Biomedical subjects

M A Sackner

Publications and source records attributed to M A Sackner.

At least 55 records · Page 3Linked to original sources

PubMed1987

Oropharyngeal deposition and delivery aspects of metered-dose inhaler aerosols.

Oropharyngeal deposition and subsequent delivery of metered-dose inhaler (MDI) aerosols into the lung were measured with the actuator alone and with 4 different kinds of auxiliary devices; open-end straight tube, Aerochamber, Nebuhaler, and InspirEase. The total mass of dry aerosol discharged directly from the actuator, from the auxiliary devices, and through the oropharyngeal model was determined by collecting the aerosol on the absolute filter and weighing the filter. Aerosol depositions in the auxiliary devices and in the oropharynx as well as the amount of aerosol delivered past the oropharynx were determined as percentages of the total aerosol mass output from the actuator alone. Six different MDI aerosols, 3 bronchodilators, and 3 corticosteroids were used. With the actuator alone, oropharyngeal deposition ranged from 33 to 71% at an inspiratory flow rate of 0.33 L/s, depending on the type of MDI aerosols. Aerosol delivery into the lung was 29 to 67%. With the auxiliary devices, oropharyngeal deposition markedly decreased to the range below 6% regardless of the type of auxiliary device and aerosol. A major deposition (23 to 72%) occurred in the auxiliary devices except for Nebuhaler in which a much reduced deposition (8 to 18%) occurred. Aerosol delivery into the lung was in the range of 40 to 72% with the open-end tube, 26 to 62% with the Aerochamber, 34 to 60% with InspirEase, and 31 to 92% with Nebuhaler. Although a substantial increase in aerosol delivery (as much as 38%) was found with a large size Nebuhaler, the aerosol delivery with other smaller auxiliary devices used was comparable to those obtained without the auxiliary devices.

Adrenal Cortex Hormones↗

PubMed1987

Oronasal distribution of ventilation during exercise in normal subjects and patients with asthma and rhinitis.

This study was undertaken to determine whether the resistance to nasal airflow and differences in oronasal distribution of ventilation at rest and during exercise alter the pattern of breathing. We observed six normal subjects, six patients with symptomatic allergic rhinitis, and six patients with asymptomatic bronchial asthma (three men and three women in each group), all of whom had normal pulmonary function. At rest, five of the six normal subjects breathed nasally but 11 of the 12 patients breathed with an oronasal distribution. Five normal subjects who breathed nasally at rest breathed with an oronasal distribution of ventilation during exercise, and one normal subject who breathed oronasally at rest had slightly less oral ventilation during exercise. In the patients, the change in oral distribution of ventilation during exercise was variable. Among the three groups, there were no significant differences from the resting oronasal distribution for ventilation during exercise, and all subjects breathed oronasally during exercise. The oronasal distribution of ventilation did not correlate with the level of nasal airflow resistance. Analysis of the timing, volume, and flow components of breathing showed no statistically significant differences among the three groups at rest and exercise. Thus, neither the level of resistance to nasal airflow, even up to moderately high values, nor the nasal distribution of ventilation at rest and with moderate exercise appears to have a major role in the pattern of breathing.

Adult↗

PubMed1987

Phasic flow mechanisms of mucus clearance.

Excessive bronchial secretions within the airways can be transported by two-phase gas-liquid flow with airflow rates encountered during normal tidal breathing. The transport speed of secretions with this mechanism is as effective as the mucus clearance rate in normal subjects. The thickness of bronchial secretions required to effect two-phase gas-liquid flow is about 10% of the airways diameter which is not an unusual situation for patients who have bronchial hypersecretion. Periodic airflow as encountered in normal breathing is more effective than continuous flow in moving secretions in one direction or another. However, to propel the secretions toward the larynx, expiratory airflow velocity should be higher than inspiratory airflow velocity. This pattern can be achieved by imposing a controlled pattern of mechanical ventilation and is also probably the basis for the "huffing manoeuvre" taught by chest physiotherapists to clear airway secretions. Increased elasticity and decreased viscosity of secretions promote higher transport rates by two-phase gas-liquid flow. Conditions for two-phase gas-liquid flow during tidal breathing can be met at the 8th to 9th generation of the airways.

Animals↗

PubMed1986

Criteria for mucus transport in the airways by two-phase gas-liquid flow mechanism.

