WO2000048513A1 - Technique permettant de mesurer le volume residuel des poumons chez les jeunes enfants - Google Patents

Technique permettant de mesurer le volume residuel des poumons chez les jeunes enfants Download PDF

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WO2000048513A1
WO2000048513A1 PCT/US2000/004044 US0004044W WO0048513A1 WO 2000048513 A1 WO2000048513 A1 WO 2000048513A1 US 0004044 W US0004044 W US 0004044W WO 0048513 A1 WO0048513 A1 WO 0048513A1
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volume
infant
washout
frc
lung
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PCT/US2000/004044
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Mohy G. Morris
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Board Of Trustees Of The University Of Arkansas
Arkansas Children's Hospital Research Institute, Inc.
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Priority to AU29995/00A priority Critical patent/AU2999500A/en
Publication of WO2000048513A1 publication Critical patent/WO2000048513A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/091—Measuring volume of inspired or expired gases, e.g. to determine lung capacity

Definitions

  • FRC functional residual capacity
  • FRC Fluorescence Activated bowel syndrome
  • TLC30 total lung capacity at a raised lung volume (V30) to an airway opening pressure (P ao ) of 30 cm H 2 0.
  • P ao airway opening pressure
  • TLC 30 has been measured invasively by tracer gas (Thorsteinsson et al., 1994) and nitrogen (Hammer et al., 1998) washout in intubated infants in the intensive care unit. We measured it noninvasively in three ways:
  • V 30 Raising the lung volume (V 30 ) to an airway opening pressure (P ao ) of 30 cm H 2 0 then allowing expiration to proceed passively.
  • the squeeze jacket for rapid thoracoabdominal compression (RTC) is triggered before the end of the passive expiration to induce a forced expiration down to residual volume (RV).
  • RV residual volume
  • Flow is integrated to produce volume, the vital capacity (from V 30 down to RV).
  • RV By measuring the volume of nitrogen expired after end-forced expiratory switching of the inspired gas from room air to 100% oxygen while thoracoabdominal compression was maintained during the post-expiratory pause, RV is estimated.
  • TLC 30 represents the sum of RV and the expired volume (vital capacity) from V 30 down to RV.
  • the exact switching time is determined as well as a characteristic negative deflection caused by the outward springing of the compressed chest, occurring synchronously with jacket deflation.
  • TLC30 was estimated.
  • the technique may be used for routine clinical as well as research studies of lung function in infants from birth until three years of age. It will assist in defining the normal development and growth of the lungs, to determine the efficacy of therapeutic interventions (surfactant treatment in premature newborns, liquid ventilation in critically ill infants, and the use of pulmozyme in cystic fibrosis), and to evaluate the relation between lung injury in early life and chronic lung disease. It has the potential of being similarly used in experimental animal studies as well.
  • An automated system can be designed and programmed to perform the measurements. Using a three-way balloon valve, such a system would be capable of automatically raising the lung volume to V 30 , triggering the squeeze jacket, and switching the patient into O 2 .
  • the maneuvers can be summarized as follows:
  • Measurement of FVC Hyperventilate the infant; raise to P a0 of 30 cm H 2 0; hold for 0.06 s; trigger the jacket; deflate the jacket after 3 (or 4) seconds.
  • An automated system can be made to measure FVC and RV in the same breath.
  • Fig. 1 is a schematic view of the nitrogen washout circuit.
  • Figs. 1 A and B schematically illustrate operation of the apparatus when the infant is breathing air (Fig. 1A) and oxygen (Fig. 1B), respectively.
  • Figs. 2 A, B, C are graphs of the mean (SD [T]) of residual volume (RV) [ ] and functional residual capacity (FRC) [o] from each infant plotted against the respective height, weight and age.
  • the straight dashed and solid lines are RV and FRC regression lines, respectively.
  • the curved dotted lines represent the 95% confidence limit.
