Tidal Breathing Flow-volume Loops Research Articles

Dose-dependent impact of human milk feeding on tidal breathing flow-volume loop parameters across the first 2 years of life in extremely low-birth-weight infants: a cohort study.

Preterm infants with higher consumption of HM had significantly less airway obstruction across the first 2 years, suggesting that human milk may contribute in a dose-dependent manner to improve lung function in early childhood in former preterm infants born ELBW. • Human milk feeding reduces the risk of prematurity-related morbidities, including necrotizing enterocolitis, sepsis, lower respiratory tract infections, and BPD. Both exclusive and partial human milk feeding appear to be associated with a lower risk of BPD in preterm infants. • This cohort study of 180 preterm infants with birth weight < 1000 g found that exposure to human milk during hospitalization improves airway obstruction markers tPTEF/tE z-score over the first 2 years of corrected age in a dose-dependent manner.

In utero exposure to poly- and perfluoroalkyl substances and children respiratory health in the three first years of life

BackgroundPoly- and perfluoroalkyl substances (PFAS) are used in a wide range of products. Experimental studies suggested impaired lung development and pro-inflammatory response following exposure to some PFAS. We aimed to assess the associations between prenatal exposure to PFAS and children respiratory health. MethodsThe study is based on 433 mother-child pairs. 26 PFAS were measured in maternal serum collected during pregnancy. Lung function parameters were measured at 2 months using tidal breathing flow-volume loops and multiple-breath nitrogen washout and at 36 months using oscillometry. Incidence of respiratory health diseases (asthma, wheeze, bronchitis, bronchiolitis) in the first 36 months of life was assessed by repeated questionnaires. A cluster-based analysis was applied to identify prenatal PFAS exposure patterns. Adjusted linear and logistic regressions were performed to assess the associations between PFAS exposure patterns as well as individual PFAS, and each respiratory health parameter. ResultsWe excluded 13 PFAS due to low quantification (<5%). Relying on the 13 remaining PFAS, we identified three exposure clusters, characterized by low (N = 163), medium (N = 236) and high (N = 51) pregnancy PFAS concentrations. Compared to children belonging to the low exposure group, children in the moderate exposure group had higher reactance at 7 Hz (X7) and lower frequency dependence of resistance between 7 Hz and 19 Hz (R7-19) at 36 months, suggesting better lung function. No association of any exposure metric was detected with respiratory diseases in the first 3 years of life. ConclusionsOur study relying on both mixture and uni-pollutant analyses, does not provide evidence for a deleterious effect of prenatal PFAS exposure on respiratory health at an early age.

Prenatal exposure to synthetic phenols and phthalates and child respiratory health from 2 to 36 months of life

Exposure to phthalates and synthetic phenols is ubiquitous. Some of them are suspected to impact child respiratory health, although evidence still remains insufficient. This study investigated the associations between prenatal exposure to phthalates and phenols, individually and as a mixture, and child respiratory health assessed by objective lung function measures since 2 months of age. Among 479 mother-child pairs from the SEPAGES cohort, 12 phenols, 13 phthalate and 2 non-phthalate plasticizer metabolites were measured in 2 pools including each 21 urine samples collected at the 2nd and 3rd pregnancy trimesters. Lung function was measured at 2 months using tidal breathing flow-volume loops and nitrogen multiple-breath washout, and at 3 years using oscillometry. Asthma, wheezing, bronchitis and bronchiolitis were assessed by repeated questionnaires. A cluster-based analysis was applied to identify exposure patterns to phenols and phthalates. Adjusted associations between clusters as well as each individual exposure biomarker and child respiratory health were estimated by regression models. We identified four prenatal exposure patterns: 1) low concentrations of all biomarkers (reference, n = 106), 2) low phenols–moderate phthalates (n = 162), 3) high concentrations of all biomarkers except bisphenol S (n = 109), 4) high parabens–moderate other phenols–low phthalates (n = 102). At 2 months, cluster 2 infants had lower functional residual capacity and tidal volume and higher ratio of time to peak tidal expiratory flow to expiratory time (tPTEF/tE) and cluster 3 had lower lung clearance index and higher tPTEF/tE. Clusters were not associated with respiratory health at 3 years but in the single-pollutant models, parabens were associated with increased area of the reactance curve, bronchitis (methyl, ethyl parabens) and bronchiolitis (propyl paraben). Our results suggested that prenatal exposure to mixtures of phthalates reduced lung volume in early life. Single exposure analyses suggested associations of parabens with impaired lung function and increased risk of respiratory diseases.

