Obstructive sleep apnea (OSA) is a condition where a person's airway repeatedly collapses during sleep, causing them to stop breathing briefly and disrupting their rest. The standard way to diagnose OSA is a formal overnight sleep study called polysomnography (PSG). However, in resource-limited settings, sleep study centers are scarce, which can lead to months of waiting before a patient can be diagnosed and treated. Delaying treatment can negatively affect a patient's quality of life and increase their risk for other health issues.

The purpose of this observational study is to evaluate the clinical benefits of starting continuous positive airway pressure (CPAP) therapy early for patients who are highly suspected to have OSA, while they wait for their formal sleep study.

Researchers will enroll adult patients who have symptoms of OSA (such as loud snoring, witnessed breathing pauses, and severe daytime sleepiness) and a high clinical probability of having the condition. Instead of waiting for the official sleep study to begin treatment, these participants will be provided with an Auto-CPAP machine set to a practical pressure range.

The main goals of the study are to evaluate:

• If this early, empirical Auto-CPAP treatment improves patients' daytime sleepiness and overall quality of life, which will be measured using specialized questionnaires.
• How accurately the temporary Auto-CPAP machine's pressure settings match the final, optimal pressure settings that will eventually be determined by the formal sleep study.

Obstructive sleep apnea (OSA) is a prevalent sleep disorder associated with severe comorbidities, including an increased risk of cardiovascular events, stroke, and premature mortality. While polysomnography (PSG) remains the gold standard for diagnosing OSA, it is time-consuming, expensive, and not readily accessible in resource-limited settings. The scarcity of sleep study centers often results in months of delay for patients with a high clinical suspicion of OSA, leaving them untreated and at an elevated risk for prolonged morbidity.

This observational cohort study, conducted at the Chest Department of Assiut University Hospital, aims to evaluate the efficacy of empirical Auto-CPAP therapy for patients waiting for diagnostic PSG. Patients presenting with a high clinical probability of OSA will undergo a comprehensive baseline evaluation. This includes a meticulous medical history, clinical examination, and anthropometric measurements to categorize Body Mass Index (BMI). Additional baseline diagnostics include a standard posteroanterior Chest X-Ray and comprehensive laboratory investigations (Lipogram, HbA1C, T3, T4, TSH, CBC, Urea, Creatinine, Liver Function Tests, and Arterial Blood Gases). Furthermore, patients will undergo spirometry testing (using a Zan 300 device) performed according to ATS-ERS 2019 criteria for acceptability and repeatability.

Clinical probability and the impact of daytime sleepiness will be quantified using standardized questionnaires, including the STOP-BANG score, the Epworth Sleepiness Scale (ESS), and the 10-item Functional Outcomes of Sleep Questionnaire (FOSQ-10). Following these baseline assessments, eligible patients will be initiated on empirical Auto-CPAP therapy utilizing a practical pressure range of 6-14 mmHg.

Patients will be monitored to evaluate clinical symptom improvement and quality of life changes during this empirical therapy phase. Once patients are able to undergo their delayed diagnostic PSG, the optimal CPAP titration pressure determined by the formal sleep study will be recorded. The study will analyze the agreement and differences between the initial empirical Auto-CPAP pressures and the final PSG-determined pressures. The data will be analyzed to explore correlations between the optimal pressure requirements and specific patient characteristics, such as BMI, neck circumference, and baseline STOP-BANG scores.

Inclusion Criteria:

• Age ≥18 years.
• Patients presenting with symptoms suggestive of OSA, including one or more of the following: excessive daytime sleepiness, habitual snoring, witnessed apnea during sleep, non-restorative sleep, or morning headache.
• High clinical probability of OSA defined by: STOP-BANG score ≥5 or STOP-BANG score 3-4 with ESS ≥10.
• Patients awaiting diagnostic PSG due to delayed access to sleep laboratory services.
• Patients with OSAS and COPD overlap.
• Obesity hypoventilation syndrome requiring automated CPAP.
• Ability and willingness to use CPAP and provide informed consent.

Exclusion Criteria:

• Age <18 years.
• Pregnancy.
• Previous PSG-confirmed OSA with prescribed CPAP settings.
• Predominant central sleep apnea.
• Cheyne-Stokes respiration.
• Neuromuscular disorders affecting respiration.
• Severe psychiatric illness impairing adherence.
• Inability to provide informed consent.
• Severe unstable cardiopulmonary disease requiring urgent respiratory support, including: acute heart failure, acute coronary syndrome, acute respiratory failure, or severe COPD with chronic hypercapnic respiratory failure requiring NIV rather than CPAP.
• Obesity hypoventilation syndrome requiring bilevel PAP (BiPAP) instead of CPAP.

The study population consists of adult patients (aged 18 years and older) attending the Chest Department at Assiut University Hospital who present with symptoms suggestive of Obstructive Sleep Apnea (OSA), such as excessive daytime sleepiness, habitual snoring, or witnessed apnea. Eligible patients must have a high clinical probability of OSA, defined as having a STOP-BANG score of 5 or greater, or a STOP-BANG score of 3 to 4 combined with an Epworth Sleepiness Scale (ESS) score of 10 or greater. Furthermore, the population is specifically composed of individuals who are currently awaiting diagnostic polysomnography (PSG) due to delayed access to sleep laboratory services in a resource-limited setting.