Continuous Positive Airway Pressure Therapy Reduces Oxidative Stress Markers and Blood Pressure in Sleep Apnea–Hypopnea Syndrome Patients

Abstract

Sleep apnea-hypopnea syndrome (SAHS) is characterized by recurrent episodes of hypoxia/reoxygenation, which seems to promote oxidative stress. SAHS patients experience increases in hypertension, obesity and insulin resistance (IR). The purpose was to evaluate in SAHS patients the effects of 1 month of treatment with continuous positive airway pressure (CPAP) on oxidative stress and the association between oxidative stress and insulin resistance and blood pressure (BP). Twenty-six SAHS patients requiring CPAP were enrolled. Measurements were recorded before and 1 month after treatment. Cellular oxidative stress parameters were notably decreased after CPAP. Intracellular glutathione and mitochondrial membrane potential increased significantly. Also, total antioxidant capacity and most of the plasma antioxidant activities increased significantly. Significant decreases were seen in BP. Negative correlations were observed between SAHS severity and markers of protection against oxidative stress. BP correlated with oxidative stress markers. In conclusion, we observed an obvious improvement in oxidative stress and found that it was accompanied by an evident decrease in BP with no modification in IR. Consequently, we believe that the decrease in oxidative stress after 1 month of CPAP treatment in these patients is not contributing much to IR genesis, though it could be related to the hypertension etiology.

Full text

Continuous Positive Airway Pressure Therapy Reduces
Oxidative Stress Markers and Blood Pressure in Sleep
Apnea–Hypopnea Syndrome Patients
Mora Murri &Regina García-Delgado &José Alcázar-Ramírez &
Luis Fernández de Rota &Ana Fernández-Ramos &Fernando Cardona &
Francisco J. Tinahones
Received: 22 December 2010 / Accepted: 12 January 2011 /
Published online: 1 February 2011
#Springer Science+Business Media, LLC 2011
Abstract Sleep apnea–hypopnea syndrome (SAHS) is characterized by recurrent episodes
of hypoxia/reoxygenation, which seems to promote oxidative stress. SAHS patients
experience increases in hypertension, obesity and insulin resistance (IR). The purpose was
to evaluate in SAHS patients the effects of 1 month of treatment with continuous positive
airway pressure (CPAP) on oxidative stress and the association between oxidative stress
and insulin resistance and blood pressure (BP). Twenty-six SAHS patients requiring CPAP
were enrolled. Measurements were recorded before and 1 month after treatment. Cellular
oxidative stress parameters were notably decreased after CPAP. Intracellular glutathione and
mitochondrial membrane potential increased significantly. Also, total antioxidant capacity
and most of the plasma antioxidant activities increased significantly. Significant decreases
were seen in BP. Negative correlations were observed between SAHS severity and markers
of protection against oxidative stress. BP correlated with oxidative stress markers. In
conclusion, we observed an obvious improvement in oxidative stress and found that it was
accompanied by an evident decrease in BP with no modification in IR. Consequently, we
believe that the decrease in oxidative stress after 1 month of CPAP treatment in these
Biol Trace Elem Res (2011) 143:1289–1301
DOI 10.1007/s12011-011-8969-1
M. Murri (*):F. Cardona
Laboratorio de Investigaciones Biomédicas, Fundación IMABIS,
Hospital Clínico Universitario Virgen de la Victoria, 29010 Málaga, Spain
e-mail: moramurri@gmail.com
R. García-Delgado :A. Fernández-Ramos
Servicio de Hematología, Hospital Clínico Universitario Virgen de la Victoria, 29010 Málaga, Spain
J. Alcázar-Ramírez :L. Fernández de Rota
Servicio de Neumología, Hospital Clínico Universitario Virgen de la Victoria, 29010 Málaga, Spain
F. Cardona :F. J. Tinahones
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBER CB06/003),
Instituto de Salud Carlos III, 29010 Málaga, Spain
F. J. Tinahones
Servicio de Endocrinología y Nutrición, Hospital Clínico Universitario Virgen de la Victoria, 29010
Málaga, Spain

