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

Table 3 Comparison of the RR HF-CDM parameters between the two groups of patients (unstable vs stable) at PEEP 10.

RR series	Parameters	Unstable group (n = 11)	Stable group (n = 12)	p value
Raw RR	mean value (ms)	777 (613-911)	551 (473-600)	0.004
HF-CDM amplitude	mean value (ms)	3.04 (1.91-7.17)	1.33 (1.10-1.98)	0.007
	lnHF/RR (ms/s)	1.42 (0.80-2.18)	0.54 (0.15-1.28)	0.05
	SD (ms)	1.21 (0.81-2.03)	0.14 (0.09-0.30)	0.001
	time below threshold^a (%)	8.37 (4.50-11.92)	0.00 (0.00-0.00)	0.001
HF-CDM phase	SD (rad)	0.80 (0.35-2.42)	0.13 (0.08-0.22)	0.001
	maximal drift (rad)	2.76 (0.78-6.17)	0.44 (0.29-0.679)	0.001

All results were reported as means ± SEM when normality has been checked, as median (25-75 percentile) values otherwise. ^a: percentage of time spent with HF amplitude below 50% of the mean HF amplitude for the individual patient. For each patient, the resulting parameter values were the average of the beat-to-beat values over the analysis period. Mean RR and HF amplitude were lower in the stable group. The two parameters related to the variability of HF amplitude (standard-deviation and time spent below the threshold of amplitude) were lower in this group, reflecting a more stable HF amplitude over time. The two parameters related to the variability of the HF-RR/ventilation phase difference (standard-deviation and maximal drifts) were lower in the stable group, reflecting a more stable RR/ventilation phase difference over time.

ISSN: 1465-993X