Calculate the inspiratory time necessary to ensure 98 of the ...

[craiczarry]

Calculate the inspiratory time necessary to ensure 98 of the volume is delivered to a patient with a Cs = 40 mL/cm H2O and the Raw = 1 cm H2O/(L/sec).
 
  a. 0.04 second
  b. 0.16 second
  c. 1.6 second
  d. 4.0 seconds

Question 2

The condition that is associated with an increase in airway resistance is which of the following?
 
  a. Pulmonary edema
  b. Bronchospasm
  c. Fibrosis
  d. Ascites

[medine]

Answer to Question 1

ANS: B
Time constant = C (L/cm H2O)  R (cm H2O/(L/sec)). 98 of the volume will be delivered in 4 time constants. Therefore, multiply 4 times the time constant.

Answer to Question 2

ANS: B
Airway resistance is determined by the gas viscosity, gas density, tubing length, airway diameter, and the flow rate of the gas through the tubing. The two factors that are most often subject to change are the airway diameter and the flow rate of the gas. The flow rate of the gas during me-chanical ventilation is controlled. Pulmonary edema is fluid accumulating in the alveoli and will cause a drop in the patient's lung compliance. Bronchospasm causes a narrowing of the airways and will, therefore, increase the airway resistance. Fibrosis causes an inability of the lungs to stretch, decreasing the patient's lung compliance. Ascites causes fluid buildup in the peritoneal cavity and increases tissue resistance, not airway resistance.