The effect of lateral positioning on gas exchange and respiratory mechanics in mechanically ventilated patients with unilateral lung disease

Objective

To study the influence of lateral positioning with the involved side upwards, on gas exchange and respiratory mechanics in intubated patients with unilateral lung disease.

Materials and methods

Mechanically ventilated patients with unilateral lung disease. Of the 15 patients studied, seven had pneumonia and eight atelectasis with no response to routine physicotherapy. All patients were sedated and paralyzed for the study. All patients were ventilated in the A/C mode.

We performed measurements of gas exchange and respiratory system compliance and resistance (interrupter technique) with the patient supine. Immediately afterwards the patient was placed at lateral decubitus position with the involved side upwards. After 10 min at the new position, measurements were repeated. We searched for differences with positioning for the parameters measured. We also tried to correlate changes in oxygenation with a score expressing the radiographic extend of lung disease on the basis of portable anterolateral X-rays. Statistical analysis was performed with t-test and Pearson correlation. All measurements are expressed as mean ± SEM.

Results

With lateral positioning there was a statistically significant increase in PaO₂/FiO₂ (from 132.5 ± 19.4 to 162.5 ± 18.9 mmHg, P < 0.000) and PaCO₂ (from 41.7 ± 2.6 to 43.7 ± 2.5 mmHg, P < 0.01). At the same time a significant decrease in compliance (from 44.9 ± 3.1 to 39.4 ± 2.9 l/cmH₂O, P < 0.000) and an increase in resistance (from 0.223 ± 0.02 to 0.255 ± 0.02 cmH₂O l ^-1 s, P < 0.000), were observed. PaO₂/FiO₂ was significantly (P < 0.01) correlated with the radiographic score (r = 0.76).

Conclusion

Placement in lateral decubitus positioning with the involved side upwards, results in immediate improvement of oxygenation in the majority of cases of unilateral lung disease. This improvement is correlated with the radiographic extend of disease. At the same time a statistically significant deterioration in respiratory mechanics is observed.