Week 3: Non Invasive Ventilation Flashcards
What are the types of ventilation failure?
Type 1 respiratory failure –oxygen failure
Type 2 hypercapnoeic respiratory failure -Effects on carbon dioxide
What is ventilation?
The process of allowing fresh air into the lungs and exhaling carbon dioxide (byproduct of metabolism)
How does inspiration occur?
Diaphragm flattens and ribs elevate → ↑ volume of the thoracic cavity
Increased intrathoracicvolume → ↓intrathoracic pressure
Intrathoracic volume falls below atmospheric pressure and because of this pressure difference, air flows into the lungs
How does expiration work?
Inspiratory muscles relax
Natural elastic recoil of the lungs reduces the volume of the thoracic cavity
↓volume of the thoracic cavity → ↑intrapulmonary pressure.
Air moves out of lungs because the pressure in the alveolus is greater than atmospheric pressure.
What is airway resistance?
Refers to the forces that oppose airflow within the respiratory passageways
Increased resistance increases work of breathing
What are factors which increase work of breathing?
Bronchoconstriction/dilation
Patency of ETT
Size of ETT
What is lung compliance?
Refers to the ease at which the lungs can be expanded e.g. a balloon that is easy to inflate is very compliant.
What are conditions which affect lung compliance?
Pulmonary oedema
Adult Respiratory Distress Syndrome (ARDS)
Pulmonary fibrosis
What is tidal volume?
Volume of one breath
What is minute ventilation?
Total air inhaled and exhaled each minute
How do you calculate minute ventilation?
MV = VT X RR
What factors could change RR?
Increase: pain, exertion/exercise, stress/anxiety, medications (activation of SNS)
Decrease: medication (morphine), decrease LOC
What factors could affect tidal volume?
Injury: fractured rib Pneumothorax LOC Positioning: position of diaphragm (abdomen may impede), sit patient up Lung disease
What is functional residual capacity?
Amount of air in lungs at end of a normal expiration
What is anatomical dead space?
Volume of air that takes no part in gas exchange nose, pharynx larynx, trachea, etc
What is alveolar ventilation?
Volume of air that actually reaches alveoli
How do you calculate alveolar ventilation?
Alveolar ventilation = TV - dead space ventilation
How is gas exchange explained by Dalton’s law and Henry’s law?
Dalton’s law: pressure gradient. Higher O2 partial pressure in alveoli than capillaries –> O2 moves into blood. Opposite for CO2 partial pressure
Henry’s law: CO2 dissolves well in water (more soluble than O2)
How is O2 transported in the blood?
97% carried on the Hb
3% dissolved in the plasma
Portion dissolved in plasma can be measured as partial pressure of arterial oxygen (PaO2) done by ABG analysis
Include more on gas exchange
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Include pulmonary oedema
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Include V/Q relationship
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What are first line pH buffers?
H+in the plasma is buffered by bicarbonate in the plasma
H+ + HCO3H2CO3CO2+ H2O
Some H+enters the cells and is buffered by intracellular bicarbonate
Haemoglobin
Albumen and globulin
What are second line pH buffers?
If the amount acid exceeds the capability of the first line buffers the increased H+is detected by the chemoreceptorsin the medulla and the rate and depth of breathing is increased
Occurs when the ph <7.35
Increased rate and depth of breathing increases carbon dioxide removal reducing carbonic acid and H+load
What are third line pH buffers?
Renal mechanisms is powerful but slower
Peak in 72 hours
Retain and excrete both H+and bicarbonate to bring pH back to normal
What are the 5 steps of an ABG analysis?
Step one: Examine the pH Step two: Compare the CO2 and the pH Step 3: Consider the HCO3 and Base excess in conjunction with the pH Step 4: Assess the oxygen levels Step 5:Compare the PaO2 and SaO2
What are the causes of respiratory acidosis?
Respiratory disease (pneumonia, COPD), over-sedation
What are the causes of respiratory alkalosis?
Overventilation due to pain or emotional distress
What are the causes of metabolic acidosis?
DKA
Shock
What are the causes of metabolic alkalosis?
Chronic vomiting
Sodium bicarb overdose
What are the indications of Continuous Positive Airway Pressure?
Acute exacerbations of COPD Asthma Acute cardiogenic pulmonary oedema Hypoxemic respiratory failure Post-op respiratory failure - atelectasis Obstructive sleep apnoea
How does Continuous Positive Airway Pressure work?
Gas delivered at constant preset pressure during both inspiration and expiration
Ventilation (RR and TV) controlled by patient
Supports ventilation, doesn’t replace
Decreases work of breathing to increase TV upon inspiration
Inhibits paradoxical chest movements
Increases functional residual capacity:
Splints airway to keep open
Forcing open collasped alveoli, preventing collaspe at end expiration
Improved amount of O2 which crosses alveolar/capillary membrane
What is FiO2?
