PRC Breathing Mechanics & Diaphragm Function 3 — Questions and Answers
Question 1: Which statement best explains why PRI emphasizes exhalation techniques before assessing or correcting postural patterns?
- Exhalation relaxes the paraspinal muscles only
- Full exhalation repositions the diaphragm inferiorly and restores ZOA, making the patient receptive to repositioning (Correct answer)
- Inhalation causes rib flare which blocks correction
- Exhalation eliminates CO2 buildup that causes spasm
Correct answer: Full exhalation repositions the diaphragm inferiorly and restores ZOA, making the patient receptive to repositioning
Achieving a full exhalation restores the diaphragm to a properly domed position with adequate ZOA, which is a prerequisite for effective postural repositioning in PRI.
Question 2: The right crural attachment of the diaphragm to the lumbar spine primarily influences which lumbar segment most directly?
- L1-L2
- L2-L4 (Correct answer)
- L4-S1
- T12 only
Correct answer: L2-L4
The right crus of the diaphragm attaches to the anterior bodies of L2-L4 vertebrae, making those segments most directly influenced by diaphragm tension and positioning.
Question 3: A PRI clinician assesses a patient's breathing and notes that the lower ribs flare outward bilaterally during inhalation instead of expanding laterally. This most likely indicates:
- Optimal diaphragm function with wide ZOA
- Loss of ZOA with diaphragm acting as a flat piston rather than a dome (Correct answer)
- Excessive lung compliance reducing rib excursion
- Hypertonicity of the intercostal muscles
Correct answer: Loss of ZOA with diaphragm acting as a flat piston rather than a dome
When the diaphragm loses its ZOA and domed shape it can only pull the ribs outward (bucket-handle flare) rather than lifting them in the optimal lateral and superior direction.
Question 4: In PRI, which muscle pairing is most responsible for creating intra-abdominal pressure that assists diaphragmatic descent during inhalation?
- Psoas and iliacus
- Transverse abdominis and pelvic floor (Correct answer)
- Rectus abdominis and quadratus lumborum
- Internal oblique and erector spinae
Correct answer: Transverse abdominis and pelvic floor
Co-activation of the transverse abdominis and pelvic floor generates intra-abdominal pressure that resists and modulates diaphragmatic descent, providing the diaphragm a stable base to work against.
Question 5: During normal quiet breathing, what percentage of the total respiratory muscle work is attributed to the diaphragm in healthy adults?
- About 20-30%
- About 50-60%
- About 70-80% (Correct answer)
- About 95-100%
Correct answer: About 70-80%
In healthy adults during quiet breathing, the diaphragm accounts for approximately 70-80% of total ventilatory work, with accessory muscles contributing minimally.
Question 6: Which of the following describes the 'pump handle' rib motion that occurs predominantly in the upper ribs during inhalation?
- Ribs rotate downward and laterally
- Ribs rotate upward and anteriorly increasing the AP diameter of the chest (Correct answer)
- Ribs move laterally only, increasing transverse diameter
- Ribs move inferiorly compressing the abdominal contents
Correct answer: Ribs rotate upward and anteriorly increasing the AP diameter of the chest
Pump handle motion describes upper rib rotation upward and anteriorly around a roughly coronal axis, primarily increasing the anterior-posterior diameter of the thorax during inhalation.
Question 7: In the PRI framework, what is the primary consequence of an over-inflated thorax (air trapping) on diaphragm mechanics?
- The diaphragm becomes hyperresponsive and hypertrophies
- The diaphragm is pushed into a flat position, reducing its dome and ZOA (Correct answer)
- The accessory muscles are inhibited by increased lung volume
- The crura shorten and pull the lumbar spine into flexion
Correct answer: The diaphragm is pushed into a flat position, reducing its dome and ZOA
Chronic air trapping pushes the diaphragm downward into a flattened position, eliminating its normal dome shape and ZOA, severely reducing its mechanical advantage.
PRC Breathing Mechanics & Diaphragm Function 3
Which statement best explains why PRI emphasizes exhalation techniques before assessing or correcting postural patterns?