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Respiratory support, oxygen delivery, and oxygen monitoring in the newborn

Respiratory support, oxygen delivery, and oxygen monitoring in the newborn
Authors:
Richard Martin, MD
Kathleen M Deakins, MHSA RRT NPS FAARC
Section Editor:
Leonard E Weisman, MD
Deputy Editor:
Laurie Wilkie, MD, MS
Literature review current through: Apr 2022. | This topic last updated: May 16, 2022.

INTRODUCTION — Oxygen supplementation using noninvasive measures is an important component of intensive care of the newborn. Careful monitoring is required to minimize pulmonary toxicity or the consequences of hypoxemia or hyperoxia.

Noninvasive oxygen administration and monitoring for the neonate, including the preterm infant, will be reviewed here. Oxygen administration during neonatal resuscitation in the delivery room and neonatal mechanical ventilation are discussed separately:

(See "Neonatal resuscitation in the delivery room", section on 'Oxygen concentration'.)

(See "Overview of mechanical ventilation in neonates".)

(See "Approach to mechanical ventilation in very preterm neonates".)

DEFINITIONS — Definitions of different degrees of prematurity based upon gestational age (GA; which is calculated from the first day of the mother's last period) or birth weight (BW) are provided in the table (table 1).

DELIVERY ROOM RESUSCIATATION — Respiratory support and the use of supplemental oxygen and its administration and monitoring during neonatal resuscitation in the delivery room are discussed separately. (See "Neonatal resuscitation in the delivery room".)

RESPIRATORY SUPPORT DEVICES — Respiratory support systems used in neonates include:

Low-flow nasal cannula (LFNC)

High-flow nasal cannula (HFNC)

Hood

Face mask

Nasal continuous positive airway pressure (nCPAP)

Nasal intermittent positive pressure ventilation (NIPPV)

Endotracheal intubation and invasive mechanical ventilation (MV)

These respiratory support devices provide warmed and humidified gas that is delivered using a system in which the oxygen concentration can be regulated. Individualized assessment and frequent reassessment of the adequacy of oxygenation is required (see 'Measurement of oxygenation' below). The inspired oxygen concentration (FiO2) should be monitored with an oxygen analyzer, if possible.

The following sections describe the various respiratory support and oxygen delivery devices commonly used in neonates.

Choice of modality — The choice of respiratory and oxygen delivery device is dependent on the clinical setting and the needs of the individual neonate.

In our center, we base the choice on the gestational age (GA) of the neonate, the underlying respiratory condition, and the phase of illness (ie, initial support versus following extubation). Our general approach is as follows:

Very preterm infants (VPT; GA <32 weeks) – For VPT infants who are at risk for respiratory distress syndrome (RDS), nCPAP is our preferred initial primary respiratory support, as discussed separately. (See "Management of respiratory distress syndrome in preterm infants", section on 'Noninvasive positive airway pressure'.)

Moderate preterm infants (GA 32 to <34 weeks) – For moderate preterm infants, the initial respiratory support depends upon the degree of respiratory distress. For infants who display respiratory distress (tachypnea, grunting, nasal flaring), nCPAP is the preferred respiratory support system as these infants may be at risk for RDS. For infants with hypoxemia without respiratory distress, LFNC is usually sufficient.

Late preterm and term infants (GA >34 weeks) – For late preterm and term infants, the modality depends upon the underlying diagnosis. Positive pressure typically is not necessary unless there is considerable intrinsic lung disease.

Transient tachypnea of the newborn ‒ In this setting, oxygen supplementation is provided by hood or LFNC to maintain oxygen saturation >90 percent. (See "Transient tachypnea of the newborn".)

Neonatal pneumonia ‒ Oxygen supplementation is initially provided by hood or LFNC to maintain oxygen saturation >90 percent.

Cyanotic heart disease – Choice of respiratory support is dependent on the clinical setting based on the infant's respiratory status and oxygen saturation. (See "Diagnosis and initial management of cyanotic heart disease in the newborn", section on 'General supportive care'.)

Persistent pulmonary hypertension of the newborn (PPHN) – The respiratory support for PPHN depends on the infant's respiratory status and oxygen saturation, as discussed separately. (See "Persistent pulmonary hypertension of the newborn".)

