Chapter 38 ■ Thoracostomy 257

b. Size of fistula or tear

c. Infant position

The dependent placement of the needle puncture site allows reduction of both the alveolar

size and alveolar to pleural pressure difference

in the region surrounding the leak, thereby reducing and possibly stopping pneumothorax formation (9).

3. Rate of evacuation

a. Directly proportional to

(1) Internal radius of chest tube (r

4

)

(2) Pressure gradient across tube (DP)

(a) Suction pressure applied

The negative pressure applied may effect

intrapleural pressure only in the immediate

vicinity of the tip of the tube (4).

(b) Positive intrathoracic pressure during exhalation and spontaneous or mechanical ventilation

b. Inversely proportional to length of tube and

viscosity

Poiseuille’s law regarding flow across a tube is F =

DPπr

4

/8hl, where F = flow; DP = pressure gradient;

r = radius; h = viscosity; and l = length.

E. Precautions

1. Anticipate which infant is at risk of developing pulmonary air leakage and keep equipment for diagnosis and

emergency evacuation at bedside (6,10,11).

2. Recognize that transillumination may be misleading

(12,13).

a. True positive

(1) Follows shape of thoracic cavity (not corona of

light source)

(2) Varies with respiration and position

(3) Has larger area compared with corona of light

b. False positive

(1) Subcutaneous edema

(2) Subcutaneous air

(3) Severe pulmonary interstitial emphysema

c. False negative

(1) Thick chest wall

(2) Darkly pigmented skin

(3) Area over air accumulation obscured by dressing/monitor probe

(4) Weak light due to fiberoptic deterioration or

voltage turned too low

(5) Room too bright

(6) Abnormal color vision in observer

3. Distinguish pleural air collections from skin folds, thymus, Mach effect*, artifacts, or other nonpleural intrathoracic air collections on radiograph (Figs. 38.3–38.6)

(7,14).

4. Select the appropriate insertion site (Figs. 38.7 and 38.8).

Allen et al. (15) recommend inserting the thoracostomy tube in the anterosuperior portion of the chest

wall, in the first to third intercostal space at the midclavicular line, to ensure anterior placement of the chest

tube tip. However, although an anterior insertion may

be appropriate for the right-angled pigtail tube used by

Allen et al., a properly placed lateral tube will have its

tip anterior but, more important, will not leave a (more

visible) scar on the anterior chest and completely

avoids the nipple (see Fig. 38.9).

a. Reduces complications

b. Facilitates insertion of thoracostomy tube into

appropriate position

(1) Anteromedial tip position for air collections

(2) Posterior tip position for fluid accumulation

(Fig. 38.9A, B).

Fig. 38.2. One model of an underwater drainage system,

demonstrating the three necessary chambers. Systems now

are compact and easy to set up and read. This system is set at

22 cm H2O, which would be necessary only for a rapid rate of

air accumulation.

*Appearance on x-ray of a dark or light line where there is a convex or

concave curve in the body shape of the patient.