Non-Invasive Ventilation Nursing
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Direct answer
Non-invasive ventilation delivers ventilatory support through a mask instead of a tube through the cords, and in a hypercapnic COPD exacerbation it is the intervention that most reliably prevents intubation. CPAP provides one constant positive pressure throughout the breathing cycle — it splints alveoli open and improves oxygenation, the treatment of choice in cardiogenic pulmonary oedema; BiPAP adds a higher inspiratory pressure over a lower expiratory pressure, actively augmenting tidal volume and washing out carbon dioxide, which is why hypercapnic failure is its territory. Typical starting settings — inspiratory 10-12 over expiratory 4-6 cm water, or CPAP 5-10 in pulmonary oedema — are titrated against gases checked at one to two hours. Nursing decides success: correct mask and fit, skin and eye protection, and the discipline to recognise failure and escalate before the window closes.
What you must remember
- Physiology split: CPAP (single pressure) recruits alveoli and improves oxygenation — cardiogenic pulmonary oedema, obstructive sleep apnoea; BiPAP (IPAP over EPAP) adds pressure support that raises ventilation and lowers carbon dioxide — COPD exacerbation with respiratory acidosis.
- The evidence threshold: in COPD exacerbations, BiPAP is indicated for persistent acidosis (pH below about 7.35) with PaCO2 above 45 mmHg despite standard therapy — the number examiners want quoted.
- Starting settings: BiPAP commonly IPAP 10-12 with EPAP 4-6 cm water, titrated upward by 2 at a time; CPAP commonly 5-10 cm water in pulmonary oedema.
- Contraindications: cardiac or respiratory arrest, inability to protect the airway, decreased consciousness, copious secretions or vomiting risk, facial burns or surgery, undrained pneumothorax and haemodynamic instability — none of these patients belongs in a mask.
- Mask and skin craft: correctly sized interface with minimal leak, hydrocolloid on the nasal bridge from the first hour, and periodic release — nasal-bridge ulcers are the signature complication.
- Monitoring: heart rate, saturation and respiratory rate, blood gas at 1-2 hours, synchrony checks, documentation of every setting change.
- Failure signs: deteriorating pH or PaCO2 on the first gas check, rising respiratory rate, worsening consciousness, agitation fighting the mask, haemodynamic decline — triggers for intubation discussion, not for strapping the mask tighter.
- Eye care and feeding: upward leaks cause conjunctivitis; feeds upright with brief mask release, since gastric distension and aspiration are real risks.
The first hour of BiPAP on a COPD exacerbation
A known COPD patient arrives drowsy-eyed, respiratory rate 32, using accessory muscles, pH 7.28 and PaCO2 of 68. The nurse selects a full-face mask — drowsy patients mouth-breathe, nasal masks leak — seats it snug but not strapped, and applies hydrocolloid to the nasal bridge before the first hour, not after the redness. The ventilator starts at IPAP 10, EPAP 4, oxygen titrated to 88-92 per cent — this patient's respiratory drive lives on his hypoxaemia.
Twenty minutes in he synchronises; the nurse stays, coaching "breathe with the machine", because first-hour asynchrony predicts failure. At one hour the gas shows pH 7.33, PaCO2 58 — pressures titrated up by 2 per protocol, with oral care, upright sips at mask release and two-hourly skin checks charted. The same note writes the alternative: if pH worsens or drowsiness deepens, intubation is discussed immediately — the mask is a bridge, and the nurse watches whether it holds.
Where students slip
The costliest slip is applying NIV to a patient who cannot protect his airway — he needs an airway, not a tighter mask; the contraindication list is a safety list, not trivia. The second is the CPAP-BiPAP confusion in reverse: CPAP in a hypercapnic patient splints alveoli but moves no additional air, so carbon dioxide climbs while saturations look respectable — "which for pH 7.28 COPD?" is answered BiPAP every time. Technique errors separate candidates: unmonitored oxygen (target 88-92 per cent in COPD), gases not repeated at 1-2 hours, and straps cranked tighter over a leaking mask instead of repositioning it — producing the pressure ulcer of the next week. Finally, know why NIV first when it fits: avoided intubation means avoided ventilator-associated pneumonia, sedation and deconditioning.
Frequently asked questions
What is the difference between CPAP and BiPAP?
CPAP holds a single constant pressure that splints alveoli and aids oxygenation; BiPAP cycles between higher inspiratory and lower expiratory pressures, adding ventilatory support that increases tidal volume and clears carbon dioxide.
When is non-invasive ventilation contraindicated?
In arrest, absent airway reflexes, significantly reduced consciousness, uncontrolled vomiting or copious secretions, facial burns or trauma, undrained pneumothorax and severe haemodynamic instability.
What are typical starting BiPAP settings in COPD?
Inspiratory pressure about 10-12 cm water with expiratory pressure of 4-6, titrated in steps against response, with oxygen targeting a saturation of 88-92 per cent.
When should blood gases be rechecked after starting NIV?
Within one to two hours of initiation and after significant setting changes, to confirm falling carbon dioxide and improving pH.
What signs indicate non-invasive ventilation failure?
Worsening acidosis or carbon dioxide on repeat gases, rising respiratory rate, declining consciousness, agitation with mask intolerance and haemodynamic deterioration — mandating escalation toward intubation.