Respiratory phase detection and delay determination for breath-by-breath analysis

Area of Science:

• Respiratory physiology
• Pulmonary function testing
• Biomedical engineering

Background:

• Accurate measurement of respiratory airflow and gas concentrations is crucial for pulmonary diagnostics.
• The time delay between these signals is typically assumed constant, but existing methods limit verification of this assumption.
• Uncertainty in this delay can lead to significant errors in respiratory analysis.

Purpose of the Study:

• To develop novel methods for precise respiratory phase detection and signal delay determination.
• To investigate the constancy of the airflow-gas concentration delay within and between breaths.
• To quantify the impact of delay uncertainty on respiratory measurements.

Main Methods:

• Developed a new algorithm for respiratory phase detection using bidirectional pneumotachographs with a volume criterion.
• Implemented a test gas injection method (low N2) to measure the delay between flow and gas concentration signals.
• Analyzed various breathing patterns to assess delay variations and their consequences.

Main Results:

• The new methods enabled accurate examination of delay variations.
• Investigation revealed that the impact of delay uncertainty on respiratory measurements is often underestimated.
• Significant variations in delay were observed across different breathing patterns.

Conclusions:

• The assumption of a constant delay between airflow and gas concentration signals is often invalid.
• Breath-by-breath determination of the signal delay is recommended to improve accuracy in respiratory analysis.
• The developed methods offer enhanced precision for studying respiratory dynamics.