A patient newly diagnosed with left-sided heart failure is admitted to the hospital. The nurse will observe this patient closely for:

Choice A reason: Cardiac output has not fallen below normal levels. Cardiac output is the amount of blood pumped by the heart per minute. It is affected by the heart rate and the stroke volume. Angina pectoris does not directly affect the cardiac output, but it can reduce the stroke volume due to impaired ventricular filling.

Choice B reason: The vagus nerve is not stimulated. The vagus nerve is a cranial nerve that innervates the heart and other organs. It is part of the parasympathetic nervous system, which slows down the heart rate and lowers the blood pressure. Angina pectoris does not activate the vagus nerve, but it can trigger the sympathetic nervous system, which increases the heart rate and blood pressure.

Choice C reason: Myocardial stretch has not exceeded the upper limits. Myocardial stretch is the degree of tension or load on the cardiac muscle fibers. It is determined by the end-diastolic volume, which is the amount of blood in the ventricle at the end of relaxation. Angina pectoris does not cause excessive myocardial stretch, but it can impair the myocardial contractility due to ischemia.

Choice D reason: The myocardial oxygen supply has fallen below demand. This is the main cause of angina pectoris. It occurs when the coronary arteries, which supply blood and oxygen to the heart muscle, are narrowed or blocked by atherosclerosis or spasm. This creates an imbalance between the oxygen demand of the heart, which increases during exertion, and the oxygen supply, which is reduced by the obstruction.

Choice A reason: Respiratory acidosis does not cause no change in affinity of hemoglobin with oxygen. It causes a decrease in affinity of hemoglobin with oxygen, which means that hemoglobin releases more oxygen to the tissues. This is known as the Bohr effect, which is a physiological response to low pH and high CO2 levels.

Choice B reason: Respiratory acidosis causes a decrease in affinity of hemoglobin with oxygen, which means that hemoglobin releases more oxygen to the tissues. This is the correct statement that describes the expected finding in this patient. The decrease in affinity of hemoglobin with oxygen is a compensatory mechanism that tries to restore the oxygen balance in the body.

Choice C reason: Respiratory acidosis does not cause an increase in affinity of hemoglobin with oxygen. It causes a decrease in affinity of hemoglobin with oxygen, which means that hemoglobin releases more oxygen to the tissues. An increase in affinity of hemoglobin with oxygen would mean that hemoglobin holds on to oxygen more tightly, which would worsen the hypoxia in the patient.

Choice D reason: Respiratory acidosis does not cause a decrease in blood CO2. It causes an increase in blood CO2, which is the primary cause of the low pH. A decrease in blood CO2 would indicate respiratory alkalosis, which is a condition of high pH and low CO2 levels.