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29 Cards in this Set
- Front
- Back
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Hypoxemic failure
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inadequate O2 delivery (lung failure)
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Hypercapnic failure
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respiratory acidosis (pump failure)
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decreased Pi O2
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not enough O2 available - high altitude, airplane
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decreased alveolar ventilation
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increased Alveolar CO2, decreased Alveolar O2
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VQ mismatch
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can be corrected by supplemental O2
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R >> L shunt
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refractory to O2
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Diffusion limitation
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typically see hypoxemia only during exercise - can't meet the faster transit time
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Vd/Vt
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dead space / tidal volume ratio; typically 0.25-0.3 @ rest
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physiologic mechanisms of hypercapnic failure
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Increase in minute ventilation b/c of higher CO2 production or increased dead space; or decreased minute ventilation
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Things that can affect minute ventilation
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central drive, nerve conduction, neuromuscular, chest wall, lung disease, upper airway obstruction
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things that affect central drive
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narcotic overdose, stroke
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nerve conduction
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cervical cord trauma, GBS
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NM
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MG, muscle atrophy
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chest wall
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flail chest, kyphoscoliosis
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lung disease
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asthma, COPD
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Normal blood arterial gases
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ph 7.4/CO2 40/Bicarb 24
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Acute failure
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7.3/55/26 >> high CO2, low pH, not enough time for bicarb to compensate
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Compensated failure
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7.37/55/31 >> high CO2, normalish pH, high bicarb tries to compensate
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acute and chronic failure
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7.25/85/36 >> high CO2, low pH, high bicarb.
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Respiratory drive
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normally CO2 is main driver, but in some COPD pts w/ chronic CO2 retention, the carotid body begins to use O2 as its main driver
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hypoxemic drive to ventilate
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chemoreceptors regulate ventilation based on pH/CO2. If hypoxemia >> see decrease in O2 sat and subsequent increase in vent. So giving pt O2 may decrease their drive to breathe. If ventilated aim for 94-95% sat.
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danger point #1
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don't decrease fraction of inhaled O2 to stimulate respiration
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deconditioning
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patients w/ malnutrition, immobility, long-term ventilation may develop muscle weakness
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Clinical signs of respiratory muscle weakness
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tachypnea, decreased VC, decreased max inspiratory force, ineffective cough
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Respiratory stimulants
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Naloxone (opioid antag), controlled hypoxemia, chemicals (rarely effective)
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assist devices
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negative pressure (iron lung), nasal, face mask CPAP, cycled CPAP (bipap), positive pressure ventilation (standard today)
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PEEP and ventilation
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positive end expiratory pressure - don't let pt exhale the whole way, keeps alveoli open and not collapsed.
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PEEP and FRC
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increasing PEEP increases FRC
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adverse effects of PEEP
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barotrauma if PEEP is too high, decreases venous return and CO (due to increased intrathoracic pressure)
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