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Respiratory inductance plethysmography (RIP) is a method for respiratory measurements particularly attractive in infants because it is noninvasive and it does not interfere with the airway. RIP calibration remains controversial in neonates, and is particularly difficult in infants with thoraco-abdominal asynchrony or with ventilatory assist. The objective of this study was to evaluate a new RIP calibration method in preterm infants either without respiratory disease, with thoraco-abdominal asynchrony, or with ventilatory support. This method is based on (i) a specifically adapted RIP jacket, (ii) the least squares method to estimate the volume/motion ribcage and abdominal coefficients, and (iii) an individualized filtering method that takes into account individual breathing pattern. The reference flow was recorded with a pneumotachograph. The accuracy of flow reconstruction using the new method was compared to the accuracy of three other calibration methods, with arbitrary fixed RIP coefficients or with coefficients determined according to qualitative diagnostic calibration method principle. Fifteen preterm neonates have been studied; gestational age was (mean ± SD) 31.7 ± 0.8 weeks; birth weight was 1,470 ± 250 g. The respiratory flow determined with the new method had a goodness of fit at least equivalent to the other three methods in the entire group. Moreover, in unfavorable conditions—breathing asynchrony or ventilatory assist—the quality of fit was significantly higher than with the three other methods (P

Objective Air leakage is a major problem in long-term assisted ventilation both invasive and non-invasive that becomes even more important during sleep. The objective of this work was to provide a method for continuous estimation of tidal volume changes in patients under ventilatory support during sleep. Materials and methods Recordings were from 14 patients with neuromuscular disorders admitted to hospital for a routine evaluation of assisted ventilation during sleep. Air leakage was continuously evaluated from: 1) the difference between the insufflated and expired volume using a flow meter; 2) the changes in lung volume using inductance plethysmography. Results Both methods showed presence of air leaks in all patients and also variations in their amount throughout the night. However, inductance plethysmography provided more rigorous measurement of air leaks than flow meters as it measures the amount of air actually entering the lungs. The magnitude of leakage does not appear to be related to the method of assisted ventilation (invasive or non-invasive) or to the characteristic of the assistance mode (volume control or volume assist control). Conclusion The proposed method offers a reliable, non-invasive, continuous, bedside evaluation of air leak changes in ventilated patients. On-line analysis can be performed to find optimal ventilator settings in order to compensate for leakage while providing patient comfort.

To investigate the interindividual differences in respiratory sinus arrhythmia (RSA), recordings of ventilation and electrocardiogram were obtained from 12 healthy subjects for five imposed breathing periods ( TTOT) surrounding each individual's spontaneous breathing period. In addition to the spectral analysis of the R-R interval signal at each breathing period, RSA characteristics were quantified by using a breath-by-breath analysis where a sinusoid was fitted to the changes in instantaneous heart rate in each breath. The amplitude and phase (or delay = phase × TTOT) of this sinusoid were taken as the RSA characteristics for each breath. It was found that for each subject the RSA amplitude- TTOT relationship was linear, whereas the delay- TTOT relationship was parabolic. However, the parameters of these relationships differed between individuals. Linear correlation between the slopes of RSA amplitude versus TTOT regression lines and 1) mean breathing period and 2) mean R-R interval during spontaneous breathing were calculated. Only the correlation coefficient with breathing period was significantly different from zero, indicating that the longer the spontaneous breathing period the lesser the increase in RSA amplitude with increasing breathing period. Similarly, only the correlation coefficient between the curvature of the RSA delay- TTOT parabola and mean breathing period was significantly different from zero; the longer the spontaneous breathing period the larger the curvature of RSA delay. These results suggest that the changes in RSA characteristics induced by changing the breathing period may be explained partly by the spontaneous breathing period of each individual. Furthermore, a transfer function analysis performed on these data suggested interindividual differences in the autonomic modulation of the heart rate.

International audience; Studies of heart rate variability (HRV) have so far produced contradictory evidence to support the common belief that endurance training enhances cardiac parasympathetic tone. This may be related to the fact that most studies failed to specifically isolate the vagally mediated influence of respiration. This study used a cross-sectional comparison of endurance athletes (n=20; ATHL) exhibiting resting bradycardia and age-matched nonathletes (n=12; CRTL) to indirectly assess training effects on amplitude and timing characteristics of respiratory sinus arrhythmia (RSA). Continuous electrocardiogram (ECG) and ventilatory flows were recorded during spontaneous breathing (SP), as well as during breathing at four cycles less than (M4) or more (P4) than SP, to also examine potential repercussions of training on the sensitivity of the cardiac vagal responses to breathing. A fast Fourier transform procedure was used to quantify the standard spectral high-frequency (HF) and low-frequency (LF) components and a respiratory-centered frequency (RCF) component of HRV. RSA was assessed using a breath-by-breath quantification of the amplitude and timing of the maximum change in instantaneous heart rate. Under baseline SP conditions, heart rate was lower in ATHL (62.6+/-6.5 vs. 75.2+/-9 beats/min; p

Mentally imaged but unexecuted physical activity has been reported to induce a cardiorespiratory change. In order to test whether the previous experience of the performed exercise was a prerequisite to observe these changes, ventilation and heart rate were recorded during mental imagination of a rowing race in four groups of volunteers: 12 competitive rowers, 10 non-rower athletes, 12 students (22-30 years old) and 12 senior subjects (50-60 years old). Recordings were performed at rest, during the viewing of a rowing race and during mental imagination of this race. Analysis of variance revealed significant condition effect for all cardiorespiratory variables. All subjects increased their breathing rate (mean increase: 16 breaths.min(-1) in rowers, 8 breaths.min(-1) in athletes, 8 breaths.min(-1) in students, and 6 breaths.min(-1) in seniors), 29 decreased their tidal volume (mean decrease: 100 ml in rowers, 102 ml in athletes, 120 ml in students and 26 ml in seniors), with an increase in the resulting ventilation in 38 subjects (mean increase: 14 l.min(-1) in rowers, 3.6 l.min(-1) in athletes, 2.8 l.min(-1) in students, 2.6 l.min(-1) in seniors). Heart rate was increased in 34 subjects (mean increase: 12 beats.min(-1) in rowers, 5 beats.min(-1) in athletes, 6 beats.min(-1) in students and 5 beats.min(-1) in seniors). The number of subjects who exhibited changes was evenly distributed among the four groups. However, mean values of the changes were higher in rowers than in the three other groups, mainly due to three rowers who exhibited extremely large increases in cardioventilatory variables. Analysis of variance showed no significant group effect for heart rate and breathing rate. These results suggest that rowing experience may not be necessary for changes in heart rate and ventilation to be elicited by mentally imagining a rowing race.

