Principles of Mechanical Ventilation

1
Principles of Mechanical Ventilation

• RET 2284
• Module 4.0 Ventilator Management
• - Initial Assessment

2
Assessment and Documentation of MV

• This module will review the assessment and
  documentation of the patient-ventilator
  interaction in the initial stages

3
Assessment and Documentation of MV

• Verify the physicians order
• Some orders are specific
• Mode, rate, Vt, FiO2, PEEP
• Some orders are flexible
• Desired range of PaCO2 and PaO2
• Initial settings Mode, rate, Vt, FiO2, PEEP
  which can be manipulated to achieve the desired
  blood gas results

4
Assessment and Documentation of MV

• Verify that the ventilator has passed OVP
• OVP Operational Verification Procedure
• Usually an automated self-test
• Usually includes a system-leak test to check the
  integrity of the ventilator circuit, humidifier
  and related equipment
• Done before placing a patient on the ventilator
  for the first time and before reconnecting the
  patient to a ventilator if the circuit has been
  changed or disassembled for any reason
• Must be documented

5
Assessment and Documentation of MV

• Place the patient on the ventilator
• Set parameters on ventilator in accordance with
  the physicians orders
• Connect the patient to the ventilator
• Listen to breath sounds to confirm adequate
  volume delivery and proper placement of ET Tube

6
Assessment and Documentation of MV

• Check patients vital signs especially heart
  rate and blood pressure because these may be
  affected by mechanical ventilation
• Note Positive pressure ventilation can reduce
  venous return to the heart, cardiac output, and
  blood pressure

7
Assessment and Documentation of MV

• Activate alarms (e.g., apnea, low pressure, low
  Vt, and high pressure limits)
• Obtain ABG about 15 minutes after ventilation
• Evaluates effectiveness of ventilation and
  oxygenation

8
Assessment and Documentation of MV

• Chest x-ray Verify ET tube placement
• If the patients clinic presentation indicates a
  need, other determinations my be include
• CBC
• Glucose, sodium, potassium, chloride, CO2, blood
  urea nitrogen, creatinine, phosphate, magnesium
• PT, PTT, platelet count
• Blood, sputum, urine culture

9
Assessment and Documentation of MV

• Documentation of the PT-Vent System
• AKA Vent Check
• Patient information and ventilator settings
  should be documented regularly when a patient is
  receiving ventilator support every 1 4 hours
  depending on the institutions policy
• Documentation is done on a ventilator flow sheet
  electronic or paper record

10
Assessment and Documentation of MV

• Documentation of the PT-Vent System
• AARC Recommendations
• Data relevant to the patient-ventilator system
  check are recorded on the appropriate hospital
  form and become part of the patients medical
  record
• The patient-ventilatory system check includes
  patient information and observations of
  ventilator settings at the time of the check

11
Assessment and Documentation of MV

• Documentation of the PT-Vent System
• AARC Recommendations
• The record should include the physicians order
  for mechanical ventilator settings
• The patient-ventilatory system check includes a
  brief narrative of the clinical observations of
  the patients response to mechanical ventilation
  at the time of the check

12
Assessment and Documentation of MV

• Documentation of the PT-Vent System
• Patient information

13
Patient and ventilator parameters
14
Patient and ventilator parameters

• Patient and ventilator parameters (cont.)

15
Patient and ventilator parameters

• Patient and ventilator parameters (cont.)

16
Patient and ventilator parameters

• Patient and ventilator parameters (cont.)

17
Patient and ventilator parameters

• Patient and ventilator parameters (cont.)

18
Patient and ventilator parameters

• Patient and ventilator parameters (cont.)