  • Fig. 3 is four graphs showing the measurement of the residual volume (RV) with example traces of flow, volume, airway opening pressure (P ao ) and jacket pressure (Pj) from infant # 6.
  • Figs. 4, 5, and 6 are graphs illustrating the measurement of the residual volume in patients (pf) 2, 7, and 6, respectively, zoomed on the time period that begins with jacket inflation and ends at the 20 th second of the data collection period. Each figure includes a trace of flow, volume, airway opening pressure (P ao ), and jacket pressure (P j ).
  • Fig. 7 shows two graphs illustrating the measurement of the residual volume including traces of P ao and Pj from pt 3. It zooms on the period between the switching into oxygen and ends at the 20 th second.
  • Fig. 8 is a graph showing the nitrogen washout curve of residual volume.
  • Figs. 9 A, B, C are graphs of the mean (SD [T]) of forced vital capacity
  • FVC mean total lung capacity at a raised lung volume to an airway opening pressure of 30 cm H 2 0 (TLC 30 ) [•] from each infant plotted against the respective height, weight and age.
  • the straight dashed and solid lines are FVC and TLC 30 regression lines, respectively.
  • the curved dotted lines represent the 95% confidence limit.
  • Fig. 10 shows four graphs illustrating the influence of the collapsible breathing bag (BB) on gas flow in the N 2 mixing chamber during in vitro washout.
  • the flow and volume signal patterns are compared using a pneumotachometer connected to the outlet of the N 2 mixing chamber, before (lower two panels) and after the BB was introduced in the washout circuit. Note the presence of flow transients in the absence of BB.
  • FRC functional residual capacity
  • RV residual volume
  • RTC (SensorMedics, CA) for N 2 washout and a custom-made system to perform RTC.
  • RTC was performed from a raised lung volume (V 30 ) to an airway opening pressure of 30 cm H 0.
  • the jacket pressure (Pj) (range 65-92 cm H 2 0) which generated the highest forced expiratory volume ⁇ range, 22.3-49.1 ml/kg; (mean) 40.2 ml/kg; 95% confidence interval [C1] 33.03, 47.33 ⁇ , was used during the RV maneuver.
  • the infant was manually hyperventilated to briefly inhibit the respiratory drive.
  • RTC was initiated during the last passive expiration.
  • RV was estimated.
  • SD mean (SD) period between the switching to 0 2 and the end of the Pj plateau was 0/301 (0.187) s.
  • RV and FRC measurements were reproducible and did not overlap; the difference (expiratory reserve volume) between means was statistically significant (p ⁇ 0.05).
  • Mean RV was 21.3 (Cl 18.7,24.0), RFC, 25.5 (Cl 22.8, 28.1) and TLC 30 (total lung capacity at V 30 ), 61.5 (Cl 54.4, 68.7) ml/kg. Means exhibited body length and weight as well as age dependence. When measuring RV, the period between the switching to 0 2 and the end of the Pj plateau was 0.301 (Cl 0.211 , 0.391) s. The RV washout duration was longer than FRC's: 80.9 (Cl 71.3, 90.4) was 72.4 (Cl 64.9, 79.8) s (p ⁇ 0.001). We have developed a new, noninvasive and reliable technique for routine measurement of RV in infants.
  • Figs. 1 , 1A, and 1 B schematically illustrate the nitrogen washout circuit.
  • the infant is fitted with face mask 30 and breathes through the three-way slide valve 14, pneumotachometer 21 and Y-adapter 20. Air is introduced through inspiratory limb 25 of Y-adapter 20 and expired through expiratory limb 22 of Y-adapter 20 when three-way slide valve 14 is operated for air breathing (shown schematically in Fig. 1 A).
  • the long parallel dotted lines 10 point to the connection site of the central port 12 of the aerosol T adapter 13 onto the inlet-outlet port 11 of the slide valve 14.
