Study population:

Adult patients with severe COVID-19 requiring oxygen therapy who were not endotracheally
intubated at the Department of Respiratory and Critical Care Medicine, Union Hospital,
Tongji Medical College, Huazhong University of Science and Technology were selected.

Diagnostic Criteria:

Diagnostic criteria for severe COVID-19: A diagnosis of severe COVID-19 is made when any
of the following criteria are met.

1. Presence of shortness of breath with an RR ≥ 30 beats/min.

2. Finger oxygen saturation ≤93% on air inhalation at rest.

3. Oxygenation index (arterial partial pressure of oxygen/oxygen concentration) ≤ 300
mmHg (1 mmHg = 0.133 kPa), or arterial partial pressure of oxygen ≤ 60 mmHg when
breathing air at rest.

4. Progressive worsening of clinical symptoms and pulmonary imaging showing the
significant progression of >50% of the lesion within 24 to 48 hours.

Inclusion criteria:

(1)age ≥ 18 years; (2) admitted with a confirmed diagnosis of severe COVID-19; (3)
Patients without endotracheal intubation requiring high flow nasal cannula, non-invasive
ventilator, mask, nasal cannula assisted ventilation; (4) signed informed consent.

Exclusion criteria:

(1)hemodynamic instability; (2) unstable spinal fractures; (3) unstable pelvic or long
bone fractures; (4) open abdominal wounds; (5) late pregnancy; (6) increased intracranial
pressure due to a lesion in the head and neck that obstructs cerebral venous drainage.

Content and methods:

Patients who met the study criteria were selected according to the inclusion and
exclusion criteria. Adult patients with confirmed severe COVID-19 and requiring oxygen
therapy were admitted to the Department of Respiratory and Critical Care Medicine, Wuhan
Union Hospital, from 2023.01.10 to 2024.01.10 without tracheal intubation were included.
Informed consent was obtained from the patients and their families and signed.
Investigators collected baseline data on demographics, anthropometrics, concomitant
diseases, arterial blood gases on admission, and oxygen therapy modalities and parameters
for all patients. After inclusion in the study, all patients were grouped into control
and intervention groups according to the treatment protocol and pulmonary imaging in
combination with the patient's wishes and tolerance of the position. According to
pulmonary imaging data, in the intervention group, arterial blood gases, heart rate,
blood pressure, finger pulse oxygen saturation, and inhaled oxygen concentration were
collected 30 minutes before ventilation in different positions (Time 1). Patients are
ventilated in a prone position (for patients with bilateral lung lesions), left/right
lateral position, semi-prone position (for patients with unilateral lung lesions or those
who cannot tolerate prone ventilation, so that the diseased lung is above and the healthy
lung is below), supine position (for patients who cannot tolerate prone ventilation or
lateral ventilation, etc.) according to the pulmonary imaging data. Arterial blood gases,
heart rate, blood pressure, finger pulse oxygen saturation, and inhaled oxygen
concentration were collected again when the patient was ventilated in different positions
for 2 hours (Time 2). Patients in the control group are ventilated comfortably according
to the treatment principles and their wishes. All patients were homogenized regarding
medication and ventilation during their hospitalization, except for the choice of
position during ventilation. The primary observation was 28-day mortality. Secondary
observations were oxygenation index (PaO2/FiO2) before and after a position change,
tracheal intubation rate, duration of respiratory support, length of stay, and comfort in
position.

The primary information recorded during the patient's hospitalization included: gender,
age, concomitant diseases, history of smoking, alcohol consumption, body mass index
(BMI), position and duration of ventilation. Prothrombin time (PT), activated partial
thromboplastin time (APTT), international normalized ratio (INR), B-type natriuretic
peptide (BNP), D dimer, leukocytes, platelets, lymphocytes, C-reactive protein (CRP),
procalcitonin (PCT), ferritin, inflammatory factors, liver function, renal function;
imaging information including lung CT; and disease-related scores, including acute
physiology and chronic health inquiry (APACHE) Ⅱ score, Glasgow Coma Scale (GCS),
sequential organ failure assessment (SOFA) score, etc.

