Weakness and Fluid Overload Hinder Weaning. Or Do They?

Weaning from mechanical ventilation is still a major challenge in critical care units. Prolonged ventilation is clearly associated with poor prognosis and increased mortality. For this reason, in recent years, many studies have aimed to identify which patients are ready to breathe on their own. Despite some controversial conclusions, most of us have included daily interruption of sedation, light sedation, and early mobilization to accelerate weaning in our practice. Despite these strategies, the rate of weaning and extubation failure in the last 15 years has remained as high as 13–18%.1 While we strive to discover the reasons for failure, we continue to do everything in our power to reduce the risk of keeping patients ventilated longer than absolutely necessary. The challenge is not only to identify which patients are ready to breathe without assistance, but also which ones will pass a spontaneous breathing trial (SBT) and be successfully extubated. This issue of RESPIRATORY CARE includes 2 articles2,3 exploring 2 reasons for failure: weakness and fluid balance. De Jonghe et al4 first described the relationship between limb and respiratory muscle weakness. They measured maximum inspiratory and expiratory pressures and vital capacity to evaluate respiratory strength and used the Medical Research Council scale to evaluate limb weakness, 2 factors that were closely correlated. Another study5 demonstrated that handgrip strength, an easy-to-measure variable, showed a good correlation with the accepted standard for weakness, the Medical Research Council scale. In this issue of RESPIRATORY CARE, Cottereau et al2 took this idea one step further and aimed to evaluate whether handgrip strength, as a surrogate for respiratory muscle function, predicts weaning and extubation success. The authors found that subjects with simple weaning had greater handgrip strength based on a single measurement on the first day of weaning before the first SBT, suggesting that they were strong enough to breathe spontaneously. However, handgrip strength was not associated with extubation failure defined as re-intubation or unscheduled noninvasive ventilation within 48 h after extubation. One can argue that a single measurement of strength is unlikely to predict weaning when the patient will not be extubated until a few days later. It would be interesting to know if the strength measured on the actual day of extubation might be a better predictor of extubation failure.