Mechanically assisted cough in amyotrophic lateral sclerosis: Effect on vital capacity decline and timing of non invasive ventilation onset

Background: Mechanically assisted cough with an insufflator-exsufflator (MAC) increases peak cough flow and improves management of secretions in patients with Amyotrophic Lateral Sclerosis (ALS). Study objective: To evaluate the effect of MAC on VC decline in a group of patients before the onset of NIV. Patients: Criteria for starting MAC were VC=70% of predicted value and cough insufficiency. We enrolled 43 patients not being treated with NIV during the studying time. NIV was started when VC decreased below 55% of predicted value. Results: Our patients were divided in MAC compliant (n=21) and not compliant (n=22).The groups were similar for age at onset, sex, and body site at onset, bulbar or limb. Differences were found in time from onset to MAC starting time (20,5 months in MAC not compliant vs 26,5 in compliant) and in VC at the first respiratory evaluation (85,59 vs 93,42), although the VC decrease was similar before the offering of MAC. VC at MAC starting time was similar in compliant and non compliant groups (70,8% of predicted value vs 71,7%). In the compliant group the VC decreased to 69,4% and 60,4% of predicted value at 4,7 and at 12,2 months after the start of MAC therapy. In the not compliant group VC decreased to 54,3% and 43,5% of predicted value after 4,0 and 8,1 months from offering MAC. The differences were significant: 69,38 vs 54,27; p=0,03 and 60,35 vs 43,5; p=0,008. Conclusion: MAC compliant patients, in similar condition, meet the prescription criteria for MAC treatment later than the not compliant patients. Their VC decline is reduced and they need to start treatment with NIV later than the not tolerating patients.