Anne, who is drinking beer at a party, falls and hits her head on the ground. Her friend Liza dials "911" because Anne is unconscious, has depressed ventilation (shallow and slow respirations), rapid heart rate, and is bleeding from both ears.
Which primary acid-base imbalance is Anne at risk for if medical attention is not provided?
Respiratory Alkalosis.
Metabolic Alkalosis.
Respiratory Acidosis.
Metabolic Acidosis.
The Correct Answer is C
Choice A rationale
Respiratory alkalosis occurs due to hyperventilation, leading to excessive carbon dioxide expulsion. This reduces the partial pressure of carbon dioxide ($PaCO_2$), increasing the pH. Anne's depressed ventilation indicates hypoventilation, not hyperventilation, which would cause an accumulation of $CO_2$ rather than its expulsion. Therefore, respiratory alkalosis is not the primary imbalance she faces.
Choice B rationale
Metabolic alkalosis arises from an excess of bicarbonate ($HCO_3^-$) or a loss of hydrogen ions ($H^+$), typically from vomiting or diuretics. This increases the pH. Anne's symptoms of depressed ventilation and head trauma do not directly point to a primary metabolic issue causing $HCO_3^-$ retention or $H^+$ loss; her immediate risk is respiratory compromise.
Choice C rationale
Respiratory acidosis develops when the lungs cannot adequately remove carbon dioxide ($CO_2$), leading to its accumulation in the blood. This accumulation increases carbonic acid, which lowers the pH. Anne's depressed ventilation (shallow and slow respirations) directly impairs $CO_2$ excretion, causing $CO_2$ retention and a decrease in blood pH, thus predisposing her to respiratory acidosis. Normal $PaCO_2$ range is 35-45 mmHg.
Choice D rationale
Metabolic acidosis results from an accumulation of non-carbonic acids or a loss of bicarbonate ($HCO_3^-$). This lowers the pH. While head trauma can sometimes lead to metabolic derangements, Anne's immediate and primary physiological compromise is depressed ventilation, which directly affects $CO_2$ elimination and respiratory acid-base balance rather than metabolic acid accumulation or bicarbonate loss.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale
Normal arterial blood gas (ABG) values are pH 7.35-7.45, $PaCO_2$ 35-45 mmHg, and $HCO_3^-$ 22-26 mEq/L. Olivia's ABG results of pH 7.40, $PaCO_2$ 40 mmHg, and $HCO_3^-$ 24 mEq/L all fall within these normal physiological ranges, indicating no acid-base imbalance despite her anxiety and hyperventilation episode.
Choice B rationale
Intubation is a medical procedure to secure an airway, typically for respiratory failure or severe oxygenation/ventilation issues. Olivia's ABG results are completely normal, indicating effective gas exchange and no respiratory distress requiring intubation. There is no physiological basis in these ABG numbers to warrant such an invasive intervention.
Choice C rationale
Inconclusive results suggest that the data gathered is insufficient or ambiguous to draw a definitive conclusion. However, Olivia's ABG results are clearly within normal physiological parameters. The values are precise and fall squarely within the reference ranges, making them conclusive for normal acid-base status.
Choice D rationale
Partial compensation in acid-base balance occurs when the body's compensatory mechanisms are actively trying to correct a primary imbalance but have not fully restored the pH to normal. Since Olivia's pH, $PaCO_2$, and $HCO_3^-$ are all within normal limits, there is no primary imbalance for which the body needs to compensate, thus ruling out partial compensation. .
Correct Answer is A
Explanation
Choice A rationale
The non-rebreather mask delivers the highest possible fraction of inspired oxygen (FiO2) among conventional oxygen delivery devices, often reaching 85-90%. This high concentration is achieved by a one-way valve system that prevents exhaled air from mixing with the inspired oxygen and a reservoir bag that stores a high concentration of oxygen. This mechanism minimizes room air entrainment, maximizing oxygen delivery to the patient's respiratory system.
Choice B rationale
A non-rebreather mask is designed to deliver high concentrations of oxygen and prevent rebreathing of exhaled gases, including carbon dioxide. The one-way valves direct exhaled air out of the mask, ensuring that the patient inhales nearly pure oxygen from the reservoir bag, thereby minimizing CO2 retention, not increasing it. This physiological effect ensures efficient gas exchange.
Choice C rationale
While a simple mask may appear less complex in its physical design, its operation still requires proper fitting and flow rate adjustment for effective oxygen delivery. The perceived simplicity does not outweigh the significant physiological advantage of a non-rebreather mask in delivering higher oxygen concentrations, which is the primary goal of oxygen therapy.
Choice D rationale
Non-rebreather masks, due to their tight seal and large reservoir bag, can exacerbate feelings of claustrophobia in some patients. Similarly, the mask's design might induce or worsen nausea in individuals prone to it, making simpler face masks or nasal cannulas often more tolerable options for these patient populations. Patient comfort and tolerance are crucial considerations in oxygen therapy.
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