Following extubation – We typically use nCPAP when managing infants who have been intubated and mechanically ventilated for a period of time and who are at risk for requiring reintubation following extubation. We prefer nCPAP over HFNC and NIPPV because there is greater experience and familiarity with this modality, particularly in VPT infants. The available data suggest that all three modalities are effective in preventing reintubation. These data are discussed separately. (See "Management of respiratory distress syndrome in preterm infants", section on 'Post-extubation support'.)

For preterm infants with advancing age who continue to require supplemental oxygen following extubation and who poorly tolerate the CPAP nasal prongs, HFNC or LFNC are reasonable alternative methods for oxygen delivery [1]. (See 'Low-flow nasal cannula' below.)

Low-flow nasal cannula — LFNC provides oxygen through two soft prongs that are inserted into the patient's anterior nares (picture 1). Oxygen flows from the cannula into the patient's nasopharynx and mixes with room air entering from the infant's mouth and nose. Consequently, there is considerable variability is the effective FiO2 delivered to the lungs with LFNC due to variability in respiratory rate, oxygen flow rate, extent of mouth breathing, and size of the nasopharynx [2].

In neonates, LFNC is typically provided with unblended oxygen at flow rates <1 L/min, which provides no or minimal positive pressure (<1 cm H2O). Alternatively, LFNC can be used with a blender to administer a lower oxygen concentration (FiO2 0.25 to 0.4) at a higher flow rate (1 to 2 L/min). The effective oxygen concentration the lungs receive will be lower than the FiO2 setting on the air/oxygen blender. In preterm infants, the latter approach is commonly used when transitioning from nCPAP to LFNC. The benefit of this approach is that it provides a small amount of positive airway pressure (approximately 1 to 3 cm H2O) without exposing the neonate to high oxygen concentrations [3].

There are established formulas to estimate the effective delivered FiO2 based upon patient size, oxygen concentration, and flow rate [4]. However, these formulas are rarely used in clinical practice because they are cumbersome and they provide only a rough estimate. It is simpler to just assume that the effective FiO2 delivered by LFNC is lower than prescribed and, in some cases, almost equivalent to room air [5].

Other oxygen delivery systems

Hood — An oxygen hood is a high-flow, high-concentration oxygen system (7 to 15 L/min) that uses a hard plastic or soft tent-like structure or dome that fits over the infant's head (if in an incubator) or over the body (if in a crib) (picture 2). Hoods are not routinely used for oxygen delivery in neonates, since they limit access to the infant's face and head. They are generally used only in settings when a cannula is not tolerated.

Oxygen enters the hood through a gas inlet. Oxygen concentrations of 80 to 90 percent can be achieved with oxygen flow rates ≥10 to 15 L/min. Exhaled gas exits through the opening at the neck [6]. A pass-over system is used to humidify the oxygen to prevent drying of the skin and inspired gas. In preterm neonates <1500 g, the oxygen is heated to the same temperature as the incubator. In larger infants, room temperature is maintained within the hood to prevent tachypnea.

Face mask — A face mask used for oxygen delivery is rarely used beyond the delivery room resuscitation. However, a mask is occasionally used to deliver free-flow oxygen as a temporary measure during periods of oxygen desaturation or prior to endotracheal intubation. The distance of the mask from the face affects the delivered FiO2 . If a mask is employed for the resolution of apnea, every effort would be made to mirror the FiO2 that is used prior to the episode.

Servo-control incubator — Stable oxygen concentration can be achieved in a servo-controlled incubator. In preterm infants receiving supplemental oxygen, a small single-center trial reported episodes of hypoxemia were lower when using a servo-controlled environment compared with the use of a nasal cannulae to deliver [7].

High-flow nasal cannula — HFNC delivers heated, humidified air at flow rates that are higher than standard LFNC. The flow rate and FiO2 are set by the clinician. Typical initial flow rates for neonates are 4 to 6 L/min up to maximum of 8 L/min. At these flow rates, the amount of positive airway pressure provided by HFNC ranges from 2 to 5 cm H2O [3].