From neonatal lung function to lung function and respiratory morbidity at 6-year follow-up.

Lung function is traceable from infancy to adulthood. Only a few studies have examined lung function from birth to childhood longitudinally in children born moderate to late preterm. We aimed to investigate how prematurity and lung function in the neonatal period are related to lung function and respiratory morbidity at age 6in former moderate to late preterm children compared with children born at term. Lung function was measured in a cohort of moderately to late preterm (n = 48) and term-born (n = 53) infants in the neonatal period by FeNO, and tidal breathing flow-volume loops (TBFVL) and at age 6(n = 52) by spirometry, whole-body plethysmograph and impulse oscillation combined with a respiratory symptom questionnaire. Moderate to late preterm children had a higher TPEF /TE ratio neonatally (42.6% vs. 33.7%, p = 0.02) and a lower % predicted orced expiratory volume in the first second at age 6(94.4% vs. 101.9%, p = 0.01) compared to term-born children. We found a significant association between the variability of neonatal tidal volume and effective airway resistance at age 6 (β = -0.34, p = 0.03). No association between neonatal FeNO or TBFVL and respiratory morbidity at 6-year follow-up was shown. Children born moderate to late preterm had lower lung function at age 6 than term-born children. We did not find evidence for the use of neonatal tidal breathing parameters as a predictor for subsequent respiratory morbidity or lung function, however sample size was small.

Effect of human milk and other neonatal variables on lung function at three months corrected age

To evaluate the impact of human milk and different neonatal variables on tidal breathing flow-volume loop (TBFVL) parameters within three months' corrected age (CA) in infants born ≤32 wks or weighing <1500 g. We retrospectively studied 121 infants with gestational age (GA) ≤ 32 weeks or birth weight (BW) <1500 gr who had lung function assessment within three months' CA by TBFVL analysis between June 2009 and April 2018. We investigated the impact of GA, gender, being Small for GA (SGA), sepsis, days of mechanical ventilation (MV) and human milk feeding (HMF) on later respiratory function, both in the entire group and according to BW ( ≤1000 g and >1000 g). The mean(SD) z-score for tidal volume (Vt) and time to peak expiratory flow to expiratory time (tPTEF/tE) were respectively -4.3 (2.5) and -0.8 (2.0) for the overall population with no significant differences between infants <1000 g or ≥1000 g. The mean(SD) Vt standardized for body weight was 6.2(2.0) ml/kg. Being female was associated with better Vt/Kg, whereas longer MV or being born SGA were associated with worst tPTEF/tE. For infants with BW < 1000 gr, tPTEF/tE was positively associated with HMF. An early TBFVL assessment within three months' CA already reveals lung function alteration in preterm infants. Being female is associated with better Vt/Kg, while longer duration of MV or being born SGA negatively affect tPTEF/tE. The positive association between HMF and better tPTEF/tE in infants with BW <1000 g has emerged, which deserves further investigation.

Effect of acute respiratory infections in infancy on pulmonary function test at 3 years of age: a prospective birth cohort study

IntroductionAcute respiratory infections (ARIs) in infancy may have a long-term impact on the developing respiratory system. We planned a prospective cohort study to determine the impact of ARI during infancy...

Normative Data of Infant Pulmonary Function Testing: A Prospective Birth Cohort Study from India