patients is not contributing much to IR genesis, though it could be related to the
hypertension etiology.
Keywords Continuous positive airway pressure .Hypertension .Insulin resistance .
Oxidative stress .Sleep apnea–hypopnea syndrome
Introduction
The sleep apnea–hypopnea syndrome (SAHS) is characterized by recurrent episodes of airflow
limitation in the upper airway during sleep. These episodes induce a decrease in oxy-
haemoglobin saturation and frequent micro-awakenings that lead to a restless sleep, excessive
daytime sleepiness, and cardiovascular, respiratory and neuropsychiatric disorders. Conse-
quently, SAHS has been considered an independent risk factor for hypertension [1]. However,
the mechanisms underlying these disorders in SAHS patients are not completely understood.
During the phenomenon of hypoxia/reoxygenation that occurs in SAHS patients, the
generation of reactive oxygen species (ROS) is increased, leading to mitochondrial
dysfunction [2]. These alterations activate inflammatory transcription factors that are
involved in the regulation of inflammatory cytokines and adhesion molecules. ROS
production can occur via an activated inflammatory response induced by hypoxia [3], as
well as by an increased sympathetic tone and elevated catecholamine production [4].
It is well known that ROS overproduction may induce oxidation and functional alterations in
a variety of biological molecules. These alterations can be normalized by antioxidant systems [5],
which neutralize the oxidative burst in order to maintain cell redox balance. Redox imbalance
induces activation of signaling pathways, altering cell functions, and leading to a variety of
diseases [6], depending on the cell and tissue types involved and the site of production of ROS.
Insulin resistance (IR) has been reported to be increased in SAHS patients [7], though
the causative mechanisms are not clear. Possible reasons include various SAHS parameters
[8], the degree of obesity [9], and also the presence of increased sympathetic drive. Some
authors have suggested that many factors leading to IR are mediated via the generation of
abnormal amounts of ROS [10].
The standard therapy for SAHS is continuous positive airway pressure (CPAP) [11].
Constant CPAP use improves quality of life and attenuates daytime sleepiness. Some
authors have registered an improvement in hypertension and IR in patients with SAHS after
CPAP treatment [12] while others have not [13].
In summary, SAHS seems to be associated with oxidative stress and an increased
prevalence of cardiovascular and metabolic diseases, including hypertension and insulin
resistance. The purpose of the present study was to evaluate in SAHS patients the effects of
1 month of treatment with CPAP on oxidative stress parameters, and the association
between oxidative stress and IR or blood pressure.
Methods
Ethics Statement
The study was approved by the Ethics Committee of the Virgen de la Victoria Hospital, and all
the participants provided signed consent after being fully informed of its goal and characteristics.
1290 Murri et al.

Study Subjects
The study included 26 men with SAHS who required nasal CPAP, according to established
criteria [14]. Diabetic patients who required insulin were excluded, as were patients who
failed to complete 1 month of treatment or whose weight changed by more than 1.5 kg
during the study.
Sixteen healthy men, blood donors, were recruited as a control group. They had no
personal or family history of cardiovascular disease, dyslipidaemia or diabetes. In
these subjects, the diagnosis of SAHS was excluded by overnight polysomnography
(Alice5; Respironics).
Study Design
The study design was a prospective observational study.
The subjects completed a structured interview to obtain the following data: age, medical
history, and current diseases. The following data were also collected: weight, height, waist
and neck circumference, body mass index, and blood pressure (BP). The subjects also
completed the Epworth Sleepiness Scale (ESS) questionnaire, for the evaluation of daytime
sleepiness, before and 1 month after treatment.
Methods
Polysomnography
The diagnosis of SAHS was established by overnight polysomnography (Alice5;
Respironics), which included continuous recording of oronasal flow, thoracoabdominal
movements, electrocardiography, submental and pretibial electromyography, electrooculog-
raphy, electroencephalography, and arterial oxygen saturation. Apnea was defined as the
absence of airflow for more than 10 s. Hypopnea was defined as a 50% reduction in airflow
for more than 10 s that resulted in arousal or oxyhaemoglobin desaturation. The oxygen
desaturation index (ODI) was defined as the number of oxygen desaturation=4%/h. The
apnea–hypopnea index (AHI) was defined as the sum of the numbers of apneas and
hypopneas per hour of sleep. SAHS was defined as an AHI≥10 and pathological daytime
sleepiness (ESS>10 points [14]), as defined by the Spanish Consensus Document [15]in
accordance with the recommendations of the American Academy of Sleep Medicine [16].
T
90
was defined as the percentage of time during which arterial oxygen saturation was less
than 90%.
Measurements
The BP was measured two times with the subject seated and an interval of 5 min between
measurements at 7:20 AM. BP measurements were taken on the right arm, which was
relaxed and supported by a table, at an angle of 45° from the trunk (ELKA aneroid
manometric sphygmomanometer, Von Schlieben Co., Manheim, Germany).
Fasting venous blood samples were drawn at 7:30 AM, before and 1 month after CPAP
treatment. Samples were collected in vacutainers with and without ethylenediaminetetra-
acetic acid and placed on ice. Samples were centrifuged at 4,000 rpm for 15 min at 4°C.
Plasma and serum were aliquoted and stored at −80°C until analysis.
Oxidative Stress 1291

