Tuberculosis today--the ongoing challenge.
Explore the source record for details and available documents.
AIDS-Related Opportunistic Infections↗
Biomedical subjects
M A Avendano
Publications and source records attributed to M A Avendano.
Effect of external chest wall oscillation on gas exchange in healthy subjects.
Effective gas exchange can be maintained in animals without the need for endotracheal intubation using external chest wall oscillation (ECWO). The clinical application of this technique has been limited by equipment which was either impractical or uncomfortable. We evaluated a prototype of a new oscillator in which an oscillatory profile of negative and positive pressure was imposed on a negative baseline pressure within a cuirass. In seven healthy subjects, we identified an oscillatory cuirass pressure that could effectively ventilate but would not result in severe hypocapnia over 5 min. We then measured the influence of changing the frequency of oscillation (fo) on PaCO2 and spontaneous ventilation. Lastly, we evaluated the capability of this prototype to achieve targeted changes in chamber pressure. Subjects were ventilated with an inspiratory chamber pressure of -20 +/- 4 cm H2O, an expiratory chamber pressure of 5 cm H2O and an inspiratory-expiratory ratio of 1:1 at 9 oscillatory frequencies (fo: 1 to 5 Hz at 0.5-Hz increments). Each subject was ventilated for 5 min with consecutive periods of ECWO being separated from each other by 10 min of unassisted breathing. Oscillatory tidal volume (Vo) was sampled and PaCO2 was determined from the expired carbon dioxide concentration (FECO2) measured at the mouth. The change in PaCO2 (delta PaCO2) was the difference in PaCO2 immediately before and after ECWO. We found that delta PaCO2 and Vo were inversely related to fo. At 1 Hz the delta PaCO2 was -13 +/- 1 mm Hg and Vo was 344 +/- 34 mL in the absence of spontaneous breathing (fb = 0). At 3 Hz and above, at the chamber pressures used, the delta PaCO2 was small (-1 to -2 mm Hg) and the Vo was less than the predicted dead space. Subjects breathed spontaneously but at a frequency below that of their resting fb. With this prototype, chamber pressure changes up to 30 cm H2O could be accurately achieved at 1, 2.5, and 4 Hz. In conclusion, ECWO can provide effective ventilation among healthy adults in the presence or absence of spontaneous breathing, and further studies are warranted to explore its effectiveness in a variety of clinical circumstances.
Adult↗
Randomised controlled trial of respiratory rehabilitation.
Disability associated with chronic obstructive pulmonary disease has led to the development of rehabilitation programmes that aim to increase exercise tolerance and improve quality of life. Many reports of the benefits of rehabilitation have been from uncontrolled trials and unsupervised programmes. In view of the commitment asked of patients, their families, and health-care professionals, rehabilitation should be justified by a demonstration of sustained improvement over conventional treatment. We undertook a prospective randomised controlled trial of respiratory rehabilitation in 89 subjects (44 men, 45 women) aged 66 (SD 7) years with severe but stable chronic obstructive pulmonary disease who received rehabilitation or conventional community care. The treatment group were rehabilitated as inpatients for 8 weeks and supervised as outpatients for 16 weeks. Primary outcome measures of exercise tolerance and quality of life were made at baseline and repeated at 12, 18, and 24 weeks. The difference between baseline and last follow-up was significant for 6 min walk distance (37.9 m [95% CI 10.8-65.0], p = 0.0067) and submaximal cycle time (4.7 min [2.1-7.3]). There were also significant differences in questionnaire assessment of dyspnoea (p = 0.0061), emotional function (p = 0.0150), mastery (p = 0.0002), and dyspnoea index (p = 0.0053). Improvements in exercise tolerance and quality of life can be achieved and sustained for 6 months in patients undergoing respiratory rehabilitation compared with those receiving conventional care.
Aged↗
The ventilatory response to arm elevation of patients with chronic obstructive pulmonary disease.
