Assessing the effects of inspiratory muscle training in a patient with unilateral diaphragm dysfunction

Respiratory muscle dysfunction in acute and chronic respiratory failure: how to diagnose and how to treat?

Assessing and treating respiratory muscle dysfunction is crucial for patients with both acute and chronic respiratory failure. Respiratory muscle dysfunction can contribute to the onset of respiratory failure and may also worsen due to interventions aimed at treatment. Evaluating respiratory muscle function is particularly valuable for diagnosing, phenotyping and assessing treatment efficacy in these patients. This review outlines established methods, such as measuring respiratory pressures, and explores novel techniques, including respiratory muscle neurophysiology assessments using electromyography and imaging with ultrasound.Additionally, we review various treatment strategies designed to support and alleviate the burden on overworked respiratory muscles or to enhance their capacity through training interventions. These strategies range from invasive and noninvasive mechanical ventilation approaches to specialised respiratory muscle training programmes. By summarising both established techniques and recent methodological advancements, this review aims to provide a comprehensive overview of the tools available in clinical practice for evaluating and treating respiratory muscle dysfunction. Our goal is to present a clear understanding of the current capabilities and limitations of these diagnostic and therapeutic approaches. Integrating advanced diagnostic methods and innovative treatment strategies should help improve patient management and outcomes. This comprehensive review serves as a resource for clinicians, equipping them with the necessary knowledge to effectively diagnose and treat respiratory muscle dysfunction in both acute and chronic respiratory failure scenarios.

Inspiratory muscle training for diaphragmatic dysfunction: A case series

Inspiratory muscle training (IMT) is used across various pathology domains to improve respiratory function. Limited literature exists which demonstrates IMT benefit among patients with Diaphragmatic dysfunction. 7 individuals with a mean age of 59.6yrs had unilateral diaphragmatic dysfunction (UDD) post cardiac surgery and were referred to a cardiac rehab program where an IMT strength based protocol was prescribed. IMT implementation over an average of 13 weeks yielded an average improvement in maximum inspiratory pressure (MIP) of 48 % (p value 0.018), peak inspiratory flow rate (PIFR) of 45 % (p value 0.018), forced expired volume in 1 sec (FEV1) of 15 % (p value 0.028) and forced vital capacity (FVC) of 15 % (p value 0.018). This case series of data adds to the limited evidence that exists currently and outlines the benefits of IMT application within unilateral diaphragmatic dysfunction.

Analysis and applications of respiratory surface EMG: report of a round table meeting

Surface electromyography (sEMG) can be used to measure the electrical activity of the respiratory muscles. The possible applications of sEMG span from patients suffering from acute respiratory failure to patients receiving chronic home mechanical ventilation, to evaluate muscle function, titrate ventilatory support and guide treatment. However, sEMG is mainly used as a monitoring tool for research and its use in clinical practice is still limited-in part due to a lack of standardization and transparent reporting. During this round table meeting, recommendations on data acquisition, processing, interpretation, and potential clinical applications of respiratory sEMG were discussed. This paper informs the clinical researcher interested in respiratory muscle monitoring about the current state of the art on sEMG, knowledge gaps and potential future applications for patients with respiratory failure.

[Neuralgic amyotrophy: a common cause of unilateral and bilateral diaphragmatic pareses]

There are several causes for unilateral or bilateral diaphragmatic paresis. The most common cause is an (intraoperative) injury to the phrenic nerve.However, in up to 20% of cases, no explanation can be found despite extensive workup. Neuralgic amyotrophy (NA, also known as Parsonage-Turner syndrome) is a common underdiagnosed multifocal autoimmune-inflammatory disease that predominantly affects proximal nerve segments of the upper extremities. Classic symptoms include acute onset of severe pain in the shoulder girdle with delayed onset of paresis of the shoulder and arm muscles. In at least 7% of cases, the phrenic nerve is also affected. Based on the annual incidence of NA of 1:1000, the entity as a cause of diaphragmatic dysfunction is probably not as uncommon as previously thought. However, clinical experience shows that this diagnosis is often not considered, and diaphragmatic paresis gets wrongly classified as idiopathic.This is particularly disastrous because in the early stage of NA, medical therapy with corticosteroids is mostly not considered and the possibility that surgical repair of the diaphragm may be performed prematurely, given that the condition may resolve spontaneously many months after symptom onset.The aim of the present article is to raise awareness of the entity of NA as a cause of diaphragmatic paresis and to establish a standardized approach to diagnosis and treatment.

