Chapter 16.

Multiple Choice Questions 

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

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

  III. Answers  A, C, D, E are true statements, whereas B is false.

Case History A

 1.        The alveolar air equation states:

R = V°CO2 /  V°O2 = 0.8 = [V°A × PACO2/(PB - 47)]/[V°A (PIO2 - PAO2)/(PB - 47)];

R = PACO2/(PIO2 - PAO2) ; 

PACO2 = 0.8 (120 - 100) = 16 mmHg or 2.1 kPa.

 2.        V°A + V°D = V°E 

 Expiratory ventilation = 5.6 + (0.12* 14) = 7.28 l  STPD per min.

Case History B

1.       V°A  = V°CO2 / FACO2 . 

V°O2 = (5 kJ per min)/(20 kJ per l STPD) = 0.25 l STPD per min.

The Sherpas are assumed to be in respiratory steady state with an RQ of 0.85. Thus, the V°CO2  must be (0.25* 0.85) = 0.213 ml STPD per min as an average. FACO2  is 22/(410-47) = 0.0606.

          V°A = 0.213/0.0606 = 3.52   l STPD per min

          VSTPD *(760-47)/273 = VBTPS *(410 -47)/310

Thus, V°A  is equal to 7.84  l  BTPS per min. The alveolar ventilation measured on the mountain is increased inversely proportional to the PB  

2.       (PB  - 47) mmHg = PAO2 + PACO2 + PAN2

 PIN2 at the sea level is 760 - (100 + 40+ 47) =  573 mmHg

          PIO2 = (PB  -47) 0.2093; 

The simplified alveolar gas equation states:

PAO2= PIO2 - PACO2 or PIO2 = PAO2 + PACO2. 

PIO2 is here at the hypothetical altitude: (30+8)=38 mmHg.

38 = (PB  - 47) 0.2093.

PB = 229 mmHg. 

This pressure corresponds to a somewhat higher altitude than the summit of Mt. Everest (8848 m or 253 mmHg). As a physiological theory, it is possible to ascent further without oxygen.

Case History C

1.       The sum of the reciprocal compliance values for the lungs and the thoracic cage is equal to the reciprocal value of the total compliance (for both elastic systems). Accordingly, the specific standard compliance for the total system (x) is calculated as follows: 

            1/x = 1/1.5 + 1/0.8

            x = 0.52 ml BTPS per Pascal. 

2.   The expired ventilatory volume (V°E ) is equal to the specific total standard compliance multiplied by frequency (f) and input pressure: (0.52 * 10 * 800) = 4160 ml BTPS min-1.

V°A  = V°E   - VD*f;      V°A  = 4160 - 130*10;   V°A =  2860 ml BTPS min-1.

3.    The carbon dioxide output (V°CO2  ) is equal to the V°A  multiplied by  FACO2. Accordingly,  V°CO2  =  2860 * 0.059 =168.7 ml BTPS min-1. 

The ideal gas equation  reads: PV = nRT.

 VSTPD*760/(273oC) = VBTPS*(770-47)/(273+37oC).

V°CO2 =  273/310 * 723/760 * 168.7; V°CO2 = (0.8378 * 168.7) or 141 ml STPD min-1.

4.       The cardiac output is equal to the oxygen uptake divided by the arteriovenous oxygen content difference.  The oxygen uptake is equal to the carbon dioxide output, since the respiratory exchange quotient is 1.

Cardiac output = V°O2  /55 or 141/55 = 2.56 l min-1.

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