Aging-related changes in respiratory system mechanics and morphometry in mice.
Previous work investigating respiratory system mechanics in mice has reported an aging-related increase in compliance and mean linear intercept (Lm). However, these changes were assessed using only a young (2-mo-old) and old (20- and 26-mo-old) group yet were interpreted to reflect a linear evolution across the life span. Therefore, to investigate respiratory system mechanics and lung morphometry across a more complete spectrum of ages, we utilized 2 (100% survival, n = 6)-, 6 (100% survival, n = 12)-, 18 (90% survival, n = 12)-, 24 (75% survival, n = 12)-, and 30 (25% survival, n = 12)-mo-old C57BL/6 mice. We found a nonlinear aging-related decrease in respiratory system resistance and increase in dynamic compliance and hysteresis between 2- and 24-mo-old mice. However, in 30-mo-old mice, respiratory system resistance increased, and dynamic compliance and hysteresis decreased relative to 24-mo-old mice. Respiratory system impedance spectra were measured between 1-20.5 Hz at positive end-expiratory pressures (PEEP) of 1, 3, 5, and 7 cmH2O. Respiratory system resistance and reactance at each level of PEEP were increased and decreased, respectively, only in 2-mo-old animals. No differences in the respiratory system impedance spectra were observed in 6-, 18-, 24-, and 30-mo-old mice. Additionally, lungs were fixed following tracheal instillation of 4% paraformaldehyde at 25 cmH2O and processed for Lm and airway collagen deposition. There was an aging-related increase in Lm consistent with emphysematous-like changes and no evidence of increased airway collagen deposition. Accordingly, we demonstrate nonlinear aging-related changes in lung mechanics and morphometry in C57BL/6 mice.
Mayo Clinic, Department of Physiology and Biomedical Engineering, Rochester, Minnesota;
Jonathan E
JE
Elliott
Mayo Clinic, Department of Physiology and Biomedical Engineering, Rochester, Minnesota; Mayo Clinic, Department of Anesthesiology, Rochester, Minnesota; and.
Carlos B
CB
Mantilla
Mayo Clinic, Department of Physiology and Biomedical Engineering, Rochester, Minnesota; Mayo Clinic, Department of Anesthesiology, Rochester, Minnesota; and.
Christina M
CM
Pabelick
Mayo Clinic, Department of Laboratory Medicine and Pathology, Rochester, Minnesota.
Anja C
AC
Roden
Mayo Clinic, Department of Physiology and Biomedical Engineering, Rochester, Minnesota; Mayo Clinic, Department of Anesthesiology, Rochester, Minnesota; and sieck.gary@mayo.edu.
Gary C
GC
Sieck
D000375:Aging; D000403:Airway Resistance; D000818:Animals; D008168:Lung / Q000473:pathology*; D008297:Male; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D011658:Pulmonary Fibrosis / Q000473:pathology; D012119:Respiration
compliance; mean linear intercept