HFNC may be used as an alternative to nCPAP in the following settings [1,8,9]:

Apnea of prematurity (see "Management of apnea of prematurity", section on 'High flow nasal cannula')

Primary mode of respiratory support in preterm infants with RDS (see "Management of respiratory distress syndrome in preterm infants", section on 'High-flow nasal cannulae')

Following extubation (see "Management of respiratory distress syndrome in preterm infants", section on 'Post-extubation support')

The theoretical benefit of HFNC is that the high flow rate washes out nasopharyngeal dead space and replaces the end-expiratory gas within the upper airway with fresh oxygenated and humidified gas [10]. In addition, the nasal cannulae used for HFNC are smaller than the nasal prongs used for nCPAP and they are easier to apply and associated with less nasal trauma [11]. However, there is greater variability in the amount of positive airway pressure provided with HFNC compared with nCPAP [12]. For this reason, and because there is greater experience with nCPAP, many centers, including our own, preferentially use nCPAP for initial management of VPT infants. HFNC is a reasonable alternative for neonates who do not tolerate nCPAP and those who develop problematic nasal trauma on nCPAP. These issues are discussed in greater detail separately. (See "Management of respiratory distress syndrome in preterm infants", section on 'Noninvasive positive airway pressure'.)

HFNC can also be used to provide apneic oxygenation during endotracheal intubation in non-emergency situations (ie, when time and resources allow for setting up the HFNC system). The aim of HFNC use in this setting is to maintain cardiorespiratory stability during the procedure and allow more time for successful intubation. In a trial involving 209 preterm neonates undergoing 258 non-emergency intubations (most patients were on CPAP prior to intubation), HFNC use throughout the procedure improved the likelihood of successful first-attempt intubation compared with no supplemental oxygen (68 versus 54 percent; adjusted risk difference [aRD] 15.8, 95% CI 4.3–27.3) [13]. In addition, episodes of desaturation and/or bradycardia occurred less commonly in the HFNC group (36 versus 50 percent; aRD 13.4, 95% CI 1.3-25.5). The practice of using HFNC (or other devices) for apneic oxygenation during neonatal and pediatric intubation is discussed in greater detail separately. (See "Management of the difficult airway for pediatric anesthesia", section on 'Apneic oxygenation'.)

Each HFNC system requires a specific humidification device and cannula that are not interchangeable between systems. Adequate heating and humidification is necessary for each HFNC system [8]. HFNC prongs are smaller in length and diameter than those used for nCPAP and do not require a seal to operate. HFNC prongs should occupy no more than 50 percent of the internal diameter of the nares to permit sufficient leak and protection from high pressure [8,14]. The cannulae should not occlude the nares since this can generate high nasopharyngeal pressure and can potentially cause traumatic air dissection [8,10].

Additional details regarding HFNC are provided separately. (See "High-flow nasal cannula oxygen therapy in children".)

Continuous positive airway pressure

Clinical application — nCPAP is our preferred modality for initial respiratory support in preterm neonates with RDS or apnea. It is also commonly used for respiratory support following extubation. nCPAP is thought to be effective by splinting the pharyngeal airway with positive pressure, thereby maintaining lung recruitment and reducing the risk of upper airway collapse and obstruction (picture 3).

Use of nCPAP in these clinical settings is discussed in detail separately:

Initial respiratory support for VPT neonates (see "Management of respiratory distress syndrome in preterm infants", section on 'Nasal continuous positive airway pressure (nCPAP)' and "Bronchopulmonary dysplasia: Prevention", section on 'Ventilation strategies to minimize lung injury')

Management of apnea of prematurity (see "Management of apnea of prematurity", section on 'Nasal continuous positive airway pressure')

Postextubation respiratory support (see "Management of respiratory distress syndrome in preterm infants", section on 'Post-extubation support')

CPAP systems — CPAP is administered through nasal prongs or mask through a variety of systems (picture 3).

CPAP can be delivered using different systems, which are broadly categorized as fluidic (variable flow) CPAP, constant flow CPAP, and bubble CPAP. In our center, we use the fluidic (variable flow) system because it allows rapid transition from inspiration to expiration and this may reduce work of breathing, especially in smaller infants.

Fluidic CPAP, also known as variable flow CPAP, uses two individual flow paths, one each for inspiration and expiration. An inlet port supplies fresh gas flow that enters one of the two separate flow paths, converts energy to pressure, and delivers constant pressure through nasal prongs or a mask to the airway. On exhalation, gas exits the system though an exhaust tubing (opposing path) that imposes little to no resistance, making exhalation easy. Because of the availability of the two individual flow paths, transition between inspiratory and expiratory phases occurs quickly and reduces the work of breathing, especially in VPT infants (GA ≤32 weeks) [15].

