NIV Flashcards
NIV
- def
- types
- benefits
Delivery of positive pressure ventilation through a noninvasive interface (e.g. nasal mask, face mask, nasal plugs), rather than an invasive interface (endotracheal tube, tracheostomy)
Types: BPAP and CPAP
Benefit: reduces resp muscle fatigue and improves ventilation
Contraindications to NIV
Absolute:
Severe facial deformity
Fixed upper airway obstruction
Facial burns
Relative:
pH<7.15
pH<7.25 + adverse features
GCS <8
Confusion/ agitation
Cognitive impairment
Predictors of NIV failure
High severity score of illness (APACHE II, SAPS II, SOFA)
Older age
Failure to improve after 1h on NIV
Multiorgan involvement
Premorbid status (inability to perform self care)
pH<7.25, PaCO2≥75mmHg after 2h of NIV
Difficult to identify aetiology of resp failure
ARDS/ pneumonia
PFR <150mmHg
Higher TV generation
Complications of NIV
1) Nasal bridge ulceration
needs assessment every 4-6h
Barrier dressing
Regular breaks & alternating 2 interfaces
Topical steroid in mask-related rash
2) Severe gastric distension
Usually from poor coordination
NGT may be inserted
3) Sinus/ear/nose discomfort
water-based gels & topical steroid or decongestants can be used
Do not use petroleum-based emollients with supplemental O2
4) Pneumothorax
To be considered in unexplained agitation/ distress or chest pain
Intercostal drainage required
Review need to cont NIV
5) Sputum retention
Can precipitate ARF, NIV failure & resp distress post extubation
Manual-assisted cough and mechanical insufflation-exsufflation are safe methods to aid secretion clearance
- In NMD: mechanical insufflation-exsufflation (e.g. with Coughassist T70)
Practice points prior to starting NIV
1) ABG
2) CXR – but should not delay NIV initiation
3) Reversible causes for resp failure should be sought and treated
4) Individualized plan in the event of NIV failure – involve the pt wherever possible (and discuss Mx of possible future episodes of ARF with pt due to high recurrence rate)
How to initiate NIV – The equipment & Ax
The equipment:
1) Ventilator with non-invasive modes, or portable pressure ventilator
2) Interface:
Types:
Nasal mask/ pillows – not preferred due to mouth breathing
Full face mask – preferred and most commonly used
Helmet – interfere with triggering and cycling off delay → desynchrony. But higher pressures can abolish this
3) Supplemental O2
To be adjusted to achieve SpO2 88-92%
Setting should be optimized before increasing FiO2, as alveolar ventilation will improve gas exchange
4) Humidication
Not routinely required
Useful in pt complaining of mucosal dryness or if with thick secretions
5) Aerosol delivery
Not routinely required
Nebulised drugs to be given during breaks from NIV → facilitates coughing 7 clearing of secretions
Advisable to place it btw the interface and the resp circuit if pt dependent on NIV
6) Sedation
To be used with close monitoring and in HDU/ICU setting
Used in agitated/ distressed and/or tachypnoeac pts
To provide Sx relief and improve NIV tolerance
Iv morphine 2.5-5mg (+/- benzodiazepine)
7) ECG monitoring
Advisable if PR>120bpm/ dysrhythmia/ cardiomyopathy
8) Transcutaneous CO2
A continuous pain-free monitoring of CO2 measurements → may replace the need for frequent ABGs
Not readily available
The assessment:
1) Review the indications and contraindications
2) Review care area
NIV should be initiated in critical care sites: ED, HDU, ICU, resp ward with adequate support
3) ABG
To assess NIV efficacy
Should be done within 1h after initiation
Repeat frequency depends on clinical condition and NIV settings
4) Level of consciousness
Assess GCS and ability to cough and maintain airway before and after NIV
NIV set up
1) Choose the mode: (Go with S/T mode usually)
- Options:
a) S Mode (spontaneous mode) = inspiration triggered by the pt
b) T Mode (time mode) = the machine determines the rhythm and breathing rate for all patients at a fixed predetermined rate
c) S/T Mode (spontaneous/time mode) = the patient determines the rhythm and rate of breathing, until the respiratory rate is lower than the specified value, then the machine will adjust to Timed Mode and will provides the additional breaths (to achieve the predetermined rate)
2) Start with IPAP 10, EPAP 4
3) Adjust IPAP and EPAP
- Increase IPAP for CO2 clearance
- Increase EPAP to increase O2
- Make sure IPAP - EPAP (which is the pressure support) if between 5-12.
