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