Richard L. Jones

Intra‐pulmonary shunt and pulmonary gas exchange during exercise in humans

In young, healthy people the alveolar–arterial P u2009Ou20092 difference (A‐aDO2) is small at rest, but frequently increases during exercise. Previously, investigators have focused on ventilation/perfusion mismatch and diffusion abnormalities to explain the impairment in gas exchange, as significant physiological intra‐pulmonary shunt has not been found. The aim of this study was to use a non‐gas exchange method to determine if anatomical intra‐pulmonary (I‐P) shunts develop during exercise, and, if so, whether there is a relationship between shunt and increased A‐aDO2. Healthy male participants performed graded upright cycling to 90% while pulmonary arterial (PAP) and pulmonary artery wedge pressures were measured. Blood samples were obtained from the radial artery, cardiac output was calculated by the direct Fick method and I‐P shunt was determined by administering agitated saline during continuous 2‐D echocardiography. A‐aDO2 progressively increased with exercise and was related to (r= 0.86) and PAP (r= 0.75). No evidence of I‐P shunt was found at rest in the upright position; however, 7 of 8 subjects developed I‐P shunts during exercise. In these subjects, point bi‐serial correlations indicated that I‐P shunts were related to the increased A‐aDO2 (r= 0.68), (r= 0.76) and PAP (r= 0.73). During exercise, intra‐pulmonary shunt always occurred when A‐aDO2 exceeded 12 mmHg and was greater than 24 l min−1. These results indicate that anatomical I‐P shunts develop during exercise and we suggest that shunt recruitment may contribute to the widened A‐aDO2 during exercise.

Effects of the self-contained breathing apparatus and fire protective clothing on maximal oxygen uptake

To examine the effects of firefighting personal protective ensemble (PPE) and self-contained breathing apparatus (SCBA) on exercise performance, 12 males completed two randomly ordered, graded exercise treadmill tests (GXTPPE and GXTPT). Maximal oxygen consumption (VO2max) during GXTPPE was 17.3% lower than the GXTPT in regular exercise clothing (43.0 ± 5.7 vs. 52.4 ± 8.5 ml/kg per min, respectively). The lower VO2max during the PPE condition was significantly related (r = 0.81, p < 0.05) to attenuated peak ventilation (142.8 ± 18.0 vs. 167.1 ± 15.6 l/min), which was attributed to a significant reduction in tidal volume (2.6 ± 10.4 vs. 3.2 ± 0.4 l). Breathing frequency at peak exercise was unchanged (55 ± 7 vs. 53 ± 7 breaths/min). The results of this investigation demonstrate that PPE and the SCBA have a negative impact on VO2max. These factors must be considered when evaluating aerobic demands of fire suppression work and the fitness levels of firefighters.

The impact of exercise training intensity on change in physiological function in patients with chronic obstructive pulmonary disease.

Pulmonary rehabilitation incorporating exercise training is an effective method of enhancing physiological function and quality of life for patients with chronic obstructive pulmonary disease (COPD). Despite the traditional belief that exercise is primarily limited by the inability to adequately increase ventilation to meet increased metabolic demands in these patients, significant deficiencies in muscle function, oxygen delivery and cardiac function are observed that contribute to exercise limitation. Because of this multifactorial exercise limitation, defining appropriate exercise training intensities is difficult. The lack of a pure cardiovascular limitation to exercise prohibits the use of training guidelines that are based on cardiovascular factors such as oxygen consumption or heart rate.Current recommendations for exercise training intensity for patients with COPD include exercising at a ‘maximally tolerable level’, at an intensity corresponding with 50% of peak oxygen consumption (VO2peak), or at 60–80% of peak power output obtained on a symptom-limited exercise tolerance test. In general, it appears that higher intensity training elicits greater physiological change than lower intensity training; however, there is no consensus as to the exercise training intensity that elicits the greatest physiological benefit while remaining tolerable to patients.The ‘optimal’ intensity of training likely depends upon the individual goals of each patient. If the goal is to increase the ability to sustain tasks that are currently able to be performed, lower to moderate-intensity training is likely to be sufficient. If the goal of training, however, is to increase the ability to perform tasks that are above the current level of tolerance, higher intensity training is likely to elicit greater performance increases. In order to perform higher intensity exercise, an interval training model is likely required. High-intensity interval training involves significant anaerobic energy utilisation and, therefore, may better mimic the physiological requirements of activities of daily living. Also, high-intensity interval training is tolerable to patients and may, in fact, reduce the degree of dyspnoea and dynamic hyperinflation through a reduced ventilatory demand. Another factor that will determine the optimal intensity of training is the relative contribution of ventilatory limitation to exercise tolerance. If peak exercise tolerance is limited by a patient’s ability to increase ventilation, it is possible that interval training at an intensity higher than peak will elicit greater muscular adaptation than an intensity at or below peak power on an incremental exercise test. More research is required to determine the optimal training intensity for pulmonary rehabilitation patients.

The effect of salbutamol on performance in endurance cyclists

AbstractThe effect of salbutamol (S) on cycling performance was examined in 15 highly trained non-asthmatic male cyclists. A double-blind, randomized cross-over design was used with S or placebo (P) administered using a metered-dose inhaler and a spacer device 20 min before each testing session. The S dose was 400 μg (four puffs), which is twice the normal therapeutic level. Subjects were habituated to all the laboratory procedures in the week prior to actual data collection. The subjects performed four tests under S and P conditions on separate days over 2 weeks. These included measurement of maximal O2 uptaken

Effects of hyperbaric oxygen on recovery from exercise-induced muscle damage in humans.

(dot VO_{2max} )

The Effect of Inspiratory and Expiratory Respiratory Muscle Training in Rowers

n (cycle ergometry) with assessment of pulmonary function before and after, a submaximal (90% of ventilatory threshold) square-wave work transition from a base of unloaded cycling, a 60-s modified Wingate test, and a simulated 20 km time trial. No significant differences were observed in any of the dependent variables related to aerobic endurance or cycling performance between the S and P conditions. These results support other findings that an acute dose (400 μg) of S has no performance-enhancing properties.

Effects of self-contained breathing apparatus on ventricular function during strenuous exercise

The effects of hyperoxia on maximal exercise while breathing from a self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed three graded exercise tests (GXT) for the assessment of maximal oxygen uptake (Vdot;O 2max): two with 20.95 ± 0.28% O2 and the third (GXT40) while breathing hyperoxia (40.64 ± 1.29% O2). No significant differences were found between the two normoxic tests, except for a 16W increase in maximal power output (POmax) in the second trial (GXT21). Compared to GXT21, hyperoxia significantly increased Vdot;O 2max and POmax by 10.0 ± 3.8% and 10.2 ± 7.1%, respectively. This was likely due to an increase in O2 delivery as suggested by the significantly higher oxyhemoglobin saturation. The increase in Vdot;O 2max with hyperoxia was similar to the increase in carbon dioxide production (9.3 ± 6.5%). No other significant differences were found at maximal exercise. However, at the intensity that elicited Vdot;O 2max in GXT21, pulmonary ventilation and SCBA mask pressure were significantly lower during GXT40, suggesting a decrease in the work of breathing. These findings could have significant implications for occupations that involve heavy work with SCBA.

Normal values for the hypercapnic ventilation response : effects of age and the ability to ventilate

ObjectiveTo determine whether hyperbaric oxygen (HBO) therapy could accelerate recovery from exercise-induced muscle damage in humans. DesignPretest–posttest design with random assignment to either a treatment (HBO) or placebo control (sham) group. SettingUniversity of Alberta and Misericordia Hospital, Edmonton. Participants12 healthy male students (24.2 ± 3.2 years) who were unaccustomed to strenuous eccentric exercise of the calf muscles. InterventionsAll subjects performed a strenuous eccentric exercise protocol designed to elicit muscle damage within the right gastrocnemius muscle. Subjects subsequently received either HBO (100% oxygen at 253 kPa [2.5 ATA] for 60 min; n = 6) or sham (atmospheric air at 132 kPa [1.3 ATA] for 60 min; n = 6) treatment conditions. The first treatment was administered 3–4 hours after damage, with a second and third at 24 and 48 hours after the first, respectively. Main Outcome MeasuresDependent variables included peak torque at 0.52 radians/s, peak isometric torque, and muscular endurance using isokinetic dynamometry; muscle cross-sectional area using magnetic resonance imaging; inorganic phosphate levels and T2 relaxation time using 31P and 1H magnetic resonance spectroscopy; pain sensation and unpleasantness using the Descriptor Differential Scale. These variables were assessed at baseline and until day 5 postdamage. ResultsThere was little evidence of a difference in recovery rate between the HBO and sham groups. Faster recovery was observed in the HBO group only for isometric peak torque and pain sensation and unpleasantness. ConclusionsHBO cannot be recommended as an effective method of treatment of this form of muscle injury.