Respiratory Failure: Modes of Ventilatory Support Flashcards
What is ventilation?
- The cyclic process of exchange of air
- In physiology, the exchange of air in the lungs with atmospheric air which has a higher oxygen and lower carbon dioxide content
Ventilator support is indicated in?
- Inadequate alveolar ventilation (Acute ventilatory failure)
- Excessive work of breathing
- Inadequate lung expansion
- Insufficient respiratory drive
- Hypoxemia
- Airway protection
What are the physiologic goals of respiratory support?
- To improve gas exchange – Oxygenation – CO2 removal
- To help maintain acid base balance
- To optimize lung volumes – Improve V/Q distribution
- To reduce the work of breathing
What are the types of Ventilatory support?
• Non-invasive • Invasive
Non-invasive uses what two techniques?
• Negative pressure • Positive pressure
Negative pressure non-invasive is done via?
– Iron lung (tank)
– Cuirass (turtle)
– Poncho (pneumosuit)
Positive pressure non-invasive is done via?
–Face mask
–Nasal masks
– High Flow Nasal Cannula (HFNC)
–Helmet
–Mouthpiece/sip ventilation
Explain how positive pressure non-invasives work?
- A pressure is delivered either in a continuous fashion, CPAP or split between inspiration and expiration (BiPAP)
- The patient generates a tidal volume depending on their respiratory mechanics
- Can be used in acute or chronic respiratory failure
Modes of NIV? (noninvasive)
- Conventional oxygen therapy (COT) – Nasal oronasal full facemask
- Continuous positive airway pressure (CPAP)
- Bi-level positive pressure (BiPAP)
- High frequency nasal cannula (HFNC) for acute respiratory failure
- Helmet ventilation
Indications for use of NIV?
– PaO2/FiO2 < 200 mmHg
– Hypercapnia PaCO2 > 45 and 7.3 < pH < 7.35
– Severe dyspnea/↑ WOB
– Tachypnea RR > 24 breaths/min
– Alert/cooperative
– Unable to protect airway
Use of NIV positive pressure ventilation criteria?
– Clinical criteria • Alert • Cooperative • Able to protect airway • Demonstrate: moderate to severe respiratory distress • Increased dyspnea • Tachypnea • Use of accessory muscle • Paradoxical breathing pattern
– Blood gas criteria • PaCO2 > 45 mmHg (> 6.0 kPa) and pH < 7.35, or PaO2/FiO2 < 200
Roles for NIV?
- Primarily used in acute respiratory failure due to: – Acute exacerbation of COPD – Acute CHF/pulmonary edema
- Other roles: – Weaning strategy in invasive mechanical ventilation – Prevent post-extubation failure – Chronic neuromuscular disease – Neutropenic patients with fever and pulmonary infiltrate – Chronic restrictive thoracic disorders – Palliate symptoms in end stage disease
NIV positive pressure ventilation is the gold standard for? failure rate?
Gold standard” therapy in acute hypercapnic exacerbation of COPD
Has a failure rate of around 20% in acute hypercapnic respiratory failure
Clinical Goals for NIV?
- To correct hypoxemia
- To correct respiratory acidosis
- To improve V/Q (prevent/reverse atelectasis)
- To reduce myocardial oxygen consumption
- To stabilize the chest wall
- To reduce intracranial pressure
- To buy time for therapies to work/recover
Keys to success for NIV? Need to monitor what in the beginning?
- Early Delivery in the course of respiratory failure
- Very cooperative patient
- Younger age
- Lower acuity of illness (APACHE Score)
- Appropriate blood gas criteria
- Good interface fit (less chance of leaking, intact dentition)
Need to closely monitor ABG, HR, RR within the first ½ to 1hr and closely thereafter
Do not use NIV in a patient who? examples?
Do not use in patient who would be more safely managed invasively.
For example: • Overt respiratory distress • Cardiac/respiratory arrest • Shock • Smoke inhalation (risk of airway edema) • Severe facial trauma or deformity • Glasgow coma scale score <10 • Gastrointestinal bleed Don’t use if uncooperative or agitated Don’t use if unable to protect airway
Adverse Side Effects & Complications of NPPV?
Key facts about invasive ventilation?
- A form of supportive care – a bridge
- Need to identify and address the primary gas exchange derangement of the patient
- DOES NOT TREAT the underlying illness
What is themajor cause for invasive ventilation?
Acute Respiratory Failure is the major indication for mechanical ventilation
What are the two basic causes of acute respiratory failure?
Two basic causes:
A. Hypoxic Respiratory Failure Failure to adequately oxygenate – ineffective gas exchange 1. V/Q mismatch 2. Shunt 3. Decreased FRC
B. Hypercapnic Respiratory Failure Failure to adequately ventilate 1. Reduced respiratory drive 2. Respiratory muscle fatigue 3. Decreased compliance Chest wall lung parenchyma
What four things in the ventilatory cycle are we looking at to see if we need volume targeting or pressure?
