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40 Cards in this Set
- Front
- Back
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Normally, which is the greater stimulus for respiration: Hupoxia or Hypercarbia
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Hypercapnia
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why is a Bilat Carotid Endarterectomy a dangerous procedure for a pt with COPD?
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Loss of carotid bodies-COPD pts are dependent on hypoxic drive
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Under which conditions will a patient not increase their resp rate in response to hypercapnia?
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anesthetised
intoxicated brain injured |
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According to Samet, ventilation is defined as:
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Movement of CO2 out of the system
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According to Samet, oxygentaion is defined as:
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moving O2 from the atmosphere to tissues
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Under what conditions will a patient oxygenate but not ventilate?
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Apnea test
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Under what conditions will a patient ventilate, but not oxygenate? [At least for a while:)]
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delivery of hypoxic gas mixture
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West Zone I
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PA>Pa>Pv
Airflow greatest in apex Bloodflow worst in apex Pressure in alveoli collapse capillaries, no flow through to veins, no gas exchange(dead space) |
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West Zone II
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Pa>PA>Pv
Good match of blood flow and air Capillary has more pressure than alveoli; alveoli has more pressure than venous flow can proceed, gas exchange occurs here |
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West Zone III
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Pa>Pv>PA
Blood flow greatest in base Alveoli not fully inflated High pressure in capillary collapse alveoli no gas exchange (shunt) |
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what is the normal V/Q ratio?
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0.8
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Define shunt
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Perfusion without ventilation
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Define dead space
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Ventilation without perfusion
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What percentage of normal ventilation is dead space?
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30%
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Dead space or shunt?
1)Pulmonary edema 2)Low cardiac output 3)PEEP 4)Pneumonia 5)Pulmonary emboli 6)Obesity ascites, pregnancy 7)Pneumothorax 8)Pulmonary contusion 9)Positive pressure ventilation |
1)Pulmonary edema-SHUNT
2)Low cardiac output-DEAD SPACE 3)PEEP-DEAD SPACE 4)Pneumonia-SHUNT 5)Pulmonary emboli-DEAD SPACE 6)Obesity ascites, pregnancy-SHUNT 7)Pneumothorax-SHUNT 8)Pulmonary contusion-SHUNT 9)Positive pressure ventilation-DEAD SPACE(opens easiest alveoli-West zone I-with poorest blood flow) |
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A-a Gradient normal or increased ?
1)Diffusion impairment 2)Low FiO2 3)Hypoventilation 4)Right to left shunt 5) V/Q mismatch |
1)Diffusion impairment-INCREASED
2)Low FiO2-NORMAL 3)Hypoventilation-NORMAL 4)Right to left shunt-INCREASED 5) V/Q mismatch-INCREASED |
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Factors shifting Oxyhemoglobin Dissociation Curve to Left
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alkaLOsis
LOw temp LOw 2,3 DPG |
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Factors shifting Oxyhemoglobin Dissociation Curve to the RIGHT
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Right
Increase G 2,3 DPG Hydrogen ion (acidosis) Temp (hyperthermia) |
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At what rate is O2 consumed:
by adults? by peds? |
adults: 2-3ml/kg/min
peds: 6-7ml/kg/min |
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What is the greatest value of the anesthesia machine?
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allows you to rebreathe without wasting gas, O2, humidiity, or heat
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What is normal VO2 (resting , awake)
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250 ml/min
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Name the lung volumes
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Tidal volume
Inspiratory reserve volume Expiratory reserve volume Residual Volume |
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Tidal volume + Inspiratory reserve volume=
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Inspiratory Capacity
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Tidal Volume + Inspiratory Volume Expiratory Volume=
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Vital Capacity
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Expiratory Volume + Functional Residual Volume=
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Functional Reserve Capacity
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Inspiratory Resrve Volume + Tidal volume + Expiratory Reserve Volume + Residual Volume=
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Total Lung Capacity
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What is the normal volume for total lung capacity?
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6 Liters
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Which capacity is most negatively affected by obesity, ascites, pregnancy?
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FRC
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Which capacity is most important for Anesthesia?
Why? |
FRC
Maximize reserve Gen Anesthesia decreases RV Positive pressure ventilation decreases FRC |
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What conditions decrease Functional Residual Capacity?
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Pregnancy
Ascites Neonates General Anesthesia Obesity Supine Position Remeber "PANGOS" |
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Define Closing Volume
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volume needed at end expiration to keep alveoli open
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Define Closing Capacity
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closing volume + residual volume
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What conditions increase closing volume?
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Age
Liver failure Bronchitis (chronic) Obesity Surgery Smoking Remember "ALf BOSS" |
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Does a higher closing Volume indicate increased or decreased gas exchange?
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Decreased gas exchange-some of the volume is used just to keep the lungs open
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What ventilatory changes are seen in the supine position?
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Cephalad shift of the diaphragm
Decreased FRC More perfusion/less ventilation in posterior aspect of lungs |
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What ventilatory changes are seen with anesthesia?
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-Increased RR
-Decreased Tidal Volume -Irregular resp in light anesthesia -Increased airway resistance -Muscle tone favor s collapse -Paralysis results in more collapse -Positive pressure vent increases V/ mismatch -Transudation and shunt from excessive IV fluid adm -Absorption atelectasis with high O2 concentration -Decreased mucociliary flow -Inhibition of pulmonic hypoxic constriction |
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Why is PEEP used in anesthesia?
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To prevent alveoli from reaching state where they cannot be recruited again
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What is the rate of rise for PaCO2 during apnea?
Why do we care? |
6mmHg first minute
3-4mmHg for each subsequent minute Anesthetized pt won't be stimulated to breathe until ETCO2 reaches 45-50 (COPD 60-65) Significant during emergence and apnea test for brain death |
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During hypoxia the patient relies on anaerobic metabolism. what are the physiologic effects?
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Acidosis
Initial excitatory and vasoconstrictive CV (may not be seen under anesthesia) Later, CV depressed and vasodilatory Cardiac arryhthmias, fibrillation, asystoe |
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What are the physiologic effects of hypercapnia?
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Similar to hypoxia
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