Individual response in patient's effort and driving pressure to variations in assistance during pressure support ventilation

Mattia Docci; Emanuele Rezoagli; Maddalena Teggia-Droghi; Andrea Coppadoro; Matteo Pozzi; Alice Grassi; Isabella Bianchi; Giuseppe Foti; Giacomo Bellani

doi:10.1186/s13613-023-01231-9

Individual response in patient's effort and driving pressure to variations in assistance during pressure support ventilation

Ann Intensive Care. 2023 Dec 20;13(1):132. doi: 10.1186/s13613-023-01231-9.

Authors

Mattia Docci¹, Emanuele Rezoagli^{1

2}, Maddalena Teggia-Droghi², Andrea Coppadoro², Matteo Pozzi², Alice Grassi³, Isabella Bianchi⁴, Giuseppe Foti^{1

2}, Giacomo Bellani^{5

6}

Affiliations

¹ School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
² Department of Emergency and Intensive Care, Fondazione IRCCS San Gerardo Dei Tintori, Monza, Italy.
³ Department of Anesthesia and Pain Medicine, Toronto General Hospital, Toronto, ON, Canada.
⁴ Department of Anesthesia and Intensive Care, ASST Papa Giovanni XXIII, Bergamo, Italy.
⁵ Centre for Medical Sciences-CISMed, University of Trento, Trento, Italy. giacomo.bellani@apss.tn.it.
⁶ Department of Anesthesia and Intensive Care, Santa Chiara Hospital, APSS Trento Largo Medaglie d'Oro Trento, Trento, Italy. giacomo.bellani@apss.tn.it.

Abstract

Background: During Pressure Support Ventilation (PSV) an inspiratory hold allows to measure plateau pressure (Pplat), driving pressure (∆P), respiratory system compliance (Crs) and pressure-muscle-index (PMI), an index of inspiratory effort. This study aims [1] to assess systematically how patient's effort (estimated with PMI), ∆P and tidal volume (Vt) change in response to variations in PSV and [2] to confirm the robustness of Crs measurement during PSV.

Methods: 18 patients recovering from acute respiratory failure and ventilated by PSV were cross-randomized to four steps of assistance above (+ 3 and + 6 cmH₂O) and below (-3 and -6 cmH₂O) clinically set PS. Inspiratory and expiratory holds were performed to measure Pplat, PMI, ∆P, Vt, Crs, P0.1 and occluded inspiratory airway pressure (Pocc). Electromyography of respiratory muscles was monitored noninvasively from body surface (sEMG).

Results: As PSV was decreased, Pplat (from 20.5 ± 3.3 cmH₂O to 16.7 ± 2.9, P < 0.001) and ∆P (from 12.5 ± 2.3 to 8.6 ± 2.3 cmH₂O, P < 0.001) decreased much less than peak airway pressure did (from 21.7 ± 3.8 to 9.7 ± 3.8 cmH2O, P < 0.001), given the progressive increase of patient's effort (PMI from -1.2 ± 2.3 to 6.4 ± 3.2 cmH₂O) in line with sEMG of the diaphragm (r = 0.614; P < 0.001). As ∆P increased linearly with Vt, Crs did not change through steps (P = 0.119).

Conclusion: Patients react to a decrease in PSV by increasing inspiratory effort-as estimated by PMI-keeping Vt and ∆P on a desired value, therefore, limiting the clinician's ability to modulate them. PMI appears a valuable index to assess the point of ventilatory overassistance when patients lose control over Vt like in a pressure-control mode. The measurement of Crs in PSV is constant-likely suggesting reliability-independently from the level of assistance and patient's effort.

Keywords: Acute respiratory failure; Artificial ventilation; Breathing effort; Driving pressure; Monitoring; Pressure muscle index; Pressure support ventilation; Respiratory system compliance.