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PubMed2006

The effect of breathing an ambient low-density, hyperoxic gas on the perceived effort of breathing and maximal performance of exercise in well-trained athletes.

BACKGROUND: The role of the perception of breathing effort in the regulation of performance of maximal exercise remains unclear. AIMS: To determine whether the perceived effort of ventilation is altered through substituting a less dense gas for normal ambient air and whether this substitution affects performance of maximal incremental exercise in trained athletes. METHODS: Eight highly trained cyclists (mean SD) maximal oxygen consumption (VO(2)max) = 69.9 (7.9) (mlO(2)/kg/min) performed two randomised maximal tests in a hyperbaric chamber breathing ambient air composed of either 35% O(2)/65% N(2) (nitrox) or 35% O(2)/65% He (heliox). A ramp protocol was used in which power output was incremented at 0.5 W/s. The trials were separated by at least 48 h. The perceived effort of breathing was obtained via Borg Category Ratio Scales at 3-min intervals and at fatigue. Oxygen consumption (VO(2)) and minute ventilation (V(E)) were monitored continuously. RESULTS: Breathing heliox did not change the sensation of dyspnoea: there were no differences between trials for the Borg scales at any time point. Exercise performance was not different between the nitrox and heliox trials (peak power output = 451 (58) and 453 (56) W), nor was VO(2)max (4.96 (0.61) and 4.88 (0.65) l/min) or maximal V(E) (157 (24) and 163 (22) l/min). Between-trial variability in peak power output was less than either VO(2)max or maximal V(E). CONCLUSION: Breathing a less dense gas does not improve maximal performance of exercise or reduce the perception of breathing effort in highly trained athletes, although an attenuated submaximal tidal volume and V(E) with a concomitant reduction in VO(2) suggests an improved gas exchange and reduced O(2) cost of ventilation when breathing heliox.

Adult↗
PubMedDate not supplied

[Metabolism during exercise in young men breathing 4% CO2 (author's transl)].

Fourteen young men (on the average 25 years), well trained (maximal oxygen consumption, VO2 max., between 2.7 to 3.5 1) have been studied at two different levels of exercise: 90 and 140 watts (about 40 and 70% of VO2 max.) in chamber, where the atmosphere was regulated. The subjects performed the exercise after a sojourn of six hours in the chamber, at the same level, either in air or in hypercapnic conditions (FICO2: 0.04; FIO2: 0.21); the order of the exercise tests was determined at random. The rise of total ventilation (VE) during exercise in CO2 atmosphere was particularly related to the increased tidal volume (VT). In spite of the larger increase of VE in hypercapnia, CO2 output (VCO2) and respiratory quotient (R) were lower while PaCO2 was elevated (48 at rest and 54 mmHg during exercise). Oxygen consumption during exercise was the same in both conditions. Values of arterial lactic acid concentration were not different at 90 watts level. On the contrary, at the level of 140 watts, the lactic acid concentration was significantly lower in CO2 atmosphere. The well known changes during exercise of other electrolytes (rise of Na+, K+ and total Ca) was similar in air and in CO2. Only the inorganic phosphorus was higher in CO2 atmosphere at 140 watts.

Adult↗
PubMed1992

Effects of impaired lung function and pulmonary regurgitation on maximal exercise capacity in patients with repaired tetralogy of Fallot.

Long-term haemodynamic results and exercise capacity were studied in 34 patients with tetralogy of Fallot (24 men and 10 women) repaired 10.0 +/- 4.9 (mean +/- SD) years previously and compared to 34 healthy matched controls. All subjects were studied by resting spirometry, echocardiography and a symptom limited treadmill exercise test (modified Bruce protocol). The maximal oxygen consumption was 38.2 +/- 8.0 ml.kg-1.min-1 in patients and 48.1 +/- 8.1 ml.kg-1.min-1 in the control group (P < 0.001). Reduced maximal oxygen consumption was found in patients with low vital capacity (VC) and pulmonary regurgitation (PR). The ventilatory anaerobic threshold (VAT) was 23.8 +/- 0.6 ml.kg-1.min-1 and 29.9 +/- 0.6 ml.kg-1.min-1 in patients and controls, respectively (P < 0.001). VC was 3.4 +/- 1.21 in patients and 4.0 +/- 1.31 in controls (P < 0.02). In the patients, maximal ventilation was reduced and at submaximal exercise, the breathing frequency increased. Heart rates during exercise were similar in patients and controls. Tricuspid regurgitation (TR) was detected in 20 patients (58.8%); however, the exercise capacity was not reduced. Thus, impaired exercise capacity in tetralogy of Fallot is partly due to reduced resting lung function, pulmonary regurgitation and low ventilatory anaerobic threshold.

