Ventilatory response to helium-oxygen breathing during exercise: effect of airway anesthesia

1997 ◽  
Vol 83 (1) ◽  
pp. 82-88 ◽  
Author(s):  
Bharath S. Krishnan ◽  
Ron E. Clemens ◽  
Trevor A. Zintel ◽  
Martin J. Stockwell ◽  
Charles G. Gallagher
Keyword(s):  
Ventilatory Response ◽  
Breathing Circuit ◽  
Minute Ventilation ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Upper Airways ◽  
Warm Up ◽  
Oxygen Breathing ◽  
Exercise Effect ◽  
Constant Work Rate

Krishnan, Bharath S., Ron E. Clemens, Trevor A. Zintel, Martin J. Stockwell, and Charles G. Gallagher. Ventilatory response to helium-oxygen breathing during exercise: effect of airway anesthesia. J. Appl. Physiol. 83(1): 82–88, 1997.—The substitution of a normoxic helium mixture (HeO2) for room air (Air) during exercise results in a sustained hyperventilation, which is present even in the first breath. We hypothesized that this response is dependent on intact airway afferents; if so, airway anesthesia (Anesthesia) should affect this response. Anesthesia was administered to the upper airways by topical application and to lower central airways by aerosol inhalation and was confirmed to be effective for over 15 min. Subjects performed constant work-rate exercise (CWE) at 69 ± 2 (SE) % maximal work rate on a cycle ergometer on three separate days: twice after saline inhalation ( days 1 and 3) and once after Anesthesia ( day 2). CWE commenced after a brief warm-up, with subjects breathing Air for the first 5 min (Air-1), HeO2 for the next 3 min, and Air again until the end of CWE (Air-2). The resistance of the breathing circuit was matched for Air and HeO2. Breathing HeO2 resulted in a small but significant increase in minute ventilation (V˙i) and decrease in alveolar [Formula: see text] in both the Saline (average of 2 saline tests; not significant) and Anesthesia tests. Although Anesthesia had no effect on the sustained hyperventilatory response to HeO2breathing, theV˙i transients within the first six breaths of HeO2 were significantly attenuated with Anesthesia. We conclude that theV˙i response to HeO2 is not simply due to a reduction in external tubing resistance and that, in humans, airway afferents mediate the transient but not the sustained hyperventilatory response to HeO2 breathing during exercise.

Effects of separate rib cage and abdominal restriction on exercise performance in normal humans

1985 ◽  
Vol 58 (6) ◽  
pp. 2020-2026 ◽  
Author(s):  
S. N. Hussain ◽  
B. Rabinovitch ◽  
P. T. Macklem ◽  
R. L. Pardy
Keyword(s):  
Minute Ventilation ◽  
Normal Subjects ◽  
Cycle Ergometer ◽  
Abdominal Muscle ◽  
Work Rate ◽  
Abdominal Pressure ◽  
Transdiaphragmatic Pressure ◽  
Rib Cage ◽  
Constant Work Rate ◽  
And Control

We assessed the effects of selective restriction of movements of the rib cage (Res,rc) and abdomen (Res,ab) on ventilatory pattern, transdiaphragmatic pressure (Pdi), and electrical activity of the diaphragm (Edi) in five normal subjects exercising at a constant work rate (80% of maximum power output) on a cycle ergometer till exhaustion. Restriction of movements was achieved by an inelastic corset applied tightly around the rib cage or abdomen. Edi was recorded by an esophageal electrode, rectified, and then integrated, and peak values during inspiration were measured. Each subject exercised at the same work rate on 3 days: with Res,rc, with Res,ab, and without restriction (control). Res,rc but not Res,ab reduced exercise time (tlim). Up to tlim, minute ventilation (VE) was similar in all three conditions. At any level of VE, however, Res,rc decreased tidal volume and inspiratory and expiratory time, whereas Res,ab had no effect on the pattern of breathing. Res,ab was associated with higher inspiratory Pdi swings at any level of VE, whereas peak Edi was similar to control. Inspiratory Pdi swings were the same with Res,rc as control, but the peak Edi for a given Pdi was greater with Res,rc (P less than 0.05). During Res,rc the abdominal pressure swings in expiration were greater than with Res,ab and control. We conclude that Res,rc altered the pattern of breathing in normal subjects in high-intensity exercise, decreased diaphragmatic contractility, increased abdominal muscle recruitment in expiration, and reduced tlim. On the other hand, Res,ab had no effect on breathing pattern or tlim but was associated with increased diaphragmatic contractility.

