Treating respiratory failure in ALS: the details are becoming clearer

Breathing new life into treatment advances for respiratory failure in amyotrophic lateral sclerosis patients

SUMMARY In the last three decades, improvements in respiratory management are responsible for increasing survival and improving quality of life for amyotrophic lateral sclerosis (ALS) patients. Nowadays, ALS patients with respiratory involvement are offered a support treatment other than the traditional respiratory palliative care. Knowledge about available respiratory support potentialities is essential for appropriate, customized and effective treatment of ALS, which should probably be started sooner than the conventional approach. There is evidence supporting that respiratory support has a larger impact than riluzole on survival. Noninvasive ventilation is essential in the treatment of ALS patients with respiratory involvement. In this article methods to determine respiratory failure in ALS, mechanical invasive and noninvasive ventilation, telemetry, diaphragm pacing, cough aids and respiratory exercise are reviewed, after a brief overlook of respiratory insufficiency in ALS.

Formal ventilation patient education for ALS predicts real-life choices

Our objective was to evaluate a single-session, hands-on education programme on mechanical ventilation for ALS patients and caregivers in terms of knowledge, change in affect and to determine whether ventilator decisions made after the education sessions predict those made later in life. Questionnaires were administered to 26 patients and 26 caregivers on four separate occasions. The questionnaires assessed knowledge of ventilatory support, feedback on the nature of the education programme, as well as self-reported emotional well-being. All patients were followed until their death or until initiation of invasive ventilation. Both groups demonstrated significant improvements in knowledge as a result of the education session which was retained after one month. There was no change in patient or caregiver reports' self-reported emotional well-being. The choices of ventilatory support expressed at one month (T4) accurately predicted the real-life clinical choices made by 76% of patients. Any difference resulted from choosing palliative care. Hands-on patient and caregiver education results in improved knowledge, assists in decision-making with respect to ventilatory support, and is not associated with a worsening of affect. It also provides for an accurate prediction of real-life choices and avoids undesired life support interventions and critical care admissions.

MnSOD deficiency has a differential effect on disease progression in two different ALS mutant mouse models

Mitochondrial dysfunction and oxidative stress are thought to participate in the pathogenesis of amyotrophic lateral sclerosis (ALS). The purpose of this study was to determine the effect of reduced mitochondrial antioxidant defense on lifespan and disease progression in two mouse models of familial ALS (G93A and H46R/H48Q mutant lines) that represent pseudo-wildtype and metal-deficient ALS mutants, respectively. The metal-deficient H46R/H48Q mutant differs from the G93A mutant in that it cannot bind copper in the active site and thus lacks SOD activity. We crossed each of these mutant lines with mice deficient in the mitochondrial matrix antioxidant enzyme MnSOD (Sod2+/- mice). In both high (G93A1Gur) and low (G93ADL) copy G93A strains, MnSOD deficiency caused a decrease in lifespan that was associated with a reduced disease duration rather than earlier disease onset. In contrast, MnSOD deficiency had no effect on lifespan or disease parameters of H46R/H48Q mutant mice. MnSOD deficiency thus has a differential effect on disease progression in different mutant SOD1 ALS mouse models, suggesting that different ALS-causing mutations in SOD1 result in disease progression by at least proximally different mechanisms/pathways.

Denervation-induced skeletal muscle atrophy is associated with increased mitochondrial ROS production

