Table 1 Inclusion and exclusion criteria

Demographic characteristics

Adult (18 years old ≤ age ≤ 80 years old) immunocompromised patients with moderate to severe ARF diagnosed within the last 72 h.

Age < 18 or >80 years old.

Diagnosis of mid to severe ARF

85 ≤ PaO₂/FiO₂ ≤ 170 adjusted with altitude change or clinically diagnosed with evidence of respiratory distress (intercostal recession or other assisted breathing muscle movements, polypnea >35/min or dyspnea at rest).

(1) Partial pressure of arterial carbon dioxide (PaCO₂) > 50 mmHg or arterial pH < 7.20;

(2) PaO₂/FiO₂ > 170(mild) or PaO₂/FiO₂ < 85(severe);

Diagnosis of immunocompromised status

At least one of the following:

(1) Hematologic malignancy or solid tumor under chemotherapy;

(2) Solid organ or stem cell transplant;

(3) Long-term (>30 days) and high dose steroids (>1 mg/kg/d prednisone equivalent) usage and/or any other immunosuppressive drugs;

(4) Neutropenia (defined as a neutrocyte count of <1.0 × 109/L) showing for at least 48 h.

Other causes of immunocompromise including HIV infection, etc.

Indications for intervention

Patients with severe ARF described above, in which mechanical ventilation is indicated.

Patients have been treated with NIV, IMV or high-flow oxygen therapy within 30 days. NIV is contraindicated or intubation is inevitable, which including PaO₂/FiO₂ < 85, respiratory arrest, hemodynamic instability, inability to fit the face mask, pneumothorax, vomiting, development of airway bleeding, inability to protect the airway, or copious respiratory secretions.

Morbidities

Mild diseases not stated in the exclusion criteria.

Acute cardiac failure; Acute-on-chronic ARF; Other severe diseases including dilated cardiomyopathy, valvular heart disease, cardiogenic pulmonary edema, implanted cardiac pacemaker, or acute coronary syndrome; systolic arterial pressure < 90 mmHg after optimal fluid therapy; history of chronic obstructive pulmonary disease (COPD) or asthma; impaired consciousness (Glasgow Coma Scale score < 8) [32]; postoperative acute respiratory failure; pregnancy or breastfeeding.

Others

Informed consent to participate in the study signed by the patient or their authorized surrogate decision maker

Lack of consent, do-not-intubate decision, and any other situations where obvious bias are expected.