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Respir Care. 2018 Sep;63(9):1132-1138. doi: 10.4187/respcare.05866. Epub 2018 May 15.

Passive Versus Active Circuit During Invasive Mechanical Ventilation in Subjects With Amyotrophic Lateral Sclerosis.

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NEuroMuscular Omnicentre, Fondazione Serena Onlus, Milan, Italy.
NEuroMuscular Omnicentre, Fondazione Serena Onlus, Milan, Italy.
Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milan, Italy.
Respiratory Rehabilitation Care Unit, Fondazione Don Carlo Gnocchi, Istituto di Ricovero e Cura a Carattere Scientifico Santa Maria Nascente, Milan, Italy.
Pulmonary Rehabilitation Unit, Istituti Clinici Scientifici Maugeri, Istituto di Ricovero e Cura a Carattere Scientifico, Pavia, Italy.



Until recently, it has been considered essential to maintain the use of a double-limb circuit in patients with amyotrophic lateral sclerosis (ALS) to avoid rebreathing expired air during invasive mechanical ventilation. Currently, life-sustaining home ventilators can work with a single, lighter circuit that is easier to manage. Our aim was to evaluate the effectiveness and safety of a single-limb circuit with intentional leaks (passive circuit) in comparison with a circuit with an expiratory valve (active circuit), in subjects with ALS who use invasive home ventilation.


We conducted a retrospective single-center study. The enrolled subjects were divided into 2 groups according to the type of exhalation port. The aim of the study was to compare arterial blood gases; nocturnal oxygen saturation recordings; and the occurrence of adverse events, both clinical and technical events. In addition, we compared the rate of mortality and unplanned hospital admissions that occurred within a year after discharge from the hospital.


Forty-three subjects were included in our study: 23 who used a passive circuit and 20 who used an active circuit. No significant difference in nocturnal and diurnal gas exchanges was detected. The incidence of adverse events was significantly higher in the active circuit group (85% in active circuit vs 30% in passive circuit, P < .001). However, by splitting the adverse events into 2 categories, clinical and technical, the technical events were significantly more frequent in the active circuit group. None of these events led to hospital admission or death.


The passive circuit was shown to be as effective and safe as the active circuit during home invasive ventilation in the subjects with amyotrophic lateral sclerosis. A future randomized controlled study is necessary to confirm these results and to extend indications to other pathologies.


amyotrophic lateral sclerosis (ALS); chronic respiratory failure; mechanical ventilation; neuromuscular diseases; respiratory therapy; tracheostomy

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