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Include PEEP
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What is Bilevel Positive Airway Pressure?
Delivers positive pressure in two phases to a spontaneously breathing patient
Includes: inspiration positive airway pressure (IPAP) during inhalation, and expiratory positive airway pressure (EPAP) during exhalation
What are the indications for Bilevel Positive Airway Pressure?
Acute respiratory failure, type 2 Chronic airway limitation Pneumonia Congestive heart failure Acute pulmonary oedema Atelectasis Neuromuscular disease Sleep apnoea Poor candidates for mechanical ventilation
How does Bilevel Positive Airway Pressure work?
As patient breathes, a positive pressure gradient is established until the preset inspiratory pressure support is reached. Enhances TV
Detects reducing amount of airflow in, cuts out on expiration to allow natural elastic recoil to PEEP level
Promotes CO2 removal
What is IPAP and what does it do?
Inspiratory Positive Airway Pressure: Supports breath Improves TV Maximises removal of CO2 Reduces work of breathing Opens airways and alveoli
What is EPAP and what does it do?
Expiratory Postiive Airway Pressure:
Exerts positive intrapulmonary pressure on expiration
Increases functional residual capacity
Recruits underinflated lung tissue
What are the physiological effects of Bilevel Positive Airway Pressure?
Increased functional residual capacity
Reduced respiratory muscle work
Atelectatic alveoli opened –> improved compliance
Improved oxygenation
Assistance inhaling –> increased transpulmonary pressure –> inflation of lungs and augmentation of alveolar ventilation –> augmentation of TV
Improved cardiac performance: reduction in preload and afterload reducing myocardial oxygen consumption
Upper airway able to warm and humidify gas
What are the contraindications of Bilevel Positive Airway Pressure?
Respiratory arrest Facial trauma/surgery Excessive secretions/inability to clear Risk of aspiration Low GSC/agitation Severe hypoxia Haemodynamically unstable Upper GIT bleeding Upper airway obstruction
How does Continuous Positive Airway Pressure improve oxygenation?
Splints open airways
Forces alveoli open for gas exchange
Pushes fluid back into capillaries
What is the assessment and management of a patient receiving Continuous Positive Airway Pressure?
Assess: tolerance, mucous membranes, pressure areas, vitals, hourly ABGs for CO2, O2 and pH, mask fit and seal
Management: reassure, educate, plan breaks, consider humidifier or dry mouth spray, dressings for pressure areas, positioning
What is the usual range for Continuous Positive Airway Pressure?
5-15 cmH2O
What variables need to be set on a Continuous Positive Airway Pressure device?
Oxygen %
PEEP level
What paediatric medical conditions are treated with Continuous Positive Airway Pressure?
Altered control of breathing e.g. Congenital Central Hypoventilation Sydnrome
Neuromuscular weakness e.g. Duchenne muscular dystrophy, spinal muscular dystrophy
Upper spinal cord injury
Upper airway obstruction (non-acute) e.g tracheobronchomalacia, some craniofacial abnormalities
Chronic lung disease
Obstructive sleep apnoea
What are the four variable in Bilevel Positive Airway Pressure?
Expiratory positive airway pressure
Inspiratory positive airway pressure
Frequency of cycling or breath rate at 4-30 cycles per minute
Proportion of each respiratory cycle spent in IPAP, 10-90%
What are the four modes of Bilevel Positive Airway Pressure?
Spontaneous
Spontaneous/timed
Timed
Continuous Positive Airway Pressure
What are the complications of non-invasive positive pressure ventilation?
Decreased CO Ill fitting mask and leaks Decreased patient compliance Skin irritation Dry mucous membranes Gastric distension Aspiration Barotrauma and pneumothorax
What primary assessment needs to be performed on a patient with non-invasive positive pressure ventilation?
A and B: RR, depth, work of breathing Patient-ventilator synchrony Chest wall movement Use of accessory muscles Continuous pulse oximetry ABG analysis
C:
BP, HR, JVP, rhythm
D:
AVPU or GSC
E
What is the nursing management for a person with non-invasive positive pressure ventilation?
Oral care:
Mouth washes
Need to decide if it is appropriate to remove mask, ventilation takes priority
Pressure relief from mask:
Breaks
Padding
Nasal care:
Humidification devices
Comfort: Positioning Promote secretion removal Analgesia Psychological support
Decrease O2 consumption: temperature control
Nutritional support and adequate phosphate levels
What are the indications that non-invasive positive pressure ventilation is not working?
Unstable cardiovascular system
Deteriorating mental state
Increasing RR
Hypoxia and increased CO2