Constant flow systems use a standard nasal prong or mask interface attached to a standard ventilator circuit. The level of CPAP is controlled by the ventilator settings and the bias flow (the amount of flow left in the circuit during exhalation). Advanced ventilator technology incorporates algorithms that respond to the patient's need or demand for flow. In some cases, if the patient needs higher flow because they are "flow starved," such as in neonates with respiratory distress; the demand valve of the ventilator opens and allows for higher flows to achieve the desired CPAP. Most ventilators deliver constant pressure to achieve CPAP. However, in low birth weight (BW) infants, minimum or smaller respiratory efforts in very low birth weight (VLBW) infants are sometimes not recognized by the ventilator, making it less responsive to their needs, and thus making this system less favorable.

Bubble CPAP is a constant-flow variable pressure system that incorporates a standard nasal prong or mask interface attached to a dual-limb heated and humidified circuit. It is the least expensive system, is commonly used in level 2 and 3 neonatal care units, and is easy to initiate in the delivery room. Inspiratory flow is provided from a blended gas source while the expiratory side of the circuit is submersed into a water column. These low flows prevent buildup of back pressure in the system, making it a safe application for neonates. The desired level of CPAP in cm H20 is determined by not only the depth of the tubing within the water column but also the amount of flow powering the system. Continuous bubbling requires a base flow rate of 4 to 8 L per minute depending on the type of system used. Bubble CPAP systems' characteristics vary, so careful attention to both the depth and the flow are important factors to consider. CPAP pressure is measured with a pressure manometer to determine the actual pressure delivered. Gas flow is responsible for bubbling in the circuit and produces mini oscillations generated within the chest that can equate to nearly 5 to 20 Hz at average CPAP levels [15].

Initial settings — In our center, we administer nCPAP with an initial pressure level of 5 cm H20 and then increase to 6 to 8 cm H20 as needed. In select cases, infants may benefit from higher pressures up to 10 to 11 cm, which is affected by the amount of leak around the nasal prongs and patient-specific factors, including lung compliance and impaired hypopharyngeal function.

Nasal intermittent positive pressure ventilation — NIPPV provides noninvasive respiratory support with phasic positive pressure ventilation (ie, higher pressure during inspiration, lower pressure during exhalation). It is delivered via nasal prongs or mask using a mechanical ventilator [10,16]. The peak inspiratory pressure, expiratory pressure, and breath rate are set by the clinician. Breaths are time-cycled and pressure- or flow-limited; the size of the breath is determined by the difference between the inspiratory and expiratory pressures. Clinical trials evaluating NIPPV in neonates have used a wide range of set peak inspiratory pressures (10 to 25 cm H2O), breath rates (10 to 60 breaths per minute), and inspiratory times (0.3 to 0.5 seconds) [10].

As with invasive MV, NIPPV can be delivered either as synchronized or nonsynchronized breaths. However, synchronization is difficult to achieve in with noninvasive ventilation in neonates [17], and there are few devices that are approved by the US Food and Drug Administration (FDA)-approved for delivery of synchronized NIPPV in neonates. As a result, NIPPV is generally used in a nonsynchronized mode.

NIPPV has been used clinically in the following settings [10,16,18]:

Apnea of prematurity (see "Management of apnea of prematurity", section on 'Nasal intermittent positive pressure ventilation')

Primary mode of respiratory support in preterm infants with RDS (see "Management of respiratory distress syndrome in preterm infants", section on 'Nasal intermittent positive pressure ventilation')

Following extubation (see "Management of respiratory distress syndrome in preterm infants", section on 'Post-extubation support')

Compared with nCPAP, NIPPV is more costly and complex to use because it requires a ventilator for administration. For this reason, many centers, including our own, preferentially use nCPAP for initial management of VPT infants. However, NIPPV is a reasonable option for neonates who fail nCPAP.

Another disadvantage of NIPPV is that because it delivers breaths through a smaller interface (nasal prongs) than with invasive MV, it generally requires a higher flow rate. Inadequate flow will not overcome the back pressure in the ventilator system and can result in insufficient pressure being delivered to the infant such that there may be little to no tidal volume. This can occur despite the ventilator indicating adequate measured pressure on the display.

