Effect of recumbent position on lung volume and oxygenation during Acute Respiratory Distress Syndrome.
J Dellamonica, N Lerolle, C Sargentini, S Hubert, G Beduneau, F Di Marco, A Mercat, JC M Richard, JL Diehl, G Bernardin, L Brochard
Electronic supplemental Material
Additional Method:
Lung volume measurement suing the Multribreath nitrogen wash-in wash-out:
The technique has been described elsewhere [16, 20]. In summary, continuous measurement of end-tidal O2 and CO2 during a 10% variation of FiO2 allows measurement of nitrogen washout and washin and then the calculation of the aerated lung volume. Average of both washout and washin data is performed automatically if the variation between the two is less than 20% (as determined by manufacturer). FRC implies that it is measured without PEEP (atmospheric pressure), and we thus used the term End Expiratory Lung Volume (EELV) for this measurement. The mean of three EELV measured at each position was considered [15]. EELV was expressed as normalized to the predicted body weight using the formula for men: 50 + 0.91 × (height [cm] – 152.4), and for women: 45.5 + 0.91 × (height [cm] – 152.4). Theoretical FRC seated and supine have been calculated using the Ibanez and Raurich formula [21].
Additional discussion:
Hemodynamic
Mean arterial pressure increased during verticalization without heart rate modification (table E1). All patients studied had an arterial line for blood pressure continuous monitoring and arterial blood gas samples. Main hypothesis for these MAP variations is the miss-position of the pressure captor without re-calibration in sitting position.
Table E1: Hemodynamic and pulmonary data during the four epochs studied.
Supine 1 / Semi-recumbent / Seated / Supine 2MAP (mmHg) / 71 [66; 80] / 80 [71; 88] * / 84 [75; 93] * / 75 [65; 81]
Heart rate (bpm) / 94 [78; 105] / 91 [80; 109] / 90 [78; 109] / 88[77; 100]
Strain / 0.38 [0.27; 0.45] / 0.33 [0.24; 0.39]* / 0.31 [0.24; 0.40]* / 0.33 [0.24; 0.46]
EELV/PBW (mL/kg) / 16 [13; 22] / 18 [15; 25] * / 19 [15; 25] * / 18 [13; 25]*
PaO2 (mmHg) / 84 [78; 104] / 97 [80; 110] * / 102 [87; 110] * / 90 [72; 114]
FiO2 (%) / 60 [50; 80]
PaO2/FiO2 / 131 [116; 180] / 159 [126; 199] * / 160 [122; 210] * / 143 [115; 194]
PaCO2 (mmHg) / 39.0 [35.5; 47.0] / 39.5 [35.0; 48.0] / 40.0 [34.7; 48.2] / 40.0 [35.5; 47.5]
SaO2 (%) / 96.5 [96.0; 97.0] / 97.0 [96.0; 98.0] * / 98.0 [96.7; 98.0] * / 97.0 [94.2; 98.0]
Cstat (mL/cmH2O) / 36 [27; 45] / 32 [25; 40] * / 31 [24; 38] * / 35 [29; 40]
* p<0.01 vs supine 1 was considered significant using Bonferoni correction if Friedman’s test was p<0.05.
All patients had stable FiO2 during the study
Figure E1:
PaO2/FiO2 at the four epochs studied.
Panel A represents the whole population.
Panel B Blue boxes represent moderate & severe ARDS defined as PaO2/FiO2<200, red boxes are milder patients.
Friedman’s non parametric test showed p<0.05 for All patients and Moderate and severe ARDS allowing Wilcoxon paired test: * p<0.001 vs supine 1 (Bonferoni correction)
Panel A
Panel B