Physiology of Sedation Flashcards

Question

pulmonary gas exchange

Answer 1

Gas exchange occurs between the alveolar air and the pulmonary capillary blood * In close contact * 0.5-2 micrometers Gases move across alveolar wall by diffusion Diffusion is determined by partial pressure gradients (these are equivalent to conc gradients)

Answer 2

amount of gasses passing into lungs

Answer 3

amount of gasses travelling through pulmonary circulation

Answer 4

* Match * Upright person – vary in different parts of the lung * V and Q are greater at the base of the lung, reduce as go up * V:Q varies at different levels in the lung * Differences are less marked in a subject lying flat

Answer 5

* Oxygen and CO2 transported in blood – erythrocytes (red blood corpuscles) * Haemoglobin most imp in O2 transport * Nitrous oxide does not bind to haemoglobin (carried in simple solution in blood)

Answer 6

* Globular protein * MW = 68,000 * 2 alpha & 2 beta protein chains * 4 haeme groups: * Porphyrin ring * Iron atom * Fe reversibly binds O2 * 200-300 Hb molecules / RBC Affinity to oxygen changes at different partial pressures (binds to Fe) (Fetus has Hb-F (fetal form) stronger bind to O2)

Answer 7

* Attached to haemoglobin 97% * Dissolved in plasma 3%

Answer 8

* Little inc in O2 bound to haemoglobin * Amount dissolved is increased in proportion to PO2

Answer 9

Erythrocytes or plasma * As * Dissolved CO2 (10%) * Combined to protein: carbamino compounds (20%) * Bicarbonate ions (70%)

Answer 10

Physiological conditions affecting curve * hypothermia as well as alkalosis will shift the curve to the left and increase haemoglobin affinity to oxygen * easier to harvest oxygen in the lung but harder to give that oxygen away in the tissues. * increase in temperature, acidosis, and increase in 2,3 DPG (diphosphoglycerate) shift the curve to the right reducing the affinity of haemoglobin to oxygen * facilitate haemoglobin to give away oxygen when in the tissue. * 2,3 DPG is an alternative by-product of glycolysis and is part of a feedback loop that can prevent tissue hypoxia.

Answer 11

* As if straight normal air sudden drop in maintenance oxygen with the slowly diffusing N2O, would increase shift towards N2O here it is 50:50 but room air O2 is just 21%

Answer 12

Breathing automatic process controlled by ‘voluntary’ (Skeletal) type muscles * But not autonomic process * Rhythm generated by respiratory centres in the brainstem * can be modified by signals from various ‘sensory’ receptors

Answer 13

* conscious cerebral cortex * peripheral (arterial) chemoreceptors – reduction PO2, inc PCO2 * central chemoreceptors – dec in pH, inc PCO2 (CSF)

Answer 14

* lung stretch receptors detect and inflation and reduce resp centre rhythms

Answer 15

inc in resp centre and breathing rhythm

Answer 16

reduction in O2 delivery to tissues hypoxic, anaemia, stagnant (ishaemic) or cytotoxic

Answer 17

low oxygen concentration, small variations of carbon dioxide have greater effect in pulmonary ventilation, when compared to higher concentrations of oxygen and vice versa. PCO2 and PO2 respiratory control of breathing are intertwined; a change in one will affect the respiratory response of the other.

Answer 18

less O2 reaching alveoli or less O2 diffusion into blood

Answer 19

reduction of O2 transport due to low Hb or ability of Hb to funtion as carrier (e.g. due to CO poisoning)

Answer 20

reduction in transport due to reduced flow

Answer 21

reduction in o2 utilisation by cells

Answer 22

Blue colour of skin and/or mucous membranes Due to \>5gm de-oxygenated Hb/dl of blood (deoxyhaemoglobin) * 1/3 of ‘normal’ (so 5 not 15gm Hb) 2 main forms * Central * Affects whole body, evident in oral tissues * Generally due to dec O2 delivery to blood, hypoxic hypoxia * Low atmospheric PO2 * Dec airflow in airways (obstruction) * Dec O2 diffusion into blood * Dec pulmonary blood flow * ‘shunting’ (‘venous’ blood à arteries) * Peripheral * Due to dec O2 delivery to a localised and ‘peripheral’ part of body * Often due to red blood flow to tissues – stagnant hypoxia * Peripheral vascular diseases e.g. atherosclerosis Pulse oximeter providing early warning of falling PaO2 Alarm set higher than evidence of cyanosis

Answer 23

* Affects whole body, evident in oral tissues * Generally due to dec O2 delivery to blood, hypoxic hypoxia * Low atmospheric PO2 * Dec airflow in airways (obstruction) * Dec O2 diffusion into blood * Dec pulmonary blood flow * ‘shunting’ (‘venous’ blood à arteries)

Answer 24

* Due to dec O2 delivery to a localised and ‘peripheral’ part of body * Often due to red blood flow to tissues – stagnant hypoxia * Peripheral vascular diseases e.g. atherosclerosis

Answer 25

20% short to lungs

Answer 26

80% to body

Answer 27

4 chambers: * -right atrium * -right ventricle * -left atrium * -left ventricle 4 main valves: * -tricuspid * -pulmonary * -mitral (bicuspid) * -aortic

