Instability of nocturnal parasympathetic nerve function in patients with chronic lung disease with or without nocturnal desaturation

Figures & data

Table 1 Characteristics and results of pulmonary function test and arterial blood gas analysis in healthy elderly subjects (control group) and chronic lung disease patients with ventilatory disturbance with and without NOD (NOD group and non-NOD group, respectively), and who have been treated with LTOT (LTOT group)

	Control	non-NOD	NOD	LTOT
Number	17	17	12	13
COPD, n		12	10	8
CPFE, n		1	1	2
IP, n		2	0	2
BE, n		2	1	1
Age, years	65.3±1.7	77.0±2.3**	76.4±3.3**	77.2±2.2**
Sex, male/female	15/2	15/2	12/0	13/0
BMI, kg/m^2	23.4±0.7	22.5±0.9	20.6±1.0*	21.7±0.9
FVC, %	103.2±1.8	98.7±6.0	93.1±6.2	73.4±5.1**,##,§
FEV1, %	97.6±2.3	74.2±4.2**	54.8±6.1**,#	45.4±5.5**,##
FEV1/FVC, %	78.6±1.7	61.9±3.6**	46.2±4.3**,#	51.0±6.8**
FRC, %		102.0±5.7	103.8±7.1	122.4±12.3
RV, %		142.5±13.2	171.7±19.7	203.0±30.9
TLC, %		113.8±6.0	118.3±7.0	121.1±10.9
RV/TLC, %		43.8±2.6	48.4±3.7	54.8±4.3#
DLCO, %		67.7±4.9	46.6±4.4##	34.1±3.1##
PaO2, Torr		75.9±2.5	66.0±2.4#	72.6±3.6
PaCO2, Torr		38.4±1.0	36.6±1.8	42.4±1.3#,§
HCO3^−, mmol/L		24.6±0.4	24.0±0.9	26.5±0.7#

Notes: Values are means ± SEM.

* P<0.05 and

** P<0.01 vs control subjects;

# P<0.05 and

## P<0.01 vs non-NOD;

§ P<0.05 vs NOD. NOD was defined as CT90 ≥3%.

Abbreviations: CPFE, combined pulmonary fibrosis and emphysema; IP, interstitial pneumonia; BE, bronchiectasis; BMI, body mass index; FRC, functional residual capacity; RV, residual volume; TLC, total lung capacity; DLCO, carbon monoxide diffusing capacity; LTOT, long-term oxygen therapy; NOD, nocturnal oxygen desaturation; SEM, standard error of means; CT90, cumulative time with SpO₂ <90%.

Table 2 Results of nocturnal respiratory events, oxygen desaturation, and autonomic nerve function in healthy elderly subjects (control) and chronic lung disease patients with ventilatory disturbance with and without NOD (NOD group and non-NOD group, respectively), and who have been treated with LTOT (LTOT group)

	Control	non-NOD	NOD	LTOT
Number	17	17	12	13
REI, events/h	8.9±0.9	18.4±3.0*	12.9±2.1	11.5±1.9
REI ≥15 events/h, n (%)	0 (0)	9 (52.9)	6 (50.0)	5 (38.5)
Mean SpO2, %	94.9±0.4	95.5±0.4	91.2±0.5**,##	96.7±0.4**,§§
Lowest SpO2, %	86.1±1.3	87.9±1.1	76.8±2.5**,##	89.5±1.1*,§§
CT90, %	2.5±1.0	0.8±0.2	27.7±6.0**,##	0.4±0.2*,§§
3% ODI, events/h	7.7±1.5	4.4±2.1*	11.0±2.5##	1.1±0.3**,§§
4% ODI, events/h	4.7±1.0	3.2±1.6	6.5±1.6##	0.5±0.2**,§§
LF/HF ratio	0.97±0.06	0.96±0.09	0.88±0.09	0.74±0.04**
HFamp, ms	21.8±1.9	27.1±4.2	20.7±1.8	24.0±2.1
HF20sec, %	51.7±4.0	25.9±2.9**	15.2±1.9**,##	32.2±5.0**,§§
HF5min, %	19.5±3.8	2.5±1.2**	0.2±0.1**	2.9±1.7**

Notes: Values are means ± SEM.

* P<0.05 and

** P<0.01 vs control subjects;

# P<0.05 and

## P<0.01 vs non-NOD;

§ P<0.05 and

§§ P<0.01 vs NOD. NOD was defined as CT90 ≥3%.

Abbreviations: REI, respiratory event index; CT90, cumulative time with SpO₂ <90%; ODI, oxygen desaturation index; LF, low frequency; HF, high frequency; LF/HF ratio, a marker of sympathetic nerve activity; HFamp, mean HF amplitude (a marker of parasympathetic nerve activity); HF_20sec and HF_5min, the relative times over which the same main HF peak was sustained for at least 20 seconds and 5 minutes in total recording time (markers of stability of parasympathetic nerve function); LTOT, long-term oxygen therapy; NOD, nocturnal oxygen desaturation; SEM, standard error of means.

Figure 1 Comparison of sympathetic (A) and parasympathetic (B) activity among healthy elderly subjects (control), CLD patients with NOD and without NOD (non-NOD), and CLD patients treated with LTOT.

Note: **P<0.01 vs control.

Abbreviations: LF, low frequency; HF, high frequency; LF/HF ratio, an index of sympathetic nerve activity; HF amplitude, an index of parasympathetic nerve activity; NOD, nocturnal oxygen desaturation; LTOT, long-term oxygen therapy; CLD, chronic lung disease.

Figure 2 Comparison of indexes of stability of parasympathetic nerve function, %HF_20sec (A) and %HF_5min (B), among healthy elderly subjects (control), CLD patients with NOD and without NOD (non-NOD), and CLD patients treated with LTOT.

Notes: **P<0.01 vs control; ^##P<0.01 vs non-NOD; ^§§P<0.01 vs NOD.

Abbreviations: %HF_20sec and %HF_5min, the relative times over which the same main high-frequency peak was sustained for at least 20 seconds and 5 minutes in total recording time (markers of stability of parasympathetic nerve function); CLD, chronic lung disease with irreversible pulmonary dysfunction and mild-to-moderate daytime hypoxemia; NOD, nocturnal oxygen desaturation defined as CT90 ≥3%; CT90, cumulative time with SpO₂ <90%; LTOT, long-term oxygen therapy.

Figure 3 Relationship between %HF_20sec, an index of stability of parasympathetic nerve function, and CT90 (A) or PaO₂ (B).

Abbreviations: CT90, cumulative time with SpO₂ <90%; %HF_20sec, the relative time over which the same main HF peak was sustained for at least 20 seconds in total recording time (an index of stability of parasympathetic nerve function); HF, high frequency.