Reach Peak Tidal Expiratory Flow Research Articles

Maternal asthma is associated with reduced lung function in male infants in a combined analysis of the BLT and BILD cohorts

RationaleAsthma in pregnancy is associated with respiratory diseases in the offspring.ObjectiveTo investigate if maternal asthma is associated with lung function in early life.MethodsData on lung function measured at 5–6 weeks...

Fetal Origins of Asthma: A Longitudinal Study from Birth to Age 36 Years.

Rationale: Deficits in infant lung function-including the ratio of the time to reach peak tidal expiratory flow to the total expiratory time (tptef/te) and maximal expiratory flow at FRC (V̇maxFRC)-have been linked to increased risk for childhood asthma.Objectives: To examine the individual and combined effects of tptef/te and V̇maxFRC in infancy on risk for asthma and abnormalities of airway structure into mid-adult life.Methods: One hundred eighty participants in the Tucson Children's Respiratory Study birth cohort had lung function measured by the chest-compression technique in infancy (mean age ± SD: 2.0 ± 1.2 mo). Active asthma was assessed in up to 12 questionnaires between ages 6 and 36 years. Spirometry and chest high-resolution computed tomographic (HRCT) imaging were completed in a subset of participants at age 26. The relations of infant tptef/te and V̇maxFRC to active asthma and airway structural abnormalities into adult life were tested in multivariable mixed models.Measurements and Main Results: After adjustment for covariates, a 1-SD decrease in infant tptef/te and V̇maxFRC was associated with a 70% (P = 0.001) and 55% (P = 0.005) increased risk of active asthma, respectively. These effects were partly independent, and two out of three infants who were in the lowest tertile for both tptef/te and V̇maxFRC developed active asthma by mid-adult life. Infant V̇maxFRC predicted reduced airflow and infant tptef/te reduced HRCT airway caliber at age 26.Conclusions: These findings underscore the long-lasting effects of the fetal origins of asthma, support independent contributions by infant tptef/te and V̇maxFRC to development of asthma, and link deficits at birth in tptef/te with HRCT-assessed structural airway abnormalities in adult life.

The expression and significance of matrix metalloproteinases-9 and tissue inhibitors of matrix metalloproteinase-1 in serum of infant with severe pneumonia

Objective To explore the expression and significance of matrix metalloproteinases-9(MMP-9) and tissue inhibitors of matrix metalloproteinase-1(TIMP-1) in serum at acute phase of severe pneumonia in infants. Methods A total of 45 infants of pneumonia were selected and divided into 20 cases of severe pneumonia group and 25 cases of mild pneumonia group according to the severity of the disease, and all 45 infants were also divided into virus group of 24 cases and non-virus group of 21 cases on the basis of etiology.Additionally, 20 cases of healthy children who accepted the physical examination at the same time were selected as the control group.Serum levels of MMP-9 and TIMP-1 were detected by using ELISA.Tidal breathing lung function was measured in all selected infants. Results Compared with the control group, the serum levels of MMP-9, TIMP-1 and MMP-9/TIMP-1 ratio of the infants with acute pneumonia were significantly higher, the severe pneumonia group were higher than the mild pneumonia group, and the virus group were higher than the non-virus group(P<0.05). The ratio of the time to reach peak tidal expiratory flow to total expiratory time (TPTEF/TE) and the volume to reach peak tidal expiratory flow to total expiratory volume(VPTEF/VE) of pneumonia group in recovery period were significantly lower than those in the control group, severe pneumonia group were lower than those in the mild pneumonia group, and the virus group were lower than those in the non-virus group (all P<0.05). There were no statistically significant about VT/kg among three groups.The serum MMP-9 levels and the MMP-9/TIMP-1 ratio were negatively correlated with TPTEF/TE and VPTEF/VE (r1=-0.459, -0.376; r2=-0.413, -0.327; all P<0.05). Conclusion The serum levels of MMP-9 and the MMP-9/TIMP-1 ratio in the acute phase of infantile pneumonia are correlated with pneumonia severity and pulmonary function injury in recovery period, and the performance is particularly prominent in the viral pneumonia, and can be used as a prognosis monitoring indicator. Key words: Infant; Severe pneumonia; Matrix metalloproteinases-9; Tissue inhibitors of matrix metalloproteinase-1; Lung function,

Tidal breathing patterns derived from structured light plethysmography in COPD patients compared with healthy subjects.

