A nurse is reviewing ABG values for a client who has emphysema. Which of the following findings indicates a need for mechanical ventilation?

Arterial blood gas (ABG) interpretation in a client with Emphysema is essential for evaluating gas exchange and ventilatory status. Emphysema causes destruction of alveolar walls, leading to impaired carbon dioxide elimination and air trapping. Over time, patients may develop chronic respiratory acidosis due to persistent CO₂ retention. A significant rise in PaCO₂ with signs of respiratory failure may indicate the need for mechanical ventilation support. Rationale: A. SaO₂ of 90% is mildly reduced but may be acceptable in clients with chronic emphysema due to their adapted lower oxygen baseline. Oxygen saturation targets are often lower in COPD patients to avoid suppressing hypoxic respiratory drive. This value alone does not indicate immediate need for mechanical ventilation. B. PaCO₂ of 62 mm Hg is significantly elevated and indicates hypercapnia due to inadequate ventilation. In emphysema, CO₂ retention reflects worsening respiratory failure and fatigue of respiratory muscles. When elevated PaCO₂ is accompanied by clinical deterioration or acidosis, mechanical ventilation may be required to support gas exchange and prevent respiratory collapse. C. HCO₃⁻ of 24 mEq/L is within normal range and does not indicate an acute acid-base imbalance requiring ventilatory support. In chronic respiratory conditions like emphysema, bicarbonate may be elevated as renal compensation, but a normal value suggests no acute metabolic disturbance. It does not independently signal respiratory failure. D. PaO₂ of 82 mm Hg is within the expected or acceptable range for many clients, including those with chronic lung disease. Although slightly lower than ideal, it does not indicate severe hypoxemia requiring mechanical ventilation. Oxygenation status alone is not the primary trigger for ventilatory support unless accompanied by significant CO₂ retention or respiratory distress.