Final MCQs Physiology - ANZCA Flashcards
PH01 [1986] At an altitude of 14,000 feet (4,200m), ambient pressure is 450mmHg. Breathing air, a normal man has an alveolar pO2 of: A. 40 mmHg B. 50 mmHg C. 55 mmHg D. 60 mmHg E. 80 mmHg
PiO2 = FiO2 × (Pb - 47) PiO2 = 0.21 × (450-47) = 84
PAO2 = PiO2 - (PaCO2 / R) PAO2 = 84 - (35 / 0.8) = 40mmHg (Assuming PaCO2 lower because of hyperventilation)
A is the BEST answer
Disagree. read Nunn ch.16 on altitude. Graph shows how R value changes with altitude, and compares alveolar PO2 and PCO2 values. PCO2 at this altitude (acclimatised) is somewhere between 26 and 30mmHg NB. FIO2 and SVP H20 at body temp constant regardless of altitude (ie. 0.21 and 47mmHg respectively) Thus, substituting -> 84 - (28/0.8) = 49 -> thus B is the best answer
For some rough values to remember (alveolar values)
19000m atm P equals H20 P -> PO2 and PCO2 become zero
>8000m - alveolar PO2 remains relatively stable at about 36mmHg (and PCO2 is about 8!)
6000m - PO2=40 PCO2=18
3000m - PO2=64 PCO2=30
1500m - PO2=80 PCO2=35 (remember these are rough values from the graph)–Spud 15:42, 12 Feb 2006 (EST)
But who can really say what the RR and PaCO2 will be. Also wrt to the graph in Nunn, if you look back a page at the barometric pressure relative to altitude table, these pressure are inconsistent with those in the question (ie the question gives a higher pressure). Isn’t there also some discussion from the UK everest expedition which notes that the PO2 was consistently higher than predicted from the fireplace chairs of those at sea level.
PH02 Peripheral cyanosis appears when: A. Hb exceeds 17G% B. MetHb level exceeds 0.1G% C. SulpHb level exceeds 0.1G% D. MetHb level exceeds 1.5G%
“MetHb and SulfHb produce detectable cyanosis at concentration as low as 2.0 gm and 0.5 gm/dl respectively” Lee et al (eds) Wintrobe’s Clinical Hematology. 10th ed. Philadelphia: Lippincott Williams & Wilkins 1999: p1046-53.
This is further supported by Nunn’s 5th edition p. 293:
“It is generally found that cyanosis can be detected when arterial blood contains greater than
1.5g/dL of reduced haemoglobin, or at an arterial oxygen saturation of 85-90%, although there
is much variation.”
and on p294:
“Non-hypoxic cyanosis has several causes, all of which are rare but worth considering in a patient
who seems cyanosed yet displays no other evidence of cyanosis. Sulphhaemoglobin and, more
importantly, methaemoglobin (at concentrations of 1.5g.dl-1 cause a blue-grey appearance.”
D the best answer
PH03 [1988] [Aug93] [Mar94] If breathe 100% oxygen, marked increase in paO2 occurs in: A. Hypoventilation B. V/Q abnormality C. Moderate diffusion problems D. True shunt
Answer: A, B, and C are true. Only true shunt is not amenable to an increased FiO2.
PH04 In a healthy person lying quietly on his back, the intracranial pressure (referred to the level of the interventricular foramen) is in the range: A. 0-5 cmH2O B. 5-15 cmH2O C. 15-30 cmH2O D. 2-3 mmHg E. 15-18 mmHg
Answer: B
conversion: 10.2cm H2O = 7.3mmHg, so 5-15cm H20 would be 3.5-11mmHg
PH05 [1986] [1987] Normal maternal blood gases: A. pH 7.4 B. Bicarbonate 31mmol/l C. pCO2 50mmHg D. Metabolic alkalosis E. None of the above
A. True: as stated in the Physiology Viva Book the arterial pH is normal at term. This is the one example of complete compensation in normal physiology.