Biochemical variables studied included glucose, uric acid, cholesterol, high-density
lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides and Hb1Ac.
The insulin was analyzed by an immunoradiometric assay (BioSource International,
Camarillo, CA) in a Beckman Coulter (Fullerton, CA), showing a 0.3% crossreaction with
proinsulin. The intra- and inter-assay CV was 1.9% and 6.3%, respectively. The
homeostatic model assessment was used to determine IR (HOMA-IR) and beta-cell
function (HOMA-beta) [17].
Serum leptin levels were measured using a human leptin enzyme-linked immunosorbent
assay (ELISA) kit from Mediagnost (Reutlingen, Germany). The intra- and inter-assay
coefficients of variation were 2.6% and 4.7%.
Serum adiponectin levels were measured using a human adiponectin ELISA kit from
DRG diagnostics (Marburg, Germany). The intra- and inter-assay coefficients of variation
were 3.4% and 7.8%.
Serum high sensitivity C-reactive protein (hs-CRP) levels were measured using a human
hs-CRP ELISA kit from BLK Diagnostics (Badalona, Spain). The intra- and inter-assay
coefficients of variation were 4.7% and 7.3%.
Determination of Plasma and Serum Oxidative Stress Biomarkers
Lipid peroxidation levels were measured in serum using a commercial kit (Cayman
Chemical, Ann Arbor, MI).
Total antioxidant capacity (TAC) and the activities of glutathione peroxidase (GPx),
glutathione reductase (GR), glutathione s-transferase (GST), catalase, and superoxide
dismutase (SOD) were measured in plasma with a commercial kit (Cayman Chemical, Ann
Arbor, MI). The intra- and inter-assay coefficients of variation of TAC, GPx, GR, GST,
catalase, and SOD were 3.4% and 3.0%; 5.7% and 7.2%; 3.7% and 9.3%; 4.1% and 7.9%;
3.8% and 8.9%; 3.2% and 3.7%, respectively.
Determination of White Blood Cell Oxidative Stress Biomarkers
Oxidative stress biomarkers were analyzed in white blood cells (WBCs) as total leukocytes,
neutrophils, lymphocytes, and monocytes.
WBCs were isolated from patients by dextran sedimentation followed by density
gradient centrifugation with Ficoll–Paque. After purification with two washing steps,
1×10
6
cells/mL WBCs were analyzed on a dual-laser FACSCalibur (Becton Dickinson,
Mountain View, CA). The test standardization, data acquisition and data analysis were
performed using the CELL Quest software (Becton Dickinson). A forward and side
scatter gate was used for the selection and analysis of the different cell subpopulations.
a. Mitochondrial membrane potential (MMP)
WBCs were incubated with Rodamina-123 from Sigma-Aldrich (USA) dissolved in
methanol, at a final concentration of 5 μM. After incubation at 37°C for 30 min in darkness
with frequent agitation, the cells were washed and re-suspended in phosphate-buffered
saline (PBS) and were analyzed on a dual-laser FACSCalibur.
b. ROS and intracellular glutathione measurements
For the assessment of mitochondrial ROS generation, such as superoxide anion and
hydrogen peroxide, cells were incubated with dihydroethidium×5 mM stabilized solution
1292 Murri et al.

