Restrictive pulmonary disease

Question 1

Definition

Answer 1

• Restrictive lung disease is characterized by a reduced lung volume, due to disease of either the lung parenchyma or the pleura, chest wall, or neuromuscular apparatus. there is a reduction in total lung capacity (tLC), VC, and restingVt .

Question 2

Diffuse parenchymal lung disease

Def and course

Answer 2

• Adiverse group of disorders (often referred to as interstitial lung disease) that are classified together because of similar clinical, radiographic, physiological, or pathological manifestations.
• Results in decreased lung compliance and impaired gas exchange.
• An initial inflammatory reaction in the alveoli impairs gas exchange. this is followed by collagen deposition and fibrosis, resulting in lungs that are smaller in volume and less compliant to inflation.
• Diffuse parenchymal lung diseases are divided into those that are associated with known causes and those that are idiopathic.

Question 3

Diffuse parenchymal lung disease

Causes

Answer 3

• the commonest identifiable causes include exposure to occupational and environmental agents, especially to inorganic or organic dusts, drug-induced pulmonary toxicity (e.g. amiodarone, chemotherapy agents, and paraquat poisoning), and radiation-induced lung injury. Diffuse parenchymal lung disease can also complicate the course of most connective tissue disorders (e.g. dermatomyositis, rheumatoid arthritis (RA), SLE, and scleroderma).
• Idiopathic causes include sarcoidosis, cryptogenic organizing pneumonia, and the idiopathic interstitial pneumonias.
• Avariety of infections can cause interstitial opacities on CXR, including fungal pneumonias, atypical bacterial and viral pneumonias. these infections often occur in immunocompromisedhosts.

Question 4

Diffuse parenchymal lung disease

Treatment

Answer 4

• treatment is usually with oral steroids, but other immunosuppressive therapy may be used, and young patients may be considered for lung transplantation if severely affected.

Question 5

Extrinsic conditions ofthe chestwall

Answer 5

• the components of the chest wall include the bony structures (ribs, spine), respiratory muscles, and nerves connecting the central nervous system (CnS) with the respiratory muscles
• Disease that alters the structure of the chest wall will affect the mechanics of ventilation and may result in respiratory compromise or failure.

Question 6

Extrinsic conditions ofthe chestwall

Examples

Answer 6

• Examples of conditions that affect the chest wall include ankylosing spondylitis, congenital deformities (such as pectus excavatum, flail chest, kyphoscoliosis), thoracoplasty, abdominal processes (such as morbid obesity and ascites), and chest wall tumours.

Question 7

General considerations

Answer 7

• the work of respiration is optimized by rapid shallow breaths and is easier in the sitting position.
• Many patients are stable and only slowly deteriorate over some years. these patients may tolerate surgery relativelywell.

Question 8

Preoperative assessment

Answer 8

• Should focus on determining the degree of respiratory impairment and the underlying disease process to establish the extent of involvement of other organs.
• Ahistory of exertional dyspnoea (or at rest) should be evaluated further with ABgs andPFts.
• Discuss seriously affected patients with a respiratory physician.

Question 9

Investigations

Answer 9

• ABgs—often remain normal until late. Reduced PaO2 reflects significant disease, and CO2 retention is a late sign, implying impending ventilatory failure.
• Obtain PFts, including spirometry, lung volumes (all are reduced), and gas transfer, if these have not been done within the previous 6–8wk. AVC of <15mL/kg is indicative of severe dysfunction.
• CXR changes will be according to the underlying condition

Question 10

Conduct ofanaesthesia

Answer 10

• As for other pathologies, consider regional techniques, and minimize positive pressure ventilation and airway instrumentation as far as possible. Spinal disease may preclude subarachnoid or epidural blocks.
• Where IPPV is necessary, minimize peak airway pressure using pressure-controlled ventilation with high rate and lowVt .
• Check the need for additional steroid cover at induction for those patients on regular steroid therapy (see E p. 165).
• Maintain a high index of suspicion for pneumothorax.

Question 11

Post-operativecare

Answer 11

• Consider post-operative ICU/HDU admission following major surgery. May be suitable for elective training in CPAP/non-invasive positive pressure ventilation (nIPPV) techniques preoperatively.
• Extubate in a sitting position.
• give supplemental O2, and maintain SpO2 >92%.
• good physiotherapy and analgesia are vital to achieve sputum clearance. With severe disease, minor respiratory complications may precipitate respiratory failure.
• Mobilizeearly.
• treat respiratory infection vigorously.

• Ensure steroid cover continues in appropriate formulation.