B. False: the HCO3 is lowered
C: False: pCO2 is ~32mmHg due to maternal hyperventilation
D: False: respiratory alkalosis with (complete) metabolic compensation
PH06 [1988] [Mar92] What is the main lung function derangement in pregnancy? A. Decreased tidal volume B. Decreased VC C. Decreased FRC D. Decreased airway resistance E. ? (Related Q PH21)
The respiratory changes in pregnancy include: Increased Respiratory Rate 15% Decreased FRC 20% (decreased ERV & RV) Increased Tidal Volume 30-40% Increased Minute Volume 50% Increased Alveolar Ventilation 70% decreased ariway resistance etc... Disagree(slightly)
Nunn 5th ed Table 13.1
increase TV and alveolar vent 40%, no change RR.
decreased FRC 27%, RV 26%, VC 15%
which gives closest answers 06 -C, and 06b - E
PH06b [Mar93] Typical physiological changes in pregnancy at term, compared to the non-pregnant state include a twenty percent A. Increase in alveolar ventilation B. Increase in tidal volume C. Increase in vital capacity D. Reduction in arterial pH E. Reduction in functional residual capacity
The respiratory changes in pregnancy include: Increased Respiratory Rate 15% Decreased FRC 20% (decreased ERV & RV) Increased Tidal Volume 30-40% Increased Minute Volume 50% Increased Alveolar Ventilation 70% decreased ariway resistance etc... Disagree(slightly)
Nunn 5th ed Table 13.1
increase TV and alveolar vent 40%, no change RR.
decreased FRC 27%, RV 26%, VC 15%
which gives closest answers 06 -C, and 06b - E
PH07 [1986] [Apr96] Which of the following is NOT a normal pressure measurement? A. Pulmonary artery: 25/10 mmHg B. Aortic root: 120/0 mmHg C. Right ventricle 25/8 mmHg D. Right atrium: 5 mmHg E. Left atrium: 3 mmHg
Answer: B. Aortic root pressure typically 120/80mmHg
–BassBoyDave 02:38, 31 Mar 2010 (EDT)
Hang on- the DBP in the RV should be zero, shouldn’t it? The figures I remember are
RAP 5-10/0 RVP 25/0 PAP 25/8 LAP 5-10/0 LVP 120/0 MAP 120/80
So I think B and C are both wrong.
PH08 [1986] [Mar93]
The cardiovascular response to rise in intrathoracic pressure to 40 mmHg include:
1. Reduced venous return
2. Increased peripheral vascular resistance (vasoconstriction)
3. Arterial hypotension
4. Bradycardia
This is obviously a question about the Valsalva manoeuvre. It does not specify the acuity of the change. Taken directly from the Physiology Viva book: There are 4 phases:
pulse rate steady. Small increase in blood pressure (augmented VR).
increased HR. Vasoconstriction. Slight decrease in BP (diminished VR).
Steady HR. Drop in BP.
Increase in BP, with compensatory bradycardia.
Hence, all changes listed do occur.
I’ll go for 1 and 3, probably just 1 if type A.
Nunn 5th ed, fig 31.10 and text explains the changes well, though neglects to mention the reflex bradycardia
secondary to the overshoot increase MAP when the valsalva is released and the VR improves in the presence of increased SVR.
Answer is 1, 2, 3. you only get braycardia with release of pressure…..spooky
–BassBoyDave 02:40, 31 Mar 2010 (EDT)
Indeed, remember the Valsalva diagram-bradycardia only occurs after the termination of increased ITP.
PH09 [1988] Carboxyhaemoglobin: A. Due to CO2 combining with Hb B. Can be 2% in non-smokers C. Can be up to 15% in smokers D. ? E. ?
Answer: B. Nunns seems to suggest levels up to 10% being found in smokers
Clinical Evidence suggests up to 5% is normal in urban non-smokers and up to 15% can be found with heavy smokers [1]
PH10 [1988] Time constant of lung is: A. Resistance x compliance B. Resistance / compliance C. ? D. ?
Answer A: TC = R x C
PH11 [1988] [Aug91] With which of the following vessels are the following results compatible? pO2 15, SO2 26%, O2 5 vols% A. Umbilical artery B. Umbilical vein C. Uterine vein D. ?
Answer: A
Umbilical artery: pH 7.21, p02 = 18, pCO2 = 55, Sa02 = 45%, Ca02 = lOmlldl
Umbilical vein: pH 7.32, pO2 28, pC02 = 40, Sa02 = 70%, CaO2 = 16 mlldl
PH12 [1988] [Mar91] [Mar92] In non-shivering thermogenesis: A. Vessels and muscles of neck are involved B. Perinephric & periadrenal fat C. Interscapular mass D. Gluteal muscles
Brown fat is localised around the adrenal glands, kidneys, nape of the neck, inter-scapula area, and the axillary region.
Note that recently (1995) halothane was shown to inhibit non-shivering thermogenesis (in animal studies) in response to noradrenaline challenge. This is important and may explain why neonatal temperature regulation is lousy under anaesthetic.
