Detecting unilateral phrenic paralysis by acoustic respiratory analysis

Area of Science:

• Pulmonology
• Respiratory Physiology
• Medical Acoustics

Background:

• Unilateral phrenic nerve paralysis significantly impacts respiratory function, with consequences ranging from mild impairment to severe dysfunction.
• Assessing respiratory muscle function, particularly in cases of unilateral phrenic paralysis, often requires invasive methods or indirect evaluations.
• Lung sound intensity (LSI) analysis offers a potential non-invasive approach to indirectly evaluate respiratory muscle activity by comparing thoracic cage sides.

Purpose of the Study:

• To investigate the utility of acoustic analysis of lung sound intensity (LSI) as a non-invasive method for assessing respiratory function in patients with unilateral phrenic paralysis.
• To compare LSI measurements between the affected and unaffected sides in patients with unilateral phrenic paralysis and contrast these with measurements in healthy individuals.
• To explore the relationship between LSI, airflow, and pulmonary function parameters like FEV1 in the context of unilateral phrenic paralysis.

Main Methods:

• Lung sounds and airflow were recorded in ten males with unilateral phrenic paralysis and ten healthy subjects during progressive airflow maneuvers.
• Two acoustic sensors were placed on the subjects' backs, on the left and right sides, to capture lung sounds.
• Lung sound intensity (LSI) was calculated within a specific frequency range (70–2000 Hz) and airflow range (1.2–2.4 L/s).

Main Results:

• Significantly lower LSI was observed on the paralyzed side (5.7±3.5 dB) compared to the normal side (19.3±4.0 dB) in patients (p=0.0002).
• Healthy subjects exhibited similar LSI between left (15.1±6.3 dB) and right (17.4±5.7 dB) sides (p=0.2730).
• A positive linear relationship between LSI and airflow was found, with patients showing a shallower slope (approx. 5 dB/L/s) than healthy subjects (approx. 10 dB/L/s). LSI on the affected side correlated with FEV1, being lower in patients with reduced FEV1.

Conclusions:

• Acoustic analysis of LSI is a relevant and non-invasive technique for assessing respiratory function, particularly in unilateral phrenic paralysis.
• This method can effectively differentiate between the affected and unaffected sides of the thoracic cage, supporting the diagnosis of unilateral phrenic paralysis.
• LSI monitoring may enhance the reliability of diagnosis and facilitate the ongoing management of patients with unilateral phrenic paralysis.