A client with Guillain-Barré syndrome has experienced a sharp decline in vital lung capacity. What is the most appropriate nursing action.

Choice A rationale Bronchodilators and inhaled corticosteroids are used to treat conditions involving bronchospasm or airway inflammation, such as asthma or COPD. Guillain-Barré syndrome causes ascending, progressive peripheral neuropathy that can lead to respiratory muscle paralysis. A sharp decline in vital lung capacity indicates neuromuscular failure, which these drugs cannot correct, and a more aggressive intervention is needed. Choice B rationale Deep breathing and coughing exercises rely on functional respiratory and accessory muscles, which are becoming paralyzed in advanced Guillain-Barré syndrome as indicated by the sharply declining vital lung capacity. This exercise may be futile or exhausting for a client with failing respiratory effort. This measure is insufficient and does not address the underlying and rapidly progressing neuromuscular respiratory failure. Choice C rationale A sharp decline in vital lung capacity in Guillain-Barré syndrome is a direct indicator of impending or acute respiratory failure due to paralysis of the diaphragm and intercostal muscles. A vital capacity significantly below 15 mL/kg or a rapid drop necessitates immediate preparation for oral intubation and mechanical ventilation to secure the airway and support breathing, as this is a life-threatening emergency. Choice D rationale Supplementary oxygen via nasal cannula only addresses hypoxemia but does not support the mechanics of breathing or ventilation. In respiratory failure caused by neuromuscular weakness, the client's ability to move air is impaired (ventilatory failure), and oxygen alone will not prevent a buildup of carbon dioxide or ensure sufficient gas exchange, thus being an inadequate intervention for a sharply declining vital capacity.