Airflow Measurements Research Articles

Objective nasal airflow measures in relation to subjective nasal obstruction, trigeminal function, and olfaction in patients with chronic rhinosinusitis.

This study aimed to determine how nasal airflow measures and trigeminal function vary among patients with chronic rhinosinusitis (CRS) versus healthy controls and whether these measures are correlated with subjective nasal obstruction (SNO), olfactory function, and CRS control. Participants included CRS patients and healthy controls. After a structured medical history, nasal airflow (peak nasal inspiratory flow [PNIF]; active anterior rhinomanometry [AAR]), trigeminal function (trigeminal lateralization test, CO2 sensitivity), and olfactory "Sniffin's Sticks" odor identification test) tests were performed. SNO ratings were also obtained. Sixty-nine participants were included (37 men, 32 women, mean age 51 years). There was no significant difference for objective nasal airflow between patients and controls, but CRS patients had worse SNO, trigeminal function, and olfaction compared to controls. SNO, but not objective nasal airflow tests, was negatively correlated with CO2 sensitivity and odor identification. The perception of nasal obstruction does not only depend on nasal airflow, but may also be modulated by trigeminal function and other factors. Thus, the role of objective nasal airflow measures as a sole method of functional nasal obstruction assessment in CRS remains limited.

Pitot Tube Sensor Probe System for Simultaneous Airflow and Pressure Measurement of Expiration Inside Pulmonary Airway

Respiratory diseases, including the cronic obstructive pulmonary disease (COPD) are among the leading causes of death worldwide. To date, there is no physical examination procedure that can quantify important parameters within a specific lesion area inside the lung. In this study, we propose a novel sensor probe system consisting of a basket forceps and 2 pressure sensors to simultaneously measure the expiratory airflow and the static pressure inside the pulmonary airway. A Pitot tube mechanism using 2 pressure sensors is introduced in the system for measuring both the physical quantities. Small fiber‐optic pressure sensors with 0.3 mm diameter were utilized, and both the airflow rate and the static pressure characteristics were evaluated for obtaining the calibration curves. Finally, the proposed sensor system was implemented to measure both the airflow and pressure in an artificial ventilator and an experimental animal. The measurement of expired airflow and static pressure inside the airway of a rat with the diameter of 1.8 mm were demonstrated. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Design and Performance Evaluation of an Air Flow Meter for Drying Cassava Chips

Drying is an important unit operation in the processing of fresh cassava tubers into cassava chips. An air flow meter is a device that measure airflow. Airflow meter and direction sensing are importance in many fields, including the monitoring on vehicle engine performance. The airflow meter for cassava chips measures how much air is flowing through the cassava chips. There are many reasons and ways to measure airflow, this technical method of explores the use of air flow meter to measure cassava chips in order to ensure the proper airflow to dry the cassava chip, which will improve the value chain of cassava processing. This research work focused on the design and performance evaluation of an airflow meter for drying cassava chips. The air flow meter was made from locally available materials and it consists of a blower, pressure, sensor, temperature sensor, heating chamber which was used to carry out several tests on cassava chips. From the test conducted during drying operation, at a temperature of 900c for a 372g of cassava chips, it takes a period of 180 minutes (3hours) with an airflow of 133m3/sec to dry it to a safe moisture content. At temperature 1100c for 617g of cassava chips, it takes a period of 240 minutes (4hours) with an airflow of 209m3/sec to dry it to safe moisture content. The efficiencies of the drying mechanism and measuring airflow device are 70% and 65% respectively. The sample dried with airflow meter still retain their white colours, thus indicating no mould growth.

The Sub-Metered HVAC Implemented for Demand Response Dataset

Abstract Closed-loop control of commercial building heating, ventilating, and air conditioning (HVAC) for demand response requires measurements used as feedback to the controllers. Demand response effectiveness is usually measured as a power deviation from baseline, but the building automation system (BAS) does not usually collect power measurements, and whole-building electric meters typically measure power at intervals of 15 min, which may be too slow for some types of demand response. Demand response strategies are sometimes focused on components of building HVAC systems, e.g., the response of supply/return fans to temperature set-point changes, but these components are usually not submetered. Fan power can be estimated from physics-based models leveraging BAS data, e.g., airflow measurements; but our ability to effectively close the loop on these estimates is not clear. In this paper, we introduce a massive dataset that contains both submetered fan power data and BAS data for several building HVAC systems during typical operation and demand response events. Through a case study we show that models leveraging BAS data alone do not provide accurate estimates of fan power during event transients, making it unlikely that closed-loop control of commercial building HVAC components for demand response would be effective using BAS data alone. This demonstrates the value of submetering HVAC components. More broadly, our dataset will enable future research bridging the gap between building control and power systems research.