in dimethyl sulphoxide (DMSO) from Molecular Probes (Eugene, OR, USA; final
concentration, 4 μM) and 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diace-
tate acetyl ester from Molecular Probes (Eugene, OR, USA) dissolved in DMSO at a final
concentration 1 μg/μl, respectively, at 37°C for 30 min in darkness with frequent agitation.
The cells were then washed and re-suspended in PBS and analyzed on a dual-laser
FACSCalibur.
For detection of intracellular glutathione, WBCs were incubated with CellTracker™
Green 5-chloromethylfluorescein diacetate from Molecular Probes (Eugene, OR, USA),
dissolved in DMSO at a final concentration 1 μM, for 30 min in darkness with frequent
agitation. The labeled cells were washed and re-suspended in PBS and analyzed on a dual-
laser FACSCalibur.
Statistical Analysis
The results are given as the mean ± standard deviation. All clinical parameters are
summarized by descriptive statistics. Relationships between the results of the controls and
the patients were analyzed using the Mann–Whitney Utest. The Student ttest for paired
samples was used to compare oxidative stress and clinical parameters before and after
treatment with CPAP. The Pearson’s correlation coefficient was calculated to estimate the
linear correlations between variables. In all cases, the rejection level for a null hypothesis
was α=0.05 for two tails. The statistical analysis was done with SPSS (Version 15.0 for
Windows; SPSS, Chicago, IL).
Results
The clinical variables of the study patients and controls are shown in Table 1.
Evaluation of plasma biomarkers of oxidative stress showed significant increases
after CPAP treatment (p<0.05) in TAC and catalase, SOD, GR, and GST activities
(Table 2).
Analysis of oxidative stress biomarkers in WBCs showed a significant decrease after
CPAP in the production of superoxide anion and hydrogen peroxide and significant
Table 1 Distribution of clinical variables in the studied patient group
Variables Controls (n=16) Patients (n=26) p
Age (years) 47.62 ±7.40 52.15± 13.41 0.102
BMI (kg/m
2
) 30.56± 2.16 33.07 ±5.61 0.517
Waist circumference (cm) 108.65± 7.13 114.65± 12.42 0.169
Neck circumference (cm) 42.40± 3.80 44.62 ±4.31 0.102
AHI (events/h) 3.19± 0.73 55.41 ±21.47 0.000
Mean SaO
2
(%) 95. 75± 1.34 91.35 ±3.40 0.000
ODI (desaturations/h) 2.88± 1.79 43.34 ±29.06 0.000
T
90
(%) 0 10.29± 13.08 0.000
ESS score 3.19± 1.22 14.07 ±6.53 0.000
Values are presented as means ± SD
AHI apnea–hypopnea index, BMI body mass index, ESS Epworth sleepiness scale, ODI oxygen desaturation
index, T
90
(%) percentage of time during which arterial oxygen saturation was less than 90%
Oxidative Stress 1293

