The role of gravitational effects and pre-puncture techniques in reducing pneumothorax during CT-guided lung biopsies

Abstract

Purpose: The study aimed to evaluate whether the relative height (RH) of the entry point (EP) during CT-guided lung biopsies, adjusted for patient positioning, can predict the risk of pneumothorax during the intervention, leveraging the gravitational effects on pleural pressure.

Materials and methods: We retrospectively analyzed 128 percutaneous CT-guided lung biopsies performed at a single center between January 2018 and December 2023. Patients were grouped based on pneumothorax occurrence. Various measurement methods indirectly assessed the influence of gravitational force on pleural pressure, focusing on the RH at the EP with prone positioning adjustments (PP). Other confounding factors like patient demographics, lesion characteristics, pre-puncture fluid administration and other procedural details were assessed. Test performance metrics were compared using Chi-Square, Fisher's exact, and Mann-Whitney U tests. Univariate and binomial logistic regression assessed the influence of different parameters on pneumothorax occurrence.

Results: All measurements of lower RH at EP and pre-puncture fluid administration were significantly associated with a reduced incidence of peri-interventional pneumothorax (p < 0.01). The RH at EP adjusted for the prone position demonstrated the best predictive performance (AUC = 0.844). After adjusting for various confounding factors, both lower RH at EP adjusted for the prone position (OR 110.114, p < 0.001) and pleural fluid administration (OR 0.011, p = 0.011) remained independently associated with a lower risk of pneumothorax.

Conclusion: Strategic use of gravity by selecting the lowest possible entry point, ideally positioning the patient laterally, combined with pre-puncture pleural fluid administration, could be the key to reducing pneumothorax in CT-guided lung biopsies.

Keywords: Biopsy; Image-guided biopsy; Lung; Patient positioning; Pneumothorax; Postoperative complications tomography.

Fig. 1

Graphical abstract—schematic illustration of the presumed influence of gravitational force (GF) based on patient position In This Study. A, D Pleural pressure (PPL) decreases linearly from the non-dependent upper to the dependent lower lung regions, primarily due to the gravitational effects of lung weight [, , , –47]. Represented by red, orange and green gravitational field lines to indicate the degree of gravity. The blue arrow indicates the pleural pressure that steadily increases due to gravitational force. B, C The patient was in the prone position with the coaxial needle inserted posteriorly, targeting the lesion (asterisk). A pneumothorax occurred immediately post-intervention. D The patient was positioned in the lateral decubitus position with the biopsy-side down to prevent pneumothorax. The coaxial needle tip is near the target lesion (asterisk). E Following a full core lung biopsy, a pneumothorax and a pulmonary hemorrhage (red area) were observed

Fig. 2

Flowchart with the study population

Fig. 3

A schematic illustration of CT-guided lung biopsy with localized fluid application in the subpleural space to elevate pleural pressure, thereby reducing the risk of pneumothorax

Fig. 4

Indirect measurement of the gravitational force influence, derived from the vertical pleural pressure gradient (PPL) at the entry point. A Patient in the supine position. The suspicious lung mass is accessed with the biopsy needle from the anterior. The entry point height measured in millimeters was correlated with the corresponding lung height at the same layer level and on the same side. B In the lateral position, the total lung height is used as a reference. The indirect GF, representing RH for EP without adjustment for PP, was calculated as follows: APD R EP/ max. APD. Max. APD, maximum anteroposterior distance; APD R EP, anteroposterior distance in relation to the entry point; GF, gravitational force; RH, relative height; EP, entry point; PP, prone position all distances are measured in millimeters (mm)

Fig. 5

Indirect measurement of the influence of gravitational force, derived from the vertical pleural pressure gradient (PPL) at the entry point, accounting for the specific conditions in the prone position. Same patient in A supine and B prone position with puncture site (red arrowhead) at the same level in the upper third of the left thorax. According to Kallet’s model [41], in the supine position, gravity increases strain due to the Slinky® effect of a triangular spring suspended from its apex (supine position). In contrast, in the prone position results in more even strain distribution and reducing stress inhomogeneity. This could explain the halved vertical pleural pressure gradient in the prone position observed in the dog model of Hoppin et al. [42]. B Consequently, the indirect GF as RH at EP with adaptation for PP was calculated in the prone position as follows: (APD R EP/ max. APD)/2. The double arrow indicates the difference to the maximum APD. Max. APD, max. anteroposterior distance; APD R EP, anteroposterior distance in relation to the entry point; GF, gravitational force; RH, relative height; EP, entry point; PP, prone position

Fig. 6

Physically approximated models derived from geometric shapes to assess the effect of gravitational force on pleural pressure

Fig. 7

Schematic illustration of the zoning used for this study according to position-dependent gravitational effect on pleural pressure (PPL). For zoning, we applied the rule of thirds. Only the zone "RED" was determined as non-dependent

Fig. 8

Validation of ROC (Receiver Operating Characteristic) Curves and Performance Metrics for Gravitational Force Parameters in Pneumothorax. RH, relative height; PP, prone position; PMC, physical measurement calculation; ND, non-dependent

Fig. 9

Optimal patient positioning to benefit from the gravitational force of the lungs’ own weight. Color gradation from red to green with green as the best choice for patient positioning. The nearest access routes are shown with a blue arrow. The dashed line represents the height of the entry point, where the biopsy needle passes through the pleura. H1 and H2 illustrate the height difference of the entry point relative to the patient’s baseline in different positions, demonstrating the extent of change caused by repositioning. A The reduced decrease in pleural pressure in the prone position, combined with the puncture direction aligned with gravity, significantly increases the risk of pneumothorax; B, C In both the supine and lateral positions, the gravitational force of the lung above the access route is utilized. In the strict lateral position, the gravitational force of the mediastinal masses further enhances this effect. D The patient is positioned in a lateral oblique position using a wedge cushion, which helps reduce the height of the access route. The green arrow shows the reduced height of the entry point in direct comparison to the strict lateral position. E No pneumothorax resulted after the biopsy