This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anaesthesia
Most potent bronchodilator among inhalational anesthetic agents is 
Select and explain. 
A. Isoflurane, B. Sevoflurane, C. Halothane, D. Desflurane
C: Halothane
Answer: C: Halothane 
Explanation: Effect of inhalational agents on respiratory systemAll inhalational agents are bronchodilators -Halothane cause maximum bronchodilatation. The inhalational agent of choice in asthmatics (intravenous anaesthtic of choice is ketamine).All inhalational agents cause respiratory depression to some extent - Maximum depression of respiration is seen with enflurane, on the other hand, maximum inhibition of ventilator response to increased CO2 and hypoxia is caused by halothaneAll inhalational agents vasodilate pulmonary vascular bed by blunting the hypoxic pulmonary vasoconstriction (HPV) response. Halothane has maximum effect: Isoflurane, Enflurane, desflurane, sevoflurane have similar effect.(Refer: Morgan and Mikhail's Clinical Anaesthesiology, 5th edition, pg no. 167 - 169)