The odd pulse, also known as the inspiratory stop pulse, is mainly caused by a decrease in left ventricular ejection, and the clinical manifestation of the pulse is significantly weakened or disappears during inspiration. In severe asthma attacks, the airway resistance increases significantly, causing the pressure in the alveoli to rise, and the negative pressure in the chest cavity to drop relatively during inspiration, causing the pulmonary vasculature to dilate, reducing pulmonary venous return, decreasing the amount of blood in the left atrium, and reducing the relative left ventricular ejection. If an odd pulse is present, the asthmatic patient is already very severe and at risk of death. The treatment is mainly symptomatic with airway diaphragms and anti-inflammatory drugs, and if the partial pressure of carbon dioxide is high, a ventilator may be required.