Comparing two types of loading during inspiratory muscle training in patients with weaning difficulties: An exploratory study

BACKGROUND

Inspiratory muscle training improves respiratory muscle function and may improve weaning outcomes in patients with weaning difficulties. Compared to the commonly used pressure threshold loading, tapered flow resistive loading better accommodates pressure-volume relationships of the respiratory muscles, which might help to facilitate application of external loads and optimise training responses.

OBJECTIVE

The objective of this study was to compare acute breathing pattern responses and perceived symptoms during an inspiratory muscle training session performed against identical external loading provided as pressure threshold loading or as tapered flow resistive loading. We hypothesised that for a given loading, tapered flow resistive loading would allow larger volume expansion and higher inspiratory flow responses and consequently higher external work of breathing and power than pressure threshold loading and that subsequently patients perceived fewer symptoms during tapered flow resistive loading than during pressure threshold loading.

METHODS

In this exploratory study, 21 patients (maximal inspiratory pressure: 35 ± 14 cmH₂O and vital capacity:0.85 L±0.37 L) performed two training sessions against external loads equalling 42 ± 15% of maximal inspiratory pressure provided either as pressure threshold loading or as tapered flow resistive loading. During these training sessions, breath-by-breath data of breathing parameters were collected, and patients rated their perceived breathing effort, dyspnoea, and unpleasantness.

RESULTS

Compared to pressure threshold loading, tapered flow resistive loading allowed significantly larger volume expansion (0.53 ± 0.28 L versus 0.41 ± 0.20 L, p < 0.01) and inspiratory flow responses (0.43 ± 0.20 L/s versus 0.33 ± 0.16 L/s, p = 0.01). Tapered flow resistive loading was perceived as less unpleasant (3.1 ± 1.9 versus 3.8 ± 2.4, p = 0.048). No significant differences in breathing effort, dyspnoea, work of breathing, and power were observed.

CONCLUSIONS

For a given loading, inspiratory muscle training with tapered flow resistive loading allowed larger volume expansion and higher inspiratory flow responses than pressure threshold loading, which led patients to perceive tapered flow resistive loading as less unpleasant. This might help us to facilitate early implementation of inspiratory muscle training in patients with weaning difficulties.

CLINICAL TRIAL REGISTRATION NUMBER

Clinicaltrials.gov identifier: NCT03240263.

High-Intensity Inspiratory Muscle Training Improves Scalene and Sternocleidomastoid Muscle Oxygenation Parameters in Patients With Weaning Difficulties: A Randomized Controlled Trial

Background

Critically ill patients who have difficulties weaning from the mechanical ventilator are prone to develop respiratory muscle weakness. Inspiratory muscle training (IMT) can improve respiratory muscle strength. Whether IMT can improve scalene and sternocleidomastoid muscle oxygenation parameters is unknown.

Aim

To compare changes in muscle oxygenation parameters of scalene and sternocleidomastoid inspiratory muscles during a standardized task between patients with weaning difficulties who received either high-intensity IMT (intervention) or sham low-intensity IMT (control).

Method

Forty-one patients performed daily IMT sessions (4 sets, 6–10 breaths) until weaning success or for 28 consecutive days. The training load was progressively adjusted in the intervention group (n = 22) to the highest tolerable load, whilst the control group (n = 19) kept training at 10% of their baseline maximal inspiratory pressure (PImax). Breathing characteristics (i.e., work and power of breathing, PoB), respiratory muscle function [i.e., PImax and forced vital capacity (FVC)] were measured during a standardized loaded breathing task against a load of 30% of baseline PImax before and after the IMT period. In addition, during the same loaded breathing task, absolute mean and nadir changes from baseline in local scalene and sternocleidomastoid muscle oxygen saturation index (Δ%StiO2) (an index of oxygen extraction) and nadir Δ%StiO2 normalized for the PoB were measured by near-infrared spectroscopy.

Results

At post measures, only the intervention group improved mean PoB compared to pre measures (Pre: 0.42 ± 0.33 watts, Post: 0.63 ± 0.51watts, p-value &lt; 0.01). At post measures, both groups significantly improved nadir scalene muscles StiO2% normalized for the mean PoB (ΔStiOnadir%/watt) compared to pre measurements and the improvement was not significant different between groups (p-value = 0.40). However, at post measures, nadir sternocleidomastoid muscle StiO2% normalized for the mean PoB (ΔStiOnadir%/watt) was significantly greater improved in the intervention group (mean difference: +18.4, 95%CI: −1.4; 38.1) compared to the control group (mean difference: +3.7, 95%CI: −18.7; 26.0, between group p-value &lt; 0.01). Both groups significantly improved PImax (Intervention: +15 ± 13 cmH2O p-value &lt; 0.01, Control: +13 ± 15 cmH2O p-value &lt; 0.01). FVC only significantly improved in the intervention group (+0.33 ± 0.31 L p &lt; 0.01) report also change in control group.