increases after CPAP treatment in intracellular glutathione levels. These redox changes were
accompanied by an increase in MMP (Fig. 1; Table 3).
Moreover, Tables 2and 3show differences between control group and patients. Plasma
total antioxidant capacity and SOD activity, MMP and intracellular glutathione of WBC
were significantly higher in the control group than in the SAHS patients. Whereas
superoxide anion and hydrogen peroxide were significantly lower in the control group than
in the SAHS patients.
Both SBP and DBP fell significantly after CPAP treatment. The ESS also decreased
significantly after treatment. The other clinical and biological variables experienced no
significant changes (Table 4).
Statistically significant positive correlations were observed between plasma TAC
and lymphocyte intracellular glutathione (r=0.399; p< 0.05). Significant negative
correlations were observed between GPx activity and cellular superoxide anion levels
before treatment in neutrophils (r=−0.491; p<0.02), total leukocytes (r=−0.460;
p<0.02), and monocytes (r=−0.526; p<0.01). Also, there was a statistically significant
negative correlation between plasma SOD activity and the hydrogen peroxide levels in
neutrophils (r=−0.408; p<0.05) and total leukocytes (r=−0.390; p<0.05). Furthermore,
there was a statistically significant negative correlation between plasma TAC and
hydrogen peroxide levels in neutrophils (r=−0.492; p<0.02), total leukocytes (r=−0.468;
p<0.02), and monocytes (r=−0.469; p<0.02). After treatment with CPAP, there was a
statistically significant positive correlation between plasma catalase activity and
lymphocyte MMP (r=0.398; p<0.05).
SAHS severity, including AHI and ODI, correlated negatively with total antioxidant
capacity and intracellular glutathione before treatment (Fig. 2). After CPAP, lymphocyte
MMP correlated significantly with ESS (r=−0.453; p<0.05).
Before CPAP, systolic and diastolic blood pressure correlated negatively with MMP.
Also, systolic and diastolic blood pressure correlated positively with serum lipid
hydroperoxide levels before CPAP (Fig. 3).
Table 2 Comparison of plasma oxidative stress markers
Variables Controls (n=16) Patients (n=26)
Before CPAP After CPAP
Catalase (nmol
−1
min
−1
ml
−1
) 27.66± 12.11 25.22± 10.12 29.68± 10.57*
Superoxide dismutase (U/ml) 2.106± 0.562 1.633± 0.640*** 1.439± 0.648*
Glutathione peroxidase (μmol
−1
min
−1
ml
−1
) 21.05± 5.09 19.59± 5.79 20.10± 6.32
Glutathione reductase (μmol
−1
min
−1
ml
−1
) 4.402±1.922 3.018 ±0.497 3.208±0.559*
Glutathione transferase (μmol
−1
min
−1
ml
−1
) 2.632±0.445 1.606 ±0.534 2.105±0.891**
Lipid hydroperoxide (μM) 10.37± 5.06 12.16±3.80 11.70±4.69
Total antioxidant capacity (mM) 6.237± 3.178 4.141± 1.361**** 4.372± 1.476**
Values are presented as means ± SD. Relationships between plasma oxidative stress markers in control and in
patients before CPAP were analyzed using the Mann–Whitney Utest. Relationships between plasma
oxidative stress markers in patients before and after CPAP were assessed using the Student’sttest
*p<0.05; **p< 0.01, significant difference in the results found in patients between before and after treatment
with CPAP; ***p<0.05; ****p<0.001, significant differences in the results found between controls and
patients before treatment with CPAP
1294 Murri et al.

Discussion
Our results show that parameters of cellular oxidative stress were significantly lower in the
control group than in the SAHS patients, while markers of protection against oxidative
stress were significantly higher in the control group than in the SAHS patients. Also, we
have found that parameters of oxidative stress showed a notably decrease after CPAP.
Diastolic and systolic blood pressure also decreased significantly while IR did not improve
significantly.
Oxidative stress is the consequence of an increase in the production of free radicals and
ROS and/or a reduction in the antioxidant systems [18]. In the present study, oxidant
Fig. 1 Differences between cellular oxidative stress biomarkers in total white blood cells (WBCs) before and
after treatment with continuous positive airway pressure (CPAP) were analyzed on a dual-laser FACSCalibur.
Green represents values before CPAP treatment; purple represents values after treatment. aSuperoxide anion
in total WBCs. bHydrogen peroxide in total WBCs. cIntracellular glutathione in total WBCs. (d)
Mitochondrial membrane potential of total WBCs
Oxidative Stress 1295