Misunderstanding of the dynamical behavior of the ventilatory system, especially under assisted ventilation, may explain the problems encountered in ventilatory support monitoring. Proportional assist ventilation (PAV) that theoretically gives a breath by breath assistance presents instability with high levels of assistance. We have constructed a mathematical model of interactions between three objects: the central respiratory pattern generator modelled by a modified Van der Pol oscillator, the mechanical respiratory system which is the passive part of the system and a controlled ventilator that follows its own law. The dynamical study of our model shows the existence of two crucial behaviors, i.e. oscillations and damping, depending on only two parameters, namely the time constant of the mechanical respiratory system and a cumulative interaction index. The same result is observed in simulations of spontaneous breathing as well as of PAV. In this last case, increasing assistance leads first to an increase of the tidal volume (VT), a further increase in assistance inducing a decrease in VT, ending in damping of the whole system to an attractive fixed point. We conclude that instabilities observed in PAV may be explained by the different possible dynamical behaviors of the system rather than changes in mechanical characteristics of the respiratory system.

The addition to the respiratory system of a resistive load results in breathing pattern changes and in negative intrathoracic pressure increases. The aim of this study was to use resistive load breathing as a stimulus to the cardiorespiratory interaction and to examine the extent of the changes in heart rate variability (HRV) and respiratory sinus arrhythmia (RSA) in relation to the breathing pattern changes. HRV and RSA were studied in seven healthy subjects where four resistive loads were applied in a random order during the breath and 8-min recording made in each condition. The HRV spectral power components were computed from the R-R interval sequences, and the RSA amplitude and phase were computed from the sinusoid fitting the instantaneous heart rate within each breath. Adding resistive loads resulted in 1) increasing respiratory period, 2) unchanging heart rate, and 3) increasing HRV and changing RSA characteristics. HRV and RSA characteristics are linearly correlated to the respiratory period. These modifications appear to be linked to load-induced changes in the respiratory period in each individual, because HRV and RSA characteristics are similar at a respiratory period obtained either by loading or by imposed frequency breathing. The present results are discussed with regard to the importance of the breathing cycle duration in these cardiorespiratory interactions, suggesting that these interactions may depend on the time necessary for activation and dissipation of neurotransmitters involved in RSA.

We recorded by pneumotachography the breathing in nine patients with myotonic dystrophy (MD), both seated and supine and with eyes open in both positions. Irregular breathing (coefficient of variation >20% for VT and TTOT) was observed in six of the patients, two of whom showed irregularity in both positions whilst the remaining four had irregular breathing only when supine. In addition, in this latter group, irregularities first appeared in VT and only after a few minutes in TTOT. Whereas in the group exhibiting irregular breathing in both seated and supine positions, irregularities were observed throughout the recording. However, no significant difference in any ventilatory variable was observed as between the two postures. Rib cage (RC) and abdomen (AB) motions were recorded by uncalibrated respiratory inductance plethysmography. Although for MD patients the mean values of the RC/AB ratio lay within the normal range the relative decrease in value as between seated (0.78+/-0.52) and supine (0.31+/-0.13) position was less than in healthy subjects. These observations suggest that MD may cause deficiencies in several mechanisms. Analyses of the respiratory pattern in each patient may provide information leading to the identification of the impaired respiratory mechanisms.

The improvement in motor performance resulting from levodopa administration in patients with Parkinson’s disease (PD) provides the opportunity to investigate ventilatory changes brought about by the disease. The aim of this study has been to investigate these changes in order to specify the mechanisms of the impairment in breathing in PD. Breathing patterns at rest were investigated in 11 patients with idiopathic PD both before (O ff ) and after (O n ) administration of levodopa at a dose improving their motor performance by at least 30%. Airflow (Fleisch head mounted on a mask), rib cage and abdomen movements (inductance plethysmography) were recorded in the O ff condition 1 h after subjects woke up. Subjects then received levodopa and a new set of recordings was obtained 1 h later, in the O n condition. Breath-by-breath processing of recordings was carried out and tidal volume (V t ), inspiratory (T i ) and expiratory (T e ) durations were measured. The main finding was a lengthening of T i resulting in a decrease in ventilation and in V t /T i, and an increase in T i /T tot in the O n compared to the O ff condition. In the O n condition abnormal rib cage–abdomen plots patterns were found in four out of six subjects. A hypothesis on the effect of PD on breathing is proposed on grounds of normal diaphragmatic activity but impaired activity of the other respiratory muscles and more specifically the intercostal muscles.

In order to determine changes in breathing patterns brought about by resistive loading, ventilation was recorded in 11 healthy subjects with four linear resistances (3.57, 5.75, 8.76 and 13.13 cmH 2 O L −1 sec) added in a random order throughout the entire breath. At steady state, a breath-by-breath analysis of airflow was used to quantify the pattern of breathing in terms of respiratory variables: T i , T e , Tt, V t , V t /T i , T i /Tt, and by taking T i , T e , V t all together (TRIAD) and also the shape of the entire airflow profile quantified by harmonic analysis (ASTER). Group analysis using ANOVA showed significant changes in all variables. There were increasing changes with increasing loads in all variables, the smallest changes being in T i /Tt. Within to between-individual comparisons between two loads showed that only T i /Tt and the ASTER were more similar within than between-individuals for all comparisons. It was concluded that at steady state mechanisms of load compensation come into play inducing changes in the pattern of breathing proportional to the loads while maintaining some of the individual characteristics.

