SEARCH · PubMed Health

Results for “Inspiratory Capacity”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1975

Effects of expiratory threshold loading during steady-state exercise.

Increases in functional residual capacity (FRC) decrease inspiratory muscle efficiency; the present experiments were designed to determine the effect of FRC change on the ventilatory response to exercise. Six well-trained adults were exposed to expiratory threshold loads (ETL) ranging from 5 to 40 cmH2O during steady-state exercise on a bicycle ergometer at 40-95% VO2max. Inspiratory capacity (IC) was measured and changes of IC interpreted as changes of FRC. ETL did not consistently limit exercise performance. At heavy work (greater than 92% VO2max) minute ventilation decreased with increasing ETL; at moderate work (less than 58% VO2max) it did not. Decreases in ventilation were due to decreases in respiratory frequency with prolongation of the duration of expiration being the most consistent change in breathing pattern. At moderate work levels, FRC increased with ETL; at maximum work it did not. Changes in FRC were dictated by constancy of tidal volume and a fixed maximum end-inspiratory volume of 80-90% of the inspiratory capacity. When tidal volume was such that end-inspiratory volume was less than this value, FRC increased with ETL. Mouth pressure measured during the first 0-1 s of inspiratory effort against an occluded airway (P0-1) was increased by ETL equals 30 cmH2O, in spite of the fact that ventilation was decreased. We concluded that changes in FRC due to ETL had no effect on the ventilatory response to exercise and that changes in P0-1 induced by ETL did not reflect changes of inspiratory drive so much as changes of the pattern of inspiration.

Adult↗

PubMed1979

Pulmonary reaction to upper mantle radiation therapy for Hodgkin's disease.

To study the effects of upper mantle radiation therapy on pulmonary function, forced expiratory volume in one second (FEV1), vital capacity (VC), inspiratory capacity (IC), diffusing capacity for CO (DLCO) and diffusion per unit of alveolar volume (DL/VA were determined in 28 patients with Hodgkin's disease, stages 1--3, before therapy and at regular intervals thereafter. Within the first year of follow-up there were significant declines in DLCO, VC, and IC, whereas there were no significant changes in FEV1 or DL/VA. DLCO showed the greatest decline in the largest number of subjects (22/28). Eleven of the 22 had 20 to 60 percent decline of DLCO from baseline. The maximum mean decline in DLCO was -12.7 +/- 3 percent at the 87th +/- 3 days from initiation of therapy postradiation sustained through the 150th day and improving to pretreatment value (+/- 5 percent) by the 8th to 12th month. The changes in DLCO seemed to be independent of the radiation dose ranges evaluated, clinically apparent intrathoracic lymphoma, postradiation radiographic abnormalities and respiratory symptoms. We concluded that impairment in diffusing capacity and loss of vital capacity will develop in most patients receiving upper mantle radiation therapy, indicating that pulmonary reaction occurs despite lung shielding. The functional losses were prolonged and occasionally severe, but were transient and subclinical in most but not all cases. A case of fatal radiation pneumonitis affecting the lung beyond the field of irradiation is reported.

Adolescent↗

PubMed1975

Evaluation of bronchial drainage in patients with cystic fibrosis.

Examined in this study are the results of six tests of pulmonary function immediately preceding and following bronchial drainage in twenty-six patients with cystic fibrosis. Highly significant increases averaging 5.67, 4.13, 13.47, and 6.98 percent occurred in peak expiratory flow rate, forced vital capacity, expiratory reserve volume, and inspiratory capacity respectively. Significant increases in peak expiratory flow rate, forced vital capacity, and inspiratory capacity were observed in a subgroup of six of the above patients who had evidence of bronchospasm. The authors conclude that bronchial drainage will produce significant increases in routine pulmonary function values. The results suggest that this treatment is most effective in clearing the larger, more proximal, airways and is of benefit even in the presence of clinical bronchospasm.

Adolescent↗

PubMed1992

Breathing pattern adjustments during the first year following cervical spinal cord injury.

