COVID-19 Hypoxemia: Detecting the Presence of Concomitant Intra-Pulmonary or Intra-Cardiac Shunts with Contrast Bubble Studies (COVID-Shunt Study)

LeadDr. Vincent Lau

Co-Investigators: Peter Brindley, Jim Kutsogiannis, Michael Jacka, Oleksa Rewa, Sean
Bagshaw, Aws Alherbish, Matt Wheatley, Jonathan Windram, Andrew Shaw, Leon Byker,
Dustin Anderson, Graham Mah, Brian Buchanan

Background: Patients with COVID-19 often have low blood oxygen levels despite less affected
lung. Early laboratory data suggests that blood is bypassing the lungs (i.e. causing a “shunt”).
This theory is also supported by autopsies and computed tomography (CT) scans that suggest
dilatation blood vessels in the lungs. Recently, US researchers used micro-bubbles to look for
shunts in patients with COVID-19 pneumonia using ultrasound of brain vessels (transcranial
Doppler [TCD]), in a high number of severe adult ICU COVID-19 patients (15 of 18, 83%). Other
researchers found that ~30% of patients had shunts in COVID-19 patients (20% heart, 10%
lungs) during external heart ultrasound (transthoracic echocardiogram). However, the more
definitive test to tell whether the shunt is coming from the heart or lungs (transesophageal
echocardiogram, TEE) was not performed, despite its recommended use from the American
Society of Echocardiography.

Methods Perform a single-center, pilot feasibility, prospective observational cohort study looking at a step-wise protocol with TTE/TCD/TEE bubble studies (see Figure 1) to assess for:                   

  • The presence or absence of shunts in patients with bilateral pneumonia (with andwithout COVID-19) who are on life support (e.g. mechanical ventilation).
  • Inclusion criteria: all adult intubated, mechanically ventilated ICU patients (with or​ without COVID)
  • Exclusion criteria: contraindication to receiving a TEE bubble study

Statistical Analysis Plan:

  • Our primary objective is to determine feasibility of recruitment of COVID and non-COVID  patients into our feasibility study.
  • Our secondary objectives are to: directly determine the presence or absence of shunt in​  adult patients with pneumonia (COVID-19 included) who are on life support (i.e. mechanical ventilator); and evaluate important demographics and characteristics of COVID and non-COVID patients with or without shunts
  • We will investigate clinical outcomes associated with the presence/absence of shunt, including mortality (90-days). We will also determine if there is a connection with shunt presence and severely low oxygen levels.
  •  Other patient-centered outcomes of interest include: time duration on the ventilator, ICU and hospital LOS, tracheostomy and adverse event rates (myocardial infarction or heart attack, cardiac arrest, stroke, shock, TEE complications). We will be collecting mechanical ventilator parameter data (e.g. lung compliance or stiffness), and anypertinent standard bloodwork (arterial blood gases, D-dimers indicative of life threateningblood clots).