NEONATAL RESPIRATORY CARE: CLINICAL APPLICATIONS

Transcription

1 By Kevin T. Martin BVE, RRT, RCP RC Educational Consulting Services, Inc Van Buren Blvd, Suite B, Riverside, CA (800) 441-LUNG / (877) 367-NURS

2 BEHAVIORAL OBJECTIVES BY THE END OF THE READING MATERIAL, THE PRACTITIONER WILL BE ABLE TO: 1. Describe the complications of oxygen therapy. 2. Describe the indications for: a. Oxygen therapy. b. Continuous distending pressure. c. Mechanical ventilation. 3. Recommend modification with the use of Continuous Distending Pressure. 4. Describe the proper procedure to wean a neonate from oxygen therapy. 5. Compare the relationship between inspiratory time, expiratory time, frequency, and I:E ratio. 6. Describe the effects of airway obstruction on I:E ratio. 7. Describe the effects associated with increased peak inspiratory pressures on tidal volume. 8. Identify acceptable blood gas values ranges for the neonate. 9. Compare and contrast acceptable PaCO 2 and ph values. 10. List the factors affecting transcutaneous measurements. 11. Describe the complications associated with suctioning. 12. Explain the importance of proper neck position of the neonate during CPR. 13. Select proper resuscitation bag for the transport of a neonate. 14. Determine initial settings for mechanical ventilation. 15. Discuss factors affecting oxygenation in the mechanically ventilated neonate. 16. Describe ways to improve the oxygenation of mechanical ventilated patients. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 2

3 17. Identify situations when it is acceptable to promote the use of IMV. 18. Choose correct endotracheal tube size based upon infant weight. 19. Identify the common clinical symptoms of hypoxemia. 20. Name the narrowest point in the upper airway of a neonate. COPYRIGHT MARCH, 1989 BY RC Educational Consulting Services, Inc. COPYRIGHT April, 2000 By RC Educational Consulting Services, Inc. (#TX ) AUTHORED BY KEVIN T. MARTIN, BVE, RRT, RCP REVISED 1992, 1995 BY KEVIN T. MARTIN, BVE, RRT, RCP REVISED 2001, BY ANNE B. FASCIO, RRT, RCP AND PHILIP M. SORKIN, RRT, RCP, PERI/PED RESPIRATORY CARE SPECIALIST AND MICHAEL R. CARR, BA, RRT, RCP REVISED 2004 BY DENISE M. REES, RRT, RCP REVISED 2007 BY MICHAEL R. CARR, BA, RRT, RCP ALL RIGHTS RESERVED This course is for reference and education only. Every effort is made to ensure that the clinical principles, procedures and practices are based on current knowledge and state of the art information from acknowledged authorities, texts and journals. This information is not intended as a substitution for a diagnosis or treatment given in consultation with a qualified health care professional. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 3

4 TABLE OF CONTENTS INTRODUCTION...7 OXYGEN THERAPY...7 COMPLICATIONS AND CAUTIONS...7 SYMPTOMS OF HYPOXEMIA...9 OXYGEN DELIVERY DEVICES...10 ADMINISTRATION...13 WEANING FROM OXYGEN...14 CONTINUOUS DISTENDING PRESSURE...14 INDICATIONS...14 DEVICES AND MODES...15 INITIATION AND MANAGEMENT...17 MONITORING...18 WEANING...19 COMPLICATIONS...19 MECHANICAL VENTILATION...20 INDICATIONS...21 MANUAL VENTILATION...22 MECHANICAL VENTILATORS...22 IMPORTANT CONCEPTS...23 INITIAL SETTINGS...25 VENTILATOR MANAGEMENT...28 This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 4

5 WEANING...30 HIGH-FREQUENCY OSCILLATORY VENTILATION...31 AIRWAY CARE...33 SUCTIONING...33 INTUBATION...36 TUBE POSITION...37 SECURING THE TUBE...38 EXTUBATION...38 BRONCHIAL HYGIENE/CHEST PHYSICAL THERAPY...39 AEROSAL THERAPY...40 ASSESSMENT AND MONITORING...40 PHYSICAL EXAMINATION...41 PULMONARY FUNCTION TESTING...42 LAB VALUES...42 CHEST X-RAY...42 MONITORING...43 TRANSCUTANEOUS MONITORING...44 OXIMETRY...45 ARTERIAL AND CAPILLARY BLOOD SAMPLING...46 ARTERIAL LINES...46 ARTERIAL PUNCTURES...47 CAPILLARY SAMPLING...47 This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 5

6 SURFACTANT REPLACEMENT...47 TRANSPORT...48 CLINICAL PRACTICE EXERCISE...49 SUMMARY...51 PRACTICE EXERCISE DISCUSSION...54 SUGGESTED READING AND REFERENCES...55 This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 6