Abdominal distention has been observed in patients managed by NIPPV but the rate of necrotizing enterocolitis (NEC) appears to be similar to that in patients receiving nCPAP. It remains uncertain whether NIPPV is associated with increased risk of nasal septum injury compared with nCPAP.

Intubation and mechanical ventilation — Invasive mechanical ventilation is discussed separately. (See "Overview of mechanical ventilation in neonates" and "Approach to mechanical ventilation in very preterm neonates".)

Other modalities — Other respiratory support systems are not commonly used in neonates:

Noninvasive high-frequency oscillatory ventilation (nHFOV) ‒ nHFOV applies an oscillatory pressure waveform to the airways using a nasal interface. It has been used in some centers for management of preterm neonates who fail nCPAP [19].There are few data comparing nHFOV with other more standard respiratory support modalities (eg, nCPAP) [20-22]. In a meta-analysis of four randomized trials involving 570 neonates most of whom had moderate to severe RDS, intubation rates were lower in neonates assigned to nHFOV compared with nCPAP (relative risk [RR] 0.44, 95% CI 0.29-0.67) [21]. However, the trials had important limitations including incomplete follow-up and high rates of crossover to the other treatment modality.

nHFOV is more costly than other more standard respiratory support modalities. As a result, we suggest not using nHFOV outside the research setting until further clinical trials clearly demonstrate that it is safe and more effective (and more cost-effective) compared with conventional modes of oxygen delivery and respiratory support.

Bilevel nasal CPAP – Bilevel nCPAP systems provide sigh breaths with much lower pressures, longer inflation times (0.5 to 1.0 second for the higher nCPAP pressure), and lower cycle rates (10 to 30 breaths per minute) than NIPPV [10]. As a result, there are small differences (<4 cm H2O) between the two alternating levels of CPAP pressures. However, data are insufficient to determine whether bilevel nCPAP provides any further advantage over standard CPAP for respiratory support in neonates [10]. As a result, we prefer standard nCPAP as the initial modality for respiratory support until there are data that show the additional benefit of bilevel nCPAP over standard nCPAP.

Noninvasive neurally adjusted ventilatory assist (NIV-NAVA) – NIV-NAVA is similar to synchronized NIPPV [23,24]. However, breath delivery is triggered by a signal from the electrical activity of the diaphragm rather than flow sensing on the ventilator. As such, NAVA is not affected by leaks around the interface and the delivered breaths more closely match the infant’s spontaneous effort. NIV-NAVA has been used in practice in attempt to reduce the need for intubation and mechanical ventilation. However, it is unclear based on limited data whether there are short-term clinically beneficial effects [25,26]. In a randomized trial comparing NIV-NAVA to standard ventilation for management of neonatal RDS, lower peak inspiratory pressure (PIP) were delivered by NIV-NAVA, but outcomes were similar between the two groups regarding duration of ventilation, mortality, and the risk of BPD, intraventricular hemorrhage, and pneumothorax [27].

Further research in larger trials is needed to determine in which clinical settings NIV-NAVA is safe and cost-effective, and whether it can be used beyond the research setting [10].

MEASUREMENT OF OXYGENATION — Oxygenation should be monitored in any neonate who receives supplemental oxygen therapy to prevent episodes of hypoxemia and hyperoxia, and to avoid the use of excessive supplemental oxygen and periods of profound hypoxia, which are associated with mortality and morbidity. In preterm infants, high concentrations of supplemental oxygen are associated with increased risk of bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP). Although the level of oxygenation can be assessed in several ways, pulse oximetry, which measures hemoglobin saturation (SpO2), is the accepted standard for routine monitoring of oxygenation. (See "Retinopathy of prematurity: Pathogenesis, epidemiology, classification, and screening", section on 'Pathogenesis' and "Retinopathy of prematurity: Pathogenesis, epidemiology, classification, and screening", section on 'Risk factors' and "Bronchopulmonary dysplasia: Definition, pathogenesis, and clinical features", section on 'Oxygen toxicity'.)

Pulse oximetry — Pulse oximetry measures SpO2 and reflects the 98 percent of arterial oxygen content that is carried normally by hemoglobin. This monitoring technique provides data that are continuous and noninvasive, and, therefore, avoids some limitations of intermittent arterial blood sampling. As a result, in most neonatal intensive care units (NICUs), pulse oximetry is the accepted standard for routine monitoring, and SpO2 has been called the "fifth vital sign" [28]. (See "Pulse oximetry".)

