Expert opinion on the suspicion of diaphragmatic dysfunction. Expert opinion on the suspicion of diaphragmatic dysfunction. The figure describes the current practice of how the members of the task force suspect and treat respiratory muscle dysfunction (especially for unilateral and bilateral diaphragm weakness), outside of the intensive care setting (this is, however, not intended as a recommendation for clinical practice). In the absence of clearly defined lower limits of normal, it has long been accepted that a PImax or sniff-Pdi or Pdimax ≥80 cmH2O in men and ≥70 cmH2O in women, and/or SNIP ≥70 cmH2O in men and ≥60 cmH2O in women are generally thought to exclude clinically significant inspiratory muscle weakness [1], and unilateral and bilateral diaphragm paralysis can be expected to decrease PImax or SNIP in the ranges of 60% [41] and <30% [42] of the predicted values, respectively. However, these values may be greatly impacted by the presence of underlying obstructive or restrictive lung disease [40]. A Pdi,tw >10 cmH2O with unilateral phrenic nerve stimulation or >20 cmH2O with bilateral phrenic nerve stimulation also rules out clinically significant weakness [1]. Please refer to the text for more details. SNIP: sniff nasal inspiratory pressure; VC: vital capacity; PImax: maximal inspiratory pressure; TF: thickening fraction of the diaphragm; PSG: polysomnography; CPAP: continuous positive airway pressure; Pdi: transdiaphragmatic pressure; Pdi,tw: twitch transdiaphragmatic pressure; NPPV: noninvasive positive pressure ventilation; PaCO2: arterial partial pressure of carbon dioxide; SpO2: peripheral oxygen saturation. Pierantonio Laveneziana et al. Eur Respir J 2019;53:1801214 ©2019 by European Respiratory Society