To develop a normal reference range of Infant pulmonary function test (IPFT) indices for Indian children. Prospective birth cohort study. Division of Pediatric Pulmonology of a tertiary-care institute in India from August 2012 to March 2017. All neonates born at the institute during the study period were screened for eligibility. IPFT at baseline and every 6-month until 36-months of age. Tidal breathing flow-volume loop (TBFVL), Rapid thoracoabdominal compression (RTC), and Raised volume RTC (RVRTC) indices at baseline and follow-up. 310 newborns were enrolled in the cohort; 281 of them (169 male) had completed 36-months of follow-up at the end of the study period. There was no influence of gender on the baseline IPFT indices. Tidal volume per unit body weight (VT/kg) significantly increased from baseline to 36 months of age (P<0.001) while the peak ratio (tPTEF/tE) initially decreased in first 18-months of age (P<0.001), after that returned to the baseline value by 36 months of age. RTC indices did not change significantly from baseline values. In RVRTC, the ratio of forced expiratory volume in 0.5s to forced vital capacity (FEV0.5/FVC) was significantly decreased from baseline to 36 months of age (P=0.002). Normal values for various IPFT indices for TBFVL, RTC, and RVRTC from neonates to the age of 36-month are provided. These data may be used as normative data for healthy neonates and children of Indian origin.

Small for gestational age birth may increase airflow limitation in bronchopulmonary dysplasia.

To determine significant indices for assessing the pulmonary function of infants according to bronchopulmonary dysplasia (BPD) severity and to evaluate whether small for gestational age (SGA) could affect pulmonary function in BPD. We evaluated 117 preterm infants who had undergone tidal breathing flow-volume loop and multiple-breath washout analyses within 7 months after birth. We categorized preterm infants according to BPD severity into mild/moderate BPD (n = 86), severe BPD (n = 21), and without BPD (n = 10) and the presence of SGA or appropriate gestational age (AGA) using the Fenton growth chart. We evaluated nine healthy term infants as controls. The tidal breathing ratio (time to peak expiratory flow/expiratory time [tPEF /tE ]) was significantly lower in infants with severe BPD than in those with mild/moderate BPD. Lung clearance index (LCI) was not different based on BPD severity. In the correlation analysis after adjusting for gestational age and sex, tPEF /tE was correlated with the duration of mechanical ventilation (r = -0.347, P < .001) and the duration of oxygen supply (r = -0.248, P = .013) in infants with BPD. The proportion of "lower tPEF /tE ," defined as below the cut-off value, was greater in SGA infants (P = .017), while no significant difference was seen in the percentage of "higher LCI," defined as above the cut-off value between SGA and AGA infants. In infants with BPD, tPEF /tE could be a useful pulmonary index which shows lower values in severe BPD. The finding of SGA in infants with BPD could be associated with poor pulmonary function related to the tPEF /tE values.

Tidal breathing flow volume profiles during sleep in wheezing infants measured by impedance pneumography

Overnight analysis of tidal breathing flow volume (TBFV) loops, recorded by impedance pneumography (IP), has been successfully applied in the home monitoring of children with wheezing disorders. However, little is known on how sleep physiology modifies the relationship between TBFV profiles and wheeze. We studied such interactions in wheezing infants. Forty-three infants recruited because of recurrent lower airway symptoms were divided into three groups based on their risk of asthma: high (HR), intermediate (IR), or low (LR). Sedated patients underwent infant lung function testing including assessment of airway responsiveness to methacholine at the hospital and a full-night recording of TBFV profiles at home with IP during natural sleep. Overnight TBFV indexes were estimated from periods of higher and lower respiration variability, presumably belonging to active [rapid eye movement (REM)] and quiet [non-REM (NREM)] sleep, respectively. From 35 valid recordings, absolute time indexes showed intrasubject sleep phase differences. Peak flow relative to time and volume was lower in HR compared with LR only during REM, suggesting altered expiratory control. Indexes estimating the concavity/convexity of flow decrease during exhalation suggested limited flow during passive exhale in HR compared with IR and LR, similarly during NREM and REM. Moreover, during REM convexity was negatively correlated with maximal flow at functional residual capacity and methacholine responsiveness. We conclude that TBFV profiles determined from overnight IP recordings vary because of sleep phase and asthma risk. Physiological changes during REM, most likely decrease in respiratory muscle tone, accentuate the changes in TBFV profiles caused by airway obstruction. NEW & NOTEWORTHY Impedance pneumography was used to investigate overnight tidal breathing flow volume (TBFV) indexes and their interactions with sleep phase [rapid eye movement (REM) vs. non-REM] at home in wheezing infants. The study shows that TBFV indexes vary significantly because of sleep phase and asthma risk of the infant and that during REM the changes in TBFV indexes caused by airway obstruction are accentuated and better associated with lung function of the infant.

