chronic respiratory failure

Question 1

definition

Answer 1

• Condition with abnormal gas composition of the blood, or this abnormality is compensated for by intense work of external respiratory apparatus & higher load of the heart.
• Occurs when pulm gas exchange is sufficiently impaired to cause hypoxemia with or without hypercapnia.
• Present when PaO2 < 8 kPa (60mmHg) or the PaCO2 > 7 kPa (55mmHg)

Question 2

pathogenesis

Answer 2

Arises during uneven distribution of air in the lungs when a part of the lung is not ventilated (in pneumonia atelectasis) with preservation of blood circulation.
Part of venous blood is not oxygentd before it enters pulm vv & the L heart chambers.
Vascular shunting (fr R to L) during which part of the venous blood fr the pulm artery syst enters directly the pulm vv (bypassing the capillaries) to mix with oxygenated arterial blood.
Oxygenation of blood in lungs is thus upset but hypercapnia may be present but to compensatory intensification of ventilation in the intact parts of the lungs.
This is partial respi insufficiency (different fr total respi insufficiency where hypoxemia & hypercapnia are present).

Question 3

classification

Answer 3

1. Type IA Respiratory failure (Acute Hypoxemic RI)
   - PaCO2 is normal (35-40mmHg) or low but PaO2 is reduced (80-100 mmHg).
   - Hypoxia with respiratory alkalosis.
   - marked V/Q abnormality (V – ventilation, P – perfusion) & intrapulmonary shunting
   - Occurs aar of pulmonary restriction in diffuse PN, pulmonary edema, ARDS, pulmonary embolism & fibrosing alveolitis
2. Type IIB Respiratory insufficiency (Ventilatory failure)
   - PaCO2 is elevated & PaO2 is reduced i.e. hypoxemia & hypercapnia – ventilatory failure
   - both V/Q imbalance & inadequate alveolar ventilation
   - Occurs in COPD, chronic bronchitis, emphysema, acute obstructive lung disease, asthma & intrinsically by narcotics & sedatives, due to general bronchial obstruction

Question 4

clinical symptoms according to stages

Answer 4

Grade
1
2
3

Charac
Dyspnea & mild hypoxemia with strenuous, prolonged exertion No signs of RF at rest
Dyspnea, cyanosis & inadequate hypoxemia with ordinary physical activity
Dyspnea, cyanosis & severe hypoxemia with minimal physical activity or even at rest

PaO2
50-85 mmHg
30-50 mmHg
<30 mmHg

PaCO2
45-50 mmHg
50-80 mmHg
>80 mmHg

Question 5

subjective examination

Answer 5

• Dyspnea
• ↓ed tolerance level of physical activity
• Early: dyspnea, cyanosis, inadequate changes in ventilation (rapid & deep breathing at slight physical exertion)
• Later : cardiac failure (edema), tachypnea, tachycardia & signs of intensified work of respiratory mm, involvement of accessory mm during light exercise & at rest,

Question 6

objective examination

Answer 6

• Dyspnea at either significant physical load/light exercise/rest – rapid changes of resp, rapid & deep breathing, intensified work of resp mm., ↑ resp rate, paradoxical respiration (abdominal & thoracic compartments move in different direction)
• Cyanosis – Pink puffers (hypoxemia w/o hypercapnia) & blue blotter –edematous cyanotic ptts with ventilatory failure (hypoxia & hypercapnia)
• Disorderred orientation, flaring of nostrils, pursed-lip breathing, use of accessory muscles of respiration
• Heart failure (edema)
• Tachycardia

Question 7

investigation

Answer 7

1. Pulmonary function test (spirometry) – rise resp rate, tidal volume measurement, vital capacity
2. Arterial blood gas
3. ECG
4. Chest X ray
5. JVP, physical examination

Question 8

obstructive type

Answer 8

• Characterized by difficult passage of air through the bronchi (bronchospasm) & compression/contractn of large bronchi & trachea.

Obstruction of air passage increases load on resp mm.

The ability of resp. apparatus to perform additional functional load decreases : fast inspiration & expiration, & rapid breathing becomes impossible.

The 1‘ obstructive ventilatory defects are :
COPD, Chronic bronchitis, Pulmonary emphysema, Bronchial asthma, Cystic fibrosis

Question 9

restrictive type

Answer 9

Occurs in limited ability of lungs to expand & to collapse. limited depth of maximum inspiration.

Vital capacity of lungs ↓ but dynamics of resp is not affected & breathing rate is normal. The 1‘ restrictive ventilatory defects are :

1. Parenchymal disorders
   - Alveolar & interstitial procs (edema, fibrosis, infection)
   - Large space occupying tissue
   - Atelectasis
   - Resection of pulm tissue
2. Chest wall disease
   - Obesity
   - Kyphoscoliosis
   - Ankylosing spondilytis
3. Pleural diseases
   - Effusion
   - Pneumothorax
   - Fibrothorax
4. Neuromuscular diseases
   - Guillian-Barre syndrome (resp mm. weakness)
   - Diaphragmatic weakness: pleural nerve palsy
   - Spinal cord injury, Poliomyelitis
   - Disorders of respiratory center (drug intoxicant, vascular disorders, trauma, infection)
   - Disorders of impulse transmission

Question 10

test for obstructive and restrictive lung

Answer 10

Test
Obstructive lung
Restrictive lung

FEV1
Markedly ↓
↓

Vital capacity (VC)
↓ / Normal
↓

FEV1/VC (80%) the difference index
↓ to 70-75%
Normal >75

Question 11

treatment

Answer 11

1. Initial management – establish adequate oxygenation (endotracheal tube + mechanical ventilation)
2. Depends on the etiology
   - removing excess secretion by suction
   - treating infections – AB
   - suppress inflmtn – anti inflmtory/immunosuppressive drugs
   - treat obstruction – bronchodilators
   - Dissolving blood clots – anticoagulants or thrombolytics
   - lung transplantation