FANNP 27th National NNP Symposium: Clinical Update … Ventilation Strategies and...K depletion...

Baby’s Breath: Ventilation Strategies and Blood Gas Interpretation Karen Wright, PhD, NNP-BC DNP NNP Program Director Rush University, Chicago, IL

The speaker has signed a disclosure form and indicated she has no significant financial interest or relationship with the companies or the manufacturer(s) of any commercial product and/or service that will be discussed as part of this presentation.

Session Summary This presentation will provide a general overview of oxygenation and ventilation strategies commonly used in neonatal care, as well as a review of blood gas interpretation/manipulation to optimize the neonate’s status.

Session Objectives Upon completion of this presentation, the participant will be able to:

evaluate blood gas results;

recognize the effects of common neonatal therapies for oxygenation and acid-base manipulation;

apply the principles of ventilation.

Test Questions Participants will be asked questions throughout this presentation.

References Brodsky, D. & Martin, C. (2012). Neonatology review: Q & A (3rd ed.). Wolters-Kluwer.

Cummings, J. J., Polin, R. A. & Committee on Fetus and Newborn, American Academy of Pediatrics (2016). Noninvasive respiratory support. Pediatrics, 137.

Donn, S. M. & Sinha, S. K. (2006). Minimising ventilator induced lung injury in preterm infants. Archives of Disease in Childhood, Fetal Neonatal Edition, 91, F226.

Fisher, M. J. (2008). Mechanical ventilation made easy (2nd ed.). Michael J. Fisher publisher.

Goldsmith, J. & Karotkin, E. (2004). Assisted ventilation of the neonate (4th ed.). Philadelphia, PA: W. B Saunders.

Gomella, T. L. (2013). Neonatology: Management, procedures, on-call problems, diseases, and drugs (7th ed.). New York: McGraw-Hill.

Kenner, C. & Lott, J. W. (2009). Comprehensive neonatal care: An interdisciplinary approach (4th ed.). St. Louis, MO: Saunders Elsevier.

Salvo, V., Lista, G., Lupo, E., et al. (2015). Noninvasive ventilation strategies for early treatment of RDS in preterm infants: An RCT. Pediatrics, 135: 444.

B13 FANNP 27th National NNP Symposium: Clinical Update and Review

B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation of 17

• The continuum of respiratory management

• Ventilation strategies

Baby’s Breath: Ventilation Strategies and Blood Gas

Interpretation

Karen Wright PhD, NNP‐BC

Rush University Chicago, IL

[email protected]

Disclaimers 1. I have no financial interests to disclose

2. I hope that this presentation is helpful and that informs learning and study. But I have no idea what the NCC will specially ask you. That said, physiology is crucial to understanding diagnostics and management.

Objectives of This Lecture

Upon completion of this presentation, the participant will be able to:

1. Evaluate blood gas results

2. Recognize the effects of common neonatal therapies for oxygenation and acid‐base manipulation

3. Apply the principles of ventilation

3 Primary Topics Part 1 Transition and Resuscitation

Part 2 Blood gas interpretation

Part 3 Ventilation

Module Contents

• Assessment, diagnosis and clinical presentation of respiratory distress

• Clearance of fetal lung fluid and transition from fetal to neonatal breathing

• Umbilical cord blood gas analysis

• Clinical Interpretation of ABGs

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FANNP 27th National NNP Symposium: Clinical Update and Review


Birth Transition

• Physiology of respiratory changes at birth

• The benefits of labor

• Water channels of the fetal lung

Physiologic Changes at Birth

Umbilical Vessels‐ Immediately after clamping

• constrict in response to stretching and increased O2 content at delivery

• Low resistance placental vascular bed removed from circulation

• Increased SVR • Reduction of blood flow along the ductus venosus (passive closure 3‐7days)

Lung expansion:

