Dekker introduced a method for analyzing plethysmographic signals to identify heart rate variability parameters linked to respiration rate, leading to an improved pulse oximeter functionality for noninvasive respiration rate monitoring. His development of an apparatus resulted in an approved patent for monitoring secondary physiological processes by analyzing optical signal variations. He then presented a method utilizing photoplethysmography to gather physiological parameters, involving filtering and analyzing pleth signals to identify components of interest for determining respiratory parameters.