Sigh refers to a deep breath, often exhaled in sorrow, and is normally a complement to spontaneous breathing patterns.
It is taken once every few minutes to maintain lung volume and avoid atelectasis.
Sighing keeps alveoli open that might otherwise close or reopens alveoli that have collapsed.
Sigh breathing is sometimes considered a recruitment maneuver.
Sigh is a necessary maneuver to maintain oxygenation and lung compliance during mechanical ventilation in patients undergoing anesthesia.
The use of sigh respirations allows the use of lower PEEP at constant tidal volume, maintaining lung volume, oxygenation, and hemodynamics.
Most patients receive pressure or volume, controlled, invasive, mechanical ventilation, receive a constant, or nearly constant, title, volume with each breath.
Constant ventilation with either small or large tidal volumes, delivered for even short periods, alter surfactant, increases surface tension, cause atelectasis, generates inflammatory cytokines, and produces ventilator induced lung injury.
Surfactant is normally in activated and/or depleted continuously and must be continuously secreted to maintain low surface tension and prevent atelectasis.
Surfactant’s stimulus to secrete is the mechanical stress resulting from stretching type II pneumocytes.
The sigh recruits more surfactant.
Atelectasis is a major factor that becomes because cyclic opening and closing of atelectatic spaces and over extension of patent alveoli adjacent to the atelectatic regions occur, both of which cause Ventilator induced lung injury, and result in systemic inflammation (biotrauma).