Respiration during exercise in conscious laryngectomized humans

1989 ◽  
Vol 66 (5) ◽  
pp. 2071-2078 ◽  
Author(s):  
W. N. Gardner ◽  
M. S. Meah
Keyword(s):  
Minute Ventilation ◽  
Work Rate ◽  
Inspiratory Flow ◽  
Control Group ◽  
Respiratory Drive ◽  
Upper Airways ◽  
Expiratory Time ◽  
Expiratory Flow ◽  
End Tidal ◽  
Normal Controls

We compared respiratory patterning at rest and during steady cycle exercise at work rates of 30, 60, and 90 W in 7 male chronically laryngectomized subjects and 13 normal controls. Breathing was measured with a pneumotachograph and end-tidal PCO2 by mass spectrometer. Inspired air was humidified and enriched to 35% O2. Peak flow, volume, and times for the inspiratory and expiratory half cycles, time for expiratory flow, minute ventilation, and mean inspiratory flow were computer averaged over at least 40 breaths at rest and during the last 2 min of 5-min periods at each work rate. During the transition from rest to exercise and with increasing work rate in both groups, there was an increase in respiratory rate and depth with selective and progressive shortening of expiratory time; these responses were not significantly different between the two groups, but there was a suggestion that respiratory “drive” as quantitated by mean inspiratory flow may limit in the laryngectomized subjects at high work rates. Time for expiratory flow increased on transition from rest to exercise and then decreased in both groups as the work rate increased; it was shorter in the laryngectomy than control group at all levels. In the laryngectomized subjects there was significantly more breath-by-breath scatter in some variables at rest, but there was no difference during exercise. It is concluded that chronic removal of the larynx and upper airways in mildly hyperoxic conscious humans has only subtle and, therefore, functionally insignificant effects on breathing during moderate exercise. Evidence is provided that the upper airways can modulate expiratory flow but not expiratory time during exercise.

Lactic acidosis as a facilitator of oxyhemoglobin dissociation during exercise

1994 ◽  
Vol 76 (4) ◽  
pp. 1462-1467 ◽  
Author(s):  
W. Stringer ◽  
K. Wasserman ◽  
R. Casaburi ◽  
J. Porszasz ◽  
K. Maehara ◽  
...  
Keyword(s):  
Lactic Acidosis ◽  
Femoral Vein ◽  
Lactate Concentration ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Exercise Tests ◽  
Ergometer Exercise ◽  
Constant Work Rate ◽  
Slow Rise ◽  
Lactic Acidosis Threshold

The slow rise in O2 uptake (VO2), which has been shown to be linearly correlated with the increase in lactate concentration during heavy constant work rate exercise, led us to investigate the role of H+ from lactic acid in facilitating oxyhemoglobin (O2Hb) dissociation. We measured femoral venous PO2, O2Hb saturation, pH, PCO2, lactate, and standard HCO3- during increasing work rate and two constant work rate cycle ergometer exercise tests [below and above the lactic acidosis threshold (LAT)] in two groups of five healthy subjects. Mean end-exercise femoral vein blood and VO2 values for the below- and above-LAT square waves and the increasing work rate protocol were, respectively, PO2 of 19.8 +/- 2.1 (SD), 18.8 +/- 4.7, and 19.8 +/- 3.3 Torr; O2 saturation of 22.5 +/- 4.1, 13.8 +/- 4.2, and 18.5 +/- 6.3%; pH of 7.26 +/- 0.01, 7.02 +/- 0.11, and 7.09 +/- 0.07; lactate of 1.9 +/- 0.9, 11.0 +/- 3.8, and 8.3 +/- 2.9 mmol/l; and VO2 of 1.77 +/- 0.24, 3.36 +/- 0.4, and 3.91 +/- 0.68 l/min. End-exercise femoral vein PO2 did not differ statistically for the three protocols, whereas O2Hb saturation continued to decrease for work rates above LAT. We conclude that decreasing capillary PO2 accounted for most of the O2Hb dissociation during below-LAT exercise and that acidification of muscle capillary blood due to lactic acidosis accounted for virtually all of the O2Hb dissociation above LAT.

