Validation of Airway Occlusion Pressure as a Method of Assessing Breathing Effort During Noninvasive Ventilation

Background: The airway-occlusion pressure is used to estimate the muscle pressure ($$) and the occlusion pressure at 100 ms ($$) to assess respiratory drive in patients on mechanical ventilation. However, the validity of these maneuvers during noninvasive ventilation (NIV) has not been evaluated. This study was designed to validate the airway-occlusion pressure and the $$ described for mechanical ventilation during NIV in a bench model. Methods: This was a bench observational prospective study carried out during January and February 2024 in the ICU laboratory of the Hospital Británico of Buenos Aires. Results: In the non-leakage NIV scenarios with oronasal and total face mask, the NIV-airway-occlusion pressure increased with greater $$ (P < .001). For a programmed $$ of 5 cm H₂O, values around 4.5 cm H₂O were recorded for both oronasal and total face masks. At 10 cm H₂O, the values were ∼8 cm H₂O, and at 15 cm H₂O, they were ∼11 cm H₂O. With leaks, this difference worsened as leakage increased and the effort decreased. In the Bland-Altman analysis between mechanical ventilation-airway-occlusion pressure and NIV-airway-occlusion pressure without leakage for oronasal and total face masks, we found a good agreement for the 3 levels of $$ with both types of masks. With regard to the values of NIV-airway-occlusion pressure with the helmet, Bland-Altman analysis showed a high bias and random error. Multivariate analysis found that NIV-airway-occlusion pressure depends on the type of interface, increased with $$, and decreased as leakage increased. The agreement of NIV-$$ was not good across all noninvasive measurements. Conclusions: This study constitutes a relevant contribution in the validation of indices to assess $$ during NIV. In a laboratory setting, the measurement of airway-occlusion pressure in NIV may be used to assess effort estimation in the absence of leakage; however, it will likely be underestimated. $$ proved to be an unreliable method. These findings suggest the feasibility of assessing muscle effort during NIV.