This observational cohort study describes long-term survival and patient-reported health after intensive care unit (ICU) treatment for COVID-19-related acute respiratory distress syndrome (ARDS) in adults treated in a single center in Poland. The main questions it aims to answer are:

1. What is all-cause mortality up to 4 years after ICU admission for COVID-19-related ARDS?
2. Among long-term survivors, what are the health-related quality of life and functional outcomes approximately 4 years after ICU admission?
3. What rehabilitation use, return-to-work outcomes, and self-reported financial burden are reported during follow-up, and which acute-phase clinical and laboratory factors are associated with late mortality and long-term outcomes?

Participants did not receive any experimental intervention as part of this study. The study team collected clinical information from hospital and ICU records and conducted a structured telephone follow-up with survivors using standardized questionnaires (including EQ-5D-5L for quality of life, the modified Medical Research Council [mMRC] scale for breathlessness, and the Post-COVID-19 Functional Status [PCFS] scale for functional status), as well as questions about rehabilitation and work status.

This is an observational retrospective-prospective cohort study of adults treated in the intensive care unit (ICU) for COVID-19-related acute respiratory distress syndrome (ARDS) at a single center in Poland (University Hospital in Zielona Góra / Temporary COVID-19 Hospital in Zielona Góra). The cohort includes consecutive eligible ICU admissions between December 2020 and July 2021. No experimental intervention was assigned as part of this study.

Acute-phase clinical data were obtained from routinely collected hospital and ICU documentation. These data include baseline demographics, pre-existing comorbidities, severity of illness, and organ dysfunction at ICU admission, selected laboratory and physiological parameters, and key aspects of ICU management and clinical course. Long-term vital status was assessed for approximately 4 years after ICU admission, using available clinical records and follow-up procedures described in the protocol.

A structured telephone follow-up was conducted approximately 4 years after ICU admission among long-term survivors to collect patient-reported outcomes using standardized instruments and a predefined interview script. The follow-up assessment captured health-related quality of life, breathlessness, and functional status, and also included questions on post-discharge rehabilitation, return-to-work status, and self-reported financial burden related to recovery.

Analyses are descriptive and exploratory. Mortality over time is described using time-to-event methods, and associations between selected acute-phase variables and late mortality and long-term patient-reported outcomes are evaluated using multivariable models, with appropriate handling of missing data and sensitivity analyses as specified in the statistical analysis plan. The study was conducted with approval from the relevant ethics committee, and participant consent procedures for the follow-up interview were implemented in accordance with local requirements.

Time perspective: Retrospective extraction of acute-phase ICU data (December 2020-July 2021) with a single structured telephone follow-up of survivors approximately 4 years after ICU admission.

Inclusion Criteria:

Baseline cohort (retrospective ICU cohort)

• Adults (≥18 years) admitted to the Temporary Hospital in Zielona Góra ICU between December 2020 and July 2021
• Confirmed SARS-CoV-2 infection
• COVID-19-related acute respiratory distress syndrome (ARDS)
• Required invasive mechanical ventilation during ICU treatment

Prospective follow-up component (telephone interview):

• Confirmed alive at approximately 4 years after ICU admission
• Agreed to participate in a structured telephone interview (voluntary participation)

Exclusion Criteria:

Baseline cohort:

• None (no additional clinical exclusion criteria)

Prospective follow-up component (telephone interview):

• Declined participation in the telephone interview
• Unable to be reached after repeated contact attempts (non-responder)

Adults (≥18 years) treated in a single intensive care unit in Poland for COVID-19-related acute respiratory distress syndrome (ARDS) requiring invasive mechanical ventilation during the pandemic surge (December 2020-July 2021). Long-term survival was assessed for the full cohort up to approximately 4 years after ICU admission, and survivors were invited to a structured telephone follow-up to assess patient-reported outcomes.

The plan to share individual participant data (IPD) has not been finalized. Any future sharing would require additional ethics and data protection review and would be considered only in a de-identified form under a data use agreement. Aggregated results will be reported in publications.