Respiratory pathophysiology 4 Flashcards
The Haldane effect describes how the
oxygen tension in the blood determines the blood’s ability to buffer CO2
Inhibition of hypoxic pulmonary vasoconstriction increases
both shunt and dead space; increased dead space diminishes CO2 excretion and manifests as hypercapnia
Identify the MOST appropriate strategy for mechanical ventilation in the patient with COPD.
a. I:E ratio 1:1
b. FiO2 <50%
c. Respiratory rate 7 breaths per minute
d. tidal volume 10-12 mL/kg
c. respiratory rate 7 breaths per minute
(a way to increase the expiratory time? per Apex)
For patients with COPD, always consider _____ for procedures involving the extremities and the lower abdomen.
regional anesthesia
For COPD patients, do not consider neuraxial anesthesia if the patient requires sensory blockade >
T6
This block should be avoided in patients with COPD.
interscalene blockade b/c it causes paralysis of the ipsilateral hemidiaphragm
For patients with COPD receiving regional anesthesia, be careful of
excessive sedation and ventilatory depression
What gas should be avoided for patients with COPD?
nitrous oxide is associated with rupture of pulmonary blebs–> pneumothorax
Volatile agents impair
hypoxic pulmonary vasoconstriction (>1.5 MAC) and increase shunt
unless shunt is severe, it can be overcome by increasing FiO2
For patients with COPD, select a volatile agent with
a low blood:gas solubility
All halogenated anesthetics are
bronchodilators (sevo and iso are better than des)
Key considerations for mechanical ventilation of the COPD patient:
use a tidal volume of 6-8 mL/kg IBW
use a longer expiratory time
add PEEP (stay alert for dynamic hyperinflation)
slow inspiratory flow
Atelectasis is exacerbated by
muscle relaxants and longer surgeries
A patient with COPD is double stacking. Which interventions will improve this patient’s condition? (select 2)
a. increase inspiratory time
b. decrease respiratory rate
c. disconnect the circuit
d. increase inspiratory flow
b. decrease respiratory rate
c. disconnect the circuit
Dynamic hyperinflation occurs when a
new breath is given before the patient was able to exhale the previous breath fully
this is also known as breath stacking
Risk factors for dynamic hyperinflation include
high minute ventilation
increased airway resistance
reduced expiratory flow (such as COPD)
Consequences of dynamic hyperinflation include
barotrauma
pneumothorax
hypotension
Treatment of dynamic hyperinflation (auto-PEEP) includes
removing the patient from the breathing circuit to allow for the pressure in the lungs to equalize with the atmospheric pressure
prolong expiratory time (increasing I:E ration, reduce RR, reduce flow resistance by using a larger diameter ETT & frequent suctioning if needed)
What can lead to increased airway resistance?
secretions
obstructed ETT
fighting the ventilator
Factors that reduce expiratory flow include
bronchoconstriction
airway collapse
inflammation
How can the cardiac system be impacted from auto peep?
impaired venous return
hypotension
overestimation of CVP & PAOP
All of the following are examples of restrictive lung disease EXCEPT:
a. sarcoidosis
b. cystic fibrosis
c. negative pressure pulmonary edema
d. flail chest
b. cystic fibrosis
Restrictive lung disease is an umbrella term for
a collection of disorders that impair normal lung expansion during inspiration
Areas of restriction include the
pulmonary interstitium
pleura
rib cage
and/or abdomen
Categories of restrictive ventilatory defects include:
acute intrinsic
chronic intrinsic
disease of the chest wall, mediastinum, & pleura
other
What are examples of acute intrinsic disorders that cause restrictive disease?
aspiration
upper airway obstruction
What are examples chronic intrinsic disorders that cause restrictive disease?
sarcoidosis
amiodarone-induced pulmonary fibrosis
Restrictive ventilatory diseases of the chest wall, mediastinum, and pleura include
flail chest
pleural effusion
ankylosing spondylitis
Other examples of restrictive ventilatory defects include
pregnancy
obesity
ascites
_________________ is diagnostic for restrictive lung disease
A FEV1 and FVC <70%
- the FEV1/FVC ratio is unchanged
One of the most significant risks of RLD is
barotrauma
The best ventilatory strategies for RLD include
tidal volume= 6 mL/kg IBW
RR= 14-18 breaths/min
PIP <30 cmH2O
I:E ratio= 1:1
Characteristics of restrictive lung disease include
decreased lung volumes and capacities
decreased compliance
intact pulmonary flow rates
Patients with RLD have reduced ______________ making them more prone to _________________
FRC; rapid arterial desaturation
All of the following reduce the incidence of ventilator-associated pneumonia EXCEPT:
a. oropharyngeal decontamination
b. minimizing the duration of mechanical ventilation
c. limiting sedation
d. proton pump inhibitors
d. proton pump inhibitors
Aspiration most commonly occurs during
anesthetic induction and intubation or within 5 minutes of extubation
Aspiration can lead to
airway obstruction, bronchospasm, impaired gas exchange, and bacterial respiratory infection
Risk factors for aspiration pneumonitis include
pregnancy
trauma
emergency surgery
GI obstruction
GERD
PUD
hiatal hernia
ascites
difficult airway management
cricoid pressure
impaired airway reflexes
seizures
residual neuromuscular blockade
Mendelson’s syndrome is a
chemical aspiration pneumonitis that was first described in OB patients receiving inhalation anesthesia
Risk factors for Mendelson’s syndrome include
Gastric pH <2.5
Gastric volume >25 mL (0.4 mL/kg)
Pharmacologic prophylaxis to prevent aspiration includes
antacids
H2 antagonists
GI stimulants
Proton pump inhibitors
antiemetics
Signs and symptoms of aspiration icnlude
hypoxemia (hallmark sign)
dyspnea
tachypnea
cyanosis
Primary treatment of aspiration includes
tilting the head downward (or to the side)
suctioning the upper airway
securing the airway (if indicated)
applying PEEP
Patients who aspirate must be observed
in the PACU
A patient can be safely discharged to home if they do NOT experience any of the following within ________ of the aspiration event:
two hours
new cough or wheeze, radiographic evidence of pulmonary injury
A-a gradient >300 mmHg
SpO2 decrease >10% of preoperative values on room air
The best method to prevent ventilator associated pneumonia is to
avoid intubation all together
minimize the duration of mechanical ventilation
Aspiration causes three potential problems:
gastric contents enter the airway
gastric contents cause a chemical burn to the airway & lung parenchyma
infectious material enters the airway
What is the result of gastric contents entering the airway?
risk of airway obstruction
What is the result of gastric contents causing a chemical burn to the airway and lung parenchyma?
risk of bronchospasm and impaired gas exchange
What is the result of infectious material entering the airway?
bacterial infection (not all aspiration leads to infection)
Routine use of pharmacologic prophylaxis for patients NOT at risk for aspiration is
NOT recommended
_____________ to reduce the risk of aspiration is NOT recommended
anticholinergics