Reactive oxygen species (ROS), especially mitochondrial ROS, are postulated to play a significant role in muscle atrophy. We report a dramatic increase in mitochondrial ROS generation in three conditions associated with muscle atrophy: in aging, in mice lacking CuZn-SOD ( Sod1−/−), and in the neurodegenerative disease, amyotrophic lateral sclerosis (ALS). ROS generation in muscle mitochondria is nearly threefold higher in 28- to 32-mo-old than in 10-mo-old mice and is associated with a 30% loss in gastrocnemius mass. In Sod1−/− mice, muscle mitochondrial ROS production is increased >100% in 20-mo compared with 5-mo-old mice along with a >50% loss in muscle mass. ALS G93A mutant mice show a 75% loss of muscle mass during disease progression and up to 12-fold higher muscle mitochondrial ROS generation. In a second ALS mutant model, H46RH48Q mice, ROS production is approximately fourfold higher than in control mice and is associated with a less dramatic loss (30%) in muscle mass. Thus ROS production is strongly correlated with the extent of muscle atrophy in these models. Because each of the models of muscle atrophy studied are associated to some degree with a loss of innervation, we were interested in determining whether denervation plays a role in ROS generation in muscle mitochondria isolated from hindlimb muscle following surgical sciatic nerve transection. Seven days postdenervation, muscle mitochondrial ROS production increased nearly 30-fold. We conclude that enhanced generation of mitochondrial ROS may be a common factor in the mechanism underlying denervation-induced atrophy.

A population based study of respiratory function in motor neuron disease patients living in Tayside and North East Fife, Scotland

Respiratory failure is a major cause of morbidity and the principal cause of death in motor neuron disease; non-invasive ventilation is increasingly used worldwide to palliate the respiratory symptoms. This observational study was designed to evaluate the prevalence of respiratory insufficiency within the motor neuron disease population of Tayside and North East Fife, Scotland. Twenty-six patients were identified, their diagnosis confirmed according to agreed criteria and subjected to the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale, the Epworth Sleepiness questionnaire; spirometry, sniff nasal inspiratory pressure and nocturnal pulse oximetry measurements.Twenty-two (84.6%) patients reported one or more symptoms of respiratory insufficiency, 19 patients (73%) had forced vital capacity <80% of predicted in the sitting position and 10 (38.5%) had oxygen saturation <90% for >5% of night. On this basis a potential 10 patients required consideration for ventilation. As well as probable improvement in quality of life and survival for those patients this potential increase in workload has major educational, management and resource implications for health care providers.

Longitudinal assessment of noninvasive positive pressure ventilation adjustments in ALS patients

The absence of data guiding optimal titration of noninvasive positive pressure ventilation (NIPPV) over time in ALS patients may contribute to the under-prescribing of NIPPV. We conducted a retrospective, single-center, chart review assessment of NIPPV pressure settings used for symptomatic treatment of ALS patients to determine NIPPV adjustments, and to compare survival between those who were tolerant and intolerant to NIPPV. All subjects were started on nocturnal NIPPV at 8 and 3 cm H2O inspiratory and expiratory pressure, respectively. Of the 18 tolerant subjects identified, 4 (22%) had no NIPPV pressure changes before death; 8 (44%), 1 change; 4 (22%), 2 changes; 1 (6%), 3 changes; and 1 (6%), 5 changes. Most pressure changes occurred during the first year of NIPPV initiation. The maximum pressure needed for comfort by any patient in this study was 19/5 cm H2O, while 4 (22%) found the original 8/3 cm H2O settings to be sufficient until death. Subjects in the tolerant group had better survival, when adjusting for age and site of symptom onset (bulbar versus limb), with a hazard ratio of 0.23 [95% confidence interval: 0.10, 0.54]. The current data suggest that ALS patients who are tolerant to NIPPV typically need at least one upward change in pressure settings. Tolerance to relatively low NIPPV inspiratory pressures is associated with improved survival.

Nocturnal hypoxia in motor neuron disease is not predicted by standard respiratory function tests

BACKGROUND

With increasing awareness of motor neuron disease (MND) in Australia, the approach to respiratory management of patients with this disease will more commonly face the respiratory physician.

AIM

The aim of this study was to determine if standard respiratory function tests could determine the presence of nocturnal hypoxia (NH) in patients with MND.

METHODS

Respiratory function tests were used to examine daytime respiratory function, and sleep studies were used to detect NH in 16 consecutive patients with MND and in 9 healthy control subjects. Demographic data, clinical parameters, respiratory function tests and sleep studies were obtained. Statistical analyses were carried out using t-tests and anova, where appropriate.

