PRC Breathing Mechanics & Diaphragm Function 2 — Questions and Answers
Question 1: In the Postural Restoration Institute (PRI) model, the right hemidiaphragm is considered more dominant than the left primarily because of its anatomical relationship with which structure?
- The right lung lobe
- The liver providing a stable base (Correct answer)
- The right atrium of the heart
- The inferior vena cava
Correct answer: The liver providing a stable base
The liver sits beneath the right hemidiaphragm, providing a solid dome-shaped base that makes the right side mechanically more advantageous and dominant in most individuals.
Question 2: Which phase of the breathing cycle is most associated with spinal extension and posterior rib cage expansion in PRI?
- Forced expiration
- Inhalation (Correct answer)
- Exhalation
- The apneic pause
Correct answer: Inhalation
During inhalation the diaphragm descends, the rib cage lifts and expands posteriorly, and the thoracic spine moves into relative extension.
Question 3: A patient is unable to achieve a zone of apposition (ZOA) on the left side. Which compensatory breathing pattern is most likely observed?
- Paradoxical abdominal breathing
- Dominant left accessory muscle use with elevated left shoulder girdle (Correct answer)
- Increased nasal breathing with mouth closed
- Diaphragmatic breathing with equal bilateral expansion
Correct answer: Dominant left accessory muscle use with elevated left shoulder girdle
Loss of left ZOA leads to recruitment of accessory muscles on the left (scalenes, upper trapezius) and elevation of the left shoulder girdle as the patient tries to expand the left thorax.
Question 4: The zone of apposition (ZOA) of the diaphragm is best described as the region where the diaphragm:
- Attaches to the lumbar vertebrae via the crura
- Apposes the inner surface of the lower rib cage (Correct answer)
- Intersects the esophageal hiatus
- Contacts the pericardium superiorly
Correct answer: Apposes the inner surface of the lower rib cage
The ZOA is the cylindrical portion of the diaphragm that lies in direct apposition against the inner aspect of the lower six ribs, allowing it to generate lateral and superior rib expansion with contraction.
Question 5: During a 90-90 hip lift with balloon exercise in PRI, the balloon serves primarily to:
- Strengthen the serratus anterior directly
- Provide resistance that facilitates left ZOA and diaphragm repositioning (Correct answer)
- Increase tidal volume through load training
- Stretch the posterior hip capsule
Correct answer: Provide resistance that facilitates left ZOA and diaphragm repositioning
Blowing into the balloon on exhalation creates back-pressure that assists in repositioning the left hemidiaphragm by promoting left ZOA and left thoracic expansion.
Question 6: Which abdominal muscle is most critical in PRI for maintaining a proper exhalation position and supporting the diaphragm's ZOA?
- Rectus abdominis
- External oblique (Correct answer)
- Transverse abdominis
- Internal oblique
Correct answer: External oblique
The external oblique, when active, depresses the anterior rib cage and supports the lower abdominal wall, facilitating a proper exhalation position that maintains the diaphragm's ZOA.
Question 7: In a patient with a left AIC pattern, the left hemidiaphragm is typically found in which positional state?
- Fully descended and flat
- Elevated and in a shortened position (Correct answer)
- Neutral and symmetrical with the right
- Depressed inferiorly due to stomach gas
Correct answer: Elevated and in a shortened position
In the left AIC pattern the left hemidiaphragm is typically elevated and shortened, having lost its normal dome shape and ZOA, contributing to impaired left-side breathing mechanics.
PRC Breathing Mechanics & Diaphragm Function 2
In the Postural Restoration Institute (PRI) model, the right hemidiaphragm is considered more dominant than the left primarily because of its anatomical relationship with which structure?