Pneumothorax Risk Factors

There are many factors that seem to influence the incidence of pneumothorax following a needle aspiration biopsy of the lung. They are related to host factors, features of the lesion and technical issues.

Host Factors

Age:
Older patients develop pneumothorax more frequently than younger patients following a needle biopsy.
Uncooperative Patient:
It is very difficult to perform a needle aspiration biopsy in a uncooperative patient. The risk of an excessive tear to the lung is higher if the patient is unable to stay still. Thus, this increases the risk for pneumothorax.
Emphysema:
Patients with emphysema and blebs have a higher probability of developing pneumothorax. Patients with a higher total lung capacity have a higher incidence of pneumothorax associated with needle aspiration biopsy of the lung.
Prior Thoracotomy:
A needle biopsy is associated with less incidence of pneumothorax in patients who have had a prior thoracotomy. This may be due to pleural adhesions.

Lesion

Size:
Biopsy of smaller lesions are associated with a higher incidence of pneumothorax. It is more difficult to guide the needle into a smaller lesion; thus, increasing the time in the chest and the need for multiple passes. Both of these factors are associated with a higher risk of pneumothorax.
Depth from Chest Wall
The distance of the lesion from the chest wall is most strongly associated with the incidence of pneumothorax. The greater the depth of needle penetration in the lung, the greater the incidence of pneumothorax, which can be estimated by an equation.
Cavitating Lesions:
Biopsy of cavitating lesions are associated with higher incidence of hemoptysis and pneumothorax.

Technical

Size of Needle:
The size of the needle for lung aspiration biopsy range from 14 to 25. The thinner the needle, the less the incidence of pneumothorax. The needles that provide a core of tissue tend to be wider with an increased incidence of pneumothorax. The choice largely depends upon the location, size and anticipated diagnosis of the lesion.
Length of Time Needle Stays in Chest:
The longer the needle stays in the chest, the higher the risk for pneumothorax. This factor, is one minor disadvantage for CT guided biopsy procedures.
Number of Fissures Crossed:
The number of fissures crossed by the needle is a factor. If the needle crosses fissures, the risk for pneumothorax is higher. Every fissure crossed adds two more holes in visceral pleura.
Number of Needle Passes:
Multiple passes increase the risk for pneumothorax. Quick read technique has been introduced to minimize the number of needle passes. The pathologist performs a modified wright stain on the spot. The staining process takes about 20 seconds and the slides are examined wet. The pathologist decides on the adequacy of the sample. The next puncture is preformed only if the first puncture failed to obtain a diagnostic or adequate specimen.
Core Tissue:
100% Oxygen Breathing:
In one study, administration of 100% oxygen prior to and during the procedure minimized the incidence of pneumothorax. In a second study, this observation was not confirmed. Both the reports did show rapid absorption of pneumothorax in patients who were given oxygen. It is certainly reasonable to consider this approach in patients with compromised lung function to minimize the duration of ill effects of pneumothorax.
Experience:

Old age, uncooperative patients, COPD, blebs, smaller lesions, central lesions, cavitating lesions, large needles, longer amounts of time in the chest and multiple passes are all factors associated with increased incidence of pneumothorax. Prior thoracotomy, 100% oxygen breathing and experience are associated with decreased incidence. There is nothing one can do to alter some of these factors. However, we can minimize the risk of pneumothorax by:

Using thinner needles.
Staying the least amount of time in the chest.
Minimizing the number of passes; this can be done by adopting quick cytology review.
Use 100% oxygen for 15 minutes during the procedure.
Let the experienced physician biopsy small, deeper lesions.