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Quantification of thoracic volumes by three-dimensional imaging.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 1, 1987
Summary
Anesthesia-paralysis reduces thoracic cavity volume and functional residual capacity in humans. Rib cage and diaphragm changes, along with increased trapped gas, contribute to these significant respiratory changes.
Area of Science:
- Physiology
- Respiratory Medicine
- Anesthesiology
Background:
- Functional residual capacity (FRC) is crucial for maintaining lung function.
- Understanding volume changes in the thoracic cavity during anesthesia is vital for patient safety.
Purpose of the Study:
- To quantify changes in end-expiratory thoracic cavity volume (Vthx) and FRC after anesthesia-paralysis.
- To determine the contributions of rib cage and diaphragm movements to these volume changes.
Main Methods:
- Three-dimensional X-ray computed tomography (Dynamic Spatial Reconstructor) measured Vthx.
- Nitrogen clearance determined untrapped end-expiratory pulmonary gas volume at FRC.
- Measurements were taken before and after anesthesia-paralysis induction in eight supine volunteers.
Main Results:
- Anesthesia-paralysis significantly reduced Vthx (0.28 L) and FRC (0.59 L).
- The reduction in FRC exceeded the reduction in Vthx in most subjects, suggesting increased intrathoracic fluid or trapped gas.
- Rib cage volume changes significantly contributed to Vthx reduction, while diaphragm changes had a variable contribution.
Conclusions:
- Anesthesia-paralysis induces significant reductions in thoracic cavity volume and FRC.
- Rib cage, diaphragm, and trapped gas volume changes collectively contribute to FRC reduction.
- Individual subject variability exists in the relative contributions of these factors.