3.1 Oxygen Delivery, Airway Clearance, and Tracheostomy Care
Key Takeaways
- Low-flow devices (nasal cannula, simple mask, non-rebreather) deliver a variable FiO2 that falls as the patient's inspiratory demand rises; only a Venturi mask delivers a fixed, prescribed FiO2 regardless of respiratory pattern.
- A nasal cannula raises FiO2 by roughly 4% per litre from a 21% baseline, giving about 24% at 1 L/min up to about 44% at 6 L/min; above 4 L/min the flow must be humidified to protect the nasal mucosa.
- A non-rebreather mask must be run at 10 to 15 L/min so the reservoir bag stays at least one-third inflated on inspiration; a collapsing bag means the flow is too low and the patient is rebreathing carbon dioxide.
- Suction only on withdrawal, for no more than 10 to 15 seconds per pass, with wall suction set to 100 to 150 mmHg in adults, and hyper-oxygenate before and between passes.
- Keep a spare tracheostomy tube of the same size, one a size smaller, an obturator, and a tracheal dilator at every tracheostomy bedside; if the tube is accidentally decannulated within 7 days of surgical placement, the tract is immature and recannulation must not be forced.
3.1 Oxygen Delivery, Airway Clearance, and Tracheostomy Care
Oxygen is a prescribed drug, not a comfort measure. On the DHP blueprint it sits inside Nursing Fundamentals, but the skill is tested indirectly in almost every adult respiratory, perioperative, paediatric, and resuscitation vignette. Examiners repeatedly ask you to match a clinical picture to the correct device and then to defend the choice. The two decisions that carry the marks are: how much oxygen does this patient actually need, and does their breathing pattern let a low-flow device deliver it reliably?
Low-Flow vs. High-Flow: The Distinction That Drives Device Choice
A low-flow device supplies less gas than the patient's peak inspiratory flow demand, so the patient entrains room air around the device to make up the difference. The delivered FiO2 therefore varies with tidal volume and respiratory rate: the faster and deeper the patient breathes, the more room air is entrained and the lower the actual FiO2. A high-flow device supplies gas at or above peak inspiratory flow, so the FiO2 the patient receives is the FiO2 you set.
This is the exam's favourite trap. A tachypnoeic patient on a simple mask at 8 L/min is not reliably receiving 50% oxygen; they may be receiving far less. If a fixed, known FiO2 is clinically essential — most classically in the hypercapnic COPD patient — the answer is a Venturi mask.
| Device | Flow rate | Approximate FiO2 | Fixed or variable | Best use |
|---|---|---|---|---|
| Nasal cannula | 1–6 L/min | 24%–44% (≈ +4% per L) | Variable | Long-term therapy, eating, talking, mild hypoxaemia |
| Simple face mask | 5–8 L/min | 40%–60% | Variable | Short-term moderate hypoxaemia; never below 5 L/min |
| Partial rebreather | 6–11 L/min | 60%–75% | Variable | Moderate–severe hypoxaemia without CO2 retention |
| Non-rebreather | 10–15 L/min | 60%–95% | Variable | Trauma, shock, carbon monoxide poisoning, pre-intubation |
| Venturi mask | Set per colour-coded adaptor | 24%, 28%, 31%, 35%, 40%, 60% | Fixed | Hypercapnic COPD; any patient needing a precise FiO2 |
| High-flow nasal cannula | up to 60 L/min | 21%–100% | Fixed | Heated, humidified support; type 1 respiratory failure |
| Bag-valve-mask with reservoir | 15 L/min | ~100% | — | Apnoea, agonal breathing, manual ventilation |
Two rules examiners test directly. First, a simple face mask must never run below 5 L/min, because lower flows fail to flush exhaled carbon dioxide out of the mask body and the patient rebreathes it. Second, on a non-rebreather the reservoir bag must remain at least one-third inflated during inspiration; if the nurse observes the bag collapsing completely with each breath, the correct action is to increase the flow rate, not to change the device.
Humidification and oxygen safety
Dry medical gas desiccates the respiratory mucosa, thickens secretions, and causes epistaxis. Add humidification when nasal cannula flow exceeds 4 L/min, for any patient with a bypassed upper airway (tracheostomy or endotracheal tube), and for prolonged therapy.
Oxygen does not burn, but it dramatically accelerates combustion, so fire precautions belong in the care plan:
- Post "Oxygen in Use" signage and prohibit smoking, including by visitors.
- Avoid petroleum-based lip or nasal products; use water-based lubricants.
- Keep cylinders upright, secured, and away from heat sources; store below 52 °C.
