Waves of Precision: A Practical Guide for Reviewing New Tools to Evaluate Mechanical In-Exsufflation Efficacy in Neuromuscular Disorders

Mechanical insufflation-exsufflation (MI-E) is essential for secretion clearance, especially in neuromuscular disorders. For the best outcomes, initiation of MI-E should be started at the correct time with regular evaluation to the response to treatment. Typically, cough peak flow has been used to evaluate cough effectiveness with and without MI-E. This review highlights the limitations of this and discussed other tools to evaluate MI-E efficacy in this rapidly developing field. Such tools include the interpretation of parameters (like pressure, flow and volumes) that derive from the MI-E device and external methods to evaluate upper airway closure. In this review we pinpoint the differences between different devices in the market and discuss new tools to better titrate MI-E and detect pathological responses of the upper airway. We discuss the importance of point of care ultrasound (POCUS), transnasal fiberoptic laryngoscopy and wave form analysis in this setting. To improve clinical practice newer generation MI-E devices should allow real-time evaluation of waveforms and standardize some of the derived parameters.

Cut-Off Value of Voluntary Peak Cough Flow in Patients with Parkinson's Disease and Its Association with Severe Dysphagia: A Retrospective Pilot Study

Background and Objectives. Swallowing and coughing reflexes are both closely associated with airway protection. Peak cough flow (PCF) is associated with dysphagia in several neurogenic diseases. In this study, we aimed to analyze the relationship between PCF and aspiration in Parkinson's disease (PD) and determine the cut-off value of PCF. Materials and Methods. We retrospectively analyzed the records of patients with PD who underwent a videofluoroscopic swallowing study and checked for PCF. A total of 219 patients were divided into an aspiration group (n = 125) and a non-aspiration group (n = 94). Results. Significantly lower PCF values were observed in the aspiration group compared to the non-aspiration group (132.63 ± 83.62 vs. 181.38 ± 103.92 L/min, p < 0.001). Receiver operating characteristic curve analysis revealed that a PCF cut-off value of 153 L/min (area under the receiver operating characteristic curve, 0.648; sensitivity, 73.06%; specificity, 51.06%) was associated with aspiration in PD. Additionally, a univariate analysis showed that the male sex, lower body mass indexes, higher Hoehn and Yahr scales, and PCF values of ≤153 L/min indicated an increased risk of aspiration. Conclusions. Through a multivariate analysis, we demonstrated that a PCF value ≤153 L/min was associated with an increased risk of aspiration (odds ratio 3.648; 1.797-7.407), highlighting that a low PCF is a risk factor for aspiration in patients with PD.

Assessing the effect of transcranial magnetic stimulation on peak cough flow in patients with supratentorial cerebral infarction: A retrospective cohort study

Respiratory dysfunction following supratentorial cerebral infarction leads to pneumonia and is a major cause of mortality. Decreased voluntary cough function impairs the ability to clear mucus or secretions from the airways and increases the risk of aspiration pneumonia. Peak cough flow (PCF) is one of the objective tools for evaluating voluntary cough function. Repetitive transcranial magnetic stimulation (rTMS) could be applied to the respiratory motor cortex to improve respiratory function. Little is known about the effect of rTMS on PCF in patients with supratentorial cerebral infarction during the subacute period. This study aimed to determine whether rTMS treatment could improve PCF in patients with supratentorial cerebral infarction. We retrospectively recruited patients with subacute supratentorial cerebral infarction who underwent a PCF test. The rTMS group received a combination of rTMS treatment for 2 weeks and conventional rehabilitation for 4 weeks. However, the control group underwent only conventional rehabilitation for 4 weeks. PCF tests were performed before and after treatment and the results were compared between the 2 groups. In total, 145 patients with supratentorial cerebral infarctions were recruited. The PCF parameters before and after treatment increased in both the rTMS and control groups. However, the rTMS group showed a greater increase in PCF values compared with the control group. In patients with supratentorial cerebral infarction, the combination of conventional rehabilitation and rTMS in the subacute period may be helpful in improving voluntary cough function compared with conventional rehabilitation alone.

Pulmonary function tests for evaluating the severity of Duchenne muscular dystrophy disease

AIM

In Duchenne muscular dystrophy (DMD), lung disease contributes significantly to morbidity and mortality. This study aimed to assess the usefulness of various pulmonary function tests in evaluating DMD severity.

