Answers to Quiz 112 · Respiration in Abnormal Conditions and Abnormal Respirations
Asphyxia is best defined as:
Answer: Hypoxia combined with hypercapnia
Asphyxia needs both gases to be abnormal: PO₂ down and PCO₂ up, usually from mechanical airway obstruction. Hypoxia with a normal PCO₂ is type I respiratory failure, not asphyxia. Revise asphyxia, hypercapnia and hypocapnia
Generalized convulsions with tachycardia and a rise in blood pressure belong to which stage of asphyxia?
Answer: Stage of convulsion
The second stage lasts about a minute: respiratory efforts turn violent, convulsions appear, and sympathetic discharge with catecholamine release raises both heart rate and blood pressure. In the third stage blood pressure falls instead. Revise asphyxia, hypercapnia and hypocapnia
In fever, a rise in body temperature of 1°C increases CO₂ production by about:
Answer: 13%
Each 1°C raises CO₂ production by 13%. Fever also stimulates breathing, so the extra CO₂ is normally blown off and hypercapnia appears only if ventilation is compromised as well. Revise asphyxia, hypercapnia and hypocapnia
In profound hypercapnia with respiratory acidosis, plasma bicarbonate may exceed:
Answer: 40 mEq/L
Plasma bicarbonate may go above 40 mEq/L, because renal tubular reabsorption of HCO₃⁻ comes to exceed its excretion. That rise is compensation for the acidosis, not its cause. Revise asphyxia, hypercapnia and hypocapnia
Hypoxia occurring together with hypercapnia is termed:
Answer: Type II respiratory failure
Hypoxia with hypercapnia is type II respiratory failure; hypoxia with a normal PCO₂ is type I. The distinction matters because only type II patients depend on a hypoxic drive. Revise asphyxia, hypercapnia and hypocapnia
During voluntary hyperventilation performed as an experiment, arterial PCO₂ may fall as low as, and arterial PO₂ may rise up to:
Answer: 15 mmHg and 140 mmHg
Over-breathing washes out CO₂ down towards 15 mmHg while raising O₂ intake, so PO₂ climbs to about 140 mmHg. Both gases move, which is why hypocapnia is never a pure CO₂ problem. Revise asphyxia, hypercapnia and hypocapnia
Which of these is NOT an effect of hypocapnia?
Answer: A rise in plasma bicarbonate
Hypocapnia goes with respiratory alkalosis, in which plasma bicarbonate is decreased, not raised. The vasomotor and respiratory centers are depressed, cardiac output falls with coronary flow, and low ionized calcium can give carpopedal spasm and a Chvostek sign. Revise asphyxia, hypercapnia and hypocapnia
A man is pulled from a freshwater lake after inhaling water. The expected change in his blood is:
Answer: Hemodilution with hemolysis
Fresh water in the lungs is rapidly absorbed into the blood, so the blood is diluted and red cells hemolyse. Hemoconcentration is the seawater picture, where hypertonic water pulls fluid out of the vessels into the lung. Revise asphyxia, hypercapnia and hypocapnia
A physiological cause of respiratory alkalosis is:
Answer: Ascent to high altitude
At altitude the hypoxic drive makes a healthy person hyperventilate, lowering PCO₂ and H⁺. Barbiturates and pneumothorax cause respiratory acidosis, and ketoacidosis is a metabolic acidosis. Revise asphyxia, hypercapnia and hypocapnia
In the periodic breathing that follows voluntary hyperventilation, the apnea occurs because:
Answer: CO₂ has been washed out, removing the CO₂ drive on ventilation
Over-breathing strips out the CO₂ that normally drives ventilation, so breathing stops until PCO₂ builds back up. Falling PO₂ does the opposite: it stimulates the chemoreceptors and restarts breathing. Revise abnormal breathing patterns
Cheyne-Stokes respiration is seen in all of the following EXCEPT:
Answer: Diabetic ketoacidosis
Diabetic ketoacidosis gives Kussmaul breathing, which is continuous and has no apnea. Premature infants, unacclimatized climbers, deep sleep, heart failure and renal failure are the listed causes of Cheyne-Stokes respiration. Revise abnormal breathing patterns
A 19-year-old with type 1 diabetes is drowsy and breathing deeply and rapidly, with ketones in the urine. This breathing pattern is:
Answer: Kussmaul breathing
Acetoacetic and β-hydroxybutyric acid produce a metabolic acidosis that stimulates the respiratory centers, giving the deep rapid air hunger Kussmaul described. Hysteric hyperpnea washes out CO₂ and causes alkalosis, the opposite acid-base state. Revise abnormal breathing patterns
Biot's respiration consists of:
Answer: Three to four normal cycles followed by abrupt apnea
Biot's pattern is three or four normal breaths, often a deep gasp, then sudden apnea, and it points to the medulla: meningitis, raised intracranial pressure, morphine poisoning, brainstem damage. The waxing and waning pattern is Cheyne-Stokes respiration. Revise abnormal breathing patterns
A middle-aged man wakes repeatedly through the night and complains of morning headache and fatigue. The immediate cause of his apneas is:
Answer: Loss of pharyngeal muscle tone during REM sleep
In adult sleep apnea syndrome pharyngeal tone is markedly lost in REM sleep, so the airway is obstructed during inspiration. Loss of rhythmic respiratory center activity is the mechanism proposed for sudden infant death syndrome instead. Revise abnormal breathing patterns
In Ondine's curse, the patient after brain injury:
Answer: Loses automatic breathing but retains voluntary breathing
Automatic control is lost while voluntary breathing survives, so these patients need intermittent respiratory assistance and are in danger the moment they stop attending to breathing, as in sleep. Revise abnormal breathing patterns
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