However, many studies have given no value to iNO therapy because of a lack of impact on mortality rate. Despite this, it should be considered that the improvement in oxygenation promoted by NO inhalation may be useful as rescue therapy. Also, it is known that responsiveness to iNO can be significantly influenced by applying sufficient positive and expiratory pressure (PEEP), as this seems to recruit additional alveoli for gas exchange. In this sense, HFOV is very attractive as the application of a constant mean airway pressure maintains an "open lung" and optimizes lung recruitment; this could maximize iNO effects.