Respiratory mechanics in upper airway obstruction

Area of Science:

• Pulmonary Physiology
• Respiratory Medicine
• Medical Engineering

Background:

• Airway obstruction significantly impacts respiratory mechanics.
• Understanding flow-volume (V/V) and inspiratory/expiratory pressure-flow (IVPF) curves is crucial for diagnosing respiratory conditions.

Purpose of the Study:

• To investigate respiratory mechanics in patients with various upper airway obstructions.
• To analyze flow-volume and pressure-flow patterns in vocal cord paralysis, laryngeal/sublaryngeal obstruction, and tracheal obstruction.

Main Methods:

• Studied respiratory mechanics in 17 patients across three groups: vocal cord paralysis (A), laryngeal/sublaryngeal obstruction (B), and tracheal obstruction (C).
• Analyzed flow-volume (V/V) curves and inspiratory/expiratory pressure-flow (IVPF) curves, measuring parameters like forced inspiratory volume in 1 second (FIV1.0), peak inspiratory flow rate (PIFR), and expiratory flow rate (PEFR).

Main Results:

• Group A (vocal cord paralysis) exhibited reduced FIV1.0, PIFR, and VI50. All groups showed a flattened expiratory flow pattern and absence of the normal expiratory plateau.
• Group B (laryngeal/sublaryngeal obstruction) showed higher inspiratory resistance than expiratory resistance at high pressures (Palv > 50-60 cm H2O).
• The difference between PEFR and PIFR correlated inversely with obstruction severity, suggesting moderate sublaryngeal lesions can cause disproportionate inspiratory flow reduction.

Conclusions:

• The findings do not support the hypothesis that reduced tracheal caliber causes inspiratory flow decrease.
• Flow-volume and pressure-flow curve analysis effectively characterizes different types of upper airway obstruction.
• Surgical treatment outcomes were also discussed in relation to the observed respiratory mechanics.