Extrapulmonary Effects of Mechanical Ventilation

Flashcards about the Extrapulmonary Effects of Mechanical Ventilation

During spontaneous breathing, what affect does the negative intrapleural pressure have on the body?

Draws air into the lungs and blood into the major thoracic blood vessels and heart.

How does positive pressure ventilation affect cardiac output?

Increased intrathoracic pressure leads to decreased cardiac output.

What is the correlation between thoracic vascular pressures and mean airway pressure during positive pressure ventilation?

There is a direct correlation.

Why does PPV with PEEP further decrease cardiac output?

PEEP further increases mean airway pressure.

How does high tidal volumes or high levels of PEEP affect pulmonary vascular resistance (PVR)?

They compress the alveolar capillaries, increasing pulmonary vascular resistance.

What can increased right ventricular afterload lead to?

Dilation of the RV and in some cases, a left shift of the interventricular septum.

What is the 'Cardiac Tamponade Effect' in the context of mechanical ventilation?

The heart is compressed between the lungs when tidal volumes are large.

What can cause a decrease in coronary vessel perfusion?

Any factor that decreases the coronary artery perfusion gradient.

How do people with normal anatomy compensate for the cardiovascular effects of mechanical ventilation?

Increase in sympathetic tone, shunting blood flow away from kidneys and lower extremities.

How are the cardiovascular effects of increased airway pressure affected in patients with stiff lungs?

The effects are diminished.

How are the cardiovascular effects of increased airway pressure affected in patients with stiff chest walls?

The effect is increased.

How can PEEP and PPV be beneficial to patients with LV dysfunction?

PEEP improves oxygenation to the myocardium and can reduce preload by increasing intrathoracic pressure and decreasing venous return.

What type of airway pressure is the most potentially damaging pressure?

Mean airway pressure.

Why is mean airway pressure not all bad?

It increases FRC and improves oxygenation.

How do higher inspiratory flows affect inspiratory time and mean airway pressure?

Higher flows decrease inspiratory time and decrease mean airway pressure.

What range should I:E ratio be kept to reduce mean airway pressure?

1:2 to 1:4 or lower.

Inflation hold increases and mean airway pressure.

TI

What are the benefits and hazards of increased Paw?

Benefits:

• Increased VA

• Recruitment of alveoli

• Better gas distribution

  Hazards:

• Decreased cardiac output

• Decreased O2 transport

• Increased risk of barotrauma

How can PPV decrease CPP?

Decreased cardiac output can decrease CPP and increased CVP will decrease venous return from the head increasing ICP.

What are the 3 ways changes in renal function occur?

1. renal responses to hemodynamic changes,

2. humoral responses,

3. abnormal pH, PaCO2 and PaO2 affecting the kidney.

Decreased blood pressure could increase the release of causing the kidneys to retain water decreasing urine output.

ADH

What PaCO2 level can severely impair renal function?

PaCO2 > 65 mm Hg

What may liver malfunction caused by in PPV?

Decrease in cardiac output, the downward pressure exerted by the diaphragm on the liver, a decrease in portal blood flow, or an increase in splanchnic resistance, - which could lead to liver ischemia.

Why should every mechanically ventilated patient have a gastric tube?

To prevent gastric distension from swallowing air.

What can over-feeding lead to?

Increased O2 consumption and increased CO2 production.

How REE can be measured?

By indirect calorimetry