Although arm activity is poorly tolerated by patients with COPD, the ventilatory response to arm elevation alone is not well understood. We therefore studied the ventilatory response to arm elevation using a customized arm support sling to eliminate the effect of an increase in metabolic activity that might be attributable to independent arm elevation and used leg exercise to increase metabolic activity. During arm elevation at rest, there was a significant decrease in vital capacity (180 ml) and a small decrease in functional residual capacity (120 ml) as measured by body plethysmography. Minute ventilation was unchanged. When supported arm elevation (SAE) was compared with the control arm position (CAP), minute ventilation was unchanged although the pattern of breathing became more rapid and shallow (mean +/- SD, SAE vs CAP: fb = 17.9 +/- 5.3 vs 16.2 +/- 4.8 breaths.min-1; VT = 533 +/- 126 vs 579 +/- 142 ml; p < 0.05). During steady-state leg exercise, the increase in VO2, VCO2 and VE did not differ between SAE and CAP; however, both fb and VT changed toward a more rapid, shallow pattern of breathing (SAE vs CAP: fb = 24.3 +/- 3.0 vs 22.8 +/- 3.5 breaths.min-1; VT = 990 +/- 293 vs 1,081 +/- 309 ml; p < 0.05). During unsupported arm elevation VO2, VCO2, and VE, and fb were significantly greater than during the CAP. Approaches that train arm muscles and strategies that either support arm muscles or allow for frequent rests during upper arm activity may improve the endurance and the quality of life for COPD patients.
Aged↗
Respiratory function during wakefulness and sleep among survivors of respiratory and non-respiratory poliomyelitis.
The purpose of this study was to determine whether there is a difference in respiratory mechanics and gas exchange between polio survivors and healthy, age-matched controls during wakefulness and sleep. Polio survivors were divided into four groups. The first group included those who had evidence of respiratory muscle involvement originally (PRM) and the second group included those who had bulbar muscle involvement originally (PBM). The third and fourth groups had only limb involvement originally but were separated by absence (PSL) or presence of a scoliosis (PSS) at the time of their evaluation. Each subject completed baseline and one year follow-up measurements of lung volumes, diffusion, flow rates, respiratory muscle strength, central and peripheral chemoreflexes and arterial blood gases. Sleep measurements included a full respiratory polysomnographic study. Fifty polio survivors and 13 controls completed the study. The PRM and PSS groups had an elevated arterial carbon dioxide tension (PaCO2) (mean +/- SE 6.0 +/- 0.4 and 6.0 +/- 0.3 kPa, respectively), reduced vital capacity (2.8 +/- 0.3 and 2.9 +/- 0.3 l, respectively), reduced maximal inspiratory pressure (-5.9 +/- 0.7 and -5.4 +/- 0.8 kPa, respectively) and reduced maximal expiratory pressure (9.8 +/- 1.1 and 9.1 +/- 1.2 kPa, respectively), when compared with non-polio controls. During sleep PRM and PSS groups experienced a higher PaCO2 (6.5 +/- 0.5 and 6.7 +/- 0.4 kPa, respectively) and a lower arterial oxygen saturation (SaO2) (89 +/- 4 and 86 +/- 3%, respectively). There were no differences among groups for diffusion, flow rates and chemoreflexes. All other polio survivors showed essentially normal respiratory function.(ABSTRACT TRUNCATED AT 250 WORDS)
Female↗
Influence of noninvasive positive pressure ventilation on inspiratory muscles.
