In the present study, we found that breath-by-breath P0.1aw measured by the Hamilton C6 on quasi-occlusion significantly correlated with P0.1es and ∆Pes. The threshold value of P0.1aw for high respiratory drive was calculated at approximately 1.0 cmH2O from both regression equations. Additionally, P0.1aw was equivalent to a quarter of P0.1es.
A previous study reported the nominal range for P0.1aw measured with airway occlusion to be between 0.5 and 1.5 cmH2O . Another previous study reported airway P0.1 with occlusion above 3.5 cmH2O to be associated with high respiratory drive . In contrast, the airway P0.1 measured on quasi-occlusion may result in underestimation of these values . Our findings suggest a lower threshold of P0.1 measured on quasi-occlusion utilizing the Hamilton C6 than that which has been previously reported.
It should be noted that clinical threshold of the P0.1 value for high respiratory drive and inspiratory effort described in the present study is not universally applicable to other ventilators. This is because we exclusively assessed P0.1 measurements using a single ventilator (Hamilton C6). The generalizability would be limited since each manufacturer utilizes its own proprietary software to estimate P0.1. For instance, Getinge group Servo I and U ventilators also provide P0.1 values without airway occlusions. Beloncle et al.  showed that the absolute values of P0.1 measurements vary between ventilator manufacturers. It should be further highlighted that under ideal circumstances as of November 2022, airway P0.1 with occlusion should be adopted as a standard reference; however, the Hamilton C6 ventilator does not include a function to measure airway P0.1 with occlusion. Therefore, we adopted esophageal P0.1 and esophageal swing for high respiratory drive and inspiratory effort, respectively as surrogates .
In patients with COVID-19, the evaluation of respiratory drive and inspiratory effort are critical due to concerns of P-SILI. A P0.1aw value measured on quasi-occlusion of approximately 1.0 cmH2O or higher may suggest a high respiratory drive and inspiratory effort. P0.1aw may be equivalent to a quarter of P0.1es on Hamilton C6.