Acute Respiratory Distress Flashcards
Acute Respiratory Failure
defined by physiologic criteria
sudden onset of one or more of the following:
- PaO2 less than or equal to 50 mmHg (on room air)
- PaCO2 more than or equal to 50 mmHg.
- pH is 7.35 or less
a medical diagnosis not a disease (caused by some other issue - like exacerbation of chronic COPD/asthma, a PE > V/Q mismatch)
Two Types of Respiratory Failure
Hypoxemic = PaO2 is 50 mmHg or less
Hypercapnic = PaCO2 is 50 mmHg or greater
Hypoxemic Respiratory Failure: Causes
respiratory issue
cardiac issue
Hypercapnia Respiratory Failure: Causes
- respiratory issue
- CNS issue (such as decrease in ventilation. When ventilatory rate decreases, causes CO2 to rise. Could be caused by something wrong with nervous system like spinal chord injury, drugs like opioids that have caused decrease in respiratory rise in pt > RR to decrease > build up of CO2)
- Chest Wall injury (pneumothorax, chest trauma injury, flail chest > pt is not able to increase ventilatory rate or breaths are shallow > can’t open alveoli > build up of CO2 b/c pt is not taking deep enough breaths and exhaling enough CO2 > hypercapnia)
- Neuromuscular System (Guillain-barre syndrome, MS, lou gehrig’s disease > decrease in pt’s ability to maintain RR so they can expel CO2)
Causes of ARF
Direct:
- smoking inhalation
- near drowning
- aspiration (of one’s own secretion, or aspiration that occurs in drowning)
Indirect:
- toxins
- ischemia
- sepsis
Signs of ARF
Neuro signs first (pt is not getting enough O2 to brain):
- HA
- irritability
- confusion
- increasing somnolence, coma
then:
- cyanosis
- dyspnea
- exhaustion
- tachycardia
- hypotension
- cardiac dysrhythmias
Seen in those w/ right or left HF:
- peripheral edema
- neck vein distention
- hepatomegaly
Major Lung Sounds Heard
- wheezing: caused by constriction or inflammation of the bronchial tree itself
- rhonchi: caused by mucus accumulating in bronchial tree, may clear with cough
- rales/crackles: caused by fluid in alveoli or in the interstitium of alveoli
ARF/ARDS Leads to:
- organ failure
- MODS (multi-organ system disorder syndrom)
- 50% mortality rate
ARF/ARDS: Tx
diuretics - to pull fluid out of interstitium and out of alveoli themselves
V/Q Mismatch: Causes
- absolute shunt, no ventilation d/t fluid (or secretions) filling the alveoli
- V/Q mismatch: ventilation partially compromised by secretions in the airway (small mucus plug > partial compromise (some cells can pick up O2 and some cannot))
- V/Q mismatch: perfusion partially compromised by emboli obstructing blood flow (perfusion issue, clot in pulmonary capillary bed itself > perfusion isn’t going to occur)
- Dead space, no perfusion d/t obstruction of the pulmonary capillary (PE > no perfusion getting to alveoli at all)
Two Types of Shunting
Anatomic Shunt
Intrapulmonary/Absolute Shunt
Anatomic Shunt
blood passes through an anatomic channel in the heart and bypasses the lungs
- blood cells not picking up O2 on the way
- no perfusion, ventilation
- something is causing shunt
Intrapulmonary/Absolute Shunt
- anatomical issue
- blood flows through the pulmonary capillaries without participating in gas exchange
- it is seen in conditions in which the alveoli fill with fluid
- when O2 is given, you do not see improvement in pulse ox or blood gases
*hallmark of shunting is a hypoxemic patient who does not improve with oxygen
ARF: Tx
tx underlying cause (like bronchodilators for asthmatic)
goal:
- maintain adequate CO
- SBP > 90 and MAP > 65
- stable lab values
ARF: Ventilation Problem
secretion or fluid in alveoli or vasoconstriction
pt is unable to ventilate d/t tightly constricted bronchial tree
ARF: Perfusion Problem
pulmonary embolism, or small mini clots in the capillary bed of the pulmonary bed
happens frequently in pts w/ sickle cell anemia
Sepsis
a life-threatening organ dysfunction caused by dysregulated host response to infection
sepsis starts somewhere locally (pneumonia, wound infection, UTI, etc)
result of sepsis = ARF
underlying cause of a lot of ARDS = sepsis (usually from pneumonia)
Septic Shock
subset of sepsis-induced in which underlying circulatory and cellular/metabolic abnormalities are profound enough to substantially increase mortality
persisting hypotension requiring vasopressors to maintain MAP > 65 mmHg and serum lactate > 2 mmol/L despite adequate volume resuscitation
Uses for an Arterial Line?
- put them in pts who are ventilated and want to get serial ABGs (better to do this in existing arterial line rather than continuing to stick pts radial artery)
- titrate vasoactive drugs, treating and titrating drugs according to arterial BP from beat to beat, instead of consistently cycling BP cuff
Goals for Treating Patients w/ ARF
- maintain a patent airway (ET Tube)
- optimize O2 delivery (ET tube and ventilator)
- minimize O2 demand (by breathing for pt, give pain and sedation meds so they aren’t working against vent)
- prevent complications
Meds for ARF
- bronchodilators (if needed)
- corticosteroids (to decrease inflammation of lungs)
- antibiotics (for pneumonia - draw blood and sputum cultures first)
- expectorants (loosen mucus especially w/ pneumonia)
Predisposing Conditions to ARDS
direct: pneumonia (could be aspiration pneumonia)
indirect: sepsis or TRALIs (transfusion related acute lung injuries)
* pt can go into acute respiratory failure b/c of blood transfusion reaction
Types of Pneumonia
CAP: community acquired
HAP: hospital acquired
VAP: ventilator associated
Primary Preventions in the Community to Prevent Pneumonia
flu shot pneumonia vaccine (if they are over 65)
Biggest Pesonnel-Related RF for VAP Development
Handwashing