Objective To assess the accuracy of respiratory inductive plethysmography (RIP) waveforms to those obtained with whole body plethysmograph (BP) as this device gives a plethysmographic signal and a pneumotachograph (PNT). Design Randomized controlled trial. Setting Physiologic laboratory in a university hospital. Participants Eleven subjects from the laboratory staff. Interventions This study was achieved during four consecutive periods in subjects breathing spontaneously and through different added resistive loads. Using the least square method calibration, two RIP waveforms, VRIP.BP(t) and VRIP.PNT(t), were simultaneously calculated with coefficients obtained from BP and from PNT volume waveforms, respectively VBP(t) and VPNT(t). For each recording, to compare volume waveforms, we calculated their differences in term of distances, DRIP-BP and DRIP-PNT, between the normalized RIP volume signal (respectively, V _ RIP.BP[t] and V _ RIP.PNT[t]) and its normalized reference (respectively, V _ BP[t] and V _ PNT[t]). We also calculated the distance DPNT-BP between the two normalized references V _ BP(t) and V _ PNT(t). Results No significant effect of load or time on the distance occurred. Including all the recordings, the mean distance DRIP-BP (3.4±1.1%) appears significantly lower than both the mean distance DRIP-PNT (4.5±1.3%; p Conclusion The RIP seems reasonably accurate for analysis of respiratory waveform while subjects subsequently breathe against resistive loads.

Fourteen subjects learned to adjust their breath pattern to two target breaths displayed on a video screen, by using visual feedback, during two sessions 24 h apart. These two targets were respectively the smallest and the largest breaths of a ten-breath sample previously recorded from each subject's resting spontaneous breathing. Performances were significantly better for the large than for the small target breath. This cannot be directly inferred from current knowledge related to the control of movement time and amplitude, but rather it may be inferred from the periodic character of breathing, to the higher mental load during the small breath task, or to the presumably different frequencies of target breaths in the whole span of spontaneous breathing. In the second session, performance on the two targets levelled out as a result of learning.

Background: Analysis of breath-to-breath variability of respiratory characteristics provides information on the respiratory control. In infants, the control of end-expiratory lung volume (EELV) is active and complex, and it can be altered by respiratory disease. The pattern of EELV variability may reflect the behavior of this regulatory system. Objectives: We aimed to characterize EELV variability in premature infants, and to evaluate variability pattern changes associated with respiratory distress and ventilatory support. Methods: EELV variations were recorded using inductance plethysmography in 18 infants (gestational age 30–33 weeks) during the first 10 days of life. An autocorrelation analysis was conducted to evaluate the ‘EELV memory’, i.e. the impact of the characteristics of one breath on the following breaths. Results: In infants without respiratory symptoms, EELV variability was high, with large standard deviations of EELV. Autocorrelation was found to be significant until a median lag of 7 (interquartiles: 4–8) breaths. Autocorrelation was markedly prolonged in patients with respiratory distress or ventilatory support, with a higher number of breath lags with significant autocorrelation (p < 0.01) and higher autocorrelation coefficients (p < 0.05). Conventional assisted ventilation does not re-establish a healthy EELV profile and is associated with lower respiratory variability. Conclusions: In premature infants, EELV variability pattern is modified by respiratory distress with a prolonged ‘EELV memory’, which suggests a greater instability of the control of EELV.

Respiratory inductance plethysmography (RIP) is a method for respiratory measurements particularly attractive in infants because it is noninvasive and it does not interfere with the airway. RIP calibration remains controversial in neonates, and is particularly difficult in infants with thoraco-abdominal asynchrony or with ventilatory assist. The objective of this study was to evaluate a new RIP calibration method in preterm infants either without respiratory disease, with thoraco-abdominal asynchrony, or with ventilatory support. This method is based on (i) a specifically adapted RIP jacket, (ii) the least squares method to estimate the volume/motion ribcage and abdominal coefficients, and (iii) an individualized filtering method that takes into account individual breathing pattern. The reference flow was recorded with a pneumotachograph. The accuracy of flow reconstruction using the new method was compared to the accuracy of three other calibration methods, with arbitrary fixed RIP coefficients or with coefficients determined according to qualitative diagnostic calibration method principle. Fifteen preterm neonates have been studied; gestational age was (mean +/- SD) 31.7 +/- 0.8 weeks; birth weight was 1,470 +/- 250 g. The respiratory flow determined with the new method had a goodness of fit at least equivalent to the other three methods in the entire group. Moreover, in unfavorable conditions--breathing asynchrony or ventilatory assist--the quality of fit was significantly higher than with the three other methods (P0.05, repeated measures ANOVA). Accuracy of tidal volume measurements was at least equivalent to the other methods, and the breath-by-breath differences with reference volumes were lower, although not significantly, than with the other methods. The goodness of fit of the reconstructed RIP flow with this new method--even in unfavorable respiratory conditions--provides a prerequisite for the study of flow pattern during the neonatal period.

the characteristic pattern of breathing for an individual when awake at rest may be due to forebrain influences upon breathing. To examine this hypothesis we have studied the breathing pattern in 18 healthy subjects during relaxed wakefulness (W) and during Stage 4 sleep (S4), when forebrain influences upon breathing are absent or minimal. Inspiratory and expiratory times, respiratory frequency, tidal volume, and ventilation were quantified noninvasively by respiratory inductance plethysmography. The stability of respiratory variables between W and S4 sleep was tested within individuals. The results show that (i) individuals breathe differently from each other when awake and when in S4 sleep; the range between individuals during sleep being as large as it is when awake; (ii) differences in breathing pattern between two S4 periods within an individual are relatively small; (iii) the characteristic breathing pattern of an individual when awake tends to be maintained in S4 sleep. This persistence of a respiratory ‘personality’ into S4 sleep probably indicates that there are individual differences in respiratory rhythm generation in the absence of any forebrain influences upon breathing.

