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acute respiratory failure (ARF)
ventilation is not adequate to maintain gas exchange and acid-base balance
goals of mechanical ventilation (MV)
physiological
support/manipulate pulmonary gas exchange
increase lung volume
reduce WOB
goals of mechanical ventilation (MV)
clinical
reverse ARF
reverse respiratory distress
reverse hypoxemia
prevent/reverse atelectasis and maintain FRC
reverse respiratory muscle fatigue
allow sedation/paralysis
reduce systemic/myocardial O2 consumption
minimize associated complications
reduce mortality
recognition of respiratory distress
assess LOC
assess appearance and texture of skin
evaluate vital signs
types of ARF
hypoxemic
hypercapnic
causes of hypoxemic ARF
V/Q mismatch
diffusion defects
right-to-left shunt
alveolar hypoventilation
aging
decreased inspired O2
causes of hypercapnic ARF
ventilatory pump failure
CNS defects
neuromuscular defects
increased WOB
manifestations of mild/moderate hypoxemia
tachypnea
dyspnea
pallor
tachycardia
mild HTN
restlessness
disorientation
headache
lethargy
manifestations of severe hypoxemia
tachypnea
dyspnea
cyanosis
eventual bradycardia
eventual hypotension
somnolence
confusion
blurry vision
loss of consciousness
eventual coma
manifestations of mild/moderate hypercapnia
tachypnea
dyspnea
tachycardia
HTN
vasodilation
headache
drowsiness
dizziness
confusion
sweatiness
redness
manifestations of severe hypercapnia
tachypnea → bradypnea
eventual hypotension
hallucinations
hypomania
convulsions
loss of consciousness
coma
causes of CNS disorders
drugs
tumors
stroke
head trauma (cerebral bleed, ↑ICP)
causes of neuromuscular disorders
motor nerve damage
faulty nerve impulse
muscle dysfunction
drugs
thresholds for neuromuscular disorders
MIP ≤ −20 to −30 cmH2O
VC < 10-15 mL/kg
causes of increased WOB
respiratory muscle fatigue
airway obstruction
restriction
severe chest trauma
MIP/NIF
normal range
−100 to −50 cmH2O
MIP/NIF
critical
−20 to 0 cmH2O
MEP
normal value
100 cmH2O
MEP
critical range
< 40 cmH2O
VC
normal range
65-75 mL/kg
VC
critical range
< 10-15 mL/kg
VT
normal range
5-8 mL/kg
VT
critical range
< 5 mL/kg
RR / f
normal range
12-20 breaths/min
RR / f
critical range
> 35 breaths/min
FEV1
normal range
50-60 mL/kg
FEV1
critical range
< 10 mL/kg
PEFR
normal range
350-600 L/min
PEFR
critical range
75-100 L/min
other physiological measurements
PaCO2
PaO2
SpO2
CaO2
PaO2/PAO2
PaO2/FiO2
treatment for arterial hypoxemia
hypoventilation
increase alveolar ventilation
treatment for arterial hypoxemia
decreased V/Q
CPAP
treatment for arterial hypoxemia
intrapulmonary shunt
CPAP
treatment for arterial hypoxemia
diffusion defect
steroids (?)
treatment for arterial hypoxemia
decreased atmospheric pressure (PB)
lower altitude
treatment for arterial hypoxemia
decreased FiO2 (<21%)
oxygen
MV goals
allow pulmonary system to have an adequate level of alveolar ventilation
reduce WOB until cause of RF is treated
restore arterial and systemic acid-base balance to levels that are normal for patient
increase O2 delivery to tissues
prevent complications associated with MV
possible alternatives to MV
supplemental O2 (ie, HFNC)
patient positioning (upright/Fowlers)
medications
resolve cause
benefits of noninvasive positive pressure ventilation (NPPV)
treats acute-on-chronic RF unless CV instability is present
reduces need for intubation
reduces complications of ventilation
shortens hospital stay
reduces hospital mortality rates
benefits patients with ARF associated with cardiogenic pulmonary edema
noninvasive ventilation (NIV)
indications
at least 2 factors present:
RR > 25 breaths/min
pH 7.25-7.30
PaCO2 45-60 mmHg
moderate-to-severe dyspnea with accessory muscle use and paradoxical breathing
noninvasive ventilation (NIV)
absolute contraindications
respiratory arrest
cardiac arrest
CV instability
non-respiratory organ failure
patent tracheoesophageal fistula
inability to protect airway and/or high risk of aspiration
uncooperative patient
facial/head surgery or trauma
noninvasive ventilation (NIV)
relative contraindications
copious/viscous secretions
fixed nasopharyngeal abnormalities
extreme obesity
NIV to MV indications
respiratory arrest
RR > 35 breaths/min
severe dyspnea
PaO2 < 40 mmHg or PaO2/FiO2 < 200
pH < 7.25
PaCO2 > 60 mmHg
hyper-somnolence
impaired mental ability
CV complications
NIV failure