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Biomedical subjects

T S Chadha

Publications and source records attributed to T S Chadha.

13 recordsLinked to original sources
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↗
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↗
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

Mechanism of bronchoconstrictive effects of aerosolized buffered saline in asthmatics.

Bronchoconstriction, measured by spirometry and body plethysmography, has been reported with deep breaths of air and of aerosolized buffered saline (ABS) (0.5% sodium chloride and phosphate buffer), in some stable asthmatics. To investigate the mechanisms of this phenomenon, we measured airway resistance (Raw) and functional residual capacity (FRC) in ten asthmatics after deep breaths of ABS, tidal breaths of ABS, tidal breaths of unbuffered normal saline (0.9% sodium chloride) and tidal breaths of 0.5% sodium chloride (ABS without phosphate) on different days. Raw and FRC increased with deep breaths and tidal breaths of ABS in all asthmatics, but not with tidal breaths of normal saline and unbuffered 0.5% sodium chloride. Thus the phosphate buffer rather than the hypoosmolarity of aerosolized buffered saline causes bronchoconstriction in asthmatics.

Adult↗
PubMed1983

Noninvasive treatment of pneumothorax with oxygen inhalation.

The treatment for pneumothorax varies from invasive chest tube drainage to conservative management with bed rest. Based on the behavior of gases in closed body cavities, the inhalation of supplemental oxygen hastens absorption of the pneumothorax. To evaluate oxygen as a therapeutic agent, we treated 8 patients with pneumothoraces of various degrees with a high concentration of inspired oxygen delivered by a partial rebreathing mask. Periodic roentgenograms were used to measure the change in size of pneumothorax in order to assess the rate of resolution. 6 patients with pneumothoraces of less than 30% showed a mean resolution rate of 4.2% per day with reduction to one-third original size in the first 72 h. This was more than three times the rate of resolution (1.25% per day) previously reported with breathing room air alone. In 2 patients who initially received a lower concentration of inspired oxygen via nasal cannula, the rate of absorption increased after placing them on a partial rebreathing mask. 2 patients with four episodes of pneumothoraces greater than 30% did not benefit from this form of therapy and eventually needed chest tube drainage. We conclude that the administration of high concentrations of inspired oxygen is an effective method to enhance the rate of resolution of pneumothoraces, particularly when smaller than 30%, thereby reducing morbidity and duration of hospitalization and avoiding invasive drainage procedures.

Absorption↗
PubMed1983

Breathing patterns. 1. Normal subjects.

Ventilatory monitoring devices that require mouthpiece breathing produce a rise in tidal volume (VT), a fall in frequency (f) and alterations in periodicity and variability of breathing components. Together with the introduction of the respiratory inductive plethysmograph, a reliable noninvasive monitoring device of ventilation, major advances have taken place in understanding the significance of the components of the breathing pattern. We measured the breathing pattern of normal subjects utilizing respiratory inductive plethysmography and continuously processed these data with a microprocessor system. The mean values of the breathing pattern components in normal subjects were not affected by age, but the rhythmicity was more irregular in the elderly. The values of breathing pattern components obtained noninvasively by respiratory inductive plethysmography in normal subjects are fairly predictable in limits similar to other tests of pulmonary function.

Adult↗
PubMed1983

Breathing patterns. 2. Diseased subjects.

We measured the breathing pattern of normal subjects, asymptomatic smokers, asymptomatic and symptomatic asthmatic patients, and patients with chronic obstructive pulmonary disease, restrictive lung disease, primary pulmonary hypertension and anxiety state utilizing respiratory inductive plethysmography. Respiratory rate was increased above the normal in smokers and in patients with COPD, restrictive lung disease and pulmonary hypertension, but remained normal in asthmatic patients. Inspiratory times (T1) of one second or less often occurred in patients with COPD, restrictive lung disease, and pulmonary hypertension. Smokers and patients with symptomatic asthma, COPD, restrictive lung disease and pulmonary hypertension showed heightened respiratory center drive as reflected by elevated mean inspiratory flow (VT/TI). Fractional inspiratory time was reduced to a variable extent in smokers, symptomatic asthmatic patients and patients with COPD, and was a weak indicator of airways obstruction. Patients with COPD often had major fluctuations of expiratory timing, periodic fluctuations of end-expiratory level, and asynchrony between rib cage and abdominal movements. Chronic anxiety was characterized by frequent sighs; episodic rapid rates alternating with apneas were less common. We conclude that analysis of breathing patterns provides diagnostic discrimination among normal subjects and disease states.

Adult↗
PubMed1983

Effects of partial anti-G suit inflation on thoracic volume and breathing pattern.