PurposeDifferences in tidal breathing patterns have been reported between patients with chronic obstructive pulmonary disease (COPD) and healthy individuals using traditional measurement techniques. This feasibility study examined whether structured light plethysmography (SLP) – a noncontact, light-based technique – could also detect differences in tidal breathing patterns between patients with COPD and healthy subjects.Patients and methodsA 5 min period of tidal (quiet) breathing was recorded in each patient with COPD (n=31) and each healthy subject (n=31), matched for age, body mass index, and sex. For every participant, the median and interquartile range (IQR; denoting within-subject variability) of 12 tidal breathing parameters were calculated. Individual data were then combined by cohort and summarized by its median and IQR.ResultsAfter correction for multiple comparisons, inspiratory time (median tI) and its variability (IQR of tI) were lower in patients with COPD (p<0.001 and p<0.01, respectively) as were ratios derived from tI (tI/tE and tI/tTot, both p<0.01) and their variability (p<0.01 and p<0.05, respectively). IE50SLP (the ratio of inspiratory to expiratory flow at 50% tidal volume calculated from the SLP signal) was higher (p<0.001) in COPD while SLP-derived time to reach peak tidal expiratory flow over expiratory time (median tPTEFSLP/tE) was shorter (p<0.01) and considerably less variable (p<0.001). Thoraco–abdominal asynchrony was increased (p<0.05) in COPD.ConclusionThese early observations suggest that, like traditional techniques, SLP is able to detect different breathing patterns in COPD patients compared with subjects with no respiratory disease. This provides support for further investigation into the potential uses of SLP in assessing clinical conditions and interventions.

Roles of probiotics in regulating serum ghrelin levels and protecting pulmonary function of children with acute lung injury

Objective To investigate the regulatory effects of probiotics on ghrelin and their protective effects on pulmonary function of children during acute lung injury. Methods Fifty children with acute lung injury were recruited form Henan Provincial People's Hospital during 2010 to 2013 and randomly divided into two groups. In addition to regular therapy, those who received probiotics treatment were set up as the probiotics treatment group and the others were considered as the control group. Levels of ghrelin, surfactant protein A(SP-A), TNF-α and IL-6 in serum samples were measured before and 10 days after the corresponding treatments. Each patient was analyzed by pulmonary function test and echocardiography. The volume to peak expiratory flow (VPEF), ratio of time to reach peak tidal expiratory flow to total expiratory time (TPTEF/TE), mean arterial pressure (MAP) and pulmonary artery pressure (PAP) were recorded for statistical analysis. Results The levels of SP-A, TNF-α and IL-6 in serum samples from the probiotics treatment group were decreased on day 10 as compared with those of the control group [(195.9±54.3) ng/ml vs (245.5±56.4) ng/ml, (382.0±56.4) pg/ml vs (440.7±46.8) pg/ml, (221.5±62.6) pg/ml vs (303.5±83.9) pg/ml; P<0.05]. Children from the probiotics treatment group showed higher values of VPEF and TPTEF/TE on day 10 as compared with those without probiotics treatment [(25.3±4.5) ml vs (23.8±4.6) ml, (29.5±4.3) % vs (26.8±4.7) %; P<0.05]. Treatment of children with probiotics increased MAP and decreased PAP [(74.5±6.7) mmHg vs (71.9±6.9) mmHg, (25.5±6.4) mmHg vs (29.1±6.2) mmHg]. The levels of ghrelin in patients received probiotics treatment were higher than those of children without probiotics treatment [(329.3±49.6) pg/ml vs (296.6±48.5) pg/ml]. The levels of ghrelin showed negative correlations with the levels of SP-A, TNF-α, IL-6 and PAP on day 10, but positive correlations with TPTEF/TE and MAP (P<0.05). Conclusion Use of probiotics to children with acute lung injury could regulate the level of ghrelin, alleviate the inflammation of lungs and improve the recovery of lung function and circulation. Therefore, probiotics treatment had positive effects on the protection of pulmonary function. Key words: Probiotics; Acute lung injury; Ghrelin; Inflammatory factor

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

Time to peak tidal expiratory flow and the neuromuscular control of expiration.

