Tidal Flow Volume Research Articles

Tidal Flow-Volume Loop Enveloping at Rest in Advanced COPD.

Expiratory flow limitation (EFL) is a key physiological abnormality in COPD. Comparing tidal-to-maximum flow-volume (F-V) loops is a simple and widely available method to assess EFL in patients with COPD. We aimed to investigate whether subjects with COPD showing significant resting tidal F-V enveloping (ie, > 50% tidal volume) would present with higher exertional operating lung volumes, which would lead to greater burden of dyspnea and poorer exercise tolerance compared to their counterparts. 37 subjects with COPD (21 males; 63.1 ± 9.2 years old; FEV1 = 37 ± 12% predicted) and 9 paired controls (3 males; 55.9 ± 11.7 y old) performed an incremental cardiopulmonary exercise testing on a cycle ergometer. Dyspnea perception, inspiratory capacity maneuvers after 3-4 sequential tidal F-V loops, and esophageal and gastric pressures were measured during exercise. Most subjects (31 of 37, 84%) presented with significant tidal F-V enveloping. Critical inspiratory constraints and upward dyspnea inflection points (as a function of both work rate and ventilation) were reached earlier in these subjects, thereby leading to poorer exercise tolerance compared to their counterparts (P = .01). Abdominal muscle recruitment (ie, increase in gastric pressure ≥ 15%) during tidal expiration was significantly higher in the EFL+ group. However, this did not bear an influence on the operating lung volumes, inspiratory constraints, dyspnea, cardiocirculatory responses, or exercise tolerance (P > .05). Tidal F-V loop enveloping at rest should be valued as it is related to relevant clinical outcomes, such as dyspnea burden and exercise tolerance in subjects with COPD.

Ventilatory Limitation of Exercise in Pediatric Subjects Evaluated for Exertional Dyspnea

Purpose: Attribution of ventilatory limitation to exercise when the ratio of ventilation () at peak work to maximum voluntary ventilation (MVV) exceeds 0.80 is problematic in pediatrics. Instead, expiratory flow limitation (EFL) measured by tidal flow-volume loop (FVL) analysis – the method of choice – was compared with directly measured MVV or proxies to determine ventilatory limitation.Methods: Subjects undergoing clinical evaluation for exertional dyspnea performed maximal exercise testing with measurement of tidal FVL. EFL was defined when exercise tidal FVL overlapped at least 5% of the maximal expiratory flow-volume envelope for > 5 breaths in any stage of exercise. We compared this method of ventilatory limitation to traditional methods based on MVV or multiples (30, 35, or 40) of FEV1. Receiver operating characteristic curves were constructed and area under curve (AUC) computed for peak /MVV and peak /x⋅FEV1.Results: Among 148 subjects aged 7–18 years (60% female), EFL was found in 87 (59%). Using EFL shown by FVL analysis as a true positive to determine ventilatory limitation, AUC for peak /30⋅FEV1 was 0.84 (95% CI 0.78–0.90), significantly better than AUC 0.70 (95% CI 0.61–0.79) when 12-s sprint MVV was used for peak /MVV. Sensitivity and specificity were 0.82 and 0.70 respectively when using a cutoff of 0.85 for peak /30⋅FEV1 to predict ventilatory limitation to exercise.Conclusion: Peak /30⋅FEV1 is superior to peak /MVV, as a means to identify potential ventilatory limitation in pediatric subjects when FVL analysis is not available.

Increased prevalence of expiratory flow limitation during exercise in children with bronchopulmonary dysplasia.

Evidence regarding the prevalence of expiratory flow limitation (EFL) during exercise and the ventilatory response to exercise in children born preterm is limited. This study aimed to determine the prevalence of EFL as well as contributing factors to EFL and the ventilatory response to exercise in preterm children with and without bronchopulmonary dysplasia (BPD).Preterm children (≤32 weeks gestational age) aged 9–12 years with (n=64) and without (n=42) BPD and term controls (n=43), performed an incremental treadmill exercise test with exercise tidal flow–volume loops.More preterm children with BPD (53%) had EFL compared with preterm children without BPD (26%) or term controls (28%) (p<0.05). The presence of EFL was independently associated with decreased forced expiratory volume in 1 s/forced vital capacity z-score and lower gestational age (p<0.05). There was no difference in peak oxygen uptake between preterm children with BPD and term controls (48.0 versus 48.4 mL·kg−1·min−1; p=0.063); however, children with BPD had a lower tidal volume at peak exercise (mean difference −27 mL·kg−1, 95% CI −49– −5; p<0.05). Children born preterm without BPD had ventilatory responses to exercise similar to term controls.Expiratory flow limitation is more prevalent in children born preterm with BPD and is associated with airway obstruction and a lower gestational age.