It is essential to have a user-friendly, noninvasive bedside procedure at our disposal in order to study swallowing and swallowing disorders in the elderly in view of the frailty of this age group. In the present work, respiratory inductance plethysmography (RIP) is proposed as an appropriate clinical tool for such studies. An automated process for the detection of swallowing is used involving the derivative of the respiratory volume signal. The accuracy of the automated detection is given by the area under the Receiver Operating Characteristic (ROC) curve and is found to be greater than 0.9. At the optimal threshold, RIP constitutes a reliable and objective bedside clinical tool for studying swallowing in the elderly, as well as being user-friendly and noninvasive. In addition, RIP can be used to monitor swallowing in order to analyze swallowing disorders and put in place medical supervision of swallowing for individuals who might aspirate.

Deglutition disorders can occur at any age but are especially prevalent in the elderly. The resulting morbidity and mortality are being recognized as major geriatric health issues, Because of difficulties in studying swallowing in the frail elderly, a new, non-invasive, user-friendly, bedside technique has been developed. Ideally suited to such patients, this tool, an intermediary between purely instrumental and clinical methods, combines respiratory inductance plethysmography (RIP) and the computer to detect swallowing automatically, Based on an automated analysis of the airflow estimated by the RIP-derived signal, this new tool was evaluated according to its capacity to detect clinical swallowing from among the 1643 automatically detected respiratory events, This evaluation used contingency tables and Receiver Operator Characteristic (ROC) curves, Results were all significant (chi2(1,n=1643)100, p0.01). Considering its high accuracy in detecting swallowing (area under the ROC curve greater than 0.9), this system would be proposed to study deglutition and then deglutition disorders in the frail elderly, to set up medical supervision and to evaluate the efficiency of a swallowing disorder remedial therapeutic.

Summary.-15 asthmatic children and 15 healthy children were trained to adjust their breathing pattern to a target pattern displayed on a video screen by using visual feedback. The error scores in the two groups were not significantly different. These data did not support the hypothesis chat voluntary control of respiratory muscles is impaired in asthmatics. Patients with ventilatory disorders currently practice breathing exercises to improve their ventilatory function. These exercises require a ab~lity to voluntarily control the respiratory muscles. A recent study indicated that patients with chronic obstructive pulmonary disease (COPD) performed a ventilatory traclung task with more errors than healthy subjects (Cohen, Murphy, Adams, Guz, & Benchetrit, 1995); however, this difference was accounted for by lunited expiratory flow rather than the ability to voluntarily control the breathing pattern per se. The aim of the present experiment was to assess whether asthma is associated with an abnormal capacity to control respiratory muscles voluntarily. We compared the abilities of asthmatic and normal subjects to perform a ventilatory motor skill which required adjusting the breathing pattern to a target pattern displayed on a video screen.

The obstructive syndrome of sleep apnea/hypopnea is characterized by repeated partial or total obstructions of the upper airways (UA) [1] resulting in intermittent asphyxia and repeated micro-arousals. Sleep disordered breathing affects about 9% of males and 4.5% of females between the ages of 30 and 60 years [2], 15% to 20% of elderly people [3] and 5% to 10% of children [4]. Sleep apnea and hypopnea events are easily identified while more subtle events, such as inspiratory flow limitation episodes, are difficult to detect. Flow limitation is the result of a partial occlusion of the upper airway during sleep.

Every time the heart beats, it produces a mechanical deformation of the lungs causing small fluctuations of airway pressure and flow called cardiogenic oscillations (CO). CO have been observed on respiratory signals during pulmonary function tests, during relaxed expiration as well as during apnea, as a mean for differentiating central and obstructive apneas1. Finally, we have recently shown that the processing of CO in mouth pressure and airflow can be used as a non-invasive measurement of airway resistance2.

The ventilatory system as many biological systems is a complex dynamical one involving many controls and regulations. More over, in a reconstructed phase space respiratory data present a structure similar to a strange attractor (cf. Figure 1). In this way, considering the respiratory system as a deterministic chaotic one seems to be a good hypothesis to understand breathing and its variability. This hypothesis remains controversial. Donaldson (1992) shows that respiratory trajectories of resting human are not random but chaotic using the Largest Lyapunov Exponent (LLE). Unfortunately, Hughson et al. (1995) said that previous suggestion of Donaldson (1992) that human respiratory pattern was chaotic appears from the outcome of surrogate data analysis in their study to have been premature. Similarly, Fortrat et al. (1997), in human resting breathing could not conclude that ventilation derive from a deterministic chaotic system. On the contrary, Sammon et al. (1991, 1993a, 1993b) show that irregular inspiratory-expiratory phase switching and central respiratory pattern generator (CRPG) output in rats are consistent with low-dimensional chaos. Small et al. (1999) bring evidence that respiratory variability in infants during quiet sleep is deterministic and not random. Starting from the hypothesis that controlling the presence of chaos by changing a parameter of a system brings further evidence of the chaotic nature of the system we tried to modify, experimentally and on simulations, the chaotic dimension of the ventilatory system by changing the resistive load in resting breathing human.

Misunderstanding of the dynamical behavior of the ventilatory system, especially under assisted ventilation, may explain the problems encountered in ventilatory support monitoring. Proportional assist ventilation (PAV) that theoretically gives a breath by breath assistance presents instability with high levels of assistance. We have constructed a mathematical model of interactions between three objects: the central respiratory pattern generator modelled by a modified Van der Pol oscillator, the mechanical respiratory system which is the passive part of the system and a controlled ventilator that follows its own law. The dynamical study of our model shows the existence of two crucial behaviors, i.e. oscillations and damping, depending on only two parameters, namely the time constant of the mechanical respiratory system and a cumulative interaction index. The same result is observed in simulations of spontaneous breathing as well as of PAV. In this last case, increasing assistance leads first to an increase of the tidal volume (VT), a further increase in assistance inducing a decrease in VT, ending in damping of the whole system to an attractive fixed point. We conclude that instabilities observed in PAV may be explained by the different possible dynamical behaviors of the system rather than changes in mechanical characteristics of the respiratory system.