Anaerobic threshold alterations caused by endurance training in middle-aged men

1979 ◽  
Vol 46 (6) ◽  
pp. 1039-1046 ◽  
Author(s):  
J. A. Davis ◽  
M. H. Frank ◽  
B. J. Whipp ◽  
K. Wasserman
Keyword(s):  
Endurance Training ◽  
Anaerobic Threshold ◽  
Minute Ventilation ◽  
Correlation Coefficients ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Middle Aged ◽  
Co2 Output ◽  
Before And After ◽  
Cycle Endurance

Nine previously sedentary middle-aged males underwent cycle endurance training 45 min/day for 9 wk with an average attendance of 4.1 days/wk. Seven males served as controls. Before and after the training period, the subjects performed three cycle ergometer tests. Work rate was incremented by 15 W/min, to the limit of the subjects' tolerance, in the first two tests; the third test consisted of contant-load cycling at an O2 uptake (VO2) just below the pretraining anaerobic threshold (AT). After training, the AT increased significantly by 44%, expressed as absolute VO2, and by 15%, expressed relative to VO2 max. Significant increases were also noted in VO2max (25%), maximal minute ventilation (19%), and maximal work rate (28%). The test-retest correlation coefficients for the AT (%VO2max) were 0.91, pre- and posttraining. Training did not alter steady-state VO2 during the submaximal exercise test whereas significant decreases occurred in CO2 output, VE, respiratory quotient, and VE/VO2. No changes occurred in the control subjects during this period. These results demonstrate that the AT is profoundly influenced by endurance training in previously sedentary middle-aged males.

Breathing and upper airway CO2 in reptiles: role of the nasal and vomeronasal systems

1989 ◽  
Vol 256 (1) ◽  
pp. R91-R97
Author(s):  
E. L. Coates ◽  
G. O. Ballam
Keyword(s):  
Ventilatory Response ◽  
Minute Ventilation ◽  
Upper Airway ◽  
Olfactory Nerve ◽  
Pause Duration ◽  
Thamnophis Sirtalis ◽  
Nerve Transection ◽  
Vomeronasal System ◽  
Upper Airways ◽  
Before And After

The ventilatory response of the garter snake, Thamnophis sirtalis, to 2% CO2 delivered to the upper airways (UA) was measured before and after the olfactory or vomeronasal nerves were transected. The UA (nasal cavities and mouth) were isolated from the gas source inspired into the lungs by inserting an endotracheal T tube into the glottis. CO2 was administered to the UA via a head chamber. The primary ventilatory response to UA CO2 was a significant decrease in ventilatory frequency (f) and minute ventilation. The decrease in f was caused by a significant increase in the pause duration. Tidal volume, expiratory duration, and inspiratory duration were not altered with UA CO2. The f response to UA CO2 was abolished with olfactory nerve transection, whereas vomeronasal nerve transection significantly increased the magnitude of the f depression. These results indicate that CO2-sensitive receptors are located in the nasal epithelium and that the olfactory nerves must be intact for the UA CO2 f response to be observed. In addition, the vomeronasal system appears to modulate the ventilatory response to UA CO2.

Effect of inspiratory resistive loading on control of ventilation during progressive exercise

1987 ◽  
Vol 62 (1) ◽  
pp. 134-140 ◽  
Author(s):  
A. D. D'Urzo ◽  
K. R. Chapman ◽  
A. S. Rebuck
Keyword(s):  
Ventilatory Response ◽  
Minute Ventilation ◽  
Work Load ◽  
Cycle Ergometer ◽  
Resistive Load ◽  
Co2 Output ◽  
Exercise Ventilation ◽  
Resistive Loading ◽  
End Tidal ◽  
Arterial O2 Saturation

