EIT and mechanics
Materials and methods
Statistical analysis
Quantitative variable are expressed as mean±sd. In order to overule pseudoreplication due to repeated measurement to the same animal, mixed effect regression models were use built with nlme package. In these cases, each animal was included as a random variable. Model conditional coefficients of determination for mixed-effect models were calculated using MuMIn package. A similar approach was used when fitting analysis of variance models.
Statistical analysis was performed with R version 3.3.3 (2017-03-06).
Results
Baseline respiratory parameters were as follows: Vt=295±83.95 ml, PaFiO2=125.68±70.16 mmHg, pH=7.2±0.06, PaCO2=62.09±13.63 mmHg, inspiratory static PAW=31.43±4.15 cmH2O and compliance=14.51±5.48 ml/cmH2O.
Measurements by PEEP
Table 1: TIE data by PEEP
| 0 | 5 | 10 | 15 | 20 | 25 | 30 | P | |
|---|---|---|---|---|---|---|---|---|
| Silent Spaces Non-Dependent [%] | 2.26±2.05 | 2.45±1.99 | 5.98±2.98 | 7.25±3.19 | 7.56±3.35 | 7.22±2.67 | 6.57±2.85 | 3.8e-08 |
| Silent Spaces Dependent [%] | 9.98±7.91 | 8.51±6.37 | 5.05±4.4 | 1.01±1.55 | 0.48±0.9 | 0.61±1.14 | 0.91±1.52 | 3.7e-07 |
| Stretch quartile - | 0.19±0.05 | 0.19±0.06 | 0.21±0.07 | 0.26±0.05 | 0.27±0.05 | 0.27±0.03 | 0.29±0.05 | 6.1e-09 |
| Stretch median | 0.34±0.06 | 0.34±0.06 | 0.38±0.07 | 0.44±0.08 | 0.51±0.05 | 0.52±0.05 | 0.53±0.06 | 6.3e-13 |
| Stretch quartile + | 0.55±0.06 | 0.55±0.06 | 0.59±0.06 | 0.63±0.06 | 0.7±0.04 | 0.72±0.04 | 0.74±0.05 | 4.7e-10 |
Table 2: Mechanics by PEEP
| 0 | 5 | 10 | 15 | 20 | 25 | 30 | P | |
|---|---|---|---|---|---|---|---|---|
| Ptp-inspElas | 29.63±5.73 | 28.93±5.57 | 28.2±4.75 | 29.03±4.74 | 32.28±5.74 | 36.53±5.36 | 45.76±5.77 | 1e-08 |
| Pplat | 33.32±5.94 | 34.02±5.58 | 33.62±4.32 | 35.49±5.07 | 40.46±4.68 | 48.1±7.19 | 57.59±8.31 | <2e-16 |
| CStatic | 9.97±2.9 | 10.74±3.55 | 13.42±4.03 | 15.82±5.01 | 15.75±5.25 | 14.67±6.25 | 12.16±6.75 | 2.7e-09 |
| Cdyn | 6.44±1.47 | 6.98±1.62 | 9.14±1.95 | 10.74±2.76 | 10.53±2.91 | 10.01±3.04 | 8.98±3.66 | 8.7e-13 |
| StressIndex | 1.05±0.13 | 1.08±0.09 | 1.04±0.06 | 1.05±0.08 | 1.05±0.1 | 1.09±0.08 | 1.06±0.05 | 0.95 |
| Ptp-insp | 19.33±4.31 | 19.87±4.38 | 17.9±3.88 | 19.2±3.13 | 21.76±4.48 | 25.66±5.54 | 33.31±4.5 | 1.1e-10 |
| Ptp-esp | -8.11±7.03 | -3.82±6.5 | -1.06±5.91 | 3.18±4.95 | 6.23±5.27 | 9.29±5.24 | 12.54±5.79 | <2e-16 |
| Ep/Etot | 0.85±0.05 | 0.82±0.04 | 0.82±0.06 | 0.8±0.05 | 0.79±0.11 | 0.77±0.1 | 0.8±0.09 | 0.33 |
| Ptp-inspElas | 29.63±5.73 | 28.93±5.57 | 28.2±4.75 | 29.03±4.74 | 32.28±5.74 | 36.53±5.36 | 45.76±5.77 | 1e-08 |
Table 3: VD/VT data by PEEP
| 0 | 5 | 10 | 15 | 20 | 25 | 30 | P | |
|---|---|---|---|---|---|---|---|---|
| VCO2br | 4.32±2.13 | 5.07±3.11 | 5.37±2.89 | 5.71±2.95 | 5.02±2.74 | 4.59±2.5 | 4.18±2.7 | 5.3e-05 |
| Bohr | 0.51±0.08 | 0.52±0.09 | 0.53±0.06 | 0.55±0.05 | 0.61±0.07 | 0.65±0.08 | 0.69±0.1 | <2e-16 |
