The goal of this observational cohort study is to evaluate whether the COPD Assessment Test (CAT) score can predict the risk of perioperative respiratory complications in patients aged 40 to 70 years with diagnosed Chronic Obstructive Pulmonary Disease (COPD), undergoing elective surgical procedures lasting no longer than 150 minutes.

The main questions it aims to answer are:

• Is there a statistically significant association between preoperative CAT scores and the incidence of intraoperative and early postoperative respiratory complications in COPD patients?
• Can the CAT score be effectively used as a preoperative risk stratification tool to guide anesthetic and surgical decision-making?

Researchers will compare two patient groups based on CAT scores: those with CAT <10 and those with CAT ≥10 to determine whether higher CAT scores are associated with an increased incidence of perioperative respiratory complications.

Participants will:

• Complete the CAT questionnaire during the preoperative evaluation
• Undergo elective surgery with an expected duration of ≤150 minutes
• Be monitored intraoperatively for bronchospasm, oxygen desaturation, and ventilation difficulty
• Be monitored postoperatively (within the first 72 hours) for hypoxemia, reintubation, bronchospasm episodes, postoperative pneumonia, intensive care unit (ICU) admission, and length of hospital stay
• Have perioperative clinical data collected and analyzed for comparative outcomes between CAT score subgroups

Chronic Obstructive Pulmonary Disease (COPD) is a common chronic respiratory disease associated with increased perioperative morbidity and mortality. Surgical procedures in COPD patients often carry higher risks of respiratory complications, making anesthetic management more challenging. The COPD Assessment Test (CAT) is a simple and practical tool developed to assess symptom burden in COPD patients and is being increasingly integrated into clinical practice. While its utility in evaluating disease-related symptoms and quality of life is well documented, the role of CAT score in predicting perioperative respiratory complications remains unclear.

This prospective observational cohort study aims to evaluate whether the CAT score can be used to predict perioperative respiratory risk and support clinical decision-making for anesthesiology and surgical teams. Based on previous estimates, patients with high CAT scores appear to be at greater risk for complications. A total of 120 patients will be enrolled in the study, with 60 patients in each group. Patients will be categorized into two groups based on their CAT scores:

Group 1: CAT <10 (Low symptom burden)

Group 2: CAT ≥10 (High symptom burden)

Patients aged 40-70 years with a diagnosis of stable COPD scheduled for elective surgery lasting no more than 150 minutes will be included. The relationship between CAT score and perioperative respiratory complications will be statistically analyzed.

In the preoperative period (within 24 hours before surgery), data will be collected on demographics (age, sex, BMI, smoking history), comorbidities, surgical type (e.g., thoracic, abdominal, urological), ASA physical status classification, and planned anesthesia technique (general or regional). Arterial blood gas (ABG) samples at rest will be obtained. Additionally, Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) stage, spirometry data (Forced Expiratory Volume in 1 Second (FEV1), Forced Vital Capacity (FVC), FEV1/FVC ratio), and CAT score will be recorded by a pulmonologist.

During the perioperative period, ABG samples will be taken prior to induction and preoxygenation. All patients will receive standardized general anesthesia with full monitoring (Electrocardiogram (ECG), Peripheral Capillary Oxygen Saturation (SpO2), non-invasive blood pressure, capnography). Preoxygenation will be performed for at least 2 minutes. Anesthesia induction protocol includes:

• 1-2 mg IV midazolam (premedication)
• 0.3-0.5 mg/kg IV lidocaine
• 1.5-2.5 mg/kg IV propofol
• 0.6-1.2 mg/kg IV rocuronium
• 1-2 mcg/kg IV fentanyl

After sufficient muscle relaxation, endotracheal intubation will be performed. All patients will be ventilated using volume-controlled ventilation with ideal body weight-based settings: tidal volume 6-8 mL/kg, respiratory rate 10-14/min, Positive End-Expiratory Pressure (PEEP) 3-5 cmH₂O, I:E ratio 1:2, and target End-Tidal Carbon Dioxide (EtCO₂) of 35-45 mmHg. Volatile anesthetics (sevoflurane or desflurane) will be administered at a minimum of 1.3 Minimum Alveolar Concentration (MAC). Intraoperative respiratory events (bronchospasm, desaturation, ventilation difficulty) will be observed and documented. A second ABG sample will be collected 2 minutes after induction.

At the end of surgery, patients will receive 10-15 mg/kg IV paracetamol and 1-2 mg/kg IV tramadol for analgesia. Neuromuscular blockade will be reversed with 2 mg/kg IV sugammadex.

Postoperatively, ABG samples will be taken in the Post-Anesthesia Care Unit (PACU) and again at the 72nd hour. The following respiratory complications will be recorded within the first 72 hours:

• Hypoxemia (SpO₂ <92%)
• Reintubation requirement
• Bronchospasm episodes
• Postoperative pneumonia
• Intensive Care Unit (ICU) admission
• Length of hospital stay (in days)

All data will be collected by anesthesiologists involved in the study.

The primary objective of this study is to evaluate whether the preoperative CAT score can predict postoperative respiratory complications in patients with COPD. The secondary objective is to determine whether patients with high CAT scores require more postoperative oxygen therapy. The tertiary (exploratory) objective is to assess whether patients with higher CAT scores need more extensive medical optimization before surgery and whether the CAT score can serve as a useful guide in preoperative planning.

Inclusion Criteria:

• Patients aged between 40 and 70 years
• Diagnosed with stable-stage Chronic Obstructive Pulmonary Disease (COPD) according to GOLD criteria
• Scheduled for elective surgical intervention
• Classified as ASA Physical Status II or III according to the American Society of Anesthesiologists (ASA)
• Planned for postoperative follow-up and eligible for at least 72 hours of observation
• Undergoing surgery with an expected duration of at least 150 minutes
• Willing to participate voluntarily in the study

Exclusion Criteria:

• Patients younger than 40 years or older than 70 years
• History of COPD exacerbation within the past 4 weeks
• Presence of severe cardiac failure (EF <30%), end-stage renal disease, or active malignancy
• Neurological disorders or cognitive impairments
• Requirement for invasive mechanical ventilation in the preoperative period
• Altered consciousness or any condition preventing completion of forms before anesthesia
• Undergoing surgery with an expected duration longer than 150 minutes
• Unwillingness to participate in the study voluntarily

Patients aged between 40 and 70 years with a diagnosis of stable-stage COPD according to GOLD criteria