Working accuracy of pulse oximetry in COVID-19 patients stepping down from intensive care: a clinical evaluation.

INTRODUCTION: UK guidelines suggest that pulse oximetry, rather than blood gas sampling, is adequate for monitoring of patients with COVID-19 if CO2 retention is not suspected. However, pulse oximetry has impaired accuracy in certain patient groups, and data are lacking on its accuracy in patients with COVID-19 stepping down from intensive care unit (ICU) to non-ICU settings or being transferred to another ICU. METHODS: We assessed the bias, precision and limits of agreement using 90 paired SpO2 and SaO2 from 30 patients (3 paired samples per patient). To assess the agreement between pulse oximetry (SpO2) and arterial blood gas analysis (SaO2) in patients with COVID-19, deemed clinically stable to step down from an ICU to a non-ICU ward, or be transferred to another ICU. This was done to evaluate whether the guidelines were appropriate for our setting. RESULTS: Mean difference between SaO2 and SpO2 (bias) was 0.4%, with an SD of 2.4 (precision). The limits of agreement between SpO2 and SaO2 were as follows: upper limit of 5.2% (95% CI 6.5% to 4.2%) and lower limit of -4.3% (95% CI -3.4% to -5.7%). CONCLUSIONS: In our setting, pulse oximetry showed a level of agreement with SaO2 measurement that was slightly suboptimal, although within acceptable levels for Food and Drug Authority approval, in people with COVID-19 judged clinically ready to step down from ICU to a non-ICU ward, or who were being transferred to another hospital's ICU. In such patients, SpO2 should be interpreted with caution. Arterial blood gas assessment of SaO2 may still be clinically indicated.

Rescue therapy with thrombolysis in patients with severe COVID-19-associated acute respiratory distress syndrome.

Acute respiratory distress syndrome in patients with Coronavirus disease 19 is associated with an unusually high incidence of pulmonary embolism and microthrombotic disease, with evidence for reduced fibrinolysis. We describe seven patients requiring invasive ventilation for COVID-19-associated acute respiratory distress syndrome with pulmonary thromboembolic disease, pulmonary hypertension ± severe right ventricular dysfunction on echocardiography, who were treated with alteplase as fibrinolytic therapy. All patients were non-smokers, six (86%) were male and median age was 56.7 (50-64) years. They had failed approaches including therapeutic anticoagulation, prone ventilation (n = 4), inhaled nitric oxide (n = 5) and nebulised epoprostenol (n = 2). The median duration of mechanical ventilation prior to thrombolysis was seven (5-11) days. Systemic alteplase was administered to six patients (50 mg or 90 mg bolus over 120 min) at 16 (10-22) days after symptom onset. All received therapeutic heparin pre- and post-thrombolysis, without intracranial haemorrhage or other major bleeding. Alteplase improved PaO2/FiO2 ratio (from 97.0 (86.3-118.6) to 135.6 (100.7-171.4), p = 0.03) and ventilatory ratio (from 2.76 (2.09-3.49) to 2.36 (1.82-3.05), p = 0.011) at 24 h. Echocardiographic parameters at two (1-3) days (n = 6) showed right ventricular systolic pressure (RVSP) was 63 (50.3-75) then 57 (49-66) mmHg post-thrombolysis (p = 0.26), tricuspid annular planar systolic excursion (TAPSE) was unchanged (from 18.3 (11.9-24.5) to 20.5 (15.4-24.2) mm, p = 0.56) and right ventricular fractional area change (from 15.4 (11.1-35.6) to 31.2 (16.4-33.1)%, p = 0.09). At seven (1-13) days after thrombolysis, using dual energy computed tomography imaging (n = 3), average relative peripheral lung enhancement increased from 12.6 to 21.6% (p = 0.06). In conclusion, thrombolysis improved PaO2/FiO2 ratio and ventilatory ratio at 24 h as rescue therapy in patients with right ventricular dysfunction due to COVID-19-associated ARDS despite maximum therapy, as part of a multimodal approach, and warrants further study.