TABLE 1

Patient characteristics at the time of the study

Overall populationPresence of PIPsAbsence of PIPsp-value
Subjects1486
Anthropometric data
 Age years63 (57–66)62 (55.5–67.5)64 (57–66)0.85
 Body mass index kg·m−222.14 (20.7–24.6)21.78 (20.7–23.2)25.11 (22.0–30.8)0.08
Neurological assessment
 ALS-FRS-R score (out of 48)21 (14–23)22.5 (20.5–23.5)13.5 (13–20)*0.04
 Norris bulbar score (out of 39)37 (35–37.2)37 (35–37.5)35 (25.7–37.2)0.28
 Time since onset of first neurological symptoms months44 (25–53)28.5 (24–44)53 (49–71)*0.01
 Time since initiation of NIV months11 (6–23)9 (5.5–21.5)14 (7–48)0.41
Respiratory assessment
 Sitting FVC % pred45 (29.2–62.5)50 (36–66)36 (29–39)0.19
 Supine FVC % pred35.5 (31–48)38 (32.2–60)25 (19.7–34.7)0.12
PImax % pred24.5 (14–32.5)32 (22.2–39.5)8 (4.2–21.5)0.14
 SNIP % pred20.5 (16–34.5)34 (21.7–38.5)12 (6–18)*0.04
 mMRC dyspnoea score4 (3–4)4 (3.5–4)3.5 (3–4)0.76
Efficacy of NIV
 Morning PaCO2 during spontaneous breathing44 (42–49)47.5 (43–49.5)43 (42–44)0.34
 Morning PaCO2 after 1 h of NIV39 (36–41)38 (36–42)39 (36–40.5)0.76
 Night-time spent with SpO2 <90% on NIV % of recording0 (0–7.7)1 (0–5.7)2 (0–10)0.63
 Tidal volume512.5 (440–640)520 (410–615)502.5 (440–640)1.00
 NIV hours·day−111.5 (8–16)8 (7.5–12.5)15 (12–18)0.05
  • Data are presented as n or median (interquartile range), unless otherwise stated. Forced vital capacity (FVC) was measured in sitting and supine positions using an EasyOne ultrasound spirometer (NDD Medical Technologies, Andover, MA, USA). Inspiratory muscle strength was evaluated by measuring the maximal inspiratory pressure at the mouth (PImax) and at the nostril (sniff nasal inspiratory pressure (SNIP)) using a Micro-RPM digital manometer (Micro Medical, Chatham, UK). One of the patients with an initial bulbar form of amyotrophic lateral sclerosis (ALS) did exhibit a pre-inspiratory potential (PIP) during resting breathing; the other did not. The patient with an initial respiratory form of ALS did exhibit a PIP during resting breathing. ALS-FRS-R: Amyotrophic Lateral Sclerosis Functional Rating Scale Revised; NIV: noninvasive ventilation; mMRC: modified Medical Research Council; PaCO2: arterial carbon dioxide tension; SpO2: arterial oxygen saturation measured by pulse oximetry. *: p<0.05 for presence of PIPs versus absence of PIPs.