When air or fluid enters the pleural space, drainage may be necessary based on the clinical condition of the patient.
Pneumothorax occurs when air enters into the pleural cavity. When a pneumothorax occurs unprovoked in a person without any underlying pathology, this is labeled primary spontaneous pneumothorax (PSP). Patients with a PSP can be managed in a number of ways based on their clinical picture and the size of the pneumothorax. To measure the size of a pneumothorax, computed tomography (CT) of the chest gives the most accurate 3-dimensional volume. CT is not always necessary, however, plain upright chest radiographs or bedside ultrasound are generally adequate for clinical decisions. The two most utilized methods of determining the size of a pneumothorax are by the American College of Chest Physicians (ACCP) and the British Thoracic Society (BTS). ACCP guidelines recommend measuring the distance from the outer edge of the pleural space to the most apical portion of the collapsed lung.3 Using this measurement, ≤ 3cm is considered small. BTS recommends measuring at the level of the hilum from the outer edge of the pleural space to the collapsed lung.4 According to BTS guidelines, a measurement < 2 cm is considered small.
For clinically stable patents with small pneumothoraces, recommended care includes observation for 3 to 6 hours followed by a repeat chest radiograph. If the repeat radiograph does not show progression of the pneumothorax, the patient can be safely discharged home and should return for a follow-up chest radiograph in 24 hours.3,4,5,6 Uncomplicated pneumothoraces will reabsorb at a rate of 2% of the volume of the hemithorax every 24 hours.7 For patients with a large PSP or patients experiencing significant symptoms, needle aspiration or SBCT are the recommended treatments. In a study of 60 patients, needle aspiration and small bore catheters had similar failure rates but patients undergoing needle aspiration were hospitalized less.8 In addition, studies have demonstrated that small catheters are well tolerated and as effective as large bore chest tubes (LBCT).9 All individuals should have a follow-up within 2 to 4 weeks and avoid all air travel until full resolution of the pneumothorax is confirmed.
Secondary spontaneous pneumothorax (SSP), in contract to PSP, occurs in patients with underlying lung pathology. Patients with a SSP are likely to have worsened clinical symptoms than patients with a PSP. Patients with SSP should be admitted to the hospital and most will require intervention. SBCT have been found to be as effective as LBCT and are thus recommended.10 It is largely recommended that these patients be admitted but in some circumstances, patients may be discharged home with a Heimlich valve and follow-up within 2 days.3 If an air leak persists beyond 2 to 4 days, a thoracic surgeon should be consulted for consideration of further intervention.3,4
Provoked or traumatic pneumothoraces can occur from blunt or penetrating injuries or from barotrauma. In the case of trauma victims, the number of pneumothoraces being identified has increased with the availability and ease of CT scanning and bedside ultrasonography. Many of these are considered occult pneumothoraces (OP), defined as a pneumothorax identified on CT or ultrasound, which was not suspected on the preceding chest radiographs. Most experts agree that OP in clinically stable patients can be managed conservatively with observation.11,12,13,14 For patients with OP undergoing positive pressure ventilation (PPV), however, there remains controversy regarding whether or not to intervene. The traditional teaching was to perform tube thoracostomy on patients with occult pneumothorax if they were to undergo any period of PPV, including both prolonged mechanical ventilation during an ICU stay or for a limited time under general anesthesia.15 Recent literature, however, has shown that careful observation and directed intervention when needed of an OP may be safe and there is no difference in mortality or morbidity for these patients.13,14,15,16 For patients chosen for tube thoracostomy, the historical teaching has also been to place a LBCT but recent literature has shown that in many situations, SBCT are considered safe and effective.17
The most feared complication of pneumothorax is that it will progress to tension physiology. Tension pneumothorax occurs when there is a disruption in the visceral or parietal pleural or tracheobronchial tree. A one-way valve forms, which allows air to flow into the pleural space with inhalation and prohibits air from flowing out. With each breath, the volume of air in the intrapleural space and pressure within the hemithorax increases. As the pressure increases, the ipsilateral lung collapses and causes hypoxemia. Eventually, the mediastinum will shift toward the contralateral side and impair the venous return to the heart, causing cardiovascular collapse. The treatment is immediate decompression. The historical treatment for a tension pneumothorax is immediate needle decompression in the second intercostal space at the midclavicular line and subsequent tube thoracostomy. However, many studies have shown that the suggested 14-gauge needle for needle decompression is not long enough to penetrate the chest wall in many patients at this location.18 Alternative approaches for needle decompression are at the fifth intercostal space in the anterior axillary line where the chest wall is generally thinner.19 Studies have also shown that needle decompression is associated with failure rates as high as 58%.20 Despite this evidence, needle decompression is still recommended as first line treatment for tension pneumothorax followed by tube thoracostomy.
