CO2 retention is seen in:
B i.e. Respiratory failure Type II respiratory failure, which occurs d/t hypoventilation (i.e. failure of ventilation) is characterized by hypoxemia with hypercapnia (CO2) retention but normal (not increased) alveolar-aerial oxygen gradient IP 1 Aa02, Hypercapnia (hypercarbia or CO2 retention) is defined as an elevation in aerial paial pressure of carbon dioxide (Pco2). It characteristically occurs secondary to inadequate alveolar ventilation (hypoventilation), in type II respiratory failure. - - Type II respiratory failure (or alveolar hypoventilation = alveolar ventilatory failure = hypercapnia = hypercarbia = CO2 retention = respiratory acidosis) or normal PA-a02 is seen in reduced compliance of chest like kyphoscoliosisQ, reduced lung compliance like pulmonary (alveolar) edetnaQ, obstructive lung disease like COPDQ, weakness of respiratory muscle (like bulbar poliomyelitisQ), bronchospasm and decreased central respiratory drive. Drowning may cause bronchospasm & pulmonary edema & so CO2 retention. - Type I respiratory failure results from failure in exchange (diffusion) of respiratory gases at the alveolar-capillary junction as a result of disease of lung parenchyma (like pneumonia), or vasculature (like right to left shunt), and ventilation-perfusion mismatchQ. It is characterized by increased alveolar-aerial oxygen gradient (PA-ao2)Q, hypoxemia and normal or low PaCO2. - At high altitudes alveolar CO2 decreases b/o hyperventilation. Respiratory failure is defined as a disorder wherein lung function is inadequate to meet the metabolic demands of the individual and is unable to maintain normal aerial cas level in the blood. Type Characteristic Features Causes RF-I Represents failure of oxygenation, and is characterized by dysponea and secondary hyperventilation l/t Results from failure in exchange of respiratory gases (mainly 02)at the alveolar capillary junction (i.e. alveolar capillary block syndrome) as a result of disease of lung parenchyma. There is thickening of alveolar or capillary wall resulting in ventilation -perfusion (V-Q) - Hypoxemia (Pao2 - decreased; < mismatch. Only 02 transfers is affected because CO2 is 20 times more diffusible. So causes 60 mm Hg) are - Increased alveolar - aerial I. Parenchymal (interstitial) lung diseases Oxygen gradients' (PA-ao2 > 15 mm Hg) - which thicken alveolar - capillary membrane eg. asbestosis, sarcoidosis, pneumoconiosis, berylliosis, diffuse interstitial fibrosis, infiltrative lung disease like - Normal or decreased Paco2 ( 40 malignancy & granulomatosis. mmHg) i.e. respiratory alkalosis - Which separate A-C membrane like pulmonary (interstial) edema (in cardiac failure) and exudates (pneumonitis or pneumonia)(2 and (resultant) pulmonary fibrosis. II. Mixing of venous blood with aerial blood like right to left shuntQ. III. Ventilation - Perfusion mismatch Q: In emphysema surface area for diffusion decreases (i.e. poorly ventilated alveoli increase). Mn: "RAPE-VIP" = "Right to left shunt, Alveolar (pulmonary) edema, parenchymal disease (pneumonia), emphysema - ventilation perfusion mismatch". RF II Represents failure (defect) in I. Decreased central respiratory drive to breathe ventilation and is characterized by - Drug like morphine, sedative & anesthetics overdose. hypoventilation lit - Brain stem injury, bulbar poliomyelitisQ, hypothyroidism, sleep disordered breathing. - Hypoxemia (Pao2 decreased; < 60 II. Respiratory muscle weakness mmHg) - Normal alveolar-aerial oxygen - Neuromuscular disorders like myasthenia gravis, GB syndrome, bulbar poliomyelitis, ALS. gradient (PA-ao2 < 15 mmHg) - Myopathy, polymyositis, electrolyte derangement. - Hypercapnia (Paco2 > 40 mm Hg) III.Obstructive lung disease i.e. respiratory acidosis Q. - Acute obstruction like foreign body, laryngeal edema, bronchospasm, asthma - COPD (esp during acute exacerbation) like chronic bronchitis, emphysema, interstial lung disease. IV.Increased load on respiratory system d/t - Resistive load eg bronchospasm - Reduced chest wall compliance eg. pleural effusion, pneumo/fibro - thorax, abdominal distension (ascitis), rib cage disorder (kyphoscoliosis)Q, ankylosing spondylitis, flail chest. - Reduced lung compliance eg. atelectasis, lung resection, alveolar edema (ARDS)Q, PEEP (positive end expiratory pressure). - Increased minute ventilation requirements eg pulmonary embolism with increased dead space, sepsis. RF III Also called peri-operative respiratory failure Occurs as a result of atelectasis and atelectasis is common in perioperative period RF IV Result of hypoperfusion of respiratory muscles Occurs in patient with shock
Carbon monoxide poisoning
Respiratory failure
High altitude
All