Decay of inspiratory muscle pressure during expiration in anesthetized kyphoscoliosis patients

1992 ◽  
Vol 72 (2) ◽  
pp. 712-720 ◽  
Author(s):  
A. Baydur
Keyword(s):  
Flow Resistance ◽  
Relaxation Method ◽  
Normal Subjects ◽  
Respiratory Impedance ◽  
Elastic Recoil ◽  
Intrinsic Resistance ◽  
Inspiratory Muscles ◽  
The Mean ◽  
Work Done ◽  
Mean Time

The decay of pressure developed by the inspiratory muscles during expiration (PmusI) has not been studied in subjects with increased respiratory impedance such as in kyphoscoliosis. PmusI was compared in 11 anesthetized patients with kyphoscoliosis with that in 11 anesthetized normal subjects. PmusI was obtained according to the following equation: PmusI(t) = Ers.V(t) - K1V(t) - K2V2(t), where V is volume and V is airflow at any instant t during spontaneous expiration, Ers is the passive elastance, and K1V + K2V2 is the flow resistance (curvilinear in both groups because of the endotracheal tube and the intrinsic resistance in the kyphoscoliotics) of the total respiratory system. Ers was determined by the relaxation method and resistance from the ensuing V-V relationships during the ensuing relaxed expiration. Changes in impedance due to pliometric work done by the inspiratory muscles during relaxation were neglected. Subjects in both groups showed marked braking of expiratory flow by PmusI. The mean time for PmusI to decrease to 50 and 0% amounted to 17 and 8% less, respectively, in the kyphoscoliosis group. Average values for flow-resistive work in the control and kyphoscoliosis groups both amounted to approximately 40% of the elastic energy stored during inspiration. The remaining portion, used as negative work, amounted to approximately 60% in both groups. Expiratory braking in anesthetized kyphoscoliotic patients appears to be in proportion to their magnitude of elastic recoil and intrinsic flow resistance.

Decay of inspiratory muscle pressure during expiration in conscious humans

1985 ◽  
Vol 58 (6) ◽  
pp. 1859-1865 ◽  
Author(s):  
C. D. Shee ◽  
Y. Ploy-Song-Sang ◽  
J. Milic-Emili
Keyword(s):  
Respiratory System ◽  
Elastic Energy ◽  
Relaxation Method ◽  
Inspiratory Muscle ◽  
Expiratory Time ◽  
Negative Work ◽  
Inspiratory Muscles ◽  
The Mean ◽  
Spontaneously Breathing ◽  
Mean Time

In eight conscious spontaneously breathing adults we studied the decay of pressure developed by the inspiratory muscles during expiration (PmusI). PmusI was obtained according to the following equation: PmusI(t) = Ers X V(t) - Rrs X V(t), where V is volume and V is flow at any instant t during spontaneous expiration, and Ers and Rrs are, respectively, the passive elastance and resistance of the total respiratory system. Ers was determined with the relaxation method, and resistance with the interrupter method. All subjects showed marked braking of expiratory flow by PmusI. The mean time for PmusI to reduce to 50 and 0% amounted, respectively, to 23 and 79% of expiratory time. During expiration, 24–55% of the elastic energy stored during inspiration was used as resistive work and the remainder (45–76%) as negative work.

Analysis of reproducibility, evaluation, and preference of the new iC100 rebound tonometer versus iCare PRO and Perkins portable applanation tonometry

2019 ◽  
Vol 30 (6) ◽  
pp. 1349-1355 ◽  
Author(s):  
Mercedes Molero-Senosiaín ◽  
Laura Morales-Fernández ◽  
Federico Saenz-Francés ◽  
Julian García-Feijoo ◽  
Jose María Martínez-de-la-Casa
Keyword(s):  
Intraocular Pressure ◽  
Visual Analogue Scale ◽  
Analogue Scale ◽  
Normal Subjects ◽  
Applanation Tonometry ◽  
Rebound Tonometer ◽  
The Mean ◽  
The Difference ◽  
The Comparative Study ◽  
Mean Time