Drops pulmonary vascular resistance

Increase in blood returning to the LA

Clearance of Fetal Lung Fluid

• Physiologic considerations

• Delayed clearance of fetal lung fluid

• Enhanced clearance

Presentation of Respiratory Distress • Chest retractions

• Nasal Flaring

• Grunting

• Nasal Flaring

• Accessory Respiratory Muscles

• Apnea

• Gasping

Apgar Scoring and Delivery Room Assessment

• Measuring heart rate in the 21st century

• Treating primary and secondary apnea

• Suctioning in the delivery room



artery, or posterior tibial arteries

• May be pre or post ductal

• Consider the site/source of the blood gas, oxygen level, and pulse oximetry

Of the following, which anion/cation is actively transported across the pulmonary epithelial cells to induce fetal lung fluid absorption prior to delivery?

A. Bicarbonate

B. Chloride C.

Hydrogen D.

Potassium E.

Sodium

Blood gases

• Measure oxygenation and ventilation

• Invasive or noninvasive

• Arterial, venous, or capillary

• Umbilical cord or from the neonate

• Pre or post‐ductal

• May be used for further calculations

Umbilical Cord (Fetal) Gases

Arterial Blood Gases

• Most accepted measure of respiratory status

• Invasive – either indwelling or accessed

• Umbilical artery, either radial



Venous Blood Gases

• Analysis is the same

• Interpreted differently

• pH slightly lower

• pCO2 slightly higher

• pO2 is of no use

The tip of the UAC lies in the and the UVC in the .

A. Ductus arteriosis and ductus venosus

B. Right atrium and right ventricle

C. Aorta and inferior vena cava

Capillary Blood Gases

• Blood is arterialized by warming the heel

• pH is slightly lower than arterial

• pCo2 is slightly higher

• pO2 no value

Ensure No Air Bubbles. Syringe must be sealed immediately after withdrawing sample.

• Contact with AIR BUBBLES Air bubble = PO2 150 mm Hg , PCO2 0 mm Hg Air Bubble + Blood = PO2 PCO2

ABG Syringe must be transported at the earliest to the

laboratory for EARLY analysis via COLD CHAIN



< 28 weeks’

GA

28-40 weeks’

GA

Term with PPHN

Infant with BPD

pH ≥ 7.25 ≥ 7.25 7.30-7.50

7.35-7.45

PaCO2 45-55 45-55

30-40

55-65

PaO 45-65 50-70

80-120

50-80 2

STEP 0 • Is this ABG Authentic?

STEP 1 • ACIDEMIA or ALKALEMIA? STEP 2

• RESPIRATORY or METABOLIC? STEP 3 • If

Respiratory – ACUTE or CHRONIC? STEP 4 • Is

COMPENSATION adequate?

STEP 5 • If METABOLIC – ANION GAP?

STEP 6 • If High gap Metabolic Acidosis–

ABG – Procedure and Precautions Site- (Ideally) Radial Artery

Brachial Artery

Femoral Artery

Ideally - Pre-heparinized ABG syringes

- Syringe should be FLUSHED with 0.5ml of 1:1000 Heparin solution and emptied.

DO NOT LEAVE EXCESSIVE HEPARIN IN THE SYRINGE

HEPARIN DILUTIONAL HCO3

EFFECT PCO2

Only small 0.5ml Heparin for flushing and discard it Syringes must have > 50% blood. Use only 2ml or

less syringe.