| VTalV | 202.79±64.6 | 192.65±67.85 | 190.31±61.41 | 183.44±53.01 | 167.5±58.1 | 158.08±56.54 | 142.77±63.18 | 2.7e-14 |
| VdalV/VTalV | 0.27±0.05 | 0.26±0.05 | 0.25±0.02 | 0.27±0.03 | 0.3±0.03 | 0.33±0.03 | 0.35±0.06 | 6.7e-10 |
Table 4: Gas exchange data by PEEP
| 0 | 5 | 10 | 15 | 20 | 25 | 30 | P | |
|---|---|---|---|---|---|---|---|---|
| PH | 7.16±0.06 | 7.16±0.08 | 7.2±0.06 | 7.21±0.07 | 7.2±0.08 | 7.23±0.09 | 7.2±0.06 | 0.00011 |
| PaCO2 | 72.59±15.88 | 70.55±12.32 | 64.7±13.91 | 60.74±10.74 | 60.62±12.77 | 57.55±15.7 | 59.37±14.34 | 4.1e-07 |
| Pa/FiO2 | 50.95±22.01 | 54.74±19.54 | 105.72±58.81 | 215.75±124.33 | 332.49±169.2 | 548.55±140.55 | 571.19±56.03 | <2e-16 |
Table 5: Hemodynamics by PEEP
| 0 | 5 | 10 | 15 | 20 | 25 | 30 | P | |
|---|---|---|---|---|---|---|---|---|
| TAS | 123.55±31.71 | 126.27±28.92 | 124.73±18.43 | 125±16.73 | 114.55±14.31 | 104.18±20.4 | 100.3±16.71 | 0.0035 |
| TAM | 94±30.1 | 96.45±29.04 | 94.82±17.57 | 94.27±18.3 | 90.73±14.17 | 81.09±17.41 | 78.9±14.25 | 0.058 |
| IC | 4.84±1.1 | 3.68±1.13 | 4.22±0.32 | 3.58±0.9 | 3.42±1.28 | 3.76±1.5 | 2.98±1.1 | 0.11 |
| VVS | 6.5±2.56 | 6.5±1.77 | 7.25±1.49 | 9.62±3.89 | 15.38±6.16 | 19±9.77 | 29.57±14.36 | 5.3e-09 |
PTP and PAW
As expected, PTP shows a linear relationship with PAW (conditional mixed model R2 =0.98, P= \(2.693\times 10^{-47}\))
VD/VT and PEEP
VD/VT and PTP
Silent spaces and PEEP
Silent spaces and PTP
Comparison among physiological data according to different optimized parameters
Optimized parameter where defined as follows:
- VdalV/VTalV: lowest value
- VCO2br: greatest value
- Ptp-esp: nearest to 0 cmH2O
- CStatic: greatest value
- Pplat: nearest to 30 cmH2O
- Ptp-inspElas (elastance derived inspiratory PTP): nearest to 27 cmH2O
Table 7 shows physiological values recorded with each optimized parameter in the rows.
Table 7: Physiological data depending on optimized parameters
| VdalV/VTalV | VCO2br | Ptp-esp | CStatic | Pplat | Ptp-inspElas | P | |
|---|---|---|---|---|---|---|---|
| PEEPtot | 8.17±5.07 | 11.48±6.84 | 11.06±6.22 | 19.1±6.33 | 8.06±5.88 | 10.64±8.16 | 0.002024 |
| Pplat | 33.22±4.53 | 35.32±7.19 | 36.47±7.6 | 37.24±5.35 | 32.91±3.98 | 34.99±7.1 | 0.073583 |
| VdalV/VTalV | 0.23±0.03 | 0.25±0.04 | 0.26±0.04 | 0.29±0.03 | 0.26±0.03 | 0.28±0.02 | 4.8528e-05 |
| VCO2br | 5.44±3.02 | 6.07±2.88 | 5.86±3.25 | 5.33±2.36 | 4.97±2.14 | 4.85±2.4 | 0.0065323 |
| Ptp-esp | -1.81±6.11 | 0.6±6.99 | -0.26±1.58 | 5.69±8.17 | -2.54±6.91 | -1.95±5.82 | 0.032026 |
| Ptp-inspElas | 28.2±4.76 | 29.74±6.14 | 30.16±7.41 | 29.33±5.94 | 27.69±4.37 | 27.12±2.4 | 0.5356 |
| CStatic | 12.73±5.76 | 13.59±6.02 | 13.05±4.63 | 17.1±5.87 | 12.3±3.36 | 13.05±3.15 | 0.0027749 |
| Silent Spaces Dependent [%] | 8.28±6.71 | 4.49±5.35 | 7.36±8.8 | 1.25±1.41 | 6.84±7.49 | 5.74±6.53 | 0.062608 |
Multiple comparisons plots
Only those with significant ANOVA P above are displayed
## $PEEPtot
##
## $VCO2br
##
## $`Ptp-esp`
##
## $CStatic