AARC Clinical Practice Guideline

Infant/Toddler Pulmonary Function Tests—2008 Revision & Update

ITPFT 1.0 PROCEDURE: 2.4.3 Tidal measures: RR; time Infant/toddler pulmonary function tests (ITPFTs) to reach peak tidal expiratory flow (tPTEF); 41, total expiratory time (tE); ratio of tPTEF/tE ITPFT 2.0 DESCRIPTION/DEFINITION: 42 2.4.4 Partial expiratory flow-volume 2.1 Infant/toddler pulmonary function tests curves: maximal flow at functional residual measure a variety of pulmonary variables in capacity (VmaxFRC) 49, 68 subjects who are generally too young to per- 2.4.5 Raised volume rapid thoracoabdomi- form, comprehend, or comply with necessary nal compression technique: forced vital ca- instructions for conventional pulmonary diag- pacity (FVC); forced expired volume at 0.5 nostic procedures and 0.75 seconds respectively (FEV0.5, 2.2 Subjects are typically tested under con- FEV0.75); forced expiratory flow at 25%, scious sedation or while sleeping and are spon- 50%, 75% and between 25% and 75% of taneously breathing. ITPFTs have also been FVC (FEF25, FEF50, FEF75, FEF25-75) performed in subjects who are mechanically 68, 73 ventilated. 2.4.6 Whole body plethysmography: 2.3 ITPFTs may include measurements of: plethysmographic functional residual ca- 2.3.1 Passive respiratory mechanics, 1-35 pacity (FRCpleth); 2.3.2 Dynamic respiratory mechanics, 32, 33, (Raw) 97, 101 35-39 2.4.7 Gas dilution techniques: helium dilu- 2.3.3 Tidal breathing measurements, 1, 35, 40 -42 tion (FRCHe), nitrogen washout (FRCN2), 2.3.4 Partial expiratory flow-volume breath-by-breath inert gas washout or mul- curves, 2-7, 9, 12-14, 17, 35, 43-68 tiple breath washout (MBW) techniques 2.3.5 Raised volume rapid thoracoabdomi- measure clearance index (LCI) or nal compression technique, 12, 24, 35, 52-59, 68-89 mixing ratios (MR) 105, 109 2.3.6 Whole-body plethysmography, 9, 32, 35, 2.4.8 Forced deflation: FVC, maximum ex- 64, 84, 85, 90-101 piratory flows at 25 and 10% of FVC 2.3.7 Gas dilution techniques, 7, 10, 11, 14, 20, 26- (MEF25, MEF10) 111 29, 35, 43, 51, 90-92, 95, 99,100, 102-109 and 2.5 Although these procedures are intended pri- 2.3.8 Forced deflation technique in intubat- marily for neonates and infants, some older ed subjects. 110, 111 subjects may be successfully evaluated, if ap- 2.4 Common indices measured using these var- propriately sized equipment is employed and ious techniques includes: methodology limitations are well understood. 2.4.1 Passive respiratory mechanics: total 2.6 The maneuvers used during the raised vol- compliance (Crs); total ume technique are being used to acquire motion respiratory system resistance (Rrs); and free images during chest CT at end inspiration time constant (Trs) 8, 33, 34 and end in infants and children. 112 2.4.2 Dynamic respiratory mechanics: lung 2.7 Investigational techniques in infants such as compliance (CL); lung resistance (RL); res- forced oscillation and interrupter resistance piratory rate (RR), and 33, 38 have been described. 113-117 Consensus regard-