7 INTRODUCTION The material contained herein can be a useful introduction to the various respiratory care procedures performed on the neonate. The following should be considered general guidelines for each procedure discussed. Each institution will have specific guidelines for the standard of care to be practiced by their staff. The following procedures will be discussed: oxygen therapy, continuous distending pressure, mechanical ventilation, airway care, bronchial hygiene therapy, assessment, monitoring, surfactant replacement, and transport. OXYGEN THERAPY The American Academy of Pediatrics (AAP) has established standards and set forth recommendations for administering oxygen to the newborn infant. The goal of oxygen therapy is to provide adequate oxygenation and avoid the consequences of hypoxemia. Unlike the adult, indiscriminate use of O 2, even for short periods, can have dire consequences for the neonate. All efforts to minimize the quantity or duration of oxygen therapy should be made. If, however, the practitioner is faced with a blue or pale baby, oxygen should be provided. Oxygenation status needs to be continuously monitored via blood gases, transcutaneous oxygen monitoring (TCOM), and/or oximetry and documented. PaO 2 can fluctuate rapidly in infants so FIO 2 or liter flow needs to be constantly monitored and titrated. The neonate less than 36 weeks should be provided an FIO 2 that gives a PaO 2 between 50 to 80 mm Hg or a capillary PO2 between 40 to 50 mm Hg. COMPLICATIONS AND CAUTIONS Transcutaneous Monitor Gas Calibrator Model 868 Compliments of Novametrix Medical Systems Inc. Both adults and neonates suffer the effects of oxygen toxicity on the lungs. These effects (hyaline membranes, stiffening parenchyma, pulmonary edema, etc.) are believed to be a result of an increase in oxygen radicals. These radicals disrupt normal metabolism at the This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 7

8 cellular level and cause a decrease in surfactant production. An increase in oxygen radicals is directly related to an increase in FIO 2. Obviously, the greatest danger exists at an FIO 2 of 100%. Oxygen toxicity can occur within 24 to 72 hours at 100%. The lower the FIO 2, the longer it will take to develop symptoms. Levels less than 40% are considered nontoxic to the lungs. Levels more than 40% can be toxic to other organs if they result in an excessive PaO 2. PaO 2 s in excess of 100 mm Hg, particularly in the premature infant, can be damaging to the eyes. Excess PaO 2 (more than 100 mm Hg) can result in the condition of retinopathy of prematurity (ROP) in infants. ROP is a result of an excess of oxygen in the blood causing vasoconstriction of immature retinal vessels. If the vasoconstriction continues for several hours, vessels can be destroyed. New vessels are then formed and proliferate in the eye. This will result in retinal hemorrhage, detachment, or the new vessels can cover the retina. There can be varying degrees of sight loss, up to and including total blindness. ROP can develop in as little as 2 to 3 hours. It is most common in premature infants less than 1500 grams and rare in infants greater than 2500 grams. Blood gases of arterial blood supplying the head should be obtained. Blood from a peripheral or umbilical artery is sufficient should there be no ductal shunt. If a ductal shunt is present, blood from the right radial, brachial, or temporal artery is necessary. Continuous non-invasive monitoring also should be used. Transcutaneous or oximetry readings should be obtained from the right (preductal) and left (postductal) upper chest when a ductal shunt is suspected. A significant difference indicates a ductal shunt. A difference of 5 to 10 mm Hg in transcutaneous readings is fairly diagnostic. One also should note the use of anesthesia in considering the potential for ROP. Anesthesia can lower the threshold for ROP causing it to occur at a lower PaO 2. Absorption atelectasis is always a potential complication of an elevated FIO 2. It occurs as a result of replacing the nitrogen in the alveoli with oxygen. Normally, nitrogen acts as a splint to help maintain alveolar patency. (It is physiologically inert and does not diffuse out of the alveoli like oxygen.) If the nitrogen is washed out by oxygen and that oxygen diffuses into the blood, there is little left to keep the alveoli open. Note: The reader may find it interesting that a small percentage of otherwise healthy normal full term babies have small, spontaneous pneumothoraces probably due to birth trauma. One possible explanation might be that the neonate s chest has been squeezed in the birth canal, and then at the moment of birth, there is recoil of the chest. Rapidly following are the first few breaths, which require high pressures to inflate the lungs initially. A baby may present in the regular nursery with tachypnea. Subsequent evaluation and a chest X-ray reveal the presence of a small pneumothorax. One method of treatment is the nitrogen washout. The infant is placed in an oxyhood with as close to 100% oxygen as possible for several hours. On 100% O 2 all the nitrogen is gone so significant amounts of atelectasis can develop rapidly. A repeat chest X-ray hopefully shows the pneumothorax resolved. This is the expected result. The baby can be removed from the oxyhood immediately rather than weaning from O 2, and the nitrogen washout was successful in treating this problem. This would not be good for a premature infant however. Rapidly This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 8

