Oxygen Administration-updated (2).pdf

Oxygen Administration Hassan Althabet, MSCRC. Ghadeer Alowaywi , MSCRC.  Outlines: Discuss causes, clinical signs and symptoms, and evidence of hypoxemia. Identify adverse physiologic effects and equipment-related complications associated w...

Oxygen Administration Hassan Althabet, MSCRC. Ghadeer Alowaywi , MSCRC.  Outlines: Discuss causes, clinical signs and symptoms, and evidence of hypoxemia. Identify adverse physiologic effects and equipment-related complications associated with oxygen administration to neonates, infants, and children. Differentiate between variable-performance and fixed performance oxygen delivery systems and provide examples of each. Discuss the indications and contraindications for use of oxygen delivery devices in neonatal and pediatric populations. Describe the methods used to apply devices to deliver oxygen to neonates, infants, and children.  Introduction : The goal of oxygen administration is to achieve adequate tissue oxygenation. The system used to provide supplemental oxygen must be appropriate to the patient’s size, gestational and postnatal age, and clinical condition. Selection of the oxygen delivery device and flow rate is targeted to meet the specific physiologic needs and therapeutic goals of each patient.  Introduction : Unfortunately, adverse reactions from the therapeutic use of oxygen are well documented in neonatal and pediatric patients. Therefore, it is imperative that oxygen therapy be provided at accurate and safe levels with the lowest possible fractional concentration of inspired oxygen (Fio2).  Indications: Documented or suspected hypoxemia: The most common indication for oxygen therapy is the need to correct hypoxemia. Left untreated, hypoxemia progresses to hypoxia and possibly anoxia , which, if severe enough, leads to anaerobic metabolism and development of lactic acidosis.  The Most Common Causes of Hypoxemia : Decreased alveolar ventilation Decreased inspired oxygen Poor ventilation– perfusion relationships Intrapulmonary or cardiac shunting Diffusion defects Short red blood cell transit times.  Other Causes of Oxygenation Issues: In conditions such as anemia or carbon monoxide poisoning, the oxygen-carrying capacity of the blood is reduced despite the presence of normal arterial oxygen tension (Pao2). Bradycardia, cardiac failure, hypotension, and hypothermia leave the circulatory system unable to provide adequate tissue oxygen. In rare cases, such as cyanide poisoning, the tissue is unable to accept and use oxygen, despite adequate oxygen delivery.  Factors that Affect Oxygen Delivery : Oxygen delivery is determined by : Concentration of hemoglobin in the blood ( Hgb) Arterial oxygen saturation (Sao2) Rate of blood circulation (CO) Efficiency with which oxygen is unloaded from the hemoglobin to the tissues.  Oxygen therapy is administered if hypoxemia is documented through arterial blood gas sampling or pulse oximetry ,or if hypoxia is strongly suspected on clinical grounds. However, in emergency situations, such as severe respiratory distress, shock, or cardiopulmonary arrest, oxygen therapy is never withheld even if laboratory test results are unavailable.  Evidence of Hypoxemia Measurement of Oxygen Tension and Saturation: o The Pao2 and the Spo2 are the principal clinical indicators used to begin, monitor, adjust, and terminate oxygen administration. o Oxygen therapy is initiated when : In children : Pao2 less than 80 mm Hg and an Spo2 less than 95% usually indicate hypoxemia. In neonate :Pao2 less than 50 mm Hg and an Spo2 less than 88%.  Fetal hemoglobin has a much greater affinity for oxygen, the oxygen dissociation curve is shifted to the left, allowing a higher saturation for any given Pao2. The normal immediate postnatal Pao2 of 50 to 60 mm Hg corresponds closely with an Spo2 of 85% to 90%.  Clinical Signs and Symptoms The earliest clinical manifestations of hypoxia are typically tachycardia and tachypnea. Worsening hypoxia results in decreased ventilation, apnea, and bradycardia.  Clinical Signs and Symptoms Other physical signs of hypoxia include grunting, nasal flaring, retractions, paradoxical breathing, cyanosis, irritability, and increased restlessness. If prolonged, the neonate or child can experience a decreased level of consciousness and become lethargic and flaccid.  Clinical Signs and Symptoms : Cyanosis Peripheral cyanosis occurs when a decrease in body temperature results in poor peripheral circulation or vasoconstriction. Central cyanosis involves the warm and well-perfused areas of the tongue and mucous membranes. It does not occur until reduced hemoglobin reaches 4 to 6 g/dL in arterial blood.  