- The bigger the pressure support (PS), the bigger the tidal volume (Vt)
- Uptitrate IPAP over 10-30mins to achieve adequate chest augmentation
- in COPD:
4) Set backup rate at 16-20
5) Set rise time at 100-300miliseconds (mainly for pt comfort, this will not change other parameters)
6) Set inspiratory time:
- in COPD: 0.8-1.2s
- in OHS, NM & CWD: 1.2-1.5s
- Aim to achieve I:E
in COPD: 1:2 to 1:3
OHS, NM & CWD: 1:1
- if unable to achice the I:E, alter the RR and inspiratory time
7) Aim to achieve SpO2 >88-92%
8) Treat underlying reversible cause
9) Check synchronisation, mask fit, kiv for physio, bronchodilators and anxiolytic.
10) Consider IMV if persistent hypoxia, pH<7.25 despite optimal NIV, RR >25, new onset confusion/ distress
If wants to improve O2:
1) increase EPAP (which is PEEP in IMV)
2) increase FiO2
If wants to improve CO2:
1) Increase IPAP
2) Increase RR
Recommendations for NIV (ERS/ATS 2017)
1) COPD exacerbation:
Bilevel NIV in
a) ARF leading to acute or acute-on-chronic resp acidosis (pH≤ 7.35)
b) Prevent intubation and invasive mechanical ventilation
c) pH ≤7.35, PaCO2>45 and RR>20-24 despite medical therapy
d) No lower limit of pH, but the lower the pH, the greater risk of failure, thus needs closer monitoring for rapid intubation if not improving
e) Alternative to invasive mechanical ventilation in pts with severe acidosis and resp distress
2) Cardiogenic pulmonary oedema with ARF
Inc pre-hosp setting
3) Immunocompromised with ARF
For early NIV
4) Post-op ARF
NIV effective at improving lung aeration and art O2 and decrease atelectasis
5) Palliative care
In setting of terminal conditions
6) Chest trauma with ARF
7) Following extubation
To prevent post-extubation resp failure in high-risk pt
(age>65, underlying cardiac or res disease)
8) Weaning
- To facilitate weaning from mechanical ventilation in hypercapnic resp failure
NIV NOT recommended in:
1) COPD exac: hypercapnic but not acidotic
2) Following extubation:
- to prevent post-extubation resp failure in non-high-risk pts
- Pts with established post-extubation resp failure
NO recommendations made for the following:
1) Asthmatic with ARF
May be considered in subgroup that behaves like COPD (i.e. fixed airway obstruction)
2) ARF sec to pandemic viral illness
- Reported NIV failure rates of ~30% (H1N1 infection) & risk of infectivity
3) Weaning from IMV for hypoxemic pts
4) De novo ARF
- resp failure occurring without prior chronic resp disease,
- usually hypoxic (PFR </= 200), tachypnoeac (RR>30) and nonCOPD (e.g. pneumonia +/- ARDS)
- NIV lacks efficacy in reducing WOB
Recommendations for NIV from BTS 2016
This guideline does not cover ARF sec to CCF, trauma or acute brain injury
1) COPD exac
Initiate NIV when pH <7.35 AND pCO2>6.0kPa (>45mmHg) AND RR>23 after 60 mins of optimized medical therapy
(NOTED THAT THERE IS A CORRECTION TO THE GUIDELINE PUBLISHED IN 2017)
2) Asthmatic with ARF
Not to be used in ACUTE asthma exacerbation; BUT
hypercapnia in CHRONIC asthma resembles COPD and should be managed as such
3) Non-CF bronchiectasis
- Initiate NIV using the same criteria as AECOPD
4) Cystic fibrosis
NIV is Rx of choice mini-trachy + NIV may offer greater chance of survival than IMV
Physiotherapy for sputum clearance
5) Restrictive lung disease: Neuromuscular disease (NMD) & Chest Wall Disease (CWD)
- NIV should always be trialed with hypercapnia do not wait for acidosis
- NIV to be considered in acute illness when known vital capacity <1L
- IMV if NIV failing
- In NMD, anticipate bulbar dysfunction – NIV may be impossible
6) Obesity hypoventilation syndrome
- Initiate NIV using the same criteria as in AECOPD
- Also indicated in obese hypercapnic pts with daytime somnolence, sleep-disordered breathing +/- RHF in absence of acidosis
