Quiz 112 · Respiration in Abnormal Conditions and Abnormal Respirations

Answers to Quiz 111 · Hazards of Deep Sea Diving and Increased Barometric Pressure

1. What is the total pressure on a diver at a depth of 20 m?

   Answer: 3 atmospheres

   Each 10 m of water adds 1 atm, and the air above adds another 1 atm, so 2 + 1 = 3 atm. Forgetting the surface atmosphere gives the tempting 2 atm. Revise hazards of deep sea diving

2. Nitrogen narcosis becomes severe at a depth of about:

   Answer: 250 ft (8.5 atm)

   Up to 100 ft the dissolved N₂ causes only euphoria. Narcosis begins at about 120 ft and is severe at 250 ft or deeper. Revise hazards of deep sea diving

3. A diver at 200 ft breathing 20% O₂ and 80% N₂ behaves as if drunk. Which finding fits his condition?

   Answer: Intellect altered but manual agility kept

   Nitrogen narcosis resembles alcohol intoxication: the thinking suffers but the hands work normally. Impaired manual dexterity points instead to HPNS on helium mixtures. Revise hazards of deep sea diving

4. Which is NOT a reason for using helium instead of nitrogen in deep-diving mixtures?

   Answer: Helium prevents the high-pressure nervous syndrome

   Helium mixtures are what cause HPNS on deep dives. The other three are your book's reasons for choosing helium. Revise hazards of deep sea diving

5. On a very deep dive breathing helium–O₂, a diver develops tremors, drowsiness and incoordination, and his EEG shows depressed α activity. The likely diagnosis is:

   Answer: High-pressure nervous syndrome

   These are the features of HPNS, which helium mixtures cause on deep dives. Nitrogen narcosis needs N₂ and spares manual dexterity. Revise hazards of deep sea diving

6. Why is the O₂ in gas mixtures for deep diving cut to about 20%?

   Answer: O₂ at high pressure is toxic, mainly to the CNS

   100% O₂ at high pressure causes acute O₂ toxicity: nausea, dizziness, disorientation, disturbed vision and convulsions, with lung damage as well. Revise hazards of deep sea diving

7. Decompression sickness is caused by:

   Answer: N₂ bubbles forming in tissues and blood on rapid ascent

   N₂ dissolved at depth comes out of solution too fast on rapid decompression and forms bubbles. Ruptured pulmonary veins describe air embolism, and the anesthetic effect of N₂ is narcosis. Revise hazards of deep sea diving

8. In decompression sickness, the pain is felt mainly in:

   Answer: Muscles and joints

   Bubbles in the tissues cause severe pain, chiefly in muscles and joints, usually within half an hour of surfacing. Revise hazards of deep sea diving

9. The severity of decompression sickness depends mainly on:

   Answer: The percentage fall in pressure

   A rapid fall to half the original pressure is safe, but a fall below 45% of it is harmful. So prevention never cuts the pressure by more than 50%. Revise hazards of deep sea diving

10. A diver develops joint pain and paresthesia 20 minutes after a rapid ascent. What is the treatment?

    Answer: Immediate recompression, then slow decompression

    He should be recompressed at once in a pressurized chamber, then decompressed slowly; hyperbaric O₂ also helps. Recovery is usually complete, though some neural deficits may remain. Revise hazards of deep sea diving

11. Decompression sickness can occur without any diving, in a person who:

    Answer: Is flown rapidly to about 9000 m in an unpressurized cabin

    A rapid climb from sea level to about 9000 m in an unpressurized aircraft cabin is a sudden fall from high to low pressure, which is all decompression sickness needs. Revise hazards of deep sea diving

12. A diver breathing compressed gas from a tank at 5 m panics and shoots to the surface holding his breath, then collapses. The most likely cause is:

    Answer: Air embolism

    The lung gas expands on the rapid ascent, ruptures pulmonary veins and lets air into the circulation. It can happen from as shallow as 5 m, while narcosis and HPNS need far greater depths. Revise hazards of deep sea diving

13. According to your book, the cylinders of a SCUBA set contain:

    Answer: Compressed helium and O₂

    Your book describes SCUBA as a tank-and-valve system whose cylinders hold helium and O₂, chosen because the mixture is less toxic on deep dives. Revise hazards of deep sea diving

15 questions on chapter 112. Pick one answer for each, then save. Your answers stay in this browser, and the right ones are shown at the top of the next quiz.

1. Asphyxia is best defined as:

Hyperventilation with hypocapniaHypercapnia with a normal PO₂Hypoxia combined with hypercapniaHypoxia with a normal PCO₂

2. Generalized convulsions with tachycardia and a rise in blood pressure belong to which stage of asphyxia?

Stage of exhaustion and collapseStage of convulsionStage of exaggerated breathingStage of laryngospasm

3. In fever, a rise in body temperature of 1°C increases CO₂ production by about:

50%30%3%13%

4. In profound hypercapnia with respiratory acidosis, plasma bicarbonate may exceed:

40 mEq/L30 mEq/L24 mEq/L60 mEq/L

5. Hypoxia occurring together with hypercapnia is termed:

Type I respiratory failureCompensated respiratory alkalosisType II respiratory failurePrimary metabolic acidosis

6. During voluntary hyperventilation performed as an experiment, arterial PCO₂ may fall as low as, and arterial PO₂ may rise up to:

40 mmHg and 160 mmHg25 mmHg and 100 mmHg15 mmHg and 140 mmHg35 mmHg and 120 mmHg

7. Which of these is NOT an effect of hypocapnia?

Depression of the vasomotor centerA fall in cardiac outputA rise in plasma bicarbonateCarpopedal spasm

8. A man is pulled from a freshwater lake after inhaling water. The expected change in his blood is:

A rise in plasma protein concentrationHemodilution with hemolysisHemoconcentration from fluid moving into the alveoliAn unchanged blood volume with a raised hematocrit

9. A physiological cause of respiratory alkalosis is:

Barbiturate overdoseDiabetic ketoacidosisPneumothoraxAscent to high altitude

10. In the periodic breathing that follows voluntary hyperventilation, the apnea occurs because:

PO₂ has fallen too low to stimulate the chemoreceptorsThe pharyngeal muscles have lost their tonePlasma bicarbonate has risen above 40 mEq/LCO₂ has been washed out, removing the CO₂ drive on ventilation

11. Cheyne-Stokes respiration is seen in all of the following EXCEPT:

Renal failureDiabetic ketoacidosisHeart failureUnacclimatized people at high altitude

12. A 19-year-old with type 1 diabetes is drowsy and breathing deeply and rapidly, with ketones in the urine. This breathing pattern is:

Biot's respirationKussmaul breathingHysteric hyperpneaCheyne-Stokes respiration

13. Biot's respiration consists of:

Breaths that wax and wane in depth before each apneaThree to four normal cycles followed by abrupt apneaContinuous deep rapid breathing with no apneaApnea occurring only during REM sleep

14. A middle-aged man wakes repeatedly through the night and complains of morning headache and fatigue. The immediate cause of his apneas is:

Metabolic acidosis stimulating the respiratory centerLoss of rhythmic activity of the respiratory centerIncreased sensitivity of the respiratory center to CO₂Loss of pharyngeal muscle tone during REM sleep

15. In Ondine's curse, the patient after brain injury:

Loses voluntary breathing but retains automatic breathingBreathes normally awake and hyperventilates asleepLoses automatic breathing but retains voluntary breathingLoses both automatic and voluntary breathing

Save my answers