METHODS

This retrospective study analysed lung function tests of patients with DMD-treated in the multidisciplinary respiratory neuromuscular clinic at Schneiders' Children Medical Center of Israel. Data were analysed according to age, ambulatory status and glucocorticoid treatment.

RESULTS

Among 90 patients with DMD, 40/63 (63.5%) ambulatory patients and 22/27 (81.5%) nonambulatory patients successfully performed spirometry. Significant annual declines were demonstrated among nonambulatory patients, in percentile predicted forced vital capacity (3.8%) and in total lung capacity (5.5%) per year. The decline correlated with age and loss of ambulation but not with steroid treatment. Peak cough flow values were randomly distributed and did not correlate with age, ambulation or treatment. In nonambulatory patients, transcutaneous carbon dioxide measurement correlated significantly with age (r = 0.55, p = 0.02).

CONCLUSION

Forced vital capacity, total lung capacity and transcutaneous carbon dioxide correlated with the clinical severity of disease in children with DMD. These measures may be useful in follow-up and clinical trials. A comparable correlation was not found for peak cough flow.

Prestroke VO2max by the Jurca prediction index as a predictor of functional outcomes in stroke patients

BACKGROUND

Prestroke cardiopulmonary fitness (CPF) levels can affect post-stroke respiratory function and functional status, including gait and activities of daily living (ADL).

OBJECTIVES

To investigate the prestroke CPF level measured by the Jurca prediction index as a predictor of functional outcomes after stroke and to evaluate the association between estimated prestroke CPF and respiratory function after stroke.

METHODS

This was a prospective observational study involving 71 inpatients with first-time subacute stroke between June 2017 and July 2019. The prestroke VO₂max was assessed using the Jurca prediction index, which was calculated from age, sex, resting heart rate, body mass index, and physical activity level. Linear regression analysis was performed to determine the relationship between the Jurca prediction index, functional outcomes, pulmonary functions, and cough strength variables.

RESULTS

The estimated prestroke VO₂max was significantly associated with the post-stroke Berg Balance Scale (β=1.199, P<0.001), Trunk Impairment Scale (β=0.308, P=0.006), and Functional Independence Measure score (β=1.102, P=0.004) at admission, and these relationships remained significant at the follow-up evaluation after 1 month of conventional rehabilitation (P<0.001). Among the respiratory function variables, only peak cough flow (PCF) (β=0.696, P=0.037) was significantly associated with the estimated prestroke VO₂max.

CONCLUSIONS

Prestroke CPF likely affects the stability of core muscles that are related to PCF and the functional status, including balance function and ADL after stroke. Regular exercise to increase the CPF level should be encouraged in patients with risk factors for stroke, not only for primary prevention but also for functional improvement after stroke.

Respiratory measurements and airway clearance device prescription over one year in amyotrophic lateral sclerosis

Objective: The rates of decline in respiratory measurements, including Peak Cough Flow (PCF) have not been established in Amyotrophic Lateral Sclerosis (ALS). Additionally, optimal prescription of cough adjuncts which aim to increase cough strength are unknown. The primary aim of this study was to quantify declines in respiratory function in ALS using PCF, Sniff Nasal Inspiratory Pressure (SNIP) and Slow Vital Capacity (SVC). Secondary aims were to measure respiratory morbidity, audit the characteristics of those prescribed cough adjuncts, and compare outcomes between treated and untreated cohorts. Methods: A prospective, longitudinal, observational, cohort study evaluated respiratory measures, morbidity, and physical function in ALS patients at three monthly intervals, over one year. Patient and disease characteristics of those prescribed cough adjuncts were profiled at the time of device prescription. Results: one hundred and eight participants with mean age 62.1 ± 11.5 years participated. PCF declined rapidly at a rate of 124.8L/min/year (p < 0.001). SNIP, SVC (%predicted), and ALSFRS-R also declined significantly at rates of 18.72cmH₂O, 17.49%, and 9.62 units per year respectively (p < 0.001). Thirty-two (29.6%) patients reported 56 incidences of chest infection and 21 died. Patients prescribed a cough adjunct (44.4%) had significantly lower average PCF, SNIP, SVC percent predicted, and ALSFRS-R (p < 0.001). Conclusions: This study identified a rapid rate of decline in PCF, a similar decline in SNIP, and slower declines in SVC and ALSFRS-R. Cough adjunct prescription was triggered by declining respiratory measures and recommended PCF thresholds, but also by respiratory symptoms. Chest infections were common in patients regardless of cough adjunct prescription and should be closely monitored.