Clinical Signs and Symptoms : Cyanosis In adult and children, the presence of cyanosis has often been used to determine inadequate oxygenation before pulse oximetry. In adult and children, cyanosis occurs , when hemoglobin concentration decrease to a Pao2 of approximately 50 to 60 mm Hg and an Spo2 of 85% to 90%.  Clinical Signs and Symptoms : Cyanosis In infants , the presence of cyanosis is often a late sign of severe hypoxia which makes it less useful clinical sign. In infants, the stronger affinity of fetal hemoglobin for oxygen results in the Pao2 falling to a significantly lower level before reduced hemoglobin is present at 5 g/dL in arterial blood.  Clinical Signs and Symptoms : Cyanosis In fact, by the time central cyanosis is present in an infant, oxygen delivery to the tissues is grossly insufficient. For this reason, central cyanosis is considered an unreliable indicator of the degree of tissue hypoxia. The clinical impression of cyanosis in an infant must be confirmed by arterial blood gas analysis or pulse oximetry.  Complications : Complications of therapeutic oxygen administration are separated into two categories: Adverse physiologic effects Equipment-related complications Complications : Adverse Physiologic Effects The use of high FIO2 might lead to the following complications: Suppression of the ventilatory drive in some chronic lung disorders with chronic carbon dioxide retention. Retinopathy of prematurity (ROP). Atelectasis. Pulmonary vasodilation. Pulmonary fibrosis.  Complications : Adverse Physiologic Effects In certain chronic lung disorders, including cystic fibrosis and bronchopulmonary dysplasia, the normal response to ventilation is blunted because of chronic carbon dioxide retention. Abrupt and excessive increases in supplemental oxygen decrease the respiratory drive and result in hypoventilation and respiratory acidosis that may lead to respiratory arrest. Supplemental oxygen should be initiated at a low Fio2 and increased on the basis of the results of Pao2 or Spo2 monitoring.  Retinopathy of Prematurity (ROP) Hyperoxia and loss of maternal fetal interaction is believed to cause the suppression of growth factors and constriction of retinal and cerebral vessels in premature neonates, which can lead to ischemia, varying degrees of retinal scarring, and retinal detachment. ROP may resolve spontaneously or result in permanent visual impairment, including blindness.  ROP Many other factors, in addition to oxygen, appear to correlate with the development of ROP, including: Gestational Age Swings In Oxygenation Intraventricular Hemorrhage Swings In Blood Pressure Sepsis Low Birth Weight  One of the factors in the pathogenesis of ROP is the altered regulation of vascular endothelial growth factor (VEGF) Also, the repeated cycles of hyperoxia or hypoxia favor the progression of ROP. Current practice supports oxygen therapy targeting Spo2 levels at 88% to 95% and maintaining a Pao2 value of 50 to 80 mm Hg in premature neonates. Atelectasis: When high oxygen levels, the alveolar oxygen tension (Spo2) may increase and the alveolar nitrogen decrease, resulting in absorption atelectasis. Pulmonary vasodilation: High Fio2 levels may also result in pulmonary vasodilation. As the pulmonary vasculature dilates and alveolar volumes decrease, areas of ventilation–perfusion mismatch occur with increased intrapulmonary shunting and worsening of arterial oxygen delivery. Pulmonary fibrosis : There are also reports of pulmonary fibrosis occurring after oxygen administration to patients with Paraquat poisoning and to those receiving the chemotherapeutic agent bleomycin OXYGEN ADMINISTRATION Many of the devices used to deliver supplemental oxygen to neonatal and pediatric patients are simply smaller versions of the adult devices.  