Pulmonary Emphysema
Pulmonary emphysema is a distention of the lung caused by one distention of the alveoli with rupture of the alveolar wall, with or without the escape of air into the interstitial space.
Etiology
- Chronic obstructive pulmonary disease (COPD) in horses is the most important cause of pulmonary emphysema.
- Mouldy hay is linked to COPD in orses.
- In cattle, acute interstitial pneumonia, lung worm infestation (dictyocaulus viviparus), traumatic pneumonitis due to foreign body, and poisonous plants like Senecio quadridentatus and Perilla frufenses are attributing factors for emphysema.
Pathogenesis
Excessive dilation of alveoli due to narrowing of airways leads to its rupture and escape of air into interstitial space, which is the most accepted hypothesis of pulmonary emphysema.
Another possible reason could be the inherent weakness of the alveolar wall and supporting tissue, which are unable to sustain the stress during forceful coughing or exertion. Incomplete evacuation and imperfect oxygenation of the blood are the net results of pulmonary emphysema, leading to hypoxia.
Clinical Findings
An increased rate of respiration at rest is the initial sign of pulmonary emphysema. As the disease advances, expiratory dyspnea is evident, which gets more pronounced during exercise. It is accompanied by an expiratory grunt. On auscultation, the presence of paper crackling and lung parenchyma is a sure indication of pulmonary emphysema. Subcutaneous emphysema of the wither is considered a sequel of emphysema.
Diagnosis
- Diagnosis can be done based on the clinical findings of the paper crackling rales on auscultation.
- Narrowing of the bronchioles and the presence of abundant exudates in the airways during endoscopic examination.
- High absolute neutrophil count in BALF.
Treatment
Identification of the primary lesion and its treatment are of paramount importance. Reduction of inflammation of the airways with NSAIDs, beta-adrenergic bronchodilators like clenbuterol at 0.8–3.2 mg/kg body weight, and steroids are indicated, but prognosis is always guarded.
Inhalant corticosteroid in the form of spray (intranasal spray) have been found effective in controlling the signs of respiratory distress. Sodium cromoglycate is also useful in the treatment of COPD in horses as it prevents the degranulation of mast cells.