M6 NIV

Question 1

Physiology impacts of NIV (6)

Answer 1

• Can reverse physiological and mechanical derangements associated with respiratory failure
• augmentations of alveolar ventilation, helps reverse acidosis and hypercapnia
  -alveolar recruitment and increased FiO2, helps reverse hypoxia
• reduction of work of breathing and fatigue
• stabilisation of chest wall in presence of trauma
• reduction in left ventricular afterload and improves LV function

Question 2

CPAP vs BiPAP vs PEEP

Answer 2

CPAP - delivers the same pressyre throughout the respiratory cycle ( a way of delivering peep but also maintains the set pressure throughout the resp cycle)
BiPAP- delivers two different pressures insp/exp
PEEP- pressure that remains in the airways at the end of the respiratory cycle that is greater than atmospheric pressure

Question 3

IPAP vs EPAP

Answer 3

I: application of positive pressure during inspiration (allows less work required from the respiratory muscles). if you increase the IPAP you increase the VT. if a patient requires larger tidal volumes to decrease CO2 you would increase

E: application of positive pressure when exhaling, works like PEEP, increasing the EPAP improves the oxygenation by increasing the FRC

Question 4

what is pressure support

Answer 4

pressure provided to help the intubated patient overcome the resistance of the ETT during inspiration when they are spontaneously ventilating
- has no impact on inspiration ie No IPAP

Question 5

how does NIV impact tachypnoea?

Answer 5

• reduces RR by prolonging the expiratory phase
  -causes pressure equalisation
• transitions patient from turbulent flow to non turbulent = decreased resistance
• mechanical augmentation: distends collapsed respiratiry vessels during expiration and expands chest wall during inspiration
  -WOB reduction: helps with inspiratory support (increased VT)

Question 6

how does NIV cause gas exchange improvement

Answer 6

recruits collapsed alveoli while setting a PEEP may stabilise the recruitment this results in minimisation of v/q mismatch = improvement of gas exchange and enhance respiratory system compliance

Question 7

how does NIV cause WOB reduction

Answer 7

• ventilation relies on generating a pressure to be able to create flow in a system of given resistances to create volume change

niv reduces WOB in two ways
- positive pressure inspiratory support ( unloads inspiratory muscles)
-PEEP counterbalances intrinsic PEEP and increases respiratory system compliance

improving gas exchange and improving muscle load can reverse fatigue, mitigate dyspnoea and reduce neural drive = more normal ventilatory patter

Question 8

cardiovascular effects of NIV

Answer 8

• Increases intrathoracic pressure and results in subsequent decrease in VR and RV afterload
• decrease CO and pulmonary perfusion
• increased intrathoracic pressure reduces LV afterload and improves LV function

Question 9

how does NIV help cardiogenic APO

Answer 9

• reduction in LV filling pressure and mitral regurgitation
• increases LV ejection fraction
  -systolic function and myocardial energy consumption are enhanced
  -BiPAP helps with assissting respiratory muscles during inspiration and reducing workload