The effect of inhaled heliox on peak flow rates in normal and brachycephalic dogs.

BackgroundHeliox, a mixture of helium and oxygen, alleviates airway obstruction in people and improves air flow, and its use has been proposed in dogs. Brachycephalic dogs have naturally occurring airway obstruction where heliox might be a useful therapeutic option.ObjectiveThe purposes of this study were to (1) determine the impact of breathing heliox on peak inspiratory and expiratory flows (PIF/PEF) in healthy dogs and (2) determine if brachycephalic dogs and mesocephalic dogs have similar responses to inhaled heliox.AnimalsEleven healthy dogs: 5 mesocephalic and 6 brachycephalic dogs.MethodsA prospective study. Tidal breathing flow‐volume loops were recorded when dogs were breathing room air (nitrogen‐oxygen) and heliox. Peak inspiratory and expiratory flow rates were recorded and the subjective shape of loops assessed. Peak inspiratory and expiratory flows pre‐ and post‐heliox were compared using a Mann‐Whitney Rank sum test with a P‐value of <.05 considered significant.ResultsIn inhaled heliox, PIF and PEF were evaluated by tidal breathing flow‐volume loops. In mesocephalic dogs, PIF increased from a median of 820 mL/s (range, 494‐1010 mL/s) to 1386 mL/s; P = .02; and for PEF from 688 mL/s to 1793 mL/s (P = .04), whereas in brachycephalic dogs, the median PIF increased from 282 mL/s to 694 mL/s; P = .01 and the median PEF increased from 212 mL/s to 517 mL/sec; P = .03. Brachycephalic dogs showed normalization of loop shapes.Conclusions and clinical importanceHeliox improves flow rate and appears to improve flow patterns in brachycephalic dogs.

Dynamic hyperinflation in patients with asthma and exercise-induced bronchoconstriction

BackgroundLittle is known about the behavior of operative lung volumes during exercise in patients with asthma and exercise-induced bronchoconstriction (EIB). ObjectiveTo compare the presence of dynamic hyperinflation (DH) in patients with mild asthma with and without EIB and in healthy individuals and to relate the changes in end-expiratory lung volume (EELV) with postexercise airflow reduction. MethodsA total of 122 consecutive stable patients (>12 years of age) with mild asthma and 38 controls were studied. Baseline lung volumes were measured, and all patients performed an exercise bronchial challenge. At each minute of exercise, EELV and end-inspiratory lung volume (EILV) were estimated from inspiratory capacity measurements to align the tidal breathing flow-volume loops to within the maximal expiratory curve. ResultsDH was more frequent in patients with asthma and EIB (76%) than in patients with asthma but without EIB (11%) or controls (18%). The EELV increased in patients with asthma and EIB and decreased in patients with asthma without EIB and controls during exercise. In the patients with asthma, the decrease in forced expiratory volume in 1 second after the exercise challenge correlated with age (r = −0.179, P = .05), baseline forced vital capacity (r = 0.255, P = .005), EELV increase (r = 0.447, P < .001), and EILV increase (r = 0.246, P = .007). Age, baseline forced vital capacity, and magnitude of DH were retained as independent predictors of EIB intensity. ConclusionIn patients with asthma and EIB, the development of DH is very frequent and related to the intensity of postexercise bronchoconstriction. This finding could implicate DH in the development of EIB.

Accuracy of tidal breathing measurement of floright compared to an ultrasonic flowmeter in infants

Monitoring breathing pattern is especially relevant in infants with lung disease. Recently, a vest-based inductive plethysmograph system (FloRight®) has been developed for tidal breathing measurement in infants. We investigated the accuracy of tidal breathing flow volume loop (TBFVL) measurements in healthy term-born infants and infants with lung disease by the vest-based system in comparison to an ultrasonic flowmeter (USFM) with a face mask. We also investigated whether the system discriminates between healthy infants and those with lung disease. Floright® measures changes in thoracoabdominal volume during tidal breathing through magnetic field changes generated by current-carrying conductor coils in an elastic vest. Simultaneous TBFVL measurements by the vest-based system and the USFM were performed at 44 weeks corrected postmenstrual age during quiet unsedated sleep. TBFVL parameters derived by both techniques and within both groups were compared. We included 19 healthy infants and 18 infants with lung disease. Tidal volume per body weight derived by the vest-based system was significantly lower with a mean difference (95% CI) of -1.33 ml/kg (-1.73; -0.92), P < 0.001. Respiratory rate and ratio of time to peak tidal expiratory flow over total expiratory time (tPTEF/tE) did not differ between the two techniques. Both systems were able to discriminate between healthy infants and those with lung disease using tPTEF/tE. FloRight® accurately measures time indices and may discriminate between healthy infants and those with lung disease, but demonstrates differences in tidal volume measurements. It may be better suited to monitor breathing pattern than for TBFVL measurements.

