forced oscillations; Methacholine