Eight healthy volunteers performed gradational tests to exhaustion on a mechanically braked cycle ergometer, with and without the addition of an inspiratory resistive load. Mean slopes for linear ventilatory responses during loaded and unloaded exercise [change in minute ventilation per change in CO2 output (delta VE/delta VCO2)] measured below the anaerobic threshold were 24.1 +/- 1.3 (SE) = l/l of CO2 and 26.2 +/- 1.0 l/l of CO2, respectively (P greater than 0.10). During loaded exercise, decrements in VE, tidal volume, respiratory frequency, arterial O2 saturation, and increases in end-tidal CO2 tension were observed only when work loads exceeded 65% of the unloaded maximum. There was a significant correlation between the resting ventilatory response to hypercapnia delta VE/delta PCO2 and the ventilatory response to VCO2 during exercise (delta VE/delta VCO2; r = 0.88; P less than 0.05). The maximal inspiratory pressure generated during loading correlated with CO2 sensitivity at rest (r = 0.91; P less than 0.05) and with exercise ventilation (delta VE/delta VCO2; r = 0.83; P less than 0.05). Although resistive loading did not alter O2 uptake (VO2) or heart rate (HR) as a function of work load, maximal VO2, HR, and exercise tolerance were decreased to 90% of control values. We conclude that a modest inspiratory resistive load reduces maximum exercise capacity and that CO2 responsiveness may play a role in the control of breathing during exercise when airway resistance is artificially increased.

Effect of beta-adrenergic blockade on respiratory and metabolic responses to exercise

1981 ◽  
Vol 51 (4) ◽  
pp. 788-793 ◽  
Author(s):  
O. P. Twentyman ◽  
A. Disley ◽  
H. R. Gribbin ◽  
K. G. Alberti ◽  
A. E. Tattersfield
Keyword(s):  
Venous Blood ◽  
Normal Subjects ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Adrenergic Blockade ◽  
Early Exercise ◽  
Co2 Output ◽  
Initial Reduction ◽  
Progressive Exercise ◽  
Constant Work Rate

The responses to oral propranolol (80 mg) and placebo were compared in normal subjects during three studies on a cycle ergometer (progressive exercise and two 5-min constant work rate studies at 50 and 70% maximum). Heart rate (HR), ventilation (VE), CO2 output (VCO2) and O2 uptake (VO2) were measured in each study and metabolites in venous blood in the 70% study. Propranolol reduced HR in all studies and endurance time during progressive exercise. During constant-work-rate exercise the changes with propranolol depended on time and work rate. At 50% max, VO2, VCO2, and VE were reduced in early exercise but were similar by min 5. At 70% max, VO2 and VCO2 were again lower initially with propranolol but then rose more rapidly. By min 5 VE was greater with propranolol, coinciding with a rapidly rising venous lactate. We interpret the initial reduction in VO2 and VCO2 to reduced cardiac output and muscle perfusion with propranolol. The resulting increase in anaerobic metabolism during heavy exercise would explain the increased VE at min 5. The metabolic data are compatible with glycogen being the predominant muscle fuel.

L-Glutamine Therapy Improves Minute Ventilation of Sickle Cell Anemia Patients.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3783-3783
Author(s):  
Henry R. Macan ◽  
Janos Porszasz ◽  
Hideki Tsurugaya ◽  
Rafael L. Razon ◽  
Han Koh ◽  
...  
Keyword(s):  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Oxygen Delivery ◽  
Minute Ventilation ◽  
Exercise Duration ◽  
Work Rate ◽  
Incremental Test ◽  
Constant Work Rate ◽  
Rate Test ◽  
Exercise Endurance