Adolescent↗
PubMed1991

Lack of bronchoconstrictor response to sulfuric acid aerosols and fogs.

Sulfuric acid (H2SO4) is the most common acid air pollutant in the United States and is thought to have adverse respiratory effects. Sulfuric acid exists in polluted air as a dissolved solute in both small (haze) and large (fog) particles. Previous work in our laboratory has failed to demonstrate bronchoconstriction after near ambient, large-particle H2SO4 exposure in subjects with asthma. However, other investigators have found slight but significant changes in lung function following inhalation of small-particle or small-particle, low-relative-humidity (RH) H2SO4 aerosols, leading us to hypothesize that particle size and/or RH may be important variables in acid aerosol exposure. We initially studied the effects of resting inhalation of large-particle (volume median diameter, VMD, approximately equal to 6 microns) and small-particle (VMD approximately equal to 0.4 microns) aerosols with an H2SO4 concentration of 3 mg/m3 through a mouthpiece and found no effect on specific airway resistance (SRaw) or symptom scores. In a second mouthpiece study designed to compare high-RH (100%), large-particle (VMD approximately equal to 6 microns) and low-RH (less than 10%), small-particle (VMD approximately equal to 0.3 microns) aerosols with an H2SO4 concentration of 3 mg/m3, we again found no effect of either aerosol. We then examined the effects of small-particle aerosols inhaled in dry air during moderate exercise. Although breathing low-RH air during exercise provoked increases in SRaw in almost all subjects, this could not be attributed to H2SO4 since low-RH saline aerosol produced a similar result.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

A portable oxygen system corrects hypoxemia without significantly increasing metabolic demands.

Some patients with chronic cor pulmonale have hypoxemia only during normal daily activity. This can be corrected by portable oxygen. Whether or not the weight of the apparatus (4.2 kg) adds an additional metabolic demand of sufficient magnitude to cancel or outweigh the advantages of portable oxygen is the subject of this report in 6 patients with chronic obstructive pulmonary disease and 2 with kyphoscoliosis. All received standardized treadmill exercise while breathing room air, and the same exercise with a portable liquid oxygen system sitting on the floor or carried by the patients. The additional load created only a 6.7% increase in CO2 production and did not reverse the supplemental oxygen benefit to arterial oxygen saturation under the experimental conditions of the study.

Adult↗
PubMed2002

[Dynamic analysis of airway temperature in dogs breathing cold air].

Exercise in cold, dry air induces bronchoconstriction. However, the time course of airway cooling during the breathing of cold air has not been investigated. In this study in dogs, the temperatures of tracheal gas and the tracheal wall were measured continuously while the animal was breathing cold air at approximately 4.5 degrees C. The temperature of the tracheal gas decreased during the inspiratory phase, increase slightly early in the expiratory phase, and then decreased to the level at end-expiration. The lowest temperature of the tracheal gas decreased significantly, from 29.7 +/- 2.4 degrees C (mean +/- SD) to 25.7 +/- 2.8 degrees C. The highest temperature also changed significantly, but the decrease was less than 1 degree C. The lowest temperature of the tracheal wall decreased from 31.1 +/- 2.6 degrees C to 30.5 +/- 2.5 degrees C during cold-air breathing, but the difference was not significant. When a dog inspired deeply during a cough, the temperature of tracheal gas did not decrease linearly with the progression of inspiration. However, the decrease in the tracheal wall temperature was almost directly proportional to inspiratory volume. We concluded that both the tracheal gas and the tracheal wall temperatures were resistant to cooling with cold-air breathing. It remains uncertain whether rapid, deep breathing during exercise decreased the tracheal wall temperature.

Animals↗