Background  The most commonly used first-aid equipment for tension pneumothorax is decompression needle. There are recommended values for the length of needle in foreign countries. However related research and data are absent in China.

  Objective  To analyze the average chest wall thickness (CWT) based on computed tomography, and determine the optimal length and inserting site of pneumothorax decompression needle suitable for young Chinese adults.

  Methods  A retrospective radiographic analysis was performed in patients aged from 18 to 40 years old admitted to the department of thoracic surgery, the First Medical Center of Chinese PLA General Hospital from January to December in 2019. The CWT was measured at the anterior approach puncture point (the 2nd intercostal space of midclavicular line) and the lateral approach puncture point (the 5th intercostal space of anterior axillary line) bilaterally using Medicare picture archiving and communication system. Three needles with different sizes were evaluated regarding sufficient length for decompression and the data were analyzed statistically.

  Results  Among the 294 eligible subjects, there were 135 males and 159 females, with average age of 33.76 ± 5.41 yrs. The CWT of the anterior approach ranged from 13.20 mm to 69.09 mm, and that of the lateral approach ranged from 8.19 mm to 52.70 mm. For the same side, mean CWT of anterior approach was greater than that of lateral approach (right: 35.33 ± 9.62 mm vs 23.17 ± 7.14 mm; left: 34.91 ± 9.65 mm vs 22.59 ± 7.43 mm; P＜0.01, respectively). For the same puncture point, the mean CWT of women was greater than that of men (right anterior approach (36.57 ± 10.11 mm vs 33.88 ± 8.83 mm, right lateral approach: 24.53 ± 7.84 mm vs 21.55 ± 5.85 mm; left anterior approach: 36.19 ± 10.23 mm vs 33.41 ± 8.71 mm, left lateral approach: 23.98 ± 8.15 mm vs 20.95 ± 6.11 mm; P＜0.01, respectively), and the mean CWT of overweight patients (BMI ≥ 24) was greater than that of non-overweight patients (BMI＜24) (right anterior approach: 40.57 ± 9.93 mm vs 31.24 ± 7.08 mm, right lateral approach: 26.17 ± 7.12 mm vs 20.82 ± 6.24 mm, left anterior approach: 40.23 ± 9.93 mm vs 30.75 ± 7.05 mm; left lateral approach: 25.68 ± 7.56 mm vs 20.17 ± 6.37 mm, P＜0.01, respectively). The CWT was positively correlated with BMI (all P＜0.01).

  Conclusion  A 70 mm needle would have reached the pleural space in 100% of subjects in this case series. Gender, BMI, approach and other factors should be taken into consideration during thoracentesis. The lateral approach may be an alternative choice in first aid for tension pneumothorax.