It should be noted that pulse oximeters provide time-measure values over several heart beats and do not give out instantaneous readings. Longer averaging times provide a more stable assessment with fewer alarms but are less sensitive to brief episodes of changes in oxygen saturation [10]. (See "Neonatal target oxygen levels for preterm infants", section on 'Use of SpO2 for targeting oxygen levels'.)

It is important to determine the target pulse oximetry saturation range that adequately meets metabolic demands of the neonate, yet limits the need for high concentrations of supplemental oxygen that might cause lung injury or retinopathy of prematurity (ROP). Normal pulse oximetry values in healthy term infants average 97 percent on room air [29,30] and 95 percent in healthy preterm infants [31]. Attempts to maintain SpO2 values greater than 95 percent using supplemental oxygen may result in excess oxygen exposure and hyperoxia. Determination of SpO2 target levels is discussed separately. (See "Neonatal target oxygen levels for preterm infants", section on 'Oxygen target levels'.)

Most NICUs establish guidelines for target pulse oximetry saturation levels. However, it is challenging to maintain these targets, as SpO2 values fluctuate in unstable neonates and are often outside the intended targeted range. Additional measures, including increased surveillance and heightened awareness by medical personnel at the bedside, may be helpful to reduce the time periods of either too low or too high oxygen saturation [32]. (See "Neonatal target oxygen levels for preterm infants", section on 'Adherence to oxygen target goals'.)

Sources of error — Pulse oximetry is easy to use and does not require calibration. However, interpretation of pulse oximetry readings must account for a variety of technical and clinical factors that may artificially influence the results. The best defense against these potential sources of error is a high level of training regarding the function of the pulse oximeter.

Choice of oximeter ‒ Variation in the design of the monitor may result in differences of 2 to 3 percent among various instruments. In particular, different algorithms are used to derive SpO2, correct for minor hemoglobin variants, or to exclude motion artifact [33]. In addition, algorithms vary on the averaging time for waveform analysis, which may affect the rate and detection of desaturation events [34]. As a result, short events that are in close proximity may be displayed as a single longer event, which may impact clinical decision making. Therefore, some pulse oximeters may not be suitable for neonatal use.

Technical sources of error at the point of care include [33]:

Motion artifact – Low amplitude arterial pulsations in small preterm infants are particularly difficult for oximeters to detect and differentiate from venous pulsations and other movement artifacts. As a result, examination of the displayed waveform is recommended to validate the oximeter signal. An alternate check is comparison of the pulse rate from the oximeter with the heart rate from the electrocardiograph monitor; the two values should be identical.

Improper probe placement.

Exposure to ambient light can be minimized by shielding of the probe.

Clinical factors that contribute to error include:

Hypoperfusion – Pulse oximetry readings can be falsely low because of signal failure in the setting of hemodynamic instability or poor limb perfusion caused by vasoconstriction. Placement of a blood pressure cuff and oximeter probe on the same extremity should be avoided.

Abnormal hemoglobins and severe anemia – Abnormal hemoglobins or hemoglobin variants can interfere with pulse oximetry if their absorption properties are similar to those of oxyhemoglobin or deoxyhemoglobin. Fetal hemoglobin does not interfere with oximetry measurements unless levels exceed 50 percent [35]. Although pulse oximetry values are falsely lowered only when anemia is very severe, clinicians must be aware that low hemoglobin concentrations decrease oxygen content and delivery. (See "Hemoglobin variants that alter hemoglobin-oxygen affinity".)

Occurrence of short, deep desaturation events that trigger audible alarms are common during oximetry monitoring of preterm infants. These frequent events may produce "alarm overload" among bedside care providers and further contribute to the difficulties of maintaining target saturations in a narrowly defined range. To reduce the impact of these "nuisance alarms," manufacturers have employed increasingly sophisticated waveform analysis and algorithms that may include longer averaging time. Different averaging times used in conjunction with variable adjustments of alarm delay (which are manufacturer dependent) may influence the duration of desaturation events and the response of care providers. There is no standard for clinical practice; however, uniform policy within a NICU is desirable.

