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Causes of respiratory acidosis!
- Parenchymal lung problems
- Airway disease
- Pleural abnormalities
- Chest wall abnormalities
- Nuromusculars disorders
- Central nervous system
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Causes of respiratory alkalosis!
- Hypoxia with compensatory hyperventilation
- Parenchymal lung disease
- Medications (salicylate, xanthines, analeptics)
- Mechanical ventilation
- Central nervous system disorders
- Anxiety
- Metabolic problems
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Metabolic acidosis
These patients are often struggling to lower their PaCO2 to acheive some degree of hyperventilation to compensate for the metabolic acidosis
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Permissive Hypercapnia
- pH can not be higher than 7.1
- Oxygenation must be maintained
- May have to sedate patient
- Can give Bicarb to help bump pH up
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Appropriate suction levels for adults!
-100 to -120 mm Hg
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Appropriate suction levels for children!
-80 to -100 mm Hg
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Appropriate suction levels for infant!
-60 to -100 mm Hg
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Indication for suctioning
- Labored breathing
- Increased RR
- Bilateral breath sounds
- Seeining secretions in tube
- Feel chest
- Increased Raw PIP
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Hazards and complications for suctioning
- Decrease in dynamic lung compliance and functional residual capacity
- Pulmonary atelectasis: reduction of lung volume
- Hypoxia or hypoxemia
- Tracheal or bronchial mucosal trauma
- Cardiac or respiratory arrest
- Bronchoconstriction or bronchospasm
- Pulmonary hemorrhage or bleeding
- Elevated intracranial pressure
- Cardiac dsrhythmias
- Hypertension
- Hypotension
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3 methods of improving oxygentation
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Mean airway pressure
- Is the average pressure above baseline during a total respiratory cycle
- As Paw increases, the PaO2 increases
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Factors that affect mean airway pressure during positive pressure ventilator!
- PIP
- PEEP
- I:E
- Respiratory rate
- Flow
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Paw is a major determinant of oxygenation in patients with ARDs because...
It affects mean alveolar pressure and alveolar recruitment and therefore oxygenation
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Goals of PEEP and CPAP!
- Enhance tissue oxygenation
- Maintain a PaO2 greater than 60 mm Hg and SpO2 at least 90%
- Recruit alveoli and keep them open
- Restore FRC
- Keep FiO2 low as possible
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PEEP
On a ventilaror, invasive, set rate
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CPAP
Non invasive, spontaneously, one pressure
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Devices for PEEP/CPAP
Mask
- Full face mask
- Nasal mask
- Nasal pillows
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Rules when using a mask device for PEEP/CPAP!
- Patient must be able to protect airway
- Patient must be able to support WOB
- Maintain normal PaCO2
- Have a PaO2/FiO2 ratio greater than 200 mm Hg
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Hazards when using a mask device for PEEP/CPAP!
- Aspiration
- CO2 retention
- Increased WOB
- Skin necrosis
- Cerebral hemorrhage
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Devices for PEEP/CPAP
Nasal
- Nasal prongs
- Premies longer
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Problem win using a nasal device with PEEP/CPAP!
Lose pressure through open mouth
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Hazards when using a nasal device for PEEP/CPAP!
- Gastric distension
- Pressure necrosis
- Swelling of nasal mucosa
- Abrasion of the posterior pharynx
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Devices for PEEP/CPAP
ET/Trach
- Used for vent weaning
- Cannot protect airway
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Physiologic or low PEEP ranges!
- 3 to 5 cm H2O
- Help preserve a patients normal FRC ranges
- Few complications
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Therapeutic PEEP ranges!
- PEEP is 5 cm H2O or greater
- Used to treat refractory hypoxemia
- Greater than 15 cm H2O are only benifical to ARDs
- High levels have many side effects
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Optimal PEEP ranges!
- Vary with patients
- Most benefits with fewest side effects
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Indications for PEEP
- Bilateral infiltrates on chest radiograph
- Recurrent atelectasis with low FRC
- Reduced lung compliance
- PaO2 less than 60 mm Hg on FiO2 greater than .5
- PaO2/FiO2 ratio less than 200 for ARDs and less than 300 for ALI
- Refractory hypoxemia: PaO2 increases less than 10 mm Hg with FiO2 increase of .2
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P(A-a)O2 (mm Hg)
Big is bad
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Contraindications for PEEP
- Hypovolemia
- Large untreated pneumothorax
- Tension pneumothorax
- Incresed intercranial pressures (ICP)
- Emphysema (use low level of PEEP)
- Unliteral lung disease
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PEEP and suctioning
- use a closed system
- PEEP valve on ambu bag
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When to wean PEEP
- Patient need a good PaO2 on less than 40%
- Patient needs to be hemodymanic stable
- Some improvement in lung condition
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Adverse effects of PPV
- Increased thoracic pressure
- Decreased Cardiac output due to decreased vessel filling due to increased vascular pressure
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PEEP has the greastest effect on...
- Mean airway pressure
- Cardiac output
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Increased pulmonary vascular resistance
Too much peep can over stretch and pulmonary capillarily become smaller
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Decreasing the effects of PPV by changing
- Mean airway pressure (Paw)
- Inspiratory flow
- I:E ratio
- Inspiratory pause
- PEEP
- SIMV
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Fast flow during PPV
Decreases Paw but increases PIP and uneven distrubution of ventilation
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Slow flow during PPV
Increased WOB and causes auto PEEP because not enough E time
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I:E ratio with PPV
Fewest PPV side effects with a short I time and a longer E time
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Inspiratory pause during PPV
Helps improve oxygenation and gas distrubition but increases I time and Paw
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PEEP during PPV
- Restore FRC
- Recruit alveoli
- Increase Paw too much sometimes
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SIMV with PPV
Decrease in volume decreases pressures and Paw
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The benifits of decreased Paw
(Fast flow)
- Reduced risk of batotrauma
- reduced risk of cardiovascular effects
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The hazards of decreased Paw
(Fast flow)
- Uneven distribution of gas
- Decreased PaO2
- Increased PaCO2
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The benefits of increased Paw
(Slow flow)
- Increased alveoli ventilation
- Recruitment of alveoli
- Better gas distrubition
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The hazards of increased Paw
(Slow flow)
- Decreased cardiac output
- Decreased O2 transport
- Increased risk of barotrauma
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Effects of PPV on ICP
- Decreased BP and cerebral blood flow
- Resp alkalosis to decrease swelling
- CO2 25-35
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Effects of PPV on Renal system
- Decreased renal blood flow
- Decreased urine output
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Factors that decrease urine outptut
- PaO2 less than 40
- PaCO2 greater than 65
- Impaires renal function
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Effects of PPV on GI systems
- Decreased blood flow to GI
- Gastric mucosa ischemia, which can increase risk of bleeding and gastric ulcers
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PPV can alter cerebral perfusion by...
Causing a decrease in cardiac output and mean arterial blood pressure or by causing an increase in CVP, which can cause an increase in intracranial pressure
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Shunting
- Perfusion without ventilation
- Normal person has a 2 to 3% shunt
- Greater than 30% patient is at risk for death
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