Hemothorax is the accumulation of blood in the pleural space. Although the majority of hemothoraces occur as a result of trauma, some do occur in the ICU spontaneously. Also, they may arise as complications from procedures such as thoracentesis and central venous catheterization. These occur due to injuries to the intercostal or internal mammary arteries or pulmonary parenchyma. For traumatic hemothoraces, most surgeons recommend early (within 7 days) drainage of the hemothorax using large bore tubes (36F-42F). If the initial blood drainage is > 1500 mL or > 250 mL/h, surgery may be indicated. Complications such as fibrothorax and empyema can complicate hemothoraces that are not fully drained.
Pleural effusions are abnormal, excessive fluid collections in the pleural space. The differential diagnosis of a pleural effusion is wide and occurs in many conditions, not exclusive to the thoracic cavity. For example, 20% of patients with pancreatitis have accompanying pleural effusion.21 Pleural effusions are divided into two types: transudative and exudative. Transudative effusions develop when systemic factors affecting the formation and absorption of the pleural fluid are altered, causing the pleural fluid to accumulate.22 Conditions where transudative effusions form are with increased interstitial fluid (heart failure), increased peritoneal fluid (cirrhosis), and decreased serum oncotic pressure (hypoproteinemia). Exudative effusions, conversely, develop due to the local alteration of the pleural surfaces or capillaries causing fluid to accumulate. The most common causes of exudative effusions are pleural malignancies, infection, and pulmonary embolism.
Traditionally, supine chest radiograph has been used in critically ill patients to identify acute processes such as pleural effusions. This modality, however, has a low sensitivity and specificity and can often miss large effusions. CT scanning is an excellent tool for identifying and characterizing lung, mediastinal, and pleural disease and quantifying the pleural fluid. Often, initial CT scanning has been replaced by bedside ultrasonography. This modality is noninvasive, low risk, and can be repeated as much as necessary. It can be used to evaluate the pleural space for fluid and often can characterize the complexity of the pleural space. In the hands of a trained user, it is highly sensitive and specific and can identify as little as 5 mL of pleural fluid.23 Figure 94–1 shows ultrasound images of a simple versus complex pleural effusion. If a pleural effusion is identified and if clinically indicated, a thoracentesis and/or tube thoracostomy should be done guided by bedside ultrasonography. For patients with pleural effusion and continued respiratory compromise, drainage of pleural effusions has shown to lead to quick symptomatic improvement in many patients.24
Ultrasound of the right chest showing a pleural effusion marked with *. The image on the left shows a simple effusion while the image on the right demonstrates a complex effusion.
Parapneumonic effusions are any pleural effusion secondary to pneumonia or lung abscess.2 Parapneumonic effusions represent a range of disease beginning with a dynamic, often self-resolving exudative effusion to a complex multiloculated fibrotic and often purulent collection to a thick pleural peal. Patients with pneumonia with an associated parapneumonic effusion have a higher morbidity and mortality than patients who have pneumonia without an effusion.25 Although most simple parapneumonic effusions resolve with antibiotics, about 10% proceed to empyema and fail medical therapy.2 When the effusion worsens, bacteria will cross the damaged endothelium and propagate pleural inflammation. Neutrophils then migrate into the pleural space and the coagulation cascade will be altered, decreasing fibrinolytic activity, causing septations to form within the fluid. Following this, fibroblasts will proliferate and a solid fibrous pleural peel will form over the lung and re-expansion is prevented, creating a persistent pleural space for continued infection.26
For patients with parapneumonic effusions, the current recommendations are to perform a diagnostic thoracentesis to evaluate for empyema.27 If the diagnostic testing reveals a fluid with a pH < 7.2, LDH > 1000, or a glucose < 60 mg/dL, drainage with tube thoracostomy may be indicated. For drainage of an empyema, LBCT are typically used because smaller pigtail catheters have a higher propensity for becoming clogged or dislodged.28 For patients with continued symptoms, fibrinolytic enzymes may be attempted followed by consultation with a thoracic surgeon for resection and open drainage or decortication as indicated.
Chylothorax is a collection of lymphatic fluid in the pleural space. This occurs due to malignancy, congenital abnormalities or injury to the thoracic duct or one of its main branches due to trauma or iatrogenically during a surgical procedure. Diagnosis is made by fluid analysis showing triglyceride level greater than 110 mg/dL or a cholesterol-to-triglyceride ratio of less than 1.29 Treatment, again, depends on the clinical situation. Most patients require initial drainage due to the large volume (2-4 L/d) of chyle produced. Other strategies range from dietary restrictions to surgery.