Raised-Volume Forced Expiratory Flow-Volume Curve in Healthy Taiwanese Infants

The raised-volume rapid thoracoabdominal compression (RVRTC) manoeuvre has been applied to obtain full forced expiratory flow-volume curves in infants. No reference data are available for Asian populations. This study was conducted to establish predictive reference equations for Taiwanese infants. Full-term infants without any chronic disease or major anomaly were enrolled from this cohort study. Full forced expiratory flow-volume curves were acquired using RVRTC manoeuvres through Jaeger’s system. Tidal breath analysis, passive respiratory mechanics, and tidal forced expiratory flow-volume curves were performed and collected at the same measurement. Multiple linear analyses were used to model the variables. We performed 117 tests of RVRTC flow-volume curves in 97 infants. The results revealed that all parameters, except for FEV0.5 /FVC, correlated highly and positively with body length. These parameters correlated significantly with other parameters of passive respiratory mechanics and tidal forced expiratory flow-volume curves. This is the first study to establish equipment-specific reference data of full forced expiration using RVRTC manoeuvres in Asian infants. The results revealed that parameters of RVRTC manoeuvres are moderately related to other parameters of infant lung function. These race-specific reference data can be used to more precisely and efficiently diagnose respiratory diseases in infants of Chinese ethnicity.

Expiratory flow limitation and operating lung volumes during exercise in older and younger adults

We determined the effect of aging on expiratory flow limitation (EFL) and operating lung volumes when matched for lung size. We hypothesized that older adults will exhibit greater EFL and increases in EELV during exercise compared to younger controls. Ten older (5M/5W; >60years old) and nineteen height-matched young adults (10M/9W) were recruited. Young adults were matched for%predicted forced vital capacity (FVC) (Y-matched%Pred FVC; n=10) and absolute FVC (Y-matched FVC; n=10). Tidal flow-volume loops were recorded during the incremental exercise test with maximal flow-volume loops measured pre- and post-exercise. Compared to younger controls, older adults exhibited more EFL at ventilations of 26, 35, 51, and 80L/min. The older group had higher end-inspiratory lung volume compared to Y-matched%Pred FVC group during submaximal ventilations. The older group increased EELV during exercise, while EELV stayed below resting in the Y-matched%Pred FVC group. These data suggest older adults exhibit more EFL and increase EELV earlier during exercise compared to younger adults.

Pulmonary arterial hypertension screening and its correlation with pulmonary function in children with asthmatic diseases

