Tidal Breathing Flow-volume Loops Research Articles

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

Analysis of Tidal Breathing Flow Volume Loops for Automated Lung-Function Diagnosis in Infants

Lung-function analysis in the age group below 5 years has not yet found its way into clinical routine. One possible candidate for routine lung testing in this age group is the analysis of tidal breathing flow-volume (TBFV) loops, a technique that has not yet proven to be capable of detecting obstructive and other lung disorders at an early stage. We present a new set of mathematical features useful to analyze TBFV loops. These new features attempt to describe more complex properties of the loops, thus imitating medical judgment of the curves (e.g., "round," "triangular," etc.) in a "linguistic" manner. Furthermore, we introduce support vector machines (SVMs) as a method for automated classification of diseases. In a retrospective clinical trial on 195 spontaneously breathing infants aged 3 to 24 months, the discriminant power of individual features and the overall diagnostic performance of SVMs is investigated and compared with the results obtained with traditional Bayes' classifiers. We demonstrate that the proposed new features perform better in all examined disease groups and that depending on the disease, the classification error can be reduced by up to 50%. We conclude that TBFV loops may have a much stronger discriminant power than previously thought.

Tidal Breathing Flow-Volume Loop Analysis for the Diagnosis and Staging of Tracheal Collapse in Dogs

Tracheoscopy is generally used for the diagnosis of tracheal collapse (TC) in dogs; yet, it is costly, requires anesthesia, and can irritate the airway. The tidal breathing flow-volume loop (TBFVL) is a safe, quick, and noninvasive pulmonary function test currently used in humans. TBFVL will differentiate dogs with TC from healthy controls and contribute to disease grading. Twenty-eight dogs with naturally occurring TC and 10 healthy controls. Cross-sectional, prospective clinical study: The 38 dogs were assigned to one of 4 groups based on tracheoscopy results: group A (n=10, healthy controls), group B (n=10, grade I TC), group C (n=10, grade II TC), and group D (n=8, grade III TC). The TBFVL measurement was performed on all dogs and loops were assessed for their shape. Forty-four TBFVL parameters were calculated. Two types of TBFVL shapes were identified: Type I, representative of the 10 healthy controls, and Type II, representative of the 28 dogs with TC. Statistical analysis showed the dogs could be differentiated into healthy or affected by TC by 3 indices, TE/TI (expiratory time divided by inspiratory time), TI/TTOT (inspiratory time divided by total respiratory time), and EF75/IF75 (expiratory flow at end tidal volume plus 75% end tidal volume divided by inspiratory flow at end tidal volume plus 75% end tidal volume). The TC could also be graded as mild-moderate (grades I and II) or severe (grade III), showing a diagnostic value of 97.4%. TBFVL is accurate, quick, noninvasive, and safe and can contribute to the diagnosis of TC in dogs.

Measurement of pulmonary function with body plethysmograph in infants

To observe the alterations of pulmonary function in infants with respiratory diseases. A total of 900 infants with respiratory diseases were recruited and pulmonary function measured in 30 healthy infants. The tests were performed in the sleeping infants with sedation. Tidal breathing flow-volume (TBFV) loops were recorded when infants were breathing quietly. Passive flow-volume technique was used to obtain static respiratory system compliance and resistance. Functional residual capacity was measured by body plethysmograph. The TBFV loop showed proximate round or oval curve in healthy infants. The shape and parameters of TBFV loop had significant differences in infants with respiratory diseases as compared with healthy controls. The TBFV loop displayed a concave expiratory curve and ratio of time to reach tidal peak flow to total expiratory time, the expiratory volume till peak flow divided by the total expiratory volume significantly decreased in infants with small airway obstruction. The expiratory or inspiratory curve showed a plateau and the ratio of mid-expiratory to mid-inspiratory flow was less than 60% or over 150% in infants with upper airway obstruction. The TBFV loop turned narrow and lung volume decreased in infants with restrictive diseases. The TBFV loop show proximate round or oval curve in healthy infants. Pulmonary function has significant differences between healthy controls and infants with respiratory diseases. Pulmonary function test is useful in the assessment of respiratory diseases.

