NIV for Physios Flashcards
What is non-invasive ventilation (NIV)?
Application of bi-level positive pressure to a patient by a non-invasive interface
What is a continuous positive airway pressure (CPAP) machine used for?
- Obstructive sleep apnoea (OSA)
- Pulmonary oedema
- Hypoxemia
- Post-surgical airway collapse
- Splinting airway open
- Increasing lung volume
- Improving oxygenation (doesn’t do much for CO2)
What happens to the pressure in CPAP?
Pressure is constant throughout inspiration & expiration (e.g. 5cmH2O)
What is bilevel positive airway pressure (BiPAP)?
- 2 levels of positive airway pressure
- Expiratory (EPAP): Maintained during expiration & pause between breaths
- Inspiratory (IPAP)
- Delta pressure: Difference between IPAP & EPAP, driving pressure for increasing TV
What is the function of EPAP in BiPAP?
- Has the same effects as CPAP
- Makes the patient breathe deeper, which lowers CO2 production & WOB
When does sleep apnoea occur?
When the upper airway closes during sleep, causing oxygen levels to drop
What common physical features are associated with snoring?
- Retrognathia: Jaw seems small for the skull, or is not in line with the plane of the face
- Neck circumference > 43cm (male) or 39cm (female)
What is the role of the dilator muscles during sleep?
Contract to keep the airway open during inspiration
What is upper airway resistance?
- Hypopnoea: Partial obstruction of the airway
- When a person unconsciously wakes up/comes to a more wakeful level of sleep to prevent hypopnea, constantly throughout the night
- No drop in oxygen levels
What is sleep apnoea a risk factor for?
- Hypertension (approx 40%)
- Acute myocardial infarction
- Stroke
What are the patient-reported symptoms of OSA?
- Sleepiness
- Concentration, memory, learning problems
- Daytime fatigue/reduced energy
- Unrefreshing sleep
- Nocturnal choking or gasping for breath
- Nocturia & enuresis (excessive urination during the night)
- Mood problems & depression
- Decreased libido & erectile dysfunction
- Recent weight gain
- Dry mouth or throat in the morning
- Morning headache
What are some of the symptoms reported by the bed partner in OSA?
- Snoring
- Witnessed apneas
- Restless sleep
- Irritability
What are the treatment options for OSA?
- Lifestyle changes (weightless, alcohol)
- Oral appliances
- Surgery
- CPAP
What are the benefits of CPAP in patients with OSA?
- Improves subjective & objective sleepiness
- Improves neurocognitive function
- Improves QOL measures
- Reduces BP
- Reduces arrhythmia
- Improves cardiac function in heart failure
- May improve insulin sensitivity
What are the main findings in CPAP users?
- Risk of serious CV event is not less in users
- Less sleepiness
- Improved health-related QOL
- Improved mood
- Increased attendance at work
When can severe sleep apnoea cause respiratory failure?
- Morbid obesity
- Frequently associated with excessive alcohol intake
What is one of the most common causes of respiratory failure that is linked to sleep?
Kyphoscoliosis
- Causes a weak diaphragm
- During REM, results in patient hypoventilating/shallow breathing
Why would a person with kyphoscoliosis have higher CO2 levels in the morning than when they went to sleep the night before?
- CO2 increases during REM sleep due to hypoventilation caused by weak diaphragm
- Medullary receptors adapt to higher CO2 levels
- Causes CO2 levels to remain high during the day
- Patient in compensated respiratory failure
Apart from kyphoscoliosis, in what other conditions does REM-related hypoventilation/respiratory failure occur?
- Neuromuscular disease (MND, muscular dystrophy)
- Chest wall deformity
- Lung disease (COPD, CF)
- Control of breathing abnormality (obesity hypoventilation syndrome, stroke)
What are the common characteristics of someone in acute respiratory failure (ARF)?
- Increased RR
- Mouth breathing
- Full face mask more appropriate
What are the aims of NIV use in ARF?
- Improve pathophysiology of ARF
- Improve clinical outcome
- Economic savings (reduced ICU & LOS)
How can NIV improve the pathophysiology of ARF?
- Reduce WOB
- Augment alveolar ventilation
- Improve dyspnoea
- Improve gas exchange
How can NIV improve clinical outcome in ARF?
- Improve survival
- Reduce need for tracheal intubation (maintain airway defence, speech & swallowing, less airway trauma)
What are the limitations of NIV in ARF?
- Need for patient cooperation
- Lack of direct access to the airway (risk of sputum retention & aspiration)
What are the indications for NIV in ARF?
- Exacerbation of COPD
- Hypoxaemic respiratory failure
- Acute carcinogenic pulmonary oedema
- Weaning from mechanical ventilation
- Acute pulmonary infection
- Asthma
- Post-op
- Following intubation
- Obesity hypoventilation syndrome
- Neuromuscular disease
- Chest wall dysfunction
- Other (e.g. CF, patients not for intubation)
What did the Cochrane review of NIV use in ARF COPD find?
NIV resulted in:
- Decreased mortality
- Decreased need for intubation
- Reduced complications
- Reduced hospital stays
- Rapid improvement in pH in the 1st hour
- Improvement in RR
What should you consider if a patient has been on NIV for 2 hours and isn’t responding?
Consider invasive ventilation
What are the considerations for NIV in an acute exacerbation of COPD?
- Very SOB (rapid RR, short inspiratory time, high ventilatory demand)
- Anxious/distressed
- Mouth breathing
- Comatose or confused/combative
- Acidotic
What does further deterioration of an acute exacerbation of COPD require?
Intubation & sedation
What are the management considerations in an acute exacerbation of COPD?
- Usually breathing fast & triggering
- Mod-high levels inspiratory support to reduce WOB
- Impact of PEEPi
- Need fast inspiratory flow
- Can’t afford long Ti due to leaks
- May initially need a FFM
- Supplemental oxygen
- Close monitoring
- Safety issues
- ICU vs ward
What are the absolute CIs to NIV?
- Respiratory arrest
- Life threatening hypoxaemia
- Fixed obstruction of upper airway
- Uncontrolled ischaemia/arrhythmia
- SBP <90
- Severely depressed LOC
- Unable to protect airway
- Inability to clear secretions
- Recent facial/upper airway surgery
- Extensive facial lacerations/burns
- Unstable facial fractures
- CSF leak
- Vomiting
- Undrained pneumothorax
What are the relative CIs to NIV?
- Copious secretions
- Severe comorbidity
- Confusion/agitation
- Bowel obstruction
- GI surgery
- Focal consolidation on CXR
What are the potential complications with NIV?
- Aerophagia, gastric distension
- Aspiration
- Decreased CO
- Hypoventilation, CO2 retention
- Hyperventilation, alkalosis
- Patient discomfort, facial erosion
- Pulmonary barotrauma
- Pneumoencephalus
What are some of the factors that influence the delivered oxygen concentration?
- Oxygen flow rate
- Leak
- Pressure settings
- Site at which oxygen is added to the circuit
Measure the results of oxygen delivery (SpO2)
What did Kennan et al 2002 find regarding NIV in post-extubation failure?
- Patients who developed ARS within 48 hours of extubation
- No difference in rates of reintubation, hospital mortality or LOS
What did Estaban et al 2004 find regarding NIV in post-extubation failure?
- No difference in need for reintubation, rate of death in ICU higher in NIV group
- Longer period to reintubation in NIV group