9 developing absorption atelectasis is even more pronounced in the premature infant because they are hampered by an immature surfactant-producing system. This lack of surfactant leads to early collapse. The addition of positive pressure appears to accelerate the toxic effects of oxygen. Elevated FIO 2 combined with positive pressure ventilation can lead to a form of chronic lung disease known as bronchopulmonary dysplasia (BPD). BPD is much more common with the premature infant, particularly those who suffer from respiratory distress syndrome (RDS). Infants less than 1500 grams are more likely to develop BPD. SYMPTOMS OF HYPOXEMIA Anormal infant respiratory rate (RR) is 40 to 60 per minute. A sustained rate greater than this can indicate hypoxemia. Heart rate also will increase above the norm of 120 to 160 per minute (as the heart rate increases, the ventricular filling time decreases causing a drop in cardiac output). As hypoxia becomes severe or prolonged, tachypnea and tachycardia will reverse to bradypnea, bradycardia, apnea, or asystole. An increase in frequency/respiratory rate is one of the first symptoms of hypoxemia. Chest retractions on inspiration are present when there is an increase in the respiratory demand. An increase in demand leads to an increase in the force of contraction. This pulls the soft tissues of the thorax and the rib cage in on inspiration. This is particularly prominent on the premature infant when they are asleep. They lack intercostal muscle tone during most of their sleep cycle. Intercostal muscle tone normally helps stabilize the chest. The more severe the hypoxia, the more evident will be the retractions. If the increase in respiratory demand is due to lung disease, retractions will be more pronounced. An expiratory grunt may or may not be present depending upon the cause of hypoxemia. Hypoxemia related to lung disease will present with grunting. Lung disease usually results in alveolar instability and collapse. The expiratory grunt is a mechanism to keep alveoli inflated and exchanging gas (much like purse lip breathing in the adult). Grunting is less likely when the hypoxemia is related to other causes. Nasal flaring is common. Neonates are obligate nose breathers. When they become distressed, the nares will flare out on inspiration. They give the appearance of dilating on inspiration to obtain more air. Nasal flaring is usually present despite the cause of the hypoxemia (this is a very obvious sign of air hunger). Temperature regulation, as discussed in the Neonatal Respiratory Care: Essential Care course, is very unstable in the neonate. Hypoxemia may result in a fall in temperature. Heat production requires oxygen and if not present, temperature drops. Cyanosis will be present in severe hypoxemia, but less so for milder cases. In order for cyanosis This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 9

10 to be clinically evident, there must be 5 grams % of reduced hemoglobin. If fetal hemoglobin (HbF) is present, PaO 2 may have to decrease to 30 to 40 mm Hg for this to occur. HbF has a much higher affinity for O 2 than adult hemoglobin. So it will remain well saturated as PaO 2 falls considerably. HbF is replaced by adult hemoglobin in the first few months, or sooner if the baby is transfused. If adult hemoglobin is present, PaO 2 may still have to decrease to 50 mm Hg and % saturation to 80% for cyanosis to be evident. OXYGEN DELIVERY DEVICES M ost oxygen delivered to the infant is via oxyhoods or nasal cannulas. Nasal catheters are less common, and oxygen via isolette/incubator is possible but less efficient. Isolette/incubator - FIO 2 in an isolette can fluctuate considerably. It will depend upon the amount of oxygen flow into the isolette, the presence of leaks, and how much or how often it is opened. Rapid and substantial fluctuations can occur. Theoretically, it is possible to achieve an FIO 2 of 40 to 100% in an isolette but it will be very difficult to regulate. Because of the variability of FIO 2, babies can be maintained with a nasal cannula or oxyhood INSIDE the isolette, rather than using the isolette as the delivery device. (In fact, isolettes are rarely used as an O 2 delivery device in current practice). Air Shields Compliments of Medcom.ru An isolette can be single or double-walled. A single-walled isolette will cause radiant heat loss of the infant. If they are being used, a plastic heat shield should be placed over the infant. There are many products commercially available. When caring for micropreemies, for the first several days of life, heated aerosol or humidified gas is frequently delivered into these body hoods which helps maintain both temperature stability and skin integrity. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 10

11 Oxyhoods - These are devices that enclose the head of the infant with therapeutic gas. They can be either a clear, plastic cylinder with removable lid, a mini O 2 tent composed of a framework and plastic canopy placed around the head, or other plastic devices. There is an opening for the neck. These are not airtight devices and one does not strive for a complete seal. Leaks are, in fact, necessary to allow for exhaled CO 2 to escape. The cylinder-type oxyhoods have a hole in the lid to allow for CO 2 to escape. There are inlets for large-bore tubing, temperature probes, and oxygen analyzer probes. Sensors should be placed as close as possible to the infant s face. Flow from the oxygen source is baffled to avoid flow on the face. Flow directed on the face or body can result in apnea and heat loss. Baffles also serve to decrease sound levels in the hood. The gas must be warmed and humidified. An air-entrainment device should not be used for humidification purposes, if possible. These devices can transmit considerable noise to the hood and damage hearing. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 11

12 Oxyhoods maintain a stable FIO 2 around the infant s head. They can be used with or without an isolette for this purpose. Temperature and FIO 2 inside the oxyhood need to be carefully monitored. Too cold of an environment will increase oxygen consumption and cause heat loss. Too hot of an environment will cause apnea and dehydration. Flow to the hood must be high enough to flush out exhaled CO 2. A flow of 5 to 10 liters per minute (lpm) is usually sufficient. Be careful to avoid pressure necrosis around the neck from too small of an opening. Cannulas and catheters - Once used nearly exclusively on babies who had been weaned from the ventilator or oxyhood, now nasal cannulas are frequently used in acute situations. They are available in several sizes appropriate even for babies under one kilogram. Feeding tubes, doubling as nasal catheters, may still be in use at some institutions. They are placed about 2 cm inside either nare and secured with tape or a gentle semi-permeable dressing. A connector is placed between the feeding tube and the O 2 tubing, which is attached to the bubble humidifier. A common practice is to change the nasal catheter to the opposite nare every 12 hours, and every 24 hours replace it. Cannulas and catheters are generally used with low flow flowmeters, some available in tenths of a liter up to 1 liter, some starting at 1/16 of a liter up to 2 liters, some beginning at 1/4 liter up to 3 liters. There are several care plans for oxygen administration, all very different. Each will be discussed under administration. One method is used for the acute infant who needs improved oxygenation. Another plan is implemented for babies who have had episodes of apnea, with or without oxygenation deficits. These babies may be on an FI0 2 of.21, with flows of 1-3 liters a minute to treat apnea. The practitioner might wonder how this can be This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 12

