TY - JOUR
T1 - Atelectasis, Shunt, and Worsening Oxygenation Following Reduction of Respiratory Rate in Healthy Pigs Undergoing ECMO
T2 - An Experimental Lung Imaging Study
AU - Spinelli, Elena
AU - Colussi, Giulia
AU - Dal Santo, Gaia
AU - Scotti, Eleonora
AU - Marongiu, Ines
AU - Garbelli, Erica
AU - Mazzucco, Alessandra
AU - Dondossola, Daniele
AU - Maia, Raquel
AU - Battistin, Michele
AU - Biancolilli, Osvaldo
AU - Rosso, Lorenzo
AU - Gatti, Stefano
AU - Mauri, Tommaso
N1 - Funding Information:
We wish to thank Samanta Oldoni for the logistical support in the animal laboratory. Funding. This present study was supported by institutional funding of the Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy (Ricerca corrente 2019) and by a grant from the Italian Ministry of Health, Rome, Italy (Ricerca Finalizzata 2016, project GR-2016-02362428).
Publisher Copyright:
© Copyright © 2021 Spinelli, Colussi, Dal Santo, Scotti, Marongiu, Garbelli, Mazzucco, Dondossola, Maia, Battistin, Biancolilli, Rosso, Gatti and Mauri.
PY - 2021/4/9
Y1 - 2021/4/9
N2 - Rationale: Reducing the respiratory rate during extracorporeal membrane oxygenation (ECMO) decreases the mechanical power, but it might induce alveolar de-recruitment. Dissecting de-recruitment due to lung edema vs. the fraction due to hypoventilation may be challenging in injured lungs. Objectives: We characterized changes in lung physiology (primary endpoint: development of atelectasis) associated with progressive reduction of the respiratory rate in healthy animals on ECMO. Methods: Six female pigs underwent general anesthesia and volume control ventilation (Baseline: PEEP 5 cmH2O, Vt 10 ml/kg, I:E = 1:2, FiO2 0.5, rate 24 bpm). Veno-venous ECMO was started and respiratory rate was progressively reduced to 18, 12, and 6 breaths per minute (6-h steps), while all other settings remained unchanged. ECMO blood flow was kept constant while gas flow was increased to maintain stable PaCO2. Measurements and Main Results: At Baseline (without ECMO) and toward the end of each step, data from quantitative CT scan, electrical impedance tomography, and gas exchange were collected. Increasing ECMO gas flow while lowering the respiratory rate was associated with an increase in the fraction of non-aerated tissue (i.e., atelectasis) and with a decrease of tidal ventilation reaching the gravitationally dependent lung regions (p = 0.009 and p = 0.018). Intrapulmonary shunt increased (p < 0.001) and arterial PaO2 decreased (p < 0.001) at lower rates. The fraction of non-aerated lung was correlated with longer expiratory time spent at zero flow (r = 0.555, p = 0.011). Conclusions: Progressive decrease of respiratory rate coupled with increasing CO2 removal in mechanically ventilated healthy pigs is associated with development of lung atelectasis, higher shunt, and poorer oxygenation.
AB - Rationale: Reducing the respiratory rate during extracorporeal membrane oxygenation (ECMO) decreases the mechanical power, but it might induce alveolar de-recruitment. Dissecting de-recruitment due to lung edema vs. the fraction due to hypoventilation may be challenging in injured lungs. Objectives: We characterized changes in lung physiology (primary endpoint: development of atelectasis) associated with progressive reduction of the respiratory rate in healthy animals on ECMO. Methods: Six female pigs underwent general anesthesia and volume control ventilation (Baseline: PEEP 5 cmH2O, Vt 10 ml/kg, I:E = 1:2, FiO2 0.5, rate 24 bpm). Veno-venous ECMO was started and respiratory rate was progressively reduced to 18, 12, and 6 breaths per minute (6-h steps), while all other settings remained unchanged. ECMO blood flow was kept constant while gas flow was increased to maintain stable PaCO2. Measurements and Main Results: At Baseline (without ECMO) and toward the end of each step, data from quantitative CT scan, electrical impedance tomography, and gas exchange were collected. Increasing ECMO gas flow while lowering the respiratory rate was associated with an increase in the fraction of non-aerated tissue (i.e., atelectasis) and with a decrease of tidal ventilation reaching the gravitationally dependent lung regions (p = 0.009 and p = 0.018). Intrapulmonary shunt increased (p < 0.001) and arterial PaO2 decreased (p < 0.001) at lower rates. The fraction of non-aerated lung was correlated with longer expiratory time spent at zero flow (r = 0.555, p = 0.011). Conclusions: Progressive decrease of respiratory rate coupled with increasing CO2 removal in mechanically ventilated healthy pigs is associated with development of lung atelectasis, higher shunt, and poorer oxygenation.
KW - atelectasis
KW - expiratory time
KW - extracorporeal membrane oxygenation
KW - respiratory rate
KW - shunt
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U2 - 10.3389/fphys.2021.663313
DO - 10.3389/fphys.2021.663313
M3 - Article
AN - SCOPUS:85104876814
VL - 12
JO - Frontiers in Physiology
JF - Frontiers in Physiology
SN - 1664-042X
M1 - 663313
ER -