A nurse documents that a client is exhibiting Kussmaul's breathing. What assessment finding leads the nurse to this conclusion?

Choice A reason: Asymmetrical chest expansion is typically associated with structural or pleural pathologies, such as a pneumothorax, large pleural effusion, or fractured ribs. Kussmaul's respiration is a systemic metabolic response rather than a localized mechanical issue, and it generally involves profound, symmetrical thoracic excursions as the body attempts to compensate for severe acidosis. Choice B reason: Kussmaul's breathing is characterized by a markedly increased respiratory rate, often reaching 30 breaths per minute or higher, combined with extreme depth. This hyperpnea is a compensatory mechanism for metabolic acidosis, specifically diabetic ketoacidosis, where the lungs attempt to "blow off" excess carbon dioxide to increase the systemic pH levels. Choice C reason: A respiratory rate of 10 breaths per minute indicates bradypnea, which is the opposite of the hyperventilation seen in Kussmaul's breathing. Bradypnea may be caused by central nervous system depression, opioid overdose, or end-stage respiratory failure, whereas Kussmaul's represents an active, vigorous effort by the respiratory center to expel acid. Choice D reason: Shallow chest expansion is characteristic of hypoventilation or restrictive lung disease, not Kussmaul's. Kussmaul's respirations are famously "air hungry" and deep, involving maximal recruitment of respiratory muscles. Shallow breathing would lead to carbon dioxide retention, which would exacerbate the very metabolic acidosis that Kussmaul's breathing is designed to rectify.