Platypnea-orthodeoxia syndrome (POS) is a rare and underdiagnosed clinical syndrome classically characterised by positional dyspnea (platypnea) and arterial oxygen desaturation (orthodeoxia) while upright, which improves in the supine position. There are no known cases of a POS variant where oxygenation improved during exercise and in the upright position, but worsened at rest and while supine. We present a novel case of a man in his mid-70s with symptoms and oxygen saturations paradoxical to classic POS, who was found to have a right-to-left shunt across a patent foramen ovale (PFO) with normal right atrial pressure (RAP), ascending aortic ectasia and concomitant right hemidiaphragm elevation without paralysis. On successful transcatheter PFO closure, no hypoxaemia was found in any position or exertional level. To that effect, this paradoxical variant may represent an under-recognised and underdiagnosed form of POS that warrants further investigation in patients with positional dyspnoea and hypoxaemia.

Thoracic ultrasound has attracted much interest in detecting pleural effusion or pulmonary consolidation after cardiac surgery. In 2016, Trovato reported, in the World Journal of Cardiology, the interest of using, in addition to echocardiography, thoracic ultrasound. In this editorial, we highlight the value of assessing diaphragm function after cardiac surgery and interventional cardiology procedures. Various factors are able to impair diaphragm function after such interventions. Diaphragm motion may be decreased by chest pain secondary to sternotomy, pleural effusion or impaired muscle function. Hemidiaphragmatic paralysis may be secondary to phrenic nerve damage complicating cardiac surgery or atrial fibrillation ablation. Diagnosis may be delayed. Indeed, respiratory troubles induced by diaphragm dysfunction are frequently attributed to pre-existing heart disease or pulmonary complications secondary to surgery. In addition, elevated hemidiaphragm secondary to diaphragm dysfunction is sometimes not observed on chest X-ray performed in supine position in the intensive care unit. Analysis of diaphragm function by ultrasound during the recovery period appears essential. Both hemidiaphragms can be studied by two complementary ultrasound methods. The mobility of each hemidiaphragms is measured by M-mode ultrasonography. In addition, recording the percentage of inspiratory thickening provides important information about the quality of muscle function. These two approaches make it possible to detect hemidiaphragm paralysis or dysfunction. Such a diagnosis is important because persistent diaphragm dysfunction after cardiac surgery has been shown to be associated with adverse respiratory outcome. Early respiratory physiotherapy is able to improve respiratory function through strengthening of the inspiratory muscles i.e. diaphragm and accessory inspiratory muscles.

Patent foramen ovale (PFO) is a congenital abnormality present in 25%-30% of healthy adults and rarely leads to any sequelae. ^{1 2} It is associated with a left-to-right shunt which usually does not lead to any haemodynamic compromise. Occasionally, the shunt can get reversed; that is, right-to-left shunt occurs due to worsening pulmonary hypertension and can lead to persistent hypoxia. It is rare for the shunt reversal to happen in the absence of pulmonary hypertension. Here, we present an exceedingly rare case in a 61-year-old man presenting with hypoxia, was found to have shunt reversal due to unilateral diaphragmatic paralysis. He was successfully treated with PFO closure. The purpose of this report is to consider rare possibilities of PFO shunt reversal when the right-sided heart pressure is normal and to highlight that a simple chest X-ray can be a clue to the diagnosis.