The alterations in lung function and breathing pattern were examined in 6 quadriplegics at 3, 6 and greater than 12 months post injury, and were compared to 6 able bodied controls. Subjects were studied in both the seated and supine positions. Functional residual capacity (FRC), forced vital capacity (FVC), inspiratory capacity (IC), and maximum mouth pressure (Pimax) at FRC were measured. Total lung capacity (TLC) and residual volume (RV) were calculated. Resting breathing pattern was assessed for 20 minutes from a spirogram derived from summed rib cage and abdominal strain gauge signals. At 3 months in quadriplegics, TLC was reduced (p less than 0.05), RV increased (p less than 0.01) and FRC was normal in sitting; in supine, only TLC was reduced (p less than 0.05); Pimax was decreased (p less than 0.01) in both positions in quadriplegics at 3 months, but increased over the first year in the seated position (p less than 0.01). There were no alterations in breathing pattern at any time interval in quadriplegics in supine. In contrast, at 3 months post injury in sitting, expiratory time (Te) was shortened (p less than 0.05), tidal volume (Vt) was decreased, and heart rate elevated as compared to controls (p less than 0.05). Inspiratory time (Ti) was not significantly shortened at 3 months in quadriplegics, but a lengthening of Ti occurred between 3 and 6 months (p less than 0.025) resulting in increased Vt, and heart rate decreased to normal. Vt/Ti was reduced, and did not alter with time. The lengthening of Ti/Ttot observed in supine in control subjects (p less than 0.025), was not observed in quadriplegics. Quadriplegics sighed as frequently in supine as did controls at all stages post injury, whereas they decreased sighing frequency in sitting at 3 and 6 months post injury (p less than 0.05). The improvement in resting breathing pattern observed in quadriplegics in sitting with time, may be due to increased accessory muscle function, improved chest wall stability and thoracoabdominal coupling, or a combination of these factors. It is also possible that the alterations in breathing pattern were a response to cardiovascular adjustments occurring in the same time frame. Quadriplegics retain the sigh reflex, but do not take as many big breaths in sitting as they do in supine, probably due to the increased work of breathing in the seated posture.

Adult↗

PubMedDate not supplied

Human exposure to sulfur dioxide and ozone: absence of a synergistic effect.

Studies of the human health effects of exposure to a combination of ozone and sulfur dioxide have produced somewhat conflicting results; the possibility of a synergistic enhancement of toxicity when the two gases are present simultaneously remains equivocal. We evaluated the effects of 0.40 ppm sulfur dioxide, 0.40 ppm ozone, and the combination of these two under one environmental condition (25 degrees C and 45% relative humidity). Subjects alternately walked and rested during a 2-hr exposure. Subjects exposed to filtered air or to 0.40 ppm sulfur dioxide showed no significant changes in pulmonary function. When exposed to either ozone or ozone plus sulfur dioxide, significant decreases in maximum expiratory flow, forced vital capacity, and inspiratory capacity were observed. There were no significant differences in response between ozone alone and ozone plus sulfur dioxide exposures, thus, in our subjects on synergistic effects were discernible.

Adolescent↗

PubMed1991

Responses of baboons to prolonged hyperoxia: physiology and qualitative pathology.

Cardiopulmonary responses to prolonged hyperoxia and their relationships to the development of lung pathology have not been fully characterized in primates. In this study, circulatory hemodynamics and pulmonary function, vascular permeability, and leukocyte sequestration were measured in male baboons after 100% O2 exposure and related to ultrastructural changes of lung injury by electron microscopy. Three groups of animals were exposed to 100% O2 in an exposure cage for 40, 66, and 80 h, respectively. A fourth group of animals was exposed in a cage for 80 h and then anesthetized and ventilated with 100% O2 for additional time. These animals were exposed for a total duration of 110 h or until death from the injury. Physiological responses to hyperoxia were characterized by decreases in total lung capacity and inspiratory capacity at 80 and 110 h. A significant increase in pulmonary leukocyte accumulation was noted by 80 h. Extravascular lung water and permeability surface-area product increased at 80 and 110 h. Cardiac output and stroke volume also decreased, and systemic vascular resistance increased after 80 and 110 h of hyperoxia. Histopathological changes were present in the lungs of all but the 40-h exposure group. Animals exposed for 66 h showed endothelial injury and neutrophil accumulation. By 80 h, animals showed endothelial cell destruction, interstitial edema, and type I cell injury. At 110 h, animals showed substantial destruction of endothelial and type I epithelial cells, exposure of alveolar basement membrane, congestion of capillaries, and substantial interstitial edema. The data indicate that histological changes by electron microscopy precede physiological responses to hyperoxic pulmonary injury in baboons by as much as 14 h and that the physiological responses to early hyperoxic injury are relatively insensitive to the pathological injury.

Animals↗

PubMed1979

Pulmonary function in quadriplegia: effects of a corset.

Fifteen quadriplegic patients underwent multiple pulmonary function studies performed in 2 positions, sitting and supine, and in both positions under 2 circumstances, wearing and not wearing a corset. Analysis of variance showed that 3 volumes were significantly improved (p less than 0.05) supine, especially without the corset: vital capacity (C), inspiratory capacity (IC) and tidal volume (Vt). Although most pulmonary function tests were improved when the patients were supine the trends when sitting were for improvement when wearing a corset. Most of these patients were studied at least 1 year postinjury and results are not substantially different from those 6 months postinjury. Corsets do not have an untoward effect on pulmonary function tests.

