COVID-19 pneumonia: Guiding the decision to intubate based on independent assessment of oxygenation and work of breathing

ABSTRACT

With the emergence of COVID-19, healthcare worldwide is afflicted. While there is a spectrum of disease severity and presenting symptoms in infected patients, hypoxemic respiratory failure is the leading cause of mortality. Decision to intubate in rapidly deteriorating patients plays a significant role in determining patient outcome. In most patients, COVID-19 pneumonia initially causes worsening hypoxemia but minimal impairment of lung compliance which determines the work of breathing (WOB). Once adequate arterial oxygenation is established, a tool to determine WOB independent of oxygen needs can guide the decision to intubate for invasive mechanical ventilation (IMV). We monitored oxygen requirements and WOB in 14 patients admitted to our ICU with severe COVID-19 pneumonia. All patients had radiographic evidence of extensive lung disease, significant hypoxemia and multiple comorbidities. Hypoxemia was managed through non-invasive means, predominantly using highflow nasal cannula. To assess WOB, we used a scale developed by us assigning points to the respiratory rate and use of respiratory accessory muscles (range, 1 to 7) (Figure 1a). This was used at the time of initial evaluation and throughout the ICU stay. Out of 14 patients, 10 did not require intubation and recovered while 4 were intubated. We compared the maximum and average WOB of the non-intubated patients throughout their ICU stay with the WOB of intubated patients measured within 24 hours before intubation (Figure 1b). The maximal and the average WOB were higher in patients requiring intubation (mean ± SD, maximal 4.3 ± 0.9 vs 5.5 ± 1.0 pts, p = 0.028 and average 2.7 ± 0.6 vs 3.9 ± 0.5 pts, p = 0.002). Breakdown of the various WOB components demonstrated a statistically significantly higher maximal and average use of respiratory accessory muscles (assessed as their aggregate sum) and higher average respiratory rate in intubated patients. However, the maximal respiratory rate was not significantly higher. Our data illustrates the initial response to COVID-19 lung injury is tachypnea which can be sustained with adequate oxygenation. As lung injury progresses with more recruitment of respiratory accessory muscles, intubation for IMV becomes necessary. Our WOB scale becomes a useful tool to assist in the decision of when to intubate. It is simple to teach, apply and incorporate into routine patient assessment. We recommend routine and systematic WOB assessment to plan for orderly nonemergent intubations for IMV. Further refinement on the interventions recommended based on specific WOB level and other modifying factors is awaited.