Objective To study the pulmonary artery shrink pressure(PASP) and pulmonary function in children with asthmatic diseases, and screen pulmonary arterial hypertension(PAH). To probe the correlation between PASP and pulmonary function. Methods Ninety children with asthmatic diseases from November 2014 to April 2015 at the Department of Respiratory, Women and Children′s Hospital of Qingdao City were chosed as asthmatic group, and 90 healthy children in the same period were selected as healthy control group.PASP and pulmonary function were detected by Doppler ultrasound and tidal flow-volume loop respectively within 24 hours of admission, the respite degrees were assessed by clinical and tidal flow-volume loop.SPSS 13.0 statistical software was used for statistical analysis. Results PASP of the asthmatic group and the healthy control group was (3.24±0.66) kPa and (3.15±0.49) kPa, and the difference was statistically significant (F=7.50, P<0.05). There were 10 cases of PAH in the asthmatic group, which had statistically difference with the healthy control group (χ2=10.59, P<0.05). The tidal volume per kilogram, the ratio of time to peak tidal expiratory flow to total expiratory time, the ratio of volume to peak expiratory flow to total ex-piratory volume of the asthmatic group were (6.62±1.63) mL/kg, (26.76±6.48)% and (26.66±6.54)%, and these three indicators of the healthy control group were(8.38±0.80) mL/kg, (34.35±2.84)% and (34.23±3.02)%, but that of the former group were less than that of the lower respectively(F=86.28, 138.08, 113.27, all P<0.05). PASP had negative correlation with the ratio of time to peak tidal expiratory fow to total expiratory time in the asthmatic group (r=-9.45, P<0.05). PASP was increased with the aggravation of respite, and it had statistical difference between the mild or moderate asthmatic group [(3.43±0.50) kPa, (3.66±0.59) kPa]and the severe group [(4.20±0.75) kPa](χ2=24.81, 12.55, all P<0.05), and the cases of PAH had significant differences among these 3 groups (0, 2, 8 cases in mild, mode rate and severe group, respectively)(χ2=54.92, P<0.05). Conclusions For children with more severe airway obstruction and wheezing, the risk of PASP and PAH will be hig-her.It is helpful to reduce right ventricular function damage for children with asthmatic diseases by measuring PASP and screening PAH in the early stage according to the clinical condition and lung function. Key words: Pulmonary arterial hypertension; Asthmatic diseases; Pulmonary function; Child

Respiratory Function in Healthy Taiwanese Infants: Tidal Breathing Analysis, Passive Mechanics, and Tidal Forced Expiration.

BackgroundAlthough infant lung function (ILF) testing is widely practiced in developed Western countries it is not typically performed in Eastern countries, and lung measurements are scarce for Asian infants. Therefore, this study aimed to establish normal reference values for Taiwanese infants.Materials and MethodsFull-term infants without any chronic diseases and major anomalies were enrolled in the Prediction of Allergies in Taiwanese Children (PATCH) cohort study. Detailed medical data, such as body weight and length, birth history, and histories of previous illness and hospitalization were recorded. Lung function measurements such as analysis of tidal breathing, passive respiratory mechanics, and forced tidal expiratory flow-volume curves were obtained through Jaeger Masterscreen BabyBody Paediatrics System. Multiple linear analyses were performed to determine various parameters of the lung function tests.ResultsILF test parameters were collected from 126 infants, and 189 tests were performed. The results revealed that the ratio of time to peak expiratory flow to total expiratory time, the ratio of volume to peak expiratory flow to total expiratory volume, and the ratio of inspiratory time to total respiratory time remained relatively constant despite differences in age. However, body length is the strongest independent variable influencing tidal volume, respiratory rate, resistance, compliance, and maximal expiratory flow at functional residual capacity.ConclusionAccording to our review of relevant literature, this is the first study to establish a reference data of ILF tests in the Asian population. This study provided reference values and regression equations for several variables of lung function measurements in healthy infants aged less than 2 years. With these race-specific reference data, ILF can more precisely and efficiently diagnose respiratory diseases in infants of Chinese ethnicity.

Operating lung volumes are affected by exercise mode but not trunk and hip angle during maximal exercise.

Despite VO₂peak being, generally, greater while running compared to cycling, ventilation (VE) during maximal exercise is less while running compared to cycling. Differences in operating lung volumes (OLV) between maximal running and cycling could be one explanation for previously observed differences in V E and this could be due to differences in body position e.g., trunk/hip angle during exercise. We asked whether OLV differed between maximal running and cycling and if this difference was due to trunk/hip angle during exercise. Eighteen men performed three graded maximal exercise tests; one while running, one while cycling in the drop position (i.e., extreme hip flexion), and one while cycling upright (i.e., seated with thorax upright). Resting flow-volume characteristics were measured in each body position to be used during exercise. Tidal flow-volume loops were measured throughout the exercise. V E during maximal running (148.8 ± 18.9 L min(-1)) tended to be lower than during cycling in the drop position (158.5 ± 24.7 L min(-1); p = 0.07) and in the upright position (158.5 ± 23.7 L min(-1); p = 0.06). End-inspiratory and end-expiratory lung volumes (EILV, EELV) were significantly larger during drop cycling compared to running (87.1 ± 4.1 and 35.8 ± 6.2 vs. 83.9 ± 6.0 and 33.0 ± 5.7% FVC), but only EILV was larger during upright cycling compared to running (88.2 ± 3.5% FVC). OLV and V E did not differ between cycling positions. Since OLV are altered by exercise mode, but cycling position did not have a significant impact on OLV, we conclude that trunk/hip angle is likely not the primary factor determining OLV during maximal exercise.