13 therapeutic. It is a form of low tech CPAP. It will be discussed further under administration. Still another care plan may be implemented for infants who are older, or who have chronic lung disease (BPD) also known as reactive airway disease (RAD). One is advised to avoid high flows as these can cause drying of the mucosa and result in an excessive FIO 2 within the alveoli. FIO 2 delivered to the alveoli is affected by the same factors as in the adult (respiratory rate, depth, flowrates, etc.). ADMINISTRATION Oxygen therapy should be provided with low flow flowmeters calibrated for use with infants. An oxygen blender for precise control should regulate FIO 2. When an air-entrainment device is used for humidification and connected to the blender, set it at 100%. This will prevent any entrainment and dilution of the gas coming from the blender. Pass-over humidifiers are generally used for humidification. Aerosols should not be delivered for humidification purposes as they may cause fluid overload. FIO 2 and/or liter flow needs to be monitored constantly and documented at least every 1 to 2 hours. Analyzers need to be calibrated per manufacturer s recommendations and per individual institutional policy. This refers to oxyhoods, as it is not possible to measure the FIO 2 actually delivered via a cannula or catheter except under laboratory conditions. FIO 2 measurement of dry vs wet gas may vary due to water vapor pressure. Drier gas may give a higher FIO 2 due to a lower water vapor pressure. A lower temperature may have the same effect. FIO 2 measurement should be obtained under the same conditions as the infant is breathing. Oxygen should be constantly titrated to maintain acceptable arterial blood gas (ABG) values. Acceptable values are a PaO 2 of 50 to 70 mm Hg; however, some physicians may prefer ranges slightly lower (45-65). Serial arterial blood gases are necessary to evaluate and monitor PaO 2 even when patients are stable. Institutional policy should determine the schedule for drawing ABG s. Continuous monitoring via transcutaneous monitors or oximeters provides vital assessment information. TCOM readings should be noted and the RCP should observe them for trending. A reading of 55 mm Hg when an arterial blood CO 2 is 45 mm Hg shows values that are 10 mm Hg apart. If this trend is noted to be consistent on serial arterial blood gases, then the monitor may be very helpful in patient management. If, however, you have values that are 10 mm Hg apart one time, the next time they are 16 mm Hg apart, and later they are 4 mm Hg apart, they are inconsistent and the TCOM is a less valuable tool in patient management. The high and low alarms should be properly set according to your institution s policy. TCOM accuracy is based on skin perfusion; if skin perfusion is poor this can render the TCOM values almost useless. Continuous monitoring of all vital signs and frequent total infant assessment must be taken into consideration when examining TCOM values. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 13

14 WEANING FROM OXYGEN W eaning from oxygen is a constant process that is merely an extension of the titration of oxygen discussed above. As the patient improves, it takes less FIO 2 to maintain an acceptable blood gas. Eventually, the titration would result in an FIO 2 of 21% (room air). Another tool used in management of oxygen therapy to babies is the pulse oximeter. While not specific for PaO 2, many physicians are quite comfortable using oxygen saturation as a guideline in weaning from oxygen. It is advisable to perform a trial of a decreased FIO 2 to see if the infant can tolerate it, as long as the saturation remains in the range ordered by the physician. The reader is referred to articles that describe the actual hypopharyngeal fractional inspired O 2 at different FIO 2 s, liter flows, and while the baby is crying (mouth open, entraining air). Individual physicians may have preferences regarding lowering liter flows first, then titrating FIO 2 s. It is also to be noted that as mentioned earlier, some babies are on a high liter flow, 1-3 liters, but at.21 FIO 2 for the CPAP effect. In many cases a return of apnea is noted if the liter flow is decreased to less than 1 liter per minute. With chronic oxygen dependent babies, the plan may be for the infant to go home on oxygen. In that case, the RCP need not wean the FIO 2 since home care companies do not provide an oxygen blender. The FIO 2 would remain at 1.0, with the liter flow being adjusted to accommodate the infant s needs. CONTINUOUS DISTENDING PRESSURE Continuous distending pressure (CDP) consists of the administration of either continuous positive airway pressure (CPAP) or continuous negative pressure (CNP). The former is far more common and will be the only mode discussed in this paper. (The terms CDP and CPAP will be used interchangeably in the following discussion.) CDP is a mode of therapy designed to maintain an increased transpulmonary pressure throughout the ventilatory cycle. Often, it is the next logical step when simple oxygen therapy is insufficient to maintain acceptable blood gases. It also can be instituted prior to a failure of oxygen therapy. One should not, in fact, wait until severe hypoxemia or infant fatigue develops before considering CDP. INDICATIONS The flexible thorax and instability of the alveoli were extensively discussed in the Neonatal Respiratory Care: Essential Care course. That discussion emphasized that a strong inspiratory effort can collapse the chest. CDP can be useful in stabilizing the thorax. It can splint the chest to prevent collapse and retractions. If atelectasis has occurred, it may be reversed with CDP. Through the process of collateral ventilation via the pores of Kohn, collapsed alveoli may open up. Alveolar collapse can be prevented until the surfactant producing system becomes mature. Functional residual capacity (FRC) can be restored to normal with CDP so compliance will improve. This will, in turn, reduce intrapulmonary shunting and increase PaO 2. It may be possible to maintain the infant on a lower FIO 2, reducing possible toxic complications related to oxygen. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 14