production and antioxidant systems seem to be impaired in patients compared with the
control group. After CPAP, we have found an increase in plasma levels of TAC, and
catalase, SOD, GR, and GST activities. In addition, we have found an inverse correlation
between plasma GPx levels and cellular ROS production. Plasma GPx is the main
antioxidant enzyme in plasma and the extracellular space that redeems ROS. A deficiency
of this enzyme increases extracellular oxidative stress. In hypoxic conditions, the
expression of plasma GPx increases through the presence of hypoxia-inducible factor-1
[19]. Moreover, we have found a clear inverse relationship between plasma SOD and
cellular ROS. Some disorders have been associated with high ROS production and
reduced antioxidant activities [20]. The most significant changes in parameters of
oxidative stress were found in WBCs. These parameters showed a notably decrease,
whereas intracellular glutathione and MMP increased significantly. These results confirm
that hypoxia normalization with CPAP treatment reduces oxidative stress. Moreover, we
have found significant negative correlations between SAHS severity and markers of
protection against oxidative stress, including intracellular glutathione and plasma total
antioxidant capacity. In addition, ESS correlated negatively with lymphocyte MMP after
Table 3 Comparison of cellular oxidative stress markers
Controls (n=16) Patients (n=26)
Before CPAP After CPAP
Lymphocyte MMP
(1)
21.99± 3.60 16.57±4.53
c
20.34± 4.68***
Monocyte MMP
(1)
41.92± 7.01 32.20±8.60
c
39.33± 8.60***
Neutrophil MMP
(1)
29.99± 6.79 27.21±6.48
c
23.05± 6.09*
Total leukocyte MMP
(1)
32.25± 7.23 21.93±6.05
c
26.52± 7.02**
Lymphocyte hydrogen peroxide
(1)
14.35± 3.14 20.47±7.00
b
15.39± 5.42***
Monocyte hydrogen peroxide
(1)
24.87± 3.40 42.36±16.33
b
33.43± 15.59*
Neutrophil hydrogen peroxide
(1)
21.83± 5.61 29.73±14.23
a
23.69± 13.22
Total leukocyte hydrogen peroxide
(1)
22.07± 6.81 27.34 ±11.20 21.88±10.21*
Superoxide anion in lymphocytes
(1)
13.15± 1.97 68.10±39.68
c
48.75± 30.85**
Superoxide anion in monocytes
(1)
21.78± 3.71 139.13±83.30
c
105.44± 74.87*
Superoxide anion in neutrophils
(1)
18.52± 2.92 91.93±57.07
c
70.40± 46.59*
Superoxide anion in total leukocytes
(1)
17.93± 4.07 87.87±51.26
c
65.46± 41.17*
Lymphocyte intracellular glutathione
(1)
173.45± 24.76 105.26±60.23
c
175.04± 86.66***
Monocyte intracellular glutathione
(1)
478.75± 104.91 287.63±155.00
b
465.44± 181.26***
Neutrophil intracellular glutathione
(1)
535.95± 90.90 252.11± 126.26
c
440.23± 163.57***
Total leukocyte intracellular glutathione
(1)
343.50± 92.12 188.26±96.34
c
306.02± 127.43***
Values are presented as means ± SD. 1, Mean Fluorescence Intensity; MMP, mitochondrial membrane
potential. Relationships between cellular oxidative stress markers in control and in patients before CPAP
were analyzed using the Mann–Whitney Utest. Relationships between cellular oxidative stress markers
before and after CPAP were assessed Student’st-test.
a
P<0.05;
b
P<0.005;
c
P<0.001: Significant differences in the results found between controls and patients
before treatment with CPAP. *P<0.05; **P<0.01; ***P< 0.005: significant difference in the results found in
patients between before and after treatment with CPAP.
1296 Murri et al.

