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44 Cards in this Set
- Front
- Back
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Who discovered nitrous oxide?
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Joseph Priestly discovered oxygen and nitrous oxide
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Who was credited with the discovery of anesthesia?
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Horace Wells
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What was the first inhalation anesthetic discovered?
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Nitrous Oxide
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Why is nitrous oxide used? (3 indications)
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1. Allay anxiety and fear in patients.
2. Nitrous oxide has analgesic properties 3. Continuous supply of high concentration of oxygen |
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What procedures can benefit from use of nitrous oxide?
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Diagnostics (x-rays), Minor procedures (impressions), Periodontal (probing/scaling), Restorative (fillings), Surgical (oral surgery, endo)
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What are RELATIVE contraindications to nitrous oxide use?
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Psyciatric disorders (schizophrenic, bipolar, moderate to severe mental delay)
Drug abuse patients COPD Pregnancy Bowel obstruction |
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What are ABSOLUTE contraindications to nitrous oxide use?
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Inability to use a nasal mask
Inner ear infection or recent inner ear surgery Pneumothorax (75% N2O can double size of air pocket in 10 min) Patient refusal |
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What are advantages to the use of nitrous oxide? (9)
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No special permit is required by the Dental Board
Special monitoring equipment is not mandatory Rapid onset of action and peak clinical effect (onset in <30 sec. Maximal effect in <5 min) No ventipuncture required Rapid reversal of sedation Ability to titrate Analgesic effect NPO is not required (kids, diabetics) No escort is necessary (recover in < 5min, can safely drive after 30 min) |
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What are disadvantages to the use of nitrous oxide? (4)
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Initial set up cost
Nasal mask obstruction Patient cooperation essential Concerns with exposure to waste gasses |
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Where does gas exchange occur in the respiratory tract?
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Respiratory bronchioles, Alveolar ducts, Alveoli
(most important is alveoli) |
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Respiration is under control of the autonomic nervous system. What is the role of the dorsal respiratory group the ventral respiratory group, and the pneumotaxic center?
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Dorsal respiratory group - signals inspiration
Ventral respiratory group - signals both inspiration and expiration during heavy respiration (no signal during quiet respiration) Pneumotaxic center - limits duration cycle of inspiration (short breaths) |
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Respiratory control is in the respiratory center in the brain stem (medulla, pons). What is the difference between direct and indirect control mechanisms?
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Direct is the PRIMARY STIMULUS for breathing and is due to increased CO2 (CO2 + H2O = H+ and HCO3-, and the H+ stimulate sensors)
Indirect is due to chemoreceptors located outside the brain that sense changes in OXYGEN levels in the blood. Carotid bodies at bifurcation of common carotid aa, Aortic bodies along aortic arch. |
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Which mechanism of respiratory control is more predominant in COPD?
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Hypoxia (low oxygen) is sensed by indirect method.
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What is the volume of gas inspired or expired during quiet respiration called?
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Tidal Volume
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What is the inspiratory reserve volume?
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Volume that can be maximally inspired above tidal volume
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What is the expiratory reserve volume?
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Volume that can be maximally expired after normal tidal volume expiration
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What is the volume of gas that remains in the lungs after a maximal expiration called?
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Residual volume
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What is the total volume of gas that can be expired after a maximal inspiration called?
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Vital capacity (IRV + TV + ERV)
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What is the total volume that can be maximally inspired called?
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Inspiratory capacity (TV+IRV)
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What is the volume of gas within the lungs at the end of expiration during normal tidal breathing called?
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Functional residual capacity (ERV+RV)
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What comprises the total lung capacity?
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The entire volume that can be contained by the lungs (IRV+TV+ERV+RV)
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If a patients quiet respiratory volume is 500 mL and 150 mL is trapped in the conducting areas of their lung, what is the alveolar ventilation?
What is their minute alveolar ventilation if they are breathing at a rate of 12 breaths/min? |
Tidal Vol - Dead Space = Alveolar Ventilation
500-150 = 350 mL Alveolar Ventilation x Repiratory Rate/Min = Min Alveolar Ventilation 350 x 12 = 4200 ml/min |
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Some of the gasses that are breathed in never reach the alveoli and remain in conducting areas (trachea, bronchi, bronchioles), what is this called?
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anatomic dead space --> inefficient gas exchange
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What makes up cardiac output?
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Cardiac output = heart rate x stroke volume
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What percentage of normal tidal volume does dead space usually comprise?
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30%
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How do you calculate MAP?
What MAP is necessary for adequate perfusion of the tissues? |
MAP (mean arterial pressure) = 1/3 pulse pressure (SBP-DBP) + DBP
It is the time weighted blood pressure average of the cardiac cycle. MAP of at least 60 mmHg is necesary for adequate perfusion of tissues. |
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If a patients BP is 100/70, what is their MAP?