  • Oxygen is introduced through inlet 31 of aerosol "T” adapter 13 and when slide valve 14 is operated so as to allow the infant to breath oxygen, the oxygen- nitrogen washout is expired from outlet 32 of aerosol "T” adapter 13.
  • a breathing bag 40 may be inserted into the circuit by means of "T" connector 41 to inlet 31 of aerosol "T'adapter 13.
  • the Y-adapter 20 is connected to the pneumotachometer (vertical, parallel fine-dotted lines) 21. Occlusion of the expiratory limb 22 of the Y-adapter 20 diverts the air to the infant, raising the lung volume to an airway opening pressure plateau set at 30 cm H 2 0 by the pressure relief valve 23.
  • FRC functional residual capacity
  • Pred predicted
  • TLC 30 total lung capacity at a raised lung volume to a Pao of 30 cm H 2 O and represents the sum of FVC and RV from each subject
  • Pj jacket pressure.
  • FRC and RV were corrected for EDS and converted to BTPS.
  • RVRTC maneuvers were performed from V 30 , i.e., a raised lung volume to a predetermined airway pressure (P ao ) of 30 cm H 2 O.
  • P ao airway pressure
  • Pj jacket pressures
  • the Pj that generated the highest FVC was used during the RV measurement.
  • a P j higher by 10 cm H 2 0 was used once to find out whether further chest compression could have generated a smaller RV.
  • RV and FRC measurements were performed at random. A period of at least twice the washout time was allowed between measurements.
  • the compression jacket consisted of an inflatable plastic plate held over the chest and abdomen with a firm vinyl outer layer (VOL). RTC was performed with the arms outside the jacket to avoid possible splinting of the chest wall (Steinbrugger B, Alnigan A, Raven JM, et al. Influence of the "squeeze jacket on lung function in young infants". Amer Rev Respir Dis 1988; 138,1258-60.).
  • the VOL ( ⁇ erculite 80', Vicar International, New Jersey, NJ) was modified for the present study by inserting a 14 in.
  • zipper ('separating Sport zipper'; Coats and Clark, Greenville, SC) so that the VOL could be loosened during FRC measurement, with minimal disturbance to the sleeping infant, to avoid any possible limitation to chest wall excursions during tidal breathing.
  • Tensile resistance was maximized by covering the zipper with a strip of the firm vinyl on each side of the zipper teeth. With the zipper sandwiched between the vinyl strips and VOL, it was further anchored to the VOL by stitching through the strips, zipper and VOL. Furthermore, the zipper extended 5 cm beyond the upper and lower edges of the VOL to ensure that a uniform tension extended to the very edge of the VOL.
  • a soft plastic air cushion mask 30 (Kings Systems, Noblesville, IN) was held on the mouth and nose forming an airtight seal.
  • the mask connection port had a 10 mm inner diameter (ID) that was cut out and replaced with a 22 mm ID connection.
  • Airway opening pressure (P ao ) was measured with a pressure transducer 31 (FPM-02PG; Fujikura, Tokyo, Japan) from a port mounted into the dome of mask 30.
  • FPM-02PG Fujikura, Tokyo, Japan
  • One end of a heated 0-160 Umin screen pneumotachometer 21 (PNT) (Hans Rudolph Inc., Kansas City, MO) was connected to the mask port; the other, to a one-way balloon-valve (Model 9340; Hans Rudolph Inc.).
  • the latter in turn, was connected to a series of solenoid valves that allowed for inflation of the infant's lungs to a predetermined P ao of 30 cm H 2 0 (V 30 ) by means of a fan pump (Inflate-all; Coleman Co. Inc., Wichita, KS).
  • the inflatable jacket was then pressurized and forced expiration proceeded from V 30 to RV.
  • the sequence of valves was controlled by BRATLAB software (RHT-INFODAT, Montreal, PQ, Canada) on a computer. This integrated software sensed P ao , halted inflation, and initiated expiration.