The ratio of the time needed to reach peak tidal expiratory flow (tPTEF) and the duration of expiration (tE) is used to detect airflow obstruction in young children. tPTEF is decreased in patients with asthma, but knowledge about the physiological determinants of this parameter is scarce. This study examined the relationship between tPTEF and postinspiratory activities of inspiratory muscles and evaluated the effects of changing sensory information from the lung. Airflow patterns and electromyographic (EMG) activity of inspiratory muscles were recorded in seven spontaneously breathing, anaesthetized cats. The trachea was cannulated and, as a result, the larynx and upper airways were bypassed. Changes in postinspiratory muscle activity were induced by changing afferent sensory nerve information (by cooling the vagus nerves, by administration of histamine and by additional application of continuous positive airway pressure (CPAP)). Durations of postinspiratory activities of the diaphragm and intercostal muscles (characterized by their time constants tau diaphr and tau interc) correlated strongly with tPTEF (r=0.85 and 0.77, respectively). Tau diaphr, tau interc and tPTEF were significantly increased during cooling of the vagus nerves (4-8 degrees C) compared with values at 22 and 37 degrees C (p<0.05). Conversely, administration of histamine and CPAP caused significant decreases in tau diaphr, tau interc and tPTEF, which were absent during cooling of the vagus nerves. In conclusion, the time needed to reach peak tidal expiratory flow is highly influenced by the activities of inspiratory muscles during the early phase of expiration which, in turn, depend on the activities of vagal receptors in the lung.

Perinatal lung function measurements and prediction of respiratory problems in infancy

The aim of this study was to determine which lung function test employed in the perinatal period gave the results most significantly associated with respiratory problems in infancy. The ratio of the proportion of time to reach peak tidal expiratory flow to total expiratory time , thoracic gas volume (TGV) and airway resistance (from which specific conductance was calculated) measurements were examined from 85 infants born at or near term. The infants were followed until at least one year of age and described as symptomatic if they wheezed for at least 24 hours. Twenty-three infants were symptomatic in the first year. The symptomatic group, compared to the asymptomatic, had a higher median FRC (p < 0.01) and (p < 0.001); their median was lower (p < 0.001). It was possible to obtain results from only 61 infants; the median did not differ significantly between symptomatic and asymptomatic infants. Logistic regression analysis demonstrated a high and FRC, but not a low , independently related to positive symptom status. A high was the most sensitive (83%) predictor of subsequent respiratory problems, but all the tests examined had low positive predictive values. Keywords: lung function tests, tidal breathing parameters

Assessment of prematurely born children at follow-up using a tidal breathing parameter

Prematurely born children frequently have respiratory problems at follow-up. A non-invasive and easily performed lung function test would greatly facilitate their evaluation and appropriate treatment. We have, therefore, assessed whether the shape of the tidal breathing expiratory flow curve would give useful information in such a population. One hundred and twenty traces were randomly selected from plethysmographic measurements of thoracic gas volume and airway resistance made during a follow-up study of a prematurely born population. The children had a median gestational age of 29 (range 23-35, interquartile range 27-31) weeks and postnatal age at the time of measurement of 11 (range 6-24, interquartile range 7-13) months. From the flow and volume signals, the mean time to reach peak tidal expiratory flow as a proportion of the total expiratory time was determined for each child. The median differed significantly between children who, in the neonatal period, had or had not required mechanical ventilation and had or had not had an increased inspired oxygen requirement (p < 0.01), and who were or were not symptomatic at follow-up (p < 0.001). Logistic regression analysis demonstrated that a low ratio was independently associated with symptom status. These results suggest that assessment of a tidal breathing parameter during follow-up of prematurely born children may be useful. As can be measured without sedation, relatively quickly and with simple equipment, potentially large study populations could be investigated, and this technique should now be evaluated in a non-sedated group of young prematurely born children. Keywords: prematurity, lung function measurement, tidal breathing parameters

Tidal breathing parameters in the first week of life and subsequent cough and wheeze.