Lung function trajectories from birth through puberty reflect asthma phenotypes with allergic comorbidity

Childhood asthma phenotypes reflecting underlying developmental mechanisms are sought, with little information on asthma phenotypes based on allergic comorbidities. We asked whether lung function trajectories from birth to 16 years were associated with asthma phenotypes with comorbid allergic rhinitis and atopic dermatitis. Lung function (given as z scores) was measured at birth in 329 subjects in the "Environment and Childhood Asthma" birth cohort study in Oslo by using tidal flow volume loops, and at 10 and 16 years by using spirometry. Asthma phenotypes were classified on the basis of recurrent bronchial obstruction at 0 to 2 years, and asthma from the 2- to 10-year and 10- to 16-year intervals, and by combining asthma, atopic dermatitis, and/or allergic rhinitis from 10 to 16 years, stratifying for allergic sensitization. The reference group included 231 subjects without recurrent bronchial obstruction or asthma. Lung function trajectories differed significantly for asthma comorbidity phenotypes for FEV1, forced expiratory flow at 25% to 75% of forced vital capacity, and FEV1/forced vital capacity (all P < .0001). Significant lung function impairment was observed from birth through 16 years among subjects with asthma, atopic dermatitis, and allergic rhinitis. Lung function trajectories in subjects with asthma at 10 to 16 years or asthma in remission differed significantly for all 3 spirometric values compared with the trajectories in those who never had asthma (P < .0001), but not between asthma groups. Allergic sensitization was not significantly associated with asthma phenotype lung function trajectories. The trajectory consisting of impaired lung function from birth throughout childhood in children with asthma, atopic dermatitis, and allergic rhinitis appears less likely to be driven by allergic sensitization, and may imply disease onset in utero, with clinical presentation later in childhood.

Dysanapsis ratio as a predictor for expiratory flow limitation

To determine the efficacy of the dysanapsis ratio (DR) in predicting expiratory flow limitation during exercise, 146 subjects (73 men, 73 women) performed standard pulmonary function and maximal incremental exercise tests. Tidal flow-volume loops were recorded at maximal exercise with maximal flow-volume loops measured pre- and post-exercise. Men had larger (p<0.05) lung volumes, flow rates, and V˙O2max compared to women, but DR was similar (0.21±0.05 vs. 0.20±0.06, respectively, p>0.05). V˙O2max was not different (p>0.05) between the EFL subjects compared to the non-EFL subjects for both men and women. Men with EFL compared to non-EFL men had smaller FVC (5.16±0.89L vs. 5.67±0.86L, p<0.05) and DR (0.19±0.05 vs. 0.23±0.04, p<0.05). Similarly, women with EFL compared to non-EFL had significantly smaller DR (0.18±0.05 vs. 0.24±0.05), but similar FVC (3.88±0.52 vs. 4.12±0.64, p>0.05). A DR threshold was not determined; however, a DR continuum exists with increasing DR leading to decreased prevalence of EFL. In conclusion, DR is effective in determining the likelihood of EFL at maximal exercise.

Ventilatory patterns differ between maximal running and cycling

To determine the effect of exercise mode on ventilatory patterns, 22 trained men performed two maximal graded exercise tests; one running on a treadmill and one cycling on an ergometer. Tidal flow-volume (FV) loops were recorded during each minute of exercise with maximal loops measured pre and post exercise. Running resulted in a greater VO2peak than cycling (62.7±7.6 vs. 58.1±7.2mLkg−1min−1). Although maximal ventilation (VE) did not differ between modes, ventilatory equivalents for O2 and CO2 were significantly larger during maximal cycling. Arterial oxygen saturation (estimated via ear oximeter) was also greater during maximal cycling, as were end-expiratory (EELV; 3.40±0.54 vs. 3.21±0.55L) and end-inspiratory lung volumes, (EILV; 6.24±0.88 vs. 5.90±0.74L). Based on these results we conclude that ventilatory patterns differ as a function of exercise mode and these observed differences are likely due to the differences in posture adopted during exercise in these modes.

