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. 2018 Jun 30;7(13):e008854. doi: 10.1161/JAHA.118.008854

Figure 1.

Figure 1

Respiratory data and cerebral blood flow velocity (CBFv) for all subjects. Respiratory rate (RR) contributes to the initial surge in expiratory minute volume (VE); increased tidal volume (TV) accounts for the remainder of the VE increase in the postural tachycardia syndrome–hyperventilation (POTS‐HV) group. End tidal CO 2 (ETCO 2) decreased inversely to VE for patients with POTS‐HV , whereas CBFv decreased in parallel, as expected. CBFv decreased significantly for POTS‐HV. Administration of supplemental CO 2 to achieve approximate eucapnia normalized CBFv and improved VE and TV. POTS‐↓cardiac output (CO) indicates decreased CO without hyperventilation, defined by CO <4 L/min; and POTS–normal (NL) CO, NL CO without hyperventilation, defined by CO >4 L/min. **P<0.001, ***P<0.0001.