N95-filtering facepiece respirators (FFR) use is associated with physiological changes and symptoms due to impaired nasal airflow and increased breathing resistance. We prospectively studied the effect of using an external nasal dilator (END) in gastroenterology laboratory (gastrointestinal lab) staff using N95FFR. N95FFR qualitative saccharine fit testing was performed on study participants with and without an END. Prospective data collection and comparisons included: 1) survey of perceived symptoms and difficulty of performing one day of gastrointestinal procedures with N95FFR and 1 day of gastrointestinal procedures with END plus N95FFR in random sequence; and 2) vitals and respiratory belt plethysmography in ten gastroenterologists performing simulated colonoscopy while wearing a surgical mask (SM), N95FFR plus SM, END plus N95FFR plus SM for 20 minutes each in random sequence and rapid succession. Twenty-nine of 31 participants passed the N95FFR and the END plus N95FFR fit test. Twenty-two participants (12 physicians; 11 males; mean age 44.1 years, range 31-61) performed 1 day of gastrointestinal procedures with an N95FFR and 1 day of gastrointestinal procedures with an END plus N95FFR. Significantly less difficulty with nasal breathing and severity of symptoms including breathing difficulty, headache, fatigue and frustration, occurred while using an END plus N95FFR. Respiratory plethysmography peak-to-trough measurement showed an increase during the N95FFR stage compared to the END plus N95FFR stage and the SM stage. N95FFR related respiratory changes and symptom development may be mitigated by END use.