Effect of training on inspiratory load compensation in weaned and unweaned mechanically ventilated ICU patients

Inspiratory Muscle Training While Hospitalized With Acute COVID-19 Respiratory Failure: A Randomized Controlled Trial

Although inspiratory muscle training (IMT) has been used in outpatient settings for patients who recovered from COVID-19 respiratory failure, little data exist to support earlier implementation in acute care hospitals. This study aimed to assess the safety and feasibility of IMT during the acute disease phase of COVID-19.

Design Setting and Patients

Sixty patients presenting with COVID-19 to a single academic medical center were randomized to control or intervention groups using systematic randomization.

Measurements

Participants in the control group had their maximal inspiratory pressure (MIP) measured at enrollment and hospital discharge. They were also asked for their rating of perceived exertion on the Revised Borg Scale for Grading Severity of Dyspnea and were scored by researchers on the Activity Measure for Post-Acute Care (AM-PAC) 6-Clicks Mobility Scale and the Intensive Care Unit Mobility Scale (IMS). Control group patients otherwise received standard care. Participants in the intervention group, in addition to the measures described previously, received inspiratory threshold trainers with the goal of doing 2 sessions daily with a physical therapist for the duration of their inpatient hospitalization. In these sessions, the patient completed 3 sets of 10 breaths with the trainer. Initial resistance was set at 30% of their MIP, with resistance increasing 1 level for the subsequent session if the patients rated their during-activity rating of perceived exertion as less than 2. Changes in functional outcome measures, amount of supplemental oxygen, hospital length of stay (LOS), discharge location, adverse events, and mortality were assessed in group comparisons.

Results

Of 60 enrolled patients, 41 (n = 19 in intervention and n = 22 in control) were included in the final data set, which required completion of the study, initial and discharge data points collected, and survival of hospitalization. Final groups were statistically similar. A total of 161 sessions of IMT were completed among the 19 patients in the intervention group. Mortality totaled 2 in the control group and 3 in the intervention group and adverse events during intervention occurred in only 3 (1.8%) sessions, all of which were minor oxygen desaturations. Sessions were unable to be completed for all potential reasons 11% of possible times. Dropout rate in the intervention group was 3 (10%). Both intervention and control groups demonstrated improved MIP, decreased supplemental oxygen requirements, improved function on the AM-PAC, and slightly decreased function on the IMS. Length of stay was shorter in the intervention group, and discharge disposition was similar between groups.

Conclusions

With a low number of recorded adverse events, similar mortality between groups, and successful completion of 161 exercise sessions, IMT may be a feasible and safe intervention for some hospitalized patients with COVID-19.

Respiratory Training and Plasticity After Cervical Spinal Cord Injury

While spinal cord injuries (SCIs) result in a vast array of functional deficits, many of which are life threatening, the majority of SCIs are anatomically incomplete. Spared neural pathways contribute to functional and anatomical neuroplasticity that can occur spontaneously, or can be harnessed using rehabilitative, electrophysiological, or pharmacological strategies. With a focus on respiratory networks that are affected by cervical level SCI, the present review summarizes how non-invasive respiratory treatments can be used to harness this neuroplastic potential and enhance long-term recovery. Specific attention is given to "respiratory training" strategies currently used clinically (e.g., strength training) and those being developed through pre-clinical and early clinical testing [e.g., intermittent chemical stimulation via altering inhaled oxygen (hypoxia) or carbon dioxide stimulation]. Consideration is also given to the effect of training on non-respiratory (e.g., locomotor) networks. This review highlights advances in this area of pre-clinical and translational research, with insight into future directions for enhancing plasticity and improving functional outcomes after SCI.

Temporary Transvenous Diaphragmatic Neurostimulation in Prolonged Mechanically Ventilated Patients: A Feasibility Trial (RESCUE 1)

Prolonged mechanical ventilation promotes diaphragmatic atrophy and weaning difficulty. The study uses a novel device containing a transvenous phrenic nerve stimulating catheter (Lungpacer IntraVenous Electrode Catheter) to stimulate the diaphragm in ventilated patients. We set out to determine the feasibility of temporary transvenous diaphragmatic neurostimulation using this device.

DESIGN

Multicenter, prospective open-label single group feasibility study.

SETTING

ICUs of tertiary care hospitals.

