Method for Estimating the Size of Pneumothorax

 

Method:

(1) Measure the shortest distance between the lung marking and the chest wall at 3 points:

(1a) maximum at the apex

(1b) midpoint of upper lung hemithorax

(1c) midpoint of the lower lung hemithorax

(2) Calculate the average value for these measurements.

(3) Look up the percent pneumothorax from the table below.

 

Technical issues:

(1) The medial aspect of the scapula and large emphysematous bullae should not be mistaken for a pneumothorax.

(2) Measurements from a supine radiograph should not be used since the lung markings may extend to the chest wall (as the trapped air moves anteriorly).

Average Measurement in Centimeters	Size Pneumothorax in Percent
0.5	10%
1.0	14%
1.5	18%
2.0	23%
2.5	27%
3.0	32%
3.5	36%
4.0	40%
5.0	49%

from Wyatt (1999) page 114

 

When this data is analyzed in JMP, the following linear relationship is obtained:

 

size of the pneumothorax in percent =

= (8.71935 * (average measurement in cm)) + 5.3839

 

Performance:

• The equation gave consistent results, with r = 0.96 and the residual error –2.4 +/- 7.23%.