Physiology (Special) Flashcards
What is the normal length of pregnancy ?
40 weeks
Physiological changes resulting from pregnancy?
- Changes aiding oxygen delivery
- Increase in uterine blood flow
- Protecting against blood during delivery
- Accommodation for enlarged uterus
CVS changes in pregnancy?
- CO increases by 50%
Characteristics of changes in cardiac output in pregnancy ?
- Majority of changes in the 1st trimester
- Increase of 30% by 12 weeks
- Peaks at 28 weeks at 50%
- Increases in CO is due to increase in SV
- May rise by 45% post-delivery
- Increase may occur with uterine contraction
- Risk of decompensation with cardiac history
Characteristics of changes in SV in pregnancy ?
- Increased by 35%
Characteristics of changes in HR in pregnancy ?
- Increased by 25%
Other changes in pregnancy include?
- Decrease in SVR
- Reduction in BP (SBP -10% & DBP-20%)
- ECG - LAD, ST-depression, flat T-wave
- Aorto-caval compression supine
Haematological changes?
- Anaemia of pregnancy (Plasma > RBC )
- RBC volume increase by 20%
- Plasma volume increase by 45%
- Increased WCC
- Increased fibrinogen and clotting factors
- Factor XI & XIII do not increase
- Decreased platelet count
- Reduced fibrinolysis
Respiratory changes?
- Increased by 15%
- RR stimulated by progesterone - CO2
- Occurs in the 1st trimester
- TV increases by 35%
- FRC decreased by 20% at term
- Reduced chest wall compliance
- Reduced CO2 + Resp alkalosis
- Increase 2,3-DPG
- Airway mucosal oedema
- Increased breast size
Respiratory changes?
- Increased by 15%
- RR stimulated by progesterone - CO2
- Occurs in the 1st trimester
- TV increases by 35%
- FRC decreased by 20% at term
- Reduced chest wall compliance
- Reduced CO2 + Resp alkalosis
- Increase 2,3-DPG
- Airway mucosal oedema
- Increased breast size
Renal and acid base changes ?
- Increased plasma flow + GFR by 50%
- Increased urea & creatinin clearance
- Glycosuria & proteinuria
- Reduced plasma osmolality
- Increased bicarbonate excretion
Endocrine and metabolic changes ?
- Increased size of pituitary gland
- Increased TBG, thyroxine & triiodothyronine
- Free thyroxine index is unchanged
- Increased insulin production - Resistance >
- Maternal hyperglycaemia
What substances do not cross the placenta?
- Insulin
- Transfer occurs via diffusion
Gestational diabetes?
Increased maternal blood sugar leads to increased fetal insulin production leading to fetal hypoglycaemia
GI & Heptaic changes?
- Cephaled displacement of stomach by uterus
- Increased intragastric pressure
- Decrease LOS tone - Risk of reflux
- Delayed gastric emptying
- Elevated LFTs
- Elevated ALP due to placental production
- Reduced protein synthesis by 25%
Neurological changes?
- Reduced volume of epidural space
- Increased sensitivity to opioids & sedatives
Pharmacokinetic changes?
- Increased volume of distribution will result in prolonged elimination half-life of many drugs
- Reduced plasma cholinesterase levels
Pharmacodynamic changes ?
- Reduced MAC
- Reduced dose of drugs
Changes in the placenta?
- Increased in to 10% of cardiac output
- Uterine blood flow increases from 50 to 700ml/min
Draw a schematic of fetal circulation?
Saturation at various point are shown in the image
Describe the fetal circulation?
- Deoxygenated blood arrives the placenta via the Uterine Artery (45%)
- Oxygenated and returned to fetus via umbilical vein (85%)
- About 60% of blood bypasses liver via ductus venosus
- Streams with venous blood from the body in the IVC & returns to LA via Foramen Ovale
Neonatal physiology at birth?
- At birth cessation of placental flow after clamping of cord
- Reduction in PVR + commencement of resp
- Blood flows through the lungs due to reduction in PA pressures and PVR
- Increased pressure LA > RA - Functional closure of FO
- Pressure in aorta increased as UV are clamped
- Increased SVR and reverse flow - Aorta to pulmonary artery via patent ductus arteriosus
What is oxygen consumption at rest ?
Approximately 250mls/min
What is oxygen consumption during exercise?
Approximately 4000mls/min
What is BMR ?
This is the amount of energy that is produced from breakdown of food per unit time. It is usually 40 Kcal/m-2/hr
What is the Metabolic Equivalent (MET)?
This is the metabolic demand of activity
What is oxygen debt?
This is a period of high oxygen consumption after a period of exercise. It is used to compensate for oxygen deficit during exercise which cause accumulation of lactic acid.
What is VO2 max?
The maximal oxygen uptake achievable for an individual. It is limited by cardiovascular factors and increases with increasing fitness
What is the anaerobic threshold ?
This is the point at which oxygen supply can no longer meet demand and thus energy production shifts from aerobic to anaerobic
What is the pasteur point?
The partial pressure of oxygen below which oxidative phosphorylation cannot occur. This is 1mmHg
What are the respiratory changes during exercise?
- Increase TV & RR (Minute volume)
- Ventilation increased due to stimulation of respiratory center from motor cortex and proprioceptors from moving limbs
- PO2 at mitochondrial level is 20-30mmHg with extreme exercise
What are the CVS changes during exercise?
- Cardiac output increases 5 folds
- Increased venous return (Increased muscular tone and decreased intrathoracic pressures)
- Peripheral vascular resistance falls due to accumulation of lactic acid and CO2
- Increase HR, SV and SBP
- Increased pulse pressure
Regional blood flow?
Read it - Exercise physiology
What is the body’s response to high altitudes?
- Hyperventilation
- HPV
- Shift of OHDC to the left
- Polycythermia
- Renal compensation
- Increased cardiac output to increase DO2
- Activation of RAA system + Na retention
- Pulmonary oedema due to reduced hydrostatic pressures and hypervolaemia