Components of the BG

Measured Values:

pH PaCO2

PaO2

Calculated Values

HCO2

O2 Sat

BE

Acidic Blood

Target Blood Gas in Neonates

Blood Gas

Oxygenation Ventilation Acid-Base

PaO2

SaO2

PCO2

pH HCO3-BE

* Goldsmith and Karotkin, Assisted Ventilation of the Neonate, 4th edition, Saunders



3 Types of Acid‐Base Disorders

• Primary acid‐base disorders

• Compensation

• Mixed acid‐base disorders

Indications for a Blood Gas • Assessment of ventilation and oxygenation status in patients with respiratory disease

• Assessment of acid‐base imbalance in sepsis, metabolic, and renal diseases

Determining Acid‐Base Balance Differential Diagnosis for Metabolic Acidosis

Condition Primary Disturbance Compensation

Metabolic Alkalosis Increased HCO3 Increased PaCO2

Respiratory Alkalosis Decreased PaCO2 Decreased HCO3

• Common causes

• Sepsis • NEC • Hypothermia or cold stress • Asphyxia • GI losses • IEM

• IVH

• PDA

• Shock

• Iatrogenic

• Medications

• Renal Failure

Differential Diagnosis for Metabolic Alkalosis Differential Diagnosis for Respiratory Acidosis

• Common

Excess alkali administration

K depletion

Prolonged NG sx or vomiting

Diuretic therapy

• Less common

Pyloric Stenosis

• Usually caused by insufficient alveolar ventilation secondary to lung disease

• Examples – Asphyxia, apnea, upper airway obstruction, RDS, PIE, pneumothorax



• Airway: e.g. laryngeal edema, severe micrognathia

• Lungs: e.g. RDS, pneumonia

• CNS: respiratory depression due to medications, CNS infection, hemorrhage, etc.

• Iatrogenic: for ventilated babies • Hyperventilation: e.g. urea cycle disorders

Differential Diagnosis for Respiratory Alkalosis

• Hyperventilation of the alveolus leading to carbonic acid deficiency – iatrogenic

• Air bubble in the syringe

• Diseases: CNS, response to hypoxia, maternal heroin addiction

Mixed Metabolic/Respiratory Acidosis Severe respiratory disease with hypercapnia with hypoxia – lactic acid build‐up and metabolic disease

Hypoxia

• ↓ PaO2

• ↓ O2 Saturation

• Causes: • Respiratory: RDS, Pneumonia

• Cardiac: Cyanotic CHD, CHF • Abnormal Hemoglobins

Primary Acid Base Disorders • One of the four acid‐base disturbances that is manifested by an initial

change in HCO3‐ or PaCO2

• Types:

• Respiratory acidosis

• Respiratory alkalosis

• Metabolic acidosis

• Metabolic alkalosis

Respiratory Acidosis

• A primary disorder where the first change is an elevation of PaCO2 resulting in decreased pH.

• Causes:

Respiratory Alkalosis • A primary disorder where the first change is a lowering of PaCO2, resulting in an elevated pH

• Rare in neonates

• Causes:



3

Metabolic Acidosis

• A primary acid‐base disorder where the first change is a lowering of HCO ‐, resulting in decreased pH

• Causes: • Dehydration • Shock • Sepsis • Metabolic disorders

Metabolic Alkalosis • A primary acid‐base disorder where the first change is an elevation of HCO3‐, resulting in increased pH.

• Causes: • Iatrogenic: loop diuretics • Rare diseases: cystic fibrosis, congenital chloride diarrhea

Compensation

• The body tries to overcome either a respiratory or metabolic dysfunction in an attempt to return the pH into the normal range.

• For respiratory disorders (i.e. resp. acidosis or alkalosis) the body develops metabolic compensation through the kidney (i.e. HCO3)

• For metabolic disorders (i.e. metabolic acidosis or alkalosis) the body develops respiratory compensation through the lungs (i.e. CO2)

Mixed Acid‐Base Disorders • Combination of two primary acid‐base disorder with different range of compensation.

• Usually happen in patients with chronic diseases or multiple primary pathologies

Source of ABG error Steps to ABG Interpretation

Step One:

Assess the pH to determine if the blood is within normal range, alkalotic or acidotic. If it is above 7.45, the blood is alkalotic. If it is below 7.35, the blood is acidotic.



120 ml/kg/d and furosemide was given 1.2 mg q12 hrs.

