Patricia Jones, age 50 years, was diagnosed with idiopathicpulmonary fibrosis (IPF) two years ago. IPF is a chronic,progressive lung disease with no cure. It results in fibroticscarring and thickening of lungs tissue, impairing oxygen delivery.Despite her diagnosis, patricia continues to work full time at herjob, taking the commuter train daily. However, over the past fewweeks the demands of activities of daily living have becomeincreasingly difficult. She complains of being tired, persistentdry cough, and extreme shortness of breath when climbing a flightof stairs. She had to take a medical leave from her job. Thefollowing information was obtained at her recent physicalexamination.

Arterial Blood Gases At Rest
PaO2	76 mm Hg
PaCO2	37 mm Hg
% Hgb Saturation	97%

Results of Pulmonary Function Tests at Rest
Total Lung Capacity	Decreased
Functional Residual Capacity	Decreased
Residual Volume	Decreased
FEV1/FVC	Increased

FEV₁ = volume of air expired in the first second offorced expiration; FVC, forced vital capacity

After these results were obtained at rest, Sue was asked toexercise on a stair climber. After only 2 minutes, she becameextremely fatigued and had to discontinue the test. The arterialblood gas measurements were repeated, with the followingresults.

Arterial Blood Gases During Exercise
PaO2	58 mm Hg
PaCO2	36 mm Hg
% Hgb Saturation	90%

1. Idiopathic pulmonary fibrosis is a restrictive pulmonarydisease. Define lung compliance and explain how lung fibrosisaffects lung compliance. Use this information to explain Patricia'sdecreased total lung capacity, decreased functional residualcapacity (FRC), and decreased residual volume atrest.