Neck and abdominal muscle activity during a sniff

Area of Science:

• Respiratory Physiology
• Neuromuscular Function

Background:

• Sniff nasal inspiratory pressure (SNIP) is a common, non-invasive measure of global respiratory muscle strength.
• The specific contribution of non-diaphragmatic accessory muscles to SNIP generation is not well understood.
• Understanding accessory muscle recruitment during SNIP is crucial for accurate clinical interpretation.

Purpose of the Study:

• To investigate the electromyographic (EMG) activity of specific neck and abdominal accessory muscles during SNIP.
• To determine the relative activation patterns of scalene, sternocleidomastoid, trapezius, and transversus abdominis muscles during a sniff maneuver.

Main Methods:

• Fine-wire EMG electrodes were implanted into scalene, sternocleidomastoid, trapezius, and transversus abdominis muscles in seven healthy young adults.
• Subjects performed short, sharp sniffs of varying intensity in both standing and supine positions while SNIP was measured.
• EMG activity was recorded and analyzed in relation to SNIP intensity.

Main Results:

• Scalene muscle activity was consistently present and increased linearly with SNIP intensity across all subjects.
• Sternocleidomastoid activity was observed in some subjects at higher SNIP levels.
• Trapezius and transversus abdominis muscles showed minimal or inconsistent activity, even at maximal SNIP.

Conclusions:

• There is differential activation of accessory respiratory muscles during SNIP.
• Scalene muscles play a significant role in SNIP generation, whereas trapezius and abdominal muscles contribute less.
• The unequal contribution of accessory muscles implies that SNIP measurements may be disproportionately affected by the dysfunction of specific respiratory muscles.