Physiologic Correlates of Sleep Quality in Severe Emphysema

Figures & data

Figure 1.  Protocol for testing patients. PFT = pulmonary function test; ABG = arterial blood gas; LZAP = length of the zone of apposition of the diaphragm.

Table 1.  Baseline Characteristics of Patients (N = 25)^*

Variable	Value
Female/male gender	11/14
Age, yrs	64 ± 6
BMI, kg/m^2	24.7 ± 4.2
Home Oxygen, No. (FIO2 L/min)	13 (2 ± 0.6)
FEV1, L (% predicted)	0.8 ± 0.3 (28 ± 8)
FVC, L (% predicted)	2.5 ± 0.8 (69 ± 15)
TLC, L (% predicted)	7.1 ± 1.3 (125 ± 14)
FRC, L (% predicted)	5.4 ± 1.2 (175 ± 31)
RV, L (% predicted)	4.6 ± 1.1 (216 ± 49)
DLCO, ml/mm Hg/min (% predicted)	4.0 ± 0.9 (31 ± 14)
PaCO2, mmHg	43 ± 5
PaO2, mmHg	63 ± 8
LZAP, cm	3 ± 1
Mean nocturnal SaO2,%	90 ± 5
Lowest nocturnal SaO2,%	83 ± 8
% Total sleep time SaO2 < 90%	29 ± 40
Total Sleep Time, min	227 ± 93
Sleep Efficiency,%	56 ± 21
Arousal Index, arousals/hr	11 ± 5
Apnea-Hypopnea index, events/hr	1 ± 2
Sleep Architecture (% TST)
Stage N 1	15 ± 12
Stage N 2	65 ± 13
Stage N 3	2 ± 3
REM	18 ± 13
Medication (Number of patients)
Albuterol	23
Ipratropium	25
Levalbuterol	2
Salmeterol	4
Fluticasone	6
Budesonide	1
Fluticasone/salmeterol	3
Triamcinolone	3
Theophylline	13

^*Data presented as the mean ± SD unless otherwise indicated. LZAP – length of the zone of apposition of the diaphragm, BMI – body mass index.

Figure 2.  There was a positive correlation between both total sleep time and sleep efficiency and the length of the zone of apposition of the diaphragm (LZAP) (r = 0.5, p = 0.01 and r = 0.5, p = 0.01, respectively).

Table 2.  Pearson correlation coefficients between physiological variables and measurements of sleep quality

Variable	TST	Sleep Efficiency
FEV1,% predicted	0.45^*	0.47^*
FVC,% predicted	0.43^*	0.37
TLC,% predicted	0.07	0.01
RV,% predicted	−0.40^*	−0.44^*
LZAP, cm	0.52^**	0.54^**
DLCO,% predicted	0.39^*	0.44^*
PaO2, mm Hg	0.14	0.06
Mean SaO2,%	0.23	0.15
Lowest SaO2,%	0.10	0.05
% TST SaO2 < 90%	−0.24	−0.14
% REM SaO2 < 90%	−0.12	−0.10

TST – total sleep time, FEV₁ – forced expiratory volume in 1 sec, FVC – forced vital capacity, TLC – total lung capacity, RV – residual volume, LZAP – length of the zone of apposition of the diaphragm, DLCO – diffusion capacity of carbon monoxide, REM – rapid eye movement,

^*p < 0.05. ^**p < 0.01.

Table 3.  Multiple linear regression analyses of Total Sleep Time (TST) and Sleep Efficiency (SE)

Independent Variable	Regression Coefficient	Standard Error	P
Dependent variable: TST^*
LZAP	87.6	23.4	0.001
Mean SaO2	22.1	7.4	0.007
Lowest SaO2	−14.4	5.2	0.011
Constant	−836.6
Standard error of the estimate = 71.6
Multiple correlation coefficient (r) = 0.703 r^2 = 0.494
Dependent Variable: SE^†
LZAP	20.6	5.8	0.002
Mean SaO2	4.0	1.8	0.039
Lowest SaO2	−2.8	1.3	0.041
Constant	−138.1
Standard error of the estimate = 17.6
Multiple correlation coefficient (r) = 0.657 r^2 = 0.432

^*Regression equation: predicted TST = −836.562 + (87.597 × LZAP) + (22.077 × mean SaO₂) – (14.351 × lowest SaO₂).

^†Regression equation: predicted SE = −138.071 + (20.581 × LZAP) + (4.007 × mean SaO₂) – (2.762 × lowest SaO₂).