How does heart failure typically affect left ventricular end-diastolic pressure (LVEDP)?
LVEDP remains within normal range
LVEDP decreases due to improved ventricular compliance
LVEDP is inversely proportional to cardiac output
LVEDP increases, contributing to pulmonary congestion
The Correct Answer is D
A. In symptomatic heart failure, it is physiologically impossible for the LVEDP to remain within a normal range because the heart cannot effectively empty. The residual volume after systole increases, which naturally raises the pressure at the end of the next filling phase. Maintaining a normal pressure range would imply that the heart's pumping efficiency is still preserved.
B. Heart failure is characterized by decreased ventricular compliance and impaired relaxation, which leads to an increase in pressure for any given volume. Compliance refers to the ability of the heart chamber to stretch; in failure, the walls become stiff or overstretched. Therefore, LVEDP rises significantly as the ventricle resists the incoming blood flow from the left atrium.
C. While LVEDP and cardiac output are related through the Frank-Starling mechanism, saying they are strictly inversely proportional is a physiological oversimplification. In the failing heart, the curve flattens, meaning that increasing LVEDP no longer results in an increased cardiac output. Eventually, the heart reaches a point where higher filling pressures actually lead to a further decline in stroke volume.
D. LVEDP increases because the weakened myocardium cannot eject blood efficiently, leading to high pressures that back up into the pulmonary veins. This increased hydrostatic pressure forces fluid into the alveolar spaces, which is the primary mechanism for pulmonary congestion and edema. Elevated LVEDP is a central hemodynamic finding that explains the shortness of breath in heart failure.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. Magnesium-ammonium phosphate stones, also known as struvite or "staghorn" calculi, account for approximately 10 to 15 percent of all renal stones. They are primarily associated with chronic urinary tract infections caused by urea-splitting bacteria like Proteus. While they can grow very large and cause significant damage, they are not the most frequently encountered type in the general population.
B. Cystine stones are rare, representing only about 1 to 2 percent of all cases of nephrolithiasis. They result from a genetic defect in the transport of amino acids, leading to high levels of cystine in the urine, which then crystallizes. Because they are the result of a specific inherited metabolic disorder, they are far less common than stones caused by dietary or idiopathic factors.
C. Calcium oxalate and phosphate stones are the most prevalent type of renal calculi, representing about 75 to 80 percent of all diagnosed cases. Their formation is often linked to hypercalciuria, hyperoxaluria, or hypocitraturia, which creates a supersaturated environment in the renal pelvis. These stones are typically radio-opaque on imaging, making them relatively easy to identify during a diagnostic workup for renal colic.
D. Uric acid stones occur in about 5 to 10 percent of patients and are often associated with gout, high-protein diets, or persistently acidic urine. Unlike calcium stones, uric acid stones are typically radiolucent and may not appear on standard abdominal X-rays. While they are a significant clinical concern, they remain much less frequent than stones composed of calcium salts.
Correct Answer is C
Explanation
A. Inspiratory crackles over the lung bases are clinical findings often associated with restrictive lung diseases or heart failure involving pulmonary edema. In chronic bronchitis, the primary issue is airway obstruction rather than alveolar fluid or interstitial fibrosis. While some secretions may cause coarse rales, fine basal crackles are not the defining feature of this condition.
B. Increased resonance, or hyperresonance, upon percussion is a classic finding in emphysema due to alveolar destruction and subsequent air trapping. In chronic bronchitis, the lung parenchyma often remains intact, and percussion notes may be normal. Hyperresonance indicates a loss of lung density that is specifically characteristic of the hyperinflated state of emphysema patients.
C. A prolonged expiratory phase is a hallmark physical finding of obstructive lung diseases, including chronic bronchitis. This occurs because inflammatory narrowing of the bronchioles increases airway resistance, making it more difficult and time-consuming for air to exit the lungs. This physiological delay is a compensatory mechanism to maintain airway pressure and facilitate more complete exhalation.
D. Decreased tactile fremitus occurs when there is an increase in the air-to-tissue ratio, such as in emphysema or a pneumothorax. In chronic bronchitis, the presence of excessive mucus and bronchial wall thickening may actually maintain or slightly increase the transmission of vocal vibrations. Decreased fremitus is not a sensitive or specific diagnostic sign for simple chronic bronchitis.
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