Effects of inspiratory muscle training on exertional breathlessness in patients with unilateral diaphragm dysfunction: a randomised trial

Background

Unilateral diaphragm dysfunction (UDD) is an underdiagnosed cause of dyspnoea. Inspiratory muscle training (IMT) is the only conservative treatment for UDD, but the mechanisms of improvement are unknown. We characterised the effects of IMT on dyspnoea, exercise tolerance and respiratory muscle function in people with UDD.

Methods

15 people with UDD (73% male, 61±8 years) were randomised to 6 months of IMT (50% maximal inspiratory mouth pressure (PI,max), n=10) or sham training (10% PI,max, n=5) (30 breaths twice per day). UDD was confirmed by phrenic nerve stimulation and persisted throughout the training period. Symptoms were assessed by the transitional dyspnoea index (TDI) and exercise tolerance by constant-load cycle tests performed pre- and post-training. Oesophageal (Pes) and gastric (Pga) pressures were measured with a dual-balloon catheter. Electromyography (EMG) and oxygenation (near-infrared spectroscopy) of respiratory muscles were assessed continuously during exercise.

Results

The IMT group (from 45±6 to 62±23% PI,max) and sham group (no progression) completed 92 and 86% of prescribed sessions, respectively. PI,max, TDI scores and cycle endurance time improved significantly more after IMT versus sham (mean between-group differences: 28 (95% CI 13-28) cmH2O, 3.0 (95% CI 0.9-5.1) points and 6.0 (95% CI 0.4-11.5) min, respectively). During exercise at iso-time, Pes, Pga and EMG of the scalene muscles were reduced and the oxygen saturation indices of the scalene and abdominal muscles were higher post- versus pre-training only in the IMT group (all p<0.05).

Conclusion

The effects of IMT on dyspnoea and exercise tolerance in UDD were not mediated by an improvement in isolated diaphragm function, but may reflect improvements in strength, coordination and/or oxygenation of the extra-diaphragmatic respiratory muscles.

Differential control of respiratory frequency and tidal volume during exercise

The lack of a testable model explaining how ventilation is regulated in different exercise conditions has been repeatedly acknowledged in the field of exercise physiology. Yet, this issue contrasts with the abundance of insightful findings produced over the last century and calls for the adoption of new integrative perspectives. In this review, we provide a methodological approach supporting the importance of producing a set of evidence by evaluating different studies together-especially those conducted in 'real' exercise conditions-instead of single studies separately. We show how the collective assessment of findings from three domains and three levels of observation support the development of a simple model of ventilatory control which proves to be effective in different exercise protocols, populations and experimental interventions. The main feature of the model is the differential control of respiratory frequency (f_R) and tidal volume (V_T); f_R is primarily modulated by central command (especially during high-intensity exercise) and muscle afferent feedback (especially during moderate exercise) whereas V_T by metabolic inputs. Furthermore, V_T appears to be fine-tuned based on f_R levels to match alveolar ventilation with metabolic requirements in different intensity domains, and even at a breath-by-breath level. This model reconciles the classical neuro-humoral theory with apparently contrasting findings by leveraging on the emerging control properties of the behavioural (i.e. f_R) and metabolic (i.e. V_T) components of minute ventilation. The integrative approach presented is expected to help in the design and interpretation of future studies on the control of f_R and V_T during exercise.

