Long Term Follow-up of Ventilated Patients with Thoracic Restriction and Neuromuscular Disease

Abstract

OBJECTIVE: To evaluate the long term effects of home mechanical ventilation (HMV) on pulmonary function, nighttime gas exchange, daytime arterial blood gases, sleep architecture and functional exercise capacity (6 min walk). Patients with respiratory failure attributable to thoracic restrictive disease (TRD) (kyphoscoliosis) or neuromuscular disease (NMD) were assessed, ventilated, trained and followed in a dedicated unit for the care of patients requiring long term ventilation.DESIGN: All patients admitted for home ventilation training since 1988 were reviewed. Measurements of lung function, gas exchange during wakefulness and sleep, as well as functional exercise capacity, were recorded before and immediately after the establishment of HMV. Measurements were repeated one to two years, five years and eight to 10 years later.PATIENTS: Seventy-four individuals with TRD or NMD who completed the home ventilation training program and continued with HMV during all or part of the day for at least one year were studied.RESULTS: Forty patients had TRD. The characteristics of these patients were (mean ± SE) as follows: age 58±2.4 years; vital capacity (VC) 27%±1.6% predicted, forced expiratory volume in 1 s (FEV₁) 25%±1.5% predicted; FEV₁/forced VC (FVC) 78%±1.8%. Thirty-four patients had NMD. The characteristics of these patients were as follows: age 44±3.1 years; VC 41%±4.9% predicted, FEV₁ 44±5.3% predicted; FEV₁/FVC 83%±4.2%. There was a significant improvement in distance walked in 6 min (maximum change 51.2 m in patients with NMD and 93.0 m in patients with TRD), daytime partial pressure of arterial carbon dioxide (maximum change 12.9 mmHg in patients with NMD and 10.4 mmHg in patients with TRD) and nighttime partial pressure of arterial carbon dioxide (maximum change 11.7 mmHg in patients with NMD and 18.0 mmHg in patients with TRD) over time (P≤0.004). Ventilation resulted in an improvement in partial pressure of arterial oxygen in patients with TRD (68.1±2.8 mmHg to 80.1±3.5 mmHg) and in patients with NMD (52.9±1.7 mmHg to 65.3±2.1 mmHg), although the change was not statistically significant in patients with NMD (P=0.001 in patients with TRD; P=0.105 in patients with NMD). The improvement after ventilation was maintained over several years. Sleep efficiency (75%±18%, 79%±2.2%), the arousal index (13.4±13 events/h, 28.2±17 events/h) and the apnea-hypopnea index (10.1±11.3 events/h, 13.9±9.5 events/h) did not change with time in either patients with TRD or patients with NMD, respectively (P≥0.5).CONCLUSIONS: HMV was associated with sustained, long term improvements in nighttime and daytime gas exchange in patients with TRD and NMD. Function exercise capacity increased in patients with TRD and in a subgroup of ambulatory patients with NMD. In patients with TRD, these improvements were maintained for up to 10 years after HMV was established.