SESSION TITLE: Respiratory Support Posters
SESSION TYPE: Original Investigation Poster
PRESENTED ON: Wednesday, October 30, 2013 at 01:30 PM - 02:30 PM
PURPOSE: In the weaning literature and in our clinical experience, depressed mental status is a poor prognostic factor for successful weaning. In the setting of obtundation we have observed an airflow pattern in which each inspiration consists of an initial effort of moderate duration (whose flow tracing is dome shaped) followed by a second brief effort (spike shaped tracing) . This flow pattern has been consistently associated with a failure of sustainable spontaneous ventilation. This study was undertaken in order to delineate the mechanism of this inspiratory flow pattern.
METHODS: Design: observational study Ten patients transferred from the ICU for weaning were evaluated. All had been sedated until transfer to the medical floor and had Ramsey scores between 5 and 6 at the time of transfer. Oxygenation was quantitated with the p/f score, and mechanics were evaluated in each patient with measurements of compliance, resistance and PEEPi. Respiratory muscle function was assessed with the rapid shallow breathing index (RSBI) and the respiratory muscle recruitment pattern. The relationship between the activity pattern of the respiratory muscles and the inspiratory flow pattern was evaluated by physical examination during unsupported spontaneous breathing. This was correlated with simultaneous inspiratory flow tracings displayed on the Puritan Bennett 840 mechanical ventilator. The inspiratory flow pattern and ability to breathe were evaluated with spontaneous breathing trials (SBTs) using no continuous positive airway pressure (CPAP) or pressure support (PSV).
RESULTS: 1) All ten patients demonstrated dome and spike inspiratory flow at the time of evaluation. 2) This pattern was found to reflect an initial inspiratory effort by the intercostals followed by a paroxysmal diaphragmatic contraction. This pattern was distinct from the diaphragmatic paradox which is associated with respiratory failure. 3) All patients had highly acceptable gas exchange, mechanics and RSBI. 4) During the SBT all patients showed a progressive rise in RSBI from a mean of 70 to more than 130 with progressively higher levels of respiratory muscle recruitment over a 2 hour period. None could maintain independent ventilation.
CONCLUSIONS: Dome and Spike inspiratory gas flow reflects respiratory center dysfunction with discoordination of chest wall muscles and diaphragm and is an independent cause of ventilatory insufficiency .
CLINICAL IMPLICATIONS: The inspiratory air flow pattern should be evaluated as part of any weaning assessment.
DISCLOSURE: The following authors have nothing to disclose: William Marino
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