"Hanson's show tonight at Cains Ballroom in Tulsa, OK has been cancelled. Isaac is currently undergoing treatment and will be re-evaluated shortly by doctors. Further information about the tour will be made available at that time."

From Wikipedia: Pulmonary embolism (PE) is blockage of the pulmonary artery (or one of its branches), usually when a venous thrombus (blood clot from a vein), becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. This process is termed thromboembolism.