• ABG: pH=7.47, PCO2=40, PO2=60, HCO3=30, SaO2=92%

Steps to ABG Interpretation

Step Two:

If the blood is alkalotic or acidotic, we now need to determine if it is caused primarily by a respiratory or metabolic problem. To do this, assess the PaCO2 level. Remember that with a respiratory problem, as the pH decreases below 7.35, the PaCO2 should rise. If the pH rises above 7.45, the PaCO2 should fall. Compare the pH and the PaCO2 values. If pH and PaCO2 are indeed moving in opposite directions, then the problem is primarily respiratory in nature.

Steps to ABG Interpretation Step Three

Assess the HCO3 value. Recall that with a metabolic problem, normally as the pH increases, the HCO3 should also increase. Likewise, as the pH decreases, so should the HCO3. Compare the two values. If they are moving in the same direction, then the problem is primarily metabolic in nature.

Example 1 Baby boy, 28 wks GA, admitted 3 hrs ago, intubated initially, given surfactant, then extubated immediately to nasal CPAP, pressure 5 cm H2O, FiO2 0.5.

• ABG now: pH=7.20, PCO2=68, PO2=40,

Example 2 Baby girl, born at term by emergency CS, because of cord prolapse and severe fetal distress. She was flat, needed thorough resuscitation (intubation, UVC, 2 doses of epinephrine)

• Now she is 6 hrs old, ventilated, FiO 0.3, HCO3=22, SaO2=85%

• Interpret above blood gas

2

and had focal seizure.



Example 3

• Hundred day‐old baby girl, was born at 27 wks GA, had stormy course.

• Now she is on NC 1 LPM, FiO2 0.3



Example 4 • Seven day‐old, baby boy, born at 29 wks GA.

• He had large PDA, led to pulmonary hemorrhage, which treated conservatively.

• Indomethacin cannot begiven because of Lt side grade 4 IVH, TFI was restricted to



Example 6

If the pH is 7.23, the PaCO2 is 50, and the HCO3 is 24, what is the likely diagnosis?

RESPIRATORY ACIDOSIS

Example 7 If the pH is 7.49, the PaCO2 is 25, and the HCO3 is 22 what is the likely diagnosis?

RESPIRATORY ALKALOSIS

Example 8

If the pH is 7.56, the PaCO2 is 39, and the HCO3 is 38, what is the likely diagnosis?

METABOLIC ALKALOSIS

Example 9 If the pH is 7.35, the PaCO2 is 25, and the HCO3 is 9, what is the likely diagnosis?

COMPENSATED METABOLIC ACIDOSIS

Continuous Positive Airway Pressure

• Gregory et al in 1971. applied CPAP in RDS – used ETT CPAP initally

• Applied nasally, since most newborns are obligate nasal breathers.

• At the same time, the mouth acts as a pressure relief valve if the applied pressure is too high.

Example 10 If the pH is 7.30, the PaCO2 is 25, and the HCO3 is 9, what is the likely diagnosis?

Partially Compensated Metabolic Acidosis



Oxygen use and Pulse oximetry

• The evolution of pulse oximetry

• How does pulse oximetry work?

• Oxygen targeting

• Newborn Resuscitation Algorithm

• ROP

Oxygen Terms Oxygen Content ‐ sum of the quantity of oxygen bound to hemoglobin plus the amount of free oxygen dissolved in the blood

Oxygen Delivery ‐ amount of oxygen transported from the lungs to the microcirculation‐ depends upon the cardiac output and blood O2

Oxygen consumption — part of cardiac output; cannot be calculated

Oxygen administration

• Low‐flow cannula – difficult to calculate concentration (very low); limited ability to humidify

• High‐flow cannula‐heated and humidified; similar to CPAP; do not require a prong seal; probably washes out CO2

‐heated and humidified

‐ may be a reasonable alternative to CPAP

Assisted Ventilation

Non‐invasive Assisted Ventilation – 2 types

1. CPAP (single‐level pressure support) and High Flow Nasal Cannula

Non‐invasive Assisted Ventilation – 2 types 2. Bi‐level positive airway pressure (NIPPV)



Nasal Septal Erosion or Necrosis

• This is preventable when using appropriate sized prongs that are

correctly positioned.

