"ipsilateral hyper-expansion and splayed ribs"
"In addition to the sonographic features of pneumothorax, a RUSH exam (often performed in the setting of haemodynamic instability) the following features imply the presence of tension physiology 8:"
"This contrasts with the features of tension pneumothorax occurring in patients receiving positive pressure ventilation. These patients suddenly deteriorate; the first signs are hypoxaemia and hypotension, and this can progress to cardiac arrest within minutes 5,14."
"A one-way valve mechanism is often cited as the underlying lesion for tension pneumothorax. This is likely to be the case for all pneumothoraces; there is no evidence that gas can re-enter the lung from the pleural cavity 13. The size of a pneumothorax depends on the size and persistence of the visceral pleural defect. Gas enters the pleural space during inspiration and cannot escape, causing atelectasis of the lung with hypoxaemia due to shunting, and decreased ventilatory capacity. If the patient is receiving positive pressure ventilation, venous return is obstructed leading to circulatory collapse."
"There are two distinct scenarios."