Intermittent positive pressure ventilation reduces inspiratory muscle electromyographic activity among patients with restrictive ventilatory failure. It has therefore been suggested that the reduction of energy expenditure at night could result in improved inspiratory muscle function during the day. Reported successes with nocturnal ventilation have not included measurements of inspiratory muscle endurance. We therefore electively ventilated six (five female, one male) patients (mean +/- SD) aged 36 +/- 13 years in whom respiratory failure (room air PaCO2, 60 +/- 13 mm Hg; PaO2, 44 +/- 11 mm Hg; SaO2, 75 +/- 12 percent) was consequent on restrictive ventilatory disease (vital capacity, 25 +/- 7 percent predicted; FEV1/FVC, 81 +/- 12 percent; total lung capacity, 40 +/- 5 percent predicted; MIPRV -42 +/- 10 cm H2O; MEP, 81 +/- 28 cm H2O). Positive pressure ventilation was administered with a customized closely fitting nasal mask attached to a volume-cycled pressure-limited ventilator. Full respiratory polysomnographic measurements as well as arterial blood gases, pulmonary function, distance walked in six minutes, and inspiratory muscle endurance were measured at baseline and after 3 and 14 months of ventilation. Ventilation improved saturation (baseline on O2; SWS 87 +/- 10, REM 79 +/- 14, ventilator on R/A; SWS 90 +/- 6, REM 89 +/- 5 percent) and transcutaneous Pco2 (baseline on O2; SWS 85 +/- 26, REM 94 +/- 39, ventilator on R/A; SWS 53 +/- 9, REM 58 +/- 9 mm Hg). During ventilation, the quantity and distribution of sleep was similar to that observed prior to ventilation. Daytime gas exchange improved as did the six-minute walking test (initial test = 429 +/- 120 m, three months after ventilation = 567 +/- 121 m), both of these improvements being sustained at 14 months. Inspiratory muscle endurance measured using a pressure threshold load (mean mouth pressure = 45 percent MIPRV) improved from 7.1 +/- 3.4 minutes at baseline to 14.8 +/- 7.6 minutes at 3 months, an improvement sustained at 14 months. There was no change in measured lung volumes or respiratory muscle strength. We conclude that the improvement in nocturnal gas exchange, daytime functioning, and arterial blood gases resulting from nocturnal positive pressure ventilation is associated with an increase in inspiratory muscle endurance sustained at 14 months.
Adult↗
Intermittent positive-pressure ventilation via a nasal mask in patients with restrictive ventilatory failure.
Explore the source record for details and available documents.
Adult↗
Effect of caffeine on ventilatory responses to hypercapnia, hypoxia, and exercise in humans.
The effect of oral caffeine on resting ventilation (VE), ventilatory responsiveness to progressive hyperoxic hypercapnia (HCVR), isocapnic hypoxia (HVR), and moderate exercise (EVR) below the anaerobic threshold (AT) was examined in seven healthy adults. Ventilatory responses were measured under three conditions: control (C) and after ingestion of either 650 mg caffeine (CF) or placebo (P) in a double-blind randomized manner. None of the physiological variables of interest differed significantly for C and P conditions (P greater than 0.05). Caffeine levels during HCVR, HVR, and EVR were 69.5 +/- 11.8, 67.8 +/- 10.8, and 67.8 +/- 10.9 (SD) mumol/l, respectively (P greater than 0.05). Metabolic rate at rest and during exercise was significantly elevated during CF compared with P. An increase in VE from 7.4 +/- 2.5 (P) to 10.5 +/- 2.1 l/min (CF) (P less than 0.05) was associated with a decrease in end-tidal PCO2 from 39.1 +/- 2.7 (P) to 35.1 +/- 1.3 Torr (CF) (P less than 0.05). Caffeine increased the HCVR, HVR, and EVR slopes (mean increase: 28 +/- 8, 135 +/- 28, 14 +/- 5%, respectively) compared with P; P less than 0.05 for each response. Increases in resting ventilation, HCVR, and HVR slopes were associated with increases in tidal volume (VT), whereas the increase in EVR slope was accompanied by increases in both VT and respiratory frequency. Our results indicate that caffeine increases VE and chemosensitivity to CO2 inhalation, hypoxia, and CO2 production during exercise below the AT.
Administration, Oral↗
Applicability of a threshold loading device for inspiratory muscle testing and training in patients with COPD.
We evaluated application of a Pth device for testing inspiratory muscle endurance among patients with severe but stable COPD. Endurance time in five patients was reproducible. Magnitude of variability was +/- 1.26 minutes with a range of +/- 0.19 to +/- 2.28 minutes. Eleven inpatients completed inspiratory muscle training twice daily for four weeks in addition to their usual program of respiratory rehabilitation. The mean age of our experimental cohort was 65 years; FEV1, 33 +/- 12 percent predicted; and Dsb, 42 +/- 7 percent predicted. Baseline measurements showed no significant differences in pulmonary function, exercise tolerance, inspiratory muscle strength or inspiratory muscle endurance between control and study groups. Following training, the study group significantly improved inspiratory muscle endurance as evidenced by an increase in endurance time while breathing against the same absolute external Pth load used during baseline assessments. There were no associated changes in lung mechanics, muscle strength or exercise tolerance.
Aged↗