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ing methodology for these techniques is not ITPFT 5.0 CONTRAINDICATIONS: available for infants; therefore, the techniques are It is absolutely critical that prior to initiating briefly described in section 8 of this document. ITPFTs the technologist and physician carefully 2.8 Hardware Considerations: evaluates the patient. Clinical judgment and/or cau- 2.8.1 Size appropriate measurement de- tion should be exercised due to the need for seda- vices, such as pneumotachometers tion and invasiveness of some of these techniques. with appropriate flow range are critical. 118 5.1. Absolute Contraindications (based on the 2.8.2 When setting up equipment, one recommendations of the writing committee): should use tubing sizes and connections 5.1.1 Active pulmonary bleeding, that create the minimum possible mechani- 5.1.2 Open chest wound, cal deadspace. It is important to remember 5.1.3 Untreated or tension pneumothorax, that modifying connections near pneumota- 5.1.4 Past history of intolerance to sedation, chometers or flowmeters may adversely af- 5.1.5 Significant upper airway obstruction, fect measurement accuracy. 118 5.1.6 Seizure disorder (if performing the raised volume technique; the multiple in- ITPFT 3.0 SETTING: flations may lead to a drop in carbon diox- 3.1. Testing may be performed, in a variety of ide levels, thus a drop in seizure threshold), settings including, but not limited to: hospital 5.1.7 Hemodynamically significant con- laboratories, intensive and intermediate care genital heart disease, units, and specialized clinics. It is critical to note 5.1.8 If patient has not remained without that the infants are often undergoing conscious food and/or drink based on the conscious sedation and must be appropriately monitored in sedation policy of the individual institution, the specific setting. When performing these 5.1.9 Naso-facial deformities that prevent tests, the top priority is the safety of the infant effective mask seal or increase risk of gas- and toddler. 118, 119 Please see sections 10 and 11 tric insufflation. for details regarding monitoring and personnel. 5.2 Relative Contraindications (based on the recommendations of the writing committee): ITPFT 4.0 INDICATIONS: 5.2.1 Medical conditions that could com- Indications for ITPFTs include the following: promise patient’s condition if ventilatory 4.1 To serve as an outcome measure in epidemi- support is temporarily interrupted when 1, 2, 3, 12, 17, 32, 47, 48, 50, 58, 63, 71, 75, 76, performing ITPFTs, ologic research 5.2.2 79, 93, 120 Central hypoventilation, 5.2.3 Pre-existing central nervous system 4.2 To improve one’s understanding of the natu- depression or neurologic impairment such ral history of lung growth, or diseases present- as hydrocephalus, ing in infancy (e.g., cystic fibrosis, bronchopul- 5.2.4. Severe gastroesophageal reflux, monary dysplasia, wheezing illnesses) 4, 9, 10, 11, esophagitis or gastritis, 13, 14, 15, 20, 21, 23, 25, 26, 31, 36, 40, 43, 44, 46, 51, 55, 56, 59, 65, 69, 5.2.5 Uncooperative or combative patient, 70, 74, 77, 83, 88, 89, 90, 92, 94, 99, 102, 108, 120 5.2.6 Patients with pacemakers (Thora- 4.3 To evaluate therapeutic responses (e.g., to coabdominal compression technique medication or respiratory interventions) 5, 6, 7, 27, (Hugs) may lead to possible dislodging of 28, 29, 30, 52, 61, 86,120 wires), 5.2.7 Febrile patients, or a recent history 4.4 To help in predicting the risk of subsequent URI, pneumonia or excessive coughing. pulmonary dysfunction based upon initial test- 63, 67, 70, 120 ing. ITPFT 6.0 PRECAUTIONS/HAZARDS 4.5 To provide physiologic measures of lung AND/OR COMPLICATIONS: function in a variety of diseases 4, 9, 10, 11, 13, 14, 15, 20, 25, 31, 36, 40, 43, 46, 50, 51, 52, 55, 65, 69, 70, 78, 85, 88, 89, 90, 91, Due to the need for sedation and the potential inva-

92, 94, 108, 120 siveness of the procedure, the technician performing

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the technique should be an expert in airway manage- the complexity of both performing and interpreting ment and monitoring of infants and toddlers. Al- the data. The ATS/ERS Working Group of Infant though ITPFTs are generally safe procedures, the Lung Function Testing has published guidelines to following untoward events may occur: 121-123 standardized performance and interpretation of 6.1 Vomiting with aspiration with consequent ITPFT results. 7.1 and laryngospasm and/or bronchospasm Methodology and limitations for ITPFT (The forced deflation technique requires tra- techniques are: 7.1.1 Raised volume rapid cheal intubation), 111 thoracoabdominal compression technique 6.2 Pneumothorax, (RVRTC). 6.3 Loss of airway patency leading to increased 7.1.1.1 RVRTC Methodology: 35, 68, 73 121-123 upper airway obstruction (due to sedation), 7.1.1.1.1 Inflatable jacket is 6.4 Transmission of contagion via improperly wrapped around the thorax of the cleaned equipment or as a consequence of the sedated, supine infant. There inadvertent spread of droplet nuclei or body flu- should be a minimum of 3 finger ids (patient-to-patient or patient-to-technolo- breadths between the infant and the gist) Infection control is critical (see section jacket to prevent restriction of lung 13), 124-126 volumes. If the jacket is too tight, 6.5 Oxygen desaturation due to (a) worsening there is a restriction of lung vol- umes. If the jacket is too loose, of ventilation-to- mismatch and hy- there is a delay in the initiation of poventilation as a consequence of sedation the “hug.” 73 121-123 and/or positioning; (b) interruption of 7.1.1.1.2 A clear facemask secured oxygen therapy or failure to preoxygenate the to the face with therapeutic putty is patient prior to performing the forced deflation attached to a circuit containing a technique; (c) temporary loss of distending pneumotachograph, and placed pressure; around the infant’s nose and 6.6 Bradycardia secondary to the sedation, mouth. 35, 68, 73 122,123 7.1.1.1.3 The infant’s lung volume 6.7 Cough, is increased to an airway pressure 6.8 Hypocapnia or dizziness (during the raised of 30 cm H2O (V30) using a pop- off in the circuit attached to the volume technique), 121 facemask. 35, 68, 73 6.9 Paradoxical excitement from the chloral hy- 7.1.1.1.4 Cricoid pressure could be 121 drate (common sedative used), applied during the inflation maneu- 6.10 Gastrointestinal side effects such as nau- ver to limit gas entry into the stom- sea, vomiting, diarrhea from chloral hydrate, ach. 79, 82, 84 121-123 7.1.1.1.5 After the inflation to V30, 6.11 Gastric distention or aerophagia from air the infant is allowed to passively entering the esophagus. 73 exhale. These inflation-passive ex- halation maneuvers are repeated ITPFT 7.0 LIMITATIONS OF METHODOLO- until the infant exhibits a short res- GY/ VALIDATION OF RESULTS: piratory pause. 35, 68, 73 7.1.1.1.6 At the end of the V30 in- ITPFTs have classically been performed at large flation, the jacket is inflated to a medical centers with dedicated pediatric staff. preset pressure to initiate the Limitations of performing these tests are: (1) the forced exhalation maneuver. 35, 68, 73 need for at least two trained personnel to perform 7.1.1.1.7 The above maneuver is the maneuvers; (2) the sedation requirements, (3) repeated at increasing jacket pres- inadequate sleep deprivation of the patient, and (4) sures until flow limitation is

