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Abstract
Amyotrophic lateral sclerosis (ALS) is an idiopathic degenerative disease affecting upper and lower motor neurons and is characterized by atrophy of voluntary skeletal muscles. The disease is typically progressive over 3 to 5 years and usually culminates in death from respiratory failure.
Respiratory affection in ALS is usually in the form of respiratory muscles weakness, alveolar hypoventilation, sleep disordered breathing and impaired cough.
Several studies indicated the positive impact of non-invasive ventilation on the quality of life and survival in patients with ALS.
After initiation of NIV, it is recommended to monitor the efficiency of this treatment to make sure that it is effective and achieving its goals.
Different forms of monitoring are available including clinical monitoring, monitoring of arterial blood gases and nocturnal monitoring using simple pulse oximeters and different types of polygraphies.
The present study was conducted on 20 patients with ALS and respiratory affection justifying the initiation of NIV.
The aims of the present study were to assess the ability of the portable polygraph (Embletta) to detect different respiratory events in the studied patients before NIV and to monitor the efficiency of NIV comparing it with the results of the automated polygraph (Reslink).
All the patients were subjected to clinical neurological and respiratory assessments, respiratory tests (spirometry, PImax, SNIP, ABG), nocturnal pulse oximetry and a nocturnal polygraphic study using the polygraph Embletta before initiating NIV.
The respiratory tests confirmed the need for NIV in our patients, there was a significant statistical difference between the sitting and supine FVC and the results of nocturnal pulse oximetry showed marked nocturnal desaturations with more than 5% of the recorded time with SpO2 < 90% in all patients.
The results of polygraphy in spontaneous breathing showed oxygen desaturations in all patients, evident sleep disordered breathing with a mean AHI of 14.8± 18.8 events / hour, neck muscles recruitment in all patients, paradoxical breathing in 6 patients. The most frequent respiratory events detected were non obstructive hypopneas resulting from diaphragmatic weakness.
Under NIV, nocturnal monitoring was done using the polygraph Embletta and the automated polygraph Reslink simultaneously. The efficiency of ventilation was determined according to oxygen saturation. In the presence of desaturations with >5% of the recorded time spent with <90% SpO2, the patient was considered mal ventilated.
The patients were divided into 2 groups according to the efficiency of ventilation, group I (well ventilated) consisted of 6 patients, and group II (mal ventilated) consisted of 14 patients.
The present study found a complete overlap between the two devices in determining the efficiency of ventilation.
The cause of mal ventilation was analysed using the tracings of each polygraph independently. Five causes were found to be responsible for suboptimal ventilation in Group II patients: Air leakage, obstructive respiratory events, mixed respiratory events (obstructive and central), patient ventilator asynchronism and low tidal volume.
Among the 14 patients who were mal ventilated (group II), the Reslink and Embletta found 6 patients with the same causes of decreased ventilation efficiency, while 8 patients had different cause detected by each device.
A statistical comparison was done between the Reslink and Embletta regarding the detected causes of mal ventilation.
A significant statistical difference was found between the two devices in detection of obstructive events, mixed events and patient ventilator asynchronism, while no significant statistical difference between them in the detection of air leakage and low tidal volume.
The present study demonstrated that automated ventilator coupled polygraph (Reslink) is a rapid process and helpful in detection and quantification of leaks, but it has certain limitations, it is unable through its automatic analysis to properly classify the respiratory events (does not differentiate between obstructive events and mixed or central events), it overestimates the obstructive events, it is also unable to diagnose patient-ventilator asynchronism. These limitations may affect the therapeutic decisions.
The portable polygraph (Embletta) has many advantages; the presence of a pneumo-tachograph is contributive to a precise analysis of patient-ventilator interactions, its proved ability in detecting and properly classifying the respiratory events made it a portable alternative to polysomnography in this issue, but it has some limitations, first of all, manual analysis is a time consuming process, also the detection and quantification of air leakage and the estimation of tidal volume are not accurate.
It is recommended to monitor ALS patients treated with NIV regularly. According to the results of this study, it is proposed that monitoring procedure takes place in a stepwise manner starting from nocturnal pulse oximetry to have a rapid and accurate idea about the nocturnal oxygen saturation, then the ventilator coupled polygraph (Reslink) and if the patient is judged mal ventilated and the cause cannot be detected or the detected cause is doubtful (obstructions), then perform a simple polygraphic study (Embletta) which provide an excellent .