The critical conditions for mucous layer transport in the respiratory airways by two-phase gas-liquid flow mechanism were investigated by using 0.5- and 1.0-cm-ID tube models. Several test liquids with rheological properties comparable to human sputum were supplied continuously into the vertically positioned tube models in such a way that the liquid could form a uniform layer while traveling upward through the tube with a continuous upward airflow. The critical airflow rate and critical liquid layer thickness required for the upward transport of the liquids were determined. The critical airflow rate was in the Reynolds number (Re) range of 142-1,132 in the 0.5-cm-ID tube model and 708-2,830 in the 1.0-cm-ID tube model depending on the types of liquids tested. In both models, the critical airflow rate was lower with viscoelastic liquids than with viscous oils. The critical liquid layer thickness ranged from 0.2 to 0.5 mm in the 0.5-cm-ID tube model and 0.8 to 1.4 mm in the 1.0-cm-ID tube model at Re of 2,800. These values decreased rapidly with increasing airflow rate. The critical thickness relative to the tube diameter ranged from 3 to 15% of the respective tube diameter and was lower by approximately 30-50% in the 0.5-cm-ID tube model than in the 1.0-cm-ID tube model over the entire Re range tested. The results indicate that the critical conditions for the mucus transport by two-phase gas-liquid flow mechanism are within the range that can be achieved in patients with bronchial hypersecretions during normal breathing.

Biological Transport↗

PubMed1986

Mucus transport in the airways by two-phase gas-liquid flow mechanism: continuous flow model.

Mucus transport speed induced by two-phase gas-liquid interaction was measured in the continuous two-phase annular flow tube models, and factors influencing the transport speed were assessed in conjunction with rheological properties of mucus. The flow model was made with 1.0-cm-ID glass tubes and positioned either vertically or horizontally. During a continuous passage of airflow through the model tube, mucus stimulants were supplied into the tube at a rate of 0.5-2.0 ml/min. The advancing speed of the leading edge of the mucous layer and mean mucous layer thickness were then measured. The transport speed in the vertical tube model ranged from 1.1 to 3.1 cm/min with a mucus feed rate of 0.5 ml/min at airflow rates of 0.33-1.17 l/s and increased with increasing airflow rates but decreased rapidly with increasing viscosity of mucus. The transport speed increased almost proportionally with increasing mucus feed rate. Elasticity of mucus did not affect the transport speed itself. However, more elastic mucus caused lower flow resistance and thereby could be transported with a much reduced work load. The transport speed in the horizontal tube model was 5-60% faster than that in the vertical tube model. The mean mucous layer thickness in the vertical tube model was found to be in the range of 0.5-1.5 mm in the experimental conditions used, and decreased rapidly with increasing airflow rate and decreasing viscosity of mucus. From these data the transport speed could be functionally related to airway diameter, mucous layer thickness, and mucus production rate.

Biological Transport↗

PubMed1986

Effect of InspirEase on the deposition of metered-dose aerosols in the human respiratory tract.

A radiotracer technique has been used to assess the effects of a 700-ml collapsible holding chamber (InspirEase, Key Pharmaceuticals Inc.) on the deposition of metered-dose aerosols in ten patients with obstructive airways disease (mean forced expiratory volume in one second [FEV1], 64.5 percent of predicted). Patterns of deposition obtained by patients' usual techniques with the metered-dose inhaler (MDI) were compared with those by correct MDI technique (actuation coordinated with slow deep inhalation and followed by ten seconds of breath-holding) and with those by InspirEase. Deposition of aerosol was assessed by placing Teflon particles labelled with 99mTc inside placebo canisters, and inhaling maneuvers were monitored by respiratory inductive plethysmography (Respitrace). Nine of the ten patients had imperfect technique with the MDI, the most prevalent errors being rapid inhalation and failure to hold their breath adequately. With patients' usual MDI techniques, 6.5 +/- 1.2 percent (mean +/- SE) of the dose reached the lungs. This was increased to 11.2 +/- 1.3 percent (p less than 0.02) with correct technique and increased further to 14.8 +/- 1.4 percent (p less than 0.05) with InspirEase. Oropharyngeal deposition exceeded 80 percent of the dose for the MDI alone but was only 9.5 +/- 0.9 percent with InspirEase (p less than 0.01); 59.2 +/- 2.1 percent of the dose was retained within InspirEase itself. It is concluded that InspirEase gives whole lung deposition of metered-dose aerosols greater than that from a correctly used MDI, while oropharyngeal deposition is reduced approximately nine times.