Inspiratory muscle training for recovered COVID-19 patients after weaning from mechanical ventilation: A pilot control clinical study

BACKGROUND

To the best of our knowledge, no studies have evaluated the effects of inspiratory muscle training (IMT) on recovered COVID-19 patients after weaning from mechanical ventilation. Therefore, this study assessed the efficacy of IMT on recovered COVID-19 patients following mechanical ventilation.

METHODS

Forty-two recovered COVID-19 patients (33 men and 9 women) weaned from mechanical ventilation with a mean age of 48.05 ± 8.85 years were enrolled in this pilot control clinical study. Twenty-one patients were equipped to 2-week IMT (IMT group) and 21 matched peers were recruited as a control (control group). Forced vital capacity (FVC%), forced expiratory volume in 1 second (FEV1%), dyspnea severity index (DSI), quality of life (QOL), and six-minute walk test (6-MWT) were assessed initially before starting the study intervention and immediately after intervention.

RESULTS

Significant interaction effects were observed in the IMT when compared to control group, FVC% (F = 5.31, P = .041, ηP2 = 0.13), FEV1% (F = 4.91, P = .043, ηP2 = 0.12), DSI (F = 4.56, P = .032, ηP2 = 0.15), QOL (F = 6.14, P = .021, ηP2 = 0.17), and 6-MWT (F = 9.34, P = .028, ηP2 = 0.16). Within-group analysis showed a significant improvement in the IMT group (FVC%, P = .047, FEV1%, P = .039, DSI, P = .001, QOL, P < .001, and 6-MWT, P < .001), whereas the control group displayed nonsignificant changes (P > .05).

CONCLUSIONS

A 2-week IMT improves pulmonary functions, dyspnea, functional performance, and QOL in recovered intensive care unit (ICU) COVID-19 patients after consecutive weaning from mechanical ventilation. IMT program should be encouraged in the COVID-19 management protocol, specifically with ICU patients.

Unilateral diaphragmatic paralysis: inspiratory muscles, breathlessness and exercise capacity

Background

Patients with unilateral diaphragmatic paralysis (UDP) may present with dyspnoea without specific cause and limited ability to exercise. We aimed to investigate the diaphragm contraction mechanisms and nondiaphragmatic inspiratory muscle activation during exercise in patients with UDP, compared with healthy individuals.

Methods

Pulmonary function, as well as volitional and nonvolitional inspiratory muscle strength were evaluated in 35 patients and in 20 healthy subjects. Respiratory pressures and electromyography of scalene and sternocleidomastoid muscles were continuously recorded during incremental maximal cardiopulmonary exercise testing until symptom limitation. Dyspnoea was assessed at rest, every 2 min during exercise and at the end of exercise with a modified Borg scale.

Main results

Inspiratory muscle strength measurements were significantly lower for patients in comparison to controls (all p<0.05). Patients achieved lower peak of exercise (lower oxygen consumption) compared to controls, with both gastric (−9.8±4.6 cmH₂O versus 8.9±6.0 cmH₂O) and transdiaphragmatic (6.5±5.5 cmH₂O versus 26.9±10.9 cmH₂O) pressures significantly lower, along with larger activation of both scalene (40±22% EMGmax versus 18±14% EMGmax) and sternocleidomastoid (34±22% EMGmax versus 14±8% EMGmax). In addition, the paralysis group presented significant differences in breathing pattern during exercise (lower tidal volume and higher respiratory rate) with more dyspnoea symptoms compared to the control group.

Conclusion

The paralysis group presented with exercise limitation accompanied by impairment in transdiaphragmatic pressure generation and larger accessory inspiratory muscles activation compared to controls, thereby contributing to a neuromechanical dissociation and increased dyspnoea perception.

The exercise capacity limitation in patients with unilateral diaphragmatic paralysis is characterised by an inefficient hemidiaphragm contraction. Consequently, there is a neuromechanical dissociation with an overload of inspiratory accessory muscles and higher breathlessness.https://bit.ly/2XxAR4K