Validation of urban airflow measurements through a combined field test and wind tunnel study

Validation of urban airflow measurements through a combined field test and wind tunnel study

SIMULATION OF MUFFLER PARAMETERS IN VENTILATION CHANNELS OF VENTILATORS

During long-term observation of the operation of the ventilator (artificial lung ventilation) of the UVENT-T model, a violation of repeatability was noticed under the same operating conditions. That is, on some devices of this particular model, the air flow sensor under the same conditions showed different values when repeating the measurements.Through experiments, it was established that this is caused by the unevenness of the air flow inside the ventilation channels of the ventilator, which is most likely caused by the design of the silencers installed there.The article highlights the process of research and modeling of air flow in ventilation channels of ventilators of the apparatus due to the manufacture of several test variants of muffler designs, which should solve the problem of various deviations of flow measurements. The main idea was to change the number and size of the muffler holes. Obviously, the 5 holes of 2 mm scattered the air flow too much, due to which there was an increased risk of turbulence in the air flow, which could have caused the unevenness of its measurements. Therefore, on all new mufflers, the holes were reduced to1 mm, but their number was increased by 2 times. In total, 6 design options were obtained. All 6 options were designed in CAD SolidWorks, and flow simulation was also carried out for test models. According to the results of air flow measurements, graphic dependencies were obtained for each of the silencer samples, namely the integral of the absolute error of the flow measurement, the integral of the flow noise power, the integral of the acoustic noise power and the maximum absolute error of the flow measurement.In the future, it is proposed to develop a mathematical model of laminar air flow in a ventilator taking into account new designs of silencers, as well as to develop software for testing according to the developed algorithm and model. Conduct experimental testing of designed mufflers, as well as evaluate the results of the experiment. According to the research results, a conclusion will be made about the most effective muffler design, and its design will be used inthe production of ventilators.

Design and fabrication of a simple and cost-effective optical flow meter using liquid crystals and textile grid.

The measurement of airflow velocity is crucial in various fields, and several sensing approaches have been developed for detecting airflow, including optical fiber-based flowmeters. However, these sensors often require complex fabrication processes and precise optical alignment. In this paper, a simpler and more cost-effective approach has been used to measure air flow rate by utilizing the birefringence property of liquid crystals (LCs). LCs possess distinct optical characteristics, and their reorientation due to airflow can be detected by observing the intensity of the output light between crossed polarizers. The novelty of this study is the utilization of a textile grid to hold the LC layer, which simplifies the fabrication process. This LC-based gas flowmeter offers a simple, low-cost setup and provides rapid performance. This research presents what we believe to be a new approach to calculate airflow by exploiting the optical properties of LCs, which is a new frontier in gas flow measurement. The proposed airflow meter is capable of detecting airflow rates ranging from 0 l/min to 7.5 l/min with an accuracy of 0.5 l/min. It exhibits a stable response time in 75 seconds, and the sensor maintains acceptable stability over time.

Density measurement of supersonic airflow using decay characteristics of FLEET emission

Density measurement of supersonic airflow using decay characteristics of FLEET emission

Assessment of professional singers using laryngeal, respiratory, and airflow measurements

Purpose In the pedagogy of classical vocal singing, it can be difficult to determine the human voice fach, especially for the voice of aspiring vocalists. Hence, an objective metric-based system for the determination of the human voice is needed. In the present study, we investigated the anthropological and aerodynamic parameters for 60 professional singers with a professionally confirmed singing range. Methods Amongst the 60 included professional singers, there were ten participants each for sopranos, mezzo-sopranos, altos (female vocal fach), and tenors, baritones, basses (male vocal fach). Airflow measurements were recorded using spirometry whilst anthropological measurements were taken using CT scans. Appropriate statistical analyses were done using the Mann-Whitney U test and Kruskal Wallis H test with post-hoc tests and Bonferroni correction. p < 0.05 was considered statistically significant. Results Soprano singers, who have the highest pitch, were found to be the shortest and least heavy, whilst basses, who have the lowest pitch, were found to be tallest and heaviest amongst the study participants. Furthermore, sopranos had the smallest lung volumes while the basses had the largest lung volumes (raw spirometry measures). However, when normalized ratios were considered, no differences were observed. Finally, laryngeal size showed sexual dimorphism due to developmental changes. Conclusions A mix of anthropological and aerodynamic measurements may be useful to assist singers and vocal pedagogues to assess and determine voice types before the beginning of their vocal studies.