Pneumothorax • Usually occurs in acute phase. • It is uncommon (<5%). • It usually results from the underlying disease process rather than

positive pressure alone.

• It is not a contraindication to the use of CPAP.

Abdominal Distension from Swallowing Air

• This is benign • Easily reduced with gastric drainage or aspiration

Nasal obstruction

• From improper prong placement or inadequate airway care

Physiology and Advantages of CPAP

• Prevents alveolar collapse by maintaining alveolar inflation

• Regular pattern of breathing in preterm infants.

• Reduces thoracic distortion from over‐ventilation

• Stabilizes the chest wall, splinting the airway

• Splints the diaphragm, decreasing obstructive apnea, and enhancing

surfactant release

• Minimizes complications from mechanical ventilation

• Can be bubble or ventilator derived

Indications for CPAP Delivery room resuscitation

Management of RDS

Postextubation support

Apnea

Mild upper airway obstruction

Complications of CPAP Which of the following is most accurate about the effects of CPAP?

A. Increases total airway resistance

B. Increases lung compliance

C. Increases functional residual capacity

D. Limits gas exchange

Introduction

Part 3 Modes of Neonatal Ventilation • Introduced in the 1960s

• Contributed to increased infant survival

• Also causes chronic lung injury and BPD

• Important to strategize neonatal ventilation to minimize lung damage



mandatory or triggered by the patient

• Inspiratory/Expiratory Times

• PEEP Goal of new ventilator design – to decrease lung injury

Ideal Mode of Ventilation

• Delivers a breath that:

‐synchronizes with the patient’s breath

‐ allows spontaneous respiratory effort

• Maintains adequate and consistent tidal volume and minute ventilation at low airway pressures

• Responds to rapid changes in pulmonary mechanics or patient demand

• Provides the lowest possible WOB

Advantages of Mechanical Ventilation 1. Improves gas exchange, primarily by lung recruitment to

improve ventilation/perfusion (V/Q) matching

2. Decreases work of breathing – saves energy

3. Provide adequate minute ventilation (carbon dioxide removal) infants with respiratory depression or apnea

**Focus now is to prevent BPD

Indications for Ventilation

• Respiratory acidosis ‐ arterial pH <7.2 and PaCO2 >60 to 65 mmHg.

• Hypoxia ‐arterial PaO2 <50 mmHg despite oxygen supplementation or FiO2 exceeds 40 percent on nasal

• Severe apnea • Respiratory distress syndrome (RDS)

• Apnea due to prematurity or perinatal depression

• Infection – Sepsis and/or pneumonia • Postoperative recovery • Persistent pulmonary hypertension

• Meconium aspiration syndrome • Congenital pulmonary and cardiac anomalies, such as congenital diaphragmatic hernia

2 Types of Ventilation Conventional mechanical ventilation (CMV) involves intermittent exchange of gas, which are similar in volume to physiologic tidal volume

‐ CMV, the minute ventilation is the product of frequency of breaths and tidal volume.

‐ Ventilator or patient triggered

‐TV is pressure or volume controlled or pressure controlled

High‐frequency ventilation (HFV) delivery of small volumes of respiratory gas at a rapid rate (300 to 1500 breaths per minute)

‐Minute ventilation is the product of frequency of breaths and the square of the tidal volume.