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achieved. (i.e. no further increases 7.1.2.1.3 Infant allowed to tidal in flow despite an increase in jacket breathe through the circuit until 35, 68, 73 pressure of 10 to 15 cm H2O) stable tidal breathing established. 7.1.1.2 RVRTC Limitations: 68, 73 7.1.2.1.4 Once stable tidal breath- 7.1.1.2.1 Increased upper airway ing established, jacket inflated to resistance may interfere with the initiate forced exhalation. accuracy of intrathoracically deter- 7.1.2.1.5 Maneuver repeated at in- mined flows. creasing jacket pressures until flow 7.1.1.2.2 Airflow may be affected limitation (no increase in flows de- by upper airway obstruction and spite an increase in jacket pressure nasal compression or by head and of 10 to 15 cm H2O) presumably neck positioning. (Subject posi- has been achieved. tioning must minimize pharyngeal 7.1.2.1.6 Flow measured and refer- narrowing.) 73 enced to functional residual capaci- 7.1.1.2.3 Reflex glottic closure ty (FRC) (complete or partial) may limit 7.1.2.2 Limitations of Partial Flow- flow. 73 Volume Curves 35, 49, 68 7.1.1.2.4 Hug pressures may range 7.1.2.2.1 Increased upper airway from < 40 to > 100 cm H2O. How- resistance may interfere with the ever, if too little pressure is trans- accuracy of intrathoracically deter- mitted to the pleural space, flow mined flows. limitation will not be achieved.127 7.1.2.2.2 Airflow may be affected Conversely, excessive pressures by upper airway obstruction and may alter the shape of the curve, nasal compression or by head and via negative effort dependence. 73, neck positioning. (Subject posi- 81 tioning must minimize pharyngeal 7.1.1.2.5 Improperly sized and/or narrowing.) positioned “hug” bag may lead to 7.1.2.2.3 Flows are referenced to inaccurate results 73 FRC, which is a dynamic lung vol- 7.1.1.2.6 Pneumotachometer with ume affected by sleep state and se- inappropriate flow range may lead dation. 68 to inaccurate results 73 7.1.2.2.4 Reflex glottic closure 7.1.1.2.7 Sedation may affect air- (complete or partial) may limit way patency, thus data results 68 flow. 7.1.1.2.8.Air may enter the stom- 7.1.2.2.5 Variations in end-expira- ach leading to gastric distension tory levels, or FRC, may affect and possibly a decrease in lung measurements ‘at FRC’ making volumes 68, 73, 128 therapeutic evaluations (e.g., effi- 7.1.1.2.9 Inability to achieve an ad- cacy of ) difficult. 68 equate seal with the facemask. 68, 73 7.1.2.2.6 Flow limitation may not 7.1.2 Partial Flow-Volume Curves: be reached 35, 68 7.1.2.1 Methodology of Partial Flow- 7.1.2.2.7 The flow-volume rela- Volume Curves 35, 49, 68 tionship produced by the partial 7.1.2.1.1 Sedated infant is placed flow-volume curve technique rep- supine; facemask is placed around resents a small portion of the entire nose and mouth and secured with maximal expiratory flow-volume therapeutic putty; inflatable jacket curve 35, 68 wrapped around thorax 7.1.2.2.8 Improperly sized and po- 7.1.2.1.2 Facemask is attached to a sitioned “hug” bag may lead to pneumotachometer false results.

