by Christoph
Boesing, Joerg Krebs, Alice Marguerite Conrad, Matthias Otto, Grietje Beck,
Manfred Thiel, Patricia R. M. Rocco, Thomas Luecke and Laura Schaefer
Critical Care volume 28,
Article number: 82 (2024) Published: 15
March 2024
Background
Prone positioning (PP) homogenizes ventilation distribution
and may limit ventilator-induced lung injury (VILI) in patients with moderate
to severe acute respiratory distress syndrome (ARDS). The static and dynamic
components of ventilation that may cause VILI have been aggregated in
mechanical power, considered a unifying driver of VILI. PP may affect
mechanical power components differently due to changes in respiratory
mechanics; however, the effects of PP on lung mechanical power components are
unclear. This study aimed to compare the following parameters during supine
positioning (SP) and PP: lung total elastic power and its components (elastic
static power and elastic dynamic power) and these variables normalized to
end-expiratory lung volume (EELV).
Methods
This prospective physiologic study included 55 patients with
moderate to severe ARDS. Lung total elastic power and its static and dynamic
components were compared during SP and PP using an esophageal pressure-guided
ventilation strategy. In SP, the esophageal pressure-guided ventilation
strategy was further compared with an oxygenation-guided ventilation strategy
defined as baseline SP. The primary endpoint was the effect of PP on lung total
elastic power non-normalized and normalized to EELV. Secondary endpoints were
the effects of PP and ventilation strategies on lung elastic static and dynamic
power components non-normalized and normalized to EELV, respiratory mechanics,
gas exchange, and hemodynamic parameters.
Results
Lung total elastic power (median [interquartile range]) was
lower during PP compared with SP (6.7 [4.9–10.6] versus 11.0 [6.6–14.8]
J/min; P < 0.001) non-normalized and normalized to EELV (3.2 [2.1–5.0]
versus 5.3 [3.3–7.5] J/min/L; P < 0.001). Comparing PP with SP,
transpulmonary pressures and EELV did not significantly differ despite lower
positive end-expiratory pressure and plateau airway pressure, thereby reducing
non-normalized and normalized lung elastic static power in PP. PP improved gas
exchange, cardiac output, and increased oxygen delivery compared with SP.
Conclusions
In patients with moderate to severe ARDS, PP reduced lung
total elastic and elastic static power compared with SP regardless of EELV
normalization because comparable transpulmonary pressures and EELV were
achieved at lower airway pressures. This resulted in improved gas exchange,
hemodynamics, and oxygen delivery.
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