Conventional Ventilation

• Most common type of neonatal ventilation is time‐cycled pressure‐ limited – baby can breathe at any time

• Pressure from gas is regulated in 2 ways:

• Time‐cycled

• Pressure‐cycled

Settings • FIO2 • Regulation of gas flow

pressure‐limited‐ tidal volume delivered will fluctuate depending on the lung compliance of the patient.

volume‐controlled ‐ pressure needed to deliver a targeted tidal volume will vary depending on lung compliance

• Initiation of Breaths



SIMV

• Thought to improve patient comfort, not much change in outcome

• Provides mechanical synchronized breaths synchronized with spontaneous breaths

• Rate is set lower than spontaneous rate – allows additional breaths by baby

• PEEP with every breath

Assist Control • Ventilator delivers a breath each time the patient's inspiratory effort exceeds the preset

• IT and PIP or TV are set

• Minimum ventilator rate set in case spontaneous rate

PSV – Pressure Support Ventilation

• Patient determines the rate/ I:E ratio

• PIP is a ventilator setting • Inspiratory flow rate is flow limited

• PSV + SIMV = ↓ WOB

NAVA • Neutrally‐adjusted ventilator assist (NAVA)

• uses electrical activity from the diaphragm recorded by a specialized nasogastric tube in the lower esophagus

• Synchronizes mechanical ventilator breaths

• ↓s PIP

• NAVA can be noninvasive nasal intermittent positive pressure ventilation (NIPPV) without endotracheal intubation and appears

High-Frequency Ventilation

HFV is a radical departure from standard, conventional mechanical ventilation.

There are several types of HFV devices, including (HFJV), HFOV, and hybrids.

The rationale for HFV is that the provision of tiny gas volumes at rapid rates results in much lower alveolar pressure



High‐Frequency Ventilation

• MAP provides a constant distending pressure equivalent to CPAP.

• This inflates the lung to a constant and optimal lung volume maximizing the area for gas exchange and preventing alveolar collapse in the expiratory phase.

Indications for high frequency ventilation include

1.Rescue following failure of conventional ventilation (PPHS, MAS)

2. Air leak syndromes (pneumothorax, pulmonary interstitial emphysema)

3.To reduce barotrauma when conventional ventilator settings are high

Terminology

Frequency

High frequency ventilation rate (Hz, cycles per second)

MAP

Mean airway pressure (cmH2O)

Amplitude

delta P or power is the variation around the MAP

Oxygenation is dependent on MAP and FiO2

High Frequency Ventilation • Ventilation is dependent on amplitude and to lesser degree frequency.

• Thus when using HFV CO2 elimination and oxygenation are independent.

Adjusting HFV Settings

Poor

Oxygenation Over

OxygenationUnder

Ventilation Over

Ventilation

Increase FiO2 Decrease FiO2 Increase

Amplitude Decrease Amplitude

Increase MAP (1-2cmH2O)

Decrease MAP (1-2cmH2O)

Decrease Frequency (1-2Hz)

if Amplitude Maximal

Increase Frequency (1-2Hz)

if Amplitude Minimal



HFOV vs HFJV

• HFOV ‐ small tidal volumes by oscillating air movements at frequencies of 600 to 900 breaths per minute (10 to 15 Hz)

• HFJV ‐ time‐cycled, pressure‐limited, constant gas flow interrupters that are used in parallel with a conventional ventilator, with PEEP and rate (sigh breaths); usually 420 breaths per minute

Which ventilator settings are determinants of oxygenation?

A. Positive end expiratory pressure (PEEP)

B. Peek inspiratory pressure (PIP)

C. Inspiratory time

D. Frequency

E. Gas flow rate

F. All of the above An infant is born at 32 weeks gestational age. At 5 hours of life the baby has worsening tachypnea, nasal flaring, grunting, and central cyanosis. The X‐ray is below.

The infant describe most likely has: A. Aspiration

B. Congenital heart disease

C. Meconium Aspiration Syndrome

D. Respiratory Distress Syndrome

E. Transient Tachypnea of the Newborn



FANNP 27th National NNP Symposium: Clinical Update … Ventilation Strategies and...K depletion...

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