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7.1.2.2.9 Pneumotachometer with RV to obtain total lung capacity inappropriate flow range may lead (TLC). 84, 90 to inaccurate results. 7.1.3.2 FRCpleth Limitations 7.1.2.2.10 Infant does not exhale to 7.1.3.2.1 Occlusion usually occurs residual volume 35 at end-inspiration because the in- 7.1.2.2.11 Inability to achieve an fant tolerates this maneuver better adequate seal with the facemask. 49 than occluding at end-expiration; 7.1.3 FRC measured via Plethysmography there is less glottic closure; and (FRCpleth) less signal to noise ratio. Investiga- 7.1.3.1 FRCpleth Methodology 35, 97, 101 tors have also hypothesized that 7.1.3.1.1 Sedated infant placed in FRC obtained at end-expiration plethysmograph, facemask placed may be inaccurate due to more air- around infant’s nose and mouth way closure at these lower lung and secured with therapeutic putty volumes. 35, 101, 129-132 and box closed. 7.1.3.2.2 One must assume that 7.1.3.1.2 Respiratory frequency of during the occlusion, when there is infant observed until thermal equi- zero flow that the upper airway librium reached. pressure equilibrates with the alve- 7.1.3.1.3 Once equilibrium is oli pressure. Lack of equilibration achieved, infant’s airway occluded could lead to inaccurate results. 101 at end-inspiration for 2 to 4 respi- 7.1.3.2.3 FRC is a variable lung ratory efforts using a valve in the volume and changes with sleep circuit. state and sedation 35 7.1.3.1.4 The lack of a decay in the 7.1.3.2.4 FRCpleth has been re- mouth pressure during the occlu- ported to be inaccurate in wheezy sion confirms the absence of a infants after bronchiolitis 129, 133 leak. 7.1.3.2.5 Minimal published data is 7.1.3.1.5 The maneuver is repeated available for fractional lung vol- at least 3 to 5 times until a mini- umes. 84, 90 mum of 3 acceptable FRC mea- 7.1.4 Gas Dilution and Ventilation Inhomo- sures are obtained geneity Techniques 7.1.3.1.6 Tidal volume is subtract- 7.1.4.1 Gas Dilution Methodology ed from FRCpleth to obtain the 7.1.4.1.1. All gases used in the di- true FRC at end-expiration lution techniques are inert, thus are 7.1.3.1.7 Fractional not part of and are are not possible using the RVRTC minimally soluble in blood 109 technique and FRCpleth measures. 7.1.4.1.2 Open-circuit Nitrogen 84, 90 However the expiratory re- Washout Methodology 35, 105,109 serve volume (ERV) is measured 7.1.4.1.2.1 Tidal breathing ob- following the RVRTC maneuver served in sedated infant to en- after the infant returns to stable sure stable FRC end expiratory level (FRC). The 7.1.4.1.2.2 At FRC, subject ERV is defined and measured as switched to a circuit and begins the lung volume difference be- to breathe 100% oxygen tween the end of FVC and the sta- 7.1.4.1.2.3 Bias flow is contin- ble end-expiratory level (FRC). uous and is above the inspira- RV is obtained by subtracting ERV tory flow rate of the infant. from FRC. Forced 7.1.4.1.2.4 Expired nitrogen (FVC) measured during the from the mixing chamber is RVRTC maneuver is added to the continuously analyzed

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7.1.4.1.2.5 Maneuver contin- inert gas through the mask ues until nitrogen levels drop until equilibration is achieved. to a baseline level 7.1.4.1.4.4 During the washout 7.1.4.1.2.6 FRC is equal to the phase, the gas supply is dis- volume of nitrogen expired di- connected. vided by the initial volume of 7.1.4.1.4.5 The infant breathes nitrogen in the minus room air until the tracer gas 0.02 (the factor, 0.02, repre- concentration reaches a sents the nitrogen concentra- certain threshold (below 0.1%) tion where washout is termi- 7.1.4.1.4.6 Since nitrogen is ex- nated). creted from other tissues, the 7.1.4.1.3 Closed-Circuit Helium washout for this gas continues Methodology 35, 109 until the gas concentration is 2%. 7.1.4.1.3.1 Infant’s tidal 7.1.4.1.4.7 Different gas ana- breathing observed until FRC lyzers may be used for this stable. technique including mass 7.1.4.1.3.2 Once FRC is sta- spectrometry, infrared technol- ble, the infant is connected to a ogy and the ultrasonic device. circuit with the known volume 7.1.4.1.4.8 FRC is equal to the of helium gas (V1) at FRC. total exhaled tracer gas vol- 7.1.4.1.3.3 Rapid helium ana- ume divided by the difference lyzer must be used between the gas concentration 7.1.4.1.3.4 Infant tidal at the beginning and end of the breathes until equilibration oc- washout. curs between the infant’s lungs 7.1.4.1.4.9 Measures of venti- and chamber containing the lation of inhomogeneity can be helium measured such as lung clear- 7.1.4.1.3.5 Once equilibration ance index (number of lung has occurred, V2 is calculated volume turnovers required to with the following equation: complete the washout OR the V1 X C1 (initial concentration ratio of cumulative expired of helium) = (V1 + V2) • C2 volume needed to complete (concentration of helium at the the washout divided by FRC), end of gas mixing). V2 is FRC. mixing ratio (ratio of actual 7.1.4.1.4 Breath-by-Breath number of breaths compared Washout Methodology 109, 134 to ideal number of breaths that 7.1.4.1.4.1 To perform this lowers the tracer gas to 1/40 of method, the infant breathes in the starting concentration). an inert gas, which may be ni- 7.1.4.2 Gas Dilution Limitations trogen, helium or SF6 (sulfur 7.1.4.2.1 Leaks invalidate hexaflourane). measurements 105 7.1.4.1.4.2 This method con- 7.1.4.2.2 The time required to sists of a wash-in and washout wait between sequential FRC phase unless using 100% measures may be inaccurate 105 oxygen during nitrogen 7.1.4.2.3 Open-circuit Nitrogen washout. Washout Limitations 35, 105, 109 7.1.4.1.4.3 During the wash-in 7.1.4.2.3.1 Errors may phase, the infant breathes the occur when switching to gas mixture containing the FRC