International audience; We deal in this paper with the concept of health smart home (HSH) designed to follow dependent people at home in order to avoid the hospitalisation, limiting hospital sojourns to short acute care or fast specific diagnostic investigations. For elderly people the project of such a HSH has been called AISLE (Apartment with Intelligent Sensors for Longevity Effectiveness). For this purpose, system having three levels of automatic measuring (1) the circadian activity, (2) the vegetative state, and (3) some state variables specific of certain organs involved in precise diseases, has been developed within the framework of a 'Health Integrated Smart Home Information System' (HIS2). HIS2 is an experimental platform for technologic development and clinical evaluation, in order to ensure the medical security and quality of life for patients who need home based medical monitoring. Location sensors are placed in each room of the HIS2, allowing the monitoring of patient's successive daily activity phases within the patient's home environment. We proceed with a sampling in an hourly schedule to detect weak variations of the nycthemeral rhythms. Based on numerous measurements, we establish a mean value with confidence limits of activity variables in normal behaviour permitting to detect for example a sudden abnormal event (like a fall) as well as a chronic pathologic activity (like a pollakiuria), allowing us to define a canonical domain within which the patient's activity is qualified to be 'predictable'. Alerts are set off if the patient's activity deviates from a predictable canonical domain. Moreover, we can follow the cardio-respiratory state by measuring the intensity of the respiratory sinusal arrhythmia in order to quantify the integrity of the bulbar vegetative system, and we finally propose to carefully watch abnormal symptoms like arterial pressure or presence of plasma proteins in the expired air flow for early detecting respectively hypertension or pulmonary oedema.

The use of respiratory inductance plethysmography (RIP) for measurement of breathing is appealing not only because of its noninvasive nature but also because it provides rib cage and abdomen cross sectional area changes.

In adult awake human subjects at rest, there exists a diversity in the breathing pattern not only in terms of tidal volume and inspiratory and expiratory duration and derived variables (TTOT, VT/TI and TI/TTOT) but also in the airflow profile. Besides this diversity, in every recording of ventilation at rest in steady-state condition breath-to-breath fluctuations are observed in ventilatory variables. This variability is non random and may be explained either by a central neural mechanism or by instability in the chemical feedback loops. Beyond this variability, each individual appears to select one particular pattern among the infinite number of possible combination of ventilatory variables and airflow profile. This one particular pattern appears to be a relatively stable characteristic of an adult individual being reproducible in several conditions and above all, after a long period of time. Consequences of this individuality of breathing pattern are discussed with regard to the selection of control subjects for a study and also per se: are there physiological situations where differences may be observed solely because of the differences in the pattern of breathing?

International audience; OBJECTIVE: Measurement of capillary-alveolar permeability to fluorescein isothiocyanate-dextran (FITC-D) (molecular mass, 71,300 daltons) by a sequential bronchoalveolar lavage (BAL) technique. DESIGN: Animal research. SETTING: The Department of Physiology at a scientific and medical university. SUBJECTS: Nine anesthetized and mechanically ventilated dogs. INTERVENTIONS: Two separate experiments were performed in each subject-an initial control experiment followed by an oleic acid-induced lung injury. The indicator was administered at constant blood concentration before serial BAL including eight fluid instillation-recovery cycles. MEASUREMENTS: Plasma to BAL solute clearance at saturation (capillary-alveolar clearance at saturation, mL/min) was calculated and normalized to lavage fluid volume (measured by 1251 serum albumin dilution) to obtain a transport rate (TR) constant. MAIN RESULTS: TR for FITC-D70 was 4.0+/-0.8 and 46.1+/-18.1 x 10(-5) x min(-1) in control and injured lung, respectively (p < .02). Capillary-alveolar clearance of FITC-D70 was not affected by the lavage procedure itself. TR reflected essentially epithelial permeability in normal lung and combined epithelial and endothelial permeability in injured lung. A significant correlation was found between cardiac output and TR in injured lung. CONCLUSIONS: Saturation BAL allowed us to estimate capillary-alveolar macromolecule permeability in vivo in dogs. Further study may allow bedside evaluation of lung injury by BAL in patients.

The purpose of this study was to assess the effects of a particular breathing pattern training (BPT) on forced expiratory volume during the first second (FEV1) and forced vital capacity (FVC) in patients with chronic obstructive pulmonary disease (COPD). The subjects adjusted each breath to a target breath displayed on a video screen, by using visual feedback. This target was chosen in an individual sample recorded at rest. We used a randomized, controlled group design. Twenty patients with stable COPD, FEV1 less than 1.5 liters, undergoing a traditional rehabilitation program were randomly assigned to the BPT group or to the control group. Each BPT subject underwent 30-35 training sessions spread out over four weeks, in addition to the traditional program. FEV1 and FVC were performed before and after this program. ANOVAs showed that FEV1 and FVC significantly improved in BPT subjects, with a mean percent increase of 22% and 19%, respectively. Corresponding changes in controls were not significant. This study showed short-term increases in FEV1 and FVC in COPD patients practicing BPT in addition to respiratory rehabilitation, in comparison with controls. Further studies should incorporate outcome data to clarify the mechanisms and the duration of this effect.

