[Inspiratory phase angle behavior in oscilloresistometry]

Area of Science:

• Respiratory physiology
• Pulmonary mechanics

Context:

• Oscillatory measurements of lung resistance, including phase angle (PSI), offer insights into respiratory mechanics.
• Distinct PSI behaviors are observed during deep inspiration in pulmonary emphysema (unchanged) and pulmonary fibrosis (negativation).

Purpose:

• To investigate the relationship between phase angle (PSI) and transpulmonary pressure (Ptp) during breathing in various lung conditions.
• To explain the differing PSI findings in pulmonary emphysema and fibrosis.

Summary:

• Transpulmonary pressure (Ptp) was measured alongside PSI in 85 subjects. PSI-negativation occurred in 31/43 pulmonary fibrosis patients and 10/19 healthy subjects, unlike emphysema patients with stable PSI.
• Subjects with PSI-negativation exhibited higher Ptp at 100% total lung capacity (TLC), attributed to an overproportional pressure increase late in lung inflation.
• A modified approach is proposed, analyzing PSI-volume (PSI-V) dependence separately in breathing ranges (mid-75% vital capacity and 75%-100% vital capacity) for improved noninvasive lung compliance assessment.

Impact:

• This study enhances the noninvasive assessment of lung compliance by refining PSI-V dependence analysis.
• Findings suggest PSI variations are influenced by heart rhythm and intrathoracic blood volume, offering further diagnostic potential.