Effect of body position on peak expiratory flow during mechanical insufflation–exsufflation in people with cervical spinal cord injury: a pilot study

This prospective pilot study investigated the influence of body position on peak cough flow (PCF) during mechanical insufflation–exsufflation (MI-E) treatment in people with tetraplegia. Fifteen participants with cervical spinal cord injury (C-SCI) were randomized into two groups, which differed in the starting position, that is, the patients were either supine or reclined. Four sessions of MI-E in alternating positions with each session comprising three different maneuvers: five voluntary coughs, five MI-E-assisted coughs, and five MI-E-assisted with manual thrusts were performed with continuous airflow measurement reporting PCF from every cough. PCF was associated with the application maneuvers, total insufflation volume (TIV), and interaction between position and maneuvers but not with the application position. The estimated mean PCF was 1.808, 3.529, and 3.925 L/s when supine and 1.672, 3.598, and 3.909 L/s when reclined from voluntary cough, MI-E, and MI-E with manual thrust, respectively. The estimated PCF change compared to voluntary cough was 1.721 (95% CI, 1.603–1.838) L/s from the combined MI-E and 2.116 (95% CI, 2.005–2.228) L/s from the MI-E with manual thrust, calculated from the linear mixed-model analysis. PCF moderately correlated with TIV (R2 = 0.64). Therefore, either position can be used for C-SCI patients as long as MI-E can be performed with manual thrust and sufficient TIV is provided.

Evaluation of three approaches used for respiratory measurement in healthy subjects

Objective. Respiration is one of the critical vital signs of human health status, and accurate respiratory monitoring has important clinical significance. There is substantial evidence that alterations in key respiratory parameters can be used to determine a patient’s health status, aid in the selection of appropriate treatments, predict potentially serious clinical events and control respiratory activity. Although various approaches have been developed for respiration monitoring, no definitive conclusions have been drawn regarding the accuracy of these approaches because each has different advantages and limitations. In the present study, we evaluated the performance of three non-invasive respiratory measurement approaches, including transthoracic impedance (IMP), surface diaphragm electromyography-derived respiration (EMGDR) and electrocardiogram-derived respiration (ECGDR), and compared them with the direct measurement of airflow (FLW) in 33 male and 38 female healthy subjects in the resting state. Approach. The accuracy of six key respiratory parameters, including onset of inspiration (Ion ), onset of expiration (Eon ), inspiratory time (It ), expiratory time (Et ), respiratory rate (RR) and inspiratory–expiratory ratio (I:E), measured from the IMP, EMGDR and ECGDR, were compared with those annotated from the reference FLW. Main results. The correlation coefficients between the estimated inspiratory volume and reference value were 0.72 ± 0.20 for IMP, 0.62 ± 0.23 for EMGDR and 0.46 ± 0.21 for ECGDR (p < 0.01 among groups). The positive predictive value and sensitivity for respiration detection were 100% and 100%, respectively, for IMP, which were significantly higher than those of the EMGDR (97.2% and 95.5%, p < 0.001) and the ECGDR (96.9% and 90.0%, p < 0.001). Additionally, the mean error (ME) for Ion , Eon , It , Et and RR detection were markedly lower for IMP than for EMGDR and ECGDR (p < 0.001). Significance. Compared with EMGDR and ECGDR, the IMP signal had a higher positive predictive value, higher sensitivity and lower ME for respiratory parameter detection. This suggests that IMP is more suitable for dedicated respiratory monitoring and parameter evaluation.

