Arterial Blood Gas & Ventilation Techniques

• Lecture focuses on analysing health data through arterial blood gas samples, respiratory and metabolic conditions, ventilation techniques, and airway management.

Lecture Objectives

• Analysing health data by interpreting arterial blood gas samples.
• Understanding respiratory acidosis, respiratory alkalosis, metabolic acidosis, and metabolic alkalosis including cases of mixed acidosis and alkalosis, compensated, and partially compensated gases.
• Discussing the importance of acidotic or alkalotic conditions in patients, including the oxyhemoglobin dissociation curve.
• Understanding high flow nasal prongs (HFNP)
• Learning the components of ventilator terminology
• Describing the basics of non-invasive ventilation, including continuous positive pressure ventilation (CPAP) and Bi-level Positive Airway Pressure (BiPAP), its components, indications, and nursing management.
• Introducing the basics of invasive ventilation, including nursing management
• Describing the process of intubation, including endotracheal tubes (ETT) and tracheostomy, their indications, risks, and correct placement, assessment of artificial airways, documentation, nursing responsibilities, emergency equipment checks, and airway of suctioning
• ABG Interpretation:* Arterial Blood Gas interpretation for acid-base balance

pH Scale and Ranges:

• Acidic pH is less than 7.35
• Normal pH ranges from 7.35 to 7.45
• Basic pH is greater than 7.45

PaO2:

• Normal range is between 70 – 100mmHg.

PaCO2:

• Normal range is between 35-45mmHg.
• Higher than 45mmHg indicates acidity
• A reading lower than 35 indicates alkalosis

HCO3:

• Normal levels are between 22-26mmol/L.
• Values less than 22 indicate acidity
• Values greater than 26 indicate Alkalosis

Example ABG Interpretations:

• pH 7.23, PaO2 55mmHg, PaCO2 50mmHg, and HCO3- 25mmol/L is respiratory acidosis with hypoxemia.
• pH 7.53, PaO2 85mmHg, PaCO2 23mmHg, and HCO3- 18mmol/L signifies respiratory alkalosis.
• pH 7.21, PaO2 95mmHg, PaCO2 44mmHg, and HCO3- 18mmol/L indicates metabolic acidosis.
• pH 7.48, PaO2 78mmHg, PaCO2 42mmHg, HCO3- 35mmol/L indicated metabolic Alkalosis.
• pH 7.25, PaO2 91mmHg, PaCO2 65mmHg, and HCO3- 13mmol/L is mixed respiratory and metabolic acidosis.
• pH 7.49, PaO2 75mmHg, PaCO2 27mmHg, and HCO3- 28mmol/L indicates mixed respiratory and metabolic alkalosis.

Key Considerations for Compensation:

• No Compensation:*
• pH remains abnormal
• The value not causing the problem remains normal
• There is no attempt to normalize pH.
• Partial Compensation:*
• pH is still abnormal
• The value not causing the problem is abnormal
• There is an attempt to normalize pH.
• Full Compensation:*
• pH is normal
• The value not causing the problem is abnormal
• It has successfully normalized the pH.

Examples of ABGs With or Without Compensation:

• pH 7.21, PaO2 58mmHg, PaCO2 44mmHg, and HCO3- 18mmol/L shows metabolic acidosis without compensation and with hypoxemia.
• pH 7.23, PaO2 65mmHg, PaCO2 50mmHg, and HCO3- 30mmol/L respiratory acidosis with partial metabolic compensation and mild hypoxemia.
• pH 7.39, PaO2 78mmHg, PaCO2 55mmHg, and HCO3- 30mmol/L respiratory acidosis with full metabolic compensation without hypoxemia.
• Understanding the Influence of Acidosis or Alkalosis.

Oxyhaemoglobin Dissociation Curve:

• Left Shift (Increased Affinity for Oxygen):*
• Increased O2 affinity
• Decreased O2 unloading to tissues
• Influenced by increased pH, decreased temperature, decreased 2
• 3-DPG, and decreased PCO2.
• Right Shift (Decreased Affinity for Oxygen):*
• Decreased O2 affinity
• Increased O2 unloading to tissues
• Influenced by decreased pH, increased temperature, increased 2
• 3-DPG, and increased PCO2.

High Flow Nasal Cannulae (HFNP):

• HFNP uses larger prongs for oxygen flow up to 60L/min.
• HFNP generates low levels of Positive End-Expiratory Pressure (PEEP).
• HFNP can reduce tachypnoea and Work of Breathing (WOB).
• HFNP prevents CO2 rebreathing, decreasing PaCO2.
• HFNP is well-tolerated and must be used with humidification.

Ventilation Terminology:

• FiO2 is the fraction of inspired oxygen (O2 concentration from 30-100%)
• Respiratory Rate (RR) is the number of breaths per minute
• Tidal Volume (Vt) is the volume of gas moved into or out of the lungs during a single normal inspiration and expiration
• Minute Volume (Ve) is the volume of gas moved in and out of the lungs in one minute
• Calculated using: Vt × RR
• Positive End Expiratory Pressure (PEEP) or End-Expiratory Positive Airway Pressure (EPAP) is the amount of pressure remaining in the lungs/alveoli at the end of expiration
• Pressure Support (PS) is the push of air to help the patient with spontaneous breathing
• Peak Inspiratory Pressure (PIP) is the maximum pressure of air during inspiration

Non-Invasive Ventilation (NIV):

• Involves CPAP (Continuous Positive Airway Pressure) and BiPAP (Bi-level Positive Airway Pressure).
• Requires the patient to trigger breathing with a patent airway and adequate consciousness.
• Preserves the patient’s ability to speak, swallow, cough, and clear secretions.
• Reduces the risks of endotracheal intubation.
• May have increased FiO2 or pressure controls.

