Biphasic Cuirass Ventilation (BCV) is a noninvasive modality that reproduces physiological breath with alternating negative and positive pressure via an external cuirass. Despite the advantages of BCV in preventing intubation and promoting secretion clearance, it does not entirely avoid the development of atelectasis, a significant complication capable of impairing gas exchange and increasing the risk of infection. This chapter reviews the pathophysiology of atelectasis during BCV, including mechanisms such as ineffective transpulmonary pressure gradients, alveolar recruitment failure in noncompliant lungs, and secretion retention. This chapter identifies some of the key risk factors, both patient-related factors like obesity and neuromuscular weakness, and device-related factors such as suboptimal settings or ill-fitting cuirasses. Diagnosis is reviewed, with specific focus on the utility of lung ultrasound as a sensitive bedside diagnostic test. Management is explored in detail, with a focus on optimization of BCV parameters, the application of adjunctive secretion clearance techniques, and strategic positioning. This chapter finishes by addressing the limitations of BCV and pointing out that, while a valuable tool, vigilance and early intervention are necessary to negate atelectasis, with escalation to positive pressure ventilation continuing to be necessary in refractory cases.