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To describe the relationship between OSA and clinical Hypertension (performing ABPM), endothelial dysfunction (performing flowmetry), and its relation at the basic research (determining the β1 subunit in Peripheral Leukocytes in peripheral blood). This relation between OSA and HTA has been evaluated in basal conditions and after modifying the pathophysiological role of OSA applying treatment with positive continues pressure (CPAP) during 3 months.
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Background: Several epidemiological studies have demonstrated that untreated OSA with continuous positive airway pressure, is related to high rates of cardiovascular morbidity and mortality, being HTA the most important cardiovascular morbidity associated with OSA. This relationship has been studied at three levels: clinical, subclinical and the basic research or molecular level. Most patients with OSA diagnosis have developed clinical hypertension and, because of the high prevalence of nocturnal hypertension in OSA, it would be essential to monitor blood pressure during sleep, using this device ambulatory blood pressure monitoring (ABPM). Regard to endothelial dysfunction, which can exist before irreversible vascular changes have occurred in the arterial wall (subclinical level) has been reported that patients with OSA have lower blood flow (measured by arterial flowmetry) and after treatment with CPAP, there is an improvement in endothelial function. At basic research level, in previous studies it has been observed that hypoxia down regulates the expression of Maxi-K+ Channel B1-subunit in smooth muscle cell and also in peripheral leukocytes. This channel is involved in the regulation of arterial vasodilation, being β1 subunit responsible for the vascular tone regulation. Basic research studies have shown the relationship between hypertension and ß1 subunit, describing that the expression of that unit decreases in hypertensive animal models. In a pilot study in OSA patients was suggested that ß1 subunit channel Maxi-K + could play an important role in vascular dysregulation of these patients. It has been also described a correlation between ß1 subunit level in vascular smooth muscle cells and its level in leukocytes.
Objective: To describe the relationship between OSA and hypertension from a clinical point of view (by performing ABPM), its relationship with endothelial dysfunction (by performing a flowmetry) and basic research level (by the determination of β1 subunit of the maxi-K channel +). This relationship between hypertension and OSA has been assessed at baseline condition in a group of OSA patients and a control group without OSA, and after changing the pathophysiological role of OSA treating with continuous positive pressure airway (CPAP) in the group of OSA patients.
Patients: Prospective study in which:
Measurements:
These procedures are described below:
-Nocturnal cardiorespiratory polygraphy was performed in the "sleep laboratory of Medical-Surgical Unit of Respiratory Diseases". It has used a respiratory polygraph "Sibelhome plus"(trade name).
We measured the following variables:
Oronasal Flow. Snore: using laryngotracheal microphone. Thoracoabdominal-Effort: by two bands effort sensors placed at the level of the chest and abdomen. Arterial oxygen saturation (SaO2): Flexible digital pulse oximeter. Body-position sensor.
The records are stored in a specific database and analysis was carried out manually. The events are defined
Apnea: absence of oronasal airflow for ≥ 10 sec. Hypopnea: oronasal flow decrease ≥ 50% from baseline for ≥ 10 seconds, accompanied by desaturation.
We calculated the following parameters:
AHI: total number of apnea + hypopnea / hour check. When AHI is <5 was considered negative for OSA and when AHI WAS ≥ 15, OSA diagnosis was made. Desaturation index (DI): total number of desaturations / hour check. Basal and minimum-Saturation: automatic analysis obtained oximetry throughout the entire record. Percentage of recording time with SaO2 <90% (CT90): automatic analysis obtained oximetry throughout the entire record.
We collected the following variables:
24hours systolic and diastolic blood pressure. Medium blood pressure at day and night. Standard deviation day and night blood pressure. Percentage of high measured for 24 hours, and during periods of activity and rest. BP variability (standard deviation of the mean). 24-hour mean heart rate. Average heart rate daytime. Night Average heart rate.
The software performed two types of analysis:
General analysis: where reported the initial value, maximum value, percentage change from the first to last value or maximum slope of the curve or slope and area under the curve. Adjusted Analysis: It was estimated biological zero, peak flow, hyperemia area, time to maximum hyperemia, time to reach the half-maximal hyperemia and latency.
From these cells was performed the expression level of β1 subunit by quantitative RT-PCR technique. For reverse transcription of RNA using the Superscript III First-kit Starnd Synthesis System (trade name). For quantitative PCR we used the ABI PRISM equipment 7500 Sequence Detection System (Applied Biosystems), using the reagents Sybr Green PCR Master Mix or TaqMan probes, following the protocols indicated by the manufacturer.
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80 participants in 2 patient groups
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Data sourced from clinicaltrials.gov
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