Daily assessment of mechanically ventilated patients

Question 1

Specifically, for different modes of ventilation, it is important to check different parameters:

• In volume assist control, check peak pressure and plateau pressure.
• In pressure assist control and pressure support, check peak tidal volume and minute ventilation.
• When patients are breathing spontaneously, it is important to monitor changes in minute ventilation

Answer 1

If the patient is doing better, defined as requiring less FiO2, lower PEEP, or improved compliance, the clinician may consider liberalizing the ventilator settings.

Many will use a PaO2/FiO2 ratio greater than 200 as a cut-off for changing the patient to pressure support ventilation.

Question 2

Patients should be evaluated every day for readiness for a spontaneous breathing trial (SBT). To determine, consider if:

The patient is stable and/or improving medically.
The FiO2 requirements are 0.5 or less.
The PEEP requirements are 10 cm H2O or less.
The patient can make spontaneous efforts

Answer 2

Criteria for Performing Spontaneous Breathing Trial

-Improvement of underlying condition that led to intubation

-Relative hemodynamic stability
HR < 130
Mean arterial pressure (MAP) adequately supported on a stable dose of vasopressors

• Presence of a cough reflex (often elicited by suctioning)
• Burden of secretions that can be handled by cough strength. (Patients with a robust cough will be able to clear more secretions.)

-Adequate oxygenation
Usually SpO2 > 90% on 40% FiO2 and PEEP ≤ 8
Ability to maintain the current oxygenation status once extubated.

Question 3

-Adequate ventilation
pH > 7.3 with a PCO2 near baseline
Minute ventilation that a patient can maintain after extubated, usually < 12 L/min

Answer 3

-Minimal ventilator settings
On pressure support ≤ 10 cmH2O
On PEEP ≤ 8 cmH2O

• Maintaining tidal volumes ≥ 5 mL/kg PBW
• Respiratory rate < 35
• FiO2 ≤ 50%

Question 4

Criteria for Passing Spontaneous Breathing Trials

Clinical Appearance
No evidence of respiratory distress
Cyanosis, diaphoresis, accessory muscle use, grimacing

Pulmonary mechanics
Ratio of respiratory rate : tidal volume < 105
Respiratory rate < 30 breaths per minute
Tidal volume > 5 mL/kg PBW

Answer 4

Oxygenation and ventilation
SpO2 > 90% on 40% FiO2
PaCO2 ≤ 50mmHg or a
pH ≥ 7.3 or decrease in pH of ≤ 0.07

Hemodynamics
Change in SBP to > 90 or < 180 mmHg
HR < 130 beats per minute
No new dysrhythmias