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53 Cards in this Set
- Front
- Back
Static Lung Volumes
|
-A: Inspiratory reserve volume
-B: Tidal volume -C: Functional residual capacity -D: Vital capacity -E: Total lung capacity -F: Expiratory reserve volume -G: Residual volume |
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Residual lung volume
-define |
-volume remaining when as much air as possible is removed from the lungs
|
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Expiratory reserve volume
-purpose |
-needed for exercise to oxygenate blood effectively
|
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Minute ventilation
-equation |
V(E) = V(T) x f
Minute ventilation = Tidal volume x frequency |
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Minute ventilation
-effect of increase -effect of decrease |
-inc. = hyperventilation
-dec. = hypoventilation |
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Why is hypoventilation difficult when the patient is awake?
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-CO2 is a potent respiratory stimulant
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Tidal volume
-equation |
V(T) = V(A) + V(D)
Tidal volume = Alveolar volume + Dead space volume |
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Normal ratio of alveolar volume to dead space volume
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-2/3 alveolar volume
-1/3 dead space volume |
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When can dead space volume increase?
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-when breaths are smaller
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Anesthetic effects on ventilation
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-many sedatives, tranquilizers, induction agents, and modern inhalation anesthetics reduce ventilation
-hypoventilation |
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Potent ventilation depressant drugs
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-opioids
-all inhaled agents depress ventilation |
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Pulmonary changes in anesthetized patients
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-dec. lung volume
-inc. intrapulmonary shunt -inc. PaCO2 -dec. PaO2 -dec. tidal volume |
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Pulmonary changes are affected greatly by anesthesia in what sp?
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-horse
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Definitive measure of pulmonary ventilation
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-PaCO2
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PaO2 levels
-useful for |
-determining oxygenation issues
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Values that are not good indicators of ventilator adequacy
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-tidal volume
-minute ventilation -frequency -flow ***PaCO2 defines ventilation |
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Ventilation values that can help to monitor anesthetic depth
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-frequency
-flow |
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Horse v. Dog
-effects of inhaled induction agents |
-more profound hypoventilation in the horse
-decreased PaO2 in larger animals (horse) due to pulmonary dysfunction |
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MAC of inhaled anesthetics for surgical procedures
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about 1.5x MAC
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Spontaneous ventilation
-define |
-patient determines rate, rhythm, and volume of breathing
|
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Controlled ventilation
-define |
-the anesthetist controls rate, rhythm, volume, and flow of each breath
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Mechanical Ventilatory Support
-indications for use |
-depression of respiratory centers by anesthetics
-limitation to thoracic movement -diaphragmatic hernia -ineffective respiratory exchange -thoracic surgery -anesthetic management |
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Limitation to thoracic movement
-examples |
-bulldog w/ smaller thorax
-tight bandaging |
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Reason thoracic surgery is an indication for mechanical ventilator support
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-when the thorax is opened, the lungs collapse from the ribs being unable to be held open
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Mechanical ventilator support
-goals |
-reduce PaCO2
-reduce work of breathing -increase PaO2 |
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Intermittent Positive Pressure Ventilation (IPPV)
-cardiovascular effects |
-Inc. intrathoracic pressure
-Dec. venous return -Dec. cardiac output -Dec. blood pressure -Dec. pulmonary blood flow *All changes proportional to the mean pressure in the thorax |
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Manual IPPV for anesthetized patients
-procedure |
-close pop-off valve
-squeeze rebreathing bag -stop squeezing to allow rebreathing bag to fill with expired gas -periodically open pop-off valve to relieve excess gas |
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What should the gas pressure in the circuit not get above for manual IPPV of an anesthetized patient?
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-30 mL/kg/min
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Mechanical ventilator
-why put the bag in a container with a hole |
-bag movement depends on air flow in/out of the container
-squirt air in = give breath -let air out = expiration |
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Reason to replace rebreathing bag with a bellows for mechanical ventilation
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-easier to quantitate volume
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Mechanical ventilator
-facts |
-ventilator always connected to where the rebreathing bag was located
-ventilator bellows replace rebreathing bag -ventilator squeezes bellows to deliver breath to the patient |
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Switching from a spontaneous breath to the ventilator
-procedure |
-empty rebreathing bag
-close pop-off valve -remove rebreathing bag and attach the ventilator corrugated hose -turn pre-set ventilator on -attach waste gas tubing from waste gas interface to ventilator waste gas outlet -fine tune ventilator adjustments while observing patient |
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Switching from the ventilator to spontaneous ventilation
-procedure |
-reduce minute ventilation to allow PzCO2 to rise and stimulate patient to breath (gradually reduce rate, volume, or both)
-when breathing efforts return, switch the ventilator to off -disconnect corrugated hose and replace the rebreathing bag on breathing circuit -open the pop-off valve -remove waste gas from ventilator and attach to pop-off valve -manually assist ventilation if necessary |
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Ventilator arrangement
-types |
-single circuit
-double circuit |
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Single circuit ventilator
-define |
-all or part of the same gas supplied to the ventilator goes to the patient
|
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Double circuit ventilator
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-gas from the ventilator compresses another device (bag/bellows) that in turn forces gas into the lungs
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Single circuit ventilator
-used primarily for |
-ICU
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Double circuit ventilator
-used primarily for |
anesthesia
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Suggested ventilator settings for dogs
-frequency -tidal volume (mL/kg) -inspiratory time -peak airway pressure (cmH2O) |
-frequency = 8-15
-tidal volume (mL/kg) = 10-15 -inspiratory time = <1 sec -peak airway pressure (cm H2O) = 10-15 |
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Suggested ventilator settings for horses
-frequency -tidal volume (mL/kg) -inspiratory time -peak airway pressure (cmH2O) |
-frequency = 6-10
-tidal volume (mL/kg) = 10-15 -inspiratory time = 1-2sec -peak airway pressure (cm H2O) = 20-30 |
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Reasons patient is not accepting mechanical ventilation
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-anesthetic plane is too light (inc. anesthetic delivery)
-PaCO2 is too high (inc. minute ventilation) -PaO2 is too low (determine reasons for hypoxemia |
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Returning to spontaneous ventilation
-how to |
Allow PaCO2 to rise
-dec. frequency -dec. tidal volume -both Dec. anesthetic depth |
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-ocean bellows ventilator
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Ocean bellows ventilator
-power source |
-pneumatic
|
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Oceanic bellows ventilator
-bellows type |
-ascending bellows
|
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Oceanic bellows ventilator
-controls |
-inspiratory volume
-ventilator rate -flow |
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Oceanic bellows ventilator
-how to control tidal volume |
-flow
|
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Omni-vent ventilator
-power source |
-pneumatic
|
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Omni-vent ventilator
-use |
-common for non-rebreathing systems
|
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Drager Control Ventilator
-control source |
-electricity
|
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Large animal ventilators
-types |
-Surgivet DHV 1000 ventilator
-Drager Control Center |
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Surgivet DHV 1000 ventilator
-facts |
-descending bellows
-pneumatically powered -pneumatically controlled -variable flow control -infinite I:E ratios -can deliver larger tidal volume more rapidly than drager |
|
Drager control cent
-facts |
-descending bellows
-pneumatically powered -electronically controlled -variable flow control -5 I:E ratios -breathing rates <4 breaths/min have a long inspiratory time |