Evaluation of Tracheal Pressure During Invasive CPAP Ventilation

<h3>Background</h3> Intubated but spontaneously breathing patients in the ICU frequently are treated with CPAP ventilation during weaning from mechanical ventilation. However, depending on the patient's inspiratory effort, a pressure gradient along the airway may arise, potentially even leading to negative values at the tracheal space. <h3>Research Question</h3> Does a significant difference exist in tracheal and airway measured inspiratory pressure? <h3>Study Design and Methods</h3> Twenty patients in the ICU were enrolled (median age, 68 years [interquartile range (IQR), 63-73 years]; 4 female patients). During a set positive end-expiratory pressure (PEEP) of 10 cm H₂O, the tracheal pressure course was recorded. Subsequently, a comparison of tracheal and artificial airway pressures was performed during CPAP and after applying a pressure support of 4 cm H₂O (pressure support ventilation [PSV]) or automatic tube compensation (ATC). <h3>Results</h3> As a primary outcome parameter, the median inspiratory pressure measured in the trachea was significantly lower than simultaneously measured airway pressures (median, 2.7 cm H₂O [IQR, 0.2-3.7 cm H₂O] vs 9.0 cm H₂O [IQR, 8.5-9.2 cm H₂O]; <i>P</i> < .001). In 5 patients, negative tracheal pressures were recorded. Secondary outcome parameters revealed comparable end-expiratory pressures, but significantly higher peak and lower mean pressures when measured in the trachea. Adding PSV or ATC slightly attenuated this inspiratory pressure drop, leading to a significant increase in inspiratory tracheal pressures. <h3>Interpretation</h3> Our results show that in intubated, spontaneously breathing patients in the ICU with a set PEEP of 10 cm H₂O, the nadir of tracheal pressures during inspiration is significantly lower than airway pressures measured by the ventilator. Consistently positive tracheal pressures cannot be guaranteed by CPAP throughout the respiratory cycle. Assisted ventilation with PSV or ATC is capable of reducing the pressure drop during inspiration. <h3>Clinical Trial Registration</h3> ClinicalTrials.gov; No.: NCT05679635; URL: www.clinicaltrials.gov