Table 3.
Causal coupling index C and directionality index D computed between respiratory flow (r), systolic arterial pressure (s), and heart period (t) time series measured during the tilt test protocol (TT; su: supine position, up: upright position) and during the paced breathing protocol (PB; sp: spontaneous breathing, pa: paced breathing) in the study of vasculo-pulmonary (VP), cardio-pulmonary (CP), and cardio-vascular (CV) coupling.
| TT protocol (N = 15) |
PB protocol (N = 15) |
||||
|---|---|---|---|---|---|
| su | up | sp | pa | ||
| VP | Cr → s | 0.010 (8) | 0.031 (9) | 0.008 (8) | 0.046** (12) |
| Cs → r | 0 (5) | 0 (6) | 0 (6) | 0 (3) | |
| Dr,s | 0.010 | 0.022 | 0 | 0.046#** | |
| CP | Cr → t | 0.040 (13) | 0** (4§) | 0.113 (15) | 0.079 (15) |
| Ct → r | 0 (1) | 0 (2) | 0 (2) | 0 (4) | |
| Dr,t | 0.040# | 0** | 0.104# | 0.067# | |
| CV | Cs → t | 0.022 (9) | 0.118** (15§) | 0.017 (9) | 0 (6) |
| Ct → s | 0.035 (9) | 0.046* (9) | 0.017 (9) | 0.011 (8) | |
| Ds,t | 0 | 0.072#** | 0 | 0 | |
Values are the median over 15 subjects; values in brackets are the number of subjects (out of 15) for which non-zero causal coupling was found. *p < 0.05, **p < 0.005 up vs. su and sp vs. pa (paired test); #p < 0.005, directionality index D is different from zero (paired test); §p < 0.05, su vs. up or sp vs. pa (proportion test).