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7.1.4.2.3.2 Washout may 7.1.5.2 Dynamic Measures 33, 35 be longer in infants with 7.1.5.2.1 Dynamic measures are lung disease evaluated during spontaneous 7.1.4.2.3.3 FRC measures breathing with ongoing respiratory only communicating air- muscle activity ways, not the non-commu- 7.1.5.2.2 Dynamic measures may nicating airways; there- occur through (1) the analysis of fore, FRC measure may be airway resistance using plethys- inaccurate in severe ob- mography, (2) the evaluation of structive airways disease. lung resistance and compliance 7.1.4.2.3.4 Nitrogen ana- using esophageal manometry and lyzers may be inaccurate (3) forced oscillation techniques. due to non-linearity 7.1.5.2.3 Airway resistance mea- 7.1.4.2.4 Closed-Circuit Heli- sured during plethysmography um Limitations 35 (Raw) 35, 97, 101 7.1.4.2.4.1 Equilibration 7.1.5.2.3.1 Infant is placed in a may take up to 5 minutes plexiglass plethysmograph in infants with lung dis- 7.1.5.2.3.2 Unlike the adult, ease the infant is unable to pant, 7.1.4.2.4.2 Operator ex- thus the circuit contains a heat- pertise is essential for ac- ed, humidified gas at BTPS curate measures. that the subject rebreathes. 7.1.4.2.5 Breath by Breath 7.1.5.2.3.3 Airway resistance Washout Limitations 109, 134 is calculated from the flow 7.1.4.2.5.1 Gas concentra- measured at the pneumotacho- tions must be measured graph and from the difference accurately during rapid in pressure between the alveoli tidal breathing and the opening of the subject’s 7.1.4.2.5.2 Gas concentra- airway. (Raw = DP/ flow) tion must be correlated with 7.1.5.2.3.4 Since the heated the correct flow sample system is cumbersome, recent- 7.1.4.2.5.3 Pneumota- ly electronic compensation has chometer must be calibrat- been attempted. ed correctly with the vari- 7.1.5.2.3.5 Other measures are ous gases that can be used. possible, using FRC measured 7.1.4.2.5.4 Deadspace during plethysmography, includ- must be minimized. ing airway conductance (recip- 7.1.4.2.5.5 If using 100% rocal of Raw), specific resistance oxygen, this may alter the (Raw X FRC) and specific air- infant’s way conductance (airway con- 7.1.4.2.5.6 Mass spec- ductance divided by FRC) trometry is expensive 7.1.5.2.4 Dynamic Respiratory 7.1.4.2.5.7 No standards for Mechanics using esophageal performing the technique in manometry 33, 35 infants are available. 7.1.5.2.4.1 Esophageal 7.1.5 Compliance and Resistance Measure- catheter must be placed when ments infant is awake or sedated. 7.1.5.1 May be measured through pas- 7.1.5.2.4.2 Correct placement sive or dynamic techniques is critical for accurate

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transpulmonary pressure mea- ance is measured as the surements. Esophageal pres- change in volume divided by sure reflects pleural space the change in pressure (calcu- changes due to close apposi- lated as the difference be- tion of esophagus to pleura. tween atmospheric pressure 7.1.5.2.4.3 May use liquid- and plateau achieved during filled catheter, esophageal bal- the occlusion). loon or catheter tip pressure 7.1.5.3.6 Other parameters that transducer to perform mea- may be measured include: re- surements. sistance of the respiratory sys- 7.1.5.2.4.4 During these mea- tem and time constants. sures, tidal volume, flow and 7.1.5.3.7 During the multiple pressures changes at the air- occlusion technique, the air- way opening and esophagus way opening is briefly occlud- are measured with the aid of a ed at different volumes above pneumotachometer or flow the end expiratory level meter. 7.1.5.3.8 During the multiple 7.1.5.2.4.5 Stable tidal breath- occlusion technique, the mea- ing is essential. sured airway opening pressure 7.1.5.2.4.6 Compliance and re- and volume are recorded on x- sistance are assessed using y plots and the slope is ana- measures of volume, flow and lyzed as the compliance of the transpulmonary pressures. respiratory system. Methods of analysis include 7.1.5.3.9 Modifications of the the Mead-Whittenberger tech- occlusion techniques include a nique, the least-squares regres- weighted tech- sion technique, the multiple nique (very little published linear regression technique and since the early 1990s), expira- the Mortola-Saetta technique. tory volume clamping and as- 7.1.5.3 Passive Respiratory Me- sessing compliance using the chanics 8, 33 RVRTC technique from near 7.1.5.3.1 May use a single or total lung capacity. 21, 25 multiple occlusion technique 7.1.5.4 Limitations of Dynamic 7.1.5.3.2 For occlusion tech- Measures niques, the Hering-Breuer re- 7.1.5.4.1 Limitations of Raw flex must be invoked to elicit measures 97, 101 relaxation of the respiratory 7.1.5.4.1.1 Complex system. equipment is needed to 7.1.5.3.3 For the both occlu- measure Raw. sion techniques, a facemask is 7.1.5.4.1.2 Traditionally, a placed around the infant’s nose heated rebreathing bag is and mouth. needed for Raw measure- 7.1.5.3.4 During the single oc- ments clusion technique, at least 5 7.1.5.4.1.3 Electronic tidal breath are collected and a compensation has been in- brief occlusion takes place at troduced in place of the end inspiration heated rebreathing bag for 7.1.5.3.5 During the single Raw measurements, but occlusion technique, compli- validation is needed.

