Weaning Success Rate With High-Intensity and Sham Inspiratory Muscle Training

Failure to wean from mechanical ventilation is common, affecting up to 35% of critically ill patients undergoing the weaning process and significantly worsening outcomes, including prolonged ICU stays, longer hospitalisations, and higher mortality risk. Respiratory muscle weakness, present in over 60% of mechanically ventilated patients, is a major contributing factor due to an imbalance between ventilatory load and respiratory capacity. 

Inspiratory muscle training (IMT) has been proposed to address this issue by improving inspiratory muscle strength, such as maximal inspiratory pressure (PImax), and potentially facilitating weaning.

While IMT protocols typically involve daily sessions with varying load intensities (10–50% of PImax), studies on IMT are heterogeneous and often utilise different devices, including traditional pressure threshold and newer electronic devices. Most studies lack sham control groups and rarely target patients with weaning difficulties specifically, despite evidence suggesting they could benefit most from IMT. 

A recent study compared the effects of high-intensity IMT (Hi-IMT) to sham low-intensity IMT (Lo-IMT) on respiratory function, weaning success, ICU length of stay, and pulmonary outcomes in patients with weaning difficulties. The hypothesis was that Hi-IMT would lead to greater respiratory muscle improvements, higher weaning success rates, and shorter ICU stays compared to Lo-IMT. Findings from this study build on previous exploratory research into IMT’s effects on muscle oxygenation.

Two groups participated in daily IMT sessions for up to 28 days or until successful weaning. The Hi-IMT group trained with an external load of 30-50% of their PImax, while the control group used a lighter load of ≤10% PImax.

Training adherence was similar between groups. Both groups showed comparable weaning success rates and weaning durations. PImax improved similarly in both groups. However, the Hi-IMT group showed significantly greater improvement in forced vital capacity. 

Despite higher external workloads in the Hi-IMT group, both groups achieved similar weaning success rates (Hi-IMT: 64%, Lo-IMT: 76%) and PImax improvements. Both interventions were safe, feasible, and adhered to at high rates.

Unexpectedly, the Lo-IMT group showed more favourable outcomes than anticipated, potentially because the Lo-IMT protocol was more demanding than intended and the Lo-IMT group had slightly more advanced weaning progress at baseline, including more spontaneous breathing periods and better respiratory mechanics.

While Hi-IMT improved forced vital capacity more than Lo-IMT, these findings suggest that IMT, regardless of intensity, may not significantly influence weaning outcomes in isolation. Multifactorial contributors, such as respiratory mechanics, cardiac, and neurological factors, play critical roles in weaning success, highlighting the need for comprehensive management. Additionally, the study’s Lo-IMT group outcomes exceeded those in previous trials, possibly due to differences in IMT instructions and patient characteristics.

With high adherence, both high-intensity IMT and sham low-intensity IMT achieved similar weaning success rates and significant improvements in maximal inspiratory muscle strength.

Source: AJRCCM

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