The utility of using peak expiratory flow and forced vital capacity to predict poor expiratory cough flow in children with neuromuscular disorders

Background

Approximately one in every 1200 South Africans is affected by a neuromuscular disease (NMD). Weak respiratory muscles and ineffective cough contribute to the development of respiratory morbidity and mortality. Early identification of individuals at risk of respiratory complications, through peak expiratory cough flow (PCF) measurement, may improve patient outcomes through timely initiation of cough augmentation therapy.

Objectives

The aim of this study was to investigate the relationship between peak expiratory flow (PEF), forced vital capacity (FVC) and PCF in South African children with neuromuscular disorders.

Methods

A retrospective descriptive study of routinely collected data was conducted.

Results

Forty-one participants (aged 11.5 ± 3.6 years; 75.6% male) were included. There was a strong linear correlation between PCF and PEF (R = 0.78; p = 0.0001) and between PCF and FVC (R = 0.61; p = 0.0001). There was good agreement between PCF and PEF, with intraclass correlation coefficient of 0.8 (95% confidence interval, 0.7–0.9; p < 0.0001). Peak expiratory flow < 160 L.min⁻¹ and FVC < 1.2 L were significantly predictive of PCF < 160 L.min⁻¹ (suggestive of cough ineffectiveness), whilst PEF < 250 L.min⁻¹ was predictive of PCF < 270 L.min⁻¹, the level at which cough assistance is usually implemented.

Conclusion

PEF and FVC may be surrogate measures of cough effectiveness in children with neuromuscular disorders.

Clinical implications

PEF and FVC may be considered for clinical use as screening tools to identify patients at risk for pulmonary morbidity related to ineffective cough.

Respiratory Diagnostic Tools in Neuromuscular Disease

Children with neuromuscular disease (NMD) are at risk of acquiring respiratory complications. Both clinical assessments and respiratory diagnostic tests are important to optimize the respiratory health and care of such children. The following respiratory diagnostic tools and their utility for evaluating children with NMD are discussed in this article: lung function testing (spirometry and lung volumes), peak cough flow (PCF), respiratory muscle strength testing, oximetry, capnography, and polysomnography.

A Comparison of Cough Assistance Techniques in Patients with Respiratory Muscle Weakness

PURPOSE

To assess the ability of a mechanical in-exsufflator (MI-E), either alone or in combination with manual thrust, to augment cough in patients with neuromuscular disease (NMD) and respiratory muscle dysfunction.

MATERIALS AND METHODS

For this randomized crossover single-center controlled trial, patients with noninvasive ventilator-dependent NMD were recruited. The primary outcome was peak cough flow (PCF), which was measured in each patient after a cough that was unassisted, manually assisted following a maximum insufflation capacity (MIC) maneuver, assisted by MI-E, or assisted by manual thrust plus MI-E. The cough augmentation techniques were provided in random order. PCF was measured using a new device, the Cough Aid.

RESULTS

All 40 enrolled participants (37 males, three females; average age, 20.9±7.2 years) completed the study. The mean (standard deviation) PCFs in the unassisted, manually assisted following an MIC maneuver, MI-E-assisted, and manual thrust plus MI-E-assisted conditions were 95.7 (40.5), 155.9 (53.1), 177.2 (33.9), and 202.4 (46.6) L/min, respectively. All three interventions significantly improved PCF. However, manual assistance following an MIC maneuver was significantly less effective than MI-E alone. Manual thrust plus MI-E was significantly more effective than both of these interventions.

CONCLUSION

In patients with NMD and respiratory muscle dysfunction, MI-E alone was more effective than manual assistance following an MIC maneuver. However, MI-E used in conjunction with manual thrust improved PCF even further.

