Increasing Lung Volume

Atelectasis is collapse of anything from alveoli to the whole lung. Causes include:

• Shallow breathing
• Bronchial obstruction
• Absorption of trapped gas
• Surfactant depletion
• Compression from abdominal distension or pleural disorder

Physiotherapy is indicated to treat or prevent atelectasis if it is caused or anticipated by immobility, poor positioning, mucous plug, shallow breathing, shallow breathing or postoperative pain, especially in non-alert patients.

Consolidation causes loss of functioning lung volume. It is not directly responsive to physiotherapy but in a dehydrated patient it is responsive to hydration, and further complications may be prevented by positioning or mobilisation.

Pleural effusion, pneumothorax and abdominal distension compress the lung but are inaccessible directly to physiotherapy. Positioning may assist comfort and gas exchange, and sometimes re-expansion of the lung may need assistance, e.g. after a pleural effusion has been drained.

Restrictive disorders of the lung or chest wall reduce lung volume but are less responsive to physical treatment.

When increasing lung volume, the distribution of the extra air should be directed to poorly ventilated lung regions. In postoperative or immobilise patients this is usually the lower lobs. Loss of lung volume is a problem when it causes a significant degree of:

• Reduced surface area for gas exchange
• Reduced lung compliance
• Increased WOB

Controlled Mobilisation

The most fruitful technique for increasing lung volume is exercise (Dean, 1994). When accurately targeted, this combines upright posture (which reduces pressure on the diaphragm and encourages basal distribution of air) with natural deep breathing. The level of activity is controlled so that the patient becomes just slightly breathless but avoids muscle tension, then the patient is asked to stand against a wall to regain their breath, whilst being discouraged from talking, to minimise postural activity of the abdominal muscles, allowing the diaphragm to descend more freely encouraging deep therapeutic breathing rather than apical shallow breathing. For patients who have not just had surgery, some find that holding their hands behind their backs while leaning against a wall further frees their breathing.

Patients who cannot walk can mobilise by moving from bed to chair, and then regain their breath in the chair. With bed-bound patients, rolling is sufficient with the patient relaxing in the appropriate position to return to normal tidal breathing.

For the first 24 hours after surgery, watch the patient’s face for colour change that may be indicative of postural hypotension caused by preoperative fluid restriction and perioperative fluid shifts.

Positioning

Positioning affects several aspects of lung function:

• Lung volume is related to displacement of the diaphragm and abdominal contents. FRC decreases from standing to slumped sitting (high sitting but having slid down the bed). Macnaughton (1995) found that FRC can drop by up to 1 litre from standing to supine.
• Lung compliance decreases and WOB increases progressively from standing to sitting to supine. In supine, lung volume is restricted by the load of viscera, increased thoracic blood volume and small airway closure. Wahba (1991) found that WOB was 40% higher in supine that in sitting.
• Arterial oxygenation is usually higher in side-lying than supine. With bilateral or diffuse pathology, this tends to be slightly greater lying on the right than the left because of reduced compression on the heart.

Supine is unhelpful for lung volume because the diaphragm is inefficient and less co-ordinated with chest wall mechanics (Wahba, 1991). The slumped position is unhelpful because of pressure against the diaphragm. Time should be spent in side-lying so that the diaphragm is free from abdominal pressure. High sitting in bed rapidly becomes the slumped position for most patients as they slide down the bed. Time in high sitting should be limited for patients with loss of lung volume, unless necessary for a specific medical reason or to minimise pain.