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Exercise intolerance in chronic airflow limitation: Mechanisms of dyspnea (2)

These studies showed that, compared with type B, type A patients were more limited, kept PaCC>2 lower and showed a fall in PaOi with exercise (Figure 6); they had a large Vd/Vt and an alveolar-arterial (A-a) PO2 difference that increased. Type B patients showed a wide A-a PO2 difference at rest, but this narrowed with exercise, suggesting that areas in the lung with a low Va/Qc ratio improved their ventilation equally with the overall increase in exercise ventilation. Our thought then was that this behaviour removed a hypoxic drive to breathe during exercise and contributed to chronic underventilation, but this was an oversimplification. More recently, the elegant multiple inert gas washout technique has been applied to type A and B patients to confirm the dominant Va/Qc patterns. The combination of improving, contrasted with worsening, Va/Qc distribution, together with overall underventilation leads to ventilation being lower and dyspnea less prominent in the type B patient. Best quality drugs are available at the best pharmacy that you can start shopping with right now whenever you need buy levitra super active plus, never having to doubt the choice made or the quality of the drug you get.

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