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Kuehne 2011
UNDERSTANDING NEONATAL WAVEFORM GRAPHICS
Brandon Kuehne, MBA, RRT-NPS, RPFT Director- Neonatal Respiratory Services
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Disclosures
Purpose: To enhance bedside staff’s knowledge of ventilation and oxygenation support to the neonate. To support and encourage the use of the proximal flow probe via the explanation of theory of operation. To encourage the practical application of waveform analysis associated with neonatal pressure ventilation.
Objectives: Identify and discuss the various clinical types of graphic waveforms provided at bedside to the neonatal
caregiver. Describe the common types neonatal ventilatory complications that can be diagnosed and corrected with the
proper application of graphic waveform identification and analysis.
The Planning Committee and Faculty of this activity have no disclosed conflicts of interest related to this content.
Completion Criteria: In order to receive Continuing Nursing Education (CNE) credit, you must attend 80% of the program.
No commercial support was received for this program Nationwide Children’s Hospital’s accreditation as a provider refers to recognition of educational activities
only and does not imply ANCC Commission on Accreditation, Ohio Board of Nursing, ONA or Children’s Hospital’s approval or endorsement of any product.
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What is Respiration?
Ventilation The removal of CO2
Oxygenation The uptake of 02
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How do I achieve these items, Mechanically? Ventilation component is comprised of two parts
Tidal Volumes RateTogether they make:
Vt X RR = minute volume
In Neonate approx. 200ml/kg/min• Oxygenation component consists of a
combination of: Fractional inspired Oxygen (Fi02) Alveolar pressure (Mean Airway Pressure)
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Oxygenation
FiO2 21% - 100%
Alveolar Pressure (MAP) Distending the alveoli allows oxygen exchange to
take place over greater period of time. The biggest components that affect the MAP are
PEEP CPAP
PIP and Rate and Insp. Time affect MAP to a much lesser extent
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Ventilation
Tidal Volume- Effective Vt =
Exhaled Vt – ((PIP – PEEP) x Tubing compliance) wt.(kg)
Most ventilators can display this number in real time if the proper patient weight is inputted
(targets are usually 4-6ml/kg for newborns)
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Ventilation
Respiratory Rate Frequency that alveoli expand and contract
Good starting numbers Newborn – 3 months 30 - 40bpm 3 months to 2 years 20bpm 2 years – adult 12bpm
EXCEPTION … disease process involving air trapping
Proximal Airway Flow Monitoring
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What is measured and where? Pressure- is measured back
at machine Time – is measured back at
machine Flow is measured at patient
(only with flow probe in place) Volumes (Vti and Vte) are
derived from flows read at patient wye via flow sensor
(deriving volumes from flow signals is a process called integration)
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Proximal Airway Monitoring
Hotwire flow sensor is required in order to run ventilator properly in Neonatal Mode
Provides accurate two-way flow monitoring at patient’s airway
Critical for volume measurements on VLBW neonates
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+ -
Heated Anemometers (flow sensor) How Do They Work?
Heated element (gold wire) Measures the current necessary to
maintain the temperature constant (cooling effect of gas flow)
Lack of moving parts Fast and sensitive response
(Electrical signal –response slightly under speed of light)
Virtually no resistance Very Accurate
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Flow Sensor Issues
Humidity Water will create significant fluctuations of
accuracy. Secretions- surfactant
Reading above or below baseline in the presence of zero flow
Very delicate-breaks easily Wears-out due to processing and age
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Calibration of Heated Wire Flow Sensor
Occasionally RTs will need to disconnect flow sensor from the patient and perform zero flow calibration maneuver in order to reset flow reading to baseline.
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Scalar Identification and Analysis
Pressure
Flow
Volume
0+
_
Insp. Exp.
PIP
Exp.
PEEP
Insp.
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Waveform Identification and Analysis
Pressure
Flow
0+
_
Insp. Exp.
PIP
Exp.
PEEP
Insp.Red indicates machine initiated breath
Flow Baseline
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SIMV with Spontaneous Pressure Supported Breaths
Yellow indicates patient triggered breath
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Paw
Paw
Synchronized Intermittent Ventilation (SIMV)
SIMV: Mandatory (patient or machine init Spontaneous breaths
Are there any spontaneous breaths here?
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Paw CPAP
Paw PS
Pressure Support Ventilation
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Increased Expiratory Resistance
Prolonged expiratory flow indicates an obstruction to exhalation and may be caused by obstruction of a large airway, bronchospasm, or secretions
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Increased Expiratory Resistance
Normal Resistance
Increased Resistance
Possible Intrathoracic Obstruction- i.e. bronchospasm or secretions
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Variable Airway Obstruction-Secretions or water in tubing (extra-thoracic)
Jagged flow signal on inspiration
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Airway Obstruction- Flow-Volume Loop before and after removing
water from tubing
BE
BEFORE SXN AFTER SXN
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Insufficient Expiratory Time
Expiratory flow is unable to return to baseline prior to the initiation of the next mechanical breath
Incomplete exhalation causes gas trapping, dynamic hyper-expansion and the development of intrinsic PEEP (aka “Auto-PEEP” or “Breath-stacking”)
Can be fixed by decreasing I-time
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Gas Trapping with Inappropriate Inspiratory Time-Insufficient Exp.Time
Inspiratory Time 0.5 s
Inspiratory Time 0.3 sInspiration beginning before flow returns to baseline
Plenty of time to exhale at this I-Time
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Air leaks
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Air leak- Related to ET tubes or circuit
Volume
Pressure
Flow
Volume
Time
Volume never returns to baseline
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Air leak- Related to ET tubes or Circuit
Volume Flow
Volume
Time
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“Sawtooth" Pattern
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Baseline Flow
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Patient Lockout
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Trigger Sensitivity-Inappropriate Flow Trigger
e
Sensitivity level
Time
Flow
TimeLook at all this unsupported patient effort
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Trigger Sensitivity- Appropriate Flow Trigger
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Auto Cycling
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Autocycling- Secondary to Leak
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Resolved Autocycle- Flow Trigger Increased
Trigger ↑’d to 0.7 L/M -auto cycle ended
A short expiratory hold maneuver revealed no patient effort
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Flow Starvation
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Insufficient PSV
Figure “8”
Just a little more pressure (indirectly increasing flow) and flow starvation goes away
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Pressure Volume Loops to Assess RDS
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Graphical Analysis of RDS
Pre Surfactant
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Pressure- Volume Graphical Analysis of RDS
Six Hours Post Surfactant
Nice football shape @ 45° angle
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