Practical respiratory management in amyotrophic lateral sclerosis: evidence, controversies and recent advances

Setting Mechanical Insufflation-Exsufflation (MI-E) Pressures for Amyotrophic Lateral Sclerosis (ALS) Patients to Improve Atelectasis and Reduce Risk of Pneumothorax: A Case Report

Mechanical insufflation-exsufflation (MI-E) has been used to supplement the ability to cough and expel pulmonary secretions in patients with neuromuscular disease who have a reduced ability to cough. The manufacturer's guidelines for MI-E recommend a setting of inspiratory pressure of +40 cmH₂O and expiratory pressure of -40 cmH₂O. However, patients with small stature and restricted ventilatory impairment are prone to pneumothorax, so the manufacturer's recommendations are not used as is, and should be adjusted for the physical and pulmonary characteristics of each patient. Here, we report a case in which MI-E was used for an amyotrophic lateral sclerosis (ALS) patient with short height, low BMI, and restricted lung capacity at inspiratory and expiratory pressures lower than the manufacturer's recommendations. In adjusting MI-E pressure, physical observations such as chest auscultation, visual chest dilation, and observation of secretion movement toward the tracheal tube were performed to avoid unnecessary pressure. As a result, the pressure level set was lower than the manufacturer's recommendation (25 cmH₂O) but sufficient to improve atelectasis and no pneumothorax occurred. The method we practiced in this study is feasible in any clinical setting. We also believe that MI-E, when performed in conjunction with treatment response observation, can be expected to improve at lower pressures than generally recommended, thereby reducing the risk of lung injury and providing safer treatment.

Lung volume recruitment improves volitional airway clearance in amyotrophic lateral sclerosis

Introduction/Aims

In this study we evaluated the effects of lung volume recruitment treatment (LVR), a low‐tech, low‐cost, manual “breath‐stacking” technique used to help people cough with enough force to clear their airways, thereby reducing the risk of aspiration and choking, on five volitional airway clearance and protection behaviors used by people living with amyotrophic lateral sclerosis (PwALS).

Methods

Using a repeated‐measures cross‐over design, 29 PwALS performed five volitional airway clearance and protection behaviors in LVR treatment and in no‐treatment, control conditions. Peak cough flow (PCF) was used to measure maximum expiratory rate during forced expiration, throat clearing, hawking, post‐swallow coughing, and the supraglottic swallowing maneuver. Comparisons were made as a function of condition (treatment or control) and three time‐points (pretreatment, and 15 and 30 minutes posttreatment).

Results

LVR treatment had a significant positive effect on maximum expiratory rates during all tested airway clearance and protection behaviors. Increased PCF values lasted for up to 30 minutes post‐LVR for all tested behaviors in the treatment condition.

Discussion

We found that LVR treatment could increase control over airway clearance in PwALS, as well as provide improved airway protection for up to 30 minutes, the duration of a typical meal. This study has implications for patient care. These include offering patients control over some of the most feared symptoms of ALS, particularly choking during activities of daily living, and enhanced ALS respiratory care in low‐resource settings. Findings may have implications for other neurodegenerative disorders in which dysphagia occurs with retained sensory function.

Effects of expiratory muscle activation via high-frequency spinal cord stimulation

In persons with spinal cord injury, lower thoracic low-frequency spinal cord stimulation (LF-SCS; 50 Hz, 15 mA) is a useful method to restore an effective cough. Unfortunately, the high-stimulus-amplitude requirements and potential activation of pain fibers significantly limit this application in persons with intact sensation. In this study, the mechanism of the expiratory muscle activation, via high-frequency SCS (HF-SCS; 500 Hz, 1 mA) was evaluated in dogs. In group 1, the effects of electrode placement on airway pressure generation (P) was evaluated. Maximal P occurred at the T9-T10 level with progressive decrements in P at more rostral and caudal levels for both LF-SCS and HF-SCS. In group 2, electromyographic (EMG) latencies of internal intercostal muscle (II) activation were evaluated before and after spinal root section and during direct motor root stimulation. Onset time of II EMG activity during HF-SCS was significantly longer (3.84 ± 1.16 ms) than obtained during direct motor root activation (1.61 ± 0.10 ms). In group 3, P and external oblique (EO) EMG activity, before and after sequential spinal section at the T11-T12 level, were evaluated. Bilateral dorsal column section significantly reduced EO EMG activity below the section and resulted in a substantial fall in P. Subsequent lateral funiculi section completely abolished those activities and resulted in further reductions in P. We conclude that 1) activation of the expiratory muscles via HF-SCS is dependent entirely on synaptic spinal cord pathways, and 2) HF-SCS at the T9 level produces a comparable level of muscle activation with that achieved with LF-SCS but with much lower stimulus amplitudes. NEW & NOTEWORTHY The findings in the present study suggest that lower thoracic high-frequency spinal cord stimulation with low stimulus currents results in sufficient activation of the expiratory muscles via spinal circuitry to produce large positive airway pressures sufficient to generate an effective cough mechanism. This method, therefore, may be applied in patient populations with intact sensation such as stroke and amyotrophic lateral sclerosis to restore an effective cough.