The investigation of various titration techniques aimed at determining the most effective positive end expiratory pressure (PEEP) for individuals suffering from acute exacerbations of chronic obstructive pulmonary disease (AECOPD)

Approved 12/09/2022, Medical Ethics Committee of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine (Sir Run Run Shaw Hospital, 3 Qingchun Dong Lu, Shangcheng District, Hangzhou, 310016, China; +86 86006811; 594961420@qq.com), ref: 2022, No. 0332

In NIV group
1. The patients were ventilated at supine position with mechanical ventilation settings as follows: S/T mode, RR12 bpm, Pressure support (PS) was set at 6 cmH2O, and then progressively modified, according to tidal volume (Vte/kg of PBW), in order to target a Vte/kg of 6 ~8 mL/kg PBW and a spontaneous RR lower than 24 breaths/min, FiO2 was increased to target a SpO2 ≥90%; The oronasal facemask was finely adjusted to target a leak flow lower than 20 L/min. The inspiratory trigger was set at medium and respiratory cycling was set at medium of the inspiratory peak flow.
2. A multifunctional nasogastric tube was placed, and then EIT was connected. Once the patient was used to the experimental setting and appeared to be relaxed, measurements were performed: PEEP titration was initially set at 4 cmH2O（because that the lowest PEEP of NIV is currently 4 cmH2O), and subsequently increased by 1 cm H2O every 10 minutes, until to EIT showed that EELI was significantly elevated. All measurements were performed during a relatively stable spontaneous breathing pattern of 10 minutes and results were averaged for each assessment step.
3. Data recording
3.1. Esophageal pressure measurements: The ΔPes, PEEPi,dyn, PEEPtot, trigger delay, asynchrony index measured by esophageal pressure during PEEP titration were recorded offline.
3.2. EIT measurements: ∆EELI. The value of ∆EELI was the average of the change in EELI for any 10 breaths per PEEP (compared with PEEP 4cmH2O).
We defined the optimal PEEP as “The PEEPtot curves traced during PEEP titration were recorded offline, and the inflection point before the steep rise of the curve was selected as the best PEEP point; if not, 4cmH2O was selected as the optimal PEEP. ” We observed the performance of PEEPi,dyn, ΔPes, trigger delay, asynchrony index, and ∆EELI at optimal PEEP.

Invasive mechanical ventilation group:
1. Spontaneous breathing phase
the patients were ventilated at supine position with mechanical ventilation settings as follows: PCV mode, RR12 bpm, Pressure support (PS) was set to target a Vte/kg of 6 ~8 mL/kg PBW and a spontaneous RR lower than 24 reaths/min,FiO2 was increased to target a SpO2 ≥90%. A multifunctional nasogastric tube was placed, and then EIT was connected.
Then measurements were performed: PEEP titration was initially set at 0 cmH2O,and subsequently increased 2 cmH2O every 10 minutes, until to EIT showed that EELI was significantly elevated.
All measurements were performed during a relatively stable spontaneous breathing pattern of 10 minutes and results were averaged for each assessment step. We chose 80% of PEEPi,dyn as the optimal PEEP based on esophageal pressure (measured at PEEP0). We chose PEEP at the lowest RVD as the optimal PEEP.
2. Deep sedation phase
Then placed the patient under deep sedation, we performed three end-expiratory occlusions and take the average as PEEPi.
3. Data recording
3.1. Esophageal pressure measurements: The ΔPes, trigger delay, and asynchrony index measured by esophageal pressure during PEEP titration were recorded offline.
3.2. EIT measurements: ∆EELI, GI.
We compare the trigger delay, ∆Pes, asynchrony index, GI under the optimal PEEP obtained by these three methods.

There are no secondary outcome measures