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