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. 2022 Mar;10(6):e15225.
doi: 10.14814/phy2.15225.

Mechanical power thresholds during mechanical ventilation: An experimental study

Federica Romitti  1 , Mattia Busana  1 , Maria Michela Palumbo  1 , Matteo Bonifazi  1 , Lorenzo Giosa  1 , Francesco Vassalli  1 , Alessandro Gatta  2 , Francesca Collino  3 , Irene Steinberg  1 , Simone Gattarello  1 , Stefano Lazzari  1 , Paola Palermo  1 , Ahmed Nasr  4 , Ann-Kathrin Gersmann  5 , Annika Richter  5 , Peter Herrmann  1 , Onnen Moerer  1 , Leif Saager  1   6 , Luigi Camporota  7 , John J Marini  8 , Michael Quintel  1 , Konrad Meissner  1 , Luciano Gattinoni  1
Affiliations

Mechanical power thresholds during mechanical ventilation: An experimental study

Federica Romitti et al. Physiol Rep. 2022 Mar.

Abstract

The extent of ventilator-induced lung injury may be related to the intensity of mechanical ventilation--expressed as mechanical power. In the present study, we investigated whether there is a safe threshold, below which lung damage is absent. Three groups of six healthy pigs (29.5 ± 2.5 kg) were ventilated prone for 48 h at mechanical power of 3, 7, or 12 J/min. Strain never exceeded 1.0. PEEP was set at 4 cmH2 O. Lung volumes were measured every 12 h; respiratory, hemodynamics, and gas exchange variables every 6. End-experiment histological findings were compared with a control group of eight pigs which did not undergo mechanical ventilation. Functional residual capacity decreased by 10.4% ± 10.6% and 8.1% ± 12.1% in the 7 J and 12 J groups (p = 0.017, p < 0.001) but not in the 3 J group (+1.7% ± 17.7%, p = 0.941). In 3 J group, lung elastance, PaO2 and PaCO2 were worse compared to 7 J and 12 J groups (all p < 0.001), due to lower ventilation-perfusion ratio (0.54 ± 0.13, 1.00 ± 0.25, 1.78 ± 0.36 respectively, p < 0.001). The lung weight was lower (p < 0.001) in the controls (6.56 ± 0.90 g/kg) compared to 3, 7, and 12 J groups (12.9 ± 3.0, 16.5 ± 2.9, and 15.0 ± 4.1 g/kg, respectively). The wet-to-dry ratio was 5.38 ± 0.26 in controls, 5.73 ± 0.52 in 3 J, 5.99 ± 0.38 in 7 J, and 6.13 ± 0.59 in 12 J group (p = 0.03). Vascular congestion was more extensive in the 7 J and 12 J compared to 3 J and control groups. Mechanical ventilation (with anesthesia/paralysis) increase lung weight, and worsen lung histology, regardless of the mechanical power. Ventilating at 3 J/min led to better anatomical variables than at 7 and 12 J/min but worsened the physiological values.

Keywords: mechanical power; mechanical ventilation; treshold; ventilation induced lung injury.

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Conflict of interest statement

LG reports to be consultant for General Electrics and SIDAM. He also receives lectures fees from Estor and Dimar. LS reports financial relationships with Medtronic, Ferrer Deutschland and Merck. Part of the salary support for the author M.B. was provided by an unrestricted research grant from Sartorius Inc. Göttingen, Germany. All other authors disclose no conflict of interest.

Figures

FIGURE 1
FIGURE 1
Time course of FRC changes (actual FRC – baseline FRC/baseline FRC) as a function of time in groups 3 J, 7 J, and 12 J. The baseline FRC were 421, 426, and 425 ml respectively, see also Table 2 (p value for time = 0.025, power group = 0.932, time and power group interaction = 0.222). The error bars represent the standard error of the mean
FIGURE 2
FIGURE 2
PaO2 (panel a) and PaCO2 (panel b) as a function of time in groups 3 J, 7 J, and 12 J. The FiO2 was maintained constant at 0.4 in all animals throughout the whole experiment (PaO2: p value for time = 0.251, power group: <0.001, time and power group interaction = 0.368; PaCO2: time = <0.001, power group = <0.001, time and power group interaction = <0.001). The error bars represent the standard error of the mean
FIGURE 3
FIGURE 3
Alveolar ventilation to perfusion ratio (VA/Q) as a function of time in groups 3 J, 7 J, and 12 J (p value for time = 0.737, power group = <0.001, time and power group interaction = 0.349). Eight out of 180 measurements missing. The error bars represent the standard error of the mean
FIGURE 4
FIGURE 4
End‐experimental lung weight/kg, lung wet‐to‐dry ratio, and gas/tissue ratio in the experimental groups. The gas/tissue ratio was not available in the control animals, as FRC was not measured (p values: lung weight/kg: group: <0.001; lung wet‐to‐dry ratio: group: 0.033; gas/tissue ratio: 0.097). The error bars represent the standard error of the mean
FIGURE 5
FIGURE 5
Arbitrary score of the histological alterations observed in the experimental groups (vascular congestion: p value for power group = 0.010; septal ruptures: p value for power group = 0.175; alveolar edema: p value for power group = 0.054; atelectasis: p value for power group = 0.187; intravascular thrombi: p value for power group = 0.459). The error bars represent the standard error of the mean
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