1. To assess whether voluntary control of breathing is impaired in patients with chronic obstructive pulmonary disease, a group of such patients performed a tracking task, requiring volitional control of respiratory muscles. 2. Eight patients (mean age 60 years; mean ratio of forced expiratory volume in 1 s to forced vital capacity = 31%) took part in the study. Five of the seven patients in whom blood gas measurements were made were mildly hypoxaemic (Pao2 = 53–71 mmHg), and one of these was hypercapnic (Paco2 = 55 mmHg). Each subject performed a compensatory ventilatory tracking task using a tracking system which comprised a fixed target displayed on a monitor screen and a cursor moving in a line bisecting the target. The position of the cursor was perturbed by a forcing function and patients were required to keep the cursor on the target by breathing in and out of a spirometer. 3. To allow for any non-specific deficiency in motor control, patients performed a similar manual tracking task, using their dominant arm to move a joystick. As a control group, 11 healthy subjects (mean age 58 years; mean ratio of forced expiratory volume in 1 s to forced vital capacity = 77%) underwent an identical experimental protocol. 4. Motor control performances were measured in terms of the error between the target position and the subject's positioning of the cursor. Indices of performance were the root mean square of the error and the averages of the zero errors (i.e. end expiration/arm movement towards the trunk) and the peak errors (i.e. end inspiration/arm movement from the trunk). 5. For manual tracking, patients with chronic obstructive pulmonary disease, were not significantly different from control subjects in terms of mean root mean square (69.3 versus 60.9), mean zero error (93.8 versus 72.2) or mean peak error (99.5 versus 82.7). For ventilatory tracking, mean root mean square was significantly higher in patients (83.4 versus 65.9). This was due to a significantly higher mean zero error (101.4 versus 66.1); mean peak error was not significantly different (68.3 versus 82.1). Comparison of flows achieved during ventilatory tracking with those possible during a maximal forced expiratory manoeuvre in the patients suggested that poor expiratory control in this group could be explained by their degree of airflow limitation rather than a deficiency in motor control per se. 6. These results provide no evidence that patients with chronic obstructive pulmonary disease have any impairment in their voluntary motor control of breathing.

When we periodically perturbed the central respiratory oscillator with a controlled periodic stimulation provided by a mechanical ventilator, an entrainment phenomenon occurred: the actual rhythm of the respiratory centres was phase locked to the periodic stimulation. In some experiments, we observed an intermittence phenomenon: the respiratory rhythm successively seemed entrained, departed from this mode for few cycles, returned to the previous pseudo entrainment and so on. From intermittence data, we were able to plot a phase response curve. From literature data on the effects of a single stimulation applied at various moments in the respiratory cycle, we built up a mathematical model designed to simulate entrainment experiments. This model simulated entrainment phenomenon, but did not satisfactorily accommodate the experimental phase response curve. The section of the simulated phase response curve responsible for discrepancies was the result of the combination of an inspiratory shortening owing to a stimulation occurring during inspiration, and a positive relationship between inspiratory duration TI and expiratory duration TE. We changed the TE —TI relationship, assuming that the expiratory duration is determined not by the inspiratory duration but rather by the lung volume at the end of inspiration. The revised model was then able to exhibit almost all the qualitative properties previously noted in experiments. The significance in biological terms of the new TE —TI relationship, which is apparently incompatible with almost all previous experimental data, is discussed.

To the Editor: The manuscript by Drs. Sato and Robbins ([3][1]) presents a new method for determining average flow profiles. The resulting average flow profiles are compared with those obtained with our method ([2][2]). It is noteworthy that the method of flow profile analysis we used was first

A new device for pulmonary rehabilitation based on visual feedback has been developed. It has been derived from the notion of respiratory "personality", its purpose is to assist therapists in practising the patient's pulmonary rehabilitation. Ventilatory movements are recorded using a respiratory inductance plethysmography coupled with a computerized acquisition system.

A computer program for pulmonary rehabilitation utilizable with common PC in physiotherapist office has been developed. The main phases of this program are to process the respiratory inductance plethysmograph signals in real time for recording and working sessions, and to build the "mould" from an "ideal" cycle.

In anesthesized, paralyzed, and mechanically ventilated rabbits, the rate and duration of airflow were varied to investigate the effect on the central respiratory rhythm during 1:1 entrainment (1 phrenic nerve burst for 1 pump inflation). Our results showed that 1) the largest range of 1:1 entrainment was obtained with the longest inflation durations associated with the lowest flow rates and 2) both inspiratory (TI) and expiratory (TE) durations (as estimated by the period of phrenic nerve activity and phrenic nerve silence, respectively) increased when total respiratory duration (TT = TI+TE) increased. The phase relationships we studied were DI (the time elapsing between the onset of phrenic activity and the beginning of pump inflation) and DE (the time between the end of phrenic activity and the end of pump inflation). Both DI and DE increased when the total ventilatory period increased. However, for constant ventilatory period, DI changed with the rate and duration of airflow, whereas DE remained constant. In addition, under these conditions, TI, TE, and the integrated phrenic nerve activity remained constant independently of airflow rate and duration. The present results are discussed with regard to the pulmonary receptors (slowly and rapidly adapting receptors and C fibers) that are stimulated during mechanical ventilation, and hypotheses are drawn regarding their possible contribution to rhythm generation and the mechanism through which they may act.

Sixteen healthy adult subjects underwent two studies separated by 4-5 years to test whether their resting pattern of breathing was reproducible over time. From breath-by-breath analysis of airflow, measured with a pneumotachometer, the pattern of breathing was quantified in terms of individual respiratory variables; inspiratory time (TI), expiratory time (TE), total breath duration (TTOT), tidal volume (VT), VT/TI, TI/TTOT, and by taking TI, TE and VT all together (TRIAD). Also, the shape of the entire airflow profile was quantified by harmonic analysis (ASTER). A statistical analysis was designed to compare differences between the 1st and the 2nd recording within individuals with those differences observed between random pairs of recordings from the two studies in the same 16 individuals. It was found that all variables were significantly more similar within-individuals than between-individuals; this is best demonstrated when considering the ASTER and/or the TRIAD. It was concluded that the individuality of breathing pattern is maintained over a long period despite changes in smoking habit, weight, mild respiratory diseases, and other changes which occurred between the two studies in our subjects.