Answer 28

Arterial blood supply to the myocardium is via the right & left coronary arteries and their branches Venous drainage is mostly via coronary veins into the right atrium

Answer 29

Conducting system of heart Electric signal Not all chambers sim Atrium first then ventricles Sino-atrial SA node – pacemaker, define cardiac rhythm * Initiate contraction Atrio-ventricular AV node next * atria contract, fill ventricle Then down to apex of heart * right and left bundle of His

Answer 30

Both Parasym and sym nervous system Parasympathetic (vagus): * Actions on SAN, AVN * Via muscarinic cholinergic receptors * Negative chronotropic and dromotropic effect * slow down pacemaker and inc delay, reducing conduction velocity Sympathetic : * Actions on SAN, AVN, myocytes * Via b-1 adrenoreceptors * Positive chronotropic and dromotropic effect and Positive inotropic effect * E.g noradrenaline, inc HR conduction velocity and contractility

Answer 31

* Ventricular systole: * Isovolumetric contraction * Ejection phase * Ventricular diastole: * Isovolumetric relaxation * Passive filling * Active filling (Atrial systole) * Pressure changes and timing * Volumes * Mechanical events (valves) * Electrical events (ECG)

Answer 32

electrocardiogram ## Footnote P-wave: atrial depolarisation QRS-wave: ventricular depolarisation T-wave: ventricular repolarisation

Answer 33

* Coronary BF is greatest during ventricular diastole * Coronary arteries are compressed during systole * Coronary blood flow is decreased by: * Increased heart rate * Low aortic diastolic BP

Answer 34

* BP = Mean arterial Blood Pressure * CO = Cardiac Output * TPR = Total Peripheral resistance

Answer 35

Stroke Volume x Heart Rate

Answer 36

end diastolic volume (preload) * venous return * HR ventricular contractility after load (TPR)

Answer 37

* Blood returning to right atrium * ‘Push’ forces: * momentum (from systole) * muscle pump (limb muscles; venous valves) * ‘Pull’ forces: * Thoracic ‘pump’ (negative intrathoracic pressure)

Answer 38

* The tension in the heart wall as a result of filling * Determined by end-diastolic volume * Starling’s law of heart * increase EDV then increase stroke volume * Length-tension relationship (overlap of actin and myosin filaments)

Answer 39

compared to a normal contractility for instance by increasing the inotropic activity and thus increasing force and contraction of the cardiac muscle, the heart will increase its end diastolic volume for the same stroke volume. It becomes more efficient pumping blood. However, in heart failure and diseases that limit contractility the opposite is true and the heart becomes less efficient pumping blood

Answer 40

* Force that heart must develop to pump blood against the arterial BP and peripheral resistance * After-load is increased in patients with hypertension: * Increased cardiac ‘work-load’ * Can affect coronary blood flow

Answer 41

In systemic circulation the ideal 120/80 drops at the arterioles level until reaches below 35mm mercury at the venules and the difference between systolic and diastolic disappears * depends on level you measure at what normal readings should be The systolic and diastolic pressure from the pulmonary circulation is much lower

Answer 42

Arterial * External carotid artery * Facial artery * Superficial temporal artery * Radial artery * Accessibility * Continuous monitoring Jugular venous pulse

Answer 43

Blood flow to an organ is determined by various factors – Poiseuille’s Law * Delta P = pressure difference * Radius – large impact * Small change in it – big change in flow

Answer 44

arteriolar radius

Answer 45

local factors - O2, CO2, pH, temp, vascoactive agents sympathetic nerves (alpha and beta effects) hormones - adreanline, ADH, angiotensin II

Answer 46

TPR = the combined resistance of systemic vessels BP = CO x TPR

Answer 47

No change in TPR so no change in arterial blood pressure * Dilation in some vascular beds can occur without changing the mean arterial BP * there is ‘compensatory’ vasoconstriction in other vascular beds

Answer 48

Standing * Additional hydrostatic pressure due to gravity = 80 mmHg * Veins are more compliant than arteries Veins distend = ‘venous pooling’ =Reduced venous return

Answer 49

when loose blood – dec intravascular volume reduce – SV, CO, MAP Inc HR and inc TPR by vasoconstriction

Answer 50

cubital fossa of forearm dorsum of hand

Answer 51

* access * no nearby arteries * no nearby nerves * no joints

Answer 52

* small veins * susceptible to cold/anxiety * mobile veins * more painful

Answer 53

Mainly use CEPHALIC VEIN, BASILIC VEIN & MEDIAN CUBITAL VEIN * cannulate lateral to biceps tendon Larger veins more predictably sited Better tethered to underlying connective tissue

Answer 54

* Big well tethered veins * Less painful * Less venoconstriction

Answer 55

* Access * Potential nerve damage * Potential intra arterial injection * Joint immobilisation

Answer 56

used * median cepahlic (or cubital) vein * cephalic vein * basilic vein other structures * brachial artery * median basilic vein Cannulate lateral to biceps tendon

Answer 57

basilic vein cephalic vein dorsal venous network