Autonomic Arousals as Surrogates for Cortical Arousals Caused by Respiratory Events: A Methodological Optimization Study in the Diagnosis of Sleep Breathing Disorders

Figures & data

Table 1 Demographic and Clinical Characteristics of the Studied Sample

	N=24
Age (mean ±SD)	48.4±15.6
Females (n, percentage)	10 (42%)
AHI with TST (mean ±SD)	11.6 ± 7.0
AHI with TRT (mean ±SD)	5.8 ± 4.9
AHI severity mild with TST (n, percentage)	14 (58%)
AHI severity moderate with TST (n, percentage)	10 (42%)
RDI (mean ±SD)	13.8 ± 7.9
ESS (mean ±SD)	8.3 ± 6.1
BMI (mean ±SD)	30.0 ± 7.6
Participants under antihypertensive drugs (n, percentage)	6 (25%)
Participants with previous or current cardiovascular diseases (n, percentage)	6 (25%)

Abbreviations: AHI, apnea-hypopnea index; TST, total sleep time; TRT, total recording time; RDI, respiratory disturbance index; ESS, Epworth sleepiness scale; BMI, body mass index.

Table 2 Description of the Scored Hypopneas and Respiratory Effort Related Arousals in Respect to Electroencephalogram Arousals from Twenty-Four Consecutive in-Laboratory Polysomnography Participants

	Type	Non-Desaturating Respiratory Events	Desaturating Respiratory Events (>3%)	Total
No EEG arousal	Central Apneas	24	29	53
	Hypopneas with aa	478	60	538
	Hypopneas	149	161	310
	Mixed Apneas	5	1	6
	Obstructive Apneas	38	41	79
	RERAs	27	1	28
	RERAs with aa	161	1	162
	Total	882	294	1176
EEG arousal	Central Apneas	17	42	59
	Hypopneas with aa	34	5	39
	Hypopneas	680	195	875
	Mixed Apneas	13	8	21
	Obstructive Apneas	55	75	130
	RERAs	310	12	322
	RERAs with aa	48	1	49
	Total	1157	338	1495
Both	Central Apneas	41	71	112
	Hypopneas with aa	512	65	577
	Hypopnea	829	356	1185
	Mixed Apnea	18	9	27
	Obstructive Apnea	93	116	209
	RERA	337	13	350
	RERA with aa	209	2	211
	Total	2039	632	2671

Note: In this table, autonomic arousal was defined as heart beat acceleration (HRa) of 5 or more after respiratory events, and sleep was scored by the American Association of Sleep Medicine criteria (AASM 2012).

Abbreviations: EEG, electroencephalography; RERA, respiratory effort-related arousal; aa, autonomic arousal.

Figure 1 Sensitivity and specificity calculated for the different heart rate acceleration (HRa) and pulse transit time (PTT) cut-offs calculated with total sleep time.

Table 3 Total Number of Non-Desaturating Hypopneas and RERAs Associated with EEG Arousals and Autonomic Arousals for the Twenty-Four Consecutive in-Laboratory Polysomnography Participants

	EEG Arousals	HRa 5 bpm	HRa 8 bpm	HRa 10 bpm	HRa 12 bpm	HRa 15 bpm	PTT −15 ms
Hypopneas	714	1311	1091	864	664	444	702
RERAs	358	537	471	409	343	232	229
Total	1072	1848	1562	1273	1007	676	931

Note: Bold values correspond to the cut-offs that agreed the best with the reference.

Abbreviations: EEG: electroencephalography; RERA: respiratory effort-related arousal; HR: heart rate acceleration; PTT: pulse transit time.

