Chapter 20.

Multiple Choice Questions

I: Answers B, D, and E are true statements, whereas A and C are false.

II: Answers A, C, and D are true statements, whereas B and E are false.

Case History A

1.       The blood alcohol-permille or concentration at 8 p.m. is (1.48 + 60 min * 0.0020) = 1.6 g kg-1 or 1.6 permille at the time of the traffic accident.  

2.       The alcohol intake is (150 ml * 0.40) = 60 g of alcohol (ethanol). The distribution pool for alcohol is (58 kg * 0.60) = 34.8 kg. Assuming instantaneous distribution, the theoretical alcohol- permille at time zero (7 p.m.) is:  (60 g)/34.8 kg =1.72 g kg-1. The theoretical oxidation occurring in 2 hours is (120 min * 0.0020) = 0.24 g kg-1. At 9 p.m. the expected blood alcohol concentration is (1.72 -0.24) = 1.48 g kg-1. This is exactly what was found, so the statement seems to be correct.

Case History B

1.  According to the ideal gas equation VSTPD * 760/273 = 8 * (752 - 20)/(273+ 20). Isolation of VSTPD  yields the value 7.1793 m3 or 7179.3 litres of oxygen. The survival threshold is FIO2 : 50/(752-20) = 0.0683. The total volume of oxygen available for survival is (7179.3 * (0.2093 - 0.0683) = 1012.28 l of oxygen. The survival period is:

1012.28/(3*0.190) = 1776 min or 29.6 hours.

2.The RQ is 0.83, so for each person the carbon dioxide output per min is (0.19* 0.83) =  0.1577 l STPD min-1.

3.  The theoretical carbon dioxide accumulation amounts to (0.1577*3*1776) = 840 l STPD. The corresponding FICO2 is 840/7179.3 or 0.117 (11.7%) as an estimate.

4. The consequences of CO2 accumulation are CO2 intoxication and CO2 narcosis. Long before the theoretical accumulation should occur, the 3 victims have died in a terrifying state of anxiety by CO2 intoxication.  Humans cannot survive in an atmosphere with 11.7% CO2.

Case History C

 1.        The difference between pK and pH is (9.3 - 7.3) = 2 decades or 102. Thus, we have 100 times as much NH4+ as ammonia in the blood.

2.         12 600/0.46 = 27 391 mmol oxygen/day. RQ = V°CO2 / V°O2 ;

           V°CO2 = 0.83×27.391 = 22.7 mol CO2/day.

 3.        The synthesis of urea in the liver is the major route of removal of NH4+:

2 NH3 + CO2 ----  CO(NH2)2 + water. Thus, NH4+ is eliminated by the use of half a mol of carbon dioxide daily for urea production.

Case History D

 1.        FAO2  = 14.1 kPa/(101.3 - 6.2) kPa = 0.148.

FAN2  = 78 kPa/(101.3 - 6.2) kPa = 0.82.

FACO2 = 1 - (FAO2  + FAN2) = 0.032.

FACO2 = V°CO2/ V°A ;    V°A = V°CO2 2/FACO2

V°A = 660/0.032 = 20 625 ml STPD/min.

The PACO2 is (0.032×95.1) = 3 kPa (22.5 mm Hg). The PaCO2 is assumed to be similar, when tension equilibrium is established; the normal venous mixing can only increase the tension to a small extent. Such a low PaCO2  is a clear indication of hyperventilation.

 2.         V°O2 = V°A  [FAO2 (FAN2/FIN2) - FAO2]

V°O2 = 20.625×[0.2093×(0.82/0.79) - 0.148].

V°O2 = 1.427 l STPD per min.

 3.        R = 660/1427 = 0.46.

This R value is lower than the lowest possible RQ (0.7 by pure fat combustion).

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