Conclusion

This exploratory study suggests that high-intensity IMT induces greater improvements in scalene and sternocleidomastoid muscle oxygenation parameters attributed for oxygen delivery, utilization and oxygen saturation index compared to low-intensity IMT in patients with weaning difficulties.

Measurement validity of an electronic training device to assess breathing characteristics during inspiratory muscle training in patients with weaning difficulties

Inspiratory muscle training (IMT) improves respiratory muscle function and might enhance weaning outcomes in patients with weaning difficulties. An electronic inspiratory loading device provides valid, automatically processed information on breathing characteristics during IMT sessions. Adherence to and quality of IMT, as reflected by work of breathing and power generated by inspiratory muscles, are related to improvements in inspiratory muscle function in patients with chronic obstructive pulmonary disease. The aim of this study was to investigate the validity of an electronic training device to assess and provide real-time feedback on breathing characteristics during inspiratory muscle training (IMT) in patient with weaning difficulties. Patients with weaning difficulties performed daily IMT sessions against a tapered flow-resistive load of approximately 30 to 50% of the patient’s maximal inspiratory pressure. Airflow and airway pressure measurements were simultaneously collected with the training device (POWERbreatheKH2, POWERbreathe International Ltd, UK) and a portable spirometer (reference device, Pocket-Spiro USB/BT100, M.E.C, Belgium). Breath by breath analysis of 1002 breaths of 27 training sessions (n = 13) against a mean load of 46±16% of the patient’s maximal inspiratory pressure were performed. Good to excellent agreement (Intraclass correlation coefficients: 0.73–0.97) was observed for all breathing characteristics. When individual differences were plotted against mean values of breaths recorded by both devices, small average biases were observed for all breathing characteristics. To conclude, the training device provides valid assessments of breathing characteristics to quantify inspiratory muscle effort (e.g. work of breathing and peak power) during IMT in patients with weaning difficulties. Availability of valid real-time data of breathing responses provided to both the physical therapist and the patient, can be clinically usefull to optimize the training stimulus. By adapting the external load based on the visual feedback of the training device, respiratory muscle work and power generation during IMT can be maximized during the training.

Early neuromuscular electrical stimulation reduces the loss of muscle mass in critically ill patients - A within subject randomized controlled trial

PURPOSE

To investigate the effect of Neuromuscular Electrical Stimulation (NMES) on muscle thickness, strength and morphological and molecular markers of the quadriceps.

MATERIALS AND METHODS

Adult critically ill patients with an expected prolonged stay received unilateral quadriceps NMES sessions for 7 consecutive days. Before and after the intervention period, quadriceps thickness was measured with ultrasound. After the intervention period, strength was assessed in cooperative patients and muscle biopsies were taken. Multivariable regression was performed to identify factors affecting muscle thickness loss.

RESULTS

Muscle thickness decreased less in the stimulated leg (-6 ± 16% versus -12 ± 15%, p = 0.014, n = 47). Strength was comparable. Opioid administration, minimal muscle contraction and more muscle thickness loss in the non-stimulated muscle were independently associated with better muscle thickness preservation. Stimulated muscles showed a shift towards larger myofibers and higher MyHC-I gene expression. NMES did not affect gene expression of other myofibrillary proteins, MuRF-1 or atrogin-1. Signs of myofiber necrosis and inflammation were comparable for both muscles.

CONCLUSIONS

NMES attenuated the loss of muscle mass, but not of strength, in critically ill patients. Preservation of muscle mass was more likely in patients receiving opioids, patients with a minimal muscle contraction during NMES and patients more prone to lose muscle mass.

TRIAL REGISTRATION

clinicaltrials.govNCT02133300.

Early mobilization in clinical practice: the reliability and feasibility of the 'Start To Move' Protocol

PURPOSE

The properties of a local Intensive Care Unit early mobilization protocol ('Start To Move As Soon As Possible') in critically ill patients, consisting of an objective diagnostic assessment linked to six treatment levels were evaluated. This study aimed to investigate whether the protocol can be reliably applied by different health-care providers (reliability), to examine the associations between prescribed and delivered treatments (feasibility) and to explore safety and patient satisfaction with the protocol.

METHODS

Cross-sectional observational study evaluating the reliability of the protocol between physiotherapist was evaluated with Cohen's kappa, percentage of agreement, and intraclass correlation coefficients in 61 patients. Feasibility was analyzed as agreement between prescribed and delivered treatments with Spearman's rank correlation coefficients in 60 patients. A satisfaction survey was used to evaluate patient satisfaction with the protocol.

