title: Adaptation of respiratory muscle perfusion during exercise to chronically elevated ventilatory work.
abstract: Pneumonectomy (PNX) leads to chronic asymmetric ventilatory loading of respiratory muscles (RM). We measured RM energy requirements during exercise from RM blood flow (Q) using a fluorescent microsphere technique in dogs that had undergone right PNX as adults (adult R-PNX) or as puppies (puppy R-PNX), compared with dogs subjected to right thoracotomy without PNX as puppies (Sham) and to left PNX as adults (adult L-PNX). Ventilatory work (W) was measured during exercise. RM weight was determined post mortem. After adult and puppy R-PNX, the right hemidiaphragm becomes grossly distorted, but W and right costal muscle mass increased only after adult R-PNX. After adult L-PNX, the diaphragm was undistorted; W and left hemidiaphragm RM Q were elevated, but muscle mass did not increase. Mass of parasternal muscle did not increase after adult R-PNX, despite increased Q. Thus muscle mass increased only in response to the combination of chronic stretch and dynamic loading. There was a dorsal-to-ventral gradient of increasing Q within the diaphragm, but the distribution was unaffected by anatomic distortion, hypertrophy, or workload, suggesting a fixed pattern of neural activation. The diaphragm and parasternals were the primary muscles compensating for the asymmetric loading from PNX.
authors.affiliation: Department of Medicine, University of Texas Southwestern Medical School, Dallas, Texas 75390-9034, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Hsia
authors.forename: S I
authors.initials: SI
authors.lastname: Takeda
authors.forename: E Y
authors.initials: EY
authors.lastname: Wu
authors.forename: R W
authors.initials: RW
authors.lastname: Glenny
authors.forename: R L
authors.initials: RL
authors.lastname: Johnson
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000367:Age Factors; D000403:Airway Resistance / Q000502:physiology; D000818:Animals; D003964:Diaphragm / Q000098:blood supply* / Q000473:pathology / Q000502:physiology*; D004285:Dogs; D006984:Hypertrophy; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000502:physiology; D009929:Organ Size; D005082:Physical Exertion / Q000502:physiology*; D011013:Pneumonectomy; D012039:Regional Blood Flow / Q000502:physiology; D014939:Work of Breathing / Q000502:physiology*