- Use cotton linen and gowns; wool and synthetics generate static.
- Electrical equipment at the bedside must be grounded and spark-free.
Airway Clearance and Lung Expansion
Incentive spirometry is the workhorse post-operative lung-expansion intervention. Teach the patient to sit upright, seal the lips around the mouthpiece, inhale slowly and deeply (not forcefully), hold for 3 to 5 seconds, then exhale normally and rest. Target 10 breaths per hour while awake. The single most commonly tested error is the patient who exhales into the device — that is a peak-flow manoeuvre, not incentive spirometry, and it does nothing to prevent atelectasis.
Other clearance techniques worth knowing:
- Splinted coughing: pressing a folded blanket or pillow against an abdominal or thoracic incision before coughing reduces pain and makes an effective cough possible.
- Huff coughing: a series of forced exhalations with an open glottis; preferred in COPD because it avoids the airway collapse a forceful closed-glottis cough produces.
- Postural drainage and percussion: schedule before meals or at least 1 to 2 hours after, to avoid vomiting and aspiration; contraindicated with increased intracranial pressure, unstable spine, or active haemoptysis.
- Hydration: adequate systemic fluid intake thins secretions more effectively than any nebulised mucolytic in most ward patients.
Suctioning: The Numbers You Must Recall
Suctioning is a controlled injury to the airway mucosa, so every parameter is designed to limit harm. Indications are assessment-based — coarse crackles or gurgling, visible secretions, a sawtooth flow pattern on the ventilator, falling SpO2, or an ineffective cough — never a fixed clock schedule.
| Parameter | Adult | Child | Infant |
|---|---|---|---|
| Wall suction pressure | 100–150 mmHg | 95–110 mmHg | 50–95 mmHg |
| Duration of each pass | ≤ 10–15 seconds | ≤ 5–10 seconds | ≤ 5 seconds |
| Rest between passes | 30–60 seconds | 30–60 seconds | 30–60 seconds |
| Maximum passes | 3 | 3 | 3 |
| Catheter size | ≤ ½ the internal diameter of the artificial airway |
Technique rules: hyper-oxygenate with 100% oxygen for 30 to 60 seconds before and between passes; insert the catheter without applying suction; apply intermittent suction only while withdrawing, rotating the catheter; and stop immediately for bradycardia, dysrhythmia, or a sustained desaturation. Do not routinely instil normal saline into the airway before suctioning — it does not loosen secretions and it pushes bacteria from the tube into the lower airway.
Tracheostomy Care, Routine and Emergency
A tracheostomy bypasses the upper airway entirely, so the patient loses natural warming, humidification, filtration, and — with a cuffed tube inflated — the ability to phonate.
Routine care. Clean the stoma and inner cannula per protocol using sterile technique; change ties only with a second nurse holding the flange so the tube cannot be dislodged; secure ties snugly enough to admit one finger beneath them; use a pre-cut or manufactured drain sponge, never a cut gauze square, because loose fibres can be aspirated. Maintain cuff pressure at 20 to 30 cm H2O — high enough to seal against aspiration, low enough to preserve tracheal mucosal capillary perfusion.
Emergency equipment at every tracheostomy bedside:
- A spare tube of the same size, cuffed and ready.
- A spare tube one size smaller, for a difficult recannulation.
- The obturator for the patient's current tube, taped visibly to the head of the bed.
- A tracheal dilator and suction equipment, connected and tested.
- A bag-valve-mask.
Accidental decannulation is the emergency scenario you are most likely to be asked about, and the answer depends on the age of the stoma. If the tracheostomy was surgically created less than 7 days ago, the tract is immature and will collapse; do not force a tube into it. Instead, call for emergency help immediately, and oxygenate and ventilate from above with a bag-valve-mask over the mouth and nose while occluding the stoma. If the stoma is mature, the nurse may reinsert using the obturator, withdraw the obturator immediately (it completely occludes the airway), confirm airflow, and then reassess. If the tube cannot be replaced, ventilate from above and summon the airway team.
A nurse is caring for a patient with severe hypoxaemia who is receiving oxygen through a non-rebreather mask set at 8 L/min. On assessment, the nurse observes that the reservoir bag collapses completely with every inspiration and the patient's SpO2 has fallen to 86%. What is the nurse's most appropriate immediate action?
A nurse is performing open endotracheal suctioning on an intubated adult. Which combination of technique parameters reflects safe practice?
A patient who underwent a surgical tracheostomy three days ago coughs forcefully during repositioning, and the tracheostomy tube is expelled completely from the stoma. The patient is in respiratory distress with an SpO2 of 84%. What must the nurse do?