Guillain-Barré syndrome (GBS) is a neurological disease characterized by an inflammation of peripheral nerves, which might be responsible for long-term disability.

Respiratory muscle weakness is a complication of GBS and might be responsible for respiratory symptoms, inadequate secretion clearance or hypoventilation, with negative impact on daily life.

Inspiratory muscle training has been applied in respiratory and neurological diseases and benefits have been observed in symptoms (e.g., dyspnoea), pulmonary function, exercise capacity and quality of life. Nevertheless, results of this intervention in people with GBS are yet unknown. Moreover, rehabilitation is a key player in the recovery of these highly complex patients, however, the interpretation of the magnitude of its effects has been limited by the absence of minimal clinically important differences for most outcome measures. To overcome these drawbacks, methodologically robust trials are needed to build evidence-based rehabilitation to improve clinical care on GBS.

The primary aim of this project (RehabGBs) is to develop an inspiratory muscle training protocol - InspireGBs and assess its effects on respiratory muscle strength, peak cough flow, pulmonary function, dyspnoea, fatigue, functional status and quality of life in people with GBS, through a randomised controlled trial. Secondary aims are to: i) establish minimal clinically important differences of Functional Assessment of Chronic Illness Therapy-Fatigue Subscale, Medical Research Council - Manual Muscle Testing, Vital capacity, Maximal Inspiratory Pressure, Peak Cough Flow, Functional Independence Measure and Quality of Life for inpatient rehabilitation programmes of people with GBS ii) Evaluate the prevalence of nocturnal hypoventilation in GBS.

Guillain-Barré syndrome (GBS) is an acute inflammatory demyelinating polyradiculoneuropathy and is the most common cause of acute flaccid paralysis. Its annual global incidence is between 0.8 - 1.9 cases per 100,000 people.

GBS is usually preceded by infection or other immune stimulation that induces an aberrant autoimmune response targeting peripheral nerves and their spinal roots. It is characterized by rapid progressive bilateral muscle weakness of the lower limbs and/or arms, in combination with hyporeflexia or areflexia, and most patients reach their maximum disability within 2-4 weeks.Various phenotypes have been described, including acute inflammatory demyelinating polyradiculoneuropathy, acute motor axonal neuropathy, acute motor sensory axonal neuropathy and Miller-Fisher syndrome.

Overall, the clinical course, severity and outcomes of people with GBS are highly heterogeneous. Significant disability, including incomplete recovery of motor (i.e., ambulation) and sensory function, as well as fatigue, pain, respiratory insufficiency and psychological distress might exist after the acute phase. But long-term significant impacts, two years after the onset, on daily activities, work, social activities and health-related quality of life have also been reported. The most often feature is an impairment of the motor capacity, but respiratory muscle weakness is a common complication in people with GBS and may result in decrease vital capacity, chest wall expansion and coughing strength, causing atelectasis and pulmonary infections. Therefore, it is generally accepted that respiratory muscle weakness causes increased morbidity and mortality, owing to the combination of poor airway protection, inadequate secretion clearance and hypoventilation. Previous studies already identified these clinical manifestations in acute GBS. However, prevalence of hypoventilation and inspiratory muscle weakness in subacute phase of GBS is still unknown. Early recognition and treatment of respiratory muscle weakness is important in people with GBS and physiotherapy interventions may be useful to successfully manage these patients.

Inspiratory muscle training (IMT) is a cheap and free of side-effects therapeutic modality, which consists of breathing exercises using a pressure threshold device, that has been applied in several diseases. In patients with chronic obstructive pulmonary disease, IMT improve inspiratory muscle function, exertional dyspnoea and exercise capacity. In patients with neuromuscular disease, has been suggested that IMT increases inspiratory muscle strength and lung volumes, especially in those with muscular dystrophies. In addition, a randomized control trial concluded that IMT in acute patients increases inspiratory muscle strength and quality of life. However, there are no studies about rehabilitation approaches, such IMT, to improve symptoms (i.e. dyspnoea or fatigue), pulmonary function, functional status and quality of life in people with GBS.

