 Sleep in critically-ill patients is commonly severely fragmented, and sleep architecture is altered as compared to a healthy person. This abnormal sleep may cause some important adverse psychological and physiological consequences. Noise, light, patient-care activities, pain, or medications are some of the contributing factors to sleep disruption in the ICU. Recent evidence also suggests that invasive mechanical ventilation IMV itself may lead to sleep fragmentation in the ICU. Noninvasive ventilation NIV is a well-established, relatively new form of ventilation which improves sleep quality or gas exchange in some patients with chronic hypoventilatory disorders. Although sleep may be disrupted due to discomfort from the mask or air leaking during NIV use; intermittent use of NIV may result in better sleep quality between NIV sessions. The effects of NIV on sleep in the acute care setting have not yet been studied. 