A system and method are configured to adjust the tidal volume of the breathing of a subject. The subject is self-ventilating (breathes under her own power). The adjustment of tidal volume accomplished through use of the system and/or method may reduce hypertension (e.g., lower blood pressure), reduce stress and/or anxiety (and related maladies), improve relaxation, decrease sleep latency, improve sleep quality, address other sleep disorders, and/or provide other health benefits. The system and method are effective in adjusting tidal volume while the subject is awake and/or asleep.