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(100-70)/3 + 70 = 80 mmHg
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How does nitrous oxide exist at room temperature and ambient pressure? room temp and high pressure?
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Room temp and ambient pressure = gas
Room temp and pressure = biphasic (liquid and gas) |
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What is the receptor for analgesic sedation, respiratory depression, miosis?
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Kappa
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Describe nitrous oxide in terms of absorption, distribution, metabolism, elimination
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Absorption: N2O is inhaled into lungs and absorbed from alveoli into pulmonary capillaries (by concentration gradient)
Disribution: dissolved as a free gas in blood. Metabolism: non in the liver, very insignificant amount in the GI tract Elimination: 99% is eliminated through lungs unchanged |
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What are the effects of nitrous oxide on the CNS?
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Depression of central nervous system and psychomotor impairment
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What are the effects of nitrous oxide on the respiratory system?
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Decreases tidal volume, which is offset by increase in respiratory rate --> overall increased minute ventilation.
Depresses the ventilatory response to hypoxia (important in COPD patients) and high O2 levels further suppress hypoxic drive. |
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What are the effects of nitrous oxide on the cardiovascular system?
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No major physiologic changes
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What are the effects of nitrous oxide on the hematopoietic system?
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Bone marrow suppression
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What are the effects of nitrous oxide on the endocrine, renal, GI, hepatic system?
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No effect
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What are the effects of nitrous oxide on the reproductive system?
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Increased incidence of spontaneous abortions and congenital abnormalities in both females and wives of males chronically exposed.
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What color is used to indicate oxygen cylinders? What pressure is oxygen kept under? What state is it in? What is the difference between large and small cylinders (vol)?
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Oxygen is indicated as Green
Pressure is 2000 psi It is stored as a gas Large cylinder is H = 5500 L Small cylinder is E = 625 L |
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What color is used to indicate nitrous oxide? What pressure is it kept at? What state is it in? What is the difference between large and small cylinders (vol)?
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Nitrous oxide is blue
Pressure is 750 psi It is stores as a liquid/gas Large cylinder is G = 16000 L Small cylinder is E = 1600 L |
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Because the pressure in the cylinder of OXYGEN falls in proportion to the amount used, the remaining amount can be calculated as...
In a E cylinder reading 750 psi, how many L are left? How much time til depletion if using it at a rate of 4 L/min |
# L in a full cylinder x (pressure in cylinder/2000psi) = # L in cylinder
625 L/cylinder x 750psi/2000psi = 234 L Time estimated = # L in cylinder / rate of delivery 234 L / (4 L/min) = 58.5 min |
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Since nitrous oxide is stores as a liquid/gas, the amound left in the cylinder can be determined by ...
What does it mean when the pressure gauge drops? |
Weight of cylinder - weight of an empty cylinder
When pressure drops all the liquid has been converted to gas, usually <20% of original vol remians |
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How much oxygen is used for every cylinder of nitrous oxide
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2.5 cylinders of oxygen for every cylinder of nitrous oxide
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What is the purpose of the pin index safety system vs the diameter index safety system
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Pin index safety system: prevents mix-up of gas cylinders, unique configuration of 2 pins from the yoke for each gas. Can't put the wrong cylinder in the wrong place because it won't line up.
Diameter index safety system: prevents cross-plumping of low pressure hoses to flowmeter because the diameter and threading of the attachments for the oxygen and nitrous oxide hoses are different |
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What is the purpose of the valves, pressure gauges, pressure regulators, flowmeter?
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Vales: open the cylinders
Pressure gauges: measure pressure in the cylinders Pressure regulators: reduce high pressure within the cylinders to a line pressure of about 50 psi. It lies between the cylinders and the flowmeters Flowmeter: measures the flow rate of gases being delivered through the system |
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What is the purpose of the reservoid bag, emergency air inlet valve, nonbreathing valve, oxygen flush valve, oxygen fail safe mechanism, scavenger?
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Reservoir bag: 3L reservoir of gas if pt requires more vol than is being supplied, it also provides a visual monitor that pt is breathing
Emergency air inlet valve: allows intake of air in event vol in reservoir bag is inadequate Nonbreathing valve: prohibits exhaled gas from patient back-flowing into the unit Oxygen flush valve: rapid 100% O2 delivery straight into reservoir bag Oxygen fail safe mechanism: if O2 delivery drops below 50 psi the valve that allow N2O delivery closes to prevent 100% nitrous oxide to the pt Scavenger: scavenges exhaled and excess nitrous oxide gas. |
