Mechanical Ventilation

Question 1

What are the indications for mechanical ventilation?

Answer 1

Ventilation (hypercapnea)
Obstruction
Protection (hypoxia)
Secretion

Question 2

What is positive pressure ventilation?

Answer 2

Default kind of mechanical ventilation. Called this because it generates positive pressure that pushes air into the lungs rather than air passively entering due to negative pressure.

Question 3

Describe what PEEP is and the effects it has on the pulmonary system.

Answer 3

Positive end expiratory pressure. At the end of expiration it maintains a degree of pressure (increased end expiratory lung volume).

i) splints open areas of atelectasis
ii) splints open airways to increase gas exchange time
iii) reduces work of breathing

Question 4

Explain CPAP and list the indications.

Answer 4

Continuous Positive Airways Pressure Non-invasive facemask, used in the community. Often used for sleep apnea.

i) trigger: spontaneous
ii) cycle: spontaneous

Question 5

Explain BiPAP and list the indications.

Answer 5

Bilevel Positive Airway Pressure. Provides two levels of pressure, one for inspiration and one for expiration. Non-invasive. Used in acute care to prevent intubation. Used in the community for CO2 clearance in severe COPD.

i) trigger: spontaneous
ii) cycle: spontaneous

Question 6

Explain Assist Control mode of mechanical ventilation.

Answer 6

Has a preset RR, but also assist with patient triggered breaths. If patient triggered breaths do not meet a certain RR then the machine will trigger the next breath.

Question 7

List the advantages and disadvantages of pressure controlled and volume controlled mechanical ventilation.

Answer 7

Volume
i) minute ventilation easily monitored
i) pressures rise depending on lung compliance/disease
Pressure
i) reduces risk of barotrauma
i) TV is not consistent so may hypoventilate.

Question 8

Explain pressure support mode of mechanical ventilation.

Answer 8

Allows patient to control their own RR, TV, and I:E. Provides pressure to support during inspiration. Usually used for patients weaning towards extubation.

i) trigger: spontaneous
ii) cycle: spontatneous

Question 9

Explain Proportional Assist Ventilation mode of mechanical ventilation.

Answer 9

Target is set as % support (ex. 25%). The ventilator provides an additional 25% of the patient generated pressure. Measured on a breath-by-breath basis

i) trigger: spontaneous
ii) cycle: spontaneous

Question 10

Explain NAVA mode of mechanical ventilation.

Answer 10

Neurally adjusted ventilatory assist (NAVA). NG tube equip with sensor array to detect electrical activity at the diaphragm. Triggers breath with pressure support

i) trigger: spontaneous
ii) cycle: spontaneous

Question 11

List the criteria required to wean a patient off mechanical ventilation.

Answer 11

i) Spontaneous inspiratory effort.
ii) PaO2 >200
iii) FiO2 <0.5
iv) Hemodynamic stability
v) PEEP <10
vi) +ve cuff leak on SBT

Question 12

List the PT Tx precautions for patients on mechanical ventilation.

Answer 12

1. With high pressure support, be cautious of techniques that increase pressure (ex. rib springing). PAP 35 cmH2O.
2. PEEP > 12 cmH2O then do not disconnect vent tubing. Use PEEP valve on Ambu-bag.
3. Do not ambulate off ventilator on pressure control mode.
4. Volume control - do not mobilize and avoid manual techniques that increase volume (ex. rib spring).
5. O2 requirements. Do not mobilize if FiO2 0.8 (little reserve). Do not mobilize patient on NO.

Question 13

What are the indications and effects of NO.

Answer 13

Dilates pulmonary arteries as well as other arteries to facilitate improved perfusion.