Sniff nasal inspiratory pressure test is an early marker of diurnal hypercapnia in amyotrophic lateral sclerosis patients. Preliminary results

Abstract

Background: Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease which early affects the respiratory system, rapidly leading to pulmonary failure, requiring Non Invasive ventilation (NIV). One of the first signs of respiratory failure is diurnal hypercapnia, which appears at an early stage of disease, when the pulmonary function test (PFT) is often within the normal limits. Purpose: Aim of the study was to correlate PFT and Sniff Nasal Inspiratory Pressure (SNIP) test to diurnal PaCO2 and to PaO2, as well as to markers of sleep disordered breathing (SDB), such as Apnea/Hypopnea Index (AHI), Oxygen Desaturation Index (ODI), and Total Sleep Time (TST). Methods: We evaluated anthropometric features, PFT, SNIP, Arterial Blood Gas analysis and Polyomnographic test in 22 consecutive ALS patients (14 M). Results: A statistical negative correlation was found between SNIP and PaCO2 (N=22, p=0.042, r=-043), while FVC did not correlate to PaCO2 in the same ALS population (N=22, p=0.093, r=-0.36). SNIP also negatively correlated to AHI (N=22, p=0.03, r=-0.41), while FVC did not correlate to AHI in the same group of ALS patients (N=22, p=0.08, r=-0.38). A positive correlation was also observed between SNIP and TST (N=22, p=0.03, r=0.7), while FVC did not correlate to TST in our ALS patients (N=22, p=0.07, r=0.41). Conclusion: SNIP test but not FVC is an early marker of diurnal hypercapnia and of nocturnal SDB in ALS patients. This preliminary study suggests that a SNIP test, which is non invasive and easy to reproduce, may early disclose respiratory insufficiency, leading the physicians to early use (NIV) which may prolong survival in ALS.