Adult↗

PubMed1985

Acute effects of aerosolized metaproterenol on breathing pattern of patients with symptomatic bronchial asthma.

We studied the effect of two sequential puffs of metaproterenol (650 micrograms each puff) delivered with an auxiliary aerosol delivery system on the breathing pattern of patients with symptomatic bronchial asthma who were monitored noninvasively with respiratory inductive plethysmography. Particular attention was directed to respiratory center drive as reflected by mean inspiratory flow and minute ventilation. Both these components were elevated in the eight patients whose mean FEV1.0 was 1.43 L (45% predicted normal). Two puffs of metaproterenol produced a maximal increase over baseline in FEV1.0 of 50 +/- 25% (SD), whereas no change took place in FEV1.0 with placebo administration. This dose of metaproterenol did not alter heart rate nor blood pressure throughout the study period of 2 hours. Neither mean inspiratory flow, minute ventilation, nor any component of the breathing pattern changed with this partial reversal of bronchoconstriction. These results suggest that the neural mechanism accounting for heightened respiratory center drive in patients with symptomatic bronchial asthma does not wholly depend on bronchoconstriction.

Adult↗

PubMed1985

Increased serum copper in primary pulmonary hypertension: a possible pathogenic link?

In conscious sheep, we showed that intravenous infusion of copper sulfate produced a marked increase in pulmonary vascular resistance which was prevented by alpha-adrenergic blockade or catecholamine depletion. Because of these observations, we measured serum copper in 7 patients with primary pulmonary hypertension, and in 6 normal women. The 5 female patients had taken contraceptive and appetite-suppressant medication in the past. The mean serum copper level was significantly higher in patients with pulmonary hypertension, indicating that increased serum copper may be a cause or a marker of this entity.

Adult↗

PubMed1985

Influence of two-phase gas-liquid interaction on aerosol deposition in airways.

Many patients with chronic simple bronchitis, viz., chronic productive cough without major airway obstruction, frequently show enhanced aerosol deposition in the airways. We hypothesized that this phenomenon might relate in part to wave motion of an accumulated layer of mucus caused by dynamic, two-phase gas-liquid interactions. In the present investigation, two-phase gas-liquid interaction was demonstrated in vivo by observing wave motion during tidal breathing of radiopaque-labeled viscous and viscoelastic fluids that had been added to distal tracheas of conscious sheep. Total aerosol deposition in the lung and mean pulmonary resistance (RL) were measured after addition of 4 to 10 ml of viscoelastic or viscous fluids to the distal main bronchi of conscious sheep. Change in aerosol deposition over baseline after fluid addition was compared with change in RL. In 21 experiments, 5 for each of 3 viscoelastic fluids with varying characteristics and 6 for a viscous fluid, aerosol deposition was significantly enhanced in every experiment, irrespective of the type of fluid added. This increase in aerosol deposition ranged from 13 to 66% above baseline. The RL increased in 5 of the 6 experiments with viscous fluid and in 4 of the 15 experiments with viscoelastic fluids. There was less wavelike motion with viscous than with viscoelastic fluids. These results suggest that two-phase gas-liquid interaction in the airways can account for increased aerosol deposition with little alteration in airway resistance.

Aerosols↗

PubMed1985

Size aspects of metered-dose inhaler aerosols.

The aerodynamic size distribution of several bronchodilator and corticosteroid metered-dose inhaler (MDI) aerosols was estimated in both dry and humid (90% RH) air environments with a six-stage cascade impactor. The distribution of aerosol size that penetrated into a simulated lung model were also measured. The size distributions were approximately log-normal and ranged from 2.4 to 5.5 micron in mass median aerodynamic diameter (MMAD) with geometric standard deviation (GSD) of 1.7 to 2.5 in a dry environment. In humid air, MMAD increased from 1 to 26% above the dry air state, but GSD remained unchanged. The size of aerosol delivered by MDI that penetrated into a simulated lung model fell to 2.4 to 2.8 micron in MMAD (GSD, 1.9 to 2.2). In contrast to aerosols produced by MDI, MMAD of an aerosol of cromolyn sodium powder dispersed by a Spinhaler increased rapidly with increasing humidity, 5.6 +/- 0.3 micron in dry air and 10.1 +/- 0.8 micron in 90% RH air. Finally, the factors influencing size of MDI-delivered aerosols, including formulation, canister pressure, physicochemical properties of propellants, and design of the valve and actuator orifices are discussed. Effective delivery of MDI-generated aerosols into the lung is highly dependent on particle dynamics and jet flow, and no single parameter can produce a unique particle size and jet pattern.

