O2 cost of inspiratory and expiratory resistive breathing in humans

1988 ◽  
Vol 65 (6) ◽  
pp. 2518-2523 ◽  
Author(s):  
D. S. Dodd ◽  
J. Yarom ◽  
S. H. Loring ◽  
L. A. Engel
Keyword(s):  
Normal Subjects ◽  
Normal Male ◽  
O2 Uptake ◽  
Pressure Time ◽  
Resistive Breathing ◽  
Before And After ◽  
Expiratory Muscles ◽  
Variable Recruitment ◽  
Equivalent Load ◽  
Male Subjects

In six normal male subjects we compared the O2 cost of resistive breathing (VO2 resp) between equivalent external inspiratory (IRL) and expiratory loads (ERL) studied separately. Each subject performed four pairs of runs matched for tidal volume, breathing frequency, flow rates, lung volume, pressure-time product, and work rate. Basal O2 uptake, measured before and after pairs of loaded runs, was subtracted from that measured during resistive breathing to obtain VO2 resp. For an equivalent load, the VO2 resp during ERL (184 +/- 17 ml O2/min) was nearly twice that obtained during IRL (97 +/- 9 ml O2/min). This twofold difference in efficiency between inspiratory and expiratory resistive breathing may reflect the relatively lower mechanical advantage of the expiratory muscles in overcoming respiratory loads. Variable recruitment of expiratory muscles may explain the large variation of results obtained in studies of respiratory muscle efficiency in normal subjects.

Near-maximal voluntary hyperpnea and ventilatory muscle function

1984 ◽  
Vol 57 (6) ◽  
pp. 1742-1748 ◽  
Author(s):  
T. R. Bai ◽  
B. J. Rabinovitch ◽  
R. L. Pardy
Keyword(s):  
Muscle Function ◽  
Low Frequency ◽  
Normal Subjects ◽  
Pressure Time ◽  
Before And After ◽  
Expiratory Muscles ◽  
Four Levels ◽  
Frequency Relationship ◽  
Low Frequency Power ◽  
Relationship Of

Because of its potential relevance to heavy exercise we studied the ventilatory muscle function of five normal subjects before, during, and after shortterm near-maximal voluntary normocapnic hyperpnea. Measurements of pleural and abdominal pressures and diaphragm electromyogram (EMG) during hyperpnea and of maximum respiratory pressures before and after hyperpnea were made at four levels of ventilation: 76, 79, and 86% maximal voluntary ventilation (MVV) and at MVV. Measurements of pleural and abdominal pressures and diaphragm electromyogram (EMG) during hyperpnea and of maximum respiratory pressures before and after hyperpnea were made. The pressure-stimulation frequency relationship of the diaphragm obtained by unilateral transcutaneous phrenic nerve stimulation was studied in two subjects before and after hyperpnea. Decreases in maximal inspiratory (PImax) and transdiaphragmatic (Pdimax) strength were recorded posthyperpnea at 76 and 79% MVV. Decreases in the pressure-frequency curves of the diaphragm and the ratio of high-to-low frequency power of the diaphragm EMG occurred in association with decreases in Pdimax. Analysis of the pressure-time product (P X dt) for the inspiratory and expiratory muscles individually indicated the increasing contribution of expiratory muscle force to the attainment of higher levels of ventilation. Demonstrable ventilatory muscle fatigue may limit endurance at high levels of ventilation.

The Retention of Lung Secretions during the Night in Normal Subjects

1978 ◽  
Vol 55 (6) ◽  
pp. 523-527 ◽  
Author(s):  
J. R. M. Bateman ◽  
D. Pavia ◽  
S. W. Clarke
Keyword(s):  
Diurnal Variation ◽  
Chronic Bronchitis ◽  
Mucociliary Clearance ◽  
Normal Subjects ◽  
Early Morning ◽  
Normal Male ◽  
Related Phenomenon ◽  
Before And After ◽  
Male Subjects

1. Mucociliary clearance has been measured over a 6 h period by using the radioaerosol technique in seven normal male subjects lying supine, both during the day when awake, and during the night when asleep. 2. The percentage of radioaerosol cleared during the night, when asleep, was significantly less than during the day when awake (P < 0.02). 3. A comparison of radioaerosol clearance before and after the time of onset of sleep demonstrates that reduced clearance occurred during sleep, indicating that this is probably a sleep-related phenomenon and not merely a result of diurnal variation. 4. This finding has important implications for patients with chronic bronchitis or asthma, in whom early morning cough or wheeze may be a predominant feature.