Objectives: To analyze the reproducibility of the new iC100 rebound tonometer, to compare its results with the applanation tonometry and iCare PRO and to evaluate the preference between them. Materials and methods: For the study of reproducibility, 15 eyes of 15 healthy Caucasian subjects were included. Three measurements were taken each day in three separate sessions. For the comparative study, 150 eyes of 150 Caucasian subjects were included (75 normal subjects and 75 patients with glaucoma). Three consecutive measurements were collected with each tonometer, randomizing the order of use. The discomfort caused by each tonometer was evaluated using the visual analogue scale. Results: No statistically significant differences were detected between sessions. In the comparison between tonometers, the measurements with iC100 were statistically lower than those of Perkins (−1.35 ± 0.417, p = 0.004) and that iCare PRO (−1.41 ± 0.417, p = 0.002). The difference between PRO and Perkins was not statistically significant ( p = 0.990). The mean time of measurement (in seconds) with iC100 was significantly lower than with Perkins (6.74 ± 1.46 vs 15.53 ± 2.01, p < 0.001) and that PRO (6.74 ± 1.46 vs 11.53 ± 1.85, p < 0.001). Visual analogue scale score with iC100 was lower than Perkins (1.33 ± 0.99 vs 1.73 ± 1.10, p < 0.05). In total, 61.7% preferred iC100 against Perkins. Conclusion: The reproducibility of this instrument has been proven good. iC100 underestimates intraocular pressure compared to applanation tonometry at normal values and tends to overestimate it in high intraocular pressure values. Most of the subjects preferred iC100 tonometer.

Cholinergic stimulation induces asynchrony between the circular and longitudinal muscle contraction during esophageal peristalsis

2008 ◽  
Vol 294 (3) ◽  
pp. G694-G698 ◽  
Author(s):  
Hariprasad Korsapati ◽  
Arash Babaei ◽  
Valmik Bhargava ◽  
Ravinder K. Mittal
Keyword(s):  
Longitudinal Muscle ◽  
Acetylcholinesterase Inhibitor ◽  
Time Lag ◽  
Control Period ◽  
Temporal Correlation ◽  
Normal Subjects ◽  
Esophageal Peristalsis ◽  
Nutcracker Esophagus ◽  
The Mean ◽  
Mean Time

In healthy subjects, a close temporal correlation exists between contractions of the circular muscle (CM) and longitudinal muscle (LM) layers of the esophagus. Patients with nutcracker esophagus show disassociation between the peak of contractions of the CM and LM layers and the peak of contraction 1–3 s apart (Jung HY, Puckett JL, Bhalla V, Rojas-Feria M, Bhargava V, Liu J, Mittal RK. Gastroenterology 128: 1179–1186, 2005). The purpose of the present study was to evaluate the effect of acetylcholinesterase inhibitor (edrophonium) and acetylcholine receptor antagonist (atropine) on human esophageal peristalsis in normal subjects. High-frequency intraluminal ultrasound imaging and manometry were performed simultaneously during swallow-induced peristalsis in ten normal subjects. Standardized 5-ml water swallows were recorded 2 cm above the lower esophageal sphincter under three study conditions: control, edrophonium (80 μg/kg iv), and atropine (10 μg/kg iv). A close temporal correlation exists between the peak pressure and peak wall thickness during the control period. The mean time lag between the peak LM and peak CM contraction was 0.03 s. After edrophonium administration, the mean contraction amplitude increased from 101 ± 9 mmHg to 150 ± 20 mmHg ( P < 0.05) and mean peak muscle thickness increased from 3.0 ± 0.2 mm to 3.6 ± 0.3 mm ( P < 0.01), and duration of both CM and LM contractions were also increased. Furthermore, the mean time difference between the peak LM and CM was increased to 1.1 s, (ranging 0.2 to 3.4 s) ( P < 0.0001). We conclude that cholinomimetic agent induces discoordination between the two muscle layers of the esophagus.