Adult↗

PubMed1992

Effect of fatigue on maximal inspiratory pressure-flow capacity.

The inspiratory muscles can be fatigued by repetitive contractions characterized by high force (inspiratory resistive loads) or high velocities of shortening (hyperpnea). The effects of fatigue induced by inspiratory resistive loaded breathing (pressure tasks) or by eucapnic hyperpnea (flow tasks) on maximal inspiratory pressure-flow capacity and rib cage and diaphragm strength were examined in five healthy adult subjects. Tasks consisted of sustaining an assigned breathing frequency, duty cycle, and either a "pressure-time product" of esophageal pressure (for the pressure tasks) or peak inspiratory flow rate (for the flow tasks). Esophageal pressure was measured during maximal inspiratory efforts against a closed glottis (Pesmax), maximal transdiaphragmatic pressure was measured during open-glottis expulsive maneuvers (Pdimax), and maximal inspiratory flow (VImax) was measured during maximal inspiratory efforts with no added external resistance before and after fatiguing pressure and flow tasks. The reduction in Pesmax) with pressure fatigue (-25 +/- 7%) was significantly greater than the change in Pesmax with flow fatigue (-8 +/- 8%, P less than 0.01). In contrast, the reductions in Pdimax (-11 +/- 8%) and VImax (-16 +/- 3%) with flow fatigue were greater than the changes in Pdimax (-0.6 +/- 4%, P less than 0.05) or VImax (-3 +/- 4%, P less than 0.05) with pressure fatigue. We conclude that respiratory muscle performance is dependent not only on the presence of fatigue but whether fatigue was induced by pressure tasks or flow tasks. The specific impairment of Pesmax and not of Pdimax or flow with pressure fatigue may reflect selective fatigue of the rib cage muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗

PubMed1991

Decrease in functional residual capacity during inspiratory loading and the sensation of dyspnea.

The purposes of the present study were to determine the changes in functional residual capacity (FRC) during inspiratory loading and to examine their mechanisms. We studied seven normal subjects seated in a body plethysmograph. In both graded inspiratory elastic (35, 48, and 68 cmH2O/l) and resistive (21, 86, and 192 cmH2O.l-1.s) loading, FRC invariably decreased from control FRC and phasic expiratory activity increased. The reduction in FRC was greater with greater loads. A single inspiratory effort against an inspiratory occlusion at three different target mouth pressures (-25, -50, and -75 cmH2O) and durations (1, 2, and 5 s) also resulted in a decrease in FRC with an increase in expiratory electromyogram activity in the following expiration. The decrease in FRC was greater with greater target pressure and duration. This decrease in FRC is qualitatively similar to that during inspiratory loaded breathing, and we suspect that the same mechanisms are at work. Because neither vagal nor chemoreceptor reflex can account for these responses, we suspect conscious awareness of breathing or behavioral control to be responsible. In an additional study, the sensation of discomfort of breathing during elastic loading decreased with a decrease in FRC. These results suggest that the reduced FRC may be due to behavioral control of breathing to reduce the sensation of dyspnea during inspiratory loading.

Adult↗

PubMed1979

Rib cage deformation during static inspiratory efforts.

Patterns of rib cage (RC) deformation were studied in six normal subjects during moderate static inspiratory efforts such that esophageal pressure (Pes) as an index of transthoracic pressure fell to between -30 and -60 cmH2O during each maneuver. At lung volumes below 50% inspiratory capacity (IC), static inspiratory efforts deformed RC to a more elliptical shape; RC lateral diameter became smaller and RC lateral diameter became larger. However, at high lung volumes (greater than 50% IC) the opposite change in RC dimensions occurred despite similar changes in Pes, i.e., the RC became more circular. These differences in RC deformation did not appear to be a possive consequence of increased lung volume because the RC could be voluntarily deformed to a more circular shape at low lung volume when a) subjects performed static inspiratory efforts mainly with their intercostal and accessory muscles rather than their diaphragm as judged by a smaller change in transdiaphragmatic pressure for the same Pes; or b) subjects statically contracted their diaphragm with it held in a relatively flattened configuration as assessed by a large abdominal AP dimension. We suggest that deformation of the RC during static inspiratory efforts is not as predictable as has previously been suggested but depends on the pattern of contraction and configuration of the respiratory muscles.

Adult↗

PubMed1978

Effect of curare on maximum static PV relationships of the respiratory system.

