Figure 6. Sleep-related changes in tidal volume, respiratory period, and minute ventilation.

Panels A, B, and C show tidal volume (V_T), breath duration (T_TOT), and minute volumes (V_E), respectively, during light period epochs of NREMS and REMS. Panel D shows a Poincaré plot of T_TOT of each breath (n) versus the following breath (n+1) during REMS for a KO mouse fed a HFD. Panels E and F show the standard deviations of T_TOT around a new set of axes oriented with (SD₁) or orthogonal to (SD₂) the line of identity of the Poincaré plots, as shown in C; these reflect short-term and long-term variability of T_TOT, respectively [20], [21]. Data are means ± SEM for KO mice fed a SD (n = 4) or a HFD (n = 8) and for WT mice fed a SD (n = 7) or a HFD (n = 5). For abbreviations and symbols see Figures 1 and 3. Detailed ANOVA results are reported in Table S5.