Rationale: Central processing of dyspnea relief remains largely unknown.
Objectives: To identify physiologic determinants, quality of sensation, and brain activation associated with dyspnea relief.
Methods: Dyspnea relief was induced in 10 healthy volunteers by decreasing an adjustable external resistive load ( approximately 15-50 cm H(2)O/L/s). Brain imaging (positron emission tomography) was performed during either dyspnea or relief.
Measurements and main results: Perceived intensity of moderate and high relief was similar to that of its preceding dyspnea (Borg scores = 5.10 +/- 1.49 vs. 5.3 +/- 1.4, and 2.78 +/- 0.94 vs. 2.99 +/- 0.94, respectively; P >/= 0.05) and was predominantly related to reversal of dyspnea-induced increased mouth pressure/ventilation ratio (r(2) = 0.88, P < 0.001). Dyspnea relief involved specific, mostly positively valenced descriptors (i.e., breathing-related pleasure and/or reward). Most significant relief-associated brain activation was detected in the left anterior cingulate cortex (Z score = 4.7, corrected P < 0.05) and additional activation (uncorrected P < 0.0001) in the posterior cerebellum and in the temporal and prefrontal cortices. For dyspnea, significant activation was located in the right caudate nucleus, the anterior cerebellum (Z = 5 and 4.65, respectively; corrected P < 0.05), and the premotor cortex, whereas deactivation occurred in the left prefrontal cortex (Z = 4.11).
Conclusions: Relief of acute load-induced dyspnea is not simply the neutral perception of dyspnea decrease but rather a strong, positively valenced sensation that is associated with characteristic brain activation distinct from that subserving dyspnea perception and possibly reflecting activation of a dyspnea modulation network.