19
Assessment and Documentation of MV

• Mode
• Institution determines the method for charting
  mode
• Sensitivity
• Check for autotriggering
• Assess the patients ability to trigger the vent
• Documentation
• Pressure triggered (e.g., - 2 cmH2O)
• Flow triggered (e.g., 2 L/min)

20
Assessment and Documentation of MV

• Tidal Volume, Rate, Minute Ventilation
• Usually displayed digitally
• May be verified with respirometer
• Correcting Tubing Compliance
• Volume loss due to tubing compliance
  (compressible volume)
• Accounts for approximately 1.5 2.5 mL/cm H2O of
  lost volume
• Newer vents automatically compensate

21
Assessment and Documentation of MV

• Determination of Circuit Compressible Volume Loss
• Set VT to 100-200 and PEEP to zero
• Set inspiratory pause at 2 seconds
• Select a minimum flow rate and maximum pressure
  limit
• Occlude Y-connection and initiate a mechanical
  breath
• Record the exhaled volume (ml) and peak
  inspiratory pressure (cm H2O)
• Divide exhaled volume by PIP (V/PIP) circuit
  compression factor
• Multiply compression factor by the patients PIP
  (PIP minus PEEP if PEEP is used)
• Example
• Circuit compression factor 150 ml / 50 cm H2O
  3 ml/cm H2O
• Circuit compression volume 3 ml/cm H2O x (60 cm
  H2O PIP 10 cm H2O PEEP)
• 3 ml/cm H2O x 50 cm H2O 150 ml (circuit
  volume Loss)

22
Assessment and Documentation of MV

• Alveolar Ventilation
• Because of the use of HMEs and other circuit
  adapters that add mechanical dead space to the
  ventilator circuit, a knowledge of the effect of
  dead space on alveolar volume delivery is
  important especially in infants, children, small
  adults, and adults with ARDS treated with low
  tidal volumes

23
Assessment and Documentation of MV

• Alveolar Ventilation
• Anatomical Dead Space
• Normal anatomical dead space (VDanat) is about 1
  mL/lb IBW
• Note Bypassing the upper airway with an
  artificial airway reduces VDanat by about one half

24
Assessment and Documentation of MV

• Alveolar Ventilation
• Added Mechanical Deadspace (VDmech)
• Y-connectors, HMEs, and/or flex tubing all add
  mechanical deadspace
• To measure this volume, fill the device with
  water and empty into graduated container)
• When determining actual alveolar ventilation, the
  volume of these devices must be subtracted from
  the tidal volume
• Example VT VDanat VDmech Alveolar
  Ventilation

25
Assessment and Documentation of MV

• Alveolar Ventilation
• Final Alveolar Ventilation
• VA (VT VDanat VDmech) x f

.
26
Assessment and Documentation of MV

• Alveolar Ventilation - QUESTION
• A 36-year-old male patient with ARDS is
  ventilated with a VT of 400mL. The patients IBW
  is 176 lb (80 kg). The HME has a volume of 50
  mL. What is the approximate alveolar volume for
  one breath for this patient?
• 350 mL
• 260 mL
• 400 mL
• 190 mL

27
Assessment and Documentation of MV

• Alveolar Ventilation - ANSWER
• VDant is about 180 ml (80 kg IBW x 2.2 lb
  176). With an ET tube in place, the VDant is
  reduced to about half to 90 mL. The HME adds
  about 50 mL of mechanical dead space. VD is
  about 140 mL.
• VT VD VA
• 400 140 260 mL/breath
• VA 260 mL

28
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Ensures that very high pressure limits are not
  exceeded
• Provide information about the patients conditions

29
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Peak Inspiratory Pressure (PIP or PPeak)

30
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Peak Inspiratory Pressure (PIP or PPeak)
• The highest pressure observed during inspiration
• Used to calculate dynamic compliance (CD)
• A constant VT with an ? PIP may indicate a ? in
  lung compliance (CL) or an ? in Raw
• A declining PIP may indicate a leak or may a sign
  of improvement in CL or Raw

31
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Plateau Pressure (PPlateau)

32
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Plateau Pressure (PPlateau)
• Obtained by using the ventilators inspiratory
  pause of 0.5 1.5 seconds
• Static pressure is read when no gas flow is
  occurring
• Reflects the elastic recoil of the alveolar walls
  and thoracic cage against the volume of air in
  the lungs
• Cannot be measured accurately if the patient
  makes active respiratory efforts