The effect of respiratory muscle weakness on the maximum static pressure-volume (PV) characteristics of the respiratory system was studied in four healthy males infused slowly with d-tubocurarine (dtc). Inspiratory capacity (IC), expiratory reserve volume (ERV), maximum static inspiratory and expiratory mouth pressures at four lung volumes, and handgrip were measured during induction of, and recovery from muscle weakness. The maximum effect of dtc varied among the muscle groups tested; peripheral muscles were most severely affected, expiratory muscles moderately, and inspiratory muscles least affected. At each level of weakness studied, decreases of IC and ERV were proportional to decreases of maximum static mouth pressures. Vital capacity, measured at each level of weakness was much less than values predicted from the static mechanical properties of the respiratory system. Our findings suggest that the marked change in the extremes of lung volume during submaximal neuromuscular blockade (SMNB) is due, in part, to unequal distribution of muscle weakness, reflected by decreased ability to change ribcage dimensions even at modest levels of SMNB.

Abdomen↗

PubMed1979

The pattern of breathing in patients with chronic airflow obstruction.

1. The pattern of breathing in 12 patients with severe irreversible airflow obstruction has been studied during ventilatory stimulation by rebreathing CO2. Mean maximum tidal volume response was only 1.23 +/- 0.30 litres (mean +/- SD); this represented 65% of mean measured vital capacity and 82% of mean measured inspiratory capacity. During the course of rebreathing mean total breath duration was reduced from 3.48 +/- 0.93 to 2.44 +/- 0.48 s. 2. End-expiratory thoracic gas volume (FRC) was elevated at rest in all subjects and increased significantly by a further 0.50 +/- 1.90 litres during ventilatory stimulation in 10 of the 12 subjects. The maximum increase in FRC was proportional to the degree of airflow obstruction afforded by the airways in each subject. 3. It is suggested that the increase in FRC during ventilatory stimulation is responsible for the diminished tidal volume response and is an important determinant of breathing pattern and symptomatology in patients with airflow obstruction.

Adult↗

PubMed1975

The effect of tubocurarine on indirectly elicited train-of-four muscle response and respiratory measurements in humans.

The effect of tubocurarine on the respiratory function of conscious, non-medicated volunteers was correlated with the degree of neuromuscular blockade measured with the train-of-four technique (the evoked response of the adductor pollicis brevis muscle to trains of four supramaximal ulnar nerve stimuli at 2 Hz, repeated once every 10 sec). Respiratory frequency, tidal volume, vital capacity, inspiratory force and peak expiratory flow rate were measured, (a) before administration of tubocurarine, (b) when the ratio of the amplitude of the fourth response to the amplitude of the first response of the train-of-four reached 60%, and (c) during recovery of the ratio until the control (100%) value was reached. Respiratory frequency, tidal volume and peak expiratory flow rate were not altered. Vital capacity and inspiratory force were both reduced significantly at the 60% level and the former also at the 70% level when compared with the control. The magnitude of change in all variables is of minor clinical importance, however, since the lowest measured values are well above acceptable minimum limits required for adequate respiratory function.

Dose-Response Relationship, Drug↗

PubMed1976

Relationships between eupnoeic pattern of breathing and ventilatory control in man: I. Response to airways occlusion during active lung inflation.

The apnoeic response following interruption of the air flow at different levels of the inspiratory capacity (deltaVL) was studied in conscious children and adults. Changes in mouth pressure were used to measured the duration of the apnoe. The total duration of the interrupted breath (T1) was compared to mean value of the ventilatory period of the five preceding breaths (T0). A monoexponential regression could be fitted to the relationship between T1/T0 ratio and change in lung volume (deltaVL) measured at the onset of interruption: T1/T0=k-exp (S-deltaVL), S begin the sensitivity of the response to lung inflation. When T1/T0=1, the intrathoracic lung volume was called threshold volume (VTh.L.). The parameters S and VTh.L. were used for characterization of the individual importance of the Breuer-Hering inspiratory-inhibitory reflex (B.H. reflex). The high reproducibility of the T1/T0 vs. deltaVL relationship in many subjects showed the light influence of voluntary control on apnoea's duration. In each subject, S and VTh.L. were compared with ventilatory variables measured during eupnoea. A fast pattern of breathing (i.e. small inspired volume and short inspiratory duration) was associated with high value of S and low VTh.L. Moreover VTh.L. was near the tidal volume range in subjects where the B.H. reflex was the more potent. Thus, vagal afferents relating to this reflex could modulate the eupnoeic pattern of some subjects.