Impedance measurement during air and He-O2 breathing before and after salbutamol in normal subjects

1990 ◽  
Vol 69 (5) ◽  
pp. 1665-1669
Author(s):  
E. F. Wouters
Keyword(s):  
Impedance Measurement ◽  
Normal Subjects ◽  
Normal Male ◽  
Respiratory Resistance ◽  
Adrenergic Agonist ◽  
Before And After ◽  
The Subject ◽  
Beta Adrenergic Agonist ◽  
Male Subjects ◽  
Inductive Reactance

Total respiratory resistance and reactance from 4 to 52 Hz were determined by the method of forced pseudorandom noise oscillation in 20 normal male subjects before and after inhalation of 0.200 mg salbutamol (albuterol) and before and after the subjects were equilibrated with 80% He-20% O2. During air breathing, there was a statistically significant decrease of resistance values at lower frequencies after inhalation of salbutamol. When the subject was equilibrated with 80% He-20% O2, total respiratory resistance markedly decreased at all frequencies, and a negative frequency dependence of resistance was observed between 8 and 20 Hz. Resistance values further decreased during He-O2 breathing after inhalation of salbutamol. After inhalation of salbutamol, reactance values increased during air and He-O2 breathing. The density-dependent decrease of the real part of impedance can be explained by a decrease of turbulence in the larger airways. The bronchodilating effect of salbutamol was not influenced by a change in the physical properties of the inhaled gas. During He-O2 breathing, reactance values significantly decreased, resulting in an increase of resonant frequency due to a decrease of inductive reactance. It is concluded that an increase in the capacitance of the respiratory system must be supposed to explain the increase in reactance values after inhalation of the beta-adrenergic agonist salbutamol.

scholarly journals Comparison of the Effects of Intravenous Papaverine Hydrochloride and Oral Pavabid HP Capsulets on Regional Cerebral Blood Flow in Normal Individuals

1983 ◽  
Vol 3 (4) ◽  
pp. 442-447 ◽  
Author(s):  
Lawrence C. McHenry ◽  
David A. Stump ◽  
George Howard ◽  
Thomas T. Novack ◽  
Don H. Bivins ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Regional Cerebral Blood Flow ◽  
Normal Subjects ◽  
Normal Male ◽  
Regional Cerebral Blood ◽  
Normal Individuals ◽  
Left And Right ◽  
Male Subjects ◽  
Papaverine Hydrochloride

A single-blind study was conducted in 13 right-handed normal male subjects to compare the effects of oral and i.v. papaverine on regional cerebral blood flow (rCBF). Six xenon-133 inhalation rCBF measurements were performed on each subject; three tests—baseline, placebo, and drug evaluations—were carried out on each of two separate days. The oral and i.v. drugs were randomized for first-day administration. rCBF, measured as flow gray (FG), increased significantly (p ≤ 0.001) from baseline with both drug forms. Increases of 10.53% and 13.94% (left and right hemispheres, respectively) were demonstrated 90 min after a single 600-mg dose of oral papaverine. Increases of 5.09% and 8.69%, respectively, were recorded immediately after a single 100-mg dose of i. v. papaverine. FG also increased significantly (p ≤ 0.001) for both drug forms when compared to that of placebo. Placebo produced only a slight increase (not significant) with both the oral and i.v. groups. The data show that both oral and i.v. papaverine are equally effective in increasing rCBF in normal subjects.

Effect of Single and Combined Infusions of Angiotensin II and Aldosterone on Colonic Potential Difference, Blood Pressure and Renal Function, in Patients with Adrenal Deficiency

1975 ◽  
Vol 48 (3) ◽  
pp. 219-226
Author(s):  
A. D. Efstratopoulos ◽  
W. S. Peart
Keyword(s):  
Blood Pressure ◽  
Renal Function ◽  
Plasma Concentrations ◽  
Young Male ◽  
Normal Subjects ◽  
Potential Difference ◽  
Normal Male ◽  
Adrenal Deficiency ◽  
Increased Sensitivity ◽  
Male Subjects

1. The effect of single and combined infusions of angiotensin and aldosterone on colonic potential difference, blood pressure and renal function was studied in two normal male subjects and four female patients with adrenal deficiency maintained only on cortisone. 2. Aldosterone had its usual effect on colonic potential difference and it was possible to show that angiotensin had a small but definite effect of its own in the absence of aldosterone. The two hormones produced a summation response when given together. 3. The effects on renal function in two normal young male subjects were similar to those known previously. The response of the patients was different and probably reflected a number of factors, such as age, sex and long-standing adrenal deficiency. 4. Although the numbers were small, both normal subjects and patients showed a significantly greater rise of blood pressure with combined infusions of angiotensin and aldosterone than with angiotensin alone. The plasma concentrations of angiotensin were similar with both types of infusion, and so increased sensitivity to angiotensin in the presence of aldosterone is postulated.

