Association of Obstructive Apnea with Thoracic Fluid Shift and Small Airways Narrowing in Asthma During Sleep

Figures & data

Table 1 Participant Demographics and Lung Function

	OSA (n = 9)	Non-OSA (n = 10)	p value
Sex (male/female)	7/2	5/5	Chi^2, p=0.21
Age, years	61.2±8.1	44.1±12.9	0.003
Height, cm	170.9±7.8	165.9±8.2	0.19
Weight, kg	83.9±6.5	71.0±7.6	0.001
BMI, kg/m^2	28.9±3.2	25.8±2.5	0.03
Right leg length, cm	66.4±4.8	63.6±3.4	0.22
Thoracic length, cm	23.0±2.0	21.4±6.0	0.47
ACQ	0.47±0.32	0.59±0.25	0.44
ACT	22.71±3.25	23.14±1.95	0.77
Lung function, seated
FEV1, L	2.3±0.6	2.4±0.9	0.73
FVC, L	3.4±1.0	3.9±1.5	0.48
FEV1, % predicted	76.5±3.7	76.1±23.0	0.96
FVC, % predicted	87.7±9.3	95.5±25.6	0.50
FEV1/FVC	67.6±5.1	62.9±5.9	0.16
Fluid volumes, supine in the evening
Baseline LFV, mL	3065±344	2417±420	0.001
Baseline TFV, mL	2489±600	2168±601	0.26
Respiratory impedance, supine in the evening
Baseline X5, cmH2O/L/s	−3.58±2.04	−3.43±2.56	0.89
Baseline AX, cmH2O/L	29.62±23.47	32.28±39.16	0.86
Baseline R5, cmH2O/L/s	6.89±2.51	5.67±2.12	0.28
Baseline R5-19, cmH2O/L/s	1.98±1.42	1.49±1.19	0.43
Baseline Fres, cmH2O/L/s	24.31±7.20	24.21±7.10	0.97

Notes: p values are calculated based on unpaired t-tests for all variables except sex, for which the chi-square test was used. Bold text indicated p < 0.05. Values are mean ± SD.

Abbreviations: ACQ, Asthma Control Questionnaire; ACT, Asthma Control Test; FEV₁, forced expiratory volume in 1 sec, FVC, forced vital capacity; LFV, leg fluid volume; TFV, thoracic fluid volume; X₅, respiratory system reactance at 5 Hz; A_X, reactance area; R₅, respiratory system resistance at 5 Hz; R_5-19, frequency dependence of resistance; F_res, resonance frequency.

Table 2 Sleep Characteristics

	OSA	Non-OSA	p
TST, min	278.5 ± 68.6	340.3 ± 60.6	0.052
Sleep Efficiency, %	73.4 ± 15.9	82.1 ± 10.9	0.18
REM sleep, %	13.9 ± 6.8	16.2 ± 6.2	0.45
Oxygen desaturation index	17.9 ± 9.2	2.3 ± 1.9	<0.001
Arousal index	28.3 ± 14.0	18.2 ± 6.3	0.06
Total apnea-hypopnea time, min	27.1 ± 16.5	10.3 ± 7.3	0.01
AHI, events/hr	21.4 ± 12.8	5.8±2.8	0.001

Note: Bold text indicated p < 0.05.

Abbreviations: TST, total sleep time; REM, rapid eye movement.

Figure 1 Changes in leg fluid volumes (ΔLFV) and thoracic fluid volumes (ΔTFV) in the OSA group (black lines) and non-OSA group (grey lines) ((A and B), respectively) from pre-sleep to post-sleep measurements. Each line represents an individual participant. P values for comparisons between groups are based on analysis of covariance, adjusted for age, BMI and sex. Bars on either side of data lines represent group mean value with SD.

Figure 2 Changes in respiratory system reactance at 5 Hz (X₅), reactance area (A_X), total respiratory system resistance at 5 Hz (R₅), frequency dependence of resistance (R_5-19), and resonant frequency (Fres) in the OSA group (black lines) and non-OSA group (grey lines) (A–E, respectively) from pre-sleep to post-sleep measurements. Each line represents an individual participant. P values for comparisons between groups are based on analysis of covariance, adjusted for age, BMI and sex. Bars on either side of data lines represent group mean value with SD. More negative X₅ indicates greater small airways resistance.