Primary respiratory mechanism

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Notes

Osteopathic cranial manipulative medicine

Primary respiratory mechanism

“The primary respiratory mechanism (PRM) is a functional unit based on the accommodative actions of cranial articular surfaces" (Seffinger).
  • "Primary" precedes thoracic respiration in importance in the maintenance of life
  • "Respiratory" refers to the exchanges of gases and metabolites at the cellular level
  • "Mechanism" implies an integrated machine where each part works in relation to the others
PRM has five distinct anatomic-physiologic components:
  1. The inherent rhythmic motion of the brain and spinal cord
  2. Fluctuation of cerebrospinal fluid
  3. Mobility of intracranial and intraspinal membranes
  4. Articular mobility of cranial bones
  5. Involuntary mobility of the sacrum between the ilia
BODY MOTION DURING PRM PHASES
PRM PHASESBS*MIDLINE BONESPAIRED BONESSACRUMTHORACIC RESPIRATION PHASE
Flexion
Superior movement
FlexionExternal rotationCounter-nutation (extension)Inhalation
Extension
Inferior movementExtensionInternal rotationNutation (flexion)Exhalation

* SBS = Sphenobasilar synchondrosis

See the “Diagnosing cranial somatic dysfunction” learn page for more information on palpating the movements during the flexion and extension phases of the PRM.
Author: Arman Israelyan, OMS-III
Editor: Matt Lipinski, DO
Editor: Robyn Hughes, MScBMC

Summary

The primary respiratory mechanism (PRM) has two alternating phases, referred to as inhalation and exhalation phases. PRM is perceptible throughout the body, and its action is part of the normal physiology of the living human body. Five anatomic-physiologic phenomena function together as the PRM mechanism. These are: The inherent rhythmic motion of the brain and spinal cord Fluctuation of cerebrospinal fluid Mobility of intracranial and intraspinal membranes Articular mobility of cranial bones Involuntary mobility of the sacrum between the ilia