RESULTS

Excellent agreement was observed between physiotherapists for diagnostic level assignment (Kappa = 0.92), while the majority of the treatment proposals per level showed moderate to substantial agreement between the physiotherapists (Kappa range: 0.40-0.89). Three hundred and thirteen treatments were prescribed. Perfect agreement was observed between prescribed and delivered treatments in level 0 (Spearman's rho 1.00) and excellent associations for levels 1-5 (0.941, 0.995, 0.951, 0.998, and 0.999), respectively. Unwanted safety events rate was 3%. Most patients (92%) were very satisfied with physiotherapy.

CONCLUSION

Excellent inter-rater agreement for diagnostic level assignment and moderate to substantial agreement for proposed treatments support the reliability of the protocol. Perfect to excellent associations between prescribed and delivered treatments supports its feasibility. Complications were rare, and most patients were very positive regarding the care provided by physiotherapists during their stay in the ICU.

Can inspiratory muscle training improve weaning outcomes in difficult to wean patients? A protocol for a randomised controlled trial (IMweanT study)

INTRODUCTION

Respiratory muscle dysfunction has been associated with failure to wean from mechanical ventilation. It has therefore been hypothesised that these patients might benefit from inspiratory muscle training (IMT). Evidence, however, is thus far limited to data from small, single-centre studies with heterogeneity in inclusion criteria, training modalities and outcomes. The aim of this study is to evaluate the effects of a novel IMT method on weaning outcomes in selected patients with weaning difficulties.

METHODS

This study is designed as a double-blind, parallel-group, randomised controlled superiority trial with 1:1 allocation ratio. Patients with weaning difficulties will be randomly allocated into either an IMT group (intervention) or a sham-IMT group (control). Ninetypatients (45 in each group) will be needed to detect a 28% difference in the proportion of weaning success between groups (estimated difference in primary outcome based on previous studies) with a risk for type I error (α) of 5% and statistical power (1-β) of 80%. Patients will perform four sets of 6-10 breaths daily against an external load using a tapered flow resistive loading device (POWERbreathe KH2, HaB International, UK). Training intensity in the intervention group will be adjusted to the highest tolerable load. The control group will train against a low resistance that will not be modified during the training period. Training will becontinued until patients are successfully weaned or for a maximum duration of 28 days. Pulmonary and respiratory muscle function, weaning duration, duration of mechanical ventilation, ventilator-free days and length of stay in the intensive care unit will be evaluated as secondary outcomes. Χ2 tests and analysis of covariance with adjustments for baseline values of respective outcomesas covariates will be used to compare results after the intervention period between groups.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the local ethical committee (Ethische Commissie Onderzoek UZ/KU Leuven protocol ID: S60516). Results from this randomised controlled trial will be presented at scientific meetings as abstracts for poster or oral presentations and published in peerreviewed journals.

TRIAL STATUS

Enrolment into the study have started in August 2017. Data collection and data analysis are expected to be completed in September 2021.

TRIAL REGISTRATION NUMBER

NCT03240263.

Predictive value for weakness and 1-year mortality of screening electrophysiology tests in the ICU

PURPOSE

Muscle weakness in long-stay ICU patients contributes to 1-year mortality. Whether electrophysiological screening is an alternative diagnostic tool in unconscious/uncooperative patients remains unknown. We aimed to determine the diagnostic properties of abnormal compound muscle action potential (CMAP), sensory nerve action potential (SNAP), and spontaneous electrical activity (SEA) for Medical Research Council (MRC)-defined weakness and their predictive value for 1-year mortality.

METHODS

Data were prospectively collected during the EPaNIC trial (ClinicalTrials.gov: NCT00512122). First, sensitivity, specificity, positive (PPV) and negative predictive values (NPV) of abnormal CMAP, SNAP, and SEA for weakness were determined. Subsequently, association between 1-year mortality and abnormal findings on electrophysiological screening was assessed by univariate and multivariate analyses correcting for weakness and other risk factors and the prediction model involved only a development phase.

RESULTS

A total of 730 patients were electrophysiologically screened of whom 432 were tested for weakness. On day 8, normal CMAP excluded weakness with a high NPV (80.5 %). By day 15, abnormal SNAP and the presence of SEA had a high PPV (91.7 and 80.0 %, respectively). Only a reduced CMAP on day 8 was associated with higher 1-year mortality [35.6 vs 15.2 % (p < 0.001)]. This association remained significant after correction for weakness and other risk factors [OR 2.463 (95 % CI 1.113-5.452), p = 0.026]. Also among conscious/cooperative patients without weakness, reduced CMAP was independently associated with a higher likelihood of death occurring during 1 year [HR 2.818 (95 % CI 1.074-7.391), p = 0.035].

CONCLUSIONS

The diagnostic properties of electrophysiological screening vary over time. Abnormal CMAP documented early during critical illness carries information about longer-term outcome, which should be further investigated mechanistically.