Arterial blood gas measurement — Arterial oxygen tension (PaO2) measures the partial pressure of the small amount of oxygen that is dissolved in plasma, and has been considered the "gold standard" for the measurement of oxygenation. The PaO2, along with the accompanying measurements of partial pressure of carbon dioxide (PaCO2) and pH, are used to evaluate effective pulmonary gas exchange. However, intermittent sampling of arterial blood may not accurately reflect the fluctuations in oxygenation that typically occur in infants with cardiopulmonary disease or in response to percutaneous puncture. Although PaO2 measurements can be used to estimate oxyhemoglobin saturation, changes in pH, temperature, or other factors may render this estimate unreliable. Capillary samples do not provide reliable measurements of PaO2. (See "Arterial blood gases" and "Measures of oxygenation and mechanisms of hypoxemia".)

Specimen collection — Arterial blood usually can be obtained by percutaneous needle puncture of a palpable radial artery. The brachial and femoral arteries should be avoided, if possible. Percutaneous puncture frequently causes agitation, and the resultant PaO2 measurement may be lower than in steady state conditions.

Catheterization of the arterial system can be performed when frequent arterial blood gases are required. Sampling from a catheter also avoids the agitation associated with percutaneous puncture. Preferred locations in newborns are the umbilical or radial arteries; an alternate site is the dorsalis pedis. Common clinical settings in which an indwelling arterial catheter is useful include patients with tenuous gas exchange (eg, severe respiratory distress syndrome or persistent pulmonary hypertension) or shock.

Sources of error — The results of arterial blood gases (PaO2 and PaCO2) can be affected by:

Air bubbles occupying more than 1 to 2 percent of the blood volume in the syringe may introduce error, leading to an artificially high arterial PaO2 and an underestimation of the true arterial PaCO2 [36,37]. The error can be decreased by gentle removal of bubbles without agitation and by rapid sample analysis.

Heparin as an anticoagulant as the dilutional effect of the heparin solution can produce significant reductions in PaCO2, depending directly on the amount of heparin solution relative to the amount of blood [38]. Thus, the amount of heparin solution should be kept to a minimum, or syringes prepared with dry heparin should be used.

Plastic syringes can lead to gas diffusion, which may introduce error. This error generally is not significant if the sample is analyzed within 15 minutes and the specimen is placed on ice [37].

Transcutaneous oxygen monitoring — Transcutaneous oxygen monitors measure oxygen tension (TcPO2) with a heated blood gas electrode applied to the skin surface. However, the need for frequent recalibration and transient erythema from application of the heated electrode have greatly diminished its use.

SUMMARY AND RECOMMENDATIONS

Respiratory support devices – Respiratory support devices provide warmed and humidified gas that is delivered using a system in which the oxygen concentration can be regulated. Respiratory support systems used in neonates include (see 'Respiratory support devices' above):

Low-flow nasal cannula (LFNC) (see 'Low-flow nasal cannula' above)

High-flow nasal cannula (HFNC) (see 'High-flow nasal cannula' above)

Hood (see 'Hood' above)

Face mask (see 'Face mask' above)

Nasal continuous positive airway pressure (nCPAP) (see 'Continuous positive airway pressure' above)

Nasal intermittent positive pressure ventilation (NIPPV) (see 'Nasal intermittent positive pressure ventilation' above)

Endotracheal intubation and invasive mechanical ventilation (MV) (see "Overview of mechanical ventilation in neonates" and "Approach to mechanical ventilation in very preterm neonates")

Choice of modality – The choice of respiratory device is dependent on the clinical setting and the needs of the individual neonate. (See 'Choice of modality' above.)

Measuring and monitoring oxygenation

Neonates receiving supplemental oxygen should have routine monitoring of oxygenation to prevent episodes of hypoxemia and hyperoxia and to avoid the use of excessive supplemental oxygen. In preterm infants, high concentrations of supplemental oxygen are associated with increased risk of bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP). (See "Retinopathy of prematurity: Pathogenesis, epidemiology, classification, and screening", section on 'Pathogenesis' and "Retinopathy of prematurity: Pathogenesis, epidemiology, classification, and screening", section on 'Risk factors' and "Bronchopulmonary dysplasia: Definition, pathogenesis, and clinical features", section on 'Oxygen toxicity'.)

Oxygenation is generally monitored by pulse oximetry supplemented by intermittent arterial blood gas measurement. (See 'Pulse oximetry' above and 'Arterial blood gas measurement' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges James Adams, Jr, MD, who contributed to an earlier version of this topic review.

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