Ventilatory disturbances

Acid-base disorders are caused by disturbances in hydrogen ion (H+) homeostasis, which is ordinarily maintained by extracellular buffering, renal regulation of hydrogen ion and bicarbonate, and ventilatory regulation of carbon dioxide (C02) elimination. 

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. 

Bureau MA, Lamarche J, Foulon P, Dalle D. Postnatal maturation of respiration in intact and carotid body-chemodenervated lambs. J Appl Physiol 1985 59 869-874. Bureau MA, Lamarche J, Foulon P, Dalle D. The ventilatory response to h poxia in the newborn lamb after carotid body denervation. Respir Physiol 1985 60 109-119. Hofer MA. Sleep-wake state organization in infant rats with episodic respiratory disturbance following sinoaortic denervation. Sleep 1985 8 40 8. 

Exercise limitation and functional disability in COPD have a complex, multifactorial basis. Ventilatory limitation is caused by increased airways resistance, static and dynamic hyperinflation, increased elastic load to breathing, gas exchange disturbances, and mechanical disadvantage and/or weakness of the respiratory muscles (4-6). Car-diocirculatory disturbances (7,8), nutritional factors (9), and psychological factors, such as anxiety and fear, also contribute commonly to exercise intolerance. Skeletal muscle dysfunction is characterized by reductions in muscle mass (10,11), atrophy of type I (slow twitch, oxidative, endurance) (12,13) and type Ila (fast twitch) muscle fibers (14), altered myosin heavy chain expression (15), as well as reductions in fiber capillarization (16) and oxidative enzyme capacity (17,18). Such a dysfunction is another key factor that contributes... 

Malnutrition, acidosis, electrolyte disturbances, cachexia, infection, fatigue, and muscle dysfunction, aU exacerbate ventilatory insufficiency. Narcotics, sedatives, and supplemental oxygen reduce ventilatory drive and exacerbate alveolar hypoventilaticm. 

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