Pulmonary evaluation and prevalence of non-invasive ventilation in patients with amyotrophic lateral sclerosis: a multicenter survey and proposal of a pulmonary protocol

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Abstract

In order to evaluate the current standard of care for the management of respiratory failure in patients with amyotrophic lateral sclerosis (ALS), a questionaire was mailed to the Medical Directors of 48 multidisciplinary ALS centers in the United States. Twenty centers reported information on 2357 patients, mean of 124 patients per center. Pulmonary function tests were performed at each visit in 17/20 institutions. Arterial blood gases, maximal expiratory pressures and maximal inspiratory pressures were followed in three centers and serum chloride was monitored in only four centers. The use of non-invasive ventilation (NIV) was extremely variable (range 0–50%) and included 360 patients (15%). The majority of centers used symptoms/signs of hypoventilation and worsening forced vital capacity (FVC) to initiate NIV with no established protocol. A FVC between 20 and 40% was used by most centers to initiate NIV. Due to great variability in the approach to monitoring pulmonary function among ALS centers and the modest effects of current medications to slow disease progression, we propose the use of a structured protocol which can prospectively study the role of NIV in prolonging survival and improving quality of life.

Introduction

Respiratory failure is the most common cause of death in patients with amyotrophic lateral sclerosis (ALS) and is mainly due to respiratory muscle dysfunction. Respiratory symptoms usually develop late and in the setting of established limb and bulbar muscle involvement. Occasionally, however, ALS patients can present with respiratory insufficiency as the initial symptom. The respiratory insufficiency can be either insidious or acute, often precipitated by the development of a pulmonary infection.

Serial pulmonary function tests (PFTs) in ALS patients show progressive reduction in forced vital capacity (FVC) and maximal voluntary ventilation (MVV). Towards the terminal phase of the disease, the FVC declines at an accelerated rate. Spirometry is therefore of value, not only in detecting early respiratory involvement in ALS but also, through serial measurements, in predicting the course of respiratory failure [1]. The maximal inspiratory pressures (MIP) and maximal expiratory pressures (MEP) are often reduced in patients who have dyspnea. The grade of dyspnea seems to correlate with the degree of respiratory muscle impairment, as measured by MIP and MEP [2].

Patients with ALS may develop hypoventilation secondary to respiratory muscle weakness with subsequent respiratory acidosis and hypoxemia. Recently serum chloride, as a metabolic indicator of the degree of respiratory acidosis, has been identified as a prognostic factor in ALS patients [3]. A level below the lower limit of normal seems to be a sensitive indicator of impending respiratory decompensation.

Despite the clear relationship between respiratory status and the probability of survival of patients with ALS, there is a great deal of variability in the approach to monitoring pulmonary function among ALS centers. Non-invasive ventilation (NIV) has been proposed to prolong survival and to improve quality of life in ALS patients [4], [5], [6]. To evaluate this variability we prepared a questionnaire and mailed it to the Medical Directors of 48 ALS centers in the United States. It also addressed the prevalence of NIV and the different methods used to monitor and evaluate patients with ALS. In the second part of this article, we propose an integrated, multidisciplinary approach that would detect respiratory failure and intervene early in order to prevent morbidity and mortality in ALS patients and potentially improve quality of life (QOL).

Section snippets

Methods

A questionnaire was mailed to the Medical Directors of all the Muscular Dystrophy Association and ALS Association sponsored multidisciplinary ALS centers. The goal of the questionnaire was to obtain information regarding the pulmonary evaluation of ALS patients in specialized centers. The first part of the questionnaire addressed demographic data and the second part, information regarding pulmonary practices in diagnosing and treating respiratory failure in patients with ALS. The information

Results

Twenty centers reported information on 2357 patients, mean of 124 patients per center. The mean interval time for routine follow-up of patients was 3 months (range 2–6). In only five centers patients were routinely evaluated by a pulmonologist; two of the centers never consulted a pulmonologist and 13/20 did it only when needed. PFTs were performed on every visit in 17/20 institutions. Arterial blood gases, MIPs and MEPs were routinely followed in three centers. Serum chloride level was

Discussion

Based upon the results of the questionnaire, there is great variability in the approach to monitoring pulmonary function among the ALS centers. NIV is used only in a small number of patients with ALS. Given the modest effects of current medications to slow disease progression, it becomes imperative to optimize the respiratory management of ALS patients and to prospectively study the role of NIV in prolonging survival and quality of life.

As the deterioration of muscle strength and respiratory

Pulmonary monitoring

It is imperative to follow patients with ALS closely. There is no consensus about the most appropriate way to manage their respiratory needs. A pulmonologist with experience in the management of ALS patients should be part of the team taking care of them. The role of the pulmonologist includes, but is not limited to, monitoring for symptoms or signs suggestive of hypoventilation, early intervention with NIV, patient education about NIV and expiratory aids and anticipation of complications.

At

Respiratory failure and the use of noninvasive ventilation (NIV)

As discussed previously, the most common cause of death in these patients is respiratory failure. Eventually all patients with ALS will manifest a certain degree of respiratory muscle dysfunction. Theoretically, it is important to detect this dysfunction early in the course of the disease. There is no consensus, however, in the best approach for early detection of respiratory failure as demonstrated by the questionnaire we mailed. Symptoms and FVC are the parameters most commonly followed to

Assisted cough

Patients with ALS may have inability to clear secretions and/or a weak cough. If these symptoms are present or their peak flow is less than 5 l/s, patients are instructed on different cough maneuvers including ‘quad’ cough, air stacking and/or insufflator–exsufflator aid with a positive pressure of 15–20 cm H2O and a negative pressure of 6–10 cm H2O. The use of the insufflator–exsufflator aid is also recommended if the FVC is <1.5 l or <50% of predicted.

The use of this standard pulmonary

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