15 A B C CDP is most useful for conditions causing hypoxemia and a decrease in compliance. It should be considered when the PaO 2 is less than 50 mm Hg on an FIO 2 greater than 40%. The patient should be spontaneously breathing and capable of maintaining a PaCO 2 less than 60 mm Hg. (Some may allow for a greater PaCO 2 as long as ph remains above 7.25.) Occasional manual sighs via a resuscitation bag may be used to keep PaCO 2 down. RDS is probably the most common indication for CDP. Pulmonary edema is another common indication. Some types of neonatal apnea also respond to low CDP levels. The low positive pressure appears to provide enough stimulation to maintain ventilation. DEVICES AND MODES A. Normal alveolus with surfactant. B. Surfactant deficiency causes alveolar collapse. C. CDP reverses collapse and keeps alveoli patent. CDP is commonly delivered via nasal prongs, nasopharyngeal tubes, endotracheal tube, and less commonly, mask or head box chamber. ET tube CPAP is a relatively safe and reliable method of providing CDP to the newborn. The advantage of this mode is that more pressure is actually applied to the lungs and less dissipated in the upper airway. Disadvantages to this mode consist of the numerous complications associated with intubation and an artificial airway. Trauma to the mucosa, infection, tracheal stenosis, vocal cord damage, and retained secretions are a few of those complications. Note that with very small patients with small (2.5) endotracheal tubes, the increase work of breathing may cause fatigue and higher caloric burn off, outweighing the benefit of the distending pressure. (Airway complications are discussed fully in the airway care section that follows.) ET tube CPAP also has the advantage of providing a patent airway and easy connection to a mechanical ventilator, should that prove necessary. It is easy to stabilize the tube and more effectively This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 15

16 control the amount of CDP with this method. Nasal (prong) CPAP is more popular than in the past. It may be possible to avoid intubation on some infants by utilizing nasal CPAP. They are easily applied but challenging to maintain in place. They must be secured in place but still become dislodged easily with movement. Innovations in technology include CPAP drivers, which decrease resistance during exhalation. They are microprocessor driven, electric and pneumatically powered, with built in high and low pressure alarms for safety, oxygen blenders and oxygen analyzer. There are many new styles of headgear and prongs to make securing the CPAP much easier than in the past. They come in a variety of sizes, with charts to assist the practitioner in determining the appropriate size for the patient. Some new prongs are very soft for patient safety and comfort, and some have flared flanges to help keep the prongs from being easily dislodged. Care should be taken to avoid compression of blood vessels in the neck or head when securing the prongs. Compression can lead to an increase in intracranial pressure and possible hemorrhage. If the prongs are too loose, there will be a leak. If too tight, the nasal septum can be eroded. A cap should be used to secure the prongs in place. They are usually provided along with the prongs, complete with instructions for use and diagrams. These help prevent skin irritation or breakdown. There should be two sets so one can be cleaned every shift. Attached tubing must be supported to avoid excess weight on the infant. Prongs can cause pressure necrosis and infection. Excess flow through the prongs can cause a falsely high CPAP pressure reading due to resistance through the narrow lumen. When the infant opens their mouth, effective CPAP pressure is decreased. Fortunately, since infants are nose breathers, the mouth is usually closed and CPAP pressure maintained. Infants may use up considerable energy fighting it and become fatigued. The newer systems have decreased this problem; however, as previously mentioned, the practitioner should keep in This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 16

17 mind that ET tube CPAP can be very tiring for infants with small endotracheal tubes (2.5). The mouth and nose should be suctioned with a bulb syringe or nasal olive PRN for secretion build up. Do not use a steroid cream for the nose as this may cause tissue breakdown. An orogastric tube should always be placed to relieve swallowed air. Nasopharyngeal (NP) tube CPAP is a combination of the above. Endotracheal tubes are cut and inserted through the nares into the nasopharynx. The distance of insertion is measured from the tip of the nose to the tragus of the ear. This will place the distal end of the tube posterior to the uvula. The tubes are then connected to the CPAP source. NP tubes are less easily dislodged than prongs and many of the complications associated with intubation are avoided. More pressure is transmitted to the lungs than with prongs alone. Damage to the nose is possible with NP tubes so caution is again advised. New technology has brought new products. There are now very soft, flexible binasopharyngeal prongs, much longer than previous CPAP prongs, with universal sized adapters to attach to the CPAP source, usually a ventilator or, as mentioned, the CPAP driver. Edema, inflammation, or trauma in this area will significantly increase airway resistance when the tube is removed. Sometimes for mild atelectasis, chest physiotherapy and suction may be needed to stimulate a deep breath and mobilize secretions. The frequency is determined by the need using chest X- rays, blood gases, physical examination including breath sounds. It is important to coordinate with the feeding schedule so that the CPT and suctioning precedes feedings. It is also important to cluster the care to optimize the amount of uninterrupted sleep the infant gets for optimum growth and development. INITIATION AND MANAGEMENT One usually initiates CPAP at 4 to 6 cm H 2 O. If necessary, CPAP is increased by 1 to 2 cm H 2 O until an acceptable PaO 2 (greater than 50 mm Hg) is achieved. It may be wise to initially increase FIO 2 5 to 10%. The maximum CPAP level for a given patient is based upon weight: WEIGHT MAXIMUM CPAP 1000 grams... 8 cm H 2 O 1500 grams...10 cm H 2 O 2000 grams...12 cm H 2 O 2500 grams...12 cm H 2 O Obtain ABG s after initiation of CPAP. Continuous monitoring via TCOM or oximetry is recommended. (It is particularly important to monitor the patient during suctioning when the CPAP is removed.) The patient s clinical condition, chest X-ray, and ABG s should be monitored to evaluate the This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 17