RESULTS

NH was detected in 50% of patients with MND, with no hypoxic events detected in the control group. Standard respiratory function tests were not able to predict the presence of NH.

CONCLUSION

There was no correlation between respiratory function tests and NH. This study emphasizes the inability of standard respiratory function tests to predict NH that may arise early in the course of MND.

Development of chronic hypoventilation in amyotrophic lateral sclerosis patients

Early prediction of respiratory muscle involvement and chronic hypoventilation (CH) in amyotrophic lateral sclerosis (ALS) patients can help to plan mechanical ventilatory aids and palliative care interventions well before respiratory failure occurs. To describe the natural history of the progressive pulmonary dysfunction leading to CH, and to identify potential parameters associated with its development in ALS, we prospectively followed 38 ALS patients up to 26 months, starting from their first presentation at our Clinic. At study entry, median FVC was 87% (interquartile range: 72-104%) and declined by 10% after 6 months (range: 2-49%), showing a very high inter-patient variability. Over the 26-months follow-up, 19 patients (50%) presented CH in the first 12 months, and eight patients (21%) developed CH in the remaining 14 months of the study. The remaining 29% of patients did not show signs of CH during the whole period of observation. In the Cox model, the category of disease progression (rapid vs. intermediate and slow), assessed using the Appel ALS Rating Scale (AARS) in the first 3 months after presentation, was the only variable associated with a significantly increased likelihood of CH. We conclude that CH can occur within 1 year from presentation in a great proportion of patients, independently from their initial respiratory status. Including the patients in specific categories of early disease progression, as assessed with the AARS, could be a sensitive method to identify patients with different risk of developing CH, and may help physicians to more efficiently plan the frequencies of respiratory evaluations, initiate mechanical ventilation and discuss advance directives with the patients and their caregivers.

Alternatives to endotracheal intubation for patients with neuromuscular diseases

OBJECTIVE

To evaluate the usefulness of continuous noninvasive mechanical ventilation and mechanical coughing aids to avoid endotracheal intubation and tracheostomy during episodes of acute respiratory failure in patients with neuromuscular disease.

DESIGN

We conducted a prospective cohort study at the respiratory medicine ward of a university hospital to study the success rate of the use of continuous noninvasive mechanical ventilation and manually and mechanically (CoughAssist) assisted coughing to avert endotracheal intubation in 24 consecutive episodes of acute respiratory failure for 17 patients with neuromuscular disease. The noninvasive mechanical ventilation and coughing aids were used to reverse decreases in oxyhemoglobin saturation and relieve respiratory distress that occurred despite oxygen therapy and appropriate medication. Noninvasive mechanical ventilation was delivered by volume ventilators (Breas PV 501) alternating nasal/oronasal and oral interfaces.

RESULTS

Noninvasive management was successful in averting death and endotracheal intubation in 79.2% of the acute episodes. There were no significant differences in respiratory function between the successfully treated and unsuccessfully treated groups before the current episode. Bulbar dysfunction was the independent risk factor for failure of noninvasive treatment (P < 0.05; odds ratio, 35.99%; 95% confidence interval, 1.71-757.68).

CONCLUSIONS

Intubation can be avoided for some patients with neuromuscular disease in acute respiratory failure by some combination of noninvasive mechanical ventilation and mechanically assisted coughing. Severe bulbar involvement can limit the effectiveness of noninvasive management.

Assessment of disease progression in motor neuron disease

Motor neuron disease (MND) is characterised by progressive deterioration of the corticospinal tract, brainstem, and anterior horn cells of the spinal cord. There is no pathognomonic test for the diagnosis of MND, and physicians rely on clinical criteria-upper and lower motor neuron signs-for diagnosis. The presentations, clinical phenotypes, and outcomes of MND are diverse and have not been combined into a marker of disease progression. No single algorithm combines the findings of functional assessments and rating scales, such as those that assess quality of life, with biological markers of disease activity and findings from imaging and neurophysiological assessments. Here, we critically appraise developments in each of these areas and discuss the potential of such measures to be included in the future assessment of disease progression in patients with MND.