ANXIETY & WEANING FROM NIVV

Anxiety & weaning from NIVV

Anxiety & weaning from NIVV

Introduction

Weaning from mechanical ventilation can be defined as the process of abruptly or gradually withdrawing ventilatory support. Two large multicenter studies [1,2] have demonstrated that mechanical ventilation can be discontinued abruptly in approximately 75% of mechanically ventilated patients whose underlying cause of respiratory failure has either improved or been resolved. The remaining patients will need progressive withdrawal from mechanical ventilation.

Weaning from mechanical ventilation usually implies two separate but closely related aspects of care, discontinuation of mechanical ventilation and removal of any artificial airway. The first problem the clinician faces is how to determine when a patient is ready to resume ventilation on his or her own. Several studies [1,2,3,4,5] have shown that a direct method of assessing readiness to maintain spontaneous breathing is simply to initiate a trial of unassisted breathing. Once a patient is able to sustain spontaneous breathing, a second judgement must be made regarding whether the artificial airway can be removed. This decision is made on the basis of the patient's mental status, airway protective mechanisms, ability to cough and character of secretions. If the patient has an adequate sensorium with intact airway protection mechanisms, and is without excessive secretions, it is reasonable to extubate the trachea.

A team approach and an organized problem-orientated plan are important to expedite successful discontinuation of mechanical ventilation. Ely et al [4] recently demonstrated that a protocol of weaning is superior to the physician's individual decision-making at the bedside. They enrolled 300 mechanically ventilated medical and nonsurgical cardiac patients into a randomized, controlled trial in which the treatment group was weaned using a two-step process of daily screening by respiratory care practitioners followed by spontaneous breathing trials when recovery was sufficient to pass the daily screen. Those investigators found that removal from mechanical ventilation was 2 days earlier in the protocol-directed group. The use of the protocol to manage just four patients (95% confidence interval 3-5) would result in one individual being off mechanical ventilation after 48 h who otherwise would not have been.

Discussion

Practice guidelines on weaning should be based on carefully performed clinical studies. Few areas in critical care have been evaluated as extensively by well-designed studies over the past decade as the discontinuation of mechanical ventilation. Therefore, every step in the process of weaning is supported by the results of at least one randomized clinical trial. In the present review the procedures that should be incorporated into a weaning algorithm are discussed, taking into account the results of the aforementioned studies.

Weaning procedures are usually started only after the underlying disease process that necessitated mechanical ventilation has significantly improved or is resolved. The patient should also have an adequate gas exchange (most studies define this condition as an arterial oxygen tension/fractional inspired oxygen ratio higher than 200), appropriate neurological and muscular status, and stable cardiovascular function.

Several studies [10,11,12] have reported that pretest probability of weaning success ranges from 50 to 70% when patients are identified by clinical judgement as being ...