Rehabilitation, namely inpatient rehabilitation programmes, is therefore key for the recovery of symptoms, functional outcomes, community participation and quality of life of these highly complex patients. Nevertheless, insufficient high-quality literature, still precludes definitive conclusions about the effects of rehabilitation in people with GBS. Additionally, the interpretation of the magnitude of its effects is challenging due to the lack of minimal clinically important differences (MCIDs) for most outcome measures used in rehabilitation of people with GBS. A MCIDs is the smallest change in a measure that will be perceived as an important improvement for the patient. Such values constitute thresholds for clinical meaningfulness. Therefore, establishing MCIDs is essential to determine effectiveness of rehabilitation and guide clinical decision-making in the management of people with GBS.

In conclusion, by developing and implementing RehabGBs, we will contribute to build evidence-based rehabilitation practices and optimise care in GBS, by: i) assessing the effects of IMT in people with GBS; ii) establishing minimal clinical important differences of rehabilitation outcome measures, to help clinicians better understand the magnitude of the effects of the intervention and determine effectiveness of rehabilitation in people with GBS; iii) evaluate the prevalence of nocturnal hypoventilation in people with GBS.

Therefore, the primary aim of RehabGBs is to:

1. Evaluate, through a randomised controlled trial, the effects of InspireGBs - inspiratory muscle training protocol on respiratory muscle strength, peak cough flow, lung function, dyspnoea, fatigue, functional status and quality of life in people with GBS.

The secondary aims of the project are to:

1. Establish the MCIDs for rehabilitation programmes in people with GBS for Functional Assessment of Chronic Illness Therapy-Fatigue Subscale, Modified Borg Scale, Medical Research Council - Manual Muscle Testing, Vital capacity, Maximal Inspiratory pressure, Peak Cough Flow, Functional Independence Measure and EuroQol Five-Dimensional Questionnaire.
2. Evaluate the prevalence of nocturnal hypoventilation in people with sub-acute GBS.

Study Design & Intervention

InspireGBs is an inspiratory muscle training programme which will be implemented to people with GBS for 6 weeks during an inpatient rehabilitation programme. They will receive IMT for 5 days/week using the PowerBreath KH2. This handheld device applies a constant resistance provided by a electronic-controlled valve. Training will be set initially at a load of approximately 50% of patients' maximal inspiratory mouth pressure. This initial load will be daily increased during the programme based on symptom scores (modified Borg dyspnoea Scale ratings of 4-6 of 10).Total daily training time will consist of 6 cycles of 30 breaths (3 cycles, twice daily).

Patients will be recruited as described and randomly allocated by a computer-generated adaptive random allocation schedule (in a ratio 1:1) to either the experimental or control groups. All participants will receive the inpatient rehabilitation programme. This programme will be tailored to each patient, with approximately 5 hours of intervention/day for 5 days/week (typically for 14 weeks). An interdisciplinary team composed of physiotherapy; occupational therapy; speech and language therapy; and medical, pharmacological, nursery, psychology, clinical dietitian and social worker will be involved, as needed.

Sample Size Estimation

Based on an inspiratory muscle training study conducted in people with spinal cord injury, it is anticipated that a minimum of 64 participants (32 in each group) will be needed to detect a between-group difference of 10 cmH2O in the primary outcome measure (power=80%, α=0.05, 2-tailed). Since in GBS rehabilitation interventions dropout rates are around 15%, 74 participants will be needed.

Inclusion Criteria:

• ≥18 years
• diagnosed with Guillain Barré Syndrome
• willing to participate in an inpatient rehabilitation program
• able to provide informed consent

Exclusion Criteria:

• presence of significant cardiac and musculoskeletal diseases
• tracheostomized patients
• signs of cognitive impairment or current neoplastic or immunological disease which may preclude their participation in the rehabilitation program and participation in any other therapeutic intervention in addition to standard of care.

Single blind