Hold that thought…will continue later…
Chest wall compliance and breathing.
Conclusions: The results of this review indicated that the sitting position improved the rib-cage compartment of the chest wall, whereas the supine position resulted in the superior enhancement in the part of the abdomen relative to other body positions. These changes in the body position could have some effect on the movements of the rib cage and abdomen and the variations in lung volumes, which need to be interpreted with caution when considering implementation in the clinical setting. Respir Care . 2018 Nov;63(11):1439-1451. doi: 10.4187/respcare.06344.Epub 2018 Oct 16. Which Body Position Is the Best for Chest Wall Motion in Healthy Adults? A Meta-Analysis Rattanaporn Sonpeayung 1, Anong Tantisuwat 1, Thaniya Klinsophon 1, Premtip Thaveeratitham
Chest wall and pulmonary compliance were measured in 42 normal males aged 24—78 years. Measurements were made using the static method and the positive-pressure breathing method of Heaf and Prime. Chest wall compliance decreased significantly with age. Pulmonary compliance measured at functional residual capacity was similar in old and young subjects. As lung volume increased pulmonary compliance decreased more in the young than in the old. The latter age difference may result from a loss of lung elastic recoil in the elderly or may be due totally to the age difference in chest wall compliance. The observed age differences in lung compartment volumes can largely be accounted for by the decrease in chest wall compliance.
aging; chest wall compliance; lung compliance; static measurement of compliance; positive-pressure measurement of compliance; lung volumes; residual volume Relationship between chest wall and pulmonary compliance and age Charles Mittman, Norman H. Edelman, Arthur H. Norris, and Nathan W. Shock01 NOV 1965https://doi.org/10.1152/jappl.1918.104.22.1681 Submitted on July 17, 1964 Chest wall compliance: Calculation
Chest wall compliance is the opposite of elasticity, and elasticity is the tendency of lung tissue to return to its original (or relaxed) position after an applied force has been removed. Compliance is essentially the ability of the lung tissue to “absorb” the same applied force, which generally results from a change in intrathoracic pressure.
Chest wall compliance can be calculated by this formula:
Compliance = Δ V / Δ P
Where change in volume is in liters and change in pressure is in cm H20.
There are two different types of compliance: static and dynamic. Static compliance is a measured during plateau (rather than peak inspiratory) pressure. PEEP should be subtracted from plateau inspiratory pressure in making this calculation. Because the pressure-volume curve (see below) is not linear during inspiration and expiration due to changes in the lung tissue, Dynamic compliance varies and is a calculated with a measurement of tidal volume at a given intrathoracic pressure during which there is airflow through the lungs at any point during inspiration or expiration.
Lungs with low compliance are stiff lungs and will require much greater pressure to reach a given volume compared to lungs that have high compliance. There are several factors that affect lung compliance including alterations in the ribs (ie. fractures), ossification of the costal cartilage, obesity, muscular or neural changes to intercostal muscles (ie. paralysis or strain/pain), position (prone/supine), structural abnormalities (ie. kyphosis or scoliosis), increased intraabdominal pressure, and age.
Normal chest wall compliance in adults is approximately 100-200ml/cm H2O. However, children have far lower chest wall compliance at 2.5-5.0ml/cm H2O.
Another way to determine chest wall compliance is graphically using a pressure volume curve. The slope of the line in the is equal to the lung compliance. https://www.openanesthesia.org/chest_wall_compliance_calculation/