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7.1.5.4.2 Limitations of Dy- measuring flow and volume namic measures obtained with using a pneumotachometer and an esophageal catheter 33 (2) respiratory inductive 7.1.5.4.2.1 Improper plethysmography, using bands placement of esophageal that measure chest and abdom- catheters may lead to erro- inal wall movement neous results of resistance 7.1.6.1.2 Simple, noninvasive and compliance measures. technique 7.1.5.4.2.2 Esophageal 7.1.6.1.3 Respiratory rate, tidal pressures not accurately volume (Vt), and the ratio of measured with chest wall time to peak tidal expiratory deformities or severe air- flow and total expiratory time way obstruction. (tPTEF/ tE) are common param- 7.1.5.4.2.3 Resistance eters measured. measures dominated by 7.1.6.1.4 Phase angle is mea- upper airway resistance sured using inductive plethys- 7.1.5.4.2.4 No commer- mography and reflects the syn- cially available device chrony or asynchrony of the 7.1.5.4.2.5 Dynamic respi- abdominal wall compared to ratory mechanic measures the rib cage have not been standardized. 7.1.6.2 Tidal Breathing Limitations 7.1.5.4.3 Limitations of Pas- 35, 41, 42 sive respiratory mechanics 33 7.1.6.2.1 Minimal deadspace is 7.1.5.4.3.1 Assumption of critical pressure equilibration be- 7.1.6.2.2 There may be vari- tween airway opening and ability of the respiratory rate alveoli not valid in severe- and volume, which may be due ly obstructed patients. to sleep state, weight or gesta- 7.1.5.4.3.2 Measures total tional age respiratory system resis- 7.1.6.2.3 Tidal breathing may tance and compliance; un- provide additional objective like dynamic measurements information when combined where respiratory system with other clinical tools. components may be parti- 7.1.7 Forced Deflation tioned due to the esophageal 7.1.7.1 Forced Deflation Method- pressure measures ology 111 7.1.5.4.3.3 Resistance 7.1.7.1.1 The infant’s lungs are measures dominated by inflated to 40 cm H2O pressure upper airway resistance, for at least 3 seconds then de- thus changes in lower air- flated with the use of negative way resistance may not be pressure (-40 cm H2O) accurately measured 7.1.7.1.2 Lungs deflated until 7.1.6 Tidal Breathing Maneuvers infant reaches RV or for a max- 7.1.6.1 Tidal Breathing Methodol- imum of 3 seconds. ogy 41, 42 7.1.7.1.3 This technique re- 7.1.6.1.1 Two ways to obtain quires intubation and heavy se- tidal breathing measures: (1) dation. Placing a facemask around in- 7.1.7.1.4 Flow limitation is fant’s nose and mouth and possible