18 effectiveness of therapy. These should show stabilization and resolution before any attempt at weaning is made. Sometimes for mild apnea or periodic breathing, a low rate can be set on the ventilator. This is called Nasal IMV or NCPAP with a rate. The practitioner is advised that this is not life support. If the PaCO 2 rises or apnea persists, another modality might be apnea back up where, if there is an apnea for a specific time (>20 seconds), the CPAP/Vent will go into auto-cycle at prescribed PIP s and rate to try to stimulate (sniff reflex) the infant to breathe. If this fails, the infant will require more aggressive management, probably intubation and mechanical ventilation. CPAP should be increased when one is unable to obtain an acceptable PaO 2. This is not uncommon in RDS since the syndrome worsens within the first 24 hours. If FIO 2 requirements are increasing, adjust CPAP in 1-2 cmh 2 O increments as long as there is an increase in the PaO 2. MONITORING M onitoring of the central venous and/or esophageal pressure can be very useful to detect excessive CPAP levels. An increase in central venous pressure (CVP) of 25% with an increase in the CPAP level is an indication that overdistention has taken place. A decrease in CPAP should return the CVP to previous values. An increase in esophageal pressure of 3 cm H 2 O is also an indication to decrease CPAP. Esophageal pressure reflects pleural pressure so an increase indicates overdistention. A rising PaCO 2 can be an indication of an increase in dead space ventilation or overdistention. It can also indicate impending respiratory failure. Clinical judgement must be used on whether to decrease CPAP or change to IMV if PaCO 2 increases. The effect of CPAP can be assessed by a decrease in the signs of respiratory distress. A decrease in frequency, retractions, cyanosis, see-saw respiratory movements, or improved blood gases should be seen. The optimal CPAP level is the level at which one sees a significant increase in the PaO 2 using the least amount of CPAP possible. CPAP can be considered a failure if greater than 12 cm H 2 O with 100% FIO 2 does not provide a PaO 2 of 50 mm Hg or more. Mechanical ventilation should be considered at this point. General guidelines for considering the addition of IMV are: Greater than 12 cm H 2 O CPAP with 100% FIO 2 does not provide a PaO 2 of greater than 50 mm Hg. Apnea with bradycardia. Apnea with lung disease (hyaline membrane disease). This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 18

19 PaCO 2 greater than 70 mm Hg with ph less than High CVP or esophageal pressure with a poor PaO 2. WEANING F IO 2 is generally the first parameter to be weaned. As the patient improves: 1. Initially decrease FIO 2 in 2 to 10% increments, according to patient tolerance, to 60% (some prefer 40%). The amount of each decrease will be based upon the disease process. For example, a decrease of 2% would be appropriate for hyaline membrane disease whereas a decrease of 10% is more appropriate for transient tachypnea. 2. At 60% FIO 2, begin decreasing CPAP 1 to 2 cm H 2 O until CPAP is 4 cm H 2 O. 3. Decrease FIO 2 in gradual increments to 40% (if not already done). 4. Decrease CPAP to a minimal CPAP of 2 cm H 2 O and continue to decrease FIO 2. (Some consider 4 cm H 2 O to be a minimal CPAP level.) 5. Maintain on a minimal CPAP until extubation to help infant overcome the resistance of the tube. If the patient is stable on a minimal CPAP for 2-4 hours, consider extubation and/or discontinuing the CPAP. Prior to discontinuing the CPAP therapy form the patient, hyperinflate and suction him/her. Increase FIO 2 5 to 10% upon cessation. Obtain a chest X-ray within 2 hours. Postural drainage, percussion, and suctioning should be performed as needed. It is very important to begin weaning CDP/CPAP as the compliance improves. If not, the same CPAP pressure will overdistend the more compliant alveoli. This can result in apnea, CO 2 retention, and a decrease in venous return to the heart, pneumothorax, and an increase in dead space ventilation. COMPLICATIONS As with any form of positive pressure, the risk of barotrauma exists. Patients need to be closely monitored for signs of air leaks such as: pneumothorax, pneumomediastinum, or pulmonary interstitial emphysema (PIE). Most complications of CPAP are a result of an overdistention of the lung parenchyma. Should the lungs be uniformly stiff, there is less chance of overdistention. A stiff lung will absorb the pressure applied to it. However, when the lungs are compliant, the pressure is transmitted to the This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 19

20 pulmonary vascular bed. This results in a decrease in venous return and cardiac output. A compliant lung will be more prone to overdistention, rupture, and decreased blood flow. A B C A. Correct CDP provides adequate alveolar distention. B. Excessive CDP overdistends alveoli. C. When patient improves and surfactant returns the same CDP now overdistends. CPAP can cause a decrease in urine output by decreasing renal blood flow and perfusion pressure. Fluid overload can occur. CPAP will stimulate production of antidiuretic hormone (ADH) and lymph flow in the thorax can also be obstructed. All of the above increase the possibility of pulmonary edema. If excessive CPAP is used, overdistention will occur. If the lung disease is patchy, overdistention will occur in the compliant areas resulting in V/Q mismatching. If CPAP is applied to lungs with no pulmonary disease, as much as 50% of the pressure can be transmitted to the circulatory system. Overdistention also will occur when the patient begins to improve. As compliance increases, CPAP will begin to overdistend the lung. It must be titrated to prevent overdistention. MECHANICAL VENTILATION The goal of mechanical ventilation of the neonate is to maintain an adequate minute volume using a minimum of mechanical force. (In clinical practice, one rarely thinks of volume in neonatal ventilation, but rather in terms of pressure. However, the pressure one is using is merely to exchange a volume of gas in the lung.) The indications for mechanical ventilation are: apnea, hypoventilation, severe hypoxemia, and cardiovascular collapse. Mechanical ventilation This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 20

