Mechanical Ventilation Basics Flashcards
What is hypoxemia?
PaO2 <80mmHg, severe if below 60
What is hypercapnia?
PaCO2 >45, severe if above 75mmHg
What can cause low FiO2?
high elevation
What can cause hypoventilation?
Drugs such as opioids, benzos, general anesthetics; can result in hypoxemia and hypercapnia
What R to L shunts can lead to hypoxemia?
Pulmonary AVMs, cardiac shunt, hepatopulmonary syndrome; alveoli filled with fluid (puss, blood, edema) results in bypass of lung tissue
How can V/Q mismatch lead to hypoxemia?
Low ventilation to perfusion, COPD, ILD, vascular dz
What neurological disorders can lead to hypercapnia?
Spinal cord injury, GBS, brain tumor, increased intracranial pressure
What thoracic cage disorders can lead to hypercapnia?
trauma, kyphoscoliosis, pectus excavatum
What pulmonary disorders can lead to hyercapnia?
epiglottitis, laryngeal edema, COPD, OSA, ARDS
What are the signs of respiratory failure?
Dyspnea, tachypnea, cyanosis, sweating, use of accessory muscles of respiration, agitation or lethargy, flaring of nostrils, wheezing or crackles, low O2 saturations
Compensation is always in the same direction as what?
the primary disorder
The pH changes in opposite directions to the HCO3 and PCO2 with what?
respiratory disorders
The pH, HCO3 and pCO2 all point in the same direction with what?
metabolic disorders
What is the main purpose for mechanical ventilation?
to augment or replace respiratory system
What does mechanical ventilation provide when there is an oxygenation issue?
provides positive pressure and supplemental oxygen, reduces excessive work of breathing
What does mechanical ventilation provide for ventilation issues?
aids with airway obstruction, increases respiratory rate, assists with respiratory fatigue
What are the types of mechanical ventilation?
Invasive ventilation (intubation) and non-invasive positive pressure ventilation (NPPV)
What are the advantages for NPPV?
improved oxygenation, shorter length of stays in ICU and hospital, improved survival; preservation of upper airway reflexes, improved pt comfort, decreased work of breathing, avoids complications associated with intubation
What are the disadvantages for NPPV?
claustrophobia, unprotected airway; increased workload for practitioner, nasal pressure lesions, inability to suction deep airway, gastric dissension with use of face mask or helmet, delay in intubation
What are the absolute contraindications for NPPV?
cardiac or respiratory arrest and unstable cardiac arrhythmia
What are the relative contraindications for NPPV?
Hemodynamic instability, unable to cooperate, inability to protect airway, active GI hemorrhage, encephalopathy
When are NPPV used in clinical practice?
Acute COPD exacerbations (hypercapnic respiratory acidosis), hypoxemic respiratory failure (COVID, bacterial pneumonia), acute pulmonary edema from cardiac etiology
What are the advantages for intubation?
Decreasing risk of aspiration, allowing ventilation with 100% oxygen, facilitating tracheal suctioning, eliminate need to maintain mask to face seal
What are the disadvantages for intubation?
injury to teeth, throat and/or trachea, risk of improper placement, may increase respiratory resistance, need for advanced training to properly perform, need for specialized equipment
What is an absolute contraindications for intubation?
advanced directive
What are the relative contraindications for intubation?
facial or upper airway trauma, laryngeal edema (burns, anaphylaxis, infections), difficult anatomy, clinician skill set
When are incubations performed in clinical practice?
Acute respiratory failure (oxygenation, ventilation), airway protection (AMS [encephalopathy, drugs, EtOH, seizure], perioperative setting)
What are the settings for mechanical ventilation?
Positive end expiratory pressure (PEEP), FiO2, tidal volume, and respiratory rate
Ventilation = what?
CO2 management
What is PEEP?
aids in alveolar recruitment and improves oxygenation
What is FiO2?
Increases concentration of oxygen and improves oxygenation
What is tidal volume?
amount of air delivered with each breath, will affect ventilation
What is respiratory rate?
frequency of delivered breaths, will affect ventilation
What are the parameters that affect oxygenation?
PEEP and FiO2
What are the parameters that affect ventilation?
RR and TV
What are the risks associated with PEEP?
Too much pressure can result in barotrauma, typically limit PEEP to 15cm H2O; can go higher but you must reduce/sacrifice TV
What are the risks associated with FiO2?
There is such a thing as too much oxygen; higher levels are associated with damage to lung parenchyma; hyperoxia is also associated with increased mortality and increased hospital stay
What are the risks associated with TV?
too large of a TV may result in barotrauma; avoid >10mL/Kg of ideal body weight; in ARDS lung conservation strategy is to reduce TV in order to increase PEEP
What are the risks associated with RR?
Must allow time to exhale; if RR is too quick in patients with prolonged expiratory phases (COPD), auto-PEEP will result (not good)
