Lecture 4 - Non-invasive Ventilation and Acute Resp Failure

Question 1

CPAP vs Bilevel Ventilation

Answer 1

CPAP
- delivers constant single level of pressure during inspiration and expiration
- does not activel assist inpiration
- primarily used for hypoxaemia
- provides a distending pressure increase within the airway or alveoli
BiLEvel Ventilation
- provides two levels of airway pressure: IPAP and EPAP/PS and CPAP
- IPAP or PS: assist insp, increase Vt, reduces work of breathing, reduces CO2
- EPAP (CPAP): provides expiratory pressure, increases lung vols, improves o2
- primarily used for hypercapnic resp failure

Question 2

What are the uses of Bilevel Ventilation

Answer 2

• improve gas exchange - decrease paCo2 and correct acidosis

- reduce work of breathing - relieve dyspnoea

Question 3

What does a high flow nasal cannula do?

Answer 3

decreases anatomical dead space - co2 washout
small amount of PEEP - increase lung vols or recruit collapsed alveoli
constant fraction of inspired 02
humidification - preserves MCC

Question 4

Bilevel IPAP/EPAP settings and there effect

Answer 4

Increasing IPAP
- increases VT 
- reduces work of breathing
-reduces RR 
EPAP 
- decrease WOB by offsetting PEEpi 
- improve V/Q mismatch by increasing FRC

Question 5

complications/side effects to Bilevel Ventilation

Answer 5

• skin breakdown
• eye irritation from leak
• airway drying
• gastric distension
• pulmonary barotrauma
• aspiration pneumonia
• hypotension