A recent review evaluated the effects of respiratory muscle training (RMT) on lung function and mechanical ventilation outcomes in adult patients. The authors address a clinically important issue: mechanically ventilated patients frequently develop respiratory muscle weakness and diaphragmatic atrophy due to prolonged disuse, sedation and neuromuscular blockade, which can delay weaning, increase complications and prolong hospitalisation. Although early mobilisation strategies target limb weakness, respiratory muscle dysfunction remains common and is strongly associated with prolonged ventilation, infections and poorer recovery. This study aimed to determine whether structured respiratory training improves objective measures of lung function and reduces mechanical ventilation duration in this population.
Eligible participants were adults (≥18 years) receiving invasive mechanical ventilation for more than 48 hours in an ICU. Interventions consisted of respiratory muscle strength training delivered through various methods, including inspiratory muscle training (IMT) devices, expiratory training, neuromuscular electrical stimulation, chest physiotherapy or combined pulmonary rehabilitation. Control groups received usual care, conventional physiotherapy or sham interventions. Primary outcomes were maximum inspiratory pressure (MIP), forced vital capacity (FVC) and duration of mechanical ventilation.
Meta-analysis showed consistent benefits of respiratory muscle training. For inspiratory muscle strength, 14 studies involving 762 participants demonstrated a significant improvement in MIP, favouring RM. For lung volumes, six studies (257 participants) reported significantly higher FVC after training. Importantly, six studies including 347 participants showed that RMT reduced mechanical ventilation duration by an average of 0.88 days, indicating faster weaning and earlier liberation from ventilatory support. Subgroup analyses suggested that both IMT and non-IMT techniques improved MIP, implying that benefits are not restricted to a single training method.
The authors discuss several physiological mechanisms underlying these findings. Prolonged ventilation leads to ventilator-induced diaphragmatic dysfunction characterised by atrophy, oxidative stress and proteolysis. RMT provides an overload stimulus that enhances neural drive, motor unit recruitment and muscle protein synthesis, thereby restoring respiratory muscle strength and endurance. Improvements in FVC may facilitate better lung expansion, secretion clearance and alveolar recruitment, all of which support successful weaning. Even modest reductions in ventilation time may have meaningful clinical consequences by lowering the risk of ventilator-associated complications and reducing ICU costs.
Compared with earlier reviews that focused solely on inspiratory muscle training or limited outcomes, this analysis incorporated a broader range of respiratory techniques and included lung function parameters such as FVC. The authors argue that comprehensive respiratory rehabilitation engaging both inspiratory and expiratory muscles may better reflect real-world practice. The consistency of positive effects across modalities supports integrating some form of respiratory-specific exercise into ICU rehabilitation protocols.
In conclusion, this review demonstrates that respiratory muscle training improves inspiratory muscle strength, enhances lung volumes and modestly shortens the duration of mechanical ventilation in ICU patients. The authors recommend early implementation of respiratory training as part of routine rehabilitation for mechanically ventilated individuals. Future research should involve larger, multicentre RCTs with standardised protocols, consistent outcome reporting, inclusion of patient-centred measures such as length of stay and functional recovery, and better documentation of safety to refine clinical guidelines and optimise respiratory rehabilitation strategies.
Source: BMC Pulmonary Medicine
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