Assessment of bronchodilator response in preschool children by pulmonary function tests

We performed pulmonary function test to document bronchodilator response by using tidal breathing flow volume loop (TBFVL), rapid thoracic compression (RTC), and raised volume rapid thoracic compression (RVRTC) techniques. Thirty-nine children (mean age 45.2 months) were evaluated. The parameters that showed significant improvement after bronchodilator administration included TEF10/ PTEF ratio in TBFVL, and FEF25-75%, FEV1 and PEF in RVRTC. None of the parameters measured in RTC showed significant improvement. We conclude FEV1, PEF and FEF 25-75% in RVRTC have greater sensitivity for detection of airways changes.

Tidal breathing flow volume loop analysis of 21 healthy, unsedated, young adult maleBeagle dogs

Reference values for dogs regarding tidal breathing flow volume loop (TBFVL) parameters are scarce in the veterinary literature, so each new study requires a healthy reference population to be studied simultaneously with the diseased one. To establish reference values for TBFVL parameters in healthy dogs, to detect any potential variability in loop shape and in various TBFVL parameters and to propose clinically useful parameters for TBFVL analysis. Cross-sectional, prospective study. Twenty-one healthy, unsedated, untrained, young adult, male Beagle dogs, with minimum variability in body weight and somatometry were used. Their good health status was confirmed by physical examination, complete blood count, serum biochemistry, urinalysis, serology and parasitology for Dirofilaria immitis, faecal examination, arterial blood gas analysis, electrocardiography, and radiographic and endoscopic examinations of the respiratory tract. The shape of the TBFVLs was assessed initially. Volume, time and flow parameters, as well as their ratios, were calculated; in total 44 parameters were evaluated. Statistical indices, including Cronbach's α, discrimination index, coefficient of variation (CV) and 95% confidence intervals were estimated for each parameter. One consistently reproducible type of TBFVL shape was identified that had a similar appearance to the letter D. Statistical analysis showed that only two parameters were found to have Cronbach's α lower than 0.80. The CV for the TBFVL parameters ranged from 1.5% to 49%, but the vast majority had values lower than 20%. Eight parameters had very low CV, indicating increased homogeneity. A large number of clinically applicable TBFVL parameters were identified. Parameters related to flow and time were considered to correlate more objectively to the functional capacity of the respiratory system of healthy, unsedated dogs.