Pressure-time product, work rate, and endurance during resistive breathing in humans

1988 ◽  
Vol 64 (4) ◽  
pp. 1397-1404 ◽  
Author(s):  
D. S. Dodd ◽  
S. Kelly ◽  
P. W. Collett ◽  
L. A. Engel
Keyword(s):  
Blood Flow ◽  
Respiratory Muscle ◽  
Muscle Blood Flow ◽  
Normal Subjects ◽  
Work Rate ◽  
Available Energy ◽  
Pressure Time ◽  
Mouth Pressure ◽  
Resistive Breathing ◽  
Pressure Time Product

We examined the effect of increasing work rate, without a corresponding increase in the pressure-time product, on energy cost and inspiratory muscle endurance (Tlim) in five normal subjects during inspiratory resistive breathing. Tidal volume, mean inspiratory mouth pressure, duty cycle, and hence the pressure-time product were kept constant, whereas work rate was varied by changing the frequency of breathing. There was a linear decrease in Tlim of -2.1 ± 0.5 s.J-1.min-1 (r = 0.87 ± 0.06) with increasing work rate. The data satisfied a model of energy balance during fatiguing runs (Monod and Scherrer. Ergonomics 8: 329-337, 1965) and were consistent with the hypothesis that the rate of energy supply, or respiratory muscle blood flow, is fixed when the pressure-time product is constant. Our results indicate that during inspiratory resistive breathing against fatiguing loads, work rate determines endurance independently of the pressure-time product. On the basis of the model, our results lead to estimates of respiratory muscle blood flow and available energy stores under the conditions of our experiment.

Induced venous pooling and cardiorespiratory responses to exercise after bed rest

1982 ◽  
Vol 52 (5) ◽  
pp. 1343-1348 ◽  
Author(s):  
V. A. Convertino ◽  
H. Sandler ◽  
P. Webb ◽  
J. F. Annis
Keyword(s):  
Bed Rest ◽  
Control Group ◽  
O2 Uptake ◽  
Vo2 Max ◽  
Endurance Time ◽  
Venous Pooling ◽  
Fluid Shifts ◽  
Before And After ◽  
Male Subjects ◽  
Experimental Group

The purpose of this study was to deliberately induce venous pooling the lower extremities of bed-rested subjects to determine whether such distention may reverse the reduction in maximal O2 uptake that has regularly been observed. Bed-rest deconditioning was assessed in eight healthy male subjects by measuring submaximal and maximal O2 uptake (VO2 max), ventilation, and heart rate (HRmax) before and after 15 days of bed rest. During bed rest four subjects in the experimental group received daily treatments of venous pooling for 210 min/day with a reverse gradient garment (RGG), whereas the four subjects in the control group received no treatment. Compared with prebed-rest values, VO2max was reduced by 14.0 (P less than 0.05), HRmax was increased by 4.2 (P less than 0.05), and endurance time for the exercise test was decreased by 9.2% (P less than 0.05) in the control group. In the RGG group, VO2max, HRmax, and endurance time were essentially unchanged after bed rest. The plasma volume (PV) of the control group decreased by 16.7 (P less than 0.05) after bed rest compared with a 10.3% (not significant) reduction in the RGG group. The percent delta PV was related to the percent delta VO2 max (r = 0.75, P less than 0.05) and percent delta HR max (r = 0.65, P less than 0.05). The data support the hypothesis that the lack of venous pooling and associated fluid shifts contribute the decrement in VO2 max associated with bed-rest deconditioning.

Practical Importance of a Preceding Full Inhalation or Exhalation upon the Measurement of Airway Resistance

1980 ◽  
Vol 58 (3) ◽  
pp. 249-253 ◽  
Author(s):  
T. Higenbottam ◽  
T. J. H. Clark
Keyword(s):  
Airway Resistance ◽  
Practical Importance ◽  
Normal Male ◽  
Indirect Measurements ◽  
Lung Capacity ◽  
Airway Function ◽  
Before And After ◽  
Residual Capacity ◽  
Normal Men ◽  
Male Subjects

1. Airway resistance was measured close to functional residual capacity before and after a full inhalation of total lung capacity, as well as before and after a full exhalation to residual volume. 2. The effects of these volume manoeuvres upon airway resistance (and associated lung volume) were determined in four resting normal male subjects and in six normal men during experimentally induced bronchoconstriction after breathing an air/histamine mist from a Wright's nebulizer. 3. In four men the duration of the effect of a full inhalation upon airway resistance after induced bronchoconstriction was assessed separately. 4. Neither a full inhalation nor a full exhalation altered airway resistance under normal conditions. However, a full inhalation reduced airway resistance in the presence of bronchoconstriction and this effect lasted for a period of 45 s. Even with bronchoconstriction, a full exhalation had no effect on airway resistance. 5. Account must therefore be taken of the potential reduction in airway resistance which may result from a full inhalation, particularly when indirect measurements of airway function which involve a full inhalation, such as forced spirometry, are used to assess airway obstruction.

