Defining the optimal timing of interval chest radiograph in conservatively managed small pneumothorax from thoracic stab wounds – a South African experience

Introduction

Pneumothorax (PTX) following a stab wound (SW) of the chest is a potentially life-threatening condition, and tube thoracostomy (TT) has long been the standard treatment for the majority of these patients.^1–7 In a well-defined cohort of patients with small PTX, a selective conservative approach may be appropriate.^8–12 This highly selected cohort can simply be actively observed. Seminal studies by various authors from King Edward VIII Hospital in Durban, South Africa have supported such an approach.^8–10 This approach is reliant on clinical assessment, coupled with interval chest radiograph (CXR), to determine the need for subsequent intervention (i.e., TT) during the period of active clinical observation.^8–10 The optimal timing of the interval CXR in this setting however, has never been clarified.^8–12 Historically, the practice at our institution has been to obtain an interval CXR at approximately 12 hours following admission. Due to resource and logistical constraints, we commonly experience lengthy delays in obtaining an interval CXR.^12,13 These challenges in obtaining an interval CXR may translate into delayed discharge of patients, thereby compounding ongoing issues of hospital ward overcrowding. The aim of this study was to review the timing of interval CXR in a specific subset of patients who were asymptomatic, with a small PTX < 0.5 cm following thoracic SWs that were managed conservatively, and to determine the rate of complete resolution of PTX on CXR at various time intervals. It is hoped that this may allow streamlining our discharge protocols and optimise patient flow in our high volume trauma centre.

Materials and methods

Results

Interval CXR timing

Of the 50 patients, 70% (35/50) had their interval CXR performed at 12 hours. Table 1 summarises the proportion of patients who had their interval CXR at the different time intervals, along with the complete resolution rate.

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Table 1.

Proportion of patients who had their interval CXR at the different time intervals, along with the complete resolution rate.

CXR timing (hours)	Number (N = 50)	%	Complete resolution	%
12	35	70%	35	100%
12–16	8	16%	8	100%
16–20	4	8%	4	100%
20–24	3	6%	3	100%

Discussion

Evidence predominantly from high volume trauma centres in South Africa has supported the safety of selective conservative management of small PTXs following SWs of the chest.^8–12 Provided the patient remains asymptomatic and interval CXR demonstrates resolution, then the patient can be safely discharged.^8–12 Historical studies from our parent institution at King Edward VIII Hospital in Durban, South Africa, have documented the safety of such an approach.^8–10 Furthermore, the success rate of conservative management of small PTX appeared to be related to the actual size, and in those between 0.5 and 2 cm (on CXR), the risk of requiring a TT is approximately 3%. ¹² What remains unclear however, is the optimal timing of interval CXR. With the ever-increasing pressure on hospital beds and resources in our environment, it is advantageous to reduce delays in interval CXR and facilitate earlier discharge. Our study demonstrated significant variation in the precise timing of interval CXR and that patients, who had their interval CXR as early as 12 hours following admission in fact, demonstrated complete resolution of their PTX. A small subset of patients obtained their interval CXR between 12 and 24 hours. In all these delayed cases, there was also complete resolution on interval CXR.

PTX denotes air within the pleural space and is one of the most common sequelae of a thoracic SW.^8–10,14,15 There remains a great deal of confusion over the applicability of evidence in the management of patients with traumatic PTX. Many studies cross reference evidence from the treatment of spontaneous PTX.^16–19 Spontaneous PTX cannot be considered analogous to traumatic PTX as their pathophysiology are significantly different.^16–18 A point often cited from this heterogeneous evidence is that the rate of resolution of PTX is estimated to be 1.25% to 2.2% of thoracic volume every 24 hours. ¹⁸ This evidence was originated from studies on spontaneous PTX and cannot be extrapolated directly to PTX in the setting of thoracic SWs.^18,19

One of the major limitations of this study is the lack of randomisation regarding the timing of CXR, as this study was not designed with such methodology. Furthermore, the selective management protocol is specific to our institution and the practice may differ elsewhere. Nevertheless, interval CXR at 12 hours invariably demonstrates complete resolution of PTX < 0.5 cm and waiting up to 24 hours to perform an interval CXR is unnecessary.

Conclusions

In patients with asymptomatic small PTX < 0.5 cm, interval CXR at 12 hours invariably demonstrates complete resolution and waiting up to 24 hours is unnecessary.