With respect to respiration in neonates (as compared to young adult): Which is true:
A. Diaphragmatic respiration
B. O2 consumption (mls/kg) x 3 times that of an adult
C. Specific compliance much the same
D. pO2 is 20 mmHg less than adult (on room air)
E. Larger VD/VT ratio
F. Lack of type I fibers
G. Alveolar ventilation (mls/kg) roughly the same
H. Increased alveolar ventilation to FRC ration
Lung Volumes/Capacities Neonate vs Adult in (mL/kg or mL/kg/min as appropriate) Lower TLC 60 vs 80 "Low end of normal" FRC 30-35 vs 32-50 Same Vt = 6.5 Vd = 2.2 Higher Vm = 220 vs 100 Va = 140 vs 60 Va/FRC ratio = 5:1 vs 1.5:1
O2 Consumption (mL/kg/min) around doubled 7-10 vs 3-4
Blood Gases on room air (mmHg) PO2 68 vs 98 PCO2 34 vs 40 pH "in normal range" PO2 increases to adult levels over childhood, "much of it in the 1st year"
PH13b ANZCA version [2001-Apr] Q105
Pulmonary function values which are significantly different
between normal infants and normal adults include
1. tidal volume as ml.kg-1
2. tidal volume to FRC ratio
3. physiologic dead space to tidal volume ratio
4. O2 consumption as ml.kg-1.min-1
PH13b ANZCA version [2001-Apr] Q105 Pulmonary function values which are significantly different between normal infants and normal adults include
- tidal volume as ml.kg-1 -
- tidal volume to FRC ratio -
- physiologic dead space to tidal volume ratio - false: All ages 0.3 according to Table 84-4 in Miller
- O2 consumption as ml.kg-1.min-1 - true: Infants have a higher oxygen consumption per kg per minute than adults (around 6.0 compared to 3.5ml/kg/min in adults) according to Miller Table 84-4
PH13c ANZCA version [2002-Aug] Q100, [2003-Apr] Q17
Compared to an adult, in the neonate:
A. FRC is a more efficient buffer to changes in partial pressures of inspired gases
B. closing volume in ml/kg is lower
C. oxygen consumption in ml/kg is similar
D. FRC in ml/kg is higher
E. the ratio of alveolar ventilation to FRC is higher
PH13c ANZCA version [2002-Aug] Q100, [2003-Apr] Q17 Compared to an adult, in the neonate:
A. FRC is a more efficient buffer to changes in partial pressures of inspired gases - false
B. closing volume in ml/kg is lower - false: closing volume is higher
C. oxygen consumption in ml/kg is similar - false: higher O2 requirement per Kg
D. FRC in ml/kg is higher - false: FRC is lower per kg
E. the ratio of alveolar ventilation to FRC is higher - true: Using table 84-4 from Miller, ratio in neonate is 385/80 cf 3100/3000 for adults.
PH13d [1997]
Compared to an adult, in the neonate:
1. Subglottis is the narrowest portion of the airway
2. The diaphragm contains relatively fewer type I fibres
3. The brainstem is sensitive to opioid-induced respiratory depression
4. The breathing pattern is sinusoidal with no expiratory pause
(A related but different MCQ is PH24)
?
PH14a [1988] [Aug93] [Apr97] [Jul97] [Apr98] [Jul98] (type K)
Neonatal respiratory system different as:
1. Diaphragmatic breathing
2. Decreased type I fibres in diaphragm
3. Increased sensitivity to opioids
4. Sinusoidal breathing with no expiratory pause
5. Increased chest compliance
Laryngospasm Says: PH14a:
- A - True. “The respiration is irregular and mainly diaphragmatic.” Power & Kam. p 360.
- B - True. “There are also fewer Type I muscle fibres (slow contracting and highly oxidative fibres used for sustained contractions) in the diaphragm and intercostal muscles and hence these respiratory muscles fatigue easily.” Power & Kam. p 359-360.
- C - True. “Yet, the fact that apparent toxicity occurred with a maternal dose as low as 0.63 mg/kg/day of codeine should serve as a reminder that the higher sensitivity of neonates to the CNS-depressing effects of opioids may put some infants at risk even with an apparently small maternal dose.” Pharmacogenetics of Neonatal Opioid Toxicity Following Maternal Use of Codeine During Breastfeeding: A Case–Control Study. Clinical Pharmacology & Therapeutics (2008); 85, 1, 31–35 doi:10.1038/clpt.2008.157.
- D - True. “The respiratory pattern is sinusoidal with no expiratory pause seen.” Asian Intensive Care: problems & solutions.
- E - ? True “Lung compliance increases during the first few hours after birth. Specific compliance is similar in the neonate, infant and adult. The chest wall is very compliant because of the soft rib cage of the infant.” Power & Kam. p 360.