21 has numerous complications, so less intensive efforts to treat the problem should be attempted first. (For example, attempt respiratory stimulation and CPAP for hypoventilation or CPAP alone for severe hypoxemia prior to mechanical ventilation.) Once ventilation is initiated, one should strive to minimize the amount as much as possible. The lowest frequency, pressure, and time to achieve the desired end should be used. It is essential to remember that within this course when the issues of setting changes are addressed, it s referring to ventilators that are of the pressure limited, timed cycled classification. At the present time, it is possible to use time cycled, volume (flow) limited ventilation in neonates. INDICATIONS Apnea in the neonate can be absolute or periodic. Absolute apnea makes mechanical ventilation obvious because the infant is not breathing. It may not be so obvious with periodic apnea. Periodic apnea is when the apnea comes and goes. These infants require some type of stimulation to break the apneic spell. The more severe the problem, the greater the amount of stimulation needed to initiate breathing. Periodic apnea that requires resuscitation or vigorous stimulation to initiate breathing is an indication for ventilation. Less severe forms of periodic apnea, in an infant with lung disease, are also an indication for ventilation. In these patients, apneic spells increase atelectasis through the process of absorption. In patients without lung disease, adequate amounts of surfactant will help prevent atelectasis. Therefore, apneic spells in patients with lung disease should not be tolerated, even if the patient resumes spontaneous breathing. Rocking beds are not currently considered a good choice for relief of periodic apnea. They consist of placing a test lung hooked to a ventilator under a water mattress. The inflation of the test lung rocks the mattress, which provides stimulation to continue breathing. (Caution is advised in low birth weight infants as this may cause intraventricular hemorrhage.) The amount of hypoventilation that requires mechanical ventilation is somewhat debatable. Most consider a PaCO 2 of 60 mm Hg an indication for mechanical ventilation. Others may let it go higher, if the ph remains above An elevated PaCO 2 associated with a falling ph denotes acute respiratory failure (ARF) and is an indication for ventilation. An elevated PaCO 2 with a normal ph denotes a chronic condition. In this situation, one must weigh the potential risks and benefits of ventilation versus the risks of hypercarbia. (Hypercarbia causes pulmonary vasoconstriction, cerebral vasodilation, and depresses respiration.) Some institutions prefer periodic manual ventilation with a resuscitation bag to lower the PaCO 2 prior to ventilator commitment. If this is insufficient, the patient is placed on a ventilator. Severe hypoxemia, as evidenced by a PaO 2 less than 50 mm Hg or a % saturation less than 90% on 100% O 2, is an indication for ventilation. CPAP should be given a trial first to obtain This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 21

22 acceptable blood gases. If a CPAP greater than 12 cm H 2 O is being used, consider mechanical ventilation. Lastly, cardiovascular collapse or compromise is an indication for ventilation. Mechanical ventilation will decrease the work of breathing in these infants by decreasing oxygen consumption and carbon dioxide production. This will make the job of the heart easier and enhance oxygen delivery to the tissues. MANUAL VENTILATION M echanical ventilation can be accomplished manually via a resuscitation bag and mask. One can use a self-inflating or non self-inflating (flow-inflating) bag. The former is recommended when the practitioner has just occasional contact with neonates and for transport. The latter requires frequent practice for proper use and a constant gas supply to function. Flow-inflatable are preferred in the hospital setting. They can be more precisely adjusted to the needs of the infant than the self-inflating bags. They also provide a feel for the compliance of the infant. Flow-inflatable bags consist of an anesthesia bag with a patient elbow attached. There is an adapter to connect an in-line pressure manometer. A low-flow flowmeter and oxygen blender is used. Flow is set according to minute volume needs, usually between 5 to 10 liters per minute. For emergency resuscitation, 100% O 2 is used. This should then be adjusted based upon ABG results. For other situations, the same FIO 2 that the patient is currently receiving should be used. (Many institutions will increase FIO 2 10% for bagging associated with suctioning.) Either bag should allow the patient to breathe spontaneously while attached and allow connection to a pressure manometer. They should be capable of providing PEEP/CPAP. The selection of a bag should be based upon frequency of use, ease of operation, range of FIO 2 available, gas supply available, pressure monitoring, and availability of PEEP/CPAP. MECHANICAL VENTILATORS M ost ventilation of infants is accomplished with a pressure preset, time-cycled, continuous flow IMV ventilator. A continuous flow of fresh gas flows through the circuit and is periodically interrupted at the exhalation valve. This forces gas into the patient (the path of least resistance) for a preset period. The pressure that builds up in the circuit (and patient) is preset and limited. This pressure is maintained throughout the inspiratory cycle. This gives an inspiratory plateau or square wave type of ventilatory pattern. Volume-preset ventilators are rarely used with infants. However, volume-preset ventilators have been successful when pressure-preset ventilators have failed. Volume-preset ventilators provide a specific volume to the patient s every breath. Peak inspiratory pressure (PIP) will vary This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 22

