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 99F

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
Hill et al. Crit Care Med 2007;35:2402-7
●
Hypoxemic Resp Fail
» ALI/ARDS
» Severely ill
» Metabolic acidosis
» P/F < 150 after1hof
NPPV
» Pneumonia
» Shock
NPPV: Predictors of Failure
●
COPD
» pH < 7.25
» RR > 35/min
» Severely ill
» Asynchrony
» GCS < 11
» Poor tolerance
Hill et al. Crit Care Med 2007;35:2402-7
●
Hypoxemic Resp Fail
» ALI/ARDS
» Severely ill
» Metabolic acidosis
» P/F < 150 after1hof
NPPV
» Pneumonia
» Shock
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
Airway Pressure (cm H2O)
Trigger, Target, Cycle
Respiratory Cycle
Cycling
Inspiration
Triggering
Time (sec)
Expiration
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 characteristics
Gas 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
Modes of Support
Synchronized intermittent mandatory
ventilation
Spontaneous
SIMV + PSV
Volume-cycled breath
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:
Female IBW in lb:
106 + [6 x (height in inches – 60)]
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
What monitoring and assessment is
needed after initiation of mechanical
ventilation?





Chest radiograph
Vital signs
SpO2
Patient-ventilator
synchrony
ABG



Inspiratory pressures
Auto-PEEP
Ventilator alarms
Proving Endotracheal Intubation

Soft Signs





Equal breath sounds
Easy ventilation
No stomach bubbles
Adequate oxygenation
Firm Signs


Radiograph
Expired CO2
Inspiratory Pressures

Peak inspiratory pressure (Ppeak)

Inspiratory plateau pressure (Pplat)

Indicator of alveolar distension
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
What problems are present?






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
®
Waveform showing decreased lung compliance
‘Square
wave’ flow
pattern
Ppeak
Pplat
Pres
Case Study
What changes in ventilator settings would
decrease inspiratory plateau pressure?
Current





Ventilator Settings
Assist control (volume)
FiO2 1.0
Tidal volume 550 mL
RR 10/min
PEEP 5 cm H2O
®
Case Study
What changes in ventilator settings would
improve oxygenation?
Current





Ventilator Settings
Assist control (volume)
FiO2 1.0
Tidal volume 550 mL
Respiratory rate 10 breaths/min
PEEP 5 cm H2O
®
NIH ARDS Network trial
NEJM 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





Mode
FiO2
Tidal volume
Rate
PEEP





AC
1.0
700 mL
12 breath/min
5 cm H2O
Case Study
What are the major problems?






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
Low blood pressure alarm sounding
What do you do next?
®
Case Study
What are possible causes of the patient’s
hypotension?





Positive intrathoracic pressure (venous
return )
Auto-PEEP
Hypovolemia
Tension pneumothorax
Myocardial ischemia
®
Auto-PEEP

Diagnosis

Measurement

Waveform analysis
Gas
flow
Auto-PEEP
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
What immediate changes in ventilator
settings should be made?
Current





Ventilator Settings
AC
FiO2 1.0
Tidal volume 700 mL
Respiratory rate 12 breaths/min
PEEP 5 cm H2O
®
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:


NPPV is best used in:


support of oxygenation and ventilation and reduction
in work of breathing
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