PH14b ANZCA version [2001-Apr] Q134
In an infant
1. the chest wall is more compliant than in an adult
2. the diaphragm lacks type 1 muscle fibres
3. oxygen consumption (in ml.kg-1.min-1) is twice that of an adult
4. anatomical deadspace volume (in ml.kg-1) is larger than in an adult
PH14b Version
1. True
2. False - There are fewer type I fibres, not a lack.
From Kam p359 “There are (also) fewer Type I muscle fibres in the diaphragm and intercostal muscles, hence these respiratory muscles fatigue easily.”
From Miller p2369 “These muscles do not achieve the adult configuration of type I muscle fibers until the child is approximately 2 years old”
3. True - two to three times
4. False - relatively smaller
Reference - Miller 6th ed p 2369
4. is true infant has larger anatomical dead space despite normal total. (Nunn 5th ed, p178)
http://jap.physiology.org/cgi/content/abstract/80/5/1485
Anatomic dead space in infants and children (Abstract)
A. H. Numa and C. J. Newth Division of Pediatric Critical Care, Children’s Hospital Los Angeles, University of Southern California 90027, USA.
In adults, anatomic dead space is 2.2 ml/kg. Because of the relatively large head size of infants and children, we hypothesized that extrathoracic and, therefore, total dead space would be relatively larger in pediatric subjects. Extrathoracic dead space was measured by a “water displacement” technique in 40 patients aged 7 days to 14.2 yr who were intubated with cuffed endotracheal tubes. Intrathoracic dead space was measured by continuous analysis of end-tidal and mixed-expired PCO2 and minute ventilation in 10 patients, aged 18 days to 14.7 yr. Extrathoracic dead space per kilogram decreased exponentially with increasing age, ranging from 2.3 ml/kg in early infancy to 0.8 ml/kg in children older than 6 yr. Mean intrathoracic anatomic dead space was 1.03 ml/kg and was not related to age. The following relationship between total anatomic dead space (DStotal; in ml/kg) and age (in yr) is derived: DStotal = 3.28 - 0.56 [ln(1 + Age)], with r = 0.95 and P = 0.0001. Anatomic dead space is age dependent and is > 3 ml/kg in early infancy.
J Appl Physiol 80: 1485-1489, 1996 –Stmz 21:09, 6 Jul 2008 (EDT)
PH15 [1988] [Mar91] [Aug91] [Aug93]
Neonates:
A. Oxygen stored in brown fat
B. Baroreceptors are more sensitive than in an adult
C. Cardiac output same as adult on a weight basis
D. Heart has less compliance than adult
Answer: D
Brown Fat: contains many fat glubule and many large mitochondria. It is specialised for non-shivering thermogenesis through a higher concentration of thermogenin or uncoupling protein 1, which provides an alternative return route for the proton motive force (H+ gradient) produced by the electron transport chain, uncoupling oxidative phosphorylation and releasing the energy as heat. It consumes more oxygen and has a rich capillary supply, but does not contain oxygen.
Baroreceptors In infants: Baroreceptor responsiveness increase with post conception age in neonates and pre-term infants.
PH16 [1988] [Mar91] [Aug91] P50 is increased by a fall of: A. 2,3 DPG B. ATP C. Temperature D. pH
Decreased pH (ie increased [H+]) causes a RIGHT shift in ODC, which is an increase in P50. The other options cause a left shift.
PH17 [1985] [Aug92]
Regarding the coagulation cascade:
A. Factor XI activates factor X
B. Factor VIII is involved in the extrinsic pathway
C. Factor VII is involved in the extrinsic pathway
D. Factor XIII and fibrinogen together activate the intrinsic pathway
E. Activated IX acts VIII which acts on X
C & E correct
I disagree. IXa and VIIIa combine to form “tenase” which activates Factor X to Xa.
VIIIa levels rise under the influence of IIa (aka Thrombin) by conversion of VIII to VIIIa.
This would only leave C as correct. See good old Wikipedia for details…[1]–Groundhog 01:00, 12 Aug 2008 (EDT)
PH18 Immune mechanisms: which are TRUE? A. IgE activates complement B. IgM involved in wheal and flare C. Ab/Ag complex involved in haemolytic reaction D. ?
Answer: C
PH19 Umbilical artery: A. pO2 .... mmHg B. ? C. ? D. ?
see page 129 West. Respiratory Physiology, 6th Edition
–BassBoyDave 03:02, 31 Mar 2010 (EDT)
but jsut for the record, it’s about 15mmHg