The existence of a characteristic pattern of breathing for each individual, when awake at rest, has previously been demonstrated1,2. In an endeavour to measure an individual’s breathing pattern when awake at rest it is desirable, but difficult, to minimise forebrain influences upon breathing3. No matter how careful one is in controlling the experimental conditions, one can never be certain that such forebrain influences are absent and it is possible that they account for an individual’s particular breathing pattern when at rest i.e. when respiratory ‘drive’ is minimal.

In awake man, voluntary and involuntary forebrain influences can interact with and can override the automatic control of breathing. These ‘behavioural’ influences diminish as the metabolic demands increase (Asmussen, 1977; Morgan & Cameron, 1985) having therefore their greatest potential effect upon breathing during relaxed wakefulness. A probable example of a behavioural influence was documented by Asmussen (1977) who showed that subjects increase their ventilation significantly when they merely open their eyes to read. We have recently repeated Asmussen’s experiment but with noninvasive techniques and an improved experimental design (Shea et al, 1987). We found that breathing is stimulated in a small (approx 6%) but consistent manner by opening the eyes to read and that it is also stimulated when the eyes are opened without reading. Similar changes in breathing were found when auditory stimulation was added to the baseline condition with eyes closed. Breathing was stimulated more when the auditory or visual stimuli had ‘meaning’ ie. reading or listening to a story.

A computer program for cycle-by-cycle analysis and quantification of biological rhythms, written for an Apple II microcomputer with 48k RAM is described. The program comprises 4 steps: (1) file constitution suitable for biological data collecting; (2) signal digitalization at a sampling rate up to 1 kHz with storage in central memory; (3) determination of each cycle's limits (delimitation parameters being defined by the user; following delimitation, cycles may be dropped or saved for further analyses); (4) cycle-by-cycle harmonic analysis (fast Fourier Transform algorithm). The program is written in BASIC Applesoft, hardware-dependent functions (analog inputs, graphic display and random access disk storage) are implemented in subroutines (partly assembler) which may be easily modified. The program, consisting of 4 chained procedures is run interactively, although procedure (4) may be run automatically. Analysis of human ventilatory airflow signal with this program is given as an example of cycle-by-cycle shape analysis of a biological rhythm.

The aim of this study was to determine whether pulmonary receptors other than slowly adapting stretch receptors are capable of entraining the respiratory rhythm when periodically stimulated during artificial ventilation. Experiments were performed on anaesthetised (urethane, 1.5 g/kg) and paralysed (pancuronium bromide, 0.1 mg/kg) rabbits. Vagi were cooled in order to block conduction in the myelinated fibres innervating slowly adapting receptors. The effectiveness of this cooling was assimilated to the absence of the Hering-Breuer inflation reflex and the presence of the deflation reflex. Our results indicate that under such conditions: (1) harmonic entrainment (one phrenic burst for one pump period) can be observed, (2) the range of harmonic entrainment is more limited when the vagi are cooled, and (3) during harmonic entrainment the inspiratory duration and phrenic activity are similar to what is observed at the same period with intact vagi, whereas vagal cooling modifies the phase difference between the phrenic burst and the pump. We have concluded that periodic input from rapidly adapting receptors and/or vagal C-fibres can entrain the respiratory rhythm as does input from slowly adapting receptors but with different patterns as evidenced by phase relationship.

Which variables are important in the description of the pattern of breathing? The answer, of course, will depend upon the hypothesis which is being tested. Traditionally, people have studied TI, TE, VT and/or other variables1 derived from these three “primary variables” e.g. f, VT/TI TI/TTOT. Further information is carried in the shape of the airflow profile and this may be pertinent to some investigations. Since Fleisch’s;2 first recordings of the pneumotachogram in 1925, interest in its functional significance has been generated though problems existed in the method of description and quantification of the pneumotachogram. For example, Proctor and Hardy3 found that there were global qualitative differences in the pneumotachogram between people but that single measurement of slopes, ratios or instantaneous flows failed to yield significant differences between people. These authors suggested that such “methods of quantitative analysis may not include the fundamental characterisctics of the pattern. Perhaps an analysis of the total shape of the curve is required”. Gray and Grodins,4 have further proposed that “transformation of the tracings to a completely non-dimensional form should be the first step in analyzing the significance of their shape”.

Several models of oscillators defined by a system of non-linear differential equations have been built which simulate quite well some entrainment characteristics of the respiratory system: the range of entrainment, positioning of the stimulus at entrainment and the variation of inspiratory duration with entrainment periods. The construction of the model has been guided by consideration of the isochron configuration and the phase response curve of the system, which may yield a good qualitative fit between simulation and experimental results.

We propose in this paper to derive a new relationship between the successive inspiratory and expiratory durations of the same respiratory cycle, from the discrepancy observed between experimental data of entrainment and theoretical results obtained by simulation of a model we have previously described.

Respiratory inductance plethysmography was used to measure thoracic and abdominal surfacearea changes in order to 1) detect inspiratory flow limitation induced using a devicedeveloped in our laboratory in healthy awake subjects; the detection method was based on theanalysis of the shape of the abdominal signal, 2) evaluate respiratory volume variations inorder to estimate air leaks during sleep in ventilated patients with neuromuscular disease;variations in the amplitude of thoracic and abdominal signals were used for this evaluation,and 3) detect swallows following water ingestion in elderly subjects; this detection used theflow signal obtained by differentiating the volume signal calculated from thoracic andabdominal signals. None of the three analyses required calibration of the respiratoryinductance plethysmography system.; Les signaux des variations de sections thoracique (Tho) et abdominale (Abd) obtenus parpléthysmographie respiratoire par inductance ont été analysés pour 1) détecter des limitationsinspiratoires de débit chez le sujet sain induites à l'aide d'un dispositif mis au point aulaboratoire; cette méthode de détection est basée sur l'analyse de la forme du signal Abd, 2)évaluer les variations de volume pulmonaire afin d'en déduire l'évolution des fuites au coursde la nuit, chez des patients ayant des maladies neuromusculaire sous ventilation assistée;pour faire cette évaluation, les variations d'amplitudes des signaux Tho et Abd ont étéutilisées et 3) détecter les déglutitions provoquées par ingestion d'eau chez des personnesâgées; cette détection utilise le signal débit, obtenu par dérivation du signal volume calculé àpartir des signaux Abd et Tho. Aucune de ces trois analyses n'a nécessité l'étalonnage dusystème de pléthysmographie respiratoire par inductance.

