In this study, we retrospectively will investigate safety and efficacy of NAC dose given in paracetamol toxicity as an adjuvant therapy in critically ill COVID-19 patients with acute respiratory distress and determine whether NAC in high doses can avoid respiratory failure in patients with COVID-19.

Type of Study:Retrospective Observational Cohort Study. Study Setting: Ain shams university hospitals . Study Period: from December 2020 to February 2022 Study Population:Patients aged 18 years or older of both genders diagnosed with confirmed critically ill COVID-19 .

This is a retrospective observational study in which all cases will be collected from ICU of Ain shams university hospitals during COVID-19 outbreak. All data will be extracted from clinical records. All patients initially admitted to ICU with SPO2 less than 94 % will be included between December 2020 to February 2022. Infection with COVID-19 was confirmed by PCR. All patients received standard care, according to the institutional protocol.

Laboratory and Radiological Investigations Demographic, clinical, laboratory, management, and outcome data will be obtained from the medical records. Routine laboratory tests were done for all patients, including CBC, C-reactive protein, renal profile, coagulation profile, liver profile, lactate, electrolytes, procalcitonin, ferritin and D-dimer.Infection with COVID-19 was confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR) assay of nasopharyngeal swab. Chest computed tomography (CT) was also done for all patients.

Inclusion Criteria:

• Oxyhemoglobin saturation (SaO2) of less than 94% while breathing ambient air

Exclusion Criteria:

• Need for immediate mechanical ventilation on admission, known allergy or hypersensitivity to NAC, end stage renal and liver diseases, heart failure and pregnancy.

Patients aged 18 years or older of both genders diagnosed with confirmed critically ill COVID-19