Download CPAP (Continuous Positive Airway Pressure)

CPAP
(Continuous Positive Airway Pressure)
Cardiogenic Pulmonary Edema
Case Study
• Call to residence @ 2146
• 76 y/o male, SOB
• On arrival:
• Pt. seated upright in living room
• Conscious, obvious resp. distress, agitated
• Pale, diaphoretic, clammy, audibly congested
• Assessment/Questions/Initial Tx ?
Case Study (cont’d)
• Incident Hx; at rest, abrupt onset, now
worse
• PMHx; MI, CHF/Pulm. Edema, HPT, AAA
repair, Renal Tumor, Rx
• Presentation; sitting upright, tachypneic,
1-2 word dyspnea, ↓A/E bil. with coarse
crackles throughout, now RSCP
Case Study (cont’d)
• Vitals; P 60, Irr, R 36-40, B/P 200/94,
SpO2 76 RA, Skin-Pale/Dia. +++/Cool
• Monitor; Sinus with PVC’s, 12-lead neg.
• Any other questions/info req’d?
• Tx?
Case Study (cont’d)
• O2 - Device, FiO2?
• Position? Why?
• Rx – Drug(s) of choice/availability/benefit
• Directive
• Goals of Tx?
Case Study (cont’d)
• Current options to improve
oxygenation/ventilation?
• NRB mask - benefits/limitations
• BVM - benefits/limitations
• ETT - benefits/limitations
• Other options?
Definitions
• CHF - inability of heart to maintain
forward circulation of blood.
• Most severe manifestation; pulmonary
edema
• Pulmonary Edema - extravasation of fluid
from pulmonary vasculature to
interstitium/alveoli of lungs
Pathophysiological Mechanisms
• Imbalance of Starling forces
• Damage to Alveolar/Capillary barrier
• Lymphatic obstruction/dysfunction
• Idiopathic
Cardiogenic Pulmonary Edema
• Normal fluid shift/removal:
• Opposing forces of plasma oncotic pressure and
pulmonary capillary hydrostatic pressure
• Lymphatics remove excess
• Abnormal:
• Volume in pulmonary veins/left atrial venous
•
•
return exceeds left ventricular output
↑pulmonary venous pressure
↑capillary hydrostatic pressure
Pulmonary Edema (cont’d)
• Pulmonary capillary pressure exceeds
plasma colloidal osmotic pressure
• (Norm. PCWP 8-12 mmHg, Normal Colloidal
Osmotic Pressure 25-28 mmHg)
• Fluid shifts to interstitium
• Lymphatic removal does not increase in
proportion to fluid accumulation
Pulmonary Edema (cont’d)
• Stages:
• ↑Lt. atrial pressure opens/distends small
pulmonary vessels
• Fluid/colloids shift to interstitium
• Continual filtration overwhelms lymphatics
• Fluid accumulates/surround alveoli/bronchioles
(compromises small airways first)
• Increases space between capillaries/alveoli
• Disrupts alveolar membrane-floods alveoli
Pulmonary Edema (cont’d)
• Effects:
– Decreases vital capacity
– Causes abnormalities in gas exchange
– Decreases respiratory volume
– Leads to hypoxemia
Pulmonary Edema (cont’d)
• Vicious cycle ensues:
• ↓CO stimulates sympathetic activity
• Renin-Angiotensin-Aldosterone system
• Catecholamine production:
–
–
–
–
–
–
↑ PVR
↑ MVO2
exacerbates myocardial ischemia
↓ LV filling/emptying/function
Further ↑ pulmonary capillary hydrostatic pressure
More fluid shift
Pulmonary Edema (cont’d)
• Cardiac causes:
• CAD
• Loss of LV muscle/function
• Valvular heart disease
• Decreased diastolic ventricular compliance
• Congenital heart disease
• Myocarditis
• Infectious endocarditis
• ↑ B/P
Pulmonary Edema (cont’d)
• Precipitated by:
• Ischemia
• Dysrhythmia
• Cardiac/extra cardiac infection
• P.E.