Continuous Positive Airway Pressure (CPAP):

• Indications:*
• ARDS, cardiac pulmonary edema (HF), bilateral diffuse pneumonia, Type 1 respiratory failure (PaO2 < 60mmHg), and OSA.
• Benefits:*
• PEEP reduces the work of breathing required on inspiration.
• Facilitates alveoli recruitment, helping to shunt airways open and prevent collapse (atelectasis).
• Adds to respiratory reserve volume.
• Improves cardiac performance by reducing ventricular preload and left ventricular afterload useful in Pulmonary Oedema.

BiPAP - Biphasic Positive Airway Pressure:

• Uses two pressure levels: inspiratory positive pressure airway pressure (IPAP) and expiratory positive airway pressure (EPAP/PEEP).
• Indications:*
• COPD, Type 2 (hypercapnic) respiratory failure (PaCO2 > 60mmHg), Obesity hypoventilation.
• Benefits:*
• Similar benefits to CPAP but includes pressure support on inspiration.
• Significantly decreases the work of breathing.
• Reduces inspiratory muscle fatigue by adding inspiratory positive pressure, thus reducing dyspnea.
• Increases tidal volume, which enhances CO2 elimination and reverses acidaemia.

Nursing monitoring requirements:

• Patient and carer education of need for NIV
• Mask fit and skin integrity
• Regular recording of vital signs like oxygen saturation
• cardiovascular observations and NIV settings
• Time on and time off machine.
• Patient comfort.

Invasive Ventilation

• Involves intubated patients requiring synchronized intermittent mandatory ventilation with pressure-regulated volume control (SIMV-PRVC).
• Settings:*
• RR, FiO2, PEEP, Vt, PS, and other settings.
• Synchronized with patient’s intrinsic breathing.
• Pressure support is similar to BiPAP.
• Volume control adjusts the volume of mandatory breaths, ensuring sufficient air delivery with each breath.
• Pressure is regulated to prevent barotrauma and is set as an alarm at 35cm H2O, cutting off if the pressure reaches 40cm H2O.
• Understanding the use of pressure support ventilation (PSV) as a Weaning mode, where patient must trigger every breath
• The ventilator delivers a pressure boost to patient own breath and is like BIPAP.

Monitoring:

• Accurate record of pressures
• Assess for equipment malfunctions
• Assess for respiratory and haemodynamic stability and coordination with the ventilator.

Intubation - Endotracheal Tube (ETT):

• Indications and routes: intubation is required in instances of cardiorespiratory arrest multi-organ failure or in patients with diminished conscious states There are 2 routes of intubation: (Orotracheal and Nasotracheal)
• ETT size ranges from 2.0-12.0 (0.5 increments), length and radiopaque line
• Includes an inflated cuff and pilot tube, a connector (standard 15mm), and subglottic suction.

Risks of Intubation:

• Infection (pneumonia or Ventilator Acquired Pneumonia (VAP))
• Tooth dislodgement
• Bleeding
• Perforation of the oropharynx
• Oesophageal placement and Vocal cord damage
• Tracheal mucosa ischaemia due to increased cuff inflation pressures.

Tracheostomy:

• Indicators for Tracheostomy:*
• To bypass upper airway obstruction in cases of tumors or foreign bodies.
• Used in patients with uncontrolled aspiration, prolonged intubation, and those needing long-term ventilator support.
• Useful in facilitating weaning from ventilator support.

Assessing an Artificial Airway (ETT, NTT, or Tracheostomy):

• Assessing type, size, length at teeth, and the pressure of tube (cuff)
• Assessing for tapes or sutures), suctioning, presence of secretions, and cough reflex.
• Managing the site of tracheostomy by clearing debris and wound Ensuring that the dressing is in place

Checking Correct Placement:

• Confirm bilateral breath sounds and chest movement.
• Auscultate over the epigastrium.
• End-tidal CO2 confirmation is the gold standard.
• Use capnography for continuous monitoring.
• Confirm placement with CXR 2cm above the carina.

Documenting Artificial Airways:

• Include patient airway size (ETT or tracheostomy), length at teeth, cuff pressure, and securing method. -Note the frequency and quantity of secretions.

Bedside Emergency Equipment:

• Includes different sizes of ETT or tracheostomy tubes
• Bag valve mask (BVM) without face mask, face masks appropriate for BVM
• Cuff monitor device (manometer) and a 10ml syringe
• Tracheostomy dressing equipment and securing devices
• Suctioning and Oral care.

Nursing Responsibilities:

• Tracheostomy dressings should not be changed for 24 hours postoperatively due to dislodgement risks.
• A second nurse is needed to assist during stabilising, pressure care and tracheostomy changes.

Suctioning via ETT or Tracheostomy:

• It is necessary to clear accumulated pulmonary secretions.
• Indications:*
• Audible upper respiratory tract noises
• Deterioration of ABGs or SpO2 suspected aspiration
• Clinically apparent increased work of breathing
• Specific CXR changes a sputum specimen, increased pressures during volume control or decreased tidal volume on pressure regulated
• Cough, as part of a respiratory assessment

This lecture analyses health data using arterial blood gas samples and respiratory and metabolic conditions. It covers ventilation techniques (invasive & non-invasive) and airway management. Learn high flow nasal prongs, ventilator terminology, CPAP, BiPAP, and the importance of managing acidotic or alkalotic conditions.