B13. Baby s Breath: Ventilation Strategies and Blood Gas Interpretation. Session Summary. Session Objectives. Test Questions.

Transcription

1 B13 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 (3 rd 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: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 1 of 17

2 Baby s Breath: Ventilation Strategies and Blood Gas Interpretation 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. Karen Wright PhD, NNP BC Rush University Chicago, IL Karen_Wright@rush.edu 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 Consider becoming an NRP Instructor 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 The continuum of respiratory management Ventilation strategies B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 2 of 17

3 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 21 st century Treating primary and secondary apnea Suctioning in the delivery room B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 3 of 17

4 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 Umbilical Cord (Fetal) 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 Arterial Blood Gases Most accepted measure of respiratory status Invasive either indwelling or accessed Umbilical artery, either radial artery, or posterior tibial arteries May be pre or post ductal Consider the site/source of the blood gas, oxygen level, and pulse oximetry B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 4 of 17

5 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 UVC in the. and 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 = PO mm Hg, PCO 2 0 mm Hg Air Bubble + Blood = PO 2 PCO 2 ABG Syringe must be transported at the earliest to the laboratory for EARLY analysis via COLD CHAIN B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 5 of 17

6 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 HCO 3 EFFECT PCO 2 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 Acidic Blood Measured Values: ph PaCO2 PaO2 Calculated Values HCO2 O2 Sat BE Target Blood Gas in Neonates Blood Gas < 28 weeks GA weeks GA Term with PPHN Infant with BPD Oxygenation Ventilation Acid-Base ph PaCO PaO 2 SaO 2 PCO 2 ph HCO 3 -BE PaO * Goldsmith and Karotkin, Assisted Ventilation of the Neonate, 4 th edition, Saunders B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 6 of 17

7 3 Types of Acid Base Disorders Primary acid base disorders Compensation 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 Mixed acid base disorders 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 B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 7 of 17

8 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 PaO 2 O 2 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 PaCO 2 resulting in decreased ph. Causes: Airway: e.g. laryngeal edema, severe micrognathia Lungs: e.g. RDS, pneumonia CNS: respiratory depression due to medications, CNS infection, hemorrhage, etc. Respiratory Alkalosis A primary disorder where the first change is a lowering of PaCO2, resulting in an elevated ph Rare in neonates Causes: Iatrogenic: for ventilated babies Hyperventilation: e.g. urea cycle disorders B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 8 of 17

9 Metabolic Acidosis A primary acid base disorder where the first change is a lowering of HCO, resulting in decreased ph 3 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. HCO 3 ) For metabolic disorders (i.e. metabolic acidosis or alkalosis) the body develops respiratory compensation through the lungs (i.e. CO 2 ) 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. B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 9 of 17

10 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 PaCO 2 level. Remember that with a respiratory problem, as the ph decreases below 7.35, the PaCO 2 should rise. If the ph rises above 7.45, the PaCO 2 should fall. Compare the ph and the PaCO 2 values. If ph and PaCO 2 are indeed moving in opposite directions, then the problem is primarily respiratory in nature. Steps to ABG Interpretation Step Three Assess the HCO 3 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 HCO 3. 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 H 2 O, FiO ABG now: ph=7.20, PCO 2 =68, PO 2 =40, HCO 3 =22, SaO 2 =85% Interpret above blood gas 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 20.3, and had focal seizure. ABG: ph=7.15, PCO 2 =30, PO 2 =60, HCO 3 =6, SaO 2 =92% Interpret above blood gas 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 ABG: ph=7.34, PCO 2 =65, PO 2 =60, HCO 3 =33, SaO 2 =92% Interpret above blood gas 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 120 ml/kg/d and furosemide was given 1.2 mg q12 hrs. ABG: ph=7.47, PCO 2 =40, PO 2 =60, HCO 3 =30, SaO 2 =92% B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 10 of 17

11 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 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 B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 11 of 17

12 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) B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 12 of 17

13 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 Nasal Septal Erosion or Necrosis Pneumothorax Abdominal Distension from Swallowing Air This is preventable when using appropriate sized prongs that are correctly positioned. 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. This is benign Easily reduced with gastric drainage or aspiration Nasal obstruction From improper prong placement or inadequate airway care 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 B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 13 of 17

14 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 PaCO 2 >60 to 65 mmhg. Hypoxia arterial PaO 2 <50 mmhg despite oxygen supplementation or FiO 2 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 pressurelimited baby can breathe at any time Pressure from gas is regulated in 2 ways: Time cycled Pressure cycled Goal of new ventilator design to decrease lung injury 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 mandatory or triggered by the patient Inspiratory/Expiratory Times PEEP B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 14 of 17

15 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 B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 15 of 17

16 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 (cmh 2 O) Amplitude delta P or power is the variation around the MAP Oxygenation is dependent on MAP and FiO 2 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 Oxygenation Under Ventilation Increase FiO 2 Decrease FiO 2 Increase Amplitude Increase MAP (1-2cmH 2 O) Decrease MAP (1-2cmH 2 O) Decrease Frequency (1-2Hz) if Amplitude Maximal Over Ventilation Decrease Amplitude Increase Frequency (1-2Hz) if Amplitude Minimal B13: Baby's Breath: Ventilation Strategies and Blod Gas Interpretation Page 16 of 17

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