In this study, we evaluated the effect of chest tube position on treatment failure. Our study findings, which were derived from 87 empyema patients, suggest that chest tube drain tip positioning below the 10th or above the 9th thoracic vertebra, had no effect on treatment failure. To the best of our knowledge, this is the first study to evaluate the relationship between the level of the chest tube tip positioning and empyema treatment failure.
Our findings have important clinical implications for physicians treating empyema. Past guidelines and the idea that fluid collects in the most dependent portion suggest that chest tube drains are most effective when placed in the lowest portion of the thoracic cavity . Clinicians typically insert a chest tube through the lower intercostal space, and once verified to be in the thoracic cavity, it is pushed down to the level of the diaphragm so that it is optimally placed in inferior and most dependent portion of the chest.
Tube malposition is the most common complication of tube thoracostomy . Drain insertion under image guidance has been proven to be effective and is therefore, now being widely practiced . However, as shown in our study, if the only important factor is that the drain tube is inserted properly without malposition, and the height of the tip does not affect treatment failure for empyema, then it can lead to reduction of procedure time on targeting the bottom in the thoracic cavity and avoidance of complications (organ injury, e.g., liver, spleen) caused by aiming at a lower position in the thoracic cavity.
There are several possible reasons why the level of drain tip did not affect treatment failure in this study. First, the position of fluid retention depends on the patient's position . Usually, hospitalized patients with chest tube drains are in bed rest because of pain. Because pleural effusions accumulate in a gravity-dependent manner, they may move dorsally or laterally rather than at a lower position, depending on the position of the patient. This position-dependent migration of pleural fluid within the thoracic cavity might be the reason why the level of the drain tip did not affect treatment failure. The second reason is the high rate of urokinase usage. Urokinase is a fibrinolytic enzyme. This breaks down fibrinous adhesions, which are part of the organization process and are responsible for the encapsulated pus . In this study, urokinase was used in more than 75% of both groups, which may have decreased the viscosity of the empyema and facilitated drainage independent of the height of the drainage tube.
This study has several limitations. First, this was a retrospective single-center study. Because this study did not follow a standardized protocol, the selection of antibiotics, techniques, drain types and sizes used, type of medical personnel performing the pleural drainage, urokinase use, and selection of next treatment options in case of treatment failure were determined according to the treating physician’s judgement of the individual patients’ needs. These factors may preclude the extrapolation of our conclusions to other facilities. Second, in this study, we defined the lower position group as those with the tip of the drain tube positioned below the 10th thoracic vertebra, which is generally considered to be just above the diaphragm. However, since this is the first study to examine the influence of the level of the drain tip in the thoracic cavity on treatment failure in empyema, the validity of this definition has not yet been clearly established. Ideally, the drain tip position should be measured at each thoracic vertebral height in many patients to confirm that the drain tip position does not contribute to treatment failure. Third, even after weighting adjustment, some confounding factors could not be balanced. The lower-position group had a low BMI and a high RAPID score. As people with a low BMI and high RAPID score tend to be skinnier and frailer, the lower intercostal spaces are more easily identifiable. A low BMI and high RAPID score were associated with poor prognosis, which may have influenced our results [17, 25]. If the study were conducted with a larger sample size and well balanced in both groups, placement of the drain tip in a lower position might have been related with lower treatment failure. Therefore, a prospective multicenter randomized controlled trial with a standardized protocol and larger sample size is needed to confirm our results.