"Postural drainage is considered safe and effective, but may cause some side effects. The procedure is discontinued if the patient complains of headache, discomfort, dizziness, palpitations,[3] fatigue, or dyspnea. Patients may be dyspnic after the various manuovers, since the head-down position increases the work of breathing, reduces tidal volume, and decreases functional residual capacity (FRC).[citation needed]"