Reduced Lung Function at Birth and the Risk of Asthma at 10 Years of Age

Håland G, Carlsen KC, Sandvik L, et al. N Engl J Med. 2006;355:1682–1689 PURPOSE OF THE STUDY. To evaluate whether reduced lung function at birth predicts the development of asthma and markers of obstructive airway diseases by 10 years of age. STUDY POPULATION. A prospective cohort of 616 10-year-old Norwegian children from the Environmental and Childhood Asthma (ECA) study who were initially enrolled as healthy term infants and had undergone lung-function testing and passive respiratory mechanics evaluation shortly after birth. METHODS. Lung function at birth was measured by calculating the fraction of time to peak expiratory flow to total expiratory time (tPTEF/tE) on the basis of tidal breathing flow-volume loops. Respiratory mechanics at birth were assessed by calculating respiratory system compliance and resistance during passive maneuvers. Data at the 10-year follow-up were collected during 2 clinical visits including forced expiratory flow-volume loops, methacholine-challenge tests, a treadmill exercise test, and skin-prick testing for common inhalant and food allergens. Parents also completed a validated International Study of Asthma and Allergies in Childhood questionnaire on airway symptoms, asthma-medication use, and previous physician-diagnosed asthma. The follow-up assessments and interviews were blinded with regard to the lung-function measurements at birth. RESULTS. In this cohort, the prevalence of a history of asthma was 20.2%, and prevalence of current asthma was 11.1%. Children with a tPTEF/tE at or below the median at birth were more likely at 10 years of age to have a history of asthma (24.3% vs 16.2%; P = .01), current asthma (14.6% vs 7.5%; P = .005), severe bronchial hyperresponsiveness (9.1% vs 4.9%; P = .05), and inhaled corticosteroid use (5.9% vs 2.4%; P = .02). Children with respiratory system compliance at or below the median were more likely to have a history of asthma (27.4% vs 14.8%; P = .001) and current asthma (15.0% vs 7.7%; P = .009). Decreased lung-function measurements did not consistently correlate with percent predicted forced flow-volume loops and exercise testing. CONCLUSIONS. Reduced lung function at birth may be a risk factor for the development of asthma by 10 years of age. REVIEWER COMMENTS. Other studies to date have shown that infants with reduced lung function have an increased risk for wheezing and asthma in the first few years of life. This study suggests that measuring lung function at birth may be useful in predicting which infants will develop asthma by late childhood. Knowing these risks may allow for directed therapy and prevention.

Reduced Lung Function at Birth and the Risk of Asthma at 10 Years of Age

Reduced lung function in early infancy has been associated with later obstructive airway diseases. We assessed whether reduced lung function shortly after birth predicts asthma 10 years later. We conducted a prospective birth cohort study of healthy infants in which we measured lung function shortly after birth with the use of tidal breathing flow-volume loops (the fraction of expiratory time to peak tidal expiratory flow to total expiratory time [t(PTEF)/t(E)]) in 802 infants and passive respiratory mechanics, including respiratory-system compliance, in 664 infants. At 10 years of age, 616 children (77%) were reassessed by measuring lung function, exercise-induced bronchoconstriction, and bronchial hyperresponsiveness (by means of a methacholine challenge) and by conducting a structured interview to determine whether there was a history of asthma or current asthma. As compared with children whose t(PTEF)/t(E) shortly after birth was above the median, children whose t(PTEF)/t(E) was at or below the median were more likely at 10 years of age to have a history of asthma (24.3% vs. 16.2%, P=0.01), to have current asthma (14.6% vs. 7.5%, P=0.005), and to have severe bronchial hyperresponsiveness, defined as a methacholine dose of less than 1.0 micromol causing a 20% fall in the forced expiratory volume in 1 second (FEV1) (9.1% vs. 4.9%, P=0.05). As compared with children whose respiratory-system compliance was above the median, children with respiratory compliance at or below the median more often had a history of asthma (27.4% vs. 14.8%; P=0.001) and current asthma (15.0% vs. 7.7%, P=0.009), although this measure was not associated with later measurements of lung function. At 10 years of age, t(PTEF)/t(E) at birth correlated weakly with the maximal midexpiratory flow rate (r=0.10, P=0.01) but not with FEV1 or forced vital capacity. Reduced lung function at birth is associated with an increased risk of asthma by 10 years of age.

Differences in tidal breathing between infants with chronic lung diseases and healthy controls

BackgroundThe diagnostic value of tidal breathing (TB) measurements in infants is controversially discussed. The aim of this study was to investigate to what extent the breathing pattern of sleeping infants with chronic lung diseases (CLD) differ from healthy controls with the same postconceptional age and to assess the predictive value of TB parameters.MethodsIn the age of 36–42 postconceptional weeks TB measurements were performed in 48 healthy newborns (median age and weight 7d, 3100 g) and 48 infants with CLD (80d, 2465 g)) using the deadspace-free flow-through technique. Once the infants had adapted to the mask and were sleeping quietly and breathing regularly, 20–60 breathing cycles were evaluated. Beside the shape of the tidal breathing flow-volume loop (TBFVL) 18 TB parameters were analyzed using ANOVA with Bonferroni correction. Receiver-operator characteristic (ROC) curves were calculated to investigate the discriminative ability of TB parameters.ResultsThe incidence of concave expiratory limbs in CLD infants was 31% and significantly higher compared to controls (2%) (p < 0.001). Significant differences between CLD infants and controls were found in 11/18 TB parameters. The largest differences were seen in the mean (SD) inspiratory time 0.45(0.11)s vs. 0.65(0.14)s (p < 0.0001) and respiratory rate (RR) 55.4(14.2)/min vs. 39.2(8.6)/min (p < 0.0001) without statistically significant difference in the discriminative power between both time parameters. Most flow parameters were strongly correlated with RR so that there is no additional diagnostic value. No significant differences were found in the tidal volume and commonly used TB parameters describing the expiratory flow profile.ConclusionThe breathing pattern of CLD infants differs significantly from that of healthy controls. Concave TBFVL and an increased RR measured during quiet sleep and under standardized conditions may indicate diminished respiratory functions in CLD infants whereas most of the commonly used TB parameters are poorly predictive.

