Abstract
Purpose: The automated recognition of critical clinical events by physiological monitors is a challenging task exacerbated by a lack of standardized and clinically relevant threshold criteria. The objective of this investigation was to develop consensus for such criteria regarding the identification of three ventilatory events: disconnection or significant leak in the anesthesia circuit, decreased lung compliance or increased resistance, and anesthetic overdose from inhaled anesthetics.
Methods: We individually administered a structured interview to five expert anesthesiologists to gain insight into the cognitive processes used by clinicians to diagnose ventilatory events and to determine the common heuristics (rules of thumb) used in clinical practice. We then used common themes, identified from analysis of the structured interviews, to generate questions for a series of web-based questionnaires. Using a modified Delphi technique, iterative questionnaire administration facilitated rapid consensus development on the thresholds for the specific rules used to identify ventilatory events.
Results: A threshold for 75% agreement was described for each scenario in a healthy ventilated adult. A disconnection or significant leak in the anesthesia circuit is diagnosed with peak airway pressure (<5 cm H2O or change of 15 cm H2O), ETCO2 (0 mmHg, 40% drop, or value below 10 mmHg for a duration of 20 sec), and inspired-expired volume difference (300 mL). Increased resistance or decreased lung compliance is diagnosed with high peak airway pressure (40 cm H2O or a 20 cm H2O change), asymmetry of capnogram, and changes in measured compliance or resistance. Anesthetic overdose from inhaled anesthetics is diagnosed with high end-tidal anesthetic agent concentration (2 MAC in a patient less than 60 yr of age or 1.75 MAC in a patient over 60 yr of age), low systolic blood pressure (below 60 mmHg), and low modified electroencephalogram (bispectral index or entropy).
Conclusion: This investigation has provided a set of consensus-based criteria for developing rules for the identification of three critical ventilatory events and has presented insight into the decision heuristics used by clinicians.
Résumé
Objectif: La reconnaissance automatisée des événements cliniques critiques par des moniteurs physiologiques constitue un défi rendu difficile par le manque de critères de seuils standardisés et pertinents d’un point de vue clinique. L’objectif de cette étude était de parvenir à un consensus par rapport aux critères nécessaires à l’identification de trois événements respiratoires : une déconnexion ou une fuite considérable du circuit anesthésique, une compliance pulmonaire diminuée ou une résistance accrue, et une overdose anesthésique résultant des anesthésiques inhalés.
Méthode: Nous avons individuellement mené des entretiens structurés de cinq anesthésiologistes experts afin d’avoir un aperçu des processus cognitifs utilisés par les cliniciens pour dépister les événements respiratoires et de déterminer les connaissances heuristiques communes (règle empirique) utilisées dans la pratique clinique. Ensuite, nous nous sommes servis des thèmes communs identifiés par l’analyse des entretiens structurés afin de générer des questions pour une série de questionnaires en ligne. À l’aide d’une méthode de Delphi modifiée, l’administration itérative des questionnaires a permis le développement rapide d’un consensus concernant les seuils pour les règles spécifiques utilisées dans l’identification des événements respiratoires.
Résultats: Pour chaque scénario chez un adulte sain ventilé, un seuil de concordance de 75 % a été décrit. Une déconnexion ou fuite considérable du circuit anesthésique est diagnostiquée lors d’une pression maximale du conduit aérien (< 5 cm H2O ou changement de 15 cm H2O), ETCO2 (0 mmHg, chute de 40 %, ou valeur en dessous de 10 mmHg pour une durée de 20 sec), et d’une différence de volume inspiré-expiré (300 mL). Une résistance accrue ou une compliance pulmonaire réduite est diagnostiquée lors d’une pression maximale du conduit aérien élevée (40 cm H2O ou un changement de 20 cm H2O), un capnogramme asymétrique, et de changements dans la compliance ou la résistance mesurées. Une overdose anesthésique provoquée par les anesthésiques inhalés est diagnostiquée lors d’une concentration d’anesthésique télo-expira-toire élevée (2 MAC chez un patient de moins de 60 ans ou 1,75 MAC chez un patient de plus de 60 ans), de pression systolique basse (inférieure à 60 mmHg) et d’électroencéphalogramme modifié bas (index bispectral ou moniteur entropy).
Conclusion: Cette étude a permis de déterminer un ensemble de critères basés sur un consensus pour le développement de règles permettant l’identification de trois événements respiratoires critiques et a donné un aperçu des connaissances heuristiques utilisés par les cliniciens pour prendre des décisions cliniques.
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Support has been provided by an operating grant (MOP — 79418) from the Canadian Institutes of Health Research, and the Canadian Anesthesiologists’ Society. Mark Ansermino is a Michael Smith Foundation for Health Research Scholar, has received operating grants from the Natural Sciences and Engineering Research Council of Canada, and has a research agreement with Draeger Medical for research unrelated to this project. Mark Ansermino is co-recipient of operating grants from the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council of Canada, the Michael Smith Foundation for Health Research, and the Child & Family Research Institute. Stephan Schwarz and Mark Ansermino are recipients of a Canadian Anesthesiologists’ Society/Abbott Laboratories Ltd Career Scientist Award in Anesthesia. Stephan Schwarz holds an independently peer-reviewed research grant sponsored by Pfzer Canada, unrelated to this research, and is co-recipient of operating grants from the Natural Sciences and Engineering Research Council of Canada and the Canadian Institutes of Health Research. There are no commercial or non-commercial affliations that were, or might be perceived to be, a confict of interest for the other authors.
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Ansermino, J.M., Dosani, M., Amari, E. et al. Defining rules for the identifcation of critical ventilatory events. Can J Anaesth 55, 702–714 (2008). https://doi.org/10.1007/BF03017747
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DOI: https://doi.org/10.1007/BF03017747