The aim of postural drainage is to to allow gravity to assist drainage of respiratory secretions. There are 11 different positions which are based on the anatomy of the bronchial tree and are aimed at draining particular lobes or lung segments. Postural drainage may be used in conjunction with other techniques, e.g.the active cycle of breathing techniques, the forced expiration technique with or without percussion, positive expiratory pressure (PEP) and flutter.
The right lung is divided into three lobes (right upper lobe, right middle lobe and right lower lobe) while the left lung has only two lobes (left upper lobe and lower lobe). The figure below shows the individual segments which make up each lobe.

Click on picture to split lung into lobes. Right upper lobe Apical segment (1) Posterior segment (2) Anterior segment (3) Right middle lobe Lateral segment (4) Medial segment (5) Right lower lobe Superior segment (6) Anterior basal segment (7) lateral basal segment (8) posterior basal segment (9) medial basal segment (10)

Click on picture to split lung into lobes. Left upper lobe (superior division) Apico-posterior segment (11,12)
Anterior segment (13)
Left upper lobe (lingular division) Superior segment (14)
Inferior segment (15)

Left lower lobe
Superior segment (16)
Posterior basal segment (17)
Lateral basal segment (18)
Antero-medial basal segment (19)