Thoracic ultrasound to differentially diagnose the cause of an opaque hemithorax (whiteout) when patients are referred for respiratory physiotherapy: A service evaluation
Authors: Hayward Simon , Hayward Lisa , Tait Chloe , Williams Nicola , Seddon David , Gidden Jemma 
Published: November 2022

Purpose An opaque hemithorax commonly termed a ‘whiteout’ on chest radiograph (CXR) often results in a referral for urgent respiratory physiotherapy. This referral assumes that sputum plugging of either main bronchus has resulted in a whole lung collapse. There are, however, many alternative causes of an opaque hemithorax that would not respond to physiotherapy treatment. Referring medical professionals often use the position of the mediastinum, or more specifically the trachea on CXR to identify the cause of an opaque hemithorax but this may not be a reliable method. Thoracic ultrasound (TUS) could be used to better differentiate between the pathologies causing an opaque hemithorax prior to any physiotherapeutic interventions. We predict that TUS is more accurate than CXR alone in assisting respiratory physiotherapists to differentiate between the pathological causes of an opaque hemithorax. Method This service evaluation was undertaken within the acute hospital setting and included all patients referred for chest physiotherapy that had presented with an opaque hemithorax on CXR within the six-month evaluation period. A member of the investigating team performed a TUS scan within an hour of the referral. A respiratory physiotherapy treatment was performed where clinically indicated or if not indicated the patient was referred back to the referring clinician. Data collected included: the side of the opaque hemithorax and direction of any tracheal shift; documented reason for referral to physiotherapy; TUS scan findings; final medical team findings and the patient’s treatment or management plan. Results A total of nine patients were included in this service evaluation within the 6-month evaluation period. Five of the referrals (56%) presented with ipsilateral shifts. The remaining CXRs showed the tracheas to be in a central position. None of the patients referred showed a contralateral shift. The main documented reason for a referral for respiratory physiotherapy in these nine cases was ‘sputum plugging’, ‘consolidation’ or ‘lung collapse’. The primary findings on TUS were pleural effusion (44%), atelectasis (22%), consolidation (22%) and empyema (11%). In four cases the TUS findings highlighted that respiratory physiotherapy treatments remained indicated. In five cases the TUS scans highlighted findings that were not immediately amenable to respiratory physiotherapy. At the time of writing eight of the patients had not survived to the end of the six-month evaluation period. Discussion No referral was received by physiotherapy to review a patient with a contralateral shift. This suggests that the referring clinicians are using the position of the trachea on CXR as a way to justify the need for a respiratory physiotherapy referral. The use of the position of the trachea on CXR to accurately determine pathology and clinically justify the need for a physiotherapy referral appears to be unreliable. In our evaluation, sputum plugging and pleural effusions have both caused ipsilateral and central tracheal positions. The use of physiotherapy-initiated TUS has allowed five patients to avoid receiving inappropriate treatments. Alternate medical techniques such as pleural drain insertion, advanced imaging and palliation were employed to manage the patient’s clinical condition. One aspect of this service evaluation that was not predicted prior to its commencement was the mortality rate in these nine patients. Eight of them did not survive to the end of the six-month data collection period. Physiotherapists can use TUS to more accurately identify the causes of an opaque hemithorax prior to the initiation of physiotherapy treatments or limit delays in alternative treatment when physiotherapy is not indicated.