Abstract We have demonstrated previously that oral L-glutamine administration can improve NAD redox potential in sickle red blood cells (RBC) and decrease the endothelial adhesion rate of sickle RBC. Additionally, preliminary results showed that L-glutamine therapy improved the exercise endurance of sickle cell anemia patients. Following up on this study, minute ventilation and work rate were evaluated. After proper consent, 6 homozygous sickle cell anemia volunteers participated in this two-part study. The first part was incremental work rate testing where the work rate was increased incrementally. The second part was the constant work rate test, in which 80% of the maximum work rate of the incremental test was utilized. Patients were observed for changes in ventilation. These tests were conducted at baseline and after 8 to 12 weeks of therapy with oral L-glutamine at 30 grams a day. There were 6 patients who completed the incremental work rate test and 4 patients who completed the constant work rate test, respectively, at baseline and after treatment. Two of the patients withdrew prior to the completion of the follow-up testing. The results were as follows: On the incremental test, there was an upward trend in peak work rate with an average of 3.5 ± 8.7 watts/min (88.7 ± 25.6 vs. 91.5 ± 21.7; ρ> 0.05). Minute ventilation (VE) showed an average improvement of −4.8 ± 3.9 liters/min (61.2 ± 9.8 vs. 56.4 ± 9.9; ρ value of 0.05). The improved ventilation may be secondary to increased pulmonary blood flow inferring an increased cardiovascular oxygen delivery. On the constant work rate test, there was significant increase in exercise duration with an average of 1.4 ± 0.8 minutes (5.9 ± 1.6 vs. 7.3 ± 1.1; ρ< 0.05). The minute ventilation (VE) showed an average decrease of −11.0 ± 11.6 liters/min (66.5 ± 24.9 vs. 55.5 ± 14.5; ρ> 0.05). This could be indicative of improved oxygen delivery to the exercising musculature despite the absence of a preparatory exercise training program. The data confirm our preliminary report suggesting that L-glutamine therapy improves the exercise endurance of sickle cell anemia patients. Test Mean + SD ρ value Pre Post Paired Δ (two-tailed t-test) Incremental Work Rate Peak Work Rate (watts/min) 88.7 ± 25.6 91.5 ± 21.7 3.5 ± 8.7 0.37 VE (liters/minute) 61.2 ± 9.8 56.4 ± 9.9 −c4.8 ± 3.9 0.05 Constant Work Rate −Duration (minutes) 5.9 ± 1.6 7.3 ± 1.1 1.4 ± 0.8 0.04 −VE (liters/minute) 66.5 ± 24.9 55.5 ± 14.5 −11.0 ± 11.6 0.15

scholarly journals Control of ventilation during exercise in patients with central venous-to-systemic arterial shunts

1988 ◽  
Vol 64 (1) ◽  
pp. 234-242 ◽  
Author(s):  
K. E. Sietsema ◽  
D. M. Cooper ◽  
J. K. Perloff ◽  
J. S. Child ◽  
M. H. Rosove ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Minute Ventilation ◽  
Venous Blood ◽  
Work Rate ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Arterial Circulation ◽  
Arterial Blood ◽  
Constant Work Rate ◽  
End Tidal

The diversion of systemic venous blood into the arterial circulation in patients with intracardiac right-to-left shunts represents a pathophysiological condition in which there are alterations in some of the potential stimuli for the exercise hyperpnea. We therefore studied 18 adult patients with congenital (16) or noncongenital (2) right-to-left shunts and a group of normal control subjects during constant work rate and progressive work rate exercise to assess the effects of these alterations on the dynamics of exercise ventilation and gas exchange. Minute ventilation (VE) was significantly higher in the patients than in the controls, both at rest (10.7 +/- 2.4 vs. 7.5 +/- 1.2 l/min, respectively) and during constant-load exercise (24.9 +/- 4.8 vs. 12.7 +/- 2.61 l/min, respectively). When beginning constant work rate exercise from rest, the ventilatory response of the patients followed a pattern that was distinct from that of the normal subjects. At the onset of exercise, the patients' end-tidal PCO2 decreased, end-tidal PO2 increased, and gas exchange ratio increased, indicating that pulmonary blood was hyperventilated relative to the resting state. However, arterial blood gases, in six patients in which they were measured, revealed that despite the large VE response to exercise, arterial pH and PCO2 were not significantly different from resting values when sampled during the first 2 min of moderate-intensity exercise. Arterial PCO2 changed by an average of only 1.4 Torr after 4.5-6 min of exercise. Thus the exercise-induced alveolar and pulmonary capillary hypocapnia was of an appropriate degree to compensate for the shunting of CO2-rich venous blood into the systemic arterial circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

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