Respiratory inductance plethysmography was used to measure thoracic and abdominal surfacearea changes in order to 1) detect inspiratory flow limitation induced using a devicedeveloped in our laboratory in healthy awake subjects; the detection method was based on theanalysis of the shape of the abdominal signal, 2) evaluate respiratory volume variations inorder to estimate air leaks during sleep in ventilated patients with neuromuscular disease;variations in the amplitude of thoracic and abdominal signals were used for this evaluation,and 3) detect swallows following water ingestion in elderly subjects; this detection used theflow signal obtained by differentiating the volume signal calculated from thoracic andabdominal signals. None of the three analyses required calibration of the respiratoryinductance plethysmography system., Les signaux des variations de sections thoracique (Tho) et abdominale (Abd) obtenus parpléthysmographie respiratoire par inductance ont été analysés pour 1) détecter des limitationsinspiratoires de débit chez le sujet sain induites à l'aide d'un dispositif mis au point aulaboratoire; cette méthode de détection est basée sur l'analyse de la forme du signal Abd, 2)évaluer les variations de volume pulmonaire afin d'en déduire l'évolution des fuites au coursde la nuit, chez des patients ayant des maladies neuromusculaire sous ventilation assistée;pour faire cette évaluation, les variations d'amplitudes des signaux Tho et Abd ont étéutilisées et 3) détecter les déglutitions provoquées par ingestion d'eau chez des personnesâgées; cette détection utilise le signal débit, obtenu par dérivation du signal volume calculé àpartir des signaux Abd et Tho. Aucune de ces trois analyses n'a nécessité l'étalonnage dusystème de pléthysmographie respiratoire par inductance.

The aim of this work has been to propose a new method for measuring respiratory resistances. This method is based on differences between Rib Cage and Abdomen surface area changes measured by inductance plethysmography. These differences were assessed by various calculation of a Rib Cage-Abdomen distance. Distance between asters (aster = vectorial representation of first four harmonics of the Fourier analysis performed on each breath) appeared to be the most sensitive and reproducible and the less variable. This distance increases significantly in healthy subjects with resistive loads (3 à 13 cmH2O.l-1.s) added during the whole breath, both seated and supine. The distance-resistance regressions lines are parallel for all subjects. This result suggests the possibility for evaluating changes in respiratory resistance by using a pooled slope. An assessment of the method was carried out using recordings performed during methacholine-induced changes in airway resistances. It was found that the Rib Cage-Abdomen distance did not increase with the airway resistance as measured by whole body plethysmography for the whole group of subjects. The resistive loading in healthy subjects resulted in (1) a significant increase in inspiratory and expiratory duration, in tidal volume, a slight decrease in minute ventilation as assessed by slight changes in end tidal CO2, whereas there were no changes in the airflow profile and inspiratory /total duration ratio, and (2) no changes in the mean heart rate but an increase in heart rate variability, due mainly to an increase in respiratory sinus arrhythmia. No significant changes were observed in the specific indicies of respiratory sinus arrhythmia, when comparing breathing at a respiratory frequency obtained by adding a resistive load to breathing at the same imposed respiratory frequency., L'objectif premier de ce travail a été la mise au point d'une méthode nouvelle d'évaluation des résistances respiratoires, basée sur les différences entre les variations de sections du thorax et de l'abdomen, mesurées par pléthysmographie à variation d'inductance. L'évaluation de cette différence a été examinée par différentes formulations de la distance Thorax-Abdomen. C'est la distance entre asters (aster : représentation vectorielle des quatre premières harmoniques d'une décomposition en série de Fourier de chaque cycle respiratoire), qui présente la plus grande sensibilité, la plus faible variabilité et la meilleure reproductibilité. Chez des sujets sains, cette distance augmente significativement avec des charges résistives croissantes (3 à 13 cmH2O.l-1.s), additionnées sur la totalité du cycle respiratoire, aussi bien dans la position assise qu'en décubitus dorsal. Les droites de régressions distances-résistances des différents sujets, sont parallèles entre elles, suggérant la possibilité d'utiliser une droite de pente commune pour évaluer les variations de résistance respiratoire. Un essai de validation de la méthode, au cours de tests à la méthacholine, ne nous a pas permis de montrer une augmentation de la distance Thorax-Abdomen avec la résistance des voies aériennes, mesurée par pléthysmographie corporelle, chez tous les sujets. Au cours d'addition de charges résistives chez le sujet sain, l'étude des caractéristiques ventilatoires et de la variabilité cardiaque a montré (1) une augmentation significative des durées inspiratoires et expiratoires et du volume courant, une faible diminution de la ventilation minute comme en témoigne les faibles variations de la teneur en CO2 du gaz expiré, alors que la forme des cycles respiratoires et le rapport durée inspiratoire/durée totale restent inchangés, et (2) pas de modification de la valeur moyenne de la période cardiaque mais une augmentation de la variabilité, essentiellement en raison d'une augmentation de l'arythmie sinusale d'origine respiratoire. Il n'existe pas de différence significative entre les indices spécifiques de l'arythmie sinusale d'origine respiratoire, à une même fréquence respiratoire, qu'elle résulte d'une addition de résistance ou qu'elle soit obtenue par une ventilation à fréquence imposée.