May 1, 2020

COVID-19 NIV: Helmet vs Mask

Background: Over the past few weeks there has been a shift in the management of critically ill COVID-19 patients.  Many seem to have moved away from an intubate early strategy to the use of high flow nasal cannula (HFNC) and noninvasive ventilation (NIV).  HFNC and NIV may obviate the need for endotracheal intubation in patients with acute respiratory failure.  Mechanical ventilation is not a benign intervention as it has a number of associated complications including ventilator associated pneumonia, excessive sedation, delirium, ICU acquired weakness, as well as ventilator induced lung injury (VILI). NIV can cause lung injury from excessive negative pressure forces.  However, mechanical ventilation can cause VILI from excessive positive pressure forces.  There is a fine balance of when to use which modality, and when to transition from one modality to another that requires frequent bedside monitoring.  NIV has been used successfully for COPD exacerbations and cardiogenic pulmonary edema, but its use in acute hypoxemic respiratory failure is still rather controversial.  One of the issues with NIV through a mask device is that higher levels of positive end-expiratory pressure (PEEP), which are often needed in hypoxemic conditions, may lead to mask intolerance and air leaks around the sides of the mask.  Helmet NIV may have several advantages over face masks including better tolerability and less air leaks.  There is a dearth of evidence comparing these to NIV modalities....Read More