Evaluate the combinations of compliance and resistance and select the combination that will cause the lungs to empty slowest

a. CS = 0.05 L/cm H2O Raw = 2 cm H2O/(L/sec)
b. CS = 0.05 L/cm H2O Raw = 6 cm H2O/(L/sec)
c. CS = 0.03 L/cm H2O Raw = 5 cm H2O/(L/sec)
d. CS = 0.03 L/cm H2O Raw = 8 cm H2O/(L/sec)

ANS: B
Use the time constant formula, TC = C ? R, to determine the time constant for each choice. The combination with the longest time constant will empty the slowest. The time constant for A is 0.1 second, B is 0.3 second, C is 0.15 second, and D is 0.24 second. To find out how many seconds for emptying, multiply the time constant by 5.