Classification of Oxygen Therapy Modalities : Oxygen devices are classified in two main categories: o Variable performance oxygen delivery systems (low-flow and reservoir systems) o Fixed-performance oxygen delivery systems (high-flow systems). o Enclosure oxygen delivery system  Variable performance oxygen delivery systems (low-flow and reservoir systems) These devices are not capable of meeting the patient’s inspiratory demand These devices provide a fractional concentration of delivered oxygen (Fdo2) that varies with the patient’s rate and depth of ventilation and the flow rate of the gas. These devices include low-flow nasal cannulas, simple oxygen masks, partial-rebreathing masks, and nonrebreathing masks o  Fixed-performance oxygen delivery systems (high-flow systems). These devices include devices that can meet or exceed the patient’s inspiratory demand These devices provide an accurate Fdo2 that is not affected by changes in the ventilatory pattern. These devices include high-flow nasal cannulas, air-entrainment masks, air-entrainment nebulizer systems, and oxygen blender systems  Enclosure oxygen delivery system The last category of oxygen delivery devices includes enclosure systems that provide some means of controlling oxygen concentration, temperature, and humidity. These devices include oxygen hoods, oxygen tents, and closed incubators.  Nasal Cannula The nasal cannula consists of flexible small-bore tubing ending in two soft prongs that are about 0.25 to 1 cm in length. Oxygen flows from the cannula into the patient’s nasopharynx, which acts as an anatomic reservoir. The nasal cannula provide low oxygen concentrations from approximately 24% to 45%, with the Fio2 varying with the patient’s inspiratory flow  Advantages: Allows for feeding and providing care for the patient without interrupting the delivery of oxygen. Allows the patient greater mobility, which may increase interactions with the patient’s caregivers and environment. Contraindications : Nasal cannulas are contraindicated in patients with nasal obstruction, such as facial trauma and choanal atresia Application : The appropriately sized cannula is selected, and the prongs inserted into the patient’s nares, making sure that the nares are not completely occluded. The lightweight tubing is wrapped around the ears and held under the chin with an adjustable plastic notch. For a very small or active infant, the cannula is secured to the face to prevent dislodgment and the tubing is positioned past the ears, securing it behind the head, instead of under the chin, to prevent airway obstruction.  Using adhesive tape to secure the cannula to neonatal skin could cause: Epidermal stripping can result each time the tape is moved to readjust the tubing. Skin irritation can also occur from a local allergic reaction to polyvinyl chloride. A better alternative to adhesive tape are: NeoHold cannula/tubing holder Tender Grip skin fixation system microporous tape  Application : 1. Sizing: the prong on the cannula should not totally fill the nostril, it should be approximately half the size of the nostril. 2. Place strips of hydrocolloid dressing along clean and dry cheeks. 3. Position prongs in the nostril, and apply tape over the cannula tubing. 4. 4. Check there is no pressure on the nasal septum and nostrils. Ensure the tape does not sit too close to their eyes. Blenders and low-flow flow meters Two methods of providing oxygen at low flows through a nasal cannula are common in neonatal and pediatric units : The nasal cannula is connected to a flow meter attached to an air–oxygen blender. The nasal cannula is connected to ad bubble humidifier and low-flow flow meter.  Flow Rate Settings: The flow rates range from 0.1 to 3.0 L/minute, with some adjustable in increments of less than 0.125 L/minute. Many protocols begin the flow rate at 1 L/minute. The flow rate should be decreased in small increments of 0.1 to 0.2 L/minute until reaching the flow necessary to maintain adequate Spo2 levels  Inspired oxygen determination Fio2 provided with a nasal cannula is controlled primarily by varying the flow rate of the gas or the oxygen concentration of the blender. At low flow rates, Fio2 also varies with the patient’s minute ventilation and the relative duration of inspiration and expiration. Fio2 may decrease as a result of room-air entrainment that occurs during the patient’s inspiration. The Fio2 is higher in infants receiving oxygen via nasal cannula than in adults and can exceed potentially toxic levels. When compared with an adult patient, an infant can experience a substantial difference in Fio2  Regression Equation for Estimating Nasal Cannula Fio2 at Low Flow Rates Approximate Fio2 = (O2 flow x 0.79)[(0.21 x VE)/( VE x 100)] This equation is most predictive with an assumed tidal volume of 5.5 mL/kg for infants less than 1500 g.  