Aerosol Propellants↗

PubMed1985

Respiratory drive in nonsmokers and smokers assessed by passive tilt and mouth occlusion pressure. Response to rebreathing carbon dioxide.

The purpose of the present investigation was to assess respiratory center function in smokers using (1) measurement of mouth occlusion pressure during carbon dioxide rebreathing and (2) noninvasive measurement of breathing pattern during passive upright tilt. The breathing patterns of 20 normal nonsmokers and 20 smokers without major obstruction of the airways were monitored noninvasively with respiratory inductive plethysmography for 15 minutes in the supine position and then after 90 degrees head-up passive tilt to the standing position. In nonsmokers, significant increases from supine to standing positions included the following: (1) minute ventilation from 6.22 +/- 1.47 to 7.32 +/- 1.16 L/min (p less than 0.05); (2) tidal volume from 368 +/- 93 to 462 +/- 108 ml (p less than 0.01); and (3) mean inspiratory flow from 263 +/- 61 to 320 +/- 43 ml/sec (p less than 0.01). Responses of smokers to tilt were variable; 14 showed changes similar to nonsmokers, but six showed no increase of ventilation and respiratory drive upon tilting. The latter also showed blunted response to rebreathing carbon dioxide in the supine position as estimated by plotting mouth occlusion pressures against end-tidal carbon dioxide tension. These data suggest that disturbances of respiratory center control are common in smokers without major obstruction of the airways.

Adult↗

PubMed1985

Periodic breathing triggered by hypoxia in normal awake adults. Modification by naloxone.

Breathing patterns in six normal awake subjects were monitored noninvasively during progressive hypoxia accomplished with the administration of nitrogen at 2, 4, 6, and 8 L/min by nasal cannula. The lowest value of arterial oxygen saturation (SaO2) of 88 +/- 4 percent (mean +/- SD) was achieved with nitrogen at 8 L/min. At baseline, tidal volume (VT) and frequency were fairly regular; with nitrogen at 2 and 4 L/min, some subjects showed minor fluctuations of VT. At 6 and 8 L/min, periodic breathing with marked oscillations of VT, apneas, hypopneas, and intermittent large tidal breaths were consistently observed. Inspired oxygen concentration fluctuated because of the variations of tidal breaths provoked when periodic breathing took place and enhanced fluctuation in SaO2. A randomized, double-blind crossover design was used to assess the effect of pretreatment with naloxone on this periodicity. In contrast to the irregular breathing pattern observed with pretreatment with placebo, the breathing pattern after pretreatment with naloxone was regular during nasal administration of nitrogen except at 8 L/min, when minor fluctuations in VT with occasional hypopneas and large tidal breaths occurred. On another day, irregular and periodic breathing with apneas or hypopneas (or both) produced by nasal nitrogen at 8 L/min was eliminated or blunted by short-term intravenous administration of naloxone. On another day, electroencephalographic monitoring corroborated visual observations made in the previous studies that the hypoxic subjects were awake during the breathing alterations. Thus, awake adults develop irregular and periodic breathing during induction of mild hypoxia produced by nasal administration of nitrogen. The irregularity in breathing appears to be mediated through release of endorphins, since the effect is blunted or eliminated by pretreatment or short-term treatment with naloxone.

Adult↗

PubMed1985

Recent advances in the management of obstructive airways disease. Auxiliary MDI aerosol delivery systems.

