mechanical ventilation in the icu: what you need to know behrouz jafari, m.d pulmonary/critical care...
Post on 29-Dec-2015
213 Views
Preview:
TRANSCRIPT
Mechanical Ventilation in the ICU: What You Need to Know
Behrouz Jafari, M.D
Pulmonary/Critical Care and Sleep Medicine
UCI-VA Long Beach
Mechanical Ventilation
NIPPV
When to intubate
Setting the ventilator
Complications of mechanical ventilation
Weaning
Case Study
65-year-old with COPD exacerbation using accessory muscles and wheezing after 2 bronchodilator treatments
HR 110/min, BP 160/110 mm Hg, RR 30/min, T 99F
ABG on 3 L/min O2: pH 7.24, PCO2 60 mm Hg, PO2 65 mm Hg
What type of respiratory support should be initiated?
NIPPV
NPPV: Evidence-Based Recommendations:
● Recommended (1A)• » Severe COPD exacerbation (pH < 7.35)• » Cardiogenic pulmonary edema
– No shock or ACS requiring revascularization● Suggested (2B- 2C)‐
• » Immunocompromised hypoxemic RF (2C)• » Post- op‐ respiratory failure (2C)
– abdominal, lung resection• » Facilitation of extubation in high- risk‐ or COPD
• Keenan et al. Can Med Assoc J 2011
NIPPV
Contraindications Poor Mental Status Excess Secretions Severe Respiratory Failure Shock Inability to Protect Airway
Case Study
ABG on 3L/min O2: pH 7.24, PaCO2 60 mm Hg, PaO2 65 mm Hg
HR 110/min, BP 160/110 mm Hg,RR 30/min
How should the patient be monitored?
NPPV: Monitoring
Patient Mask comfort Tolerance Resp distress RR, VS
» Accessory muscle use
» Abdominal
paradox
● Ventilator Air leak Adequacy of IPAP
(Vt), EPAP Pt- ‐vent synchrony SpO2; ABG (2 hr)
● Setting » ICU to start »SDU if stable
Case Study
After 1 hr of NPPV, the patient has not improved
Arterial blood gas on 40% O2: pH 7.20, PaCO2 65 mm Hg, PaO2 58 mm Hg
HR 120/min, BP 142/98 mm Hg, RR 40 /min
What is the next step?What predicts success or failure?
NPPV: Predictors of Failure
● COPD» pH < 7.25» RR > 35/min» Severely ill» Asynchrony» GCS < 11» Poor tolerance
● Hypoxemic Resp Fail» ALI/ARDS» Severely ill» Metabolic acidosis» P/F < 150 after 1h of NPPV» Pneumonia» Shock
Hill et al. Crit Care Med 2007;35:2402-7
NPPV: Predictors of Failure
● COPD» pH < 7.25» RR > 35/min» Severely ill» Asynchrony» GCS < 11» Poor tolerance
● Hypoxemic Resp Fail» ALI/ARDS» Severely ill» Metabolic acidosis» P/F < 150 after 1h of NPPV» Pneumonia» Shock
Hill et al. Crit Care Med 2007;35:2402-7
Case Study
Orotracheal intubation is performed
What ventilator mode should be selected?
What tidal volume is optimum?
What rate of ventilation should be set?
