Non-Invasive Ventilation Flashcards
Non-Invasive Positive Pressure Ventilation (NPPV) Definition
- The augmentation of alveolar ventilation thru means other than an artificial airway
- Can be:
- NPPV (BiPAP)
- CPAP - doesn’t augment patient’s ventilation
- Other methods of NPPV:
- Iron Lung
- Chest Cuirass
In What two acute care conditions is NPPV the standard first line of care
COPD Exacerbations-Reduce mortality, reduce hospital stay, fewer complication. Should only be used when they are not at risk for intubation (PaCO2 is >45 mmHg and pH is <7.35)
Acute Cardiogenic Pulmonary Edema- First line of therapy with CPAP of 8-12 cmH2O. If patient is hypercapnic or has persistent dyspnea then go to BiPAP
Acute Care Condition Where we can Use NPPV
Asthma- Only ancedotal evidence
Immuosuppresent State- Use NIPPV unless contradictions are present as there is a reduced rate of pneumonia and infections
Community Acquired Pneumonia- Reduce rate of intubation and length of hospital stay (only when patient has underlying COPD). As of right now only used with pt. wit pneumonia concurrent with COPD
Hypoxemic Respiratory Failure-Conflicting results in studies. If we are using it we need to see imporvement in 1-2 hours
Do-Not-Intubate-Orders-Use only if patients understand that it will only help the acute process and not the underlying chronic process
Postoperative-Some studies show positive results, especially prophylactic use for obese patients. Needs more studies
Difficultly Weaning-Shows reduced weaning, length of ICU stay, incidence of nosocomial pneumonia and 60 day mortality, however, duration of ventilator support was longer. Most benefit seen in acute on chronic (COPD) and CHF
For patients acute respiratory failure should have at least two of the following
Accessory muscle use
Paradoxical breathing
RR ≥ 25 bpm
Dyspnea
PaCO2 > 45 mmHg with pH < 7.35
PaO2 / FiO2 < 200
Chronic Care Indications
- Nocturnal Hypoventilation
- Eg. Sleep apnea, obesity-hypoventilation syndrome
- COPD
- Rest the respiratory muscles and improve sleep
- Restrictive thoracic disease
- Will rest respiratory muscles, decrease CO2 and improve lung function
- Types of restrictive thoracic disease
- Post polio
- Neuromuscular disorders
- Chest wall abnormalities
- Kyphoscoliosis
When a patient has acute respiratory failure contraindications for NPPV include
Apnea
Hemodynamic instability
Uncooperative patient
Facial burns
Facial trauma
High risk of aspiration
Copious secretion
Anatomic abnormalities
Predictors of NPPV success (Acute Setting)
Minimal air leak
Low severity of illness
Respiratory acidosis (PaCO2 > 45mmHg but < 92mmHg)
pH < 7.35 but > 7.22
Improvement in gas exchange within 30 – 120 minute
Improved respiratory rate and heart rate
Criteria for Terminating NPPV
Worsening pH and CO2
RR > 30 bpm
Hemodynamic instability
Inability to clear secretions
Decreased LOC
CPAP
Spontaneous unsupported breathing
Does not augment ventilation
NPPV
Spontaneous supported breaths with 2 pressure levels
Does augment ventilation
Home care ventilators or critical care ventilators provide NPPV
BiPAP is a general term derived from one of the first NPPV machinesOften used in the context of any non-invasive mode that augments ventilation
EPAP and IPAP
Most common equivalent is to pressure support ventilation
Expiratory Positive Airway Pressure (EPAP)
- aka CPAP when no inspiratory pressure is used
- Physiological Effects:
- Reverses atelectasis
- Recruits alveoli (improve V/Q)
- Increases FRC
- Improves compliance
- Can offset the effects of intrinsic PEEP
- Causes mechanical bronchodilation, decreasing airway resistance
- All of the above will decrease WOB
Inspiratory Positive Airway Pressure (IPAP)
- IPAP is the analogous to the Pressure Support setting in PSV
- Like in PSV the resulting VT is dependent on pt effort, lung mechanics and the amount of support set (IPAP/PS)
- However, these pressures are typically set as an absolute pressure on non-invasive ventilators
- Physiological Effects:
- Reduces WOB
- Relieves respiratory muscle fatigue
- Augments patient’s own spontaneous efforts thereby improving spontaneous tidal volume
All of the above will decrease WOB
Spontaneous (S) Mode
Patient triggered, pressure limited, flow cycled
No mandatory breaths
Spontaneous/Timed (S/T) Mode
Patient triggered breaths are P limited and flow cycled
Time triggered breaths are P limited and time cycled
Often (depending on the machine) mandatory breaths are only given if the patient’s rate falls below the set rate
Timed (T) Mode
A control mode: time triggered, pressure limited, time cycle
Mode Name and Ventilator Being Used
Actual mode names can vary with the brand of ventilator used. Point: have them think of BiPAP as PSV…with the idea that sometimes a back-up rate is applied (and in other special circumstances they may see other modes used)
Non-Invasive Ventilators Devices
Usually electrically powered, blower driven, and microprocessor controlled
Use a single-circuit design
Designed to function with an intentional small leak (= exhalation valve)
This is how CO2 is cleared from the circuit! Without this leak re-breathing will occur!
