Introduction

A pneumothorax is an emergent medical condition that requires rapid and accurate evaluation and treatment. There are multiple etiologies of a pneumothorax, including a ruptured bleb within the lung, pneumothorax secondary to traumatic injury, or a spontaneous pneumothorax. If not treated appropriately, a pneumothorax can lead to respiratory and cardiovascular compromise.

Though a pneumothorax can occur by various mechanisms, this section will focus primarily on primary spontaneous pneumothorax (PSP) which is defined as a pneumothorax occurring without inciting trauma or the presence of clinically apparent lung disease [21–23]. Data on the age-adjusted incidence of PSP ranges from 7.4 to 24/100,000 per year in males and 1.2 to 9.8/100,000 per year in females [24–26].

Management options for a PSP include tube thoracostomy, small-bore pleural catheter, needle aspiration, and observation, but international guidelines and standard practice are variable [21]. The American College of Chest Physicians (ACCP) recommends tube thoracostomy or a pleural catheter as the first-line treatment of symptomatic pneumothorax and endorses the use of needle aspiration only for stable patients with small pneumothoraces [27]. In contrast, the British Thoracic Society (BTS) guidelines recommend that needle aspiration be the first-line management for stable patients less than 50 years old with a PSP [23, 28, 29]. Traumatic pneumothorax is not addressed in the BTS or ACCP guidelines.

While no consensus exists on the management of pneumothorax, there is a growing body of evidence supporting needle aspiration of pneumothorax in patients with uncomplicated first-time PSP [30, 31]. Several prospective studies have shown promising results for needle aspiration [22, 29, 30, 32–35]. Compared to tube thoracostomy, needle aspiration has been shown to have similar clinical outcomes [33, 34], is less invasive and painful, leads to decreased admission rates and hospital length of stay, and has similar 1-year recurrence rates of pneumothorax [29, 30, 35].

Advantages of Ultrasound Guidance

Lung ultrasound has demonstrated better sensitivity (89% vs. 52%) and comparable specificity (98% vs. 99%) in detecting pneumothorax when compared to chest x-ray [36–38] and has also been shown to be superior in detecting residual pneumothoraces after chest tube insertion [39].

Anatomy

The anterior chest wall is delineated by the clavicle superiorly, the diaphragm inferiorly, by the sternum medially, and the mid-axillary line laterally [40]. In general, air will rise to the least dependent portion of the hemithorax, which in a supine patient is at the anteromedial portion of the chest. However, in patients with a high degree of suspicion for pneumothorax, there is utility in sonographically evaluating a larger area.

To sonographically evaluate for pneumothorax, a high-frequency probe is placed in a longitudinal axis over the anterior chest wall between two ribs. Posterior shadowing will be noted deep to the ribs. The pleural interface appears as a hyperechoic line between the two rib shadows. This view has been described by Lichtenstein as the “bat sign” [38] (Fig. 14.5). Normal pleura exhibits a characteristic shimmering appearance that is synchronized with respirations [40]. In addition, M-mode can demonstrate the presence of normal lung sliding by generating a “seashore sign,” which appears as a granular pattern below the pleural line (Fig. 14.6). In the absence of lung sliding, M-mode will demonstrate a “stratosphere sign” (also known as “barcode sign”), in which the granular pattern is replaced by horizontal lines [38] as shown in Fig. 14.7. Alternatively, the “power slide” uses power Doppler to detect movement at the pleural line (Fig. 14.8) [41]. M-mode and power Doppler both have the advantage over B-mode imaging of being able to capture the presence of lung sliding in a static ultrasound image.

Ultrasonographic diagnosis of pneumothorax depends on three sonographic findings: (1) absence of lung sliding, (2) the A-line sign, and (3) the lung point [40, 42, 43]. The absence of lung sliding represents air within the thoracic cavity which has caused the normally apposed visceral and parietal pleura to separate. The A-line sign (the presence of A-lines without B-lines) in conjunction with absent lung sliding is 96.5% specific for the presence of pneumothorax [40]. Finally, the lung point represents the transition point between normal lung sliding and adjacent pneumothorax (Fig. 14.9). While the lung point is not always visualized, its presence has been shown to be 100% specific for pneumothorax [38, 43].

Existing guidelines recommend drainage of large pneumothoraces even if the patient appears clinically well, making estimation of pneumothorax size an important aspect of assessing a patient prior to performing an aspiration. However definitions for a “large” pneumothorax differ [23, 27, 44]. While computed tomography (CT) of the chest is the most accurate method of measuring pneumothorax volume, it is not always an indicated or available imaging modality. Several methods have been suggested for estimating pneumothorax volume on chest radiograph [23]. According to ACCP guidelines, a distance greater than 3 cm from the lung cupola to the apex of the thoracic cavity represents a “large” pneumothorax [27]. BTS guidelines define a “large” pneumothorax as a rim of air greater than 2 cm at the level of the hilum on chest radiograph [28]. The Belgian Society of Pulmonology (BSP) defines a “large” pneumothorax as one that extends along the entire length of the lateral chest wall [44]. However, there is poor agreement among the size classification methods described by the AACP, BTS, and BSP, and in one retrospective study, the use of these different methods resulted in agreement in only 47% of cases [45].