Hazards and complications An increase in exhaled resistance can result in substantial inadvertent positive expiratory airway pressure (PEP) being delivered to an infant’s airway. Significant PEP tends to occur more often when the cannula has large-diameter prong tips and when flow rates are set above 2 L/minute in smaller infants and toddlers. PEP that impedes venous return may precipitate intraventricular hemorrhage in neonates and can be harmful to an infant with obstructive pulmonary disease. PEP could lead to pneumothorax, pulmonary interstitial emphysema, and pneumopericardium. Hazards and complications Displaced and resulting in loss of oxygen delivery. Increase the patient’s work of breathing. Irritation. Drying of the nasal mucosa. Airway obstruction caused by mucus.  Disadvantages: Instability of oxygen administration in transitions between oral and nasal breathing The lack of precise knowledge concerning the delivered oxygen concentration Unknown Fio2 values may contribute to inconsistent weaning practices that could potentially result in unnecessary days of supplemental oxygen, delays in hospital discharge, and high costs of care.  Simple Oxygen Mask Flow rates from 6 to 10 L/minute provide a variable Fio2 of 0.35 to 0.5. Open ports on both sides of the mask allow exhalation and also allow the patient to draw in room air during inspiration. Fio2 varies with the patient’s inspiratory flow and the oxygen flow into the mask. Room air is entrained through the exhalation ports in the mask if the patient’s inspiratory flow rate exceeds the oxygen flow rate.  Indications: simple mask is used for infants and children who need moderate concentrations of supplemental oxygen for short periods. Such situations include medical transport, emergency stabilization, postanesthesia recovery, and during medical procedures. contraindications: The oxygen concentrations may be higher in patients with small tidal volumes, and therefore simple masks are not suitable for infants and small children who require low or precise concentrations of oxygen.  Application The mask is secured around the patient’s head by a strap, and oxygen is delivered to the mask from a flow meter and bubble humidifier through small-bore tubing. In older children and adults, 6 L/minute is the recommended minimal flow rate to flush accumulated carbon dioxide.  Hazards and complications Infants and small children often refuse to keep the mask on. The confinement of the mask interferes with speech, eating, and breast- or bottle-feeding and may increase the risk for aspiration of vomitus. The elastic strap is often uncomfortable and can cause skin irritation with prolonged use.  Reservoir Masks There are two types of reservoir masks: partial-rebreathing and non-rebreathing masks. Reservoir masks have the advantage of providing high concentrations of oxygen. The use of reservoir masks is limited to short-term situations requiring high Fio2 administration or specific gas mixture therapy. Reservoir masks are not recommended for use in the neonatal population.  Partial-rebreathing mask It is similar to a simple oxygen mask but contains a reservoir bag at the base of the mask. Flow rate range : 6 to 15 L/minute. An Fio2 of up to 0.6 is delivered to the patient. If the reservoir bag becomes totally deflated when the patient inspires, the flow rate should be increased. Nonrebreathing mask A one-way valve located between the face mask and the reservoir bag allows 100% source gas to enter the mask during inspiration. Oxygen concentrations can conceivably reach greater than 90%.  Air-Entrainment Mask Venturi masks. Provides a total flow of gas that exceeds the patient’s ventilatory demands. The performance of the mask is based on Bernoulli principle. By varying either the diameter of the jet orifice or the size of the entrainment ports, the amount of room air entrained can be proportionally changed  Indications: For patients who require a controlled Fio2 at either low or moderate levels. Oxygen concentrations ranging from 24% to 50%. Hypoxic child with increased ventilatory demands. Pediatric patients with chronic carbon dioxide retention who have the potential to hypoventilate with increased oxygen concentrations.  Hazards and complications Correct performance of the air-entrainment mask can be altered by resistance to the flow of gas that may occur distal to the restricted orifice. The resistance to flow at this particular point creates backpressure, resulting in less air entrainment. If total flow decreases significantly, room air may be inhaled around and through the mask ports  Hazards and complications Resistance to the flow of gas that may occur distal to the restricted orifice can altered the performance of the device. As a result, higher oxygen concentrations and lower total flows are delivered to the patient. If total flow decreases significantly, room air may be inhaled around and through the mask ports. This same phenomenon will occur if the entrainment ports are partially or completely obstructed.  