Automatic Oxygen Titration in Patients After SARS-CoV-2 Infection

Effects of an Automatic Oxygen Titration vs. Constant Oxygen Flow Rates During Daily Activities in Patients After SARS-CoV-2 Infection

With the progression of the SARS-CoV-2 pandemic there's an increasing number of patients recovering from COVID19. Some of these patients still experience hypoxemia and therefore are still in need of a long-term oxygen therapy (LTOT), usually provided as a constant-flow. However, during a patient's daily activities, oxygenation levels may vary and the same constant flow may not be suitable for all tasks. Studies in COPD patients suggest that an automatic oxygen titration, which adjusts the oxygen flow automatically according to a patient's blood oxygen levels to prevent desaturations, could be beneficial compared to a constant oxygen titration during exercise. So far there are no studies available that directly compare the automatic oxygen titration with the patient's prescribed constant oxygen flow in patients with hypoxemia after SARS-CoV-2 infection during activities of daily life. Therefore, the primary outcome of this study is to investigate the effects of an automatic oxygen titration (O2matic, Denmark) in comparison to constant oxygen flow rates as prescribed according to guidelines.

Rationale After an infection with SARS-CoV-2, some patients still experience hypoxemia even after being discharged from the hospital. Long-term oxygen therapy (LTOT) is then used to increase the patients blood oxygen level and prolong the time spent within the SpO2 target range, decreasing the probability of severe hypoxemia or at least lowering the time spent in this severe hypoxemia and all in all enhance the patient's endurance. A prescription for LTOT is usually given for constant flow rates which might vary during day- and night use. This study is a randomized, controlled cross-over trial. Its aim is to investigate the effects of an automatic oxygen titration in patients after SARS-CoV-2 infection on the blood oxygen saturation level during activities of daily life (walking). Secondary, the effects of using an automatic titration on endurance, pCO2 blood level as well as heart rate and breathing frequency are compared to using the prescribed constant flow oxygen therapy. Design: Each patient undergoes a series of shuttle walk tests. After an initial incremental shuttle walk test (ISWT) to determine the patient's maximum walking speed, the patient undergoes 2 endurance shuttle walk tests (ESWTs) at 85% of the maximum walking speed. One of these ESWTs is performed with the prescribed constant oxygen flow, the other with the O2matic automatic oxygen titration in a random order. In addition to the shuttle walk tests, patient will perform two stair walking tests, again one with the prescribed constant oxygen flow, the other with the O2matic automatic oxygen titration in a random order. Furthermore, patients will be asked to rate their experienced comfort after each ESWT and to name their preferred oxygen titration system.

First Endurance Shuttle Walk Test using the automatic oxygen titration (O2matic) with the target range being 90 - 94% SpO2, the second Endurance Shuttle Walk Test using the prescribed constant flow oxygen therapy.

First Endurance Shuttle Walk Test using the prescribed constant flow oxygen therapy, the second Endurance Shuttle Walk Test using the automatic oxygen titration (O2matic) with the target range being 90 - 94% SpO2.

First Stair Walking Test using the automatic oxygen titration (O2matic) with the target range being 90 - 94% SpO2, the second Stair Walking Test using the prescribed constant flow oxygen therapy.

First Stair Walking Test using the prescribed constant flow oxygen therapy, the second Stair Test using the automatic oxygen titration (O2matic) with the target range being 90 - 94% SpO2.

Oxygen therapy during ESWTs and Stair Walking Test: one test using the prescribed constant oxygen flow and one using an automatic oxygen titration system. SpO2 target range: 90 - 94%

SpO2 measured by continuous transcutaneous recording via Sentec-Digital Monitor® (Sentec, Therwil, Switzerland)

tc pCO2 measured by continuous transcutaneous recording via Sentec-Digital Monitor® (Sentec, Therwil, Switzerland)

Heart rate measured by continuous transcutaneous recording via Sentec-Digital Monitor® (Sentec, Therwil, Switzerland)

Change of time to desaturation (SpO2 ≤ 90%) and to severe desaturation (SpO2 ≤ 85%) during ESWTs and Stair Walking Tests

SpO2 measured by continuous transcutaneous recording via Sentec-Digital Monitor® (Sentec, Therwil, Switzerland) and O2matic Device.

Inclusion Criteria: validated COVID19 disease in case history hypoxemia (PO2 < 55 mmHg) under room air conditions (rest or during exercise) or SpO2 <88% during exercise already established Long-term oxygen therapy or given indication for a Long-term oxygen therapy Exclusion Criteria: acute infection cardiovascular diseases that limit physical fitness orthopedic diseases preventing the patient from undergoing the walking tests

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