Lung Herniation as a Result of Cardiopulmonary Resuscitation (CPR): A Case Report and Literature Review

Lung herniation is a rare complication following cardiopulmonary resuscitation (CPR) and is defined as a protrusion of lung parenchyma through the thoracic wall. This article presents a case in which a patient presented to the hospital with sepsis secondary to community-acquired pneumonia. A 74-year-old female with a background of chronic obstructive pulmonary disease (COPD) suffered a sudden pulseless electrical activity (PEA) cardiac arrest while being managed in the acute medical ward. The CT following the return of spontaneous circulation (ROSC) demonstrated multiple bilateral anterior rib fractures and herniation of the right lung through the right lateral thoracic wall. She was managed in the ICU with ventilatory and cardiovascular support for four days until she suffered a second cardiac arrest, where resuscitation was unsuccessful. In addition to this case report, a literature review was carried out, given the rarity of this pathology. The literature provides only 13 articles on lung herniation due to CPR. The most common injury pattern was anterior rib fractures leading to anterior lung herniation. In our case report, the herniation was away from the fracture site at the lateral chest wall. A common complication was surgical emphysema in several of the articles, as was in our case. The surgical intervention appears to be indicated in large hernias, incarceration, or those causing pain and respiratory compromise. In our case, conservative management was elected, given the patient’s significant persistent cardiovascular instability unsuitable for interhospital transfer. A high index of suspicion should be adopted for patients who undergo a prolonged period of CPR, including frail patients with underlying health conditions such as chronic lung disease.


Introduction
Lung herniation is a rare complication of cardiopulmonary resuscitation (CPR). It is defined as a protrusion of lung parenchyma through the thoracic wall and is classified according to location and etiology [1,2]. It is approximated that 80% of thoracic wall lung herniation is most commonly related to trauma either blunt or penetrating and after chest wall surgery [1]. This case report demonstrates the rare occurrence of lung herniation following CPR.

Case Presentation
A 74-year-old female presented to the acute medical unit (AMU) with 24 hours of worsening dyspnea and productive cough. She was an ex-smoker with a 40-50 years smoking history and chronic obstructive pulmonary disease (COPD). She suffered a deterioration in her respiratory function over the preceding two years, requiring triple therapy inhalers (inhaled corticosteroids [IHS], long-acting beta-agonists [LAMA], long-acting muscarinic antagonists [LAMA]) and having received multiple acute courses of antibiotics and steroids in the community for infective exacerbations of COPD (IECOPD). She was reportedly independent in the community, and her past medical history included osteoporosis, a known aortic aneurysm, non-alcoholic fatty liver disease (NAFLD), and gallstones.
Physical examination revealed a new oxygen requirement with oxygen saturations of 82% on room air, tachycardia, and pyrexia with stable blood pressure. Initial management for IECOPD was commenced and escalated to full sepsis protocol due to ongoing deterioration in the form of increasing oxygen requirements and persistent tachycardia.
After 10 hours into her admission, she suddenly collapsed into PEA cardiac arrest. Immediate CPR following advanced life support (ALS) protocol was commenced. With high-quality manual CPR administered by trained staff throughout and 4x adrenaline (10ml of 1:10000 IV) given, return of spontaneous circulation (ROSC) was achieved after 29 minutes of arrest time. Bedside echocardiogram and chest X-ray at this time were unremarkable. Arterial blood gas demonstrated a metabolic acidosis with type 2 respiratory failure.
She was transferred to the ICU for standard post-cardiac arrest care, including intubation, ventilation, sedation, and required inotropes for cardiovascular support.
Owing to the sudden collapse, she underwent diagnostic imaging, including CT of the head, chest, and abdomen, to rule out pulmonary embolism and intracranial hemorrhage as a cause for cardiac arrest and establish the source of sepsis. This demonstrated right lower, middle, and upper lobe consolidation with bibasal atelectasis, a likely source of sepsis. Multiple bilateral anterior rib fractures, in keeping with CPR, and herniation of the right lung through the right lateral thoracic wall were noted (Figures 1-2). High-resolution CT performed one month before admission was available for comparison and showed continued extensive emphysematous change, as noted on both CT reports.  She required a ventilator and cardiovascular support throughout her ICU admission and remained sedated with propofol and alfentanil. Significant chest wall bruising to the anterior and right lateral chest was noted, with a small palpable mass and some surgical emphysema at the right lateral wall over the site of the herniation. While primary rib fixation was discussed, her pivotal problem was persistent cardiovascular instability, and she remained too clinically unstable for safe interhospital transfer for surgical intervention. Neurology remained poor despite weaning sedation. There was no requirement for renal replacement therapy. Broad-spectrum antibiotics were continued for sepsis. She suffered a second cardiac arrest four days into her ICU admission due to persistent cardiovascular instability and multi-organ failure. Despite CPR and maximal medical support, this was a terminal event.

Literature review
Lung herniation following CPR is a rare event. Using the search terms 'cardiopulmonary resuscitation,' 'CPR,' 'lung herniation,' and' pulmonary herniation' across Ovid, EMBASE, and PubMed search engines, 13 articles and case studies have been recorded prior to this report. Detailed results of the literature review are presented in Table 1. Of the 13 articles, one was unable to distinguish between surgical emphysema and lung herniation and was therefore removed for the purposes of analysis [3]. A total of 10/12 patients were 65 years or over, with seven male (1x gender undocumented) and three with known COPD. Only three diagnoses of lung herniation were on the day of cardiac arrest, with some prolonged to over one week. The most common injury pattern was anterior rib fractures leading to anterior lung herniation. One case documented herniation without fracture, and in our case report, the lung herniation was away from the fracture site at the lateral chest wall. The cohort had variable outcomes, with four receiving cardiothoracic surgery and others for chest drain insertion and conservative management.    Multiple rib fractures and sternal fractures are common resulting features after CPR, with up to 97% and 43% of people affected, respectively [15]. Despite the high prevalence of thoracic wall injury, lung herniation remains a rare incidence following CPR, with previous studies demonstrating no evidence in a cohort of over 700 individuals [16].
Frailty and preexisting medical conditions can predispose an individual to a more extensive injury pattern. This, combined with high-quality chest compressions, puts individuals at higher risk of severe thoracic injury after CPR [8]. With the introduction of mechanical chest compression devices, two case reports in the last five years demonstrate a resultant lung herniation. However, further evidence is needed to ascertain if this will increase the incidence of thoracic trauma compared to manual chest compression [8,9].
CT has been the modality to identify lung herniation throughout all reported cases. Physical examination may identify a bulge at the site of the lung herniation, and clinically there has been increased respiratory distress both in ventilated and non-ventilated patients. Chest X-ray (CXR) commonly reveals rib fractures, surgical emphysema, and loculated air pockets but is not the imaging modality of choice for lung herniation [7,13,17]. Surgical emphysema on CXR has been shown to mask underlying pathology and therefore has been the main indication for a CT in these cases [5,9]. In each case, CT has demonstrated the site and extent of the lung herniation and other injury patterns [17]. The lung herniates most commonly anteriorly or at the fracture site [4,6,14]. In our case, the lung herniated laterally away from the fracture site. Herniation may occur even in the absence of rib fractures [11].
Four patients underwent cardiothoracic surgery for rib fixation and hernia reduction [5,6,10,16]. Surgical intervention is indicated in large lung hernias, those that are incarcerated, irreducible, or causing pain and respiratory compromise [6]. Most patients were for conservative management, including chest drain insertion; however, this was in the context of haemothorax and pneumothorax. Some cases of those under conservative management were shown to resolve spontaneously on serial CTs [12,13].

Conclusions
Lung herniation remains a rare complication of CPR. A high index of clinical suspicion should be present in those who underwent an extended period of CPR and in the frail with underlying health conditions. CT is the best modality for diagnosing lung herniation and has been shown to have the highest detection rate for CPRrelated injuries. Given the emphasis on high-quality CPR and the use of mechanical chest compression devices in an aging population, clinicians need to be aware of this rare event, as timely recognition and management may improve survival.

Additional Information Disclosures
Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.