The purpose of this study is to evaluate the effectiveness and clinical efficiency of combining home non-invasive ventilation (NIV) with a continuous remote telemonitoring (TM) system in patients with Chronic Obstructive Pulmonary Disease (COPD) and persistent hypercapnia. In standard practice, patients with severe COPD and high carbon dioxide levels in their blood are treated with home non-invasive ventilation to support their breathing. This study compares two different care strategies over a one-year follow-up period:

1. One group of patients will receive standard home non-invasive ventilation alone.
2. Another group will receive home non-invasive ventilation combined with an automated telemonitoring system that tracks device parameters daily (such as air leaks, device usage, and breathing rates) and sends automated alerts to the healthcare team if deviations occur. The main goal of the project is to determine if adding a telemonitoring follow-up system can prevent clinical worsenings and significantly reduce the total number of days patients spend hospitalized due to severe COPD flare-ups. Additionally, the study will analyze the impact of both strategies on patients' overall health-related quality of life and the economic costs within the healthcare system.

Background and Rationale:

Chronic Obstructive Pulmonary Disease (COPD) with persistent hypercapnia is associated with increased mortality, functional decline, and high healthcare costs. While home non-invasive ventilation (NIV) is established as standard care to correct chronic respiratory failure, integrating remote telemonitoring (TM) presents an opportunity to implement early clinical interventions by allowing continuous oversight of ventilator parameters.

Study Design and Setting:

This is a prospective, multicenter, comparative cohort study with an integrated economic and utility evaluation. The study will be conducted across 5 public university hospitals within the Community of Madrid, Spain. A total of 92 patients (46 patients in the NIV+TM cohort and 46 in the conventional NIV cohort).

Study Hypotheses:

• Conceptual Hypothesis: Patients managed with the combined NIV+TM strategy experience a better clinical course than those treated with standard NIV alone.
• Statistical Hypothesis: Patients in the NIV+TM group will experience a lower average burden of exacerbation-related hospitalizations (estimated average of 24 days over 12 months) compared to the conventional NIV group (estimated average of 32 days over 12 months), reflecting a significant reduction of 8 hospital days between both management strategies during the first year of treatment.

Description of Cohorts and Follow-up Interventions:

• Combined Ventilation and Telemonitoring Cohort (NIV+TM): Patients receive standard advanced pressure-controlled nocturnal NIV combined with a remote data transmission modem. Clinical parameters-including device compliance, residual Apnea-Hypopnea Index (AHI), intentional/unintentional air leaks, respiratory rate (RR), and tidal volume (Vt)-are continuously monitored. Automated alerts are prioritized by the system: Low Priority alerts are tracked during routine visits, while High Priority alerts trigger an explicit, standardized clinical decision algorithm. This algorithm mandates immediate telephone triage, home technician visits for equipment adjustments, or direct communication with the prescribing pulmonologist for parameter adjustments. Domiciliary visits and health-related quality of life assessments (EQ-5D-5L and Severe Respiratory Insufficiency [SRI] questionnaires) will be carried out at baseline, 30, 90, 180, 270, and 365 days.
• Conventional Ventilation Cohort (NIV alone):

Patients receive identical advanced pressure-controlled nocturnal NIV settings but without remote data monitoring capabilities. Follow-up follows conventional guidelines based on standard clinical dependence: monthly home visits for patients requiring >12 hours/day of ventilation, or quarterly home visits for those requiring ≤12 hours/day. Compliance data, air leaks, and adaptation are checked manually during these visits. In-person follow-ups, EQ-5D-5L, and SRI assessments occur at baseline, day 30, and regular domiciliary visits, alongside mandatory arterial blood gas monitoring at 3, 6, and 12 months to verify treatment efficacy.

Economic and Data Analysis:

Analytical evaluations will be performed on an intention-to-treat basis. Clinical outcomes, utility values (Quality-Adjusted Life Years - QALYs gained calculated via Spanish EQ-5D-5L utility weights), and direct medical/non-medical healthcare system costs (utilizing the most recent official public tariffs from the Madrid Health Service - SERMAS) will be combined. Incremental Cost-Effectiveness Ratios (ICER), Incremental Cost-Utility Ratios (ICUR), and Incremental Cost-Benefit ratios will be constructed to evaluate healthcare efficiency. Uncertainty will be addressed via a deterministic sensitivity analysis assessing baseline, best-case, and worst-case scenarios for the telemonitoring implementation.

We have updated the Study Description to remove the term 'randomly allocated' to avoid misunderstanding. This is a strictly observational study where participants receive interventions (NIV or NIV+TM) as part of routine medical care based on institutional availability and clinical criteria, not by investigator assignment. To minimize selection bias inherent to the observational nature of the study, a consecutive sampling methodology and a post-hoc matching or adjusted statistical analysis using a block-restrictive system based on clinical variables was utilized, ensuring the investigator does not prospectively assign interventions.

Inclusion Criteria:

1. Age between 50 and 90 years.
2. Confirmed diagnosis of Chronic Obstructive Pulmonary Disease (COPD) according to current Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria, demonstrating non-fully reversible airflow limitation with a Forced Expiratory Volume in 1 second (FEV1) < 50% of the predicted value confirmed by spirometry.
3. Persistent hypercapnia, defined as PaCO2 > 53 mmHg documented for at least two weeks following an acute COPD exacerbation.
4. History of two or more acute COPD exacerbations within the preceding year.
5. Signed written informed consent.

Exclusion Criteria:

1. Prior ongoing treatment with home non-invasive ventilation (NIV) or Continuous Positive Airway Pressure (CPAP).
2. Severe obstructive sleep apnea (OSA), defined as an Apnea-Hypopnea Index (AHI) >= 30.
3. Inability of the patient or the primary caregiver to comprehend or operate the telemonitoring and NIV procedures.
4. Estimated life expectancy of less than one year.
5. Terminal heart failure (New York Heart Association [NYHA] Class III-IV) or unstable angina.
6. Advanced renal insufficiency (creatinine clearance < 30%) or inclusion in an active dialysis program.
7. Hepatic cirrhosis or active inclusion in a liver transplant program.
8. Severe psychiatric illness requiring antipsychotic medication, active ongoing treatment for substance or alcohol addiction, or lack of a fixed home address upon hospital discharge.
9. Receipt of home palliative care.
10. Institutionalization.
11. Classification by the attending physician as non-compliant with medical therapies, treatments, or study protocols

The study population consists of adult patients diagnosed with severe, stable Chronic Obstructive Pulmonary Disease (COPD) and chronic persistent hypercapnia, who are managed and followed at public university hospitals within the Community of Madrid, Spain, and who have a recent history of frequent acute respiratory exacerbations.

Individual participant data will not be shared externally due to strict patient confidentiality, data privacy, and legal regulations. In compliance with Spanish Organic Law 3/2018 (GDPR implementation) and the Patient Autonomy Law 41/2002, the link between patient identity and their study code is exclusively known and held by their attending physician[cite: 660, 685, 690, 691]. All clinical data collected are managed within a closed, pseudonymized centralized electronic platform (ReseaArch®) under a strict role-based access control architecture. External distribution of raw individual datasets is neither covered by the patient informed consent nor approved by the participating institutional ethics committees.