Air-Entrainment Nebulizer The gas-powered, large-volume, or all-purpose nebulizer is another fixed-performance system. The device provides 100% body humidity. The nebulizer provides oxygen at fixed concentrations by adjusting the size of the air entrainment port located at the top of the nebulizer. The maximal flow is 15 L/minute.  Indications and contraindications Air-entrainment nebulizers are used when high levels of humidity or aerosol are desired. Patient application devices used with the nebulizers include a tracheostomy collar, face tent, and aerosol mask. Application  Hazards and complications The aerosol mask could cause agitation and anxiety. Condensate in the aerosol tubing is considered infectious waste and should never be drained back into the nebulizer. The weight of the T-piece could cause tracheal irritation and possible displacement. A cool mist is not recommended for newborns because it might induce cold stress  Hazards and complications If the gas flow from the oxygen source is cool and is directed toward the infant’s face, stimulation of the trigeminal nerves may cause alterations in the respiratory pattern and lead to apnea.  High-Flow Nasal Cannula Studies with neonates through adults have been favorable, with data showing that high-flow nasal cannula (HFNC) provid moderate to high Fio2 values and possibly providing a cost-efficient alternative for patients who require this level of oxygen concentration. Continuous positive airway pressure (CPAP) has previously been regarded as the gold-standard for noninvasive support in this population. HFNC is a form of noninvasive respiratory support is increasingly being used as an alternative form of respiratory support in neonatal intensive care units (NICU) in preterm infants with respiratory illnesses. Definition of High flow Nasal Canula High Flow Nasal Canula(HFNC) refers to the delivery of humidified heated and blended oxygen/air at flow rates greater than 2L/min via nasal cannula. Some authors adjust the flow rates on body weight and recommend using 2 L/kg/min, which provides a degree of distending pressure and reduces the work of breathing. In children, flow rates >6 L/min are generally considered high flow.  Mechanisms of action of HFNC The warm humidification may have likely contributed to: Improvement of airway function by maximizing mucociliary clearance and preventing inflammatory reactions. Inhibition of the bronchoconstrictor reflex, which in turn prevents the increase in airway resistance that is often triggered by cold air. Washout of Nasopharyngeal Dead Space : NHF allows for a very effective flushing of the nasopharyngeal dead space, resulting in alveolar ventilation being a higher fraction of minute ventilation (the volume of gas inhaled or exhaled from the lungs per minute) The flow of gas during HFNC flushes CO2 from the nasopharynx, facilitating clearance of CO2 and improving oxygenation by creating a reservoir of fresh gas in the airway Reduction in the work of breathing  Clinical trials support the conclusion that dead-space washout provides a ventilation effect. One study show that infants were able to be extubated to HFNC from significantly greater ventilator rates (33 vs. 28 breaths per minute) compared with other noninvasive support modes. Also, a case report of a pediatric burn patient showed respiratory rate decreased immediately after initiation of HFNC (63-38 breaths per minute), with a secondary sustained decrease in heart rate (175-144 beats per minute) after a short period of HFNC. Provision of distending airway pressure Providing distending pressure to the lungs improves ventilatory mechanics by optimizing lung compliance and assists with gas exchange by maintaining the patency of the alveoli Initial data from premature infants showed that increasing HFNC flow rates resulted in increased pharyngeal pressures Pressures generated in the nasopharynx with HFNC were within the range of commonly used CPAP pressures. Appropriate prong-to-nares ratio is essential to achieve adequate, but not excessive, positive pressure support. When similar end-expiratory pressures were applied, there was no difference in breathing pattern, gas exchange, lung mechanics or work of breathing between NHF and CPAP, according to a study in 20 preterm infants with mild to moderate respiratory distress.  