Restrictive Disease In General

Question 1

What do all restrictive lung diseases have in common?

Answer 1

dec lung volumes

Question 2

3 General Categories

Answer 2

• 1- Disorders of Inc Elastic Recoil of Lungs
• 2- Disorders of Limited Expansion of Chest Wall
• 3- Disorders of Impaired Respiratory Muscle Function

Question 3

Disorders of Elastic Recoil (Patho and causes)

Answer 3

• Limiting Factor = Lungs (dec compliance - smaller deltaV for given delta P)
• Causes - interstitial lungs diseases (scarring)
• Alterations in Gas Exchange (Dec DLco)

Question 4

How is diffusion capacity affected in interstitial lung diseases?

Answer 4

• Alveoli and cap destruction –> less capillaries so faster flow thru remaining caps –> less time for equilibration
• Interstitial thickening (greater diffusion distance - inc thickness) –> less time for equilibration (dec DLco)
  - Both lead to exercise limitation (b/c exercise further inc CO)
• Under-perfusion of most diseased areas and over-perfusion of less diseased areas –> V/Q mismatch –> dec PaO2 and inc A-a gradient and eventually inc PaCO2

Question 5

Is PaCO2 elevated in interstitial lung disease?

Answer 5

• As disease progresses… inc RR and VE to comp (rapid, shallow breath) but eventually cannot fully comp for inc PaCO2
• So do not see inc PaCO2 until late in the disease course

Question 6

Diseases of Limited Chest Expansion (Patho and causes)

Answer 6

• Dec equilibrium volume of chest wall (impede expansion) –> makes overall FRC lower
• This means more work for inspiratory muscles until they eventually fatigue –> hypoventilation –> hypercapnia
• Causes - kyphoscoliosis, diaphragmatic hernia, pectus deformities, morbid obesity, massive ascites

Question 7

Disease of Resp Muscle Function (Patho and causes)

Answer 7

• Insp muscle problem –> lower TLC (cannot fully overcome Plungs and Pwall)
• Exp muscle problem –> inc RV (more left after expiration) and dec expiratory reserve volume
• Normal FRC b/c lung and wall recoil unaffected
• Causes - CNS problem, peripheral nerve problem (Guillan-Burre), neuromuscular junction (MG and Lambert Eaton), muscles themselves (muscular dystrophy)

Question 8

What PFT changes do all restrictive lung diseases share?

Answer 8

• Dec FVC, FEV1, FEF25-75, TLC

- FEV1/FVC normal (both dec)

Question 9

PFT Diff In Inc Lung Recoil/Chest Expansino v. Muscle Dysfuntion

Answer 9

Recoil Probs-

• FRC dec (lower equil pt)
• RV dec
• PEPR (peak) normal to inc
• May have dec diffusion capacity if interstitial

Muscle Probs-

• FRC normal (not a chest or lung problem so unaffected)
• RV inc (if expiratory muscles cannot get all air out)
• PEPR (peak) is dec
• Diffusion capacity is normal

Question 10

ALS (major problems and tx)

Answer 10

• Muscle atrophy (intercostals, thenar wasting, tongue atrophy)
• Effects both insp (diaphragm and external intercostals) and exp muscles (lung recoil, ab rectus, internal
  intercostals)
• Major prob = inability to cough/clear airway; meas peak flow while asking pt to cough and if low then consider using airway assistance (insufflator-exsufflator - sucks air out)
• Also nutrition (help muscles) and poss non-invasive vent (BiPAP)