Carotid chemoreflex and muscle metaboreflex interact to the regulation of ventilation in patients with heart failure with reduced ejection fraction

Figures

• 

  Figure 1. Illustration of experimental conditions. Conditions: (a) 21% O2 inhalation (tonic carotid chemoreflex activity) with free flow to the lower limbs (inactive muscle metaboreflex); (b) 100 O2 inhalation (suppressed carotid chemoreflex activity) with circulatory occlusion in the lower limbs (muscle metaboreflex activation); (c) 21% O2 inhalation (tonic carotid chemoreflex activity) with circulatory occlusion in the lower limbs (muscle metaboreflex activation); and (d) 100% O2 inhalation (suppressed carotid chemoreflex activity) with free flow to the lower limbs (inactive muscle metaboreflex)

• 

  Figure 2. Systolic arterial pressure (SAP) at rest, end‐exercise and during recovery under tonic carotid chemoreflex activity (panel a), muscle metaboreflex activation (panel b) and both reflexes active (panel c) in contrast to both reflexes inactive (i.e., control). n = 10 for panels a and b, n = 9 for panel c. Data reported as mean ± SEM and analyzed by two‐way repeated‐measures ANOVA followed by Fisher´s post hoc. *p < .05 versus control

• 

  Figure 3. Diastolic arterial pressure (DAP) at rest, end‐exercise and during recovery under tonic carotid chemoreflex activity (panel a), muscle metaboreflex activation (panel b) and both reflexes active (panel c) in contrast to both reflexes inactive (i.e., control). n = 10 for panels a, b and c. Data reported as mean ± SEM and analyzed by two‐way repeated‐measures ANOVA followed by Fisher's post hoc. *, p < .05 versus control

• 

  Figure 4. End tidal partial pressure of O2 (PETO2) and CO2 (PETCO2) at rest, end‐exercise and during recovery under tonic carotid chemoreflex activity (panel a), muscle metaboreflex activation (panel b) and both reflexes active (panel c) in contrast to both reflexes inactive (i.e., control). n = 7 for all PETO2 time points, n = 7 for resting PETCO2 and n = 10 other PETCO2 time points. In order to raise the statistical power, resting data were not included in the ANOVA analysis. Data reported as mean ± SEM and analyzed by two‐way repeated‐measures ANOVA followed by Fisher´s post hoc. *p < .05 versus control

• 

  Figure 5. Minute ventilation (V˙E) at rest, end‐exercise and during recovery under tonic carotid chemoreflex activity (panel a), muscle metaboreflex activation (panel b) and both reflexes active (panel c) in contrast to both reflexes inactive (i.e., control). Data reported as mean ± SEM and analyzed by two‐way (panels a, b and c; n = 9, the outlier was removed), one‐way [panel d; n = 10 (with the outlier) or 9 (without the outlier)] repeated‐measures ANOVA (followed by Fisher´s post hoc, if needed) and single mean Student's t‐test (panel d; n = 9, the outlier was removed). *p < .05 versus control

• 

  Figure 6. Tidal volume (VT) at rest, end‐exercise and during recovery under tonic carotid chemoreflex activity (panel a), muscle metaboreflex activation (panel b) and both reflexes active (panel c) in contrast to both reflexes inactive (i.e., control). Bars represent change versus control (panel d) and crossed out circle represents an outlier. Data reported as mean ± SEM and analyzed by two‐way (panels a, b and c; n = 9, the outlier was removed), one‐way [panel d; n = 10 (with the outlier) or 9 (without the outlier)] repeated‐measures ANOVA and single mean Student's t‐test (panel d; n = 9, the outlier was removed)

• 

  Figure 7. Respiratory frequency (f R) at rest, end‐exercise and during recovery under tonic carotid chemoreflex activity (panel a), muscle metaboreflex activation (panel b) and both reflexes active (panel c) in contrast to both reflexes inactive (i.e., control). Bars represent change versus control (panel d). Data reported as mean ± SEM and analyzed by two‐way (panels a, b and c; n = 9, the outlier was removed), one‐way [panel d; n = 10 (with the outlier) or 9 (without the outlier)] repeated‐measures ANOVA (followed by Fisher´s post hoc, if needed) and single mean Student's t‐test (panel d; n = 9, the outlier was removed). *p < .05 versus control. † p < .05 versus all other conditions