Indication for HFNC in Neonates HFNC is recommended in the following conditions: Hypoxemia that have not responded to oxygen administered with a low-flow nasal cannula. Lung disorders that require improvement in oxygenation or a reduction in work of breathing. Non-invasive ventilation for infants with ongoing parenchymal lung disease (HMD/pneumonia/CLD/ MAS/ pulmonary hypoplasia/ bronchiolitis) Management of apnea of prematurity. To reduce the potential risk of the iatrogenic injuries associated with CPAP and mechanical ventilation. Primary treatment for RDS  Contraindications: Suspected or confirmed pneumothorax. Severe upper airway obstruction (Upper airways abnormalities precluding the placement of prongs ) Need for intubation: ❖ ventilatory failure ❖ severe cardiovascular instability ❖ unstable respiratory drive with frequent apneas (absence of spontaneous ventilation)  Application Most systems offer several cannula sizes: Premature Neonatal Infant Intermediate infant Pediatric Adult The appropriate prongs size should not occlude the patient’s nares.  Gas source and flowmeter Blender HFNC Components Heated circuit Nasal cannula Heated humidifier Sterile water Internal battery Types A. OPTIFLOW B. AIRVO C. VAPOTHERM HFNC Settings in Neonates Fio2 (21% - 100%) Initial gas flow start at Flow (4 L/m – 6 L/m) for preterm and term infants. Flow rate may be adjusted to body weight, i.e., 2 L/kg/min. Temperature (34 ° C – 37 ° C) Recommend Flow Rate in Neonates According to the Literature Appropriate population for NHF Current evidence supports the application of NHF for: Post-extubation support of neonates ≥ 28 weeks’ instead of nasal CPAP As an alternative to CPAP for stable infants who continue to require respiratory support above the level of standard Oxygen therapy There was general agreement, but not consensus, that HFNC can be used as the primary mode of support for neonatal respiratory distress at the clinician’s discretion (based on the neonate’s GA and the level of oxygen support required)  Post-extubation Studies involving more than 1100 preterm infants indicates : HFNC was as effective and as safe as nasal CPAP. Failure rates were similar and there was no increase in adverse events, air leaks, or durations of oxygen use or hospital stay with HFNC. Comfort scores of neonates were similar, but care of the infant was easier with HFNC. HFNC was associated with reduced rates of nasal trauma and potentially a reduced incidence of pneumothorax in preterm infants.  Titration of HFNC in Neonates The approach to either escalation or weaning HFNC should be based on signs of distress or increase in WOB, as well as the FiO2 needed to maintain targeted SpO2. Weaning HFNC : weaning is considered in infants who have been stable for 12-24 hours 1. FiO2 should be weaned first to 0.40) or with increased WOB or distress ❖ For any baby being weaned on High Flow : If a significant and sustained increase in o Respiratory rate o Oxygen requirement o Work of breathing is seen in the 24 hours after weaning, then it is a clinical decision whether to revert back to the previous flow rate, or to continue at the new flow rate with close observation.  Assessment of outcome ROX index >or = 4.88 Little risk for intubation 3.85 – 4.87 Monitor due to increased risk of intubation 2.85 – 3.84 Close monitoring in ICU if possible. High risk of needing intubation < 2.85 Consider intubation Benefits of HFNC in Neonatal Population Babies on HFNC appear to be well settled and more comfortable than babies on CPAP. Less abdominal gaseous distension than CPAP Babies do not require “time off” for nose breaks or changes between nasal prongs / masks, reducing the amount of handling. Some evidence for better weight gain and improved feed tolerance. Parents have reported preferring being able to see more of their babies face. Easier access for cranial ultrasound scans and head circumference measurements. HFNC in Pediatric Patients Settings: In children, flow rates are greater than 6 L/min and may be up to 20 to 30 L/min Optimum flow rate can be closer to 1 L/kg/min or (First 10 Kg of weight x 2) + (rest of weight x 0.5). FiO2 is set to achieve target saturation between 92% and 97%. The gas temperature is set around 37°C in order to reach optimal humidification. If the patient’s room is cool, it may be useful to insulate the tubing or to use breathing circuits with heating wires to limit condensation and the spray of water droplets into the child’s nostrils. If the phenomenon continues, the heater temperature can be reduced to a minimum of 34°C.  Weaning from HFNC Wean Fio2 in 5% to 10% increments until