Needle Thoracostomy: Implications of Chest Wall Thickness for Anatomical Location and Needle Length

Needle thoracostomy is a lifesaving intervention for tension pneumothorax, but increased chest wall thickness in obesity may reduce success rates. This study compared chest wall thickness at the second intercostal space in the midclavicular line (ICS 2-MCL) and fourth/fifth intercostal space in the anterior axillary line (ICS 4/5-AAL) across obesity categories and relative to needle length.

Prospective cross-sectional study including 110 patients with class II and III obesity (body mass index [BMI] 36 to 71 kg/m²). Chest wall thickness was measured using ultrasound at ICS 2-MCL and ICS 4/5-AAL. Linear mixed-effects models assessed effects of BMI, location, and sex on chest wall thickness. The proportion with chest wall thickness exceeding 50 mm or 83 mm needle length was determined at each location.

Chest wall thickness was greater at ICS 4/5-AAL than at ICS 2-MCL across the BMI range. The BMI effect on chest wall thickness differed between locations, increasing 11.3 mm per 10 kg/m² at ICS 4/5-AAL versus 4.2 mm per 10 kg/m² at ICS 2-MCL. Chest wall thickness exceeded 50 mm in 22% (95% confidence interval [CI] 15% to 31%) at ICS 2-MCL versus 82% (95% CI 73% to 89%) at ICS 4/5-AAL. No patient exceeded 83 mm at ICS 2-MCL; 21% (95% CI 14% to 30%) did at ICS 4/5-AAL.

In patients with class II and III obesity, chest wall thickness at ICS 2-MCL is lower and less sensitive to increasing BMI than at ICS 4/5-AAL. No patient exceeded 83 mm at this site, suggesting this combination may maximize pleural space access.