Asthma and COPD Q 18 - Gyan Darpan : Learning Portal
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Sunday 24 April 2022

Asthma and COPD Q 18

A nurse is caring for a client with emphysema. The client is receiving oxygen. The nurse assesses the oxygen flow rate to ensure that it does not exceed:
     A. 1 L/min
     B. 2 L/min
     C. 6 L/min
     D. 10 L/min

Correct Answer: B. 2 L/min

One to 3 L/min of oxygen by nasal cannula may be required to raise PaO2 to 60 to 80 mm Hg. However, oxygen is used cautiously and should not exceed 2 L/min. Because of the long-standing hypercapnia, the respiratory drive is triggered by low oxygen levels rather than increased carbon dioxide levels, as is the case in a normal respiratory system. Supplemental oxygen can successfully reach the alveoli in these lungs, which prevents this vasoconstriction and thereby increases perfusion and improves gas exchange, thus resulting in improvement of hypoxemia.

Option A: Routine supplemental oxygen does not improve the quality of life or clinical outcomes in stable patients. Continuous long-term, i.e., longer than 15 hours of supplemental oxygen is recommended in patients with COPD with PaO2 less than 55 mmHg (or oxygen saturation less than 88%) or PaO2 less than 59 mm Hg in case of cor pulmonale.
Option C: Oxygen therapy has shown to increase the survival of these patients with severe resting hypoxemia. For those who desaturate with exercise, intermittent oxygen will help. The goal is to maintain oxygen saturation greater than 90%.
Option D: Excessive correction of hypoxia in a patient with longstanding COPD can sometimes lead to hypercapnia. This is due to the loss of compensatory vasoconstriction with an ineffective gas exchange as there is a loss of hypoxic drive for ventilation. Also, increased oxyhemoglobin decreases the uptake of carbon dioxide due to the Haldane effect.

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