Hypoventilation patterns during bronchoscopic sedation and their clinical relevance based on capnographic and respiratory impedance analysis

Published

Journal Article

© 2019, Springer Nature B.V. Capnography involves the measurement of end-tidal CO 2 (EtCO 2 ) values to detect hypoventilation in patients undergoing sedation. In a previous study, we reported that initiating a flexible bronchoscopy (FB) examination only after detecting signs of hypoventilation could reduce the risk of hypoxemia without compromising the tolerance of the patient for this type of intervention. We hypothesize that hypoventilation status could be determined with greater precision by combining thoracic impedance-based respiratory signals, RESP, and EtCO 2 signals obtained from a nasal-oral cannula. Retrospective analysis was conducted on RESP and EtCO 2 waveforms obtained from patients during the induction of sedation using propofol for bronchoscopic examination in a previous study. EtCO 2 waveforms associated with hypoventilation were then compared with RESP patterns, patient variables, and sedation outcomes. Signals suitable for analysis were obtained from 44 subjects, 42 of whom presented indications of hypoventilation, as determined by EtCO 2 waveforms. Two subtypes of hypoventilation were identified by RESP: central-predominant (n = 22, flat line RESP pattern) and non-central-predominant (n = 20, RESP pattern indicative of respiratory effort with upper airway collapse). Compared to cases of non-central-predominant hypoventilation, those presenting central-predominant hypoventilation during induction were associated with a lower propofol dose (40.2 ± 18.3 vs. 60.8 ± 26.1 mg, p = 0.009), a lower effect site concentration of propofol (2.02 ± 0.33 vs. 2.38 ± 0.44 µg/ml, p = 0.01), more rapid induction (146.1 ± 105.5 vs. 260.9 ± 156.2 s, p = 0.01), and lower total propofol dosage (96.6 ± 41.7 vs. 130.6 ± 53.4 mg, p = 0.04). Hypoventilation status (as revealed by EtCO 2 levels) could be further classified by RESP into central-predominant or non-central-predominant types. It appears that patients with central-predominant hypoventilation are more sensitive to propofol during the induction of sedation. RESP values could be used to tailor sedation management specifically to individual patients.

Full Text

Duke Authors

Cited Authors

  • Lo, YL; Wu, HT; Lin, YT; Kuo, HP; Lin, TY

Published Date

  • January 1, 2019

Published In

Electronic International Standard Serial Number (EISSN)

  • 1573-2614

International Standard Serial Number (ISSN)

  • 1387-1307

Digital Object Identifier (DOI)

  • 10.1007/s10877-019-00269-0

Citation Source

  • Scopus