Table 4 Different Respiratory Disturbance Indexes Calculated with Autonomic Arousals with Total Sleep Time (TST) and Total Recorded Time (TRT) for the Twenty-Four Consecutive in-Laboratory Polysomnography Participants

		RDI e	RDI-HRa 5	RDI-HRa 8	RDI-HRa 10	RDI-HRa 12	RDI-HRa 15	RDI-PTT -15
TST	Mean	13.83	19.76	17.59	15.36	13.33	10.89	13.28
	SD	7.98	10.61	9.21	7.83	6.59	5.68	7.56
	Median	14.65	20.95	17.85	15.46	14.13	11.18	13.33
	Min	2.33	4.47	4.47	3.83	3.67	3.35	1.89
	Max	30.15	41.32	35.48	29.43	26.41	22.55	28.56
TRT	Mean	13.83	14.68	13.07	11.44	9.95	8.10	9.97
	SD	7.98	7.70	6.66	5.78	4.83	4.08	5.76
	Median	14.65	13.71	12.64	11.23	9.96	8.56	10.41
	Min	2.33	4.06	4.06	3.48	3.33	2.98	1.67
	Max	30.15	30.97	28.74	26.75	23.41	19.69	22.05

Note: Bold values correspond to the cut-offs values that agreed the best with the reference.

Abbreviations: RDI-HRa (x), respiratory disturbance index using a heart rate acceleration of x beats per minute; RDI-PTT (x), respiratory disturbance index using a pulse transit time reduction of x msec; RDIe, respiratory disturbance index.

Table 5 Means and 95% Confidence Intervals Sensitivity and Specificity Values for the Different Heart Rate Acceleration (HRa) and Pulse Transit Time (PTT) Cut-Offs Calculated with Total Sleep Time

	Cut-off	Sensitivity	Specificity
HRa	5	97.5 (96.4–98.3)	1.5 (0.8–2.6)
	8	86.4 (84.2–88.4)	22.0 (19.2–25.0)
	10	74.3 (71.5–76.9)	41.5 (38.1–44.9)
	12	61.5 (58.5–64.4)	57.3 (53.8–60.7)
	15	44.9 (41.9–47.9)	76.1 (73.0–79.0)
PTT	−20	47.6 (44.6–50.6)	74.5 (71.3–77.4)
	−15	61.9 (59.0–64.9)	57.7 (54.2–61.1)
	−10	78.5 (76.0–81.0)	38.3 (34.9–41.7)
	−5	89.9 (88.0–91.7)	16.8 (14.3–19.6)

Note: Bold values correspond to the cut-offs values that agreed the best with the reference.

Figure 2 Bland–Altman plot demonstrating the mean difference between RDI-HRa10 vs RDIe in total sleep time (top) and RDI-HRa5 vs RDIe in total recorded time (bottom).

Table 6 Bland–Altman Analyses Comparing Different Cut-Offs for Autonomic Arousals to RDIe

		RDI-HRa 5	RDI-HRa 8	RDI-HRa 10	RDI-HRa 12	RDI-HRa 15	RDI-PTT -15
TST	Mean diff	5.93	3.76	1.53	−0.49	−2.94	−0.55
	Mean diff −2SD	−2.15	−3.02	−5.42	−8.17	−11.89	−7.45
	Mean diff+ 2SD	14.01	10.55	8.47	7.18	6.01	6.35
	ICC	0.76	0.84	0.89	0.86	0.72	0.90
	Pearson R^2	0.88	0.86	0.81	0.76	0.69	0.81
TRT	Mean diff	0.86	−0.76	−2.38	−3.88	−5.72	−4.26
	Mean diff −2SD	−6.18	−8.11	−11.08	−13.56	−16.32	−1.77
	Mean diff+ 2SD	7.89	6.59	6.31	5.81	4.87	3.25
	ICC	0.89	0.87	0.76	0.62	0.46	0.73
	Pearson R^2	0.80	0.78	0.70	0.66	0.62	0.88

Note: Bold values correspond to the cut-offs values that agreed the best with the reference.

Abbreviations: RDI-HRa (x), respiratory disturbance index using a heart rate acceleration of x beats per minute; RDI-PTT (x), respiratory disturbance index using a pulse transit time reduction of x msec; RDIe, respiratory disturbance index; ICC, intraclass coefficient of correlation.