Correction at 4:34 , Beta blockers do not cause bronchoconstriction by their own, they just do not allow beta agonists to bind to receptors thereby leading to bronchoconstriction not getting relieved if at all an asthmatic experiences an acute attack of bronchoconstriction. Blockers do not have efficacy
Specifically non-selective beta blockers are absolute contraindications for asthmatic patients...if at all required we give beta 1 selective blockers...aur vo hum man ke to nahi chal sakte ki abhi acute attack nahi ayega...