Aerosol delivered through metered-dose inhalers (MDI) offers a potentially convenient way to deliver bronchodilator agents and corticosteroids to the lungs of patients with asthma and COPD. Unfortunately, most patients are unable to coordinate satisfactorily their actuation with inhalation, a problem overcome by using auxiliary MDI aerosol delivery systems. Left to their own judgment, patients often inhale the aerosol with a high inspiratory flow rather than slowly to produce optimal aerosol deposition within the airways. This problem has been corrected by one of the auxiliary MDI aerosol delivery systems (InspirEase) through auditory, visual, and tactile feedback mechanisms. MDI devices release aerosol at a high jet velocity in large particle sizes, depositing most of the aerosol in the oropharynx which can lead to potential systemic absorption of adrenergic agonists with CNS and cardiovascular side effects, oral thrush, and suppression of adrenocortical activity. All the auxiliary MDI aerosol systems promote delivery of small aerosol particles and markedly diminish oropharyngeal impaction. Of all the systems, only InspirEase provides volume and flow feedback controls to ensure an optimal inhalation maneuver. Auxiliary MDI aerosol systems should always be used for aerosolized corticosteroid administration because they minimize oropharyngeal deposition and improve aerosol delivery efficiency.

Adrenal Cortex Hormones↗

PubMed1984

Measurement of systolic time intervals during exercise using inductive plethysmography.

Measurement of systolic time intervals (STI) provides a noninvasive assessment of cardiac function in resting subjects. However, large motion artifacts often limit their application during exercise. To improve such measurements, we employed a new lightweight carotid arterial pulse transducer and minimized the artifacts by computerized signal averaging. The carotid pulse was recorded with an inductive plethysmographic transducer band (CIP) wrapped around the neck. STI derived from these measurements were compared to standard measurements from a funnel-shaped cup attached to the neck and connected to a pressure transducer (CUP) in 12 normal subjects at rest and with graded bicycle ergometry. To compare the techniques, CIP and CUP signals, together with the EKG and phonocardiogram, were connected separately to two microcomputer systems. The systems were triggered from the EKG and averaged the signals over 16 or 32 heart beats. Semi-automatic analysis of the averaged signals provided estimates of left ventricular ejection time (LVET), pre-ejection period (PEP) and electromechanical systole (QS2). Motion artifact levels of the unprocessed signals were similar with both CIP and CUP methods but were greatly reduced by signal averaging. All LVET values using CIP fell within 10% of CUP values. 85% of PEP values using CIP were within 20% of CUP values. Increasing exercise loads produced appropriate decreases in QS2, LVET, PEP and PEP/LVET consistent with increased myocardial contractility. The CIP proved comfortable to wear and did not require critical positioning as did the CUP. Measurement of STI complements exercise pulmonary testing with useful information of cardiac function.

Adult↗

PubMed1984

Breathing pattern during induced bronchoconstriction.

The breathing patterns of normal subjects monitored with respiratory inductive plethysmography were investigated after mild increases in respiratory resistance provoked by aerosolized methacholine during natural breathing and while breathing on a mouthpiece to a pneumotachograph. First, during natural breathing, comparisons of inspiratory ventilation (VI), tidal volume (VT), frequency (f), inspiratory time (TI), fractional inspiratory time (TI/TT), and mean inspiratory flow (VT/TI) were made before and after aerosolized buffered saline and methacholine in a dose that reduced specific airway conductance (sGaw) by 35% (PD35). There was a significant increase in VT/TI and VI after methacholine, whereas VT, f, TI, and TI/TT were not consistently modified by saline or methacholine. Pretreatment with bronchodilators prevented changes in respiratory resistance (Rrs) as well as in breathing pattern after PD35 methacholine. On another day, Rrs, end-expiratory lung volume level, and breathing pattern during natural breathing were monitored after administration of predetermined doses of methacholine that reduced sGaw by 25% (PD25), PD35, and 55% (PD55). Increases in VT/TI and end-expiratory lung volume level paralleled the increases in Rrs after each dose of methacholine but not with saline control. VI increased along with Rrs at the PD25 and PD35 doses but plateaued at the PD55 dose while Rrs continued to rise. There were no changes in breathing pattern in subjects who breathed on a mouthpiece to a pneumotachograph after PD55 methacholine. Thus alterations of the breathing pattern due to mild-to-moderate degrees of bronchoconstriction are characterized by progressive rises of mean inspiratory flow (an index of respiratory center drive) and end-expiratory lung volume level (a measure of pulmonary hyperinflation), but VI plateaus at the more severe degree of bronchoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1984

Accuracy of respiratory inductive plethysmograph over wide range of rib cage and abdominal compartmental contributions to tidal volume in normal subjects and in patients with chronic obstructive pulmonary disease.

