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Number one reason for Mechanical Ventilation:
RESPIRATORY FAILURE
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WHAT IS RESPIRATORY FAILURE:
FAILURE OF OXYGENATION, VENTILATION, OR BOTH
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WHAT IS THE TYPICAL PaO2 and PaCO2 at RA for CO2 Retainers?
PaO2<60 and PaCO2>50
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3 TYPES OF RESPIRATORY FAILURE:
1. TYPE 1 ACUTE HYPOXEMIC RESPIRATORY FAILURE
2. TYPE 2 ACUTE HYPERCAPNIC RESPIRATORY FAILURE
3. TYPE 3 CHRONIC RESPIRATORY FAILURE
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PRIMARY CAUSES OF TYPE 1 A HYPOX RF(6 causes)
- 1. v/q mismatch
- 2. shunt
- 3. alveolar hypoventilation
- 4. difusion impairment
- 5. perfusion/diffusion impairment
- 6. decreased inspired O2
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INDICATIONS/SYMPTOMS OF V/Q MISMATCH
- hypoxemia
- dyspnea
- tachycardia
- accessory muscles
- abnormal bs: wheezing, dim, unilateral abnormalities
- whiteout or blackout on cxr
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WHAT PERCENTAGE SHUNT IS NORMAL IN THE BODY?
physiological shunt is 3-5%
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What is a PATHOLOGICAL SHUNT?
abnormal shunts caused by right to left blood fow through holes, or where pulmonary vasculature may be deformed.
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What are examples of Pathological Shunts?
av septal defects, fistulas, atelectatic aveoli
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What is REFRACTORY to supplemental oxygen?
Shunt due to exudate filled alveoli; alveoli not workable. V/Q mismatch WILL respond to oxygen
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What is Alveolar Hypoventilation?
- assoc with Type 1 Hypoxemia
- pt goes into RF and the PCO2 significantly rises to displace the alveolar PaO2 leading to hypoxemia
- drop in RR leads to CO2 increase
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What is Diffusion Impairment:
- assoc with Type1 hypoxemia
- common in pt's where interstitial wall is abnormally thickened which increases diffusion time
- common in emphysema, pt's with abnormal pulmonary vasculature, anemia, pulmonary HTN, pulm edema
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What is Perfusion/Diffusion Impairment:
- assoc with Type 1 hypox
- liver disease, ascites, jaundice, digital clubbing
- platypnea-dyspnea on moving upright from supine
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What is Decreased Inspired Oxygen:
- assoc with Type 1 hypox
- can occur at high altitudes
- barometric pressures decreases which lowers the PaO2-O2
- oxy tank runs out
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What is TYPE2 ACUTE HYPERCAPNIC RF:
- VENTILATORY FAILURE
- abg: Uncompensated Resp Alk
- elevated CO2 displaces alveolar oxygen so hypoxemia may accompany AH RF
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3 MAJOR DISORDERS THAT CAUSE ACUTE HYPERCAPNIC RF:
- Decreased Ventilatory Drive
- Respiratory Muscle Fatigue or Failure
- Increased WOB
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What is Decreased Ventilatory Drive:
- Assoc with Type 2 Hypercapnia
- anything that disrupts the cns breathing mechanisms i.e the spinal cord, phrenic nervers, central and peripheral chemoreceptors.
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Causes of Decreased Ventilatory Drive:
- too much O2 in a CO2 retainer
- drugs/narcotics
- brainstem lesion
- hypothyroidism
- obesity/sleep apnea
- *most causes are REVERSIBLE
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What is Respiratory Muscle Fatigue/Failure:
- caused by neuromuscular diseases such as ALS, MG, GB, polio, MS
- may be reversible or terminal depending on the cause
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Symptoms of Respiratory Muscle Fatigue/Failure:
- drooling
- weakness
- resp fatigue
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What is Increased WOB and is symptoms:
- assoc with Type2 AC Hypercapnia
- caused by copd, asthma excaberations, pneumothorax, rib fxs(broken ribs), pleural effusion, extensive burns
- irritability, mental confusion, *dim bs in young asthmatic may be a bad sign*
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What is Type3 CHRONIC RESPIRATORY FAILURE: A
CO2 RETAINER
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WHAT IS TYPE3 CHRONIC RESPIRATORY FAILURE: B
- 'ACUTE ON CHRONIC'
- CO2 RETAINER WITH AN EXCABERATION
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3 main factors to look for when considering MECHANICAL VENTILATION(intubation):
- 1. ventilatory mechanics (of pt)
- 2. ventilation
- 3. oxygenation
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What is MIF/NIF/MIP:
- max insp force/neg insp force/max insp press **all the same**
- -20 is the red flag: anything less is bad and needs intubation
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INDICATIONS TO INTUBATE:
- MIP< -20
- VC<15 ML/KG OF IBW
- VT<5 ML/KG OF IBW
- RR>30
- VE>10 L
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What levels of CO2 and PH indicate RF:
- CO2 >55 and rising and PH< 7.25 and decreasing
- **can either be acute hypoventilation or acute hypercapnia
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What is the NORMAL PaO2 and the CRITICAL VALUE requiring intubation?
- NORMAL: 80-100
- CRITICAL: <60 with supplemental oxygen
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What is the NORMAL P(A-a)O2 Gradient and what is the CRITICAL VALUE when on supplemental oxygen:
- NORMAL: 2-30 mmhg on RA
- CRITICAL: >450 mmhg on supplemental
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How can PaO2 and Aa gradient indicate shunting, diffusion defects, or v/q mismatch?
When PaO2 is LOW and Aa Gradient is high: indicates gas exchange is not occurring even though a strong gradient is present; find cause of decreased gas exchange
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What is the NORMAL and CRITICAL VALUE of PaO2/PAO2 Ratio:
- NORMAL: 75-95% DIFFUSION
- CRITICAL: <15%
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WHAT IS THE NORMAL FOR A PERSON ON 100% OXY(NRB) AND THE CRITICAL VALUE OF PaO2/FIO2 Ratio:
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What is MECHANICAL VENTILATION:
Using a machine to effective protect the airway and manage ventilation and or oxygenation for PT's unable to do so normally
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3 basic types of negative pressure ventilation:
Iron Lung
Cuirass
Body Suit
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3 Methods of Noninvasive Ventilation:
neg pressure devices
BiPAP
NIPPV
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BiPAP delivers 2 levels of pressure:
IPAP on inspiration(ventilation)
EPAP on expiration(oxygenation)
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Causes of Pressure Rise During Volume Ventilation:
1. Decreasing compliance
2. Increased resistance i.e obstruction in airway, secretions, sputum, blockage in tubing
3. Increased flowrates: HIGH FLOW = HIGH PRESSURE
4. higher set Vt: PRESSURE = VOLUME
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Assist Control Ventilation:
Vent delivers a pre-determined Vt with each inspiratory effort generated by the PT
Uses a sensitivity control(similar to IPPB) set a -2 cmhg
A backup frequency is set to insure a minimum minute volume
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