BACKGROUND: Diaphragm dysfunction is defined by a value of twitch tracheal pressure in response to magnetic phrenic stimulation (twitch pressure) amounting to less than 11 cmH2O. This study assessed whether this threshold or a lower one would predict accurately weaning failure from mechanical ventilation. Twitch pressure was compared to ultrasound measurement of diaphragm function.
METHODS: In patients undergoing a first spontaneous breathing trial, diaphragm function was evaluated by twitch pressure and by diaphragm ultrasound (thickening fraction). Receiver operating characteristics curves were computed to determine the best thresholds predicting failure of spontaneous breathing trial.
RESULTS: Seventy-six patients were evaluated, 48 (63%) succeeded and 28 (37%) failed the spontaneous breathing trial. The optimal thresholds of twitch pressure and thickening fraction to predict failure of the spontaneous breathing trial were, respectively, 7.2 cmH2O and 25.8%, respectively. The receiver operating characteristics curves were 0.80 (95% CI 0.70-0.89) for twitch pressure and 0.82 (95% CI 0.73-0.93) for thickening fraction. Both receiver operating characteristics curves were similar (p = 0.83). A twitch pressure value lower than 11 cmH2O (the traditional cutoff for diaphragm dysfunction) predicted failure of the spontaneous breathing trial with a sensitivity of 89% (95% CI 72-98%) and a specificity of 45% (95% CI 30-60%).
CONCLUSIONS: Failure of spontaneous breathing trial can be predicted with a lower value of twitch pressure than the value defining diaphragm dysfunction. Twitch pressure and thickening fraction had similar strong performance in the prediction of failure of the spontaneous breathing trial.

BACKGROUND: The debate within the multiple sclerosis (MS) community initiated by the chronic cerebrospinal venous insufficiency (CCSVI) hypothesis and the subsequent liberation procedure placed some people with MS at odds with health care professionals and researchers.
OBJECTIVE: This study explored decision making regarding the controversial liberation procedure among people with MS.
METHODS: Fifteen people with MS (procedure, n=7; no procedure, n=8) participated in audiotaped semistructured interviews exploring their thoughts and experiences related to the liberation procedure. Data were transcribed and analyzed using an iterative, consensus-based, thematic content-analysis approach.
RESULTS: Participants described an imbalance of motivating factors affirming the procedure compared to hesitating factors that provoked the participant to pause or reconsider when deciding to undergo the procedure. Collegial conversational relationships with trusted sources (eg, MS nurse, neurologist) and ability to critically analyze the CCSVI hypothesis were key hesitating factors. Fundraising, family enthusiasm, and the ease of navigation provided by medical tourism companies helped eliminate barriers to the procedure.
CONCLUSIONS: Knowledge of factors that helped to popularize the liberation procedure in Canada may inform shared decision making concerning this and future controversies in MS.