. 2022 May 12;600(11):2669–2689. doi: 10.1113/JP282327

Table 2.

Baroreflex sensitivity and heart rate variability during eucapnia, isocapnic hypoxia, hypercapnic hyperoxia and hypercapnic hypoxia in women and men

						ANOVA P values
		Eucapnia	Isocapnic hypoxia	Hypercapnic hyperoxia	Hypercapnic hypoxia	Sex	Trial	Interaction
*ABR‐MSNA*
Burst incidence (bursts [100 heartbeats]⁻¹·mmHg⁻¹)	Women	−4.14 ± 1.45	−3.25 ± 1.20	−4.05 ± 1.90	−3.24 ± 2.11	0.903	0.076	0.881
Burst incidence (bursts [100 heartbeats]⁻¹·mmHg⁻¹)	Men	−3.80 ± 1.54	−3.47 ± 1.59	−4.51 ± 1.84	−3.35 ± 2.01
Total MSNA (a.u.·beat⁻¹·mmHg⁻¹)	Women	−2.50 ± 0.81	−2.45 ± 1.01	−4.42 ± 2.34	−3.35 ± 2.07	0.525	0.010	0.758
Total MSNA (a.u.·beat⁻¹·mmHg⁻¹)	Men	−2.21 ± 1.00	−2.67 ± 1.15	−3.61 ± 2.19	−3.24 ± 1.49		^b , ^d
*cBRS*
Gain (ms·mmHg⁻¹)	Women	15.6 ± 5.0	10.7 ± 4.5	14.4 ± 6.1	12.0 ± 6.0	0.763	0.045	0.211
	Men	14.2 ± 5.2	14.7 ± 14.9	19.5 ± 10.1	14.1 ± 10.2		^f
Number of sequences (n)	Women	33 ± 20	33 ± 18	18 ± 17	25 ± 18	0.154	<0.0001	0.861
Number of sequences (n)	Men	23 ± 17	21 ± 18	10 ± 7	8 ± 11		^b , ^c , ^d , ^e
BEI (%)	Women	0.57 ± 0.32	0.53 ± 0.26	0.35 ± 0.25	0.26 ± 0.15	0.503	<0.0001	0.738
	Men	0.50 ± 0.25	0.38 ± 0.33	0.35 ± 0.28	0.19 ± 0.11		^b , ^c , ^e
*HRV*
RMSSD (ms)	Women	73.1 ± 41.2	39.1 ± 15.8	82.5 ± 39.3	51.0 ± 31.0	0.744	<0.0001	0.332
	Men	69.2 ± 34.9	51.5 ± 24.3	69.1 ± 44.3	40.6 ± 25.7		^a , ^c , ^d , ^f
SDNN (ms)	Women	77.8 ± 31.4	54.5 ± 21.0	76.4 ± 27.6	58.6 ± 21.5	0.549	<0.0001	0.198
	Men	76.2 ± 31.3	60.7 ± 21.1	62.1 ± 23.6	46.1 ± 19.8		^a , ^c , ^f
HF (ms²)	Women	3223 ± 4205	703 ± 456	3457 ± 2867	1425 ± 1761	0.403	0.009	0. 256
	Men	2560 ± 2170	1653 ± 1739	1785 ± 1520	741 ± 848		^a , ^c
LF (ms²)	Women	2159 ± 1948	790 ± 1520	866 ± 1364	480 ± 772	0.986	<0.0001	0.917
	Men	2057 ± 1909	1061 ± 1334	709 ± 497	443 ± 522		^a , ^b , ^c
Total power	Women	4874 ± 4908	1251 ± 1769	3014 ± 3979	1175 ± 2394	0.738	<0.0001	0.178
	Men	4674 ± 3971	2115 ± 4072	2335 ± 1840	990 ± 1353		^a , ^c
HF (n.u.)	Women	60 ± 27	59 ± 19	77 ± 16	62 ± 21	0.403	0.061	0.589
	Men	58 ± 22	61 ± 21	66 ± 18	52 ± 22
LF (n.u.)	Women	40 ± 27	41 ± 19	23 ± 16	38 ± 21	0.403	0.061	0.589
	Men	42 ± 22	39 ± 21	34 ± 18	48 ± 22
LF/HF ratio	Women	2.62 ± 4.78	1.51 ± 1.96	0.49 ± 0.59	1.40 ± 1.69	0.923	0.209	0.681
	Men	1.67 ± 2.35	1.22 ± 1.53	0.85 ± 0.95	2.06 ± 1.89

All variables are n = 10 women and n = 10 men, aside from ABR‐MSNA where n = 9 women and n = 9 men (due to slopes R ²<0.45) and cBRS where n = 7 women and n = 8 men (due to an absence of sequences). The main effects of sex, breathing trial and their interaction were examined using mixed model ANOVA with repeated measures. ABR‐MSNA, arterial baroreflex control of MSNA; MSNA, muscle sympathetic nerve activity; cBRS, spontaneous cardiac baroreflex sensitivity; BEI, baroreflex effectiveness index; HRV, heart rate variability; RMSSD, square root of the mean of the sum of successive differences in R–R interval; SDNN, standard deviation of all normal sinus R–R intervals; HF, high frequency; n.u., normalized units; LF, low frequency. Where a significant main effect of trial, but no interaction, is observed, differences identified during post hoc analysis (t tests with Bonferroni correction) are shown as

^{^a}

P < 0.05 eucapnia vs. isocapnic hypoxia,

^{^b}

P < 0.05 eucapnia vs. hypercapnic hyperoxia,

^{^c}

P < 0.05 eucapnia vs. hypercapnic hypoxia,

^{^d}

P < 0.05 isocapnic hypoxia vs. hypercapnic hyperoxia,

^{^e}

P < 0.05 isocapnic hypoxia vs. hypercapnic hypoxia,

^{^f}

P < 0.05 hypercapnic hyperoxia vs. hypercapnic hypoxia.