Final answer:
Air in the dialyzer would adversely affect clearance during dialysis by disrupting the diffusion of wastes like urea from the blood into the dialysate, making dialysis less effective.
Step-by-step explanation:
The question asked about factors that would adversely affect clearance during dialysis. An increase in blood flow rate would typically improve the efficiency of waste removal by increasing the contact between blood and the dialysate across the semipermeable membrane. However air in the dialyzer would indeed adversely affect clearance because it disrupts the normal diffusion process required for the transfer of substances like urea from the blood into the dialysate. The presence of air could create air locks or reduce the contact area available for diffusion, thereby lowering the effectiveness of dialysis by preventing optimal waste removal from the blood.