A randomized trial of olfactory stimulation using black pepper oil in older people with swallowing dysfunction

OBJECTIVES: To determine the effect of olfactory stimulation with volatile black pepper oil (BPO) on risk factors for pneumonia. DESIGN: A 1-month randomized, controlled study. SETTING: Nursing homes in Japan that serve as long-term care facilities for older residents who are physically handicapped, mainly because of cerebrovascular disease. PARTICIPANTS: One hundred five poststroke residents. MEASUREMENTS: Latency of the swallowing reflex (LTSR), the number of swallowing movements, serum substance P (SP), and regional cerebral blood flow (rCBF). RESULTS: Nasal inhalation of BPO for 1 minute shortened LTSR, compared with that of lavender oil and distilled water (P <.03). Compared with the period before the study, the 1-month intervention using BPO improved LTSR with an increase of serum SP (P <.01). The number of swallowing movements for 1 minute during the nasal inhalation of BPO increased (P <.001). Multiple comparisons showed a poststudy increase in rCBF within the insular cortex (P <.001). Compared with the prestudy rCBF, BPO intervention increased rCBF in the right orbitofrontal and left insular cortex (P <.001). CONCLUSIONS: Inhalation of BPO, which can activate the insular or orbitofrontal cortex, resulting in improvement of the reflexive swallowing movement, might benefit older poststroke patients with dysphagia regardless of their level of consciousness or physical and mental status.