Pleural effusion
Empyema: Empyema is pus in the pleural space. It is commonly caused by Pneumococci, S.milleri, S.aureus, and anaerobic bacteria. It may result from direct spread of lung infections, liver abscess, hematogenous seeding, or penetrating injuries to the chest. Long-standing empyema may heal with fibrosis and calcification, which can cause breathing difficulties.
It presents with fever, chest pain, cough with expectoration, malaise, poor appetite, weight loss, etc. CxR shows radio-opaque shadows with blunting of the costophrenic angles. Ultrasound and CT will also show loculated lesions and septations. The “split pleura sign” is seen on CT scan due to separation of the visceral from the parietal pleura by pus. Apart from antibiotics, chest tube drainage is needed for cure.
Chylothorax: This is the accumulation of chyle in the pleural cavity. Causes include trauma to the thoracic duct from thoracic surgery, cirrhosis, venous thrombosis in the neck veins, or mediastinal lymphadenopathy causing obstruction to chyle drainage. Infectious causes include tuberculosis, filariasis, and histoplasmosis. Genetic defects such as Down’s and Noonan’s syndrome, or developmental anomalies of lymphatics, can also cause chylothorax.
It presents with dyspnea, cough, and chest discomfort. Rapid accumulation of large quantities of chyle may cause hypotension. Chronic cases can lead to nutritional imbalances such as weight loss, muscle wasting, immunodeficiency, metabolic acidosis, hyponatremia, and hypocalcemia.
On examination, pleural fluid in chylothorax is typically milky white. Chylomicrons are present, pleural fluid triglycerides are > 110 mg/dl, and the pleural fluid/serum cholesterol ratio is <1. Chylomicrons can be detected quantitatively or stained with Sudan III.
Pulmonary hypertension (PAH): This is defined as systolic blood pressure in the pulmonary artery greater than 30 mmHg. PAH is more common in females aged 30-60 years. It may be idiopathic or secondary.
Increased resistance in pulmonary vessels occurs due to proliferation of pulmonary endothelial and smooth vessel cells, pulmonary vasoconstriction, chronic inflammation, and increased local thromboxane and endothelin-1. Platelet dysfunction, decreased activity of tissue plasminogen activator, and a pro-thrombotic tendency are also seen.
Familial cases are associated with defects in the BMPR2 gene (AD), ALK 1, ENG, SMAD9, CAV1, and KCNK3. Appetite suppressants like fenfluramine and dexfenfluramine, methamphetamines, and dasatinib are known to cause PAH. Estrogen is associated with a higher risk of PAH.
Secondary causes of PAH include HIV/AIDS, scleroderma, cirrhosis, congenital heart disease, Pickwickian disease, pneumoconiosis, COPD, sickle cell disease, recurrent pulmonary emboli, chronic left ventricular failure, and living at high altitude.
Pulmonary arteries and arterioles show medial hypertrophy, thickening of elastic laminae, and concentric intimal thickening. PAH is a diagnosis of exclusion.
It presents with nonspecific symptoms such as dyspnea (especially on exertion), fatigue, chest pain, fainting, cough, and cyanosis. Symptoms of right heart failure are seen in advanced cases.
Physical examination shows loud P2, right parasternal lift, pansystolic murmur from TR, diastolic murmur from PR, S3, edema, raised JVP, hepatomegaly, and ascites. ECG may show right ventricular hypertrophy and right axis deviation. CxR may show RVH and a prominent pulmonary artery shadow. Echo may show right heart hypertrophy and valvular regurgitation. Confirmation is done by right heart catheterization, which shows increased pressure in the pulmonary artery.
Treatment is with prostacyclin or epoprostenol, bosentan (endothelin receptor antagonist), and PDE5 inhibitors sildenafil and tadalafil. Rarely, patients may benefit from calcium channel blockers like nifedipine and diltiazem. Lung transplantation may be required.
Barotrauma: This is damage to the lungs caused by pressure changes. Barotrauma due to mechanical ventilation is called ventilator associated lung injury (VALI) or ventilator induced lung injury.
Clinical manifestations of barotrauma include pneumothorax, pulmonary interstitial emphysema, subcutaneous emphysema, pneumoperitoneum, pneumomediastinum or pneumopericardium, air embolisation, and tension cysts. Positive pressure ventilation and high volume ventilation carry a high risk of barotrauma. Hyperinflated alveoli rupture, leaking air into surrounding tissues. End-inspiratory volume and intrinsic PEEP are good predictors of barotrauma risk.
Symptoms can range from mild hypoxemia, hypotension, and tachycardia to severe signs such as profound hypoxemia, cardiovascular collapse, and low cardiac output. Subcutaneous emphysema presents with crepitus. CxR may show air in the surrounding chest tissues, perivascular air halos, linear streaks of air radiating toward the hilum, pneumatoceles, and large subpleural air collections.
Keeping the end-inspiratory plateau pressure <30 cmH2O, tidal volume 6-8 ml/kg, and carefully titrating PEEP can help protect against barotrauma.
Barotrauma is also seen in diving and breathing compressed air. Decompression sickness (Caisson disease) occurs during rapid ascent from a dive, leading to formation of nitrogen bubbles that block local and systemic circulation and cause DIC. Symptoms include headache, malaise, dyspnea, joint pains (bends), paresthesias, paresis, incontinence, dizziness, seizures, coma, etc. Some cases present with osteonecrosis a few weeks later. Treatment is with 100% oxygen and recompression therapy.
Foreign body aspiration: This is most common in young children < 4 year old. Peanuts, marbles, popcorn, coins, and button batteries are the most commonly aspirated objects in children, while fish and meat pieces are most common in adults. Foreign bodies typically get lodged in the larynx, trachea, glottis, or bronchi.
It presents with sudden onset of choking, coughing, dyspnea, stridor, and wheezing. Some cases may be asymptomatic. CxR may show the foreign body if radiopaque, as well as atelectasis, pneumothorax, or pneumonia in older cases. Lateral decubitus films are more sensitive. CT, MRI, and endoscopy can be done on a case-to-case basis. Rigid bronchoscopy can be used to remove the obstructing object.
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