Lungs ventilation disorders

Lung ventilation disorders, e.g. pneumothorax, chest injury... 

Krypton 81 2 x 10s years Gamma Diagnosis of lung and ventilation disorders... 

The ultimate mode of reduction in function, which, if sufficiently severe, results in death, is blood oxygen desaturation and accumulation of carbon dioxide. However, the inflammatory changes that the insults listed above can evoke and contribute to interference with the perfusion/ventilation relationship are varied and have different expressions in diverse lung disorders bronchial hyperresponsiveness after ozone or nitrous oxide... 

Mixed respiratory and metabolic acidosis may develop in patients with cardiorespiratory arrest, in those with chronic lung disease who are in shock, and in metabolic acidosis patients who develop respiratory failure. This mixed disorder should be treated by responding to both the respiratory and metabolic acidosis. Improved oxygen delivery must be initiated to improve hypercarbia and hypoxia. Mechanical ventilation may be needed to reduce PaC02. During the initial stage of therapy, appropriate amounts of alkali should be given to reverse the metabolic acidosis (see section on treatment of metabolic acidosis earlier in this chapter). 

Ans. Metabolic acidosis is a lowering of the blood pH as a result of a metabolic disorder as opposed to the failure of the H2CO3 — HCO3 buffer system. For example, there is a large and serious decrease in pH as a result of uncontrolled diabetes. The blood pH may fall from the normal 7.4 to as low as 6.8. The increased H concentration is due to the large amounts of ketone bodies produced in the liver. The products are acetoacetic acid and -hydroxybutyric acid. The bicarbonate buffer system attempts to compensate for the excess H", and the excess CO2 must be eliminated at the lungs. However, so much COj is lost by ventilation that the absolute concentration of the buffer system decreases, so the capacity of the buffer system is severely compromised and cannot reduce the metabolically produced excess H". In such cases, clinical treatment involves the intravenous administration of sodium bicarbonate to restore buffer capacity. 

The respiratory system is responsible for generating and regulating the transpulmonary pressures needed to inflate and deflate the lung. Normal gas exchange between the lung and blood requires breathing patterns that ensure appropriate alveolar ventilation. Ventilatory disorders that alter alveolar ventilation are defined as hypoventilation or hyperventilation syndromes. Hyperventilation results in an increase in the partial pressure of arterial CO2 above normal limits and can lead to acidosis, pulmonary hypertension, congestive heart failure, headache, and disturbed sleep. Hypoventilation results in a decrease in the partial pressure of arterial CO2 below normal limits and can lead to alkalosis, syncope, epileptic attacks, reduced cardiac output, and muscle weakness. 

Primary disorder lung disease causes Impaired ventilation or gas diffusion resulting in hypercapnia (increased arterial PCO2). Alternatively, non-pulmonary hypercapnia is caused by failure of the CNS respiratory centre to stimulate the respiratory muscles, see below... 

Ventilators are either negative-pressure or positive-pressure. Negative-pressure ventilation involves directing air directly into the lungs, and positive-pressure ventilation involves directing air into the trachea. Some ventilators require intubation, the placement of a tube into the trachea from the nose or mouth. Ventilation requiring intubation is typically used for patients who will require ventilation for a protracted period. Other ventilators work with a breathing mask that can be placed over the mouth and nose. With the increase in respiratory-related sleep disorders (such as obstructive sleep apnea), use of two positive airway pressure systems—continuous positive airway pressure (CPAP) and bilevel positive pressure ventilators (BiPAP)—has become very common. 

Respiratory failure may be classified as hypoxemic (type 1) or hypercapnic (type II or ventilatory failure) (3), either of which may be acute and chronic. Hypoxemic respiratory failure is due to failure of the lungs, caused by acute (cardiogenic pulmonary edema, pneumonia, acute respiratory distress syndrome) or chronic (emphysema, interstitial limg disorders) diseases (Tables 1 and 2). It is characterized by hypoxemia with normocapnia or hypocapnia. In these conditions central respiratory drive is high and there is sufficient alveolar ventilation (VA) to eliminate CO2 and prevent hypercapnia. 

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