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16 Cards in this Set

  • Front
  • Back
Diffusion Limitation typically leads to hypoxemia when?
during exercise
VA =
CO2 Balance Equation: PaCO2 =
- 863 X VCO2/VA
- 863 X VCO2 / VE (1-VD/VT)
causes of Hypercapnic Failure
- Increased VE 2o ↑ VCO2 - (fever, trauma)
- Increased VE 2o ↑ VD/VT - (PE, emphysema)
- Decreased VA (many causes)
Hypercapnic Failure due to Decreased VA
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
Hypoxemic respiratory drive
– 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
Hypoxemic drive to ventilate
- 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
Respiratory muscle weakness
1) Neurological (Guillain-Barre syndrome)
2) Muscular (MG)
3) deconditioning (malnutrition, atrophy)
Clinical signs of respiratory muscle weakness
- 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
treating hypercapnia w/ respiratory stimulants
1) Naloxone (opioid antagonist)
2) Controlled hypoxemia (in proper clinical settings)
3) Chemicals (rarely effective)
treating hypercapnia w/ assist devices
1) (-) pressure (Iron lung, Cuirass ventilator)
2) Nasal/Face Mask CPAP (Continuous Positive Airway Pressure)
3) Cycled CPAP (BiPAP - Bilevel Positive Airway P)
Threshold for tracheal intubation and positive pressure ventilation
usually low pH
Breath initiation / Respiratory Rate in hypercapnia
- Mechanical ventilation technique
– Controlled [Control, SIMV] or Pt-initiated [Assist, PS]
Tidal volume in hypercapnia
- Mechanical ventilation technique
- Volume limit, Pressure limit, and Pressure support level
patient regulation of VE (Spontaneous breaths and Tidal volume) in hypercapnia
- Mechanical ventilation technique
– there is unsupported (IMV) and supported (Assist, Pressure Support)
PEEP = Positive End Expiratory Pressure
- 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