PATIENTS

Adults on mechanical ventilation for greater than or equal to 7 days that had failed two weaning trials.

INTERVENTIONS

Stimulation catheter insertion and transvenous diaphragmatic neurostimulation therapy up to tid, along with standard of care.

MEASUREMENTS AND MAIN RESULTS

Primary outcomes were successful insertion and removal of the catheter and safe application of transvenous diaphragmatic neurostimulation. Change in maximal inspiratory pressure and rapid shallow breathing index were also evaluated. Eleven patients met all entry criteria with a mean mechanical ventilation duration of 19.7 days; nine underwent successful catheter insertion. All nine had successful mapping of one or both phrenic nerves, demonstrated diaphragmatic contractions during therapy, and underwent successful catheter removal. Seven of nine met successful weaning criteria. Mean maximal inspiratory pressure increased by 105% in those successfully weaned (mean change 19.7 ± 17.9 cm H2O; p = 0.03), while mean rapid shallow breathing index improved by 44% (mean change -63.5 ± 64.4; p = 0.04).

CONCLUSIONS

The transvenous diaphragmatic neurostimulation system is a feasible and safe therapy to stimulate the phrenic nerves and induce diaphragmatic contractions. Randomized clinical trials are underway to compare it to standard-of-care therapy for mechanical ventilation weaning.

Dynamic respiratory muscle function in late-onset Pompe disease

Maximal inspiratory pressure (PI_MAX) reflects inspiratory weakness in late-onset Pompe disease (LOPD). However, static pressure tests may not reveal specific respiratory muscle adaptations to disruptions in breathing. We hypothesized that dynamic respiratory muscle functional tests reflect distinct ventilatory compensations in LOPD. We evaluated LOPD (n = 7) and healthy controls (CON, n = 7) during pulmonary function tests, inspiratory endurance testing, dynamic kinematic MRI of the thorax, and ventilatory adjustments to single-breath inspiratory loads (inspiratory load compensation, ILC). We observed significantly lower static and dynamic respiratory function in LOPD. PI_MAX, spirometry, endurance time, and maximal diaphragm descent were significantly correlated. During single-breath inspiratory loads, inspiratory time and airflow acceleration increased to preserve volume, and in LOPD, the response magnitudes correlated to maximal chest wall kinematics. The results indicate that changes in diaphragmatic motor function and strength among LOPD subjects could be detected through dynamic respiratory testing. We concluded that neuromuscular function significantly influenced breathing endurance, timing and loading compensations.

Inspiratory muscle conditioning exercise and diaphragm gene therapy in Pompe disease: Clinical evidence of respiratory plasticity

Pompe disease is an inherited disorder due to a mutation in the gene that encodes acid α-glucosidase (GAA). Children with infantile-onset Pompe disease develop progressive hypotonic weakness and cardiopulmonary insufficiency that may eventually require mechanical ventilation (MV). Our team conducted a first in human trial of diaphragmatic gene therapy (AAV1-CMV-GAA) to treat respiratory neural dysfunction in infantile-onset Pompe. Subjects (aged 2-15years, full-time MV: n=5, partial/no MV: n=4) underwent a period of preoperative inspiratory muscle conditioning exercise. The change in respiratory function after exercise alone was compared to the change in function after intramuscular delivery of AAV1-CMV-GAA to the diaphragm with continued exercise. Since AAV-mediated gene therapy can reach phrenic motoneurons via retrograde transduction, we hypothesized that AAV1-CMV-GAA would improve dynamic respiratory motor function to a greater degree than exercise alone. Dependent measures were maximal inspiratory pressure (MIP), respiratory responses to inspiratory threshold loads (load compensation: LC), and physical evidence of diaphragm activity (descent on MRI, EMG activity). Exercise alone did not change function. After AAV1-CMV-GAA, MIP was unchanged. Flow and volume LC responses increased after dosing (p<0.05 to p<0.005), but only in the subjects with partial/no MV use. Changes in LC tended to occur on or after 180days. At Day 180, the four subjects with MRI evidence of diaphragm descent had greater maximal voluntary ventilation (p<0.05) and tended to be younger, stronger, and use fewer hours of daily MV. In conclusion, combined AAV1-CMV-GAA and exercise training conferred benefits to dynamic motor function of the diaphragm. Children with a higher baseline neuromuscular function may have greater potential for functional gains.