@article {GramsP4302, author = {Samantha Grams and Karen Kimoto and Elen Azevedo and Christina Brito and Wellington Yamaguti}, title = {How much time is necessary to assess maximal inspiratory pressure by unidirectional expiratory valve method in subjects without artificial airway?}, volume = {44}, number = {Suppl 58}, elocation-id = {P4302}, year = {2014}, publisher = {European Respiratory Society}, abstract = {The most used method to evaluate maximal inspiratory pressure is by maintaining maximum negative pressure forced against an occluded airway (MIPsta). To overcome the need for collaboration during MIPsta, a new technique was developed using a unidirectional expiratory valve in patients undergoing invasive mechanical ventilation (MIPuni). For this evaluation, the occlusion should be maintained for at least 20 seconds to record maximal pressure. Recently, MIPuni has also been performed in subjects under spontaneous breathing without artificial airway. However, the necessary time to obtain MIPuni in subjects without artificial airway is still unknown. The aim of this study was to determine how much time is necessary to obtain MIPuni in subjects without artificial airway. Thirty-one subjects performed both MIPsta and MIPuni methods. For MIPuni, a digital vacuum manometer was attached to a unidirectional expiratory valve and a face mask for 20 seconds. During this period, all subjects were encouraged to make maximal respiratory efforts. To define the optimum duration of the maneuver, the 20 seconds of observation were partitioned every five-second interval (0-5s, 0-10s, 0-15s, 0-20s). MIPuni (117.3 {\textpm} 24.8 cmH2O; p\<0.001) presented a statistically significant difference when compared to MIPsta (102.5 {\textpm} 23.9 cmH2O). Maximal peak values for MIPuni were achieved within the 20-second time window, which differed significantly from the peak values obtained during the 0-5s interval (p=0.036). We recommend that the occlusion should be maintained for at least 20 seconds to record MIPuni in subjects without artificial airway.}, issn = {0903-1936}, URL = {https://erj.ersjournals.com/content/44/Suppl_58/P4302}, eprint = {https://erj.ersjournals.com/content}, journal = {European Respiratory Journal} }