Respiratory Flashcards
What is the purpose of ventilation?
The purpose of ventilation is to remove CO2
What are the two components of minute ventilation?
Alveolar Ventilation and dead space ventilation
What is minute ventilation driven by?
PaCO2 and pH
What is the ratio of the volume of dead space to tidal volume that predicts mortality?
0.6 in ARDS
How do calculate the P/F ratio?
PaO2/FiO2
Criteria for weaning off the ventilator
- CLINICAL: patient is awake, able to take spontaneous breaths, and arterial oxygenation is acceptable
- ARTERIAL OXYGENATION is acceptable: PaO2 >80mmHg on FiO2 <= 40%
What is SBT? Describe the process
Done daily for over 30 min where the patient is allowed to breath through the ventilator with minimal PEEP. The patient will determine the respiratory rate and minute ventilation. If ABG is acceptable (PaO2 > 80mmHg, with acceptable pH), then patient is ready for extubation.
What is RSBI?
Rapid shallow breathing index. RSBI = RR/Vt in L. RSBI < 105 = patient is ready for extubation.
What are the two effects of mechanical ventilation on cardiac performance?
Decrease preload, decrease afterload
How does mechanical ventilation decrease preload? (3)
- Decreases the pressure gradient for venous inflow into the thorax
- Reduces the ventricular distensibility, which reduces the LV filling during diastole as compliance is compromised
- Compressing the pulmonary veins, thus increasing right heart afterload, possibly to the the extent of RV dilatation leading to ventricular interdependence
How does mechanical ventilation decrease afterload?
Positive pressure ventilation decreases afterload by augmenting the pressure gradient between left ventricle and extrathoracic outflow tract (Decreases left ventricular transmural pressure)
When should you consider tracheostomy?
- Those who do not repeatedly pass SbT
- High likelihood of prolonged mechanical ventilatory support
What are the complications of tracheostomy?
- Tracheal stenosis
- Ventilator associated Pneumonia
- Prolonged ICU stay
3 characteristics of ARDS
- Acute onset (<1 week of clinical insult)
- Bilateral chest infiltrates on chest x-ray
- Respiratory failure not explained by cardiac failure or fluid overload
How to protect the lungs when the patient has a diagnosis of ARDS?
- Limit lung volumes to 6mL/kg (predicted by body weight)
- LImit pulmonary plateau pressure to 30 cm H2O
- Use PEEP to limit FiO2 to 60%
- Transient levels of PEEP to recruit additional alveoli
How do you diagnose VAP? (4)
Evidence of pneumonia after 3-5 days of mechanical ventilation
1. Fever.
2. Increased WBC
3. Purulent sputum production
4. Infiltrate on CXR
A 50-year-old woman undergoes a laparoscopic sigmoidectomy for recurrent diverticulitis. Case was notable for 1-L blood loss but patient remained hemodynamically stable. One unit of packed red blood cells (pRBC) was started in the operating room before transfer to the postanesthesia care unit (PACU). Patient was kept intubated. However, she was noted to be increasingly hypoxic on the pulse oximetry. Arterial blood gas (ABG) showed hypoxemia with PaO 2 of 75, and chest x-ray showed diffuse pulmonary infiltrates. What is the crucial next step?
A.
Increase FIO2
B.
Increase positive end-expiratory pressure (PEEP)
C.
Stop the blood transfusion
D.
Intravenous corticosteroids
E.
Administer diuretics
Correct answer: C.
Patient likely developed transfusion-related acute lung injury. With this suspicion, transfusion should be immediately stopped, and continue respiratory and hemodynamic supports as indicated.
A 24-year-old woman is admitted to the intensive care unit (ICU), with concern for acute respiratory distress syndrome secondary to urosepsis. She is 165 cm and 55 kg. Her ventilator settings are as follows: pressure control ventilation mode, FIO 2 60%, positive end-expiratory pressure (PEEP) 8, peak inspiratory pressure (PIP) 30, tidal volume 500, respiratory rate 16. If current ventilator settings continue, what increased risk is the patient under?
A.
Barotrauma/volutrauma
B.
Pulmonary edema
C.
Pneumonia
D.
Mucous plugging
Correct answer: A.
For acute respiratory distress syndrome (ARDS), low tidal volume ventilation (<6 mL per predicted body weight) has been shown to be effective and reduces mortality. For this patient, the tidal volume should be in the 300s.
A 58-year-old man with history of chronic obstructive pulmonary disease (COPD) is admitted to ICU with respiratory failure. He has been intubated for 6 days. He undergoes a spontaneous breathing trial this morning. Patient is on minimum sedation responding appropriately and ventilator settings are minimal. But patient becomes increasingly tachypneic with low tidal volumes toward the end of the trial. What is the most logical next step?
A.
Stop daily spontaneous breathing trials (SBTs)
B.
Trial of extubation
C.
Toilet bronchoscopy
D.
Steroids
E.
Continue daily SBTs
Correct answer: E.
In the scenario above, patient failed SBT due to tachypnea, but otherwise appears to be close to being extubated. Thus with continued exercise through SBT, patient should be able to get strong enough to be weaned off the ventilator completely.
What are the indications for a tracheostomy?
- Prolong intubation
- Facilitation of ventilator support/weaning
- For managing secretions more efficiently
- Upper airway obstruction
- Inability to intubate
- For head and neck surgery
- Airway protection for TBI or neurologic disease
What are the 5 indications for intubation and ventilation?
Unable to protect airway
Excessive WOB
Progressive hypoxemia (PaO2< 55mmHg despite supplemental O2)
Progressive acidosis (pH<7.3 and PCO2>50)
RR > 35
What are the 2 associated CXR findings?
- Westermark’s sign (wedge-shaped area of decreased pulmonary vasculature
resulting in hyperlucency) - Opacity with base at pleural edge from pulmonary infarction
What is a saddle embolus
PE that “straddles” the pulmonary artery and is in the lumen of both the right
and left pulmonary arteries
What is Mendelson’s syndrome?
Chemical pneumonitis secondary to aspiration of stomach contents (i.e., gastric
acid)
What are the most common cause of fever in the first 48 hours
Atelectasis
Why give supplemental O2 to a patient with pneumothorax?
Pneumothorax is almost completely nitrogen—thus increasing the oxygen in the
alveoli increases the nitrogen gradient and results in faster absorption of the
pneumothorax!