Adolescent↗

PubMed1977

Effects of water immersion on lung volumes: implications for body composition analysis.

Lung volumes of 20 healthy young men were measured before and after water immersion to the neck level. Immersion resulted in significant decreases (P less than 0.01) in forced vital capacity (FVC) (8.9%), expiratory reserve volume (ERV) (61%), total lung capacity (TLC) (5.6%), and functional residual capacity (FRC) (2.9%). Significant increases were observed in inspiratory capacity (IC) (10%) and residual volume (RV) (6.7%). The increase in RV was attributed to a possible "stiffness" of the lung tissue caused by pulmonary vascular engorgement. Densitometric analysis was made on each subject using hydrostatic weighing techniques. Subsequent calculation of body density and per-cent body fat indicated significant (P less than 0.01) differences when using RV measured on land and in water. Body fat was 14.0% using the land RV in the computation of density and decreased to 13.4% using the RV measured in water. It was concluded that when obtaining body density values. RV should be measured concurrently while the subject is in the water.

Adult↗

PubMed1979

Effects of neuromuscular blockade on respiratory mechanics in conscious man.

The effect of submaximal neuromuscular blockade (SMNB) on lung and chest wall mechanics was studied in six normal, awake subjects infused with pancuronium. Measurements of static lung volumes, specific airway conductance (sGaw), maximum expiratory and inspiratory flow-volume (MEFV, MIFV) curves, and static pressure-volume (PV) curves of the lung and of the relaxed chest wall were obtained after lung recoil pressure (Pst(L)) at full inflation had been reduced to 60 +/- 10% of control. Inspiratory capacity was decreased, but residual volume was not increased. Inspiratory PV curve of the lung was not modified, and the observed decrease in expiratory compliance and the slight increase in Pst(L) during deflation were compatible with the altered lung volume history. SMNB did not modify sGaw nor the relationship between Pst(L) and MEF; by contrast it markedly reduced MIF rates. Finally, SMNB transposed the chest wall PV curve to higher levels on the pressure axis (it decreased the outward pull of the chest wall) without greatly affecting its slope, and thereby it reduced the resting level of the respiratory system. We conclude that 1) muscle weakness per se does not affect the eleastic properties of the lungs and airways, and 2) involuntary respiratory muscle activity influences the elastic recoil of the chest wall. We believe this muscle activity originates from muscle spindles, and lies essentially in the inspiratory portion of the intercostal musculature.

Adult↗

PubMed1992

Effect of volume history on changes in DLcoSB-3EQ with lung volume in normal subjects.

The purpose of this study was to determine the relationship between the three-equation diffusing capacity for carbon monoxide (DLcoSB-3EQ) and lung volume and to determine how this relationship was altered when maneuvers were immediately preceded by a deep breath. DLcoSB-3EQ maneuvers were performed in nine healthy subjects either immediately after a deep breath or after tidal breathing for 10 min. The maneuvers consisted of slow inhalation of test gas from functional residual capacity to 25, 50, 75, or 100% of the inspiratory capacity and, without breath holding, slow exhalation to residual volume. After either a deep breath or tidal breathing, we found that DLcoSB-3EQ decreased nonlinearly with decreasing lung volume. At all lung volumes, DLcoSB-3EQ was significantly greater when measured after a deep breath than after tidal breathing. This effect increased as lung volume decreased, so that the greatest difference between DLcoSB-3EQ after a deep breath and that after tidal breathing occurred at the lowest lung volume. We conclude that a deep breath or spontaneous sigh has a role in reestablishing the pathway for gas exchange during tidal breathing.

Adult↗

PubMed1975

[Respiratory functions in parkinsonian patients with predominant akinesia during treatment with decarboxylase-blocked L-dopa (author's transl)].

The effect of decarboxylase (DC)-blocked L-dopa (proportion of 4: 1) on respiratory function was tested by spirometry in 30 patients with Parkinson's disease. It was possible to improve restrictive ventilatory abnormalities of extra-pulmonary origin (weakness of respiratory musculature). Vital capacity (VC) increased by 0.21 litre. Thisincrease was due to a raised inspiratory capacity and thus an increase in the active part of ventilation. Forced expiration volume (FEV1) was improved by 0.32 litre, FEV1/VC remaining unchanged, which demonstrates that the restrictive ventilatory abnormality was affected. Inspiratory volume (VT) and minute volume at constant respiratory rate increased by 0.07 and 1.171, respectively. These results must be interpreted with caution, but they suggest a raised metabolic level with regained mobility during treatment. All quoted results, except those of respiratory rate and minute volume, were statistically significant (2 mu equals 0.01).

Adult↗