Patients with weakened respiratory muscles may be even more in need of cough assistance than they are of ventilatory assistance. Cough assistance may be delivered manually by a caregiver or by a machine (the in-exsufflator or cough assist) that is designed to inflate the lungs and then rapidly withdraw air, as occurs in a normal cough. This clears secretions that would otherwise accumulate and provide a locus for infection, as well as interfere with gas exchange.
Bach, J. R. Noninvasive Mechanical Ventilation. Philadelphia: Hanley & Belfus, 2002.
Kinnear, W. J. M. Assisted Ventilation at Home: A Practical Guide. Oxford: Oxford Medical Publications, 1994.