Differential lung ventilation for the respiratory care

Abstract

Conventional bilateral positive pressure ventilation (IPPV or CPPV) may not be applied to the unilateral lung disease and/or the case of remarkable difference in the compliance of both lungs. Since ventilation with equal airway pressure to both lungs will expand mainly the more compliant (better) lung, so the pulmonary blood flow will shift to the less compliant (worse) lung from the over-expanded lung. Accordingly, the V/Q mismatching will increase. And also the conventional ventilation is often not applicable to the patients with unilateral bulla or bronchopleural fistula.
Differential lung ventilation (DLV) using, as a rule, double lumen endbronchial tube and two ventilators may be effective in such conditions above mentioned. The main purpose of DLV is to correct the V/Q mismatching between left and right lungs.
The best way for DLV may be as follows.
1. Lateral positioning, better side down.
2. Equal V_T to each lungs.
3. Two electronically controlled ventilators are connected each other using a computer system, and one lung should be ventilated following the real-time informations about V_T, C_ST, or R_AW, etc. obtained (and computed) from the other lung.
As it is troublesome to use two ventilators of same type, it may be beneficial to apply high frequency ventilation (HFV) or continuous flow ventilation (CFV) to one lung and CPPV to the other. Our dog study of one lung pneumonitis by HCL infusion revealed that this method improved PaO₂ compared to the conventional bilateral ventilation.