  • the differential pressure across the PNT was measured with a 0 to 7 cm H 2 0 differential pressure transducer (PX170- 07DV; Omega International Corp., Stamford, CT) and amplified (SC14C; RHT- INFODAT, Montreal, Canada) in order to measure flow. Flow was integrated to produce volume. All signals were collected and analyzed on computer with LABDAT-ANADAT 5.2 data acquisition and analysis software (RHT-INFODAT). As shown in Fig. 1 , a Y-adapter 20 with a central mount (Bird Products Co oration, Palm Springs, CA) was used to hyperventilate the infant with several rapid inflations prior to RVRTC.
  • Calibration of the PNT was performed with a high precision calibrating flowmeter that had high-resolution valves (Gilmont Instruments, Barrington, IL). Calibration was re-checked by injecting and withdrawing known air volumes (100, 200, 300 and 500 ml) from a calibrating syringe and integrating the flow signal to produce volume. The latter differed by less than 0.5 % from the known volume.
  • the mouth's pressure transducer was calibrated with a U-shaped water manometer (range 0-60 cm H 2 0; Dwyer Instruments Inc., Michigan City, IN ) and the jacket's, with a diaphragm-operated differential pressure manometer. ('Magnehelic', range 0-150 cm H 0; Dwyer Instruments Inc.).
  • the nitrogen washout technique :
  • Lung volume (FRC or RV) Volume N 2 washed out ⁇ FAI,N2
  • the PPU has an operator-controlled pneumatic slide valve that switches the infant to breathing 100% 0 2 .
  • the expired gas enters a mixing chamber that is connected via a precision needle valve and a vacuum pump to a N 2 analyzer, and the N 2 concentration is integrated electronically by the PPU signal processing system.
  • the N 2 washout curve is displayed in real-time on the computer monitor. When a 0% N 2 concentration is displayed on the monitor, the slide valve is activated and the infant is switched back to breathing room air, and FRCN2 or RVN2 are automatically calculated by the system.
  • the latent period before the rise above baseline of the N 2 washout curve as well as the washout duration were recorded.
  • the nitrogen washout circuit (Fig. 1).
  • a three-way pneumatic slide valve (8540 Series - 9.5 mm Flow Bore Size; Hans Rudolph Inc.) was used. It had a mouth Port (22 mm outer diameter (OD) x 15 mm ID), and two other smaller inlet/outlet ports (15 OD X 10.5 ID mm).
  • the oxygen flow of a high precision flowmeter (Timemeter Instrument Corporation, Lancaster, PA) was accurately set by adjusting the middle of the float to the 10 L/min mark. This flow rate was used for all tests.
  • the O2 tubing (King Systems Corporation, Noblesville, IN) was connected to the 1/8 in.
  • an adapter Hospitak Inc., Farmingdale, NY
  • a 0.5 L collapsible breathing bag Vital Signs Inc., Totowa, NJ
  • the distal (third) end (22mm ID) of the T connection was fitted onto an aerosol T adapter (22 mm OD) (Hudson Respiratory Care Inc., Temecula, CA).
  • the center port (15 mm ID) of the aerosol T adapter was inserted onto the small port (15 mm OD) of the 3-way slide valve situated at a right angle from the mouth port.
  • the opposite end (22 mm OD) of the aerosol T adapter was inserted in a distensible coupling connector (29 mm OD X 17 mm ID) (Marquest Medical, Aurora, CO ) and a very snug fit was obtained.
  • a 'Concha Hose Adapter' (Respiratory Care Inc., Arlington Heights, IL) joined with a snug fit the other end of the coupling connector and the proximal end of a 2.0 m long hose (Tygon' 3/8 in ID X 5/8 in OD; Baxter Healthcare Corporation).
  • the vacuum pump with its 0 flow was turned on 30 min, the PPU measurement module and computer, at least 20 min before calibrating.
  • the breathing bag was squeezed manually several times to wash out any N2.
  • the computer software N 2 Calibration Menu was accessed.
