Latest News - Part 28
Synchronized Intermittent Mandatory Ventilation With and Without Pressure Support Ventilation in Weaning Patients With COPD From Mechanical Ventilation
The most critical time for patients with chronic obstructive pulmonary disease (COPD) mechanically ventilated for acute respiratory failure (ARF) is the weaning period. Asthma inhalers online Link Patients with hyperinflation and/or bad nutritional status2 are obviously exposed to difficulties in recovering sustained spontaneous breathing. Indeed, patients with COPD often do not tolerate discontinuation of mechanical ventilation (MV) due to the combination of a number of factors. During ARF, the increase in both inspiratory and expiratory flow resistances results in an increased mechanical load for the respiratory muscles, and leads to intrinsic positive end-expiratory pressure (PEEP) which acts as an inspiratory threshold load. Concurrently, the hyperinflation induces a flattening of the diaphragm which then operates on a less efficient portion of its force-length curve. So, COPD patients in ARF have to cope with an increased work of breathing that has to be overcome by respiratory muscles which are in a disadvantageous position. Furthermore, MV itself may aggravate intrinsic PEEP, may increase the mechanical load by the resistances of endotracheal tube and respirator cricuitry, and can be so considered as an additional burden for the respiratory muscles.
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Persistence of Airway Obstruction and Hyperresponsiveness in Subjects With Asthma Remission: Comment
Medication may influence symptoms and airway responsiveness. It has been shown that prolonged use of inhaled steroids may reduce airway responsiveness and “induce” remission in some subjects. In our study, only two subjects “in remission” previously took inhaled steroids or prednisone, most subjects using a /82-agonist on demand, in some of them in association with a theophylline. Some subjects took no antiasthma medication.
There was no significant correlation between PC20 and duration of asthma or of remission. This suggests that it is not necessarily the duration of asthma that determines the persistence of airflow obstruction or airway hyperresponsiveness. However, in the study of Chan-Yeung33 on occupational asthma to red cedar, the longer the duration of symptoms and the more intense the antigenic contact, the less likely the remission. Subjects who became asymptomatic following withdrawal from the sensitizing agent had at the time of diagnosis a PC20 and an FEVi much higher than those that remained symptomatic, even after cessation of work Link http://birthcontroltab.com. They also had an early diagnostic of occupational asthma and a shorter exposure period to a sensitizing agent.
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Persistence of Airway Obstruction and Hyperresponsiveness in Subjects With Asthma Remission: Conclusion
More than 50 percent of subjects with mild increases in airway response to histamine denied symptoms suggestive of asthma. This is similar to what has been reported by Woolcock et al28 showing that 32 percent of adults with airway hyperresponsiveness never had symptoms suggestive of asthma. This suggests that for a similar degree of airway responsiveness, there may be marked differences in perception of asthma symptoms from one subject to another, although why these differences occur is still to be documented.
Different factors may be involved in the reduction of severity of asthma and “virtual” or true remissions. First, “remissions” of asthma were almost exclusively observed in atopic subjects (28 of our 30 subjects), suggesting that they are possibly in relation with environmental changes such as reduced exposure to relevant allergens or a reduction in immunologic response. This is supported by the observation that most of these subjects avoided exposure to antigens to which they were sensitized. Canadian family pharmacy Link Most of our subjects had mild hyperresponsiveness and little variations of expiratory flow rates (mean daily variation <10 percent). It is possible that they did not encounter in their daily activities or avoided sufficiently triggers that could have caused symptoms.
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Persistence of Airway Obstruction and Hyperresponsiveness in Subjects With Asthma Remission: Discussion
In our study, asthma remission occurred between ages 11 and 20 years in most subjects but remissions were also observed after the age of 40 years. Remissions in asthmatic children have been well studied but little is known, however, of asthma remissions in adults. Spontaneous remissions of asthma have been reported to occur in 30 to 70 percent of subjects, mainly at adolescence. Martin et al also showed that children who had minor wheezing in childhood and were wheeze free for at least 3 years had normal pulmonary function, although 60 percent of these had an abnormal bronchial response to inhaled histamine more canadian neighbor pharmacy. Our results are in keeping with these observations as we observed the persistence of an increased response to methacholine in 63 percent of “ex-asthmatics.”
Radford et al compared the level of airway responsiveness between former and present asthmatic children. They reported that former asthmatics had persistence of airway hyperresponsiveness over time, compared with currently symptomatic asthmatics, but to a lesser degree. Gerritsen et al showed that 43 percent of 101 adults with asthma in childhood still had asthma symptoms, although the number of subjects with a PD10 histamine <16 mg/ ml went from 101 children to 29 adults. Of the 43 subjects with persistent symptoms, 59 percent had a positive response to histamine, compared with 7 percent of those without symptoms.
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Persistence of Airway Obstruction and Hyperresponsiveness in Subjects With Asthma Remission: Respiratory Symptoms
On initial questionnaire, 29 asthmatics “in remission” (15 controls) described occasional respiratory symptoms following either allergen exposure (n=15, 6 controls), viral infections, or exposure to different conditions or stimuli (humidity, cold air, smoke, heavy exercise).
During the 14-day period of PEFR measurement and symptoms recordings, 12 “ex-asthmatics” (one control) had symptoms such as either dyspnea, cough, wheezing, or chest tightness. In four, these followed exposure to an allergen to which they were sensitized. Of these 12 subjects, 6 had a PC20 <8 mg/ ml, 2 between 8 and 20 mg/ml, 3 >20 mg/ml, and one reacted to saline solution. The control subject, whose PC20 was 54.5 mg/ml, had cough and wheezing; these symptoms were related to recent exposure to tree pollens.
Correlation Between Perception of Bronchoconstriction and Airway Responsiveness or Airflow Obstruction
During methacholine inhalation tests, dyspnea and the perception of a fall in FEVi were evaluated according to a modified Borg scale (0 to 10). Canadian health care mall More info In the 20 asthmatics “in remission” with a PC20 <128 mg/ ml, mean Borg score at 20 percent fall in FEVi was 1.63 ±0.40 for dyspnea and 1.78 ±0.30 for perception of bronchoconstriction (controls [n=19]: dyspnea: 1.05 ±0.25, perception of bronchoconstriction: 1.61 ±0.26). Dyspnea and bronchoconstriction were perceived similarly by both groups of subjects. Perception of dyspnea was significantly correlated to the level of airway responsiveness in the control group only (rs=0.546, p=0.045). There was no significant correlation between the perception of either dyspnea or bronchoconstriction and baseline FEVi.
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Persistence of Airway Obstruction and Hyperresponsiveness in Subjects With Asthma Remission: Response to Bronchodilators
In asthmatics “in remission,” improvement in FEVi following bronchodilator was small although larger than in controls, with a percent change from baseline values ranging from —1.1 to 14.1 percent; mean, 5.7 ±0.8 percent (controls: —4.4 to 10.5 percent; mean, 2.5 ±0.6 percent; p=0.004). After 200 fig of inhaled albuterol, FEF25-75% increased 2.2 to 50 percent from baseline; mean, 17.3 ±2.6 percent) (controls: —4.3 to 39.8 percent; mean, 13.5±2.3 percent; NS). The increase in FEF25-75% was the sole parameter that was statistically different when the five hyperreactive control