title: Relationship between pre-anesthetic and intra-anesthetic airway resistance in patients undergoing general anesthesia: A prospective observational study.
abstract: Surgery patients in Japan undergo routine spirometry testing prior to general anesthesia. The use of a flow sensor during general anesthesia has recently become common. However, it is not certain whether the information derived from flow-volume curves is being adequately used for mechanical ventilation management during general anesthesia. So far, there have been no attempts to calculate airway resistance using flow-volume curves. Therefore, we performed a prospective, observational study to investigate the relationship between pre-anesthetic and intra-anesthetic airway resistance in patients scheduled for surgery under general anesthesia. We calculated pre-anesthetic and intra-anesthetic airway resistance in each patient, based on the slopes of flow-volume curves obtained prior to and during general anesthesia. We also calculated endotracheal tube resistance to correct the intra-anesthetic airway resistance values calculated. A total of 526 patients were included in the study, and 98 patients had a forced expiratory volume in the first second/forced vital capacity ratio of < 70%. Pre-anesthetic airway resistance was significantly higher in patients with airflow obstruction than in those without airflow obstruction (p < 0.001), whereas no significant difference in intra-anesthetic airway resistance was found between patients with and without airflow obstruction during mechanical ventilation (p = 0.48). Pre-anesthetic and intra-anesthetic airway resistance values were closer to each other in patients without airflow obstruction, with a mean difference < 1.0 cmH2O L-1s-1, than in those with airflow obstruction, although these respiratory parameters were significantly different (p < 0.001). Intra-anesthetic airway resistance was not related to the FEV1/FVC ratio, regardless of the degree to which the FEV1/FVC ratio reflected pre-anesthetic airway resistance. As compared with patients with airflow obstruction, the mean difference between pre-anesthetic and intra-anesthetic airway resistance was small in patients without airflow obstruction.
authors.affiliation: Department of Anesthesiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Ikeda
authors.affiliation: Department of Anesthesiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Kanji
authors.initials: K
authors.lastname: Uchida
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yamauchi
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Takahide
authors.initials: T
authors.lastname: Nagase
authors.affiliation: Department of Biostatistics, School of Public Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Oba
authors.affiliation: Department of Anesthesiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Yoshitsugu
authors.initials: Y
authors.lastname: Yamada
mesh_terms: D000293:Adolescent; D000328:Adult; D000403:Airway Resistance / Q000187:drug effects* / Q000502:physiology*; D000768:Anesthesia, General; D018681:Anesthetics, General / Q000494:pharmacology*; D005541:Forced Expiratory Volume; D006801:Humans; D011446:Prospective Studies; D012121:Respiration, Artificial; D013147:Spirometry; D013990:Tidal Volume; D014797:Vital Capacity
chemical_list: D018681:Anesthetics, General