INTRODUCTION: While there are numerous factors that may affect pilot attentional performance, we hypothesize that an increased expiratory work of breathing experienced by fighter pilots may impose a “distraction stimulus” by creating an increased expiratory effort sensation. Therefore, the purpose of this study was to determine the extent to which increasing expiratory pressure time product or expiratory effort sensation impacts attentional performance. METHODS: Data was collected on 10 healthy participants (age: 29 ± 6 yr). Participants completed six repetitions of a modified Masked Conjunctive Continuous Performance Task protocol while breathing against four different expiratory threshold loads. Repeated measures analysis of variances and generalized additive mixed effects models were used to investigate the effects of expiratory threshold load conditions on expiratory pressure time product, expiratory effort sensation, and the influence of altered end tidal gases on Masked Conjunctive Continuous Performance Task scores. RESULTS: T he overall median hit reaction times were significantly longer as the expiratory threshold loads increased. Specific shape-conjunctive and non-conjunctive median hit reaction times were longer with increased expiratory effort sensation. Additionally, increased expiratory effort sensation did not significantly change commission error rates, but did significantly increase omission error rates. DISCUSSION: T he findings of our work suggest that both progressively greater expiratory threshold loads during spontaneous breathing and expiratory effort sensation may impair subjects’ attentional performance due to longer reaction times and increased stimuli recognition error rates.