Acute Respiratory Failure (Type I and Type II)
<60 mmHg
Type I
PaO2 on room air hypoxemic failure
>50 mmHg
Type II
PaCO2 hypercapnic failure
88-92%
O2 Target
For chronic CO2 retainers
Type I vs Type II
know which gas is the problemType I (Hypoxemic)
- PaO2 <60 mmHg on room air
- PaCO2 normal or low
- Causes include pneumonia, PE, ARDS, pulmonary edema
- HFNC or CPAP for support
Type II (Hypercapnic)
- PaCO2 >50 mmHg
- pH drops (respiratory acidosis)
- Causes include COPD, neuromuscular disease, obesity hypoventilation
- BiPAP is first-line
In chronic CO2 retainers, target SpO2 88-92%. Too much O2 removes their hypoxic drive.
O2 Delivery and Escalation
Nasal cannula 1-6 L/min for mild hypoxemia
High-flow nasal cannula (HFNC) up to 60 L/min with heated humidified O2
CPAP for oxygenation support (single pressure level)
BiPAP for ventilation support (two pressure levels, blows off CO2)
Intubation if NIV fails, airway is unprotected, or mental status declines
Post-intubation settings guided by ABG and clinical response
Key Values to Memorize
Type I = PaO2 <60
Type II = PaCO2 >50
CO2 retainer = 88-92%
HFNC up to 60 L/min
BiPAP for Type II
Intubate if NIV fails
respiratory failure classification shows up on every CCRN exam
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Practice CCRN QuestionsExam Traps
Type I is oxygenation, Type II is ventilation
Type I (hypoxemic) means the lungs cannot get oxygen into the blood. PaO2 drops below 60 mmHg. Type II (hypercapnic) means the lungs cannot blow off CO2. PaCO2 rises above 50 mmHg. Many patients have both, but the exam wants you to identify the primary problem.
CO2 retainers need 88-92%
Chronic CO2 retainers (typically COPD patients) rely on hypoxic drive for respiratory stimulation. Giving too much oxygen removes that drive and can cause respiratory depression. Target SpO2 88-92%, not 94-98%.
BiPAP for Type II failure
BiPAP provides both inspiratory and expiratory pressure, helping blow off CO2. CPAP only provides one level of pressure and primarily helps oxygenation. Type II failure needs the extra inspiratory support BiPAP provides.
Intubation when NIV fails
If noninvasive ventilation does not improve gas exchange, mental status deteriorates, or the patient cannot protect their airway, intubation is required. Do not delay intubation waiting for NIV to work.
Hypoxic Drive Warning
Chronic CO2 retainer + too much O2 = respiratory depression. Target 88-92%. This is a classic exam trap.
BiPAP vs CPAP
BiPAP for Type II (ventilation problem, need to blow off CO2). CPAP for Type I (oxygenation problem). Know the difference.
Imagine a room with a working ventilation fan but terrible air quality. The fan spins fine (ventilation is intact) but the air coming in has no oxygen. The lungs are moving air but cannot get oxygen across the membrane. This is a problem at the alveolar level.
Now the fan is broken. Air is not moving in and out of the room properly. CO2 builds up because it cannot escape. The room gets stuffy and dangerous. The lungs are not ventilating adequately, so CO2 accumulates.
For chronic CO2 retainers, their body has adapted to high CO2 and now relies on low oxygen as the signal to breathe. If you crank the O2 dial too high, you remove the signal and they stop breathing as hard. Keep the dial at 88-92%.
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