Assessment of tidal breathing parameters may be a useful method of predicting respiratory problems in early childhood. Low values of TPTEF/TE (the ratio of the proportion of time to reach peak tidal expiratory flow to total expiratory time) outside the neonatal period have been significantly related to respiratory tract illness with wheezing in boys in the first year of life. TPTEF/TE measurements in the perinatal period were evaluated in nonsedated infants and the predictive value of this early measurement for subsequent respiratory morbidity during infancy was assessed. Flow during tidal breathing was measured while the infant slept quietly in a plethysmograph using a Fleisch pneumotachograph inserted into an infant face mask. Recruitment continued until traces from 60 infants with 10 consecutive flow curves without artefacts were obtained. In addition, plethysmographic measurements of airway resistance (Raw) and thoracic gas volume (TGV) were measured and specific conductance (sGaw) calculated. Parents recorded their infant's cough and wheeze during the first 12 months of life. Sixty five measurements were made in 60 infants with a mean age of two days and gestational age of 40 weeks. Two observers separately calculated TPTEF/TE ratios on 25 traces randomly selected from the pool of 60. The mean difference between the two observers was -0.004 (limits of agreement 0.048 to -0.056). Thirteen infants became symptomatic (wheeze, with or without cough); their median TPTEF/TE ratio (0.349) was significantly lower than the rest of the cohort (median 0.412) and they also had significantly higher Raw and lower sGaw. The positive predictive value of a low TPTEF/TE ratio, however, was only 41%. These results suggest that the use of this test in the prediction of future respiratory disease in an individual is limited.

Changes in respiratory rate affect tidal expiratory flow indices in infants with airway obstruction.

Among the tidal expiratory flow measurements that have been suggested as surrogate tests for airway obstruction, a short time to reach peak tidal expiratory flow (t(pef)) is the most widely used. Time to peak expiratory flow is most often expressed as the ratio between t(pef) and total expiratory time (t(e)). As te strictly depends inversely on respiratory rate (RR), we studied the hypothesis that an increase in RR (and a fall in t(e)) with the development of airway obstruction during methacholine or histamine challenge in infants could mask a decrease of t(pef) when expressed as t(pef)/t(e). Thirty-three infants (ages 6.5-23 months) with recurrent wheeze were studied during sedated sleep. Runs of tidal breathing and maximal expiratory flow at FRC (V(maxFRC)) measured by the squeeze technique were obtained before and after the challenge. All infants responded to the challenge: the median fall in P(tCO2) was 25%, and it was 43% in V(maxFRC). RR increased from a median value of 31.1 to a median of 35.1 breaths/min. Both t(pef) and t(e) were significantly shorter after the challenge (P < 0.001 and 0.004, respectively); however, the decrease in t(pef)/t(e) was not significant (P=0.081). The change in t(pef)/t(e) was positively correlated with the change in RR (r = 0.51, P = 0.003). To analyze better the effect of changes in RR on various indices, we divided the patients into two groups: in 17 subjects with a small increase in RR (< 10%), t(e) did not change significantly, while t(pef) and t(pef)/t(e) did; in 16 subjects with a more marked increase in RR (> or = 10%), the shortening of te masked the simultaneous shortening of t(pef), so that t(pef)/t(e) did not change. These data demonstrate that t(pef)/t(e) cannot be reliably used to evaluate changes in airway obstruction when concomitant changes in RR occur.

Changes in respiratory rate affect tidal expiratory flow indices in infants with airway obstruction

Among the tidal expiratory flow measurements that have been suggested as surrogate tests for airway obstruction, a short time to reach peak tidal expiratory flow (tpef) is the most widely used. Time to peak expiratory flow is most often expressed as the ratio between tpef and total expiratory time (te). As te strictly depends inversely on respiratory rate (RR), we studied the hypothesis that an increase in RR (and a fall in te) with the development of airway obstruction during methacholine or histamine challenge in infants could mask a decrease of tpef when expressed as tpef/te. Thirty-three infants (ages 6.5–23 months) with recurrent wheeze were studied during sedated sleep. Runs of tidal breathing and maximal expiratory flow at FRC (˙VmaxFRC) measured by the squeeze technique were obtained before and after the challenge. All infants responded to the challenge: the median fall in PcO2 was 25%, and it was 43% in ˙VmaxFRC. RR increased from a median value of 31.1 to a median of 35.1 breaths/min. Both tpef and te were significantly shorter after the challenge (P < 0.001 and 0.004, respectively); however, the decrease in tpef/te was not significant (P = 0.081). The change in tpef/te was positively correlated with the change in RR (r = 0.51, P = 0.003). To analyze better the effect of changes in RR on various indices, we divided the patients into two groups: in 17 subjects with a small increase in RR (<10%), te did not change significantly, while tpef and tpef/te did; in 16 subjects with a more marked increase in RR (≥10%), the shortening of te masked the simultaneous shortening of tpef so that tpef/te did not change. These data demonstrate that tpef/te cannot be reliably used to evaluate changes in airway obstruction when concomitant changes in RR occur. Pediatr Pulmonol. 1996; 21:236–240. © 1996 Wiley-Liss, Inc.

