Mechanical Ventilation

Question 1

Spontaneous breath vs. mech ventilation

Answer 1

At starting point, airway and alv pressure are atmospheric (both)

After a breath, the pressure are atmospheric in normal, and positive in mechanical

The pressures during inspiration are negative because the negative pleural pressure drives lung inflation (normal)

Positive because the ventilator-generated pressure drives lung infaltion (mechanical)

Question 2

Airway pressures above ____ are injurious

How to remove airway resistance (and just look at compliance)

Answer 2

25-30 cm H2O

No-flow state (end of inspiration)

Question 3

normal pressures during inspiration

Answer 3

Onset of inspiration, IP becomes more negative and alv becomes more negative

Mid inspiration, alv and IP becoming more negative and TPP increasing

At end, alv = 0 and IP is negative…TPP is at max x

Question 4

Normal lung with mech ventilation

Answer 4

At onset of inspiration, generating positive pressure

Mid-inspiration, positive pressure in the alv and IP is becoming less negative

At end-inspiration, the alv equals the proximal airway and the IPP is 0

TPP increased throughout

Half of the pressure was used to distend lung and half was used to distend the chest wlal

Question 5

Firbotic lung mech ventilation

Answer 5

At mid, the pressure in alveolus shoots up high and continues skyrocketing until end of inspiration

TPP is very high

Most of pressure used to distend the lung

Question 6

Stiff chest wall mech ventilation

Answer 6

Alveolar pressure is high, but so is the IPP (positively) so the TPP remains about normal throughout

Most of the pressure is used to distend the chest wall instead of the alveolus

Question 7

How to calculate pressure used to distend the chest wall?

Answer 7

Change in the pleural pressure

Question 8

Asthmatic lung mech ventilation

Answer 8

Everything looks about like normal and at a no-flow state, it appears normal with a TPP of around 10

Proximal airway pressure is much higher at mid-inspiration because harder for air to get there

Question 9

High airway pressures

Normal end-flow pressures

Answer 9

Means some sort of compliance issue…if the pleural pressure is high, then it means chest wall, if not, the lung

Means normal or obstructive