We assessed the accuracy of the respiratory inductive plethysmograph in the supine position to spirometry by the two-body position, least squares calibration and single-body position, isovolume calibration procedures. The comparison was carried out simultaneously in normal subjects breathing naturally and with voluntarily controlled abdominal or thoracic breathing, and in patients with COPD breathing naturally and with voluntarily controlled abdominal breathing patterns. In both groups, there was no significant difference in estimation of tidal volume between the 2 calibration procedures for the various breathing patterns. There was greater deviation from spirometric tidal volume values for both calibration methods in patients with COPD during abdominal than during natural breathing. In the normal subjects, agreement between the rib cage and abdominal partitioning of tidal volume for both calibration methods was good, but in the patients with COPD there was greater variability. In normal subjects, over a wide range of rib cage and abdominal compartmental contributions to tidal volume, either calibration procedure appears satisfactory. For patients with COPD, if large changes occur in the distribution of rib cage and abdominal contributions to tidal volume, then validation of respiratory inductive plethysmography to spirometry must be rechecked.

Abdomen↗

PubMed1984

Effects of abdominal and thoracic breathing on breathing pattern components in normal subjects and in patients with chronic obstructive pulmonary disease.

The purpose of this study was to assess the effect of voluntarily controlled breathing maneuvers on breathing pattern components measured noninvasively with the respiratory inductive plethysmograph. In normal subjects, these maneuvers included predominantly thoracic and abdominal patterns with and without visual reinforcement from video-displayed plots of rib cage versus abdominal loops. In patients with chronic obstructive pulmonary disease (COPD), only predominantly abdominal breathing without and with visual feedback was employed; the latter produced greater abdominal contribution to tidal volume. Voluntarily controlled breathing patterns led to increased minute ventilation (VI) in normal subjects because of variable changes of frequency and tidal volume. This increase in ventilation was achieved despite increased asynchronous and paradoxic motion between rib cage and abdominal excursions that would add to the work of breathing. Patients with COPD had heightened baseline respiratory center drive when compared with that in normal subjects, as evidenced by elevation of VI and mean respiratory flow (VT/TI). In contrast to normal subjects, abdominal breathing produced no change in VI and VT/TI for the group as a whole, but 6 of the 9 patients with COPD had decreases compared with natural breathing. This diminution of respiratory drive in some patients with COPD during voluntary abdominal breathing might relate to limitation of ventilatory response by the increased work of breathing caused by pulmonary hyperinflation, elevated airway resistance, and increased asynchronous and paradoxic motion of the rib cage to the abdominal excursions, and/or the mental activity required to perform the breathing maneuver might be inhibitory to respiratory drive.

Abdomen↗

PubMed1984

Assessment of asynchronous and paradoxic motion between rib cage and abdomen in normal subjects and in patients with chronic obstructive pulmonary disease.

Both scalar tracings and XY plots of rib cage (RC) and abdominal (AB) excursions were analyzed to detect asynchronous and/or paradoxic motion of one compartment with respect to the other in an effort to distinguish differences between normal subjects and patients with chronic obstructive pulmonary disease (COPD). An inspiratory asynchrony index (IAI) was obtained by connecting a straight line from beginning inspiration to end inspiration of the RC-AB loop, and dividing the area enclosed by the inspiratory portion by the tidal volume. In like manner, an expiratory asynchrony index (EAI) was computed. Values of IAI and EAI in the supine posture were greater in patients with COPD than in normal subjects, and such differences were consistently demonstrated during natural and voluntarily controlled abdominal breathing. Paradoxic motion as percent of volume or time period of inspiratory and expiratory compartmental excursions was indicated when RC or AB compartments moved in an opposite direction to the sum of the two. During natural breathing, paradoxic motion was almost absent in normal subjects and variably present in patients with COPD. Voluntarily controlled breathing patterns produced increased IAI, EAI, and paradoxic motion. Passive tilting from supine to the upright posture did not affect indexes in normal subjects but reduced asynchronous and paradoxic motion of the RC in patients with COPD. Other indexes of loop analysis, such as phase angle and maximal compartment amplitude/tidal volume, were not as consistent in distinguishing between normal subjects and patients with COPD during natural and voluntarily controlled breathing patterns.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