Dissociation between diaphragmatic and rib cage muscle fatigue

1988 ◽  
Vol 64 (3) ◽  
pp. 959-965 ◽  
Author(s):  
J. W. Fitting ◽  
T. D. Bradley ◽  
P. A. Easton ◽  
M. J. Lincoln ◽  
M. D. Goldman ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Normal Subjects ◽  
Breathing Patterns ◽  
Recruitment Pattern ◽  
Rib Cage ◽  
Inspiratory Muscles ◽  
Resistive Breathing ◽  
Emg Power Spectrum ◽  
The Mean ◽  
Substantial Degree

To assess rib cage muscle fatigue and its relationship to diaphragmatic fatigue, we recorded the electromyogram (EMG) of the parasternal intercostals (PS), sternocleidomastoid (SM), and platysma with fine wire electrodes and the EMG of the diaphragm (DI) with an esophageal electrode. Six normal subjects were studied during inspiratory resistive breathing. Two different breathing patterns were imposed: mainly diaphragmatic or mainly rib cage breathing. The development of fatigue was assessed by analysis of the high-to-low (H/L) ratio of the EMG. To determine the appropriate frequency bands for the PS and SM, we established their EMG power spectrum by Fourier analysis. The mean and SD for the centroid frequency was 312 ± 16 Hz for PS and 244 ± 48 Hz for SM. When breathing with the diaphragmatic patterns, all subjects showed a fall in H/L of the DI and none had a fall in H/L of the PS or SM. During rib cage emphasis, four out of five subjects showed a fall in H/L of the PS and five out of six showed a fall in H/L of the SM. Four subjects showed no fall in H/L of the DI; the other two subjects were unable to inhibit diaphragm activity to a substantial degree and did show a fall in H/L of the DI. Activity of the platysma was minimal or absent during diaphragmatic emphasis but was usually strong during rib cage breathing. We conclude that fatigue of either the diaphragm or the parasternal and sternocleidomastoid can occur independently according to the recruitment pattern of inspiratory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Maximal shortening of inspiratory muscles: effect of training

1983 ◽  
Vol 54 (6) ◽  
pp. 1618-1623 ◽  
Author(s):  
C. H. Fanta ◽  
D. E. Leith ◽  
R. Brown
Keyword(s):  
Lung Volume ◽  
Vital Capacity ◽  
Total Lung Capacity ◽  
Training Group ◽  
Normal Subjects ◽  
Pressure Control ◽  
Base Line ◽  
Lung Capacity ◽  
Inspiratory Muscles ◽  
The Mean

Normal subjects can increase their vital capacity by appropriate training. We tested whether that change can be achieved by greater maximal shortening of the inspiratory muscles without concomitant increases in peak static inspiratory pressures. Sixteen healthy volunteers participated in the study: eight were randomly assigned to make 20 inhalations to total lung capacity, held for 10 s with the glottis open, each day for 6 wk; the remainder served as nontraining controls. Before and after the 6-wk study period, we made multiple determinations of lung volumes and of curves relating lung volume to maximal static inspiratory (and expiratory) pressure. Control subjects had no significant changes from base line in any variable. In the training group, the mean vital capacity increased 200 +/- 74 ml (P less than 0.05) or 3.9 +/- 1.3% (P less than 0.02), without a significant change in residual volume. After training, the mean maximal inspiratory pressure at the airway opening (PI) at a lung volume equal to the base-line total lung capacity was 27 +/- 8 cmH2O in this group (vs. zero before training; P less than 0.02). Values of PI in the mid-vital capacity range did not change. We conclude that in response to appropriate training stimuli inspiratory muscles can contract to shorter minimal lengths, a capacity potentially important in progressive pulmonary hyperinflation.