Relation between hand grip strength, respiratory muscle strength and spirometric measures in male nursing home residents

Adverse-outcomes related to sarcopenia are mostly mentioned as physical disability. As the other skeletal muscles, respiratory muscles may also be affected by sarcopenia. Respiratory muscle strength is known to affect pulmonary functions. Therefore, we aimed to investigate the relations between extremity muscle strength, respiratory muscle strengths and spirometric measures in a group of male nursing home residents. Among a total of 104 male residents, residents with obstructive measures were excluded and final study population was composed of 62 residents. Mean age was 70.5 ± 6.7 years, body mass index: 27.7 ± 5.3 kg/m2 and dominant hand grip strength: 29.7 ± 6.5 kg. Hand grip strength was positively correlated with maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) (r = 0.35, p < 0.01 and r = 0.26, p < 0.05, respectively). In regression analysis, the only factor related to MIP was hand grip strength; among spirometric measures only parameter significantly related to grip strength was peak cough flow (PCF). The association of PCF with grip strength disappeared when MIP alone or "MIP and MEP" were included in the regression analysis. In the latter case, PCF was significantly associated only with MIP. We found peripheric muscle strength be associated with MIP and PCF but not with MEP or any other spirometric parameters. The relation between peripheral muscle strength and PCF was mediated by MIP. Our findings suggest that sarcopenia may affect inspiratory muscle strength earlier or more than the expiratory muscle strength. Sarcopenia may cause decrease in PCF in the elderly, which may stand for some common adverse respiratory complications.

Respiratory muscle strength and cough capacity in patients with Duchenne muscular dystrophy

The function of inspiratory muscles is crucial for effective cough as well as expiratory muscles in patients with Duchenne muscular dystrophy (DMD). However, there is no report on the correlation between cough and inspiratory muscle strength. To investigate the relationships of voluntary cough capacity, assisted cough techniques, and inspiratory muscle strength as well as expiratory muscle strength in patients with DMD (n= 32). The vital capacity (VC), maximum insufflation capacity (MIC), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) were measured. Unassisted peak cough flow (UPCF) and three different techniques of assisted PCF were evaluated. The mean value of MICs (1918 +/- 586 mL) was higher than that of VCs (1474 +/- 632 mL) (p < 0.001). All three assisted cough methods showed significantly higher value than unassisted method (212 +/- 52 L/min) (F = 66.13, p < 0.001). Combined assisted cough technique (both manual and volume assisted PCF; 286 +/- 41 L/min) significantly exceeded manual assisted PCF (MPCF; 246 +/- 49 L/ min) and volume assisted PCF (VPCF; 252 +/- 45 L/min) (F = 66.13, p < 0.001). MIP (34 +/- 13 cmH2O) correlated significantly with both UPCF and all three assisted PCFs as well as MEP (27 +/- 10 cmH2O) (p < 0.001). Both MEP and MIP, which are the markers of respiratory muscle weakness, should be taken into account in the study of cough effectiveness.

Assisted cough and pulmonary compliance in patients with Duchenne muscular dystrophy

The aim of this study was to investigate the factors affecting cough ability, and to compare the assisted cough methods in patients with Duchenne muscular dystrophy (DMD). A total seventy-one male patients with DMD were included in the study. The vital capacity (VC) and maximum insufflation capacity (MIC) were measured. The unassisted peak cough flow (UPCF) and three different techniques of assisted peak cough flow were evaluated. UPCF measurements were possible for all 71 subjects. But when performing the three different assisted cough techniques, peak cough flows (PCFs) could be obtained from only 51 subjects. The mean value of MICs (1801 +/- 780 cc) was higher than that of VCs (1502 +/- 765 cc) (p< 0.01). All three assisted cough methods showed a significantly higher value than the unassisted method (F=80.92, p< 0.01). The manual assisted PCF under MIC (MPCFmic) significantly exceeded those produced by manual assisted PCF (MPCF) or PCF under MIC (PCFmic). The positive correlation between the MIC, VC difference (MIC-VC), and the difference between PCFmic and UPCF (PCFmic-UPCF) was seen (r=0.572, p< 0.01). The preservation of pulmonary compliance is important for the development of an effective cough as well as assisting the compression and expulsive phases. Thus, the clinical importance of the inspiratory phase and pulmonary compliance in assisting a cough should be emphasized.