Correlation between tidal breathing flow volumeloops and obstructive sleep apnea in youngchildren with adenotonsillar hypertrophy

Correlation between tidal breathing flow volumeloops and obstructive sleep apnea in youngchildren with adenotonsillar hypertrophy

Measurement of tidal breathing flow-volume loop indices in horses used for different sporting purposes with and without recurrent airway obstruction

Tidal breathing flow-volume loop (TBFVL) indices in healthy horses and in horses suffering from mild and moderate to severe recurrent airway obstruction (RAO) were measured. In addition, the ability of...

Pulmonary function testing in small animals

Pulmonary function testing (PFT) may be used to help provide objective information concerning the respiratory system in dogs and cats. Available techniques for PFT include spirometry, tidal breathing flow-volume loop analysis, barometric whole-body plethysmography, dynamic and static compliance, and lung and upper airway resistance. The information gained from PFT may help both in patient management and also in gaining understanding of the pathophysiology of the pulmonary system.

A decision support system for lung function diagnosis in infants

This paper describes an automatic medical decision support system for lung function diagnosis in infants. The method is based on tidal breathing flow volume loops and air flow resistance measurements, obtained noninvasively from sedated infants. In order to obtain a diagnosis from these signals, a neural network classification algorithm has been implemented for pattern recognition purposes. At the moment, the system allows the classification of about 70% of the breaths, with a failure rate of 15% and 15% rejections.

Effects of technique and analytic conditions on tidal breathing flow volume loops in term neonates.

The tidal breathing flow volume loop (TBFVL) may provide objective assessments of infant airway function. We examined whether infant biologic variability and technical limitations of commercial equipment might affect tidal breathing indices. TBFVLs were obtained in 79 sleeping, healthy, 1-5-day-old infants, divided into two groups: 1) TBFVLs were obtained immediately after face mask placement, i.e., within 5-20 sec (Group A), or 2) after a delay of 2-3 min following face mask placement (Group B). Both tidal volume (VT) and respiratory rates (RR) were significantly lower (25% and 20%, respectively) in Group A than in Group B. VT mean (SD) was 4.45 (0.93) ml/kg for Group A and 6.09 (1.11) ml/kg for Group B (P < 0.0001); RR was 48.4 (12.2) min-1 and 60.0 (15.60) min-1 for Groups A and B, respectively (P < 0.0003). The time to peak expiratory flow as a ratio of total expiratory time (tPTEF:tE), purported to be a useful index of airway obstruction, was also significantly (P < 0.0001) attenuated in TBFVLs obtained immediately after face mask placement; tPTEF:tE was 0.26 (0.09) and 0.37 (0.05) in Groups A and B, respectively. Reproducibility of tPTEF:tE was affected by the timing of recordings. Intraindividual coefficients of variation were greater in Group A (36.53%) than Group B (18.82%). Similarly, significant differences were observed in mean value and variability of other indices of airway function between Groups A and B. Although they are easy to perform, we conclude that tidal breathing analyses may be significantly complicated by simple differences in measurement conditions.

Effects of technique and analytic conditions on tidal breathing flow volume loops in term neonates

Effects of technique and analytic conditions on tidal breathing flow volume loops in term neonates

A Neural Network Approach to Automated Lung Function Diagnosis in Infants

A method for computerized automatic diagnosis of the infant pulmonary system is presented. Based on tidal breathing flow volume loops, the concept offers diagnostic decision support based on statistical analysis of over 600 breath strokes and an automatic pattern recognition system featuring a neural network classification algorithm. At the moment, the system allows to classifiy about 70 % of the breath strokes right and 15 % wrong with another 15 % being rejected.

The effects of three models of airway disease on tidal breathing flow-volume loops of thoroughbred horses.

