Sustained Maximal Inspiration—a Rationale for Its Use

Abstract

A monotonous pattern of postoperative tidal ventilation (lacking "sighs") is the most important cause of pulmonary complications. This pattern can occur secondary to pain, surgical dressings, or narcotics. Treatment of postoperative pulmonary complications has included chest physiotherapy, blow bottles, intermittent positive pressure breathing (IPPB), and, recently, sustained maximal inspiration (SMI). The keys to successful SMI therapy are to generate enough transpulmonary pressure to achieve large inflating volumes, and to maintain inspiration for several seconds. During sustained inspiration, volume transfer from hyperin-flated alveoli to collapsed lung units enhances longterm alveolar stability. Studies comparing SMI to other therapy of postoperative patients demonstrate reduced incidence of pulmonary complications. SMI can easily be accomplished hourly and at low cost. SMI equipment is simple, and the problem of equipment-induced nosocomial infection is minimized. The SMI maneuver requires a certain level of patient understanding and participation and thus some patients may be unable to effectively perform the maneuver.