Comparison of model-driven soft measurement methods for compressor air flow in gas-steam combined cycle power units

The determination of the air flowrate at the compressor inlet is meaningful for the performance diagnosis of heavy-duty gas turbine combined cycle (GTCC) power units, whereas the compressor air flow generally cannot be directly obtained from the field data. In this paper, the procedures of three model-driven methods for soft measurement of compressor air flow were presented, including energy balance of the coupled HRSG (M1), static pressure at the compressor manifold (M2) and gas turbine joint operation line method (M3). In the case of a M701F4 GTCC power unit, the methods M1 and M3 were validated by the field and testing data; while the method M2 was calibrated and the effective area at the air manifold was decided as 12.606 m2 using M1 at the full load of gas turbine. The compressor air mass flow at overall loads was computed with the various methods. The comparative investigation to these methods shows that, the compressor inlet air flow is determined as 682.75 kg/s by M1 and 664.07 kg/s by M3, respectively, at the full load and at the ambient temperature 29.912 °C. The air flow obtained by M1 and M2 appears relatively higher than that by M3 at typical various loads of gas turbine; however, the method M3 shows a good accordance with the actual value of the air flow for turbine rotor cooling. Both M2 and M3 agree in the theoretical demonstration that compressor air flow is strongly related to the gas turbine load at certain conditions. The method M1 can be deemed as a reference for another two methods in the case of the steady operating state at full load; whereas it is not recommendable for the real-time measurement of compressor air flow, because of the large amounts of required input variables and the fluctuation in the flow meters.

Breathing pattern disorder in chronic rhinosinusitis with severe asthma: nasal obstruction and polyps do not increase prevalence

Objectives Chronic rhinosinusitis (CRS) with severe asthma are associated with breathing pattern disorder (BPD). Mouth breathing is a sign of breathing pattern disorder, and nose breathing a fundamental part of breathing pattern retraining for BPD. The prevalence of BPD in relation to CRS subtypes and the relationship of nasal obstruction to BPD in CRS and associated severe asthma is unknown. The breathing pattern assessment tool (BPAT) can identify BPD. Our objective was to thus investigate the prevalence of BPD, nasal airflow obstruction and measures of airway disease severity in CRS with (CRSwNP) and without nasal polyps (CRSsNP) in severe asthma. Methods We determined whether CRS status, peak nasal inspiratory flow (PNIF) or polyp disease increased BPD prevalence. Demographic factors, measures of airway function and breathlessness in relation to BPD status and CRS subtypes were also evaluated. Results 130 Patients were evaluated (n = 69 had BPD). The prevalence of BPD in CRS with severe asthma was 53.1%. There was no difference between BPD occurrence between CRSwNP and CRSsNP. The mean polyp grade and PNIF were not statistically different between the BPD and non-BPD group. The presence of nasal polyps did not increase breathlessness. Conclusions BPD and CRS are commonly co-associated. CRS status and nasal obstruction per se does not increase BPD prevalence.

Experimentally Validated Neural Networks for Sensors Redundancy Purposes in Spark Ignition Engines

&lt;div&gt;In the aeronautical field, aircraft reliability is strictly dependent on propulsion systems. Indeed, a reliable propulsion system ensures the safety of pilots and passengers and the possibility of making comfortable flights. Typically, on aircraft equipped with spark ignition (SI) engines, one of the principal requirements to make them reliable is the correct balancing between the intake air mass and fuel flows. Advances in the implementation of sophisticated control and estimation strategies on SI engines allow realizing engines with improved features in terms of performance, reducing pollution emissions, and fuel consumption. Approaches based on sensor redundancy are applied to improve the reliability in measurements of the manifold air pressure (MAP) and flow (MAF) to avoid issues related to possible faults of sensors vital for the correct functioning of SI engines. Model-based estimation techniques, based on the speed–density and alpha-speed methods for determining the MAF in engine control units, are employed to obtain sensor-less redundancy. The prediction of MAP and MAF, for sensors redundancy purposes, can be made through neural networks, allowing the avoidance of effects due to unmodeled dynamical behaviors. A sensor redundancy approach based on feedforward neural networks (FNNs) is proposed in this work for MAP and MAF prediction of a SI engine. The present work focuses on the possibility of estimating the physical quantities related to SI engines, such as the MAP and the MAF, fundamental for their monitoring using neural networks trained by means of a model-based approach avoiding expensive experimental tests for producing training data. A well-known intake manifold dynamical model (IMDM), parametrized based on the CMD 22 aeronautical engine, is employed for generating synthetic training data in steady-state conditions functional for making the chosen FNNs able to predict both MAP and MAF even in transient behavior.&lt;/div&gt; &lt;div&gt;The MAP and MAF are predicted through two virtual sensors based on two independent FNNs, having the same inputs, constituted by the engine speed and the throttle angle. An experimental investigation based on an aircraft endurance test of two hours proposed by the European Aviation Safety Agency (EASA) has been made on a controlled and monitored CMD 22 engine for comparing the experimentally measured MAP and MAF with the predicted ones by the FNNs. The results demonstrate the suitability of the proposed approach for sensor redundancy purposes in SI engines to increase their reliability.&lt;/div&gt;