The effects of histamine and methacholine aerosols and of a fixed inspiratory resistance on tidal breathing flow-volume loops (TBFVL) were investigated using 18 unsedated, standing, healthy thoroughbred horses. The data were first analysed using traditional flow-volume loop indices and then reduced using standardized factor scoring coefficients obtained in a previous study in this laboratory using similar experimental techniques. On the basis of resting TBFVL analysis, the degree of pulmonary dysfunction caused by inhalation of histamine and methacholine aerosols with concentrations of 10 and 2 mg/ml, respectively, was similar. The fixed resistance also caused significant changes in the resting spirogram and TBFVL indices, suggesting that this model may prove valuable for further studies involving upper respiratory tract (URT) conditions. Administration of histamine and methacholine aerosols resulted in significant changes in all factor scores, although most of the observed changes were due to the effects of these aerosols on the respiratory rate. These findings re-emphasize the importance of the effects of respiratory rate on pulmonary mechanics. Application of the resistance resulted in significant changes in factor score 3, the 'inspiratory' factor, which lends support to the validity of this model for URT conditions. The close agreement between the factor scores obtained under controlled conditions in this study and in a previous study in this laboratory confirms that the factor analysis used for both of these studies provides an adequate means of reducing TBFVL data obtained from thoroughbred horses. The large intra- and inter-individual variation observed both with the indices of TBFVL and with the factor scores limits the potential of these variables for detecting individual animals with obstructive airway disease. Re-evaluation of these indices under the stress of exercise may reduce the variability observed in these data and may increase the magnitude of differences between different animals, providing a means of detecting individual animals with subclinical obstructive airway conditions.

Characterization of normal tidal breathing flow-volume loops for thoroughbred horses.

The purpose of this study was to characterize the normal equine tidal breathing flow-volume loop (TBFVL). The study was performed using 18 healthy Thoroughbred horses. TBFVLs constructed from data collected from resting horses had a typical biphasic inspiratory and expiratory phase. The interindividual variability of the indices used to describe TBFVLs was in the range 16-32%, which is comparable to the variability of other measures of equine pulmonary mechanics. The large variability of these data probably limits the value of resting TBFVL indices for detecting subclinical respiratory conditions in individual horses. Factor analysis of these data revealed that in excess of 90% of the variance of the initial response variables could be explained in terms of three common factors. Varimax rotation of these three common factors provided three subsequent factors that were readily identifiable as (1) a factor describing the time-volume relationships of TBFVLs, responsible for 81% of the total variance, (2) a factor explaining the expiratory portion of the TBFVL, explaining 12% of the variance, and (3) a factor describing the inspiratory portion of the loops, responsible for the remaining 7% of the variance. The analysis also provided standardized factor scoring coefficients for use in subsequent studies using similar experimental techniques.

Effect of head position on upper airway function in exercising horses

SummaryThe objective of the present study was to determine the effect of head and neck position on upper airway flow mechanics in exercising horses. Five Standardbred horses (452 ± 16.5 kg bwt; 4.7 ± 0.9 years [mean ± s.e.]) were exercised at 75% (Period A) and at 100% of maximal heart rate (Period B) with head and neck unrestrained, extended, or flexed. Airflow was measured using a facemask mounted pneumotachograph, while tracheal pressure during inhalation and exhalation (PUI and PUE) was measured using a nasotracheal catheter. With head and neck unrestrained, PUI, PUE, inspiratory and expiratory impedance (ZI, ZE), respiratory frequency (f) and indices describing the tidal breathing flow‐volume loops (TBFVLs) were similar to those previously reported. There were no significant changes in the extended position, except that expiratory time (Te) and ratio of peak expiratory flow and peak inspiratory flow (PEF/PIF) were significantly increased in Periods A and B, respectively. In contrast, in the flexed position, ZI was significantly increased in Period B. Also, inspiratory flow at 50% of tidal volume (IF50) was significantly decreased, and PEF/PIF and EF50/IF50 were significantly increased. At period A, PUI was increased and Te was prolonged. We conclude that during strenuous exercise head and neck extension has little effect on upper airway flow mechanics, but that head and neck flexion causes upper airway obstruction.

Tidal breathing flow-volume loops in horses with recurrent airway obstruction (heaves)

Summary Tidal breathing flow-volume (tbfv) loops were determined in a group of control horses and in horses affected with recurrent airway obstruction (heaves). The latter group was studied when the condition was in remission and under increasing amounts of airway obstruction as reflected by measurements of change in pleural pressure, pulmonary resistance, and dynamic compliance. The tbfv loops of control horses had biphasic inspiratory and expiratory patterns; peak inspiratory and peak expiratory flows were detected early in inspiration and expiration, respectively. Tidal volume was unaffected by heaves, but at all stages of heaves, respiratory frequency was increased principally because of shorter inspiratory time, and therefore, inspiratory flow rate was increased. In horses with heaves, tbfv loops did not have a biphasic pattern; peak inspiratory flow was observed late in inspiration, and peak expiratory flow was observed early in expiration. As airway obstruction became more severe, peak expiratory flow increased as pulmonary resistance increased so that, during severe airway obstruction, tbfv loops had a characteristic appearance with high peak expiratory flow early in expiration followed by low flow rate.