  • the displayed nitrogen concentration was 0.0%; if not, it was zeroed using the 'autozero' mode of the PPU software. A check for the presence of a baseline drift was then performed.
  • the menu of the 'Low' (or 'High') volume calibration was accessed. When the displayed N 2 concentration was 0.0%, the slide valve was activated and the mouth port was left open to room air for 10 sec in order to wash out the air within the port by the pure 0 2 .
  • the port was then occluded to prevent room air from diffusing back into the port.
  • the N 2 concentration and the integrated % nitrogen signal (INS) were observed for 90 sec for a stable 0.0 reading. If the INS were to rise, then a baseline drift was presumed to be present, the 'Escape' key on the computer keyboard was pressed and the calibration menu was re-accessed. Though the displayed N 2 concentration was still 0.0%, a further decrease of the baseline towards zero was performed using 1-3 keyboard strokes in the 'manual' mode of the program, followed by a repeat check for a baseline drift. Over-correction, which resulted in a negative % N 2 concentration reading, was not allowed.
  • INS integrated % nitrogen signal
  • the PPU was adapted by connecting the PNT - attached to its flow transducer - of the CCCS to the 22 mm ID end of a plastic adapter (Baxter Healthcare Corporation) whose other 15 mm ID end fitted on the second small port of the 3-way slide valve (Fig. 1).
  • a plastic adapter Baxter Healthcare Corporation
  • Fig. 1 Prior to FRC measurement, the VOL was unzipped to avoid any splinting of the chest during tidal breathing.
  • the slide valve's mouth port was connected to a size 1 transparent face mask (Rendell-Baker Soucek Pediatric Face-mask; Gary Hull Anesthesia, Huntington Beach, CA) which was held onto the infant's face with silicone putty (Theraputty', North Coast Medical Inc., San Jose, CA) and an airtight seal was achieved.
  • the Y-adapter -described above - was connected to the PNT-slide valve assembly to perform rapid lung inflations (Fig. 1).
  • Airway opening pressure (P ao ) was measured with a pressure transducer (FPM-02PG) from a port mounted into the dome of the clear mask.
  • the slide valve assembly was connected to the clear face mask which was kept on the infant's face with an airtight seal by means of the silicone putty.
  • the RV measurement was performed by one operator.
  • the PPU and CCCS computers' keyboards were brought close to the sleeping infant by means of extension cables.
  • Several rapid inflations were delivered to the infant lungs by occluding the expiratory limb of the Y-connection until the infant's respiratory drive was inhibited (Fig. 1A). After the last inflation, the flow limb of the flow-volume loop signal was watched closely on the monitor screen. Expiration was allowed to proceed initially passively, then jacket inflation was activated during the last portion of exhalation to induce a forced expiration. Once jacket inflation was triggered, the P j signal was instantaneously observed.
  • the slide valve was activated, switching the infant to breathing 100% 0 (Fig. 1 B) before the decline of the P j plateau which coincided with maximum chest compression (Fig. 3).
  • the total duration of jacket inflation was set for three seconds.
  • a 0% N 2 concentration was displayed on the PPU monitor, the slide valve was activated and the infant was switched back to breathing room air.
  • Three criteria were set for an acceptable RV measurement.
  • the slide valve was switched, the air flow (F) and pressure (P ao ) at the mouth had been zero while a maximal chest compression was maintained as indicated by a raised Pj plateau.
  • the period between the activation of the slide valve and the end of the Pj plateau was estimated for each RV measurement (see Results below). At least two RV measurements within 10% were obtained.
  • TLC3 0 was expressed as per cent predicted based on an equation derived from a study on 40 children without lung disease in whom TLC 30 represented the sum of FRC, measured by tracer gas washout, and the inspiratory capacity at a Pao of 30 cm H 2 0 (Thorsteinsson A, Larsson A, Jonmarker C, et al. Pressure-volume relations of the respiratory system in
  • TLC30 -278 + 99.8 x weight
  • Figs. 2 A, B, C are graphs of the mean (SD [T]) of residual volume (RV) [0] and functional residual capacity (FRC) [o] from each infant plotted against the respective height, weight and age.
