Short Term Effect of Body Positions on Dynamic Lung Compliance in Mechanically Ventilated Patients with Lung Pathology- A randomised cross over study

Mechanical ventilators are used to prevent hypoxemia caused due to inadequate ventilation. It can also lead to retention of secretions and alveolar collapse due to improper ventilation of the dependent lung. Positioning has direct effect on optimizing the respiratory mechanics and improving the ventilation. This study was conducted to determine the effect of various body positions on dynamic compliance in such patients.

Randomized cross over study.

Total 19 subjects with various lung pathologies on mechanical ventilator, fulfilling the inclusion criteria were included. Each patient was positioned in the randomized sequence of four positions (supine, right lateral, left lateral and erect). Each position was maintained for 45 minutes. Dynamic compliance was measured at the interval of every 15 minutes by the formula dynamic compliance= delivered tidal volume/(peak inspiratory pressure-PEEP). Hemodynamic parameters, respiratory rate, SpO₂ were monitored in each position.

The highest values of the dynamic compliance in supine, right lateral, left lateral and erect position were 31.88 ml/cm H₂O after 45 minutes, 28.33ml/cmH₂O after 15 minutes, 25.22ml/cmH₂O at the beginning and 29.67 ml/cmH₂O after 45 minutes respectively. There was no significant difference in the dynamic compliance (p=0.229), heart rate, respiratory rate, SpO₂ in the four positions.

There was no significant difference in the dynamic compliance among all the positions. The results of the study cannot be generalized because of the small size. This provided the insight into the effect of body position.