Point-of-care ultrasound may be a useful method to estimate the size of pneumothoraces. In a prospective study of 58 patients who had a CT diagnosis of pneumothorax, sonography reliably predicted larger pneumothorax volumes. A lung point located anterior to the mid-axillary line, at the mid-axillary line, and posterior to the mid-axillary line were predictive of a pneumothorax size of less than 10%, between 11% and 30%, and greater than 30%, respectively [46].

Indications

According to the BTS Guidelines, needle aspiration of pneumothorax is indicated in stable patients less than 50 years of age with a symptomatic PSP measuring greater than 2 cm at the level of the hilum on chest x-ray or a PSP of any size from which the patient is symptomatic [23].

Contraindications

Patients who are over the age of 50 with a smoking history or evidence of underlying lung disease based on physical examination, history, or chest x-ray are not suitable candidates for aspiration. Other contraindications include patients with unstable vital signs, tension or bilateral pneumothoraces, or associated pleural effusions (hydropneumothorax). In addition, as mentioned above, skin with overlying areas of cellulitis or herpes zoster should not be pierced. Recurrent pneumothorax is a relative contraindication as such cases are likely to require more aggressive interventions such as chest tube drainage, pleurodesis, or VATS (video-assisted thoracoscopic surgery) [47–50]. Finally, repeat needle aspiration following a failed attempt is not recommended as it is unlikely to be successful in the absence of a technical issue such as a blocked or kinked catheter [23].

Though, some experts recommend chest tube or small-bore catheter placement for pneumothoraces that are 40% or larger [51, 52], BTS guidelines suggest PSP of all sizes can be drained by needle aspiration.

Equipment/Probe Selection

The equipment necessary for this procedure is depicted in Fig. 14.10. A high-frequency linear probe is ideal for the detection of pneumothorax using the previously described methods.

Preparation/Pre-procedural Evaluation

For this procedure, place the patient in a supine position with the arm ipsilateral to the pneumothorax raised above the patient’s head. In this position, inter-pleural air will preferentially collect in the nondependent anteromedial portion of the patient’s chest. Using tactile and visual landmarks, identify and mark the second intercostal space in the midclavicular line. This location is where the needle aspiration will be performed. Using a high-frequency linear probe oriented in the sagittal plane and starting at the marked needle aspiration site, locate the lung point by sliding the transducer laterally. Mark the skin with a surgical marker at the lung point so that it can be readily located later [53–55].

Procedure

This procedure requires two individuals, one person performing the aspiration while the other sonographically tracking the lung point. Alternatively, if there is a single operator, the location of the lung point can be checked intermittently throughout the procedure.

In addition to standard sterile patient preparation, the transducer is covered with the sterile probe cover and placed onto the field. At the previously identified location at the second intercostal space in the midclavicular line, the soft tissue should be anesthetized along the superior margin of the third rib in order to avoid the neurovascular bundle that lies just below the second rib. The needle is advanced until bubbles are seen in the syringe, which should still contain lidocaine. These bubbles indicate that the pleural space has been entered. While the needle is slowly withdrawn, lidocaine is instilled into the tissues between the pleura and the skin surface. Next, while applying continuous negative pressure on the plunger, insert the 16 g catheter over a needle attached to a 10 mL syringe filled with 3–5 mL of sterile saline or lidocaine. As soon as bubbles are seen in the syringe, advance the needle a few millimeters further to ensure that the catheter tip is fully within the pleural space (Fig. 14.11). Have the patient cough or exhale while removing the needle and syringe, and simultaneously advance the catheter. Immediately occlude the catheter opening to prevent additional air from entering the pleural space. Attach the preassembled tubing, three-way stopcock, and 60 mL syringe to the end of the catheter. It is critical to ensure that the stopcock is never open between the patient and the ambient air as this will worsen the pneumothorax. Locate the lung point with the linear transducer, and with the stopcock closed to ambient air, begin aspirating the pneumothorax into the syringe. As the lung re-expands, the lung point will move anteriorly and medially. While aspirating, have a second operator track the lung point in real time as it moves toward the catheter insertion site (Fig. 14.12). Once the syringe is full, evacuate it to ambient air by closing the stopcock to the patient (Fig. 14.13). Repeat the process of aspirating air from the patient’s chest and evacuating it until the lung point reaches the catheter site or no more air can be drawn into the syringe. Keep track of the total volume aspirated by counting the number of times the syringe is filled. If air continues to be aspirated after evacuating 2.5 L, the procedure should be stopped as it may indicate an air leak [23]. At the completion of the procedure, remove the catheter and place a sterile occlusive dressing on the chest at the needle insertion site [54, 55].

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