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. 2017 Apr;13(4):1572-1577.
doi: 10.3892/etm.2017.4117. Epub 2017 Feb 10.

Application of dead space fraction to titrate optimal positive end-expiratory pressure in an ARDS swine model

Weishuai Bian  1 , Wei Chen  1 , Yangong Chao  2 , Lan Wang  3 , Liming Li  2 , Jian Guan  2 , Xuefeng Zang  1 , Jie Zhen  1 , Bo Sheng  1 , Xi Zhu  4
Affiliations

Application of dead space fraction to titrate optimal positive end-expiratory pressure in an ARDS swine model

Weishuai Bian et al. Exp Ther Med. 2017 Apr.

Abstract

This study aimed to apply the dead space fraction [ratio of dead space to tidal volume (VD/VT)] to titrate the optimal positive end-expiratory pressure (PEEP) in a swine model of acute respiratory distress syndrome (ARDS). Twelve swine models of ARDS were constructed. A lung recruitment maneuver was then conducted and the PEEP was set at 20 cm H2O. The PEEP was reduced by 2 cm H2O every 10 min until 0 cm H2O was reached, and VD/VT was measured after each decrement step. VD/VT was measured using single-breath analysis of CO2, and calculated from arterial CO2 partial pressure (PaCO2) and mixed expired CO2 (PeCO2) using the following formula: VD/VT = (PaCO2 - PeCO2)/PaCO2. The optimal PEEP was identified by the lowest VD/VT method. Respiration and hemodynamic parameters were recorded during the periods of pre-injury and injury, and at 4 and 2 cm H2O below and above the optimal PEEP (Po). The optimal PEEP in this study was found to be 13.25±1.36 cm H2O. During the Po period, VD/VT decreased to a lower value (0.44±0.08) compared with that during the injury period (0.68±0.10) (P<0.05), while the intrapulmonary shunt fraction reached its lowest value. In addition, a significant change of dynamic tidal respiratory compliance and oxygenation index was induced by PEEP titration. These results indicate that minimal VD/VT can be used for PEEP titration in ARDS.

Keywords: acute respiratory distress syndrome; dead space fraction; positive end-expiratory pressure; recruitment maneuver.

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Figures

Figure 1.
Figure 1.
VD/VT of the acute respiratory distress syndrome swine model under different conditions. *P<0.05 vs. pre-injury; †P<0.05 vs. injury. VD/VT, ratio of dead space volume to tidal volume (dead space fraction); PEEP, positive end-expiratory pressure; Po, optimal PEEP; -n, n cm Hg below Po; +n; n cm Hg above Po.
Figure 2.
Figure 2.
P/F ratio of the acute respiratory distress syndrome swine model under different conditions. *P<0.05 vs. pre-injury; †P<0.05 vs. injury. P/F, alveolar partial pressure of oxygen/fraction of inspiration oxygen (oxygenation index); PEEP, positive end-expiratory pressure; Po, optimal PEEP; -n, n cm Hg below Po; +n; n cm Hg above Po.
Figure 3.
Figure 3.
Cdyn of the acute respiratory distress syndrome swine model under different conditions. *P<0.05 vs. pre-injury; †P<0.05 vs. injury. Cdyn, dynamic tidal respiratory compliance; PEEP, positive end-expiratory pressure; Po, optimal PEEP; -n, n cm Hg below Po; +n; n cm Hg above Po.
Figure 4.
Figure 4.
Qs/Qt of the acute respiratory distress syndrome swine model under different conditions. *P<0.05 vs. pre-injury; †P<0.05 vs. injury. Qs/Qt, intrapulmonary shunt ratio; PEEP, positive end-expiratory pressure; Po, optimal PEEP; -n, n cm Hg below Po; +n; n cm Hg above Po.
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