Choice of ventilation modality:

All patients included in this study were non-endotracheally intubated patients with
severe COVID-19 who were routinely administered oxygen therapy during hospitalization.
Depending on the patient's condition, the oxygen therapy modalities used during the study
included the high-flow nasal cannula (HFNC), non-invasive ventilator, face mask, and
nasal cannula. Patients were ventilated by the same method before and after changing
positions.

Clinical Outcomes:

Primary clinical outcome: 28-day mortality. Secondary clinical outcomes: oxygenation
index (PaO2/FiO2) before and after a position change, endotracheal intubation rate,
duration of respiratory support, length of stay, hospital costs, and comfort in position.

Sample size:

The sample size for this project was calculated using the chi-square Contingency Table
(Chi-Square Tests) for the two rates in PASS 15.0 software. A literature review revealed
that the current use of prone ventilation in patients with severe COVID-19 is 67.36%. In
the study, the test level was α=0.05, and the test efficacy was 1 - β=0.9. The final
sample size was 100 cases, considering that some patients dropped out in the middle of
the study or could not tolerate it.

Statistical analysis and statistical methods:

The data obtained during the study were pre-collated. For continuous data, normality
tests were first performed. If all groups met normality, the Student's t-test was used
for comparison between groups. Otherwise, the non-parametric Wilcoxon rank sum test was
considered. For categorical variables, the χ2 test was used. Statistically significant
data were subjected to multivariate logistic regression analysis. Receiver operating
characteristic (ROC) and Delong's method were used to analyze the effect of oxygen
therapy in different positions on the prognosis of patients with severe COVID-19, with a
difference considered statistically significant at P < 0.05.

Statistical analysis of all data was performed through SPSS (IBM SPSS Statistics 26.0,
SPSS Inc., Chicago, IL) and R language (version 4.1.3, www.R-project.org/). All
statistical tests were two-sided, and statistical significance was set at 0.05.

Safety evaluation:

This study investigates the effect on oxygen saturation and prognosis of patients with
severe COVID-19 when oxygen therapy is administered in prone, lateral, supine, and
semi-recumbent positions. Healthcare staff also make rounds during the change of position
and will promptly deal with any dislodgement of the line to minimize harm to the patient
and not cause additional harm to the patient. In summary, this study was safe in its
implementation.

Adverse events:

In the event of the patient's condition deterioration or respiratory distress during the
program, treatment will be adjusted according to the patient's condition. Investigators
will monitor the patient's condition in real-time and perform endotracheal intubation if
necessary to minimize harm to the patient. The decision to withdraw from this clinical
study will be based on the patient's family's wishes.

Informed Consent Process:

Informed consent is completed before the subject's participation and continues throughout
the study. The ethics committee agrees to inform consent, and the subject reads the
informed consent form. The investigator will explain the process, answer questions from
the subject, and inform the subject of the possible risks and their rights. Before
agreeing to participate, the subject may discuss this with a family member or guardian.
The researcher must inform the subject that participation in the study is voluntary and
that they may withdraw from the study at any time during the study. A copy of the
informed consent form may be provided to the research subject for retention. The rights
and welfare of the research subjects will be protected, and it is stressed that the
quality of their medical care will not be compromised by their refusal to participate in
the study.

Privacy Protection:

All information collected in this study is managed with particular confidentiality, and
any study information cannot be disclosed to unauthorized third parties without prior
approved consent.

Quality control and quality assurance:

All clinical data in this project were obtained from the inpatient case management system
of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology.
Patients with COVID-19 were screened according to the inclusion criteria, and clinical
data were collected. The data collected did not include the content of the patient's
privacy section, and all quality management and quality control were supervised and
managed by one person. The investigators received systematic methodological training at
the start of the project.

Data collection and management:

The data for this study were obtained from the medical records of inpatients within the
Wuhan Union Hospital. All data were transparent, accurate, and traceable. A clinical
database was established during the study, which was password-protected and complied with
logical proofreading procedures.

Study data retention:

All raw data and original documentation required for this project will be retained until
at least three years after the end of the clinical trial, and permission should be
obtained before destruction.

Declarations of interest:

The investigators have disclosed that they do not have any conflicts of interest.