Sighs are the deep breaths or spontaneous hyperinflations that is 3 to 5 times the normal inspiratory volume. Spontaneous sigh is said to play a role in preventing microatelectasis (i.e. collapse of alveoli of the lungs) and also restart the breathing pattern when it becomes irregular. The patients who are on mechanical ventilation may undergo atelectasis because this assisted ventilation provides preset breaths to the patient. Many studies have indicated that adding assisted inflations (i.e. sighs) every several minutes to the mechanical ventilation have proved to be beneficial as they boost the lung compliance and oxygen levels of the blood by improving the gas exchange. In some studies it was found that adding sights to assisted ventilation helped in minimizing the risk of lung injury and showed better clinical outcomes in patients with acute hypoxemic respiratory failure. However, with advancement and development of Positive end-expiratory pressure (PEEP), sighs are no more added to the mechanical ventilation.