Comparison of ventilation rate according to the lengths of air flow measurement device for measuring the ventilation rate from a pig barn

Comparison of ventilation rate according to the lengths of air flow measurement device for measuring the ventilation rate from a pig barn

Thermal imaging and velocity measurements of the exhaled airflow in total laryngectomized patients during COVID-19 pandemic.

In patients after total laryngectomies, the trachea and the lung can be easily infected by SARS-CoV-2 because the respiration happens through the tracheostoma. The aim of our study was to examine whether patients with LaryTube™ can distribute aerosols to a greater extent than without LaryTube™, and to observe whether the surface of different protective instruments can be examined using the thermal camera in total laryngectomees. An important objective was also to confirm the assumption that the use of HME (heat and moisture exchanger) alone does not provide protection during COVID-19 pandemic. Finally, during our tests, we tried to get an answer to our assumption that the sample taken from the inner surface of the HME can be tested for SARS-CoV-2. A total of 23 patients who underwent total laryngectomies were analyzed by velocity measurements and thermal imaging with and without HMEs and laryngeal tubes, using different types of PPEs. COVID-19 PCR testing was performed on patient tracheas and the inner surfaces of the HMEs. Male patients with laryngeal tubes without HMEs demonstrated an increase in exhaled airflow velocity of more than 43% compared to male patients without laryngeal tubes; in female patients, the same value was more than 39%. Thermal imaging results confirmed that the lowest surface temperature was measured on FFP2 masks. The sent samples can be tested for SARS-CoV-2 using PCR, the presence of the virus was not detected. Laryngectomized patients without laryngeal tubes pose a lower risk for spreading viral aerosols due to the reduced velocity of the exhaled airflow caused by the absence of the tube as the narrowing factor. Patients with laryngeal tubes who undergo total laryngectomies during the COVID-19 pandemic should use HMEs with viral filter, if possible, also changing the laryngeal tubes to dermal adhesives for fitting their HMEs seems to be the best option. The surface of the used protective equipment can also be examined with thermal camera in the case of total laryngectomees. COVID-19 PCR testing of the tracheal secretion from the inner HME surfaces should become a routine in clinical practice if deemed necessary. Orv Hetil. 2023; 164(34): 1327-1336.

Nasal IL-13 production identifies patients with late-phase allergic responses

There is limited knowledge on how local cytokine secretion patterns after nasal allergen challenge correlate with clinical symptoms especially with regard to the "late allergic response," which occurs in approximately 40% to 50% of patients with allergy. We sought to characterize the immunologic and clinical nasal responses to birch pollen allergen challenge with a special focus on the late allergic response. In this randomized, double-blind, placebo-controlled trial, birch pollen-allergic participants were challenged with birch pollen extract (n= 20) or placebo (n= 10) on 3 consecutive days. On days 1 and 3, nasal secretions were collected at selected time points over a 24-hour time course for the measurement of 33 inflammatory mediators. Clinical responses were determined through subjective symptom scores and objective nasal airflow measurements. Provoked participants had significantly greater clinical responses and showed significant increases in tryptase and the soluble IL-33 receptor serum stimulation 2 (sST2) in nasal secretions within minutes compared with the placebo group. Eight of 20 provoked participants displayed high IL-13 levels 2 to 8 hours after allergen provocation. This group also showed significant changes in clinical parameters, with a secondary drop in nasal airflow measured by peak nasal inspiratory flow and increased symptoms of nasal obstruction, which significantly differed from IL-13 nonresponders after 6 hours. IL-13 response status correlates with clinical responses and type 2 cytokine responses in the late phase after allergen provocation.

Nasalance, Nasal Airflow and Perceived Nasality in Carnatic Singers and Non-singers.