33
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Set Pressure
• The operator sets a target pressure to be
  delivered to the patient during PC-CMV, PC-SIMV
  and PSV
• Example

22 cm H2O
15 cm H2O
34
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Peak Pressure Minus Plateau Pressure
• The difference between PIP and PPlateau is the
  transairway pressure (PTA) this is the amount of
  pressure required to overcome Raw (Raw
  PTA/Flow)

35
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Peak Pressure Minus Plateau Pressure
• A higher than expected difference between PIP and
  PPlateau usually indicates increased Raw
• Raw increases with secretions, mucosal edema,
  bronchospasm, kinked ET tube or patient biting on
  ET tube, partly occluded HME (moisture or
  secretions)

36
Assessment and Documentation of MV

• Monitoring Airway Pressures
• End-Expiratory Pressure (EEP)
• The lowest pressure measured in the expiratory
  phase

37
Assessment and Documentation of MV

• Monitoring Airway Pressures
• End-Expiratory Pressure (EEP)
• The lowest pressure measured in the expiratory
  phase
• PEEP Positive End Expiratory Pressure
• CPAP Continuous Positive End Expiratory
  Pressure
• Auto-PEEP

38
Assessment and Documentation of MV

• Monitoring Airway Pressures
• End-Expiratory Pressure (EEP)
• Auto-PEEP air trapping during positive pressure
  ventilation AKA
• Air trapping
• Breath stacking
• Inadvertent PEEP
• Dynamic hyperinflation
• Occult PEEP
• Intrinsic PEEP

39
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Causes of Auto-PEEP

• Increased Raw
• Airway collapse on expiration
• Bronchospasm
• COPD
• Mucosal edema
• Secretions
• Short TE

• Long TI
• Slow peak flow rate
• High rate
• High VE
• High IE ratio
• Increase Raw from ET Tube, expiratory valve, PEEP
  valve

40
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Auto-PEEP Suspected

• Accessory muscle use
• Decreased breath sounds
• Decreased chest wall movement
• Dyspnea
• Increased resonant percussion
• Increased radiolucency on CXR

• Inspiratory efforts do not trigger ventilator
• Patient still exhaling when vent delivers next
  breath
• Patients respiratory rate greater than
  ventilators response (assuming sensitivity is
  set correct)

41
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Auto-PEEP Suspected

42
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Measuring Auto-PEEP
• Exhalation valve is occluded for 1-2 seconds just
  prior to inspiration
• Expiratory Pause control on newer ventilators
• Level of auto-PEEP is reflected on the pressure
  gauge during the pause
• Reading is accurate only if the patient is not
  actively breathing
• Auto-PEEP Total PEEP set PEEP

43
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Methods to reduce Auto-PEEP

• Brochodilators / suction
• Steroids
• Allow more spontaneous breathing (SIMV, PS, CPAP)
• Larger ET Tube
• Apply PEEP (up to 80 of auto-PEEP)

• Increase TE
• Decrease respiratory rate (? TE )
• Decrease VT (? TI)
• Decrease TI
• Increase peak flow rate (? TI)

44
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Mean Airway Pressure
• Closely parallels the mean alveolar pressure
• Newer vents calculate and display mean airway
  pressure
• Affected by
• PIP
• EEP
• TI/Total cycle time
• f
• Inspiratory flow patterns and modes
• Important to tissue oxygenation!!!
• Affects lung volumes and cardiac output

45
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Pressure Limit
• Usually set 10 15 cm H2O above PIP
• Audible and visual alarms are activated if PIP
  exceeds a set limit
• Activation of high pressure limit alarm ends
  inspiration
• Often activated by coughing
• High peak pressures may indicate ? Raw or ? CL

46
Assessment and Documentation of MV

• Monitoring Airway Pressures
• Low Pressure Alarm
• Visual or audible alarm is activated when
  pressure within the vent circuit has fallen
  significantly
• Leak or disconnect
• Usually set 10 cm H2O below PIP
• Note If the leak is not obvious, the patient
  must be manually ventilated until the cause of
  the leak is determined