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

No effect of arm-crank exercise on diaphragmatic fatigue or ventilatory constraint in Paralympic athletes with cervical spinal cord injury

Cervical spinal cord injury (CSCI) results in a decrease in the capacity of the lungs and chest wall for pressure, volume, and airflow generation. We asked whether such impairments might increase the potential for exercise-induced diaphragmatic fatigue and mechanical ventilatory constraint in this population. Seven Paralympic wheelchair rugby players (mean + or - SD peak oxygen uptake = 16.9 + or - 4.9 ml x kg(-1) x min(-1)) with traumatic CSCI (C(5)-C(7)) performed arm-crank exercise to the limit of tolerance at 90% of their predetermined peak work rate. Diaphragm function was assessed before and 15 and 30 min after exercise by measuring the twitch transdiaphragmatic pressure (P(di,tw)) response to bilateral anterolateral magnetic stimulation of the phrenic nerves. Ventilatory constraint was assessed by measuring the tidal flow volume responses to exercise in relation to the maximal flow volume envelope. P(di,tw) was not different from baseline at any time after exercise (unpotentiated P(di,tw) = 19.3 + or - 5.6 cmH(2)O at baseline, 19.8 + or - 5.0 cmH(2)O at 15 min after exercise, and 19.4 + or - 5.7 cmH(2)O at 30 min after exercise; P = 0.16). During exercise, there was a sudden, sustained rise in operating lung volumes and an eightfold increase in the work of breathing. However, only two subjects showed expiratory flow limitation, and there was substantial capacity to increase both flow and volume (<50% of maximal breathing reserve). In conclusion, highly trained athletes with CSCI do not develop exercise-induced diaphragmatic fatigue and rarely reach mechanical ventilatory constraint.

Childhood asthma and early life exposure to indoor allergens, endotoxin and β(1,3)‐glucans

Divergent results have been reported regarding early life exposure to indoor environmental agents and the risk of asthma and allergic sensitization later in life. To assess whether early exposure to indoor allergens, beta(1,3)-glucans and endotoxin modifies the risk of allergic diseases at 10 years of age. The concentrations of mite, cat and dog allergens, endotoxin and beta(1,3)-glucans were determined in dust from the homes of 260 two-year-old children with lung function measured at birth (tidal flow volume loops) in the Environment and Childhood Asthma study in Oslo. At 10 years, the health status was assessed in a follow-up study including a structured interview of the parents and an extended clinical examination. Cat and dog keeping at 2 years of age was reported in 6.5% and 5.5% of the families, respectively. Mite allergens were detected in only 4/260 dust samples. The adjusted odds ratio for asthma at age 10 was 1.20 (95% confidence interval: 1.01-1.43) and 1.22 (1.02-1.46) for bronchial hyperresponsiveness (BHR) per 10 microg/g dust increase in cat allergen exposure at 2 years of age. No association was seen with allergic sensitization. Moreover, endotoxin and beta(1,3)-glucan exposure did not modify the risk of asthma or allergic sensitization. None of the measured environmental factors were associated with lung function at 10 years of age or a relative change in lung function from birth. In a community with a low prevalence of pet keeping and low mite allergen levels, exposure to cat allergens early in life increased the risk of late childhood asthma and BHR, but not the risk of allergic sensitization. No risk modification was seen for dog allergens, endotoxin and beta(1,3)-glucans.

Exertional dyspnoea in patients with pectus excavatum

Most patients with pectus excavatum report better exercise tolerance and less exertional dyspnoea following surgical repair of their chest wall deformity. The reason(s) for this symptomatic improvement remain speculative but include a reversal of deconditioning and improved stroke volume. Improved function or efficiency of the respiratory muscle pump has never been assessed as a potential reason for reduced dyspnoea. An emerging approach to assessing ventilatory constraint during exercise is to plot the tidal flow–volume loops obtained during exercise within the maximal volitional flow–volume envelope obtained at rest. This paper summarises a review of pulmonary function in patients with pectus excavatum before and after surgery, and then illustrates how this newer technique can be applied in order to determine the ventilatory limitation to exercise in this population.