Sex and age differences in pulmonary mechanics in normal nonsmoking subjects

1976 ◽  
Vol 41 (1) ◽  
pp. 20-25 ◽  
Author(s):  
G. J. Gibson ◽  
N. B. Pride ◽  
C. O'cain ◽  
R. Quagliato
Keyword(s):  
Sex Differences ◽  
Elderly Women ◽  
Young Men ◽  
Maximum Flow ◽  
Normal Subjects ◽  
Pulmonary Mechanics ◽  
Elastic Recoil ◽  
Inspiratory Muscles ◽  
Maximum Expiratory Flow ◽  
Effects Of Aging

Maximun flow-volume, static pressure-volume, and maximum flow static recoil curves of three groups of nonsmoking, normal subjects (young men, youngwomen, elderly women) were used to assess age and sex differences in pulmonary mechanics. No significant sex differences in maximum flow were seen butthe young men showed higher lung recoil pressures at full inflation. When the influence of the inspiratory muscles and chest wall was excluded by exponential extrapolation of the pressure-volume curves to a maximum volume thebulk elastic properties of the lungs of young men and women appeared identical. Loss of maximum expiratory flow at low lung volumes and of lung recoilpressure occurred with age in nonsmoking women in whom emphysema should be minimal and therefore indicate true physiological effects of aging. The changes in pulmonary mechanics with age are consistent with an increase in unstressed dimensions and loss of elastic recoil of both alveoli and airways.

Respiratory mechanics and breathing pattern during and following maximal exercise

1984 ◽  
Vol 57 (6) ◽  
pp. 1773-1782 ◽  
Author(s):  
M. Younes ◽  
G. Kivinen
Keyword(s):  
Time Course ◽  
Maximal Exercise ◽  
Dynamic Pressure ◽  
Respiratory Muscles ◽  
Normal Subjects ◽  
Esophageal Pressure ◽  
Inspiratory Pressure ◽  
Elastic Recoil ◽  
Inspiratory Muscles ◽  
Inspiratory Muscle Fatigue

We looked for evidence of changes in lung elastic recoil and of inspiratory muscle fatigue at maximal exercise in seven normal subjects. Esophageal pressure, flow, and volume were measured during spontaneous breathing at increasing levels of cycle exercise to maximum. Total lung capacity (TLC) was determined at rest and immediately before exercise termination using a N2-washout technique. Maximal inspiratory pressure and inspiratory capacity were measured at 1-min intervals. The time course of instantaneous dynamic pressure of respiratory muscles (Pmus) was calculated for the spontaneous breaths immediately preceding exercise termination. TLC volume and lung elastic recoil at TLC were the same at the end of exercise as at rest. Maximum static inspiratory pressures at exercise termination were not reduced. However, mean Pmus of spontaneous breaths at end exercise exceeded 15% of maximum inspiratory pressure in five of the subjects. We conclude that lung elastic recoil is unchanged even at maximal exercise and that, while inspiratory muscles operate within a potentially fatiguing range, the high levels of ventilation observed during maximal exercise are not maintained for a sufficient time to result in mechanical fatigue.

Maximum expiratory flow-volume curves during short periods of microgravity

1991 ◽  
Vol 70 (6) ◽  
pp. 2587-2596 ◽  
Author(s):  
H. J. Guy ◽  
G. K. Prisk ◽  
A. R. Elliott ◽  
J. B. West
Keyword(s):  
Vital Capacity ◽  
Normal Subjects ◽  
Flow Volume ◽  
Elastic Recoil ◽  
Microgravity Research ◽  
Maximum Expiratory Flow ◽  
Research Aircraft ◽  
The Mean ◽  
Expiratory Flow ◽  
The Individual

To elucidate the effect of normal gravitation on the shape of the maximum expiratory flow-volume (MEFV) curve, we studied nine normal subjects in a National Aeronautics and Space Administration microgravity research aircraft. They performed multiple MEFV maneuvers at 0, 1, and approximately 2 G. The MEFV curves for each subject were filtered, aligned at residual volume, and ensemble averaged to produce an average MEFV curve for each state, allowing differences to be studied. Most subjects showed a decrease in the forced vital capacity at 0 G, which we attribute to an increased intrathoracic blood volume. In most of these subjects, the mean lung volume associated with a given flow was lower at 0 G over about the upper half of the vital capacity. This is similar to the change previously reported during headout immersion and is consistent with the known effect of engorgement of the lung with blood on elastic recoil. There were also consistent but highly individual changes in the position and magnitude of detailed features of the curve, the individual patterns being similar to those previously reported on transition from the erect to the supine position. This supports the idea that the location and motion of choke points that determine the detailed individual configuration of MEFV curves can be significantly influenced by gravitational forces, presumably via the effects of change in longitudinal tension on local airway pressure-diameter behavior and thus wave speed.