The purpose of this study was to determine the changes in thoracic volume and pattern of breathing during partial anti-G suit (PAGS) inflation by respiratory inductive plethysmography (RIP). Nine normal subjects donned the PAGS, with bladders over legs and thighs, and rested for about 10 min in 60 degrees head-up tilt position. The subjects breathed with closed glottis at functional residual capacity while PAGS was suddenly inflated to 140 mmHg using a calves to thighs sequence. The increase in thoracic volume, as measured from deflection of RIP baseline was 252 ml (S.D. 43 ml), which reflected displacement of blood from the lower extremities into the thorax. On resuming normal breathing, thoracic volume returned to baseline level. Breathing pattern was then monitored for a 15 min baseline period, PAGS was inflated, expiratory reserve volume (ERV) was measured by spirometry, and breathing pattern was monitored another 15 min. ERV decreased 227 ml (+/- 60) after PAGS inflation, which did not differ from the change in thoracic volume expected from displacement of blood into the thorax. Breathing pattern was monitored for another 15 min after PAGS was deflated. No changes took place in minute ventilation, tidal volume, frequency, inspiratory time, fractional inspiratory time, and mean inspiratory flow from deflation to PAGS inflation. Thus, 1) increase in thoracic volume produced by displacement of blood from the calves and thighs is balanced by a decrease in gas volume and, 2) no changes in breathing pattern occur after partial anti-G suit inflation, probably because the pulmonary blood vessels and heart are sufficiently distensible to accept a 250 ml volume increment without leakage of fluid into pulmonary tissues.

Adult↗
PubMed1982

Validation of respiratory inductive plethysmography using different calibration procedures.

We devised a new calibration procedure [least squares method (LSQ)] for respiratory inductive plethysmography (RIP) and compared it with our previously reported simultaneous equation method (SEQ) of analyzing data in 2 body positions and with the method of Stagg and associates using the analysis of individual breaths in a single body position. The values from RIP were compared with simultaneous spirometry (SP) in 20 normal subjects placed in the standing (STD), supine (SUP), sitting, prone, semi-recumbent, right lateral decubitus, and left lateral decubitus postures. The LSQ gave the most accurate results followed closely by SEQ. In addition, LSQ was compared with the isovolume angle maneuver (ISV) calibration procedure in supine (ISV-SUP) and standing (ISV-STD) postures. Each of the 10 normal subjects breathed at tidal volumes of 250, 750, and 1,250 ml in the SUP and STD postures. Of the values obtained by the LSQ method, 93% were within +/- 10% of SP in SUP and STD positions. Without a change in the posture in which the calibration was made, 83% of values with ISV-SUP and 90% of values with ISV-STD were within +/- 10% of SP. When body position was changed, 65% of the values obtained with ISV-SUP and 38% of the values obtained with ISV-STD were within +/- 10% of SP. With the LSQ, 45% of isovolume angles in SUP and STD position were within 45 +/- 3 degrees; 40% of isovolume angles with ISV-SUP and 60% with ISV-STD were within 45 +/- 3 degrees when body position was changed from position calibrated. In estimating fractional contribution of rib cage and abdominal compartments. LSQ was comparable to ISV in the standing posture but generally gave lesser values for the rib cage contribution in the supine posture than ISV. The optimal calibration procedure for respiratory inductive plethysmography in terms of accuracy and ease of subject performance is the least squares calibration procedure.

Calibration↗
PubMedDate not supplied

Effects of ultrasonically nebulized distilled water on respiratory resistance and breathing pattern in normals and asthmatics.

The purpose of this study was to analyze changes in respiratory resistance (Rrs) and breathing pattern in normal and asthmatic subjects after exposure to ultrasonically nebulized distilled water (UNDW). After measurement of baseline Rrs and breathing pattern, ten normals inhaled UNDW for 30, 60, 120, 240 and 480 s administered at 15 min intervals. After the 480 s exposure, subjects inhaled two puffs of metaproterenol. Rrs was measured immediately before and after each exposure to UNDW and after metaproterenol while breathing pattern was continuously monitored. Ten asthmatics were exposed to UNDW and metaproterenol in a similar time sequence, but the durations of exposure to UNDW were 15, 30, 60, 120 and 240 s. Mean (+/- SD) and frequency histograms of minute ventilation (VE), tidal volume (VT), frequency, inspiratory time, fractional inspiratory time, mean inspiratory flow (VT/TI) and end-expiratory level at baseline were compared to values after each exposure to UNDW and after metaproterenol. All subjects experienced laryngeal irritation or cough during the exposure. In normals, there were no changes in Rrs or any of the components of breathing pattern. In asthmatics, 15 and 30 s exposures produced no changes in Rrs or breathing pattern. With subsequent longer exposures, mean Rrs showed a stepwise significant increase, along with parallel increases of VT/TI and end-expiratory level. VE increased after 60 and 120 s exposure, but reached a plateau after 240 s exposure despite continued increase in Rrs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