This study aims to compare the nasalance and nasal airflow between professional singers trained in Carnatic classical singing and non-singers. We also aimed to correlate perceived nasality with objective measurements of nasalance and nasal airflow. A total of 40 female participants (20 to 50years) were involved in this study. The first group comprised 15 female professional Carnatic singers with a minimum of 10years of classical training. The second group consisted of 25 non-singer females. These participants were compared on nasalance, nasal airflow and perceived nasality across three sets of stimuli (vowels, oral non-words, and nasal non-words) and three pitch-conditions (low, mid, and high). Correlations were also made between objective measures of nasalance and nasal airflow and perceived nasality. Mixed ANOVA showed a significant (P < 0.05) interaction in nasalance between pitch conditions and groups. Group differences were also observed in the nasalance scores of vowels, oral non-words, nasal non-words. There was a significant difference (P < 0.05) in nasalance with ascending pitch in singers and non-singers. A comparison of aerodynamic analysis of vowels, oral non-words, and nasal non-words between singers and non-singers suggested that nasal airflow was higher in singers. Perceptual nasality was significantly lower (P < 0.05) in Carnatic singers than non-singers. Correlations between objective measures of nasalance and nasal airflow and perceived nasality were not observed. Despite an increased airflow, nasality was lower in trained Carnatic singers than non-singers. Current findings suggest that vocal training impacts nasalance, nasal airflow and perceived nasality.

A Pilot Study of the Effect of a Non-Contact Boxing Exercise Intervention on Respiratory Pressure and Phonation Aerodynamics in People with Parkinson's Disease.

Eight adult males diagnosed with Parkinson's disease participated in the study. Individuals participated in twice-weekly exercise classes lasting one hour across 12-months. Dependent variables were measured on three baseline days and then at six additional time points. A pressure meter acquired maximum expiratory pressure, and a pneumotachograph system acquired transglottal airflow and subglottal air pressure. Measures of average maximum expiratory pressure significantly increased after 9- and 12- months of exercise when compared to baseline. There was an increasing trend for these measures in all participants, with a corresponding large effect size. Measures of transglottal airflow and subglottal pressure did not change over the course of 9- or 12-months, although their stability may indicate that the exercise program influenced maintenance of respiratory-phonatory coordination during voicing. A non-contact boxing exercise program had a significant effect on maximum expiratory pressure in people with Parkinson's disease. The aerobic nature of the program and challenges to the respiratory muscles potentially explain the "ingredient" causing this effect. The small sample size of this pilot study necessitates future research incorporating larger and more diverse participants.

Expiratory airflow at 7–8 years of age in children born extremely low birthweight from 14 years before to 14 years after the introduction of exogenous surfactant

It is unclear if expiratory airflow in survivors born extremely low birth weight (ELBW; 500-999g) has improved after the introduction of exogenous surfactant into clinical practice in 1991. The primary aim of this study was to describe the changes in airflow at 7-8 years of age of survivors born ELBW in five discrete cohorts from 14 years before to 14 years after the introduction of exogenous surfactant into clinical practice. The cohorts comprised consecutive survivors born ELBW in 1977-82 and 1985-87at the Royal Women's Hospital, Melbourne, and in 1991-92, 1997 and 2005 in the state of Victoria, Australia. Survival rates to 2-years of age for infants born ELBW in the state of Victoria rose from approximately 1-in-4 to 3-in-4 over the time of this study. Expiratory airflow measurements at 7-8 years included the forced expired volume in 1s (FEV1), converted to z-scores for age, height, sex, and race. There were 596 ELBW participants with expiratory flow data, 280 (47%) of whom had bronchopulmonary dysplasia (BPD). Overall, there was little change in zFEV1 over the 28-year period (mean change per year; 0.003, 95% CI-0.010, 0.015, P=0.67). There was, however, evidence of an interaction between BPD and year; zFEV1 in those who had BPD fell over time (mean change per year-0.019, 95% CI-0.037,-0.009, P=0.035), whereas zFEV1 improved in those who did not have BPD (mean change per year 0.021, 95% CI 0.006, 0.037, P=0.007). Contrary to recent evidence, expiratory airflow of children born ELBW has not improved with the introduction of surfactant, and may be deteriorating in those who had BPD. National Health and Medical Research Council (Australia); Victorian Government's Operational Infrastructure Support Program.