A critical assessment of uncalibrated respiratory inductance plethysmography (Respitrace®) for the measurement of tidal breathing parameters in newborns and infants

We have compared results obtained with an uncalibrated respiratory inductance plethysmograph (RIP) with those of a face mask and pneumotachograph (PNT) for the computerized measurement of the time to reach peak tidal expiratory flow as a ratio of total expiratory time (tPTEF:tE). Simultaneous measurements were made in 32 healthy neonates aged 0-3 weeks, 35 healthy infants aged 5-82 weeks, and 28 infants aged 15-94 weeks with physician diagnosed recurrent wheeze. The group mean (+/- SD) values of tPTEF:TE determined using a PNT were 0.455 (+/- 0.129), 0.263 (+/- 0.077), and 0.232 (+/- 0.089) for the neonates, healthy infants and infants with recurrent wheeze respectively. RIP gave mean (+/- SD) values that were 0.055 (+/- 0.044) and 0.025 (+/- 0.104) lower than the PNT in healthy neonates and infants with recurrent wheeze respectively; RIP values were 0.002 (+/- 0.073) higher in the healthy infants over 4 weeks of age than measurements by PNT. Although the difference between the two measurements was not related to the thoracoabdominal phase angle, as measured from Lissajous figures, examination of the RIP ribcage and abdominal signals revealed that many healthy subjects, while appearing clinically in phase, had ribcage and abdominal signals that differed markedly from each other in terms of convexity/concavity during early expiration. This may explain the lack of agreement between the two methods. We conclude that uncalibrated RIP should be used with caution for the determination of tPTEF:tE, even in subjects whose ribcage and abdomen appear to move synchronously. The measurement of tPTEF:tE did not differentiate between the healthy infants and infants with recurrent wheezing.

Assessment of Tidal Breathing Patterns for Monitoring of Bronchial Obstruction in Infants

Two parameters of tidal breathing, the ratio of time to reach peak tidal expiratory flow to the total expiratory time (Tme/TE) and the ratio of volume exhaled at peak tidal expiratory flow to the total exhaled volume (dV/VT) were used to assess lung function in 21 sedated infants (aged 6-14 mo) with different degrees of airway obstruction. These parameters were compared with airway resistance as percentage predicted (Raw%) and maximum expiratory flow at functional residual capacity corrected for lung volume (VmaxFRC/TGV). VmaxFRC/TGV values correlated significantly with Tme/TE (r = 0.630, p = 0.002) as well as with dV/VT (r = 0.728, p = 0.001). Raw% values showed only a weak correlation with dV/VT (r = -0.435, p = 0.048). We conclude that Tme/Te and dV/VT are both able to detect airway obstruction in infants and that these parameters correlate much better with the forced expiratory flow values obtained by the rapid thoracic compression method than with airway resistance, determined by body plethysmography.

Ability of new lung function tests to assess methacholine-induced airway obstruction in infants