Lung function at 10 yr is not impaired by early childhood lower respiratory tract infections

The causal relationship between lower respiratory tract infections (LRIs) in early life and reduced lung function later in childhood is unsettled. Therefore, we assessed whether LRIs the first 2 yr of life influenced lung function development from birth to school age. In the prospective Oslo birth cohort, 'the Environment and Childhood Asthma (ECA) study' lung function was measured at birth in 802 infants by tidal flow volume loops and in 664 infants by passive respiratory mechanics and half yearly questionnaires, including LRI questions, were completed until 2 yr of age. The present study includes 607 children with information about LRIs the first 2 yr of life and successfully forced expiratory flow (FEF) volume measurements at the 10-yr follow-up assessment. At 10 yr of age, FEF at 50% of forced vital capacity (FEF(50)) (mean 95% confidence interval) was reduced in children with at least one bronchiolitis (85.0, 80.6-89.5, p = 0.020) or bronchitis (86.2, 82.6-89.8, p = 0.030) or > or =3 LRIs (83.4, 78.1-88.8, p = 0.017) when compared with no LRIs (90.6, 88.8-92.5) by 2 yr of life. The effects were significant in girls only when stratifying for gender. Among girls with later bronchiolitis compliance of the respiratory system (3.64, 3.17-4.10 vs. 4.18, 3.98-4.37, p = 0.031) and the ratio of time to peak tidal expiratory flow to total expiratory time (t(PTEF)/t(E)) measured at birth was significantly reduced (0. 26, 0.23-0.29 vs. 0.32, 0.30-0.33, p = 0.005) when compared with children with no LRIs. Change in lung function from birth (by t(PTEF)/t(E)) to 10 yr of age was not significantly associated with LRIs the first 2 yr of life, and LRIs by 2 yr of life were not significantly associated with lung function at 10 yr of age in regression analyses including lung function at birth and other possible predictors of lung function at 10 yr. In our study, LRIs during the first 2 yr of life did not impair lung function development from birth until 10 yr of age.

Differing lung function development in infants with univentricular hearts compared with healthy infants

To compare the difference in lung function development of healthy controls and patients with univentricular hearts from birth prior to surgery and during the first year of life when cardiac shunt procedures and the cavopulmonary connection are required. Tidal flow-volume measurements and single-occlusion tests were performed from birth serially up to 18 months of age on 28 unsedated spontaneously breathing infants with univentricular hearts and 58 healthy control infants. Infants with univentricular heart physiology had low tidal volumes, low compliance of the respiratory system and high respiratory rate at birth, which over time normalized, whereas the peak expiratory flow increased during the study period. The lung function measured at birth was predictive of later lung function measurements. The pattern of lung function development is different in the patients with univentricular hearts compared to healthy controls. Lung function measured at birth is predictive of later lung function.

Inhaled corticosteroids in children: use and effects of early treatment on asthma and lung function. Prevalence of asthma and the impact of severity in early life on later asthma in childhood