The most important advantage of a non-invasive ventilator is its ability to trigger and cycle appropriately in the face of leaks!
NIVs: Exhalation Valves
Shark Fin Exhalation Valve (old)
Whisper Swivel
Some masks will have a integral exhalation valve
NIVs: Oxygen Considerations
- Most non-invasive ventilators require oxygen to be Tee’d in
- This can be done at the machine outlet (most common) or at the mask
- Some newer NIVs designed for acute care allow FIO2 to be accurately set. ( example Visions)
- If the patient requires high, stable FIO2 then consider using a critical care vent or a NIV ventilator designed to deliver stable FIO2
- Avoid t’ing in O2 at flows greater than 15 LPM—this may cause problems with triggering and cycling
Critical Care Ventilators
- Uses the dual limbed circuit, with pressure targeted modes being the most often used (PSupp)
- Exhalation valves are an integral part of the ventilator
- This means that the leaky exhalation valve is used on a non-invasive ventilator is not require
- Re-breathing of CO2 is not a significant concern
- The biggest advanatge is allowing for the precise FiO2 delivery and high FiO2 (will make or break success with hypoxemic respirtory failure)
- Leaks in the system can affect the ability of the vent to trigger the cycle appropraietly
how flow-triggering may result in auto-triggering in the face of leaks
Explain how flow-triggering may result in auto-triggering in the face of leaks-can either decrease the sensitivity or switch to pressure triggering (but this is associated with a higher work of breathing)
Go through examples of PSV and flow cycling and why it may not terminate the breath and the patient ends up actively exhaling at the higher pressure. To correct the problem: use time-cycling and therefore PCV, if on the 840 increase the Esens
Ventilators Used to Deliver NPPV
- NIV vents are designed to work in the face of leaks
- They have special flow-triggering and flow-cycling mechanisms that are responsive to changing leaks
- Most require oxygen to be Tee’d in
- Critical care ventilators have the advantage of delivering high, stable FiO2s
- Critical care ventilators are not designed to be a leaky system and their triggering and cycling functions can be affected by leaks
- Some newer critical care vents have “NIV” options which are designed to compensate for leaks (nuisance alarms are turned off)
- Recommend heated humidity be delivered to all patients receiving NPPV
- If a crit.care vent has a NIV mode its main function is to disable the volume/minute volume alarms—become nuisance alarms during NIV due to mask leaks
NIV Terminology
NIV Ventilator Term Critical Care Ventilator
IPAP Pressure Support/ Pinsp
EPAP CPAP or PEEP
BiPAP PS with CPAP or PCV with PEEP
Choosing The Patient Interface
- Mask fit and comfort is essential for patient compliance
- Selection of full face vs. nasal mask:
- Generally guided by patient preference
- Try using a nasal mask first, then progress to the use of chin strap, then to full face mask
- With more severe ARF - should go to full face mask as first choice. If patient is unable to tolerate then consider nasal mask
Nasal Mask
Reduces the feeling of claustrophobia
Allows for vomiting and expectoration
Patient can discontinue ventilation voluntarily by opening mouth
Adds less deadspace
Full Face Mask
Preferred in severe ARF because dyspneic patients are often mouth breathers
Is considered to give more effective ventilation
Higher dead-space volume compared with nasal masks
With critical care vent – only use full face mask!
NPPV: Initial Settings
- Initially start with low pressures
- EPAP or CPAP
- 4 cmH2O
- IPAP or Psupp
- ∆ 4 cmH2O
- EPAP or CPAP
- Titrate to effect once patient comfortable with NPPV
- EPAP or CPAP of 5 - 8 cmH2O usually required for most patients
- IPAP or Psupp titrate
- for Vt’s of 4-6 ml/kg IBW
- For acceptable respiratory rate & minimal WOB
- FiO2 for SpO2 > 90% (Accept lower for COPD)
What do you do when the patient is struggling to trigger the ventilator
Increase pressure support
What can we do to Offset Auto PEEP
Increase CPAP/PEEP