scholarly journals Direct measurement of the lumped constant for 2-deoxy-[1-14C]glucose in vivo in human skeletal muscle

2000 ◽  
Vol 279 (1) ◽  
pp. E228-E233 ◽  
Author(s):  
Tapio Utriainen ◽  
Stefania Lovisatti ◽  
Sari Mäkimattila ◽  
Alessandra Bertoldo ◽  
Susan Weintraub ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Insulin Infusion ◽  
Normal Subjects ◽  
Normal Male ◽  
Wide Range ◽  
Lumped Constant ◽  
Male Subjects ◽  
Forearm Vein

The lumped constant (LC) is used to convert the clearance rate of 2-deoxy-d-glucose (2-DGcr) to that of glucose (Glccr). There are currently no data to validate the widely used assumption of an LC of 1.0 for human skeletal muscle. We determined the LC for 2-deoxy-[1-14C]glucose (2-DG) in 18 normal male subjects (age, 29 ± 2 yr; body mass index, 24.8 ± 0.8 kg/m2) after an overnight fast and during physiological (1 mU · kg−1· min−1insulin infusion for 180 min) and supraphysiological (5 mU · kg−1· min−1insulin infusion for 180 min) hyperinsulinemic conditions. Normoglycemia was maintained with the euglycemic clamp technique. The LC was measured directly with the use of a novel triple tracer-based method. [3-3H]glucose, 2-[1-14C]DG, and [12C]mannitol (Man) were injected as a bolus into the brachial artery. The concentrations of [3-3H]glucose and 2-[1-14C]DG (dpm/ml plasma) and of Man (μmol/l) were determined in 50 blood samples withdrawn from the ipsilateral deep forearm vein over 15 min after the bolus injection. The LC was calculated by a formula involving blood flow calculated from Man and the Glccrand 2-DGcr. The LC averaged 1.26 ± 0.08 (range 1.06–1.43), 1.15 ± 0.05 (0.99–1.39), and 1.18 ± 0.05 (0.97–1.37) under fasting conditions and during the 1 and 5 mU · kg−1· min−1insulin infusions (not significant between the different insulin concentrations, mean LC = 1.2, P < 0.01 vs. 1.0). We conclude that, in normal subjects, the LC for 2-DG in human skeletal muscle is constant over a wide range of insulin concentrations and averages 1.2.

Coupling of muscle phosphorylation potential to glycolysis during work after short-term training

1994 ◽  
Vol 76 (6) ◽  
pp. 2586-2593 ◽  
Author(s):  
J. Cadefau ◽  
H. J. Green ◽  
R. Cusso ◽  
M. Ball-Burnett ◽  
G. Jamieson
Keyword(s):  
Muscle Glycogen ◽  
Needle Biopsy ◽  
Vastus Lateralis ◽  
O2 Uptake ◽  
Cycle Exercise ◽  
Short Term ◽  
Metabolic Adaptations ◽  
Before And After ◽  
Male Subjects ◽  
Pyruvate Ratio

To examine whether the metabolic adaptations to short-term training are expressed over a range of submaximal levels of mitochondrial respiration, seven untrained male subjects [maximal O2 uptake (VO2max) = 45.9 +/- 1.9 (SE) ml.kg-1.min-1] performed a progressive three-stage protocol of cycle exercise at 60% (20 min), 79% (20 min), and 92% (11 min) of pretraining VO2max before and after training. Training consisted of 5–6 days of cycling for 2 h/day at 65% VO2max. Muscle tissue rapidly obtained from the vastus lateralis by needle biopsy indicated that training blunted (P < 0.05) the increase in lactate observed at 60% (23.4 +/- 6.5 vs. 12.4 +/- 2.9 mmol/kg dry wt), 79% (48.9 +/- 5.1 vs. 25.6 +/- 5.2 mmol/kg dry wt), and 92% (68.3 +/- 6.4 vs. 41.5 +/- 6.5 mmol/kg dry wt) of VO2max. Training also resulted in a higher phosphocreatine and lower creatine and P(i) concentrations at both 79% (P < 0.05) and 92% (P < 0.05) of VO2max and higher muscle glycogen levels (P < 0.05). These changes were accompanied by small but significant reductions (P < 0.05) in O2 uptake at the two higher exercise intensities. Given that the lactate-to-pyruvate ratio and the calculated free ADP and AMP were also reduced (P < 0.05), it would appear that short-term training results in a tighter metabolic control over a range of mitochondrial respiratory rates.

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