 Blood can usually be detected in the trachea or bronchi for 1–3 days after an episode of EIPH, but may be present for up to a week.The amount of blood visible in the trachea at the time of examination is most commonly graded on a scale of 0 (no blood) to 4 (airways awash with blood).In some mildly-affected horses, endoscopy must be performed on multiple occasions to confirm a diagnosis of EIPH.