We assessed the ability of innovative lung function tests to detect bronchial obstruction induced by methacholine bronchial challenge. Fifty-five recurrently wheezy infants (mean age 16 ± 5.2 months) free of respiratory symptoms underwent baseline lung function tests. Forty-two completed the methacholine challenge. Maximal flow at functional residual capacity (V̇maxFRC) was obtained using the squeeze technique; compliance and resistance of the respiratory system (Crs, Rrs) was measured with the passive expiratory flow volume technique; tidal volume breathing patterns were analyzed from recordings of respiratory rate (RR), tidal volume (VT), and inspiratory time divided by total cycle of duration (Ti/Ttot). Expiratory tidal flow volume (V̇/VT) curves were described with multiple indices such as the ratio of expiratory time necessary to reach peak tidal expiratory flow (Fpet) to expiratory time (Tme/Te). Transcutaneous oxygen tension (PcO2) was measured as an indicator of response to methacholine challenge. Of 42 infants 41 responded to methacholine by a change ≥ 2 standard deviations from baseline values. The mean SD unit changes were 9.8 in PcO2, 3.7 for V̇maxFRC, 2.8 for Crs, 2.09 for Rrs, 3.1 for RR, 1.6 for Ti/Ttot, 2.2 for Tme/Te 3.9 for PFvt. We conclude that these noninvasive lung function tests, especially V̇maxFRC and Fpet, can be used to detect minor or moderate airway obstruction. Further studies are needed to determine the value of the tests in assessing bronchial disease and effects of its treatment.

Pressure sensor plethysmography: a method for assessment of respiratory motion in children

Noncalibrated respiratory inductance plethysmography has been used to measure respiratory function by calculation of the phase angle and, more recently, by determination of the ratio of each time to reach peak tidal expiratory flow to total expiratory time (TPEF/TE). Since TPEF/TE is known to be decreased in airway obstruction when derived from flow signals obtained by a pneumotachograph, we wanted to develop an alternative method to measure rib cage and abdominal respiratory movements. For this purpose, we used two pressure sensors attached to the skin above the umbilicus and in the right medioclavicular line at the fourth intercostal space: "pressure sensor plethysmography". We tested the ability of this method to assess thoracoabdominal asynchrony and TPEF/TE by comparison with respiratory inductance plethysmographic and pneumotachographic measurements in 30 children, aged 1-12 yrs, with airway obstruction. The mean difference (95% confidence interval (95% CI)) between phase angles obtained by respiratory inductance plethysmography and pressure sensor plethysmography was only -5.8 degrees (range -18.0 to +6.4 degrees). Similarly, all methods used to measure TPEF/TE agreed well: mean differences (95% CI) between pneumotachographic and respiratory inductance plethysmographic, pneumotachographic and pressure sensor plethysmographic, and respiratory inductance plethysmographic and pressure sensor plethysmographic measurements of TPEF/TE were +0.01 (range -0.05 to +0.06), -0.03 (-0.09 to +0.03) and -0.03 (-0.10 to +0.04), respectively. We conclude that pressure sensor plethysmography is a simple and noninvasive method, and suitable to measure thoracoabdominal asynchrony and TPEF/TE ratios as well as respiratory inductance plethysmography and pneumotachography.

Ability of new lung function tests to assess methacholine‐induced airway obstruction in infants

We assessed the ability of innovative lung function tests to detect bronchial obstruction induced by methacholine bronchial challenge. Fifty-five recurrently wheezy infants (mean age 16 +/- 5.2 months) free of respiratory symptoms underwent baseline lung function tests. Forty-two completed the methacholine challenge. Maximal flow at functional residual capacity (VmaxFRC) was obtained using the squeeze technique; compliance and resistance of the respiratory system (Crs, Rrs) was measured with the passive expiatory flow volume technique; tidal volume breathing patterns were analyzed from recordings of respiratory rate (RR), tidal volume (VT), and inspiratory time divided by total cycle of duration (Ti/Ttot). Expiratory tidal flow volume (V/VT) curves were described with multiple indices such as the ratio of expiratory time necessary to reach peak tidal expiratory flow (Fpet) to expiratory time (Tme/Te). Transcutaneous oxygen tension (PtCO2) was measured as an indicator of response to methacholine challenge. Of 42 infants 41 responded to methacholine by a change > or = 2 standard deviations from baseline values. The mean SD unit changes were 9.8 in PtCO2, 3.7 for VmaxFRC, 2.8 for Crs, 2.09 for Rrs, 3.1 for RR, 1.6 for Ti/Ttot, 2.2 for Tme/Te 3.9 for PFVt. We conclude that these noninvasive lung function tests, especially VmaxFRC and Fpet, can be used to detect minor or moderate airway obstruction. Further studies are needed to determine the value of the tests in assessing bronchial disease and effects of its treatment.

Analysis of tidal breathing parameters in infancy: how variable is TPTEF:TE?