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7.1.7.2 Forced Deflation Limita- 8.2 Interrupter Resistance 113, 114, 135 tions 111 8.2.1 May be ideal in infants since requires 7.1.7.2.1 A cuffed endotra- no cooperation and can be performed cheal tube is desirable to pre- without sedation. 114 vent leaks 8.2.2 Measured by applying a brief 7.1.7.2.2 Endotracheal tube interruption to airway flow during tidal size may affect flows breathing. 7.1.7.2.3 Deep sedation and/or 8.2.3 Pressure and flow measured at the paralysis is required airway opening during these brief interrup- 7.1.7.2.4 Deflation may affect testing due to an effect on tions. Resistance calculated as the ratio of ; however, the pressure change versus flow measured recruitment with the inflation at the airway opening during the brief maneuver may offset this po- interruption. tential problem. 7.2 Reference values are critical when perform- ITPFT 9.0 ASSESSMENT OF NEED: ing ITPFTs; however, there is a lack of these Although progress has been made in the clinical values due to the difficulty of recruiting con- use of ITPFTs, this tool has historically been used trols and due to ethical reasons associated with in the research setting. sedation of healthy infants. Published reference data is lacking. Lack of appropriate reference ITPFT 10.0 ASSESSMENT OF data leads to difficulty in assessing disease ver- OUTCOME/TEST QUALITY: sus normal growth/development. 60, 79, 84, 96, 120 Outcome and test quality are determined by ascer- ITPFT 8.0 RECENT TECHNIQUES taining that the desired information has been gener- 8.1 Forced Oscillation: 115-117, 120, 135 ated for the specific indication(s) and that the infor- 8.1.1 May be ideal in infants since requires mation is valid and reproducible. Each laboratory should standardize procedures and demonstrate no cooperation and can be performed inter-technician reliability. Test results can only be without sedation. considered valid if they are derived according to 8.1.2 Respiratory impedance assessed by and conform to established laboratory quality con- applying oscillations (usually from a loud- trol and quality assurance protocols. These proto- speaker) to the airway opening. cols should address test standardization and repro- Impedance is equal to the ratio of pressure ducibility criteria that include the methodology and flow measured at the airway opening used to derive and report the ITPFTs. 136 during the application of these oscillations. 10.1 ITPFTs performed for the listed indica- Impedance represents the real (resistive) tions are valid only if the instrumentation func- and imaginary (reactance) components of tions acceptably and the maneuvers are ob- the respiratory system. 116, 135 tained in an acceptable, reproducible fashion. 10.2 Report of test results should contain a 8.1.3 Measurements may be assessed at a statement by the technician performing the test low-frequency, which leads to partitioning about test quality and if appropriate, which rec- of airway and tissue mechanics. For this ommendations were not met. technique, a brief respiratory pause is nec- essary and is achieved using inflation pres- ITPFT 11.0 RESOURCES: sures at the airway opening to induce the 11.1 Equipment: Equipment specifications Hering-Breuer reflex. 117 should conform to recognized standards 8, 49, 73, 97, 8.1.4 Measurements have also been 105, 118 and where applicable, be FDA approved. 11.1.1 assessed at high-frequency, with results re- Distinctive pneumotachograph, heli- flecting airway wall mechanics 115 um analyzer and nitrogen analyzer perfor-

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mance specifications. Appropriate use of the results (The final report should contain a gas analyzers is dependent upon the statement about testing conditions and test methodology employed. 118 quality.) 11.1.2 Gases must be medically certified. 12.2 The final report should contain the re- 11.1.3 Size-appropriate resuscitation equip- quested parameters and lung-volume corrected ment (including appropriate pharmacologic values (if applicable). agents) must be readily available. 118, 119 12.3 The patient for any adverse effects of test- 11.1.4 Sedation monitoring equipment must ing 118 be available (e.g., continuous pulse oxime- 12.3.1 Infants undergoing conscious seda- try with pulse rate and capnograph). 118, 119 tion should be pre-assessed prior to seda- 11.1.5 Calibrated stadiometer and scale for tion, be appropriately monitored during and accurate height and weight measurements after IPFT, with sedative information in- (respectively) on the day of the procedure cluded in the final report. 118, 119 11.2 Personnel: 118 12.3.2 Patients on supplemental oxygen 11.2.1 ITPFTs should be performed under may require periods of time to rest (on oxy- the direction of a physician trained in infant gen) between trials. pulmonary function testing methodologies (including limitations and applications). ITPFT 13.0 FREQUENCY: The value of ITPFT results are compro- mised when a test is administered and/or in- The frequency at which ITPFT measurements are terpreted by inadequately trained person- repeated depends on the clinical status of the patient nel. and the indications for performing the test. 11.2.2 Testing personnel should be specifi- cally trained (with verifiable training and ITPFT 14.0 INFECTION CONTROL: demonstrated competency) in all aspects of ITPFTs, including equipment theory of op- Infant/toddler pulmonary function tests are relative- eration, quality control, and test outcomes ly safe procedures, but the possibility of cross-con- relative to diagnosis and/or medical history. tamination exists, either from the patient-patient or Proficiency must also be demonstrated rel- patient-technologist interface. 124-126 ative to technician’s ability to calibrate 14.1 Universal Precautions (as published by the equipment, apply ancillary devices to the Centers for Disease Control) should be applied patient, perform the test, monitor the pa- in all instances in which there is evidence of tient and determine the quality of the test. contamination with blood (e.g., pneumota- 11.2.2.1 Testing personnel should, at chometers and adapters). Although Universal minimum, be trained in basic life sup- Precautions do not apply to saliva or un- port and preferable to have advance less it contains blood, other potentially hazardous (neonatal [NRP] or pediatric [PALS]) organisms may be present in these fluids even in life support training the absence of blood, and the appropriate use of 11.2.2.2 At least one of the following barriers and hand washing are recommended. credentials is recommended: CRT, 14.2 Due to the nature of some ITPFT maneu- RRT, CPFT, RPFT, LPN, RN, NP, vers and the possibility of coughing when the CRNA, PA-C, MD, DO. test is performed by subjects with active infec- tion with M tuberculosis or other airborne or- ITPFT 12.0 MONITORING: (Also see Section ganisms, the following precautions are recom- 10.0 ASSESSMENT OF TEST QUALITY) mended: 124 14.2.1 If a maneuver is likely to stimulate The following should be monitored during ITPFT or induce a cough, disposable gloves, pro- determinations: 136 tective outerwear, along with masks (which 12.1 Test data of repeated efforts (i.e., repro- comply with OSHA requirements) and pro- ducibility of results) to ascertain the validity of tective eyewear should be utilized. This

