In C4 Tetraplegia, which muscles are innervated and may be used for sip-and-puff powered mobility?

• A. Diaphragm, Trapezius, and Muscles of the Face/Neck
• B. Abdominals Only
• C. Gluteal Muscles
• D. Hip Flexors

Answer: (A)

In this situation, the ability to use sip-and-puff depends on preserving breath generation and the muscles that help control the mouthpiece and head/neck position. The diaphragm is the main muscle for inspiration and is typically intact with a C4 injury, so the person can create inhale and exhale signals to operate the device. The trapezius, as an accessory stabilizer for the neck and shoulders, helps maintain proper posture and head positioning, which improves the ability to bring air into the mouthpiece or direct it out, effectively triggering the switch. Muscles of the face and neck, supplied by cranial nerves, allow the lips and surrounding muscles to form a seal around the mouthpiece and help shape airflow during sip or puff.

Abdominal muscles, gluteal muscles, and hip flexors are controlled by lower spinal levels and are usually weak or paralyzed at this level, so they are not typically used to generate or modulate the breaths needed for sip-and-puff.