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16 Cards in this Set
- Front
- Back
Diffusion Limitation typically leads to hypoxemia when?
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during exercise
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VA =
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VE – VD
VE(1-VD/VT) |
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CO2 Balance Equation: PaCO2 =
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- 863 X VCO2/VA
- 863 X VCO2 / VE (1-VD/VT) |
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causes of Hypercapnic Failure
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- Increased VE 2o ↑ VCO2 - (fever, trauma)
- Increased VE 2o ↑ VD/VT - (PE, emphysema) - Decreased VA (many causes) |
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Hypercapnic Failure due to Decreased VA
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1) Respiratory drive (narcotic overdose)
2) Nerve conduction (cervical cord trauma, Guillain-Barre syndrome) 3) Neuromuscular (MG, muscle atrophy) 4) Chest wall (flail chest, kyphoscoliosis) 5) Lung disease (asthma, COPD) 6) UA obstruction |
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Hypoxemic respiratory drive
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– some severe COPD pts have decreased drive
– problem w/ carotic body receptors – the postivies are it’s a fair default mechanism – the negatives are that there are risks of hypoxemia – Chronic can lead to organ damage and acute can lead to MI or dysrhythmia |
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Hypoxemic drive to ventilate
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- Normal ventilation -> pH & pCO2 via CCs
- hypoxemia ↓’s SaO2 & ↑’s ventilation – the hypoxemic drive is active in some individuals with chronic ↑’d pCO2 – supplemental O2 can be titrated to balance SaO2 & pCO2/pH in some stable COPD patients - ↓’d pO2 increases risk of cardiac death – so ↓’d FIO2 rarely indicated as a respiratory stimulant |
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Respiratory muscle weakness
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1) Neurological (Guillain-Barre syndrome)
2) Muscular (MG) 3) deconditioning (malnutrition, atrophy) |
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Clinical signs of respiratory muscle weakness
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- Tachypnea, Decreasing Vital Capacity, Decreasing Maximum Inspiratory Force, Ineffective cough
- Hypercapnea is a late sign of respiratory failure due to neuromuscular limitations - Support ventilation prior to Resp. Failure |
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treating hypercapnia w/ respiratory stimulants
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1) Naloxone (opioid antagonist)
2) Controlled hypoxemia (in proper clinical settings) 3) Chemicals (rarely effective) |
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treating hypercapnia w/ assist devices
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1) (-) pressure (Iron lung, Cuirass ventilator)
2) Nasal/Face Mask CPAP (Continuous Positive Airway Pressure) 3) Cycled CPAP (BiPAP - Bilevel Positive Airway P) |
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Threshold for tracheal intubation and positive pressure ventilation
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usually low pH
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Breath initiation / Respiratory Rate in hypercapnia
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- Mechanical ventilation technique
– Controlled [Control, SIMV] or Pt-initiated [Assist, PS] |
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Tidal volume in hypercapnia
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- Mechanical ventilation technique
- Volume limit, Pressure limit, and Pressure support level |
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patient regulation of VE (Spontaneous breaths and Tidal volume) in hypercapnia
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- Mechanical ventilation technique
– there is unsupported (IMV) and supported (Assist, Pressure Support) |
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PEEP = Positive End Expiratory Pressure
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- Mechanical ventilation technique
- it sets expiratory pressure and ↑’s FRC, it reduces airway and alveolar collapse, and it is used to increase PaO2 – adverse effects are (1) Barotrauma, (2) Decreased venous return, (3) Decreased CO |