CPAP. It seems that SAHS severity is contributing to impair the antioxidant system of
these patients.
In our study, we have found a significant decrease in SBP and DBP after 1 month of
treatment. Controversy surrounds the effect of nasal CPAP on blood pressure in SAHS
patients. Some studies have found no significant changes in BP after CPAP in SAHS
patients [21,22]. Others [23] have demonstrated a significant reduction in BP in patients
after CPAP. Additionally, Usui et al.[24] showed changes in both BP and sympathetic tone
after 1 month of treatment. These discordant results suggest the existence of confounding
factors such as IR [25]. In our study, the BP reduction was not accompanied by a decline in
the IR. The benefit of CPAP treatment on BP therefore seems to be independent of IR
modifications. Intermittent experimental hypoxia and clinical SAHS lead to an elevated
sympathetic tone that persists throughout the day [26]. This elevation results in a high heart
rate and elevated BP. Several studies have described the implication of oxidative stress in
this process [27]. In accordance with this, our results show, on one hand, significant
positive correlations between oxidative stress marker such as serum lipid peroxide and
blood pressure, and on the other, significant negative correlations between marker of
protection against oxidative stress such as MMP and blood pressure before CPAP.
The effects of CPAP on IR in SAHS patients remain unclear. While some studies show a
tendency to improved insulin sensitivity or IR after CPAP [7,12], other researchers were
unable to confirm this result [13], as was also noted in our study. This disparity in results
can be explained by the lack of control in anthropometric changes that occur after CPAP,
because patients become more active and mass change may occur. Weight is a confounding
variable in CPAP treatment and may produce changes in IR. In this study, anthropometric
variables were rigorously controlled and those patients whose weight changed were
excluded.
Table 4 Distribution of biological variables in the studied patient group before and after CPAP treatment
Variables Before CPAP After CPAP p
ESS 14.07± 6.53 9.56± 4.25 0.001
Systolic BP (mmHg) 150.26± 24.64 141.74±22.99 0.014
Diastolic BP (mmHg) 91.30± 14.20 84.13 ±14.33 0.012
BMI (kg/m
2
) 33.07± 5.61 32.94± 5.29 0.783
Insulin (μUI/ml) 18.46± 8.09 19.11± 10.95 0.954
HOMA-IR 4.713± 2.367 4.472± 2.413 0.977
HOMA-IS 62.42± 31.77 59.90± 32.34 0.879
Leptin (ng/ml) 16.90± 10.86 18.02± 13.42 0.316
Adiponectin (ng/ml) 6.80± 2.94 6.86± 3.24 0.607
Triglyceride (mg/dl) 153.00± 130.87 164.27± 155.25 0.275
Cholesterol (mg/dl) 199.42± 45.70 195.38±41.03 0.602
HDL cholesterol (mg/dl) 45.92± 11.51 46.38± 11.90 0.614
LDL cholesterol (mg/dl) 126.46 ±35.63 123.27 ± 30.10 0.849
Values are presented as means ± SD. Relationships between biological variables before and after CPAP were
assessed Student’sttest (p<0.05)
BMI body mass index, BP blood pressure, ESS Epworth sleepiness scale
Oxidative Stress 1297

In conclusion, we observed an obvious improvement in oxidative stress and found that it
was accompanied by an evident decrease in BP with no modification in IR. Consequently,
we believe that the decrease in oxidative stress after 1 month of CPAP treatment in these
patients is not contributing much to the genesis of IR, though it could be related to the
etiology of the hypertension.
Fig. 2 Correlations of sleep apnea–hypopnea syndrome severity parameters with markers of protection
against oxidative stress before continuous positive airway pressure treatment were determined by Pearson’s
correlation coefficient test (r). aCorrelation of monocyte intracellular glutathione with apnea–hypopnea
index (AHI). bCorrelation of neutrophil intracellular glutathione with AHI. cCorrelation of plasma total
antioxidant capacity with AHI. dCorrelation of plasma total antioxidant capacity with oxygen desaturation
index (ODI)
Fig. 3 Correlations of blood pressure (BP) with oxidative stress biomarkers were determined by Pearson’s
correlation coefficient test (r). Correlation of lipid hydroperoxide levels with diastolic BP (a) and systolic BP
(b). Correlation of total leukocyte mitochondrial membrane potential (MMP) with diastolic BP (c) and
systolic BP (d). Correlation of monocyte MMP with diastolic BP (e) and systolic BP (f)

1298 Murri et al.

Oxidative Stress 1299

Acknowledgments The authors thank Juan Alcaide (technician) for his technical support in developing our
laboratory techniques. This work was supported in part by grants from the Andalusian Health Service (SAS
PI-0326/2007) and the Spanish Ministry of Education and Science (SAF2006-12984). Murri is a recipient of
a predoctoral Investigator Personal Formation grant (BES-2007-16594) from the Spanish Ministry of
Education and Science, and Cardona is a recipient of CP07/0095 grant. The authors thank the Pneumology
and Hematology service and the pneumology nursing staff of the Virgen de la Victoria Hospital, Málaga.
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