The most appropriate time for intubation per se is a dilemma in hypoxic patients due to lack of standard endotracheal intubation criteria (5) and it became more challenging in a pandemic with huge number of patients with severe COVID-19 and worldwide resource limitation. Also, invasive ventilation in COVID patients is being between Scylla and Charybdis (6) (7). It can be lifesaving by improvement in oxygenation and amelioration of virus spread, on the other hand it could be life threatening by increasing ventilator induced lung injury (VILI) and resource consuming (8).
In COVID patients it seems that the lower saturation could be better tolerated than the other hypoxic patients so maybe just the percent of O2 saturation should not be considered as a trigger for intubation (8). Therefore, criteria for invasive ventilation in these patients is debatable. In this study discharge rate of intubated and non-intubated patients who had severe respiratory symptoms at the time of decision making for intubation, were compared. We found that 96.6% of patients that had O2 saturation of 60-90% and were intubated died whilst in those who were not intubated with this range of O2 saturation, mortality rate was 66.7%. This is obvious that mortality rate should be higher in intubated group, due to their worse general condition and their need for invasive respiratory support, but the interesting part in this result is discharge rate of 33.3% in patients with low O2 saturation that were not intubated in compare to less than 4% in intubated group. It could show us maybe decreasing O2 saturation below 90% even to 60% is not good criteria for starting mechanical ventilation of patients with COVID infection. The findings of Yong Hoon et al in 2020 can be in favor of ours that show early intubation is not associate with improvement in survival. In their study early intubation was defined as intubation in the first day of meeting ARDS criteria in patients with COVID-19 (9).
In evaluation of other signs and symptoms for intubation we found limited studies that mostly suggest their own clinical criteria and the lack of evidence based guidelines for the best time to start mechanical ventilation was noticeable. In an observational cohort study by Ahmad et al in 2020 on 150 intubated patients, association between early intubation and improvement in outcome was shown. As they mentioned their data is not a definitive evidence for early vs late intubation, but they suggest that if tracheal intubation is considered based on following criteria they could have better clinical outcome and staff safety. Their criteria is : O2 Saturation<92%, FiO2 requirement of more than 60%, respiratory rate of more than 25 per minute, increase work of breathing and failure adequate oxygenation in 4-hour prone position (10). In another study severity of respiratory failure, multi-organ failure, hemodynamic shock and multiple high risk condition are suggested as institutional intubation criteria. Of course all these conditions dependent on availability of ventilators and intensive care capacity (11). In our study we tried to detect respiratory distress in detailed. Among various respiratory symptoms, we found that mortality rate in patients with respiratory rate ≥ 30/min and abdominal breathing who were intubated are significantly higher than patients with these symptoms who were not intubated. We found that intubation did not decrease mortality in patients with respiratory rate ≥ 30/min and abdominal breathing and could not be suitable criteria for intubation.
In our cases with severe subjective dyspnea and decreased level of consciousness we had patients who were discharged after intubation but all of the non- intubated patients died. It was not statistically significant but clinically could be important. Therefore, evaluating patients’ subjective dyspnea and decreased level of consciousness could be considered as valuable variables for future studies (Table - 3).
Table 3
Clinical symptoms
|
Intubation criteria
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O2 Saturation 60-90%
|
Not a good criteria
|
Respiratory Rate > 30/min
|
Not a good criteria
|
Heated cough
|
Not a good criteria
|
Abdominal breathing
|
Not a good criteria
|
Severe subjective dyspnea
|
Could be a criteria
|
Decreased level of consciousness
|
Could be a criteria
|
Our limitation in this study was limited number of patients, because data gathering during pandemic situation was difficult. Also, in pandemic situation mortality rate can be affected by resource limitations. For defining a guideline for intubation in COVID patients maybe aggregation of more study with huge number of data could be helpful.