Positive End-Expiratory Pressure may alter breathing cardiovascular variability and baroreflex gain in mechanically ventilated patients

Table 2 Comparison of the spectral gain parameters between the two groups of patients (unstable vs stable) at PEEP 10.

Spectral components	Unstable group (n = 11)	Stable group (n = 12)	p value
HF-RR spectral density (ms²)	6328 (2277-29222)	722 (457-1798)	0.003
HF-SBP spectral density (mmHg²)	1048 (496-4279)	1963 (851-3613)	0.3
Spectral gain (ms/mmHg)	3.03 (1.18-6.16)	0.59 (0.33-1.42)	0.01
Spectral coherence (0-1)	0.81 ± 0.02	0.93 ± 0.01	0.001
% time with coherence < 0.5	33.33 (20.64- 42.60)	0.00 (0.00-7.07)	0.006

All results were reported as means ± SEM when normality has been checked, as median (25-75 percentile) values otherwise. For each patient, the resulting spectral components values (except the last line, % time with coherence < 0.5) were the mean of the successive 16-second epoch values, when the spectral coherence between RR and SBP was greater than 0.5, allowing the gain analysis. The gain value was lower in the stable group, due to the decrease in HF-RR spectral density, whereas the spectral coherence was greater and the percentage of time with coherence < 0.5 was lower.

ISSN: 1465-993X