We agree that noninvasive positive-pressure ventilation should not be restricted to nighttime. Although we emphasized nocturnal use, we also encouraged daytime use. However, tolerance of this treatment was strictly defined as the ability to sleep nightly for at least 4 consecutive hours with the device, regardless of daytime use. We did use other interfaces, including mouth pieces for daytime ventilation. Every attempt was made to control mucus plugging and secretions by using suction devices, medications, and assisted coughing. Mechanical insufflation-exsufflation was used, but only when it became available at the end of our study.

In that context, our results may not actually differ much from Bio and Bach's experience. Our patients tolerant of noninvasive positive-pressure ventilation did not survive only 15 months. Rather, the median survival was 15 months; as our figures indicate, more than 40% of tolerant patients remain alive 2 years after initiation of noninvasive positive-pressure ventilation. We now have 10 patients with amyotrophic lateral sclerosis, including one third (6 of 18) of the tolerant patients of our original cohort, who have progressively increased the time they spend on noninvasive positive-pressure ventilation to 24 hours a day, with only one hospitalization for deep venous thrombosis. Two patients have been successfully maintained on 24 hours of ventilation per day for more than 3 years.

To simply state that the longer survival with noninvasive positive-pressure ventilation is not surprising does not validate the statement. For instance, one study has concluded that ventilation imparted a survival disadvantage in patients with Duchenne muscular dystrophy [1]. Our study remains one of the few (if not only) larger studies of a homogeneous group of patients with a neuromuscular disease for which noninvasive positive-pressure ventilation is proposed to prolong survival.

The absolute lack of intolerance reported by Bio and Bach is intriguing and is counter to our experience. Perhaps the discrepancy lies in our definition of tolerance.