Respiratory Exam from 1995
Respiratory Section Exam BME 403B Fall1995 Closed Book
1.(20) Mark True (T)or False(F)
1.1( ) Hyaline membrane disease primarily involves an abnormal thickening of the
alveolar epithelium.
1.2 ( ) The sensor which determines the primary hypoxic ventilatory response is the
carotid sinus.
1.3 ( ) Differences in alveolar and arterial levels of oxygen tension can be explained
by alveolar dead space.
1.4 ( ) Barometric pressure always equals the sum of the partial pressures of the
constituent gases.
1.5 ( ) Expiratory reserve volume can be measured with a spirometer.
1.6 ( ) The partial pressure of oxygen in the lungs will decrease as one rises to the
surace from a depth of 33 feet of water while breatholding (assume negligible
consumption of oxygen).
1.7 ( ) Hypoxia is known to enhance the ventilatory response to carbon dioxide.
1.8 ( ) In exercise ventilation increases due to the elevation of carbon dioxide tension
in the blood due to increased metabolic rate.
1.9 ( ) The slope of the blood buffer line (HCO3 vs pH) changes with hemoglobin
concentration.
1.10 ( ) The compliance of the lungs alone can be estimated from measurements of
lung volume and the difference between pleural and atmospheric pressure.
2. (10)Based on a two element (RC) model of respiratory mechanics, the differential
equation is:
dV/dt = Pm/R - V/(RC)
a.) if R= 2 Cm H2O/ LPS and C =0.2 L/cm H2 O , and inspired airflow is constant at
1.0 LPS what will Pm be at t=2 seconds if V=0 at t=0 seconds.
b) calculate the elastic work of inspiration up to t=2sec.
2. (15) a.)Determine the standard bicarbonate level for state 2 of the graph below:
b.) Classify the respiratory and metabolic acid-base status of states 1-
3.(normal,acidosis,alkalosis)
State Respiratory Metabolic
1 ----------- ---------
2 ----------- ---------
3 ----------- ---------
3.(10)A body plethysmograph consists of a closed box of unknown volume. If a
syringe is used to compresses this volume by 0.1 liters a pressure change of 0.5 mm
Hg is measured. a.) Calculate the box volume. b.) A subject is placed in the box
and holds his breath at residual volume, compressing the volume around the subject by
0.1 liter leads to a pressure change of 1.25 mm Hg. What is the volume occupied by
the subject? Assume Boyle's law holds (PV=constant) atmospheric pressure is 760
mm Hg.
4.(15) For the relaxation pressure-volume diagram of the combined lungs and chest
wall as given below, an inspiration begins at 1 and reaches 2 (to right of lines) and
expiration starts at 2 and returns to 1(left of lines). Identify the components of work
by listing all areas by letter. If no area corresponds, indicate "none".
.
A. Elastic work performed by the inspiratory muscles -----------
B. Elastic work performed by the expiratory muscles-------------
C Total dissipated resistive work during inspiration-------------
D. Total work performed by expiratory muscles(inp+exp)-----------E. Total work
performed by inspiratory muscles(insp+exp)--------
5.(15) The relationship between blood and gas for different R(respiratory quotient) is
shown below for inspiring air. If this individual goes to altitude where the barometric
pressure is 476 mm Hg ,inspired O2 is 21%, inspired CO2is 2%, dry inspired gas.
(a) what is inspired O2 and CO2 partial pressures
(b) show graphically how resultant gas tensions are estimated for an R=3.0 and the
same mixed venous point, circle your estimated operating point.
6.(15) Expired gas is collected for one minute in a balloon. Volume of the collected
gas is 20 liters (saturated with water vapor at room temperature) with a CO2
concentration of 3%. End-tidal CO2 concentration is measured as 5.6%. Room
temperature is 20 deg C (PH2O=17.5mm Hg), body temperature is 37 deg
C(PH2O=47 mm Hg), barometric pressure is 730 mm Hg, and inspired CO2 is zero.
A. Calculate carbon dioxide production rate in liters/min STPD (standard temp. and
pressure, dry). Assume ideal gas law PV/T = constant. If 10 equal breaths were
taken over the collection period, calculate the conductive dead space in BTPS(body
temp, wet)using :
Vcds = VT( Fe -FE )/(Fe-FI)
where VT= tidal volume, Fe = effective (arterial) gas fraction, FE = mixed expired gas
fraction.
You can assume that end-tidal CO2 equals alveolar or arterial tensions.
Formulae:
pV=nRT
PM= R dV/dt + V/C
LaPlace Law P=2T/r
Bohr Formula
VT=Vcds + VA
FEVT=FIVcds+FeVA
Vcds= (Fa-FE)VT/(Fa-FI)
Fa = alveolar , FE = mixed expired , FI = inspired (F=fraction)
Alveolar Equations
PaCO2= PICO2+ 863 VCO2/(f VA)
PaO2= PIO2- 863 VO2/(fVA)
f=breathing frequency
pH=6.1 + log([HCO3]/(0.0301 PCO2))