Hubungan kadar PaO2, PaCO2 dan elektrolit serum dikaitkan dengan waktu kesintasan pasien coronavirus disease (COVID-19) yang menggunakan ventilasi mekanis di RSUP Persahabatan = Association between survival time and PaO2, PaCO2 and serum electrolyte levels of COVID-19 patients receiving mechanical ventilation treated at a National Respiratory Center in Jakarta, Indonesia