Cardiorespiratory coupling is influenced by body position and slow paced 0.1Hz breathing in a state specific manner
Authors: Bojić Tijana , Matić Zoran , Stojković Mihajlo , Platiša Mirjana , Kalauzi Aleksandar , Lazarević Mihailo , Moser Maximilian 
Published: October 2020

Cardiorespiratory coupling (CRC), a set of cardiac and respiratory rhythms that optimise the body oxygenation and the adaptability of the cardiorespiratory system to the external and internal environment, is represented in the linear domain by coefficient Qpr, the number of heartbeats per respiratory cycle (1, 2). Slow 0.1Hz breathing in supine position (Supin01) and active standing (Stand) represent the states of maximal RRI vagal and sympathetic modulation, respectively, in physiological quiescence; standing with 0.1Hz breathing (stand01) is characterized by qualitatively specific pattern of CRC(3).
The aim of our work was to investigate the Qpr in 4 states: supine position with spontaneous breathing (supin), stand, supin01and stand01.

Methods: The ECG (RRI) and respiration signals were simultaneously recorded in 20 healthy human subjects in four conditions. Data acquisition and processing was performed as in (3).

Results:

Parameter

Supin (mean95%CI)

Stand(mean95%CI)

Supin01(mean95%CI)

Stand01(mean95%CI)

RRI [s]
0.980.13
0.720.10
1.060.13
0.750.09

sd

RRI [s]
0.060.02
0.040.02
0.090.03
0.070.02

BBI [s]
4.681.53
4.581.80
9.850.71
9.950.20

sdBBI [s]
1.110.69
1.351.29
1.440.94
1.060.44

Qpr

4.811.67
6.392.43
9.411.20
13.481.66

sdQpr

1.140.67
1.931.73
1.390.71
1.540.53

Table

1. Mean value and 95%CI of RRI, BBI and Qpr for 20 healthy subjects in four physiological states: Supin-supine position with spontaneous breathing, Stand- standing with spontaneous breathing, Supin01-supine position with 0.1Hz breathing, Stand01-standing with slow 0.1Hz breathing.
Parameter

Supin-Stand

Supin-Supin01

Supin-Stand01

Supin01-Stand01

RRI

0.000

0.0

04

0.000

0.000

sd

RRI

0.0

04

0.00

0

0.351

0.0

10

BBI

0.391

0.000

0.000

0.313

sdBBI

0.232
0.433
0.911
0.135

Qpr

0.0

00

0.000

0.000

0.000

sdQpr

0.0

06

0.370

0.0

33

0.191

Table 2. Probability values ​​(p) of statistically significant differences between different physiological states. Wilcoxon test on a sample of 20 subjects. Color-indicated statistically significant changes in values ​​(p <0.05) whose changes were related and discussed. - increase of mean value, -decrease of mean value.
Our results show that Qpr is state dependent and that it increases with the behavioral task complexity. Postural change tunes Qpr by RRI modulation, while 0.1Hz breathing dominantly by the increase of BBI. Stand01 is characterized by concomitant adjustment of both RRI and BBI. These data imply that Qpr regulation is "loosely" and selectively coordinated in stand and supin01("dual control") while integrated in stand01 ("unitary control"(4)). Analogously to nonlinear CRC(3), Qpr is probably operated by hierarchically higher diencephalo-telencephalic autonomic networks.
References:
1. Moser M et al, Biol Rhythm Res 1995;26(1):100-111.
2. Scholkmann F et al, Front Physiol 2019;10:371.
3. Matić Z et al, Front Physiol 2020;11:24.
4. Feldman JL et al, Annu Rev Physiol 1988;50,593606.