Invasive Mechanical Ventilation
Breath Characteristics
Triggering
Cycling
Respiratory Cycle
ExpirationInspiration
Time (sec)
Air
wa
y P
res
su
re (
cm
H2O
)Trigger, Target, Cycle
Breath characteristics
Trigger•Controlled - machine timer
•Assisted/supported - patient effort
–Pressure trigger: Pt effort pressure drop in vent circuit vent response
–Flow trigger – pt effort draws gas out of a continuous flow through the vent circuit vent response
Breath characteristicsGas Delivery (Target)
Breath characteristics
Cycle (turning breath off)
•Three common types–reach set volume–reach set time–reach certain flow reduction
5 Basic Breath
5 Basic Breath
5 Basic Breath
5 Basic Breath
Synchronized intermittent mandatory ventilation
SIMV + PSV
Modes of Support
Volume-cycled breathSpontaneous
Setting the Ventilator
Mode
FiO2
Rate
Tidal Volume
PEEP
Initiation of Mechanical Ventilation
Initial Ventilator Settings Minute Ventilation
Metabolic rate is directly related to body surface area (BSA)
Males: = 4 x BSA
Females: = 3.5 x BSA
Nomogram
Initiation of Mechanical Ventilation
Initial Ventilator Settings Minute Ventilation based on BSA
Example: Female patient with an estimated BSA of 2.0 m2
= 3.5 x 2.0 m2
= 7.0 L/min
A patient’s requirements increase by 9% for every 1° C increase on body temperature
Initiation of Mechanical Ventilation
Initial Ventilator Settings Minute vent.= RR TV
Tidal Volume VT for an adult is 6 – 8 ml/kg of IBW
Ideal Body Weight Calculation
Male IBW in lb:106 + [6 x (height in inches – 60)]
Female IBW in lb: 105 + [5 x (height in inches – 60)]
Oxygen Supplementation
Start with 100% after intubation
FiO2 > 60% is (probably) toxic.
Need to balance potential toxicities Oxygen PEEP
Case Study
Chest radiograph Vital signs SpO2
Patient-ventilator synchrony
ABG
Inspiratory pressures Auto-PEEP Ventilator alarms
What monitoring and assessment is needed after initiation of mechanical
ventilation?
Proving Endotracheal Intubation Soft Signs
Equal breath sounds Easy ventilation No stomach bubbles Adequate oxygenation
Firm Signs Radiograph Expired CO2
Peak inspiratory pressure (Ppeak) Inspiratory plateau pressure (Pplat)
Indicator of alveolar distension
Inspiratory Pressures
Compliance and Resistance
High Peak/High Plateau = decreased compliance
pneumonia, CHF, Pleural Effusion, Pneumothorax, ARDS, ascites, Chest wall abnormalities
High Peak/Low Plateau = increased resistance secretions, bronchospasm, tubing abnormalities
Case Study
18-year-old female found unresponsive at a party (wt 60 kg, ht 64 inches [162.6 cm])
Vomitus in pharynx, difficult intubation
SpO2 87-88% on 100% oxygen
Case Study
Mode FiO2 Tidal volume Rate PEEP
Assist control (volume) 1.0 550 mL 10 breaths/min 5 cm H2O
®
Ideal body wt = 56 kg
Case Study
Mode FiO2 Tidal volume Rate PEEP
Assist control (volume) 1.0 550 mL 10 breaths/min 5 cm H2O
®
Ideal body wt = 56 kg
High pressure alarm sounding
Case Study
SpO2 88% (FiO2 1.0) Blood gas: pH 7.38, PaCO2 36 mm Hg,
PaO2 57 mm Hg Ppeak 52 cm H2O Pplat 48 cm H2O Auto-PEEP 0 cm H2O Patient’s RR 18/min
®
What problems are present?
Waveform showing decreased lung compliance
Ppeak
Pplat
Pres
‘Square wave’ flow
pattern
Case Study
Current Ventilator Settings Assist control (volume) FiO2 1.0 Tidal volume 550 mL RR 10/min PEEP 5 cm H2O
®
What changes in ventilator settings would decrease inspiratory plateau pressure?
Case Study
Current Ventilator Settings Assist control (volume) FiO2 1.0 Tidal volume 550 mL Respiratory rate 10 breaths/min PEEP 5 cm H2O
®
What changes in ventilator settings would improve oxygenation?
NIH ARDS Network trialNEJM 2000;342:1301
Case Study
70-year-old with long smoking history failed NPPV for respiratory distress
Intubated, sedated, and receiving mechanical ventilation
Wt 75 kg, ht 69 inches [175.3 cm]) IBW 70 Kg
Case Study AC 1.0 700 mL 12 breath/min 5 cm H2O
Mode FiO2 Tidal volume Rate PEEP
Case Study
Blood gas: pH 7.20, PaCO2 60 mm Hg, PaO2 215 mm Hg
Pplat 28 cm H2O, Ppeak 50 cm H2O Auto-PEEP 8 cm H2O I:E = 1:1.5 RR 18/min BP 70/30 mm Hg, HR 130/min
®
What are the major problems?