Oxygen cost of resistive-loaded breathing in quadriplegia

1992 ◽  
Vol 73 (3) ◽  
pp. 825-831 ◽  
Author(s):  
H. Manning ◽  
F. D. McCool ◽  
S. M. Scharf ◽  
E. Garshick ◽  
R. Brown
Keyword(s):  
Chest Wall ◽  
Energy Cost ◽  
Regression Line ◽  
Normal Subjects ◽  
Oxygen Cost ◽  
Rib Cage ◽  
Inspiratory Muscles ◽  
Residual Capacity ◽  
Loaded Breathing ◽  
The Mean

We hypothesized that, in quadriplegia, chest wall distortion would increase the energy cost of ventilation. To assess this, we measured the oxygen cost of breathing (VO2 resp) and changes in chest wall configuration during inspiratory resistive-loaded breathing tasks in five quadriplegic and five normal subjects. Each subject performed three breathing tasks that spanned a range of work rates (Wtot). Configurational changes of the abdomen and upper, lower, and transverse rib cage were assessed with magnetometers. We found that 1) in both groups, VO2resp increased linearly with Wtot over the range of tasks performed, 2) the mean slope of the regression line of VO2resp vs. Wtot was greater for quadriplegic than for normal subjects (3.7 +/- 0.8 vs. 2.0 +/- 0.7 ml O2/J, P less than 0.01), 3) efficiency of breathing (Wtot/VO2resp) was less for quadriplegic than for normal subjects (1.9 +/- 0.6 vs. 3.5 +/- 1.4%, P less than 0.001), 4) during inhalation, upper and lower rib cages behaved similarly in the two groups, but the quadriplegic subjects had a decrease in transverse rib cage and a much greater increase in abdomen than normal subjects, and 5) functional residual capacity decreased in normal but not in quadriplegic subjects during the breathing tasks. We conclude that the lesser efficiency of breathing in quadriplegia may be related to the elastic work of chest wall distortion, shorter mean operational diaphragm length, and possibly differences between normal and quadriplegic subjects in mechanical advantage of available inspiratory muscles.

Effect of alterations in end-tidal CO2 tension on flow resistance

1964 ◽  
Vol 19 (4) ◽  
pp. 745-749 ◽  
Author(s):  
Michael T. Newhouse ◽  
Margaret R. Becklake ◽  
Peter T. Macklem ◽  
Maurice McGregor
Keyword(s):  
Flow Resistance ◽  
Work Of Breathing ◽  
Normal Subjects ◽  
Minute Volume ◽  
Oxygen Cost ◽  
Voluntary Hyperventilation ◽  
Consistent Increase ◽  
The Mean ◽  
End Tidal ◽  
End Tidal Co2

The effect of PaCOCO2 on flow resistance and on the mechanical work of ventilating the lung was studied in five normal subjects during sustained voluntary hyperventilation. Hypocapnia caused a consistent increase in flow resistance. Thus, for a minute volume of approximately 30 liters/ min the mean inspiratory flow resistance was 133% greater and the mean respiratory work of ventilating the lungs 68% greater at PaCOCO2 20–25 mm Hg compared to values at 45–50 mm Hg. End-expiratory pressure and compliance were unaffected. Atropine and isoproterenol each markedly diminished the responsiveness of the airways to low PaCOCO2 levels and, given together, blocked the effect completely. These findings could largely account for the increase in oxygen cost of breathing, and in cardiac output associated with voluntary (i.e., hypocapneic) hyperventilation. PaCOCO2; work of breathing; mechanical properties Submitted on June 24, 1963

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