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personal protective equipment is also to be 3. Young S, Arnott J, O’Keeffe PT, Souef L, Landau LI. used when testing patients with known or The association between early life lung function and suspected, potentially infectious airborne wheezing during the first 2 yrs of life. Eur Respir J disease(s). 2000;15(1):151-157. 14.2.2 The room in which ITPFTs are per- 4. Sheikh S, Goldsmith LJ, Howell L, Hamlyn J, Eid N. formed should meet or exceed the recom- Lung function in infants with wheezing and gastroe- mendations of U.S. Public Health Service sophageal reflux. Pediatr Pulmonol 1999;27(4):236-241. for air changes and ventilation. The most 5. Chavesse RJ, Bastian-Lee Y, Richter H, Hilliard T, Seddon desirable arrangement may be to maintain a P. Inhaled salbutamol for wheezy infants: a randomised specially ventilated area in the testing de- controlled trial. Arch Dis Child 2000;82(5):370-375. partment for isolation patients. 6. Chavasse RJ, Bastian-Lee Y, Richter H, Hilliard T, Sed- 14.3 Any parts of the system that come into con- don P. Persistent wheezing in infants with an atopic ten- tact with the subject should be disposable or ster- dency responds to inhaled fluticasone. Arch Dis Child ilized between patients. If sterilization is not fea- 2001;85(2):143-148. sible, then high-level disinfection should be per- 7. Derish M, Hodge G, Dunn C, Ariagno R. Aerosolized al- formed. 36 All cleaning should comply with buterol improves airway reactivity in infants with acute manufacturer recommendations. Several pneu- respiratory failure from respiratory syncytial virus. Pedi- motachometers and/or valving assemblies may atr Pulmonol 1998;26(1):12-20. be required if cleaning cannot be performed in a 8. Gappa M, Colin AA, Goetz I, Stocks J. Passive respirato- timely manner between patients. ry mechanics: the occlusion techniques. Eur Respir J 14.4 The use of bacterial filters is controversial. 118 2001;17(1):141-148. 14.4.1 Attachment may result in added sys- 9. Hartmann H, Seidenberg J, Noyes JP, O’Brien L, Poets tem and may invalidate pneu- CF, Samuels MP, Southall DP. Small airway patency in motachometer accuracy by increasing total infants with apparent life-threatening events. Eur J Pedi- system resistance of the apparatus. atr 1998;157(1):71-74. 14.4.2 Filter resistance should be subtract- 10. Dakin CJ, Numa AH, Wang H, Morton JR, Vertzyas CC, ed from Raw (and related parameters) Henry RL. Inflammation, infection, and pulmonary func- 14.4.3 If filters are used in gas-dilution pro- tion in infants and young children with cystic fibrosis. cedures, their volume should be subtracted Am J Respir Crit Care Med 2002;165(7):904-910. when FRC is calculated. 24 11. Shao H, Sandberg K Hjalmarson O. Impaired gas mixing and low lung volume in preterm infants with mild chron- Infant/Toddler PFT Guidelines Steering Committee: ic lung disease. Pediatr Res 1998;43(4 Pt 1):536-541. Stephanie D Davis, MD, Chairman, Chapel Hill NC 12. Lucas JS, Inskip HM, Godfrey KM, Foreman CT, Warn- Robin C Johnson RRT, Chairman, Chapel Hill NC er JO, Gregson RK, Clough JB. Small size at birth and Robert L Flucke RRT, Columbus OH greater postnatal weight gain: relationships to diminished Jeffrey A Kisling RRT, Indianapolis IN infant lung function. Am J Respir Crit Care Med Timothy R Myers RRT, Cleveland OH 2004;170(5):534-540. 13. Platzker AC, Colin AA, Chen XC, Hiatt P, Hunter J, Original Publication: Respir Care 1995;40(7):761–768. Koumbourlis AC, et al. Thoracoabdominal compression and respiratory system compliance in HIV-infected in- REFERENCES fants. Am J Respir Crit Care Med 2000;161(5):1567- 1. Dezateux C, Stocks J, Dundas I, Fletcher ME. Impaired 1571. airway function and wheezing in infancy: the influence 14. Dobyns EL, Griebel J, Kinsella JP, Abman SH, Accurso of maternal smoking and a genetic predisposition to asth- FJ. Infant lung function after inhaled nitric oxide therapy ma. Am J Respir Crit Care Med 1999;159(2): 403-410. for persistent pulmonary hypertension of the newborn. 2. Yau KI, Fang LJ, Shieh KH. Factors predisposing infants Pediatr Pulmonol 1999;28(1):24-30. to lower respiratory infection with wheezing in the first 15. Lui K, Lloyd J, Ang E, Rynn M, Gupta JM. Early two years of life. Ann Allergy Asthma Immunol changes in respiratory compliance and resistance during 1999;82(2):165-170. the development of bronchopulmonary dysplasia in the

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