Volume Targeted vs. Pressure Targeted Ventilatory Cycle
- Trigger – what initiates the breath – Patient vs. Ventilator: Machine timer ∆ pressure ∆ flow
- Delivery – what’s the target – Volume vs. Pressure
- Cycling – what terminates the breath – Volume time flow pressure
- Expiration
What are the clinical decisions to make with mechanical invasive vents?
- Ventilatory mode (volume or pressure)
- Inspired oxygen fraction (FIO2)
- Tidal volume
- Respiratory rate
- Positive end expiratory pressure (PEEP)
- Inspiration/expiration ratio
- Inspiratory flow rate/delivery
Ventilatory, Volume vs pressure?
Explain volume vs pressure targeted breaths?
Whats a mandatory breath? Spontaneous breath?
Mandatory breath: An assured breath that occurs at a minimum respiratory rate and preset volume or pressure
Spontaneous breath: Determined by patient effort for initiation and duration and is not assisted
What are volume targetted modes?
• Volume-targeted modes:
– Controlled mechanical ventilation (CMV)
– Assist/control (AC)
– Synchronized Intermittent Mandatory Ventilation (SIMV)
What are common pressure targeted modes?
– Pressure-support ventilation (PSV)
– Pressure control ventilation (PCV)
– Pressure-regulated volume control
– Volume assured pressure support
What is PEEP? What does normal PEEP look like?
Positive End Expiratory Pressure
- Improves airflow → improves oxygenation
- Prevents atelectasis at end expiration
- Helps to recruit collapsed alveoli
- Helps to lower FiO2 need thereby minimizes risk of oxygen toxicity
Auto PEEP?
Strategies to lower FiO2?
- PEEP
- Maximize O2 delivery/maximize PvO2
- Lower VO2 to maximize PvO2
- Prone positioning if PaO2/FiO2 < 150
Common parameters monitored during mechanical ventilation?
- Clinical: Physical exam – Vital signs – Patient’s WOB – EKG
- Ventilator – RR, VT (tidal volume), VE (minute ventilation) – Airway pressure, especially the plateau (goal <30), peak waveforms – Compliance (static/dynamic)
- Pulse oximetry/ABG
Problems to address with Oxygenation using mechanical ventilation?
- Barotrauma: Excessive airway pressure Try to keep plateau pressure < 30 mm H2O Try to keep driving pressure (Plat-total PEEP) < 15
- Volutrauma: over distension of lung units Use low tidal volume (LTV) based on ideal body weight May need to accept a degree of CO2 retention: permissive hypercapnia
- Atelectotrauma Repetitive openings and closings of terminal lung units Treatment: Positive End Expiratory Pressure to prevent alveolar collapse
- Biotrauma Local and systemic inflammatory response to mechanical ventilation
Mechanical ventilation requires? Associated with?
Requires endotracheal intubation or tracheostomy
Associated with numerous complications:
Infections: Ventilator Associated Pneumonia (VAP) from bypassing host defense mechanism Neurologic: Cognitive Decline, Delirium Respiratory: Ventilator Induced Lung Injury (VILI) Musculoskeletal: Critical Care Myopathy
Complications with mechanical ventilation
• Barotrauma • Volutrauma • Atelectrauma • Oxygen toxicity • Hypotension/decreased cardiac output • Critical illness myopathy • Auto-PEEP • Increased intracranial pressure • Renal and hepatic dysfunction • Gastric distension
Strategies for minimizing the risk of barotrauma?
- In severe air flow obstruction, one may need to consider deliberate hypoventilation eg, permissive hypercapnia, although recently permissive hypercapnia use has raised some red flags regarding its physiologic effects
- In acute hypoxemic respiratory failure, low tidal volume (6±2 cc/Kg) and high rate (26-35) should be utilized when PEEP requirement is high
Explain weaning in mechanical ventilation?
Should be protocol-based considerations • Lung injury stable or resolving • Gas exchange adequate PEEP < 5-8 cm H2O and FiO2 ≤ 0.4-0.5 • Hemodynamically stable • Good cough • Suction frequency < every 2 hours • Capable of initiating spontaneous breaths • ± RSBI (Rapid Swallow Breathing Index) • PaO2/FiO2 ≥ 200
If above are met then consider spontaneous breathing trial
Liberation from mechanical ventilation?
- Use a ventilator liberation protocol
- Use protocols attempting to minimize sedation
- Initiate spontaneous breathing trials (SBT) conducted with inspiratory pressure augmentation (5-8 cm H2O)
- After passing spontaneous breathing trial (SBT) extubate to preventative NIV
- Use rehabilitation protocols directed toward early mobilization
spontaneos breathing trials?
T-piece (use in all patients who require MV for Heart failure)
CPAP or pressure support ventilation
Automated tube compensation
ExtraCorporeal Membrane Oxygenation (ECMO) explain?