• Physical/environmental stress
• Non-compliance/changes to Rx
• Dietary changes
• Iatrogenic volume overload
• Pregnancy
• Hyperthyroidism
Differentials
• ARDS
• Anaphylaxis
• Acute anemia
• Bronchitis
• COPD
• Myopathies
• Pneumonia
• Pneumo
• Shock (septic)
• P.E.
Treatment
• ABC’s
• Improve oxygenation/ventilation
• O2 to keep SpO2 > 90%
• Assist ventilations or provide non-invasive positive
pressure ventilation
• 3 Goals:
• ↓ Preload
• ↓ Afterload
• Inotropic support
Treatment (cont’d)
• Preload reduction:
• ↓’s pulmonary capillary hydrostatic pressure
• ↓’s rate of fluid shift
• Afterload reduction:
• ↑’s CO
• ↑’s Renal perfusion
• Inotropic support:
• For those that won’t tolerate preload/afterload
reduction 2º to hypotension
Nitroglycerin
• Vasodilator
• Used with normotensive/hypertensive
patients
• Most effective, predictable and rapidacting Rx available for preload reduction
• Often occurs within 5 min.
• Usually with some afterload reduction as
well
Nitroglycerine (cont’d)
•
•
•
•
↓’s MVO2 by ↓’ng workload
↑’s coronary blood flow
↑’s forward blood flow
↓’s pulmonary hydrostatic
pressure/pulmonary congestion
• SL spray:
• Onset 1-3 min.
• Half-life 5 min.
Furosemide
(Peterborough Region Only)
• Long-standing mainstay of therapy
• Thought to have two physiological effects:
• Immediate venodilation
• Diuretic affect
• May in fact be more harmful than
beneficial
• Move away from use in many prehospital
services
Morphine
(Peterborough Region Only)
• Third drug in “classic” treatment
• Again, thought to have two major benefits:
• Preload/Afterload reduction through vasodilation
• Anxiolytic/Analgesic effects
• No sound evidence supports morphine-mediated
•
•
preload reduction
Recent studies show morphine use an
independent predictor of mortality
Use has declined both in-hospital and
prehospital
Non-invasive Ventilation
• Delivery of ventilatory support without
need of invasive artificial airway
• Will often eliminate the need for
intubation/tracheostomy
• Benefits:
• Easier to wean off ventilator
• Preserves normal cough/swallowing/speech
mechanisms
NPPV (cont’d)
• Two methods:
• BiPAP (Bilevel Positive Airway Pressure)
• CPAP (Continuous Positive Airway Pressure)
CPAP
• Delivered by nasal or face mask
• Pt. breathes through mask against a
continuous positive a/w pressure
• Can be delivered by either volume or
pressure controlled ventilator
• Delivers set pressure with each breath,
maintained throughout the respiratory
cycle
CPAP (cont’d)
• Mechanism:
• Increases gas exchange 2º to increased alveolar
ventilation
• Prevents alveolar collapse during exhalation by
maintaining a positive intra-alveolar pressure
• ↑’s intrathoracic pressure, reducing
preload/afterload and improving cardiac output
CPAP (cont’d)
• Benefits:
• Reduces need for intubation
• Pt. saves energy otherwise spent trying to reopen
collapsed alveoli
• ↓’ WOB: improves alveolar ventilation while
simultaneously resting respiratory muscles
• ↓’s metabolic rate/substrate need to fuel
respiratory effort
CPAP (cont’d)
• Advantages:
• Avoidance of intubation-related trauma
• Decreased incidence of nosocomial pneumonia
• Enhances pt. comfort
• Shorter duration of ventilator use/facilitates
weaning
• Decreased hospital stay
• Decreased costs
CPAP (cont’d)
• Usage:
• Currently utilized primarily in-hospital setting and
by critical care EMS systems
• Also used in-home
• Wide-scale EMS use previously limited by
cost/complexity of technology
• Newer technology and sig. reduced costs lend to
increased use pre-hospital
• Numerous systems incorporating CPAP as standard
for pulmonary edema therapy