Low blood pressure alarm sounding
What do you do next?
Case Study
Positive intrathoracic pressure (venous return )
Auto-PEEP Hypovolemia Tension pneumothorax Myocardial ischemia
®
What are possible causes of the patient’shypotension?
Diagnosis Measurement Waveform analysis
Auto-PEEP
Auto-PEEP
Gasflow
Auto-PEEP
Waveform showing increased airways resistance
Ppeak
Pplat
Pres
Recognizing prolonged expiration (air trapping)
Recognize airway obstruction
when
Expiratory flow quickly tapers off and then enters a prolonged
low-flow state without returning to baseline (auto- PEEP)
This is classic for the flow limitation and decreased lung
elastance characteristic of COPD or status asthmaticus
Auto-PEEP
Consequences
Inspiratory pressures
Hypotension
Worsened oxygenation
Interventions to decrease auto-PEEP
Respiratory rate
Tidal volume
Gas flow rate
®
Case Study
Current Ventilator Settings AC FiO2 1.0 Tidal volume 700 mL Respiratory rate 12 breaths/min PEEP 5 cm H2O
®
What immediate changes in ventilator settings should be made?
Obstructive Airway Disease
Initial tidal volume 6-8 mL/kg Optimize expiratory time Beware of auto-PEEP Adjust minute ventilation to
low normal pH Treat obstruction with bronchodilators
Mental Status, Sputum Volume & Cough Strength in Weaning
● 3 Risk factors for failure» Poor cough » Heavy endotracheal secretions » Unable to do all 4 tasks (open eyes, follow
with eyes, grasp hand, stick out tongue)● If 2/3 present, 71% sensitive,
81% specific for failure (72h)
Salam et al. Intensive Care Med 2004; 30:1334-9
Spontaneous Breathing Trial● Test of breathing for 30 min with minimal ventilatory
support
● Variables in SBT» Ventilatory support: T-tube or “flow-by”, < 5 cm H2O CPAP,
PSV, or automatic tube compensation
» Termination criteria: RR > 35 bpm x > 5 min, SaO2 < 90%, HR > 140 bpm or sustained HR change > 20% SBP > 180 or < 90 mmHg, increased anxiety or diaphoresis
Ventilator Emergency I
A 55-year-old patient with ARDS suddenly has a dramatic rise in airway pressures and loss of VT and is starting to desaturate quickly. What is the differential diagnosis? Sudden worsening of lung disease Pneumothorax Atelectasis Airway obstruction
Ventilator Emergency II
A 69-year-old schizophrenic woman with aspiration pneumonia starts to become agitated and starts yelling at you (even though she is intubated). Low VT alarms go off. What is the differential diagnosis?
Ventilator Emergency II
A 69-year-old schizophrenic woman with aspiration pneumonia starts to become agitated and starts yelling at you (even though she is intubated). Low VT alarms go off. What is the differential diagnosis? Self-extubation Cuff leak
Ventilator Emergency III
A 23-year-old female asthmatic is being ventilated with PCV. The blood gas is 7.14/75/102 on: AC12/PCV20/TI0.5/FiO235%/PEEP 0. The RR is increased to 20, the VT’s drop, the PCO2 rises, and the patient becomes hypotensive. What is the differential dx? Progressive air trapping Tension pneumothorax
What to Report on Rounds
Ventilator Settings
Minute Ventilation (VE)
Pressures Peak Plateau
Mechanics Compliance Resistance Auto-PEEP
Key Points Goals of NPPV /MV:
support of oxygenation and ventilation and reduction in work of breathing
NPPV is best used in:
Alert, cooperative patient whose condition will improve in 48-72 hours
Use guidelines when initiating MV and adjust based on monitoring
Maintain low TV 6-8 ml/kg IBW and Pplat 30 cm H2O.
Primary determinants of oxygenation: FiO2 and mean airway pressure.
Daily evaluation for possible weaning
top related