1.2b Resuscitation (B - Breathing) Flashcards
Define ‘breathing’ and ‘minute volume’ in a resuscitation context.
Breathing is complex and is controlled by physiological, metabolic and anatomical factors.
Successful breathing consists of:
-
Ventilation
- Ability to exchange inside CO2 from Hb to outside
- Delivery/removal of gases from gas exchange interface
- Failure of this leads to increase CO2 and decrease O2 in blood
-
Oxygenation
- Ability to exchange outside O2 to Hb inside
- Decreased gas exchange and oxygenatoin to lungs
- Due to ventilation-perfusion mismatch
- Ventilation < perfusion: E.g. consolidation in lungs
- Ventilation > perfusion: E.g. pulmonary embolus
Successful breathing depends on ‘minute volume’ which is the air inspired and expired by lungs per minute.
What is the major sign of compromised breathing?
Dyspnoea.
Consists of change in these parameters in breathing:
- Effort
- Distress, fatigue, increased RR (always do it yourself 15-30s), use of accessory muscles, tracheal tug, indrawing, recession.
- Efficacy
- Is oxygenation and ventilation working? (See attached image.)
- Effect
- Decreased LOC
- Poor oxygenation - reduced O2
- Poor ventilation - reduced O2 + increased CO2
- Decreased LOC
Name 2 types of patients you should re-consider before giving O2.
- CO2 retainers, e.g. chronic obstructive pulmonary disease. Can cause increased CO2 retention.
- ACS, national Cardiac Guidelines recommend not giving oxygen unless hypoxic <93%.
For these patients, consider titrated O2 therapy, such as through nasal prongs or Venturi mask.
Explain what the target oxygen levels should be for different demographics of patients.
- ACS - no O2 unless hypoxic or <93 %.
- COPD - aim >90%
- Other patients - aim 94-96%
Explain the principles of titrated O2 therapy for patients who are chronic CO2 retainers.
Should be considered if chronic causes of PCO2 rise.
- Check previous blood gas. Low or normal PCO2 with normal bicarbonate is not a chronic CO2 retainer and does not require titrated oxygen therapy.
- Begin O2 treatment with variable oxygen mixing, e.g. Venturi mask, or just by changing flow rate through a simple mask.
- Use pulase oximetry to aim 88-92% O2 sats.
- Recheck blood gases and watch for change in PCO2 - continue current therapy of CO2 is decreasing, decrease O2 delivery if CO2 is increasing, but maintain O2 sats 88-92% and recheck gases.
- If CO2 is increasing and unable to maintain O2 >88%, consider BiPap and get help urgently.
Explain the mechanism of increased PCO2 if you give high flow O2 to chronic CO2 retainers.
Careful giving high-flow O2 to chronic CO2 retainers.
This may paradoxically increase their PCO2.
Due to several reasons:
- Changes in pulmonary vasoconstriction, causing dead space and shunting, i.e. V/Q mismatch.
- Hypercapnia causes vasodilation, allowing for better gas exchange
- Sudden high-flow oxygen causes vasoconstriction, negating this effect and causing V/Q mismatch.
- Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3682248/
- Haldane effect - Hb molecules release more CO2 in the presence of O2.
- Blunting of hypoxic drive - these patients are dependent on mild hypoxia to stimulate the respiratory centre.
Explain the contraindications for titrated oxygen therapy.
Contraindicated if acute causes of increased PCO2.
- Acute CO2 retention from pulmonary oedema
- Pneumonia
- PE
- Asthma
This is because the PCO2 is acutely raised by imparied respiratory pathology with no risk of blunting of any hypoxic drive. These patients require high-flow oxygen as priority**. **Seek help.
Source: Marshall & Ruedey’s ‘On Call p64, 3rd ed.’
What are the types of respiratory failure?
Type 1 Respiratory Failure
- Failure of oxygenation
- Low O2
Type 2 Respiratory Failure
- Failure of ventilation
- Low O2, high CO2
What bedside investigations can you implement to assess breathing efficacy?
- Pulse oximetry
- VBG
- pH, pCO2
- pC02 - 5mmHg can help estimate CO2 in arterial blood, however in unwell patients the difference can be up to 20mmHg
- Be careful about giving O2 to patients with chronic compensation (low pH, high CO2, high HCO3) as it can increase CO2
- ABG
List the common oxygen delivery devices.
- Nasal prongs
- Hudson mask
- Non-rebreather mask - reservoir to help provide additional oxygen if intake exceeds flow.
- Venturi mask (adjustable O2 amount)
Explain how much O2 each O2 delivery system can administer.
Explain how to set up a high-flow humidified nasal prong oxygen giving set.
These are the basic instructions for a high-flow humidified nasal prong oxygen giving set, the Air Vo.
Describe the type of breathing support that the bag-valve mask provides.
- Positive pressure ventilation
- High concentration oxygen (close to 100%)
- Used with airway adjuncts and manoeuvres
If you are using the bag-valve mask, you must be ready to organise a definitive airway, e.g. laryngoscope + ETT.
Describe the parts of the bag-valve mask apparatus.
Should connect it to 15L/min O2, which allows filling of the reservoir.
The mask tip should fit over the bridge of the nose, the bottom of the mask fits between the cleft of the chin and the lower lip.
Explain the ‘BOOTS’ acronym and the predictors of BVM difficulties.
B - Beard - prevents good seal
O - Obesity - provides anatomical obstruction and requires higher pressures to ventilate
O - Old - Older patients have less subcut tissue, less skin turgor which makes it more difficult to have a seal
T - Toothless, cheeks sunken, again more difficult for seal
S - Snore/stridor - know existing obstruction, wil need to deliver high pressures to ventilate
Describe the 1-person BVM technique.
Describe the 2-person BVM technique.