The clincal significace of pulmonary function detection in normal toddler

Objective To explore the development of pulmonary function of normal toddlers between 1 and 3 years old.Methods Totally 115 normal toddlers were divided into 2 groups according to their age,i.e,1 ～ 2 years old,2～3 years old.The indicator of small and big airway examine respiratory system static compliance,total airway resistance and functional residual volume were observed.Results No significant difference was found between male and female toddler( P ＞0.05 ).Between the two groups,the difference of respiratory rate was not significant( 27 vs 26,t =1.512,P ＞0.05 ).The values of tidal volumes in the 2 ～ 3 years group was notably higher than in the 1 ～ 2 years group(0.123 vs 0.091,t =8.586,P ＜ 0.01 ),but the values of tidal volumes per kilogram body weight was not significantly different (0.0091 vs 0.0087,t =1.958,P ＞ 0.05 ).The peak tidal expiratory flow in the elder group was similarly distinctly higher than that in the other group.The measured tidal breathing flow volume loops were both displayed uncharacteristic ellipse.The rations of inspiratory time to total respiratory time,the volume to reach peak tidal expira-tory flow to total expiratory volume,tidal expiratory flow at 25％ remaining expiration to peak expiratory flow and mid-tidal expiratory flow to mid-tidal inspiratory flow were not significantly different between two groups (P ＞ 0.05 ).Butthe ratio of peak tidal flow to tidal volume( 1.257 vs 1.095,t =2.099,P ＜ 0.05 ) and the respiratory system resistances( 2.698 vs 2.071,t =3.762,P ＜0.01 )were evidently lower in the elder group than in the younger.The respiratory system compliances(0.353 vs 0.254,t =4.296,P ＜0.01 ) and functional residual capacities(0.272 vs 0.212,t =8.469,P ＜0.01 ) were significantly higher in the elder group than that in the younger,but the values per kilogram body weight was not significantly different( P ＞0.05 ).It was shown that the values of tidal volume,peak tidal expiratory flow,respiratory system static compliance,residual volume were significantly different(0.0198 vs 0.0198,t =0.000,P ＞0.05),between two groups.The values of each parameter mentioned above were increased with age,and were positively correlated with body weight(γ=0.457,0.849,0.572,0.319 all P＜0.01 ).Conclusion Tidal breathing flow volume loop could show functions of small and large airways and partially replace the maximum expiratory flow loop.The parameters were stable in toddlers and could be used as reasonable index to evaluate the pulmonary function changes in pulmonary diseases.The ventilatory function,residual volume,respiratory system static compliance and peak tidal flow were increased with the age,which coincides with the rule of development of toddlers. Key words: Child ; Respiratory function tests

Early Lung Function Testing in Infants with Aortic Arch Anomalies Identifies Patients at Risk for Airway Obstruction

BackgroundAortic arch anomalies (AAA) are rare cardio-vascular anomalies. Right-sided and double-sided aortic arch anomalies (RAAA, DAAA) are distinguished, both may cause airway obstructions. We studied the degree of airway obstruction in infants with AAA by neonatal lung function testing (LFT).Patients and Methods17 patients (10 RAAA and 7 DAAA) with prenatal diagnosis of AAA were investigated. The median (range) post conception age at LFT was 40.3 (36.6–44.1) weeks, median body weight 3400 (2320–4665) g. Measurements included tidal breathing flow-volume loops (TBFVL), airway resistance (Raw) by bodyplethysmography and the maximal expiratory flow at functional residual capacity (V′maxFRC) by rapid thoracic-abdominal compression (RTC) technique. V′maxFRC was also expressed in Z-scores, based on published gender-, age and height-specific reference values.ResultsAbnormal lung function tests were seen in both RAAA and DAAA infants. Compared to RAAA infants, infants with DAAA had significantly more expiratory flow limitations in the TBFVL, (86% vs. 30%, p<0.05) and a significantly increased Raw (p = 0.015). Despite a significant correlation between Raw and the Z-score of V′maxFRC (r = 0.740, p<0.001), there were no statistically significant differences in V′maxFRC and it's Z-scores between RAAA and DAAA infants. 4 (24%) infants (2 RAAA, 2 DAAA) were near or below the 10th percentile of V′maxFRC, indicating a high risk for airway obstruction.ConclusionBoth, infants with RAAA and DAAA, are at risk for airway obstruction and early LFT helps to identify and to monitor these infants. This may support the decision for therapeutic interventions before clinical symptoms arise.

MEASURING THE LUNG FUNCTION CONTINUOUSLY AND UNOBTRUSIVELY

Background and Aims: The conventional pulmonary function tests (PFTs) require respiratory maneuvers like forced maximal expiration, and only give snap shot information of the lung function. Our aim is to devise methodology for continuous unobtrusive assessment of the lung function using a wearable impedance pneumography (IP) system. Methods: IP is based on the knowledge that the electrical impedance of the thorax is proportional to the lung volume. Thus, variation in the lung volume can be assessed by placing two or more measurement electrodes on the surface of the body to measure the impedance variations. Furthermore, the obtained signal can be used to produce diagnostic tidal breathing flowvolume loops. The shape of these loops change in a characteristic way when an airway obstruction occurs or is relieved (Beydon et al. 2011). Results: We have conducted multiple measurements on healthy subjects and patients with obstructive airway diseases, assessing the agreement between the IP and a direct mouth airflow measurement. Thanks to our research on electrode locations and signal processing techniques, we have been able to produce highly accurate pulmonary flow-volume loops regardless of the subject body posture or presence of an obstructive airway disease. We also have produced a wearable cell phone size 24h IP recording device. Conclusions: IP is accurate enough to produce diagnostic pulmonary flow-volume loops. It does not require any direct connection with the airways nor any proactivity from the measurement subject, unlike the conventional PFTs. This potentially enables continuous, long-term estimation of changes in lung function due to external agents and obstructive diseases like asthma. In combination with personal exposure monitors, IP could be used to assess the immediate real-time effects of air pollution on the lung function. This would be especially beneficial for preschool children and infants with whom the conventional PFTs cannot be used at all.

