In particular, through multiple inert-gas elimination technique, it was demonstrated that the aforementioned improvement in oxygenation was due to either reduction in intrapulmonary shunt or improvement in ventilation-perfusion mismatch (V A/Q) 9. Further corroboration of these findings are largely available 9, 10, 11, 12, 13, 14.
In those who presented mono-lateral disease, significant increase in arterial partial pressure of oxygen (PaO 2) was demonstrated, while lying on the healthy side. In the seminal study by Zack and colleagues 8 the role of body position on arterial blood gas was appraised in patients with or without mono-lateral lung diseases. Concurrently, recruitment of the non-dependent infected lung is desirable, and redistribution of ventilation has been observed 4, 5, 6, 7. In the most severe cases, clinicians often place the patient onto lateral decubitus, with the healthy lung dependent, to improve ventilation-perfusion coupling and oxygenation 3. Severe mono-lateral pneumonia is one of the most challenging situations, since invasive mechanical ventilation (MV) is often needed to maintain adequate gas exchange, while substantial imbalance in pulmonary mechanics ensues between the healthy highly compliant lung and the stiff diseased lung. In the vast majority of cases, pneumonia commonly affects a single lobe, but the infection could broaden to an entire lung or ultimately lead to acute respiratory distress syndrome (ARDS) 2. Pneumonia is one of the most frequent causes of intensive-care unit (ICU) admission and mortality 1. Our data raise potential clinical concerns for the use of lateral position in mono-lateral pneumonia. Right-lateral orientation further collapsed the diseased lung. In an animal model of right-lung pneumonia, left-lateral decubitus improved oxygenation, but collapsed the healthy lung. PaO 2/FiO 2 improved in the left-lateral position ( p = 0.005). LUS of the left non-infected lung worsened while positioned in left-lateral position (from 1.33 ± 1.73 at baseline to 6.78 ± 4.49 p = 0.005). Primary outcome was lung ultrasound score (LUS) of the dependent lung after 3-h lateral positioning. After 3 h of lateral positioning, the animals were placed supine another recruitment manoeuvre was performed, and the effects of contralateral decubitus were assessed. After 24 h, lungs were recruited and the animals were randomly positioned on right or left side. Mono-lateral right-sided pneumonia was induced with intrabronchial challenge of Pseudomonas aeruginosa. Nine pigs (32.2 ± 1.2 kg) were sedated and mechanically ventilated. Oxygenation response to this manoeuvre is heterogeneous and derecruitment of dependent lung has not been elucidated.
Patients with mono-lateral pneumonia and severe respiratory failure can be positioned in lateral decubitus, with the healthy lung dependent, to improve ventilation-perfusion coupling.
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