23 depending upon the resistance and compliance of the patient. (For most infants, one needs precise control of PIP to minimize potential complications, particularly development of BPD.) Infants with severely low compliant lung disease (such as diaphragmatic hernia patients) are candidates for a volume-preset ventilator. Continuous flow systems are generally used so the infant can inhale at any time. Infant respiratory rates are high and demand valve systems have difficulty sensing the infant demand in adequate time to deliver flow. (This is why infants are on IMV instead of SIMV.) Newer microprocessor-controlled ventilators have a much quicker response time and may provide the choice of either a demand flow or continuous-flow. IMPORTANT CONCEPTS The parameters to be adjusted will vary from one ventilator to the next. One must commonly adjust inspiratory and expiratory time, i:e ratio, frequency (respiratory rate), flow rate, pressure limit, pressure popoff, FIO 2, PEEP/CPAP level, and various alarms. (Pressure limit in infant ventilation refers to ventilating pressure. Pressure popoff refers to a pressure relief safety mechanism to allow venting of excess pressure within the system.) One also may have the choice of selecting sensitivity and demand or continuous flow (pressure popoff should be set at 5-7 cm of H 2 O above the PIP to avoid possible pneumothorax). The interplay of inspiratory time, expiratory time, i:e ratio, and frequency must be understood. They interrelate and a change in one parameter will affect the others. If one receives an order to change a single parameter, the practitioner must then determine how to adjust the remaining parameters to maintain the infant. For example, if inspiratory time is set at 1 second, expiratory time at 2 seconds, then i:e ratio is 1:2 and frequency is 20 breaths per minute. (Adding the inspiratory time (sec.) to the expiratory time (sec.) and dividing the result into 60 sec. can easily calculate breathing frequency. In this example, 1 sec. + 2 sec. = 3 sec., 60 sec. divided by 3 sec. = 20 breaths per minute.) If the physician orders the inspiratory time increased to 2 seconds and the other parameters are left at the previous settings, i:e ratio is now 1:1 and frequency is decreased to 15 breaths per minute (60 sec. divided by [2 sec. + 2 sec.] = 15 breaths per minute). This can seriously decrease minute volume. To maintain the frequency of 20 per minute there must be a simultaneous decrease in the expiratory time to one second. However, if this is done, then the i:e ratio is now 2:1 instead of 1:2. The ordering physician must be made aware of this and it must be taken into consideration. One cannot just change a single parameter and expect all the others to remain the same. This takes considerable experience to become familiar with these concepts. The ventilator being used may have controls for any combination of inspiratory time, expiratory time, frequency, or i:e ratio. As long as one understands the relationships between these parameters one can use any given ventilator. This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 23

24 To determine proper inspiratory and expiratory time, one must also understand the concept of time constants. A time constant is the time it takes for proximal airway pressure to equilibrate with distal airway or alveolar pressure. (In other words, the time it takes a lung unit to empty or fill). A time constant is measured in seconds and is the product of airway resistance and pulmonary compliance. Very stiff lungs and no airway disease produce a short time constant. This causes pressure to equilibrate quickly. The opposite is true when there is significant airway disease. Airway disease produces a long time constant for the lung unit(s) they feed. Depending upon the disease process, there may be a different time constant for inspiration and expiration. This will influence how one sets inspiratory and expiratory time. A generic inspiratory time setting is between 0.3 and 0.7 second. (In modern ventilators, once the inspiratory time is set and the rate is changed, the expiratory time is adjusted automatically). Expiratory time will be set to achieve the desired frequency. A disease process that is primarily airway has a long inspiratory time constant. This would indicate a long inspiratory time would be most beneficial. However, the expiratory time constant is even longer than the inspiratory with airway obstruction. (This is due to the passive mechanical dilation of airways on inspiration and slight constriction on expiration.) One must allow enough time for the lungs to empty completely to prevent air trapping. A long expiratory time is therefore advantageous. Ideally, a long inspiratory and long expiratory time are both necessary. (One is limited in doing this because the resulting respiratory frequency may be inadequate to maintain CO 2 levels.) Hyaline membrane disease (HMD) is an example of a disease process with short inspiratory and expiratory time constants. There is relatively little airway disease and stiff lung parenchyma in HMD. Pressure is transmitted rapidly through the airways and the stiff parenchyma equilibrates rapidly with proximal airway pressure. Due to an increase in elastic recoil they also empty rapidly, making atelectasis common. Prolonging expiratory time is necessary to prolong the expiratory time constant to help prevent alveolar collapse. (PEEP is also advantageous in prolonging the expiratory time constant.) As one can readily see, adjustment of a given parameter on infant ventilators is not an isolated event. The practitioner must keep these concepts and their relationships in mind in making parameter adjustments. In an effort to minimize barotrauma from PIP or PEEP, prolonged inspiratory times and inverse i:e ratios have been used. (A normal i:e ratio for mechanical ventilation is greater than or equal to 1:2. Inspiratory times greater than or equal to expiratory time are inverse ratios, such as 2:1, 3:1, etc.) Prolonged inspiratory times provide an inspiratory plateau or square wave pressure pattern. This improves gas exchange and expiratory lung volume similar to PEEP. (However, PEEP provides a greater increase in lung volume per unit increase in mean airway pressure This material is copyrighted by RC Educational Consulting Services, Inc. Unauthorized duplication is prohibited by law. 24