  • the straight dashed and solid lines are RV and FRC regression lines, respectively.
  • the curved dotted lines represent the 95% confidence limit.
  • RV residual volume
  • FRC functional residual capacity
  • FVC forced vital capacity from V 30
  • TLC 30 total lung capacity at a raised lung volume (V 30 ) to a Pao of 30 cm H 2 0.
  • Fig. 3 is an example trace of flow, volume, airway opening pressure (P ao ) and jacket pressure (Pj) from infant # 6.
  • inspiration is negative and expiration is positive.
  • the infant is hyperventilated by occluding the expiratory limb of the Y-adapter (Fig. 1A).
  • P ao rises to a plateau set at 30 cm H 2 O by the pressure relief valve.
  • the jacket is activated, at 14.32 s, generating a positive small sharp peak on the expiratory flow limb signaling the onset of a forced expiratory flow.
  • FIG. 4 are illustrations from patients (pt) 2, 7, and 6, respectively, and zoom on the time period that begins with jacket inflation and ends at the 20 th second of the data collection period. Each includes a trace of flow, volume, airway opening pressure (P ao ), and jacket pressure (Pj). In these illustrations, inspiration is negative and expiration is positive.
  • Jacket inflation causes a sharp rise in flow (forced expiration) and a simultaneous miniscule rise in P a0 followed by a rapid return to zero. Note in each P ao tracing the abrupt upward shift in baseline from zero to about 0.65 cm H 2 0 caused by the switching of the infant into the bias flow of oxygen. Note also a zero flow and a raised Pj plateau at the time of the switching.
  • Fig. 7 includes a trace of P ao and P j from pt 3. It zooms on the period between the switching into oxygen and ends at the 20 th second. At the time of the switching, P ao is zero -flow is also zero (not shown)- and Pj is 64.7 cm H 2 O. Note the lack of a significant post-expiratory pause.
  • the negative deflection in P a0 caused by the outward springing of the chest wall, begins at 14.1 s and merges at 14.3 s with an early more negative deflection
  • Fig. 7 illustrates the outward chest recoil induced a small negative deflection in P ao which merged with another more negative deflection of an early inspiration. Progressively larger negative deflections in P ao indicated progressively larger tidal inspirations. This patient had respiratory rate of 54 per min. Inspiratory efforts were simultaneously confirmed by observing the collapsible breathing bag.
  • Fig. 8 illustrates the nitrogen washout curve of residual volume. Note the curve rises above baseline after a latent period (9 s). The initial peak and the area under the curve are smaller than those of FRC (not shown) in the same subject. The mean period between the switching to 0 2 and the end of P j plateau was 0.301 s (Cl, 0.211, 0.391).
  • RV N 2 washout curve rose above baseline 10-15 s, vs. 1 s for FRC, after the slide valve switched the infant into pure O 2 (Fig. 8). It had a peak and an area under the curve (INS) that were smaller than those of FRC in the same subject.
  • the mean washout duration for RV was longer than FRC: 80.9 s (Cl 71.3, 90.4) vs. 72.4 s (Cl 64.9, 79.8) (p ⁇ 0.001).
  • the intrasubject washout duration was mostly within 10 s.
  • Figs. 9A, B, and C illustrates the mean (SD [T]) of forced vital capacity (FVC) [ ⁇ ] and mean total lung capacity at a raised lung volume to an airway opening pressure of 30 cm H2O (TLC30) [•] from each infant are plotted against the respective height, weight and age.
  • the straight dashed and solid lines are FVC and TLC30 regression lines, respectively.
  • the curved dotted lines represent the 95% confidence limit.
