Scott W. Lee, MD, Saima Sajid, MD, and Michelle Cao, MD, of Loma Linda University Medical Center in Loma Linda, California, have reported two case studies on square-wave and dual-wave bolusing.

In the first, M.M. had been diagnosed with gastroparesis (a disorder where the stomach takes too long to empty its contents—most often a complication of type 1 diabetes). After switching from multiple daily injections to pump therapy, she experienced fewer episodes of low blood glucose, but she still struggled with variability in her after-meal blood glucose.

According to the researchers, "M.M. would become hypoglycemic after her initial insulin bolus and then several hours later she would become hyperglycemic [as her food was slowly digested]. Because of her gastroparesis, she would also eat slowly, often taking over two hours."

When M.M. began giving herself a square-wave bolus using Humalog—administered over two hours instead of immediately with her meal—her after-meal glucose control improved substantially. To fine-tune the dosage amount and the timing of the square-wave bolus, she checked her glucose levels frequently and experimented with the same meal several times.

The researchers note: "M.M. found she was not experiencing hypoglycemia, since the administered insulin was spread over two hours. Furthermore, a reduction in her [after-meal] hyperglycemia followed as well." They conclude that the square-wave bolus is particularly useful for people with gastroparesis.

In the second case study, even though R.W.'s basal rates seemed to be set correctly on his insulin pump, he would occasionally awaken with high fasting blood-glucose levels—sometimes over 180 mg/dl. This elevation seemed to occur only after he had eaten a high-fat dinner the night before.

R.W. wore the Medtronic MiniMed continuous glucose monitoring system (CGMS), which recorded his blood glucose every five minutes. Data gathered by the monitoring system revealed that his glucose levels slowly began to rise several hours after he ate a high-fat meal such as pizza. This elevation persisted throughout the night and affected his glucose levels the next morning.

R.W. then began using a dual-wave bolus with NovoLog with such meals, delivering one dose of insulin immediately and a second over several hours. A repeat CGMS test revealed dramatic improvements in nighttime glucose control after eating high-fat meals. Fasting glucose levels also fell back into his goal range (90 to 120 mg/dl).

"The [insulin pump's] dual-wave bolus feature is an effective means for addressing glycemic control in type 1 diabetes," write the researchers, "particularly for those foods higher in fat."