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, FEV144±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.

The timed walk test as a measure of severity and survival in idiopathic pulmonary fibrosis

“…The 6MWT is widely used and provides important prognostic information in several chronic cardiopulmonary disease states [13][14][15][16]. The primary outcome measurement of the 6MWT is the distance walked during a period of 6 min, which may include periods of rest.…”

“…A practical and simple measurement of functional status that is widely used as a clinical tool and outcome measure of patients with heart [13], obstructive lung disease [14], vascular [15], and neuromuscular disease [16] is the 6-min walk test (6MWT). However, the physiological abnormalities associated with disease severity and progression in IPF are not fully characterised by the distance of the 6MWT [7,9,12].…”

The Importance of Controlling PaCO2Throughout Long-Term Noninvasive Ventilation

“…10,12,13,19,20 Therefore, when identifying predictive risk factors, parameters observed after NIV initiation appear more valuable and reliable than those observed before the commencement of NIV. 18,20,22 We previously showed that P aCO 2 measured a few months after the start of long-term NIV is a possible prognostic factor in subjects with both restrictive thoracic disease 18 and COPD.…”

“…[3][4][5] Arterial blood gases (ABGs) stabilize a few months after NIV initiation, and are sustained for many years in sub-jects with both COPD 10,18 and restrictive thoracic disease. 10,12,13,19,20 We previously showed that the average P aCO 2 of subjects breathing spontaneously decreases rapidly within several weeks of NIV, and thereafter increases gradually throughout long-term NIV. 18,20 We hypothesized that the adaptive mechanism that permits chronic hypercapnia occurs even in subjects receiving long-term NIV.…”

“…[3][4][5][6][7][8][9] Over the last 2 decades, domiciliary NIV has been widely used to treat subjects with chronic hypercapnic respiratory failure. [10][11][12][13][14][15][16] Improved daytime P aCO 2 after the initiation of NIV has been correlated with a change in P aCO 2 while receiving nighttime NIV, 6,17 and the most important mechanism underlying the long-term reduction in daytime P aCO 2 is an augmented ventilatory response to CO 2 . [3][4][5] Arterial blood gases (ABGs) stabilize a few months after NIV initiation, and are sustained for many years in sub-jects with both COPD 10,18 and restrictive thoracic disease.…”