The role of inhaled corticosteroids (ICS) on disease progression in asthmatic children is not yet clear. This study was conducted (i) to determine how often ICS were used for treatment of obstructive airways disease (OAD) in early childhood; (ii) to assess if ICS treatment had an effect on lung function in young children with recurrent bronchial obstruction (rBO); (iii) to explore if early ICS treatment in children with OAD during the first 2 years of life can modify occurrence of current asthma in school children; (iv) to define a severity score for severity of OAD during the first 2 years of life and assess if the severity score can be used to predict asthma in school children; and (v) to investigate the prevalence of asthma in children in an urban population. The present study is part of a 10-year follow-up of children in the prospective birth cohort (n = 3754), the Environment and Childhood Asthma study in Oslo. For aim 1, all children from the entire cohort who had completed follow-up questionnaires as well as all children defined with rBO were assessed. For aim 2, 54 children with rBO (with and without ICS treatment) and 15 controls with tidal flow volume measurements upon presentation of the disease and 2 years of age were studied. For aims 3 and 4, 459 subjects (with and without rBO at 2 years of age) from the case control study who attended 10-year follow-up were studied. For aim 5, the 616 of 803 subjects who had lung function measurements performed after birth were reinvestigated at the age of 10 years. A total of 2.1% of all the children in the cohort and 21% of children with rBO had received ICS treatment by 2 years of age. The mean difference of change in baseline tidal breathing (the ratio of time to peak expiratory flow to total expiratory time) was significantly higher in the ICS-treated group only by 2 years of age and correlated significantly with duration of ICS treatment. However, in rBO children, the use of ICS treatment before 2 years of age was not associated with reduced risk of current asthma at 10 years of age. The risk (odds ratio, 95% confidence interval) of current asthma among rBO subjects with a severity score above five was 20.2, 9.9-41.3 compared to controls. In 10-year-old children, the lifetime prevalence of asthma was 20.2%. One-fifth of young children with recurrent bronchial obstruction had received inhaled corticosteroids by age 2 years. Lung function appeared to improve in children using ICS from the start of symptoms of OAD until 2 years of age, mostly in children with the longest duration of treatment. However, use of ICS during the first 2 years of life in children with OAD did not reduce asthma present 8 years later. A scoring system based on severity and frequency of OAD during the first 2 years of life predicted current asthma at 10 years of age. One in five 10-year-old children in the city of Oslo at some time had asthma.

Update in the Understanding of Respiratory Limitations to Exercise Performance in Fit, Active Adults

This review addresses three types of causes of respiratory system limitations to O(2) transport and exercise performance that are experienced by significant numbers of active, highly fit younger and older adults. First, flow limitation in intrathoracic airways may occur during exercise because of narrowed, hyperactive airways or secondary to excessive ventilatory demands superimposed on a normal maximum flow-volume envelope. Narrowing of the extrathoracic, upper airway also occurs in some athletes at very high flow rates during heavy exercise. Examination of the breath-by-breath tidal flow-volume loop during exercise is key to a noninvasive diagnosis of flow limitation and to differentiation between intrathoracic and extrathoracic airway narrowing. Second exercise-induced arterial hypoxemia occurs secondary to an excessively widened alveolar-arterial oxygen pressure difference. This inefficient gas exchange may be attributable in part to small intracardiac or intrapulmonary shunts of deoxygenated mixed venous blood during exercise. The existence of these shunts at rest and during exercise may be determined by using saline solution contrast echocardiography. Finally, fatigue of the respiratory muscles resulting from sustained, high-intensity exercise and the resultant vasoconstrictor effects on limb muscle vasculature will also compromise O(2) transport and performance. Exercise in the hypoxic environments of even moderately high altitudes will greatly exacerbate the negative influences of these respiratory system limitations to exercise performance, especially in highly fit individuals.

Relative impact of respiratory muscle activity on tidal flow and end expiratory volume in healthy neonates

It has been suggested that infants dynamically regulate their tidal flow and end-expiratory volume level. The interaction between muscle activity, flow and lung volume in spontaneously sleeping neonates is poorly studied, since it requires the assessment of transcutaneous electromyography of respiratory muscles (rEMG) in matched comparison to lung function measurements. After determining feasibility and repeatability of rEMG in 20 spontaneously sleeping healthy neonates, we measured the relative impact of intercostal and diaphragmatic EMG activity in direct comparison to the resulting tidal flow and FRC. We found good feasibility, repeatability and correlation of timing indices between rEMG activity and flow. The rEMG amplitude was significantly dependent on the resistive load of the face mask. Diaphragm and intercostal muscle activity commenced prior to the onset of flow and remained active during the expiratory cycle. The relative contribution of intercostal and diaphragmatic activity to flow was variable and changed dynamically. Using matched rEMG, air flow and lung volume measurements, we have found good feasibility and repeatability of intercostal and diaphragm rEMG measurements and provide the first quantitative measures of the temporal relationship between muscle activity and flow in spontaneously sleeping healthy neonates. Lung mechanical function is dynamically regulated and adapts on a breath to breath basis. So, non-invasive rEMG measurements alone or in combination with lung function might provide a more comprehensive picture of pulmonary mechanics in future studies. The data describing the timing of EMG and flow may be important for future studies of EMG triggered mechanical ventilation.