  • the mean FVC was 40.2 ml/kg (Cl 33.0, 47.3) and TLC30, 61.5 ml/kg (Cl 54.4, 68.7).
  • FVC and TLC30 exhibited a strong age, height and weight dependence as indicated by the coefficient of determination (r 2 ) (Table 2, Fig. 9).
  • the mean percent predicted TLC 3 0 was 90% (Cl 81, 99) (Table 1).
  • Fig. 10 shows the influence of the collapsible breathing bag (BB) on gas flow in the N 2 mixing chamber during in vitro washout.
  • BB collapsible breathing bag
  • N 2 washout curve of RV had a smaller peak and area under the curve (INS) than FRC's because of the initial small tidal volumes following the apnea and the inherently smaller volume of RV (Fig. 8).
  • the system can be mobilized to perform bedside measurements.
  • the dead space and apparatus resistance are low in the open N 2 washout, making it suitable for small or sick infants.
  • the author has performed a painstaking systematic exploration of possible sources of error when using the N 2 washout.
  • tidal breathing indices namely the tidal volume, the inspiratory, expiratory and total time as well as the frequency (FT, tl , tE ,ttot , and/(Hz), respectively
  • FVC may be smaller than a slow vital capacity in obstructive airway disease, it is possible that a small TLC was obtained in some of our patients because we used FVC (Hyatt R, Scanlon PD, Nakamura M. Interpretation of pulmonary function tests- A practical guide. Philadelphia: Lippincott-Raven, 1997:31.).
  • RV, FRC, FVC and TLC 30 correlated with the age, height and weight of patients (Figs. 2 and 9; Table 2).
  • a previous study found no correlation between age and thoracic gas volume or maximal expiratory flow at functional residual capacity in a group of infants with CF (Beardsmore CS, Bar-Yishay E, Maayan C, et al. Lung function in infants with cystic fibrosis. Thorax 1988; 43, 545-51.).
  • RV has been measured invasively or with an unacceptable reproducibility (AT/ERS, 1993).
  • Commercially available infant pulmonary function equipment is not designed to measure RV. I have two separate infant systems that were used in unison to perform the measurement. RV measurements were very reproducible, mostly within 5%, and in five patients, 2%. In each infant, measurements of RV and FRC were reproducible and did not overlap even in the presence of a significant airway obstruction or tachypnea. I anticipate RV measurements will be routinely done in every infant pulmonary lab in the world. The measurements of RV, TLC 3C and FRC will provide the most comprehensive assessment of lung volumes in infants, in health and disease, from birth until three years. I think lung growth can be more reliably assessed by RV and TLC 30 than FRC alone. The ratio of RV/TLC30 is important in studying air trapping in the lung, as is the case in older childred and adults, in diseases such as bronchopulmonary displasia in infants born prematurely and cystic fibrosis.

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Abstract

L'invention concerne un appareil permettant de mesurer le volume résiduel (RV) des poumons chez les jeunes enfants par élimination de l'azote ou d'un autre gaz inerte, à l'aide d'un gilet de compression permettant une compression thoracoabdominale rapide (RTC). La RTC est exécutée à partir d'un volume pulmonaire (V30) dilaté à une pression d'ouverture aérienne de 30 cm H2O. La pression de gilet (Pj) (plage de 65-92 cm H2O) qui produit le volume d'expiration forcée le plus grand est utilisée pendant la modification de RV. Le jeune enfant est hyperventilé manuellement de façon à inhiber brièvement l'activité respiratoire. On calcule RV par mesure du volume d'azote expiré après une expiration forcée jusqu'au bout, qui permet de substituer le gaz inspiré à partir d'un mélange respirable contenant un gaz inerte par 100 % d'oxygène, tout en maintenant RTC pendant la pause post-expiratoire.
PCT/US2000/004044 1999-02-19 2000-02-17 Technique permettant de mesurer le volume residuel des poumons chez les jeunes enfants WO2000048513A1 (fr)

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