Normative data for lung function and exhaled nitric oxide in unsedated healthy infants

Despite association with lung growth and long-term respiratory morbidity, there is a lack of normative lung function data for unsedated infants conforming to latest European Respiratory Society/American Thoracic Society standards. Lung function was measured using an ultrasonic flow meter in 342 unsedated, healthy, term-born infants at a mean ± sd age of 5.1 ± 0.8 weeks during natural sleep according to the latest standards. Tidal breathing flow-volume loops (TBFVL) and exhaled nitric oxide (eNO) measurements were obtained from 100 regular breaths. We aimed for three acceptable measurements for multiple-breath washout and 5-10 acceptable interruption resistance (R(int)) measurements. Acceptable measurements were obtained in ≤ 285 infants with high variability. Mean values were 7.48 mL·kg⁻¹ (95% limits of agreement 4.95-10.0 mL·kg⁻¹) for tidal volume, 14.3 ppb (2.6-26.1 ppb) for eNO, 23.9 mL·kg⁻¹ (16.0-31.8 mL·kg⁻¹) for functional residual capacity, 6.75 (5.63-7.87) for lung clearance index and 3.78 kPa·s·L⁻¹ (1.14-6.42 kPa·s·L⁻¹) for R(int). In males, TBFVL outcomes were associated with anthropometric parameters and in females, with maternal smoking during pregnancy, maternal asthma and Caesarean section. This large normative data set in unsedated infants offers reference values for future research and particularly for studies where sedation may put infants at risk. Furthermore, it highlights the impact of maternal and environmental risk factors on neonatal lung function.

Analysis of tidal breathing flow volume loop in dogs with tracheal masses

To investigate whether there are any changes in the tidal breathing flow volume loop (TBFVL) in calm, non-dyspnoeic dogs with intratracheal masses. We compared 4 dogs with intratracheal masses (group 1) with 10 healthy dogs (group 2). Routine clinical and laboratory examinations of the dogs were unremarkable, except for episodic upper respiratory obstructive signs in the dogs in group 1. Lateral radiography of the neck and thorax showed that group 1 dogs had masses that appeared to protrude into the tracheal lumen. Tracheoscopy and surgery or necropsy was performed to confirm the presence of the mass. Arterial blood gas and TBFVL analysis was carried out in all dogs to assess respiratory status. The shape of the TBFVL for dogs in group 1 was narrower and ovoid compared with that for the group 2 dogs. Tidal volume and expiratory and inspiratory times were significantly reduced, whereas the respiratory rate was increased for dogs in group 1 compared with dogs in group 2. Arterial blood gas analysis was unremarkable for all dogs. TBFVL is a non-invasive technique that is easy to perform and well tolerated by dogs. In the absence of abnormalities detected by routine diagnostic evaluations and arterial blood gas analysis in dogs with intratracheal masses, the TBFVL contributes to the definition of the physiologic status of the airways at the time of testing, and results suggests that these dogs breathe quite normally when they are calm and non-dyspnoeic.

SCIENTIFIC AND CLINICAL: In this issue – September 2010

Agricultural shows and communicable disease transmission in poultry · Capsule endoscopy in horse small intestine · Acute lameness from a bone metastasis in a horse · Tidal breathing flow volume loop in dogs with tracheal masses · Intracranial meningioma and facial myokymia in a dog · Caudal epidural flank anaesthesia using multiport catheters in cattle · Needle‐free vaccination in sheep · Smoking vets in Australia