During recent years there has been increasing interest in the measurement of tidal breathing parameters, such as the time to reach peak tidal expiratory flow as a proportion of total expiratory time (TPTEF:TE), and their application to population-based studies of the determinants of early respiratory morbidity. However, little is known about factors influencing the within and between-subject variability of these parameters. This study examines the influence of sedation on TPTEF:TE, estimates the optimal number of breaths and breath epochs required to measure TPTEF:TE, and assesses short-term repeatability of this parameter during the first year of life, taking account of age-related differences. Measurements were made in 266 healthy infants and young children (1 d to 19 mo old). Mean (SD) TPTEF:TE fell from 0.49 (0.11) in the first 2 wk of life to 0.34 (0.09) by 5 to 8 wk, remaining similar thereafter. Sedation with triclofos sodium (75 mg/kg) had no significant effect on TPTEF:TE, which was 0.33 (0.10) in 23 unsedated 6-wk-old infants and 0.32 (0.08) in 49 sedated infants of similar age and weight (95% CI for the difference: -0.05, 0.04). At least 10 breaths in each of two separate epochs from each infant were required to provide a representative estimate of TPTEF:TE. The mean (SD) difference between repeat measurements made 5 to 108 min apart was 0.02 (0.08) in 34 infants younger than 6 wk of age (95% limits of agreement: -0.15, 0.18) and -0.01 (0.04) (95% limits of agreement -0.09, 0.08) in 30 infants 6 wk and older.(ABSTRACT TRUNCATED AT 250 WORDS)

Persistent wheezing and gastroesophageal reflux in infants

We have evaluated the presence of gastroesophageal reflux (GER) and the effect of its treatment in 12 infants (mean age, 7 months; range, 4-11 months) with persistent wheezing not responding to bronchodilators and anti-inflammatory asthma medications. All patients had GER on cineradiography and significant acid reflux on 24 hour pH monitoring (percentage of time pH < 4 ranged from 6.1 to 47%). All infants were initially treated with prokinetic agents and with receptor histamine antagonists in addition to aggressive pulmonary therapy. Six patients treated medically had substantially decreased use of asthma medications, completely discontinuing them within 2-4 months. Two patients, though significantly improved, require intermittent asthma therapy. Four patients responding poorly to GER and asthma treatment for 2 months to 2 years had fundoplications. These had an excellent outcome over 1-4.5 years follow-up; only one patient required further asthma medications. Pulmonary function testing was done in six patients before and after 6-8 weeks of therapy indicating significant improvement in peripheral airflow: terminal flow/peak tidal expiratory flow (TEF25/PTEF), and percentage of total expiratory time to reach peak tidal expiratory flow (Tp/Te or Tme/Te). Our experience suggests that evaluation for GER should be considered in infants with persistent wheezing. Aggressive medical and possibly surgical therapy for GER may resolve persistent wheezing.

Evaluation of a tidal expiratory flow index in healthy and diseased infants.

Patterns of tidal respiratory flow have been shown to relate well to airway function in adults, and one epidemiological study in infants has demonstrated the value of the ratio of time to reach peak tidal expiratory flow to the total expiratory time (tpef/te) in predicting subsequent wheezing. The aim of this study was to evaluate tpef/te as a measure of lung function, by sequential observations over the first year, on a group of 22 healthy infants and on 32 infants with a history of mild recurrent lower respiratory illness (LRI), and by single observations on 20 infants with asthma and 20 with severe chronic lung disease of prematurity. We compared tpef/te measured in quiet, supine sleep (under sedation) through a face mask and pneumotachograph, with a measure of airway function, maximal flow at functional residual capacity (VmaxFRC), obtained from partial forced expiratory flow volume loops using the "squeeze" technique. In healty infants tpet/te was significantly longer at 1 month than at 6 months (median values, 0.38 (95% CI, 0.36-0.43) and 0.28 (95% CI, 0.26-0.33), respectively). Between 6 and 12 months tpef/te did not alter significantly and it was independent of VmaxFRC. Both tpef and te as well as their ratio varied with frequency of breathing over the first year of life, but not within each individual age band, due to the narrow spread of frequencies at each age. In assessing airway obstruction, tpef/te was less sensitive than VmaxFRC. There was no difference between healthy infants, those with LRI, and infants with asthma.(ABSTRACT TRUNCATED AT 250 WORDS)