47
Assessment and Documentation of MV

• Vital Signs
• Observing and recording the patients blood
  pressure (BP), heart rate (HR), temperature (T),
  respiratory rate (f), oxygen saturation (SpO2),
  and color every few hours help staff members
  evaluate possible changes in the patients
  overall condition
• Moderate changes in vital signs should alert the
  practitioner to the possibility of hypoxemia,
  impending cardiovascular collapse, or infection

48
Assessment and Documentation of MV

• Vital Signs
• Heart Rate
• All patient on ventilatory support must be
  continuously monitored with a three-lead ECG
• Provides maximum/minimum HR alarms
• ECG electrode disconnection
• Vent disconnection -
• (hypoxemia, hypercapnia)
• Myocardium infarction (MI)
• Anxiety
• Pain
• Stress

49
Assessment and Documentation of MV

• Vital Signs
• Temperature
• Hyperthermia
• Infection
• Tissue necrosis
• Metabolic states, e.g., hyperthyroidism
• Atelectasis
• Accidental or surgical trauma

50
Assessment and Documentation of MV

• Vital Signs
• Temperature
• Hypothermia
• Metabolic disease
• CNS disorders
• Drugs
• Alcohol, heroin, carbon monoxide

51
Assessment and Documentation of MV

• Vital Signs
• Systemic Arterial Blood Pressure
• Monitored intermittently
• Stethoscope/sphygmomanometer
• Automatic BP cuff
• Monitored continuously
• Invasive intravascular arterial catheters
• A-Line

Radial A-Line
52
Assessment and Documentation of MV

• Vital Signs
• Central Venous Line (CVP)
• Placed in the superior vena cava or right atrium
• Provide valuable information regarding
• Right heart function
• Fluid status
• Hypervolemia
• Hypovolemia

53
Assessment and Documentation of MV

• Vital Signs
• Pulmonary Artery Pressure
• Monitored continuously
• Swan-Ganz catheter
• AKA Balloon-tip, flow-directed, pulmonary artery
  catheter (BTFDC)
• Used in patients with severe cardiopulmonary
  complications

54
Assessment and Documentation of MV

• Physical Examination of Chest
• Inspection
• Accessory muscles usage - ? WOB
• Paradoxical breathing - ? WOB
• Abdominal distention
• Gas, air swallowing, bleeding, ascites
• Impairs ventilation
• Palpation
• Percussion
• Auscultation

55
Assessment and Documentation of MV

• ET and Tracheostomy Tube Cuffs
• Cuff Pressure Measurement
• Checked once per shift
• Pressures not to exceed
• 27 34 cm H2O (20 25 mm Hg)
• Excessive pressures my cause tracheal damage if
  cuff pressures are greater than tracheal
  perfusion pressures

56
Assessment and Documentation of MV

• ET and Tracheostomy Tube Cuffs
• High Cuff Pressure
• Overinflation of tube cuff
• Necessary to maintain minimum occlusion
• Artificial airway may have moved up into the
  larynx of pharynx
• Check depth of tube or chest x-ray
• ET tube may be too small

57
Assessment and Documentation of MV

• ET and Tracheostomy Tube Cuffs
• No or Low Cuff Pressure
• Cuff not properly inflated
• Cuff leak
• Check inflate cuff and clamp pilot tube
• Resolution change cuff
• Pilot balloon leak
• Check inflate cuff and place stopcock in pilot
  balloon in off position
• Resolution clamp pilot tube
• Pilot tube leak
• Resolution syringe with blunt-tipped needle

58
Assessment and Documentation of MV

• Tube and Mouth Care
• Reposition ET tube every shift (Pilbeam) and
  retape if necessary
• Most facilities do this every 24 hours
• Prevents pressure injury to gums, mouth, lips
• Usually a two-man procedure
• Mouth care should be performed every shift
• Helps prevents ventilator-acquired pneumonia
  (VAP)

59

• JADA Continuing Education
• Pneumonia in nonambulatory patients
• The role of oral bacteria and oral hygiene
• Frank A. Scannapieco, DMD, PhD Background.
  Considerable evidence exists to support a
  relationship between poor oral health, the oral
  microflora and bacterial pneumonia, especially
  ventilator-associated pneumonia in
  institutionalized patients. Teeth or dentures
  have nonshedding surfaces on which oral biofilms
  (that is, dental plaque) form that are
  susceptible to colonization by respiratory
  pathogens. Subsequent aspiration of respiratory
  pathogens shed from oral biofilms into the lower
  airway increases the risk of developing a lung
  infection. In addition, patients may aspirate
  inflammatory products from inflamed periodontal
  tissues into the lower airway, contributing to
  lung insult.

60
Assessment and Documentation of MV

• Mouth Care Kit for MV Patients

61
Assessment and Documentation of MV

• Monitoring CL and Raw
• Static Compliance (Cs)
• Normal 70 100 mL/cm H2O (Cs VT/Pplat
  PEEP)
• Changes in Cs over time is usually considered a
  result of change in the patients alveolar
  elastic recoil (can be affected by chest wall
  compliance)
• Causes for ? Cs

• Air trapping
• PE
• Atelectasis
• Consolidation

• Pneumonia
• Pneumothorx
• Hemothorax
• Pleural effusion

62
Assessment and Documentation of MV

• Monitoring CL and Raw
• Static Compliance (Cs)
• Chest wall compliance reduced in the following
• Flail chest
• Chest wall muscle tension
• Pneumonmediastinum
• Abdominal distention

63
Assessment and Documentation of MV

• Monitoring CL and Raw
• Static Compliance (Cs)
• Pressure Ventilation (PV)
• Reduced CS
• Set pressure remains constant while delivered VT
  decreases
• Increased CS
• Set pressure remains constant while delivered VT
  increases

64
Assessment and Documentation of MV

• Monitoring CL and Raw
• Static Compliance (Cs)
• Volume Ventilation (VV)
• Reduction in CS
• Delivered VT remains constant while pressure
  increases
• Increases in CS
• Delivered VT remains constant while pressure
  decreases

65
Assessment and Documentation of MV

• Monitoring CL and Raw
• Dynamic Compliance (CD)
• Normal 40 70 mL/cm H2O (CD VT/PIP-PEEP)
• Includes compliance and resistance components
• Lung and chest wall elastic recoil
• Airway resistance
• Decreases when
• CS decreases
• Raw increases

66
Assessment and Documentation of MV

• Monitoring CL and Raw
• Differentiating between lung and airway
  resistance problems
• Volume Ventilation
• ? PIP and ? Pplat (constant PTA) ? CS
• ? PIP and Pplat constant (? PTA) ? Raw

67
Assessment and Documentation of MV

• Monitoring CL and Raw
• Airway Resistance (Raw)
• Normal Raw 0.6 2.4 cm H2O/L/sec
• Approximately 6 cm H2O/L/sec or higher in
  intubated patients
• Can be estimated by PTA/Flow (L/sec)
• Use constant flow (square wave) when measuring
  Raw
• Many new ventilators calculate Raw

68
Assessment and Documentation of MV

• Monitoring CL and Raw
• Airway Resistance (Raw)
• Increased Raw caused by
• Bronchospasm
• Secretions
• Mucosal edema
• Small ET tube
• Kinked or bitten ET tube
• Treat the cause!

69
Assessment and Documentation of MV

• Monitoring CL and Raw
• Airway Resistance (Raw)
• Graphs demonstrating ?Raw

VC Ventilation
PC Ventilation
70
Assessment and Documentation of MV

• Comment Section of Vent Flow Sheet

• Breath sounds
• Chest movement
• Percussion note
• Skin color
• Level of consciousness

• Changes in vent settings
• Changes in physicians order
• Description of any equipment problems

Some medical centers use SOAP notes