Enhanced recovery of breathing capacity from combined adenosine 2A receptor inhibition and daily acute intermittent hypoxia after chronic cervical spinal injury.

Daily acute intermittent hypoxia (dAIH) improves breathing capacity after C2 spinal hemisection (C2HS) in rats. Since C2HS disrupts spinal serotonergic innervation below the injury, adenosine-dependent mechanisms underlie dAIH-induced functional recovery 2weeks post-injury. We hypothesized that dAIH-induced functional recovery converts from an adenosine-dependent to a serotonin-dependent, adenosine-constrained mechanism with chronic injury. Eight weeks post-C2HS, rats began dAIH (10, 5-min episodes, 10.5% O2; 5-min intervals; 7days) followed by AIH 3× per week (3×wAIH) for 8 additional weeks with/without systemic A2A receptor inhibition (KW6002) on each AIH exposure day. Tidal volume (VT) and bilateral diaphragm (Dia) and T2 external intercostal motor activity were assessed in unanesthetized rats breathing air and during maximum chemoreflex stimulation (MCS: 7% CO2, 10.5% O2). Nine weeks post-C2HS, dAIH increased VT versus time controls (p<0.05), an effect enhanced by KW6002 (p<0.05). dAIH increased bilateral Dia activity (p<0.05), and KW6002 enhanced this effect in contralateral (p<0.05) and ipsilateral Dia activity (p<0.001), but not T2 inspiratory activity. Functional benefits of combined AIH plus systemic A2A receptor inhibition were maintained for 4weeks. Thus, in rats with chronic injuries: 1) dAIH improves VT and bilateral diaphragm activity; 2) VT recovery is enhanced by A2A receptor inhibition; and 3) functional recovery with A2A receptor inhibition and AIH "reminders" last 4weeks. Combined dAIH and A2A receptor inhibition may be a simple, safe, and effective strategy to accelerate/enhance functional recovery of breathing capacity in patients with respiratory impairment from chronic spinal injury.

Impact of acute exposure to air pollution on the cardiorespiratory performance of military firemen.

The objective of the present study was to determine the impact of acute short-term exposure to air pollution on the cardiorespiratory performance of military firemen living and working in the city of Guarujá, São Paulo, Brazil. Twenty-five healthy non-smoking firemen aged 24 to 45 years had about 1 h of exposure to low and high levels of air pollution. The tests consisted of two phases: phase A, in Bertioga, a town with low levels of air pollution, and phase B, in Cubatão, a polluted town, with a 7-day interval between phases. The volunteers remained in the cities (Bertioga/Cubatão) only for the time required to perform the tests. Cumulative load 10 +/- 2 min-long exertion tests were performed on a treadmill, consisting of a 2-min stage at a load of 7 km/h, followed by increasing exertion of 1 km h-1 min-1 until the maximum individual limit. There were statistically significant differences (P < 0.05) in anaerobic threshold (AT) between Cubatão (35.04 +/- 4.91 mL kg-1 min-1) and Bertioga (36.98 +/- 5.62 mL kg-1 min-1; P = 0.01), in the heart rate at AT (AT HR; Cubatão 152.08 +/- 14.86 bpm, Bertioga 157.44 +/- 13.64 bpm; P = 0.001), and in percent maximal oxygen consumption at AT (AT%VO2max; Cubatão 64.56 +/- 6.55%, Bertioga 67.40 +/- 5.35%; P = 0.03). However, there were no differences in VO2max, maximal heart rate or velocity at AT (ATvel) observed in firemen between towns. The acute exposure to pollutants in Cubatão, SP, caused a significant reduction in the performance at submaximal levels of physical exertion.

Impact of acute exposure to air pollution on the cardiorespiratory performance of military firemen

The objective of the present study was to determine the impact of acute short-term exposure to air pollution on the cardiorespiratory performance of military fireman living and working in the city of Guarujá, São Paulo, Brazil. Twenty-five healthy non-smoking firemen aged 24 to 45 years had about 1 h of exposure to low and high levels of air pollution. The tests consisted of two phases: phase A, in Bertioga, a town with low levels of air pollution, and phase B, in Cubatão, a polluted town, with a 7-day interval between phases. The volunteers remained in the cities (Bertioga/Cubatão) only for the time required to perform the tests. Cumulative load 10 ± 2 min-long exertion tests were performed on a treadmill, consisting of a 2-min stage at a load of 7 km/h, followed by increasing exertion of 1 km h-1 min-1 until the maximum individual limit. There were statistically significant differences (P < 0.05) in anaerobic threshold (AT) between Cubatão (35.04 ± 4.91 mL kg-1 min-1) and Bertioga (36.98 ± 5.62 mL kg-1 min-1; P = 0.01), in the heart rate at AT (AT HR; Cubatão 152.08 ± 14.86 bpm, Bertioga 157.44 ± 13.64 bpm; P = 0.001), and in percent maximal oxygen consumption at AT (AT percentVO2max; Cubatão 64.56 ± 6.55 percent, Bertioga 67.40 ± 5.35 percent; P = 0.03). However, there were no differences in VO2max, maximal heart rate or velocity at AT (ATvel) observed in firemen between towns. The acute exposure to pollutants in Cubatão, SP, caused a significant reduction in the performance at submaximal levels of physical exertion.

Effects of almitrine on the ventilatory control, breathing pattern and maximal exercise tolerance in hypoxemic patients with chronic obstructive pulmonary disease.

Almitrine bismesylate improves arterial blood gases in patients with chronic obstructive pulmonary disease (COPD), but side effects such as increase of ventilatory drive and dyspnea have been reported in some studies. We studied 18 COPD patients (mean age = 59.1 years; mean FEV1 = 0.92 1; mean PaO2 = 58.6 mmHg) in a double-blind randomized study using placebo or almitrine 50 mg twice a day by mouth, for 60 days. In contrast to the placebo group, 40% of the patients in the almitrine group presented a significant increase in PaO2 and a decrease in P(A-a)O2 > or = 5 mmHg during submaximal exercise after 60 days of treatment. Ventilatory drive and the breathing pattern were measured at rest and during submaximal exercise. Both groups showed high levels of ventilatory drive and a tachypneic breathing pattern before drug treatment and no modification was found 30 and 60 days after treatment. Metabolic, cardiovascular and ventilatory variables were studied during an incremental to maximum exercise symptom-limited test (cycloergometry). Maximal VO2 ranged from 46 to 52% and heart rate from 76 to 78% in relation to the predicted values. The percent ratio of ventilation at maximal exercise to maximal voluntary ventilation at rest ranged from 86 to 94%. These results show that the reduction of ventilatory capacity was the main factor decreasing the aerobic performance of our COPD patients. Maximal exercise tolerance (VO2 max) did not change after almitrine treatment. Negative factors like an increase in neuromuscular drive did not occur, and positive factors like an increase in PaO2 and oxygen transport had no critical influence on exercise performance in our ventilatory-limited COPD patients.

Effects of gallamine on spontaneous ventilation during general anaesthesia

An investigation was carried out to establish if the intravenous injection of gallamine triethiodide 40mg in an anaesthetized patient breathing spontaneously, was sufficient to depress ventilation as judged by a rise Pa co2. Fifty women undergoing minor gynaecological surgery were divided into two equal groups at random. One group received thiopentone, nitrous oxide, oxygen and trichlorethylene anaesthesia. The other group received in addition gallamine 40 mg. On examination of blood gases, no statistical difference could be demonstrated between the two groups. It was concluded that this practice does not depress spontaneous ventilation.(AU)