Smartphone aiding in analysis of Hamman’s sign

Abstract

Hamman’s sign refers to an unusual click that occurs in synchrony with heart sounds, and is pathognomonic for left-sided pneumothorax and spontaneous mediastinum. In this case, a 17-year-old man living in a rural area used his smartphone to record an audible clicking sound emanating from his thorax. This occurred following coughing episodes secondary to an upper respiratory tract infection. Initially, this prompted a request for an echocardiogram to exclude structural cardiac anomalies; however, Hamman’s sign was also considered. This facilitated the timely diagnosis of pneumothorax to be made via a simple chest radiograph, one of the only imaging modalities available at the patient’s rural health service. To promote awareness of this rare clinical phenomenon, this report also presents the patient’s own sound recording of Hamman’s sign and corresponding chest radiographs.

Background

In 1937, Louis Hamman described a characteristic clicking, crunching or popping praecordial sound that occurred in synchrony with heart sounds, and varied with respiration.^{1 2} This phenomenon, eponymously referred to as Hamman’s sign, was traditionally indicative of spontaneous pneumomediastinum. However, reports have further detailed that its presence can also be pathognomonic for spontaneous left-sided pneumothorax.^3–7

This report emphasises the important role of thorough physical examination in the diagnostic process by providing evidence of this rare sign in a young patient who complained of a loud clicking sound coming from his chest. Recognition of Hamman’s sign ensured that appropriate cost-effective investigations were organised, enabling the diagnosis of a spontaneous left-sided pneumothorax to be made in a timely manner. In addition, based on a review of previously published reports, this appears to be the first documented case whereby the use of smartphone technology has aided in the identification of Hamman’s sign.

Case presentation

A 17-year-old apprentice electrician from a rural town presented to his local health service with a 2-day history of a clicking sound emanating from his chest and associated mild, left-sided, pleuritic chest pain. He had no significant personal or family medical history. For the preceding week, he had been experiencing coryzal symptoms and paroxysmal coughing fits. This was attributed to a viral upper respiratory tract infection, for which he had not sought medical attention. The patient believed the new clicking sound originated from his heart, and noted that it was louder on inspiration and when lying in the left lateral position. It was audible to the patient’s friends and family from a distance, such that the patient was able to record the sound on his smartphone (online supplementary audio 1). The patient had never before experienced a similar constellation of symptoms.

On examination, the patient appeared well and had a lean body habitus (height 175 cm, weight 57 kg, body mass index 18.6). There were no clinical features of Marfan’s syndrome. He was haemodynamically normal, with no oxygen requirement and no evidence of respiratory distress. Ear, nose and throat examination was unremarkable apart from mild tonsillar and oropharyngeal inflammation. The most pertinent examination finding was a click originating from the patient’s chest that could be heard even without a stethoscope. Praecordial auscultation revealed that it occurred consistently in mid-systole rather than with respiration, and was most prominent in the left axillary area. Posteriorly, the patient’s chest was clear with nil apparent zones of reduced air entry.

The staff at the patient’s local health service sought cardiology advice from a nearby tertiary hospital, initially considering that the clicking sound was secondary to cardiovascular pathology due to its relationship with heart sounds. Initially, an echocardiogram was requested to exclude structural heart disease or valvular abnormalities, in particular mitral valve prolapse. After listening to the patient’s smartphone recording and further enquiring into the specific characteristics of the clicking sound, the cardiology team noted the clicking sound appeared consistent with Hamman’s sign.

Investigations

A simple chest radiograph at the patient’s local health service was organised as a first-line investigation. This demonstrated a small left apical pneumothorax (figure 1). Routine blood tests and an ECG were also performed, all of which were unremarkable.

Figure 1.

Chest radiograph at time of presentation demonstrating a small left apical pneumothorax.

Outcome and follow-up

Once it was evident that the patient’s presentation was due to a small spontaneous pneumothorax, the patient was able to be discharged home for conservative management. Weekly chest radiographs were performed to assess progress. During the 2-week period following diagnosis, the patient’s symptoms gradually improved until total resolution occurred. At this point, there was also no further radiological evidence of pneumothorax, and the clicking sound was no longer audible (figure 2).

Figure 2.

Chest radiograph 2 weeks following presentation demonstrating resolution of the pneumothorax. At this point, the clicking sound was no longer audible.

Given the peculiarity of the case, the patient’s family remained anxious that the clicking sound could have been due to an underlying cardiac pathology. Subsequently, an outpatient echocardiogram was also performed. It was a normal study with an ejection fraction of 55%, with no identifiable structural or valvular disease. The patient and his family were then reassured that the sound was evidence of Hamman’s sign, and attributable to the small left-sided pneumothorax.

Discussion

Hamman’s sign is traditionally associated with the presence of pneumomediastinum, though its association with left-sided pneumothorax should also be emphasised. General consensus is that the curious sounds of Hamman’s sign are caused by movement of extrapulmonary air being pulsed by ventricular contraction during the cardiac cycle.^{1 5 7} It has also been proposed that it may be due to free pleural air being channelled through pulmonary fissures.⁶ Scadding and Wood reported four cases of Hamman’s sign in 1939, each of which were associated with a shallow, left-sided, spontaneous pneumothorax. Similar to this case, the patients were young males of lean body habitus with systolic clicking or tapping sounds on auscultation that were prominent on inspiration.³ In 1955, Chapman also proposed that Hamman’s sign is in fact caused by pneumothorax, that either coexists with pneumomediastinum or is present alone.⁴ A further series from 1969 detailed five cases of left-sided pneumothorax and extracardiac clicking sounds. They noted interpatient variability in regards to the frequency, intensity and timing of the clicking sound in relation to the cardiac cycle, respiration and patient position.⁵ Thorough physical examination plays a crucial role in the diagnostic process, especially in areas where there are limited pathological testing facilities and medical imaging modalities. Small pneumothoraces may present a diagnostic challenge, especially if the patient appears clinically well and there is minimal radiological evidence of the diagnosis. Although Hamman’s sign is rare, its presence alone should immediately raise suspicion of an underlying small left-sided pneumothorax, or pneumomediastinum.

Moreover, smartphones are undeniably playing an increasing role in the clinical practice of a variety of medical specialties. They enable patients to easily keep a photographic or audiovisual recording of clinical signs, and can document transient clinical signs that may not always be apparent during the doctor–patient encounter to aid in diagnosis. In addition, patients can also further engage in their healthcare through novel medical mobile applications. With advances in these technologies, a 2016 study demonstrated that smartphone-based microscopy (achieved via construction of a 3 mm ball camera lens attachment) performed excellently for the cost-effective diagnosis of non-melanoma skin cancers when compared with the gold standard of light microscopy.⁸ In this case, it was the ability of the smartphone to record and share the clinical sign with others that assisted in the correct diagnosis being made. By having quick access to the patient’s simple recording of the clicking sound, the consulting cardiology team from the tertiary hospital were able to more easily recognise Hamman’s sign. A simple chest radiograph was the only essential investigation required to confirm diagnosis, and was able to be performed at the patient’s local rural health service. This subsequently avoided an unnecessary inter-hospital transfer, an endeavour that uses substantial health resources and can be disruptive for the patient and their family.

Patient’s perspective.

I had been feeling sick for about a week, just with a runny nose and sore throat. I had also been coughing heaps but did not bother going to the doctor because I thought it was just a cold. A few days later, I started to notice this weird click coming out of my chest while I was at work, and I had also gotten a mild sharp pain on the left side of my chest. It was all made worse when breathing in and when I was lying on my left side to go to sleep. I was not too concerned though. My friends did not believe me at first when I said my chest was clicking, but I recorded it on my phone and sent it to them. They all came around to hear it in person because it was so strange, and eventually them and my mum convinced me to go see a doctor because they thought it was something wrong with my heart. When the doctor listened to my chest they said that the click was in time with my heartbeat, so they asked one of the bigger hospitals for advice. They sent them the recording I had made because the other doctors obviously were not able to hear the sound in person. Luckily after hearing the recording, the other doctors thought it might not be related to my heart at all. They told my doctor to just start with a chest X-ray, and it showed the pneumothorax. I was super relieved, because it meant I could stay at home and just go see my local doctor. It saved my family a lot of time and money not having to go to the bigger hospital for more tests. My symptoms started going away within a few days anyway and the click kept getting quieter until I could not hear it at all. After a fortnight, the doctor said they could not see the pneumothorax on my chest X-ray anymore and that everything was back to normal. I am glad I have kept the recording of the sound though, because lots of doctors at the health service have been asking to hear it so they know what to look out for if another patient comes in with the same thing. I hope that it can help someone else.

Learning points.

• Thorough physical examination plays a crucial role in the diagnostic process.

• Hamman’s sign is a rare phenomenon entailing a clicking, crunching or popping praecordial sound from the chest that occurs with heart sounds.

• The presence of Hamman’s sign should immediately prompt consideration of left-sided pneumothorax and pneumomediastinum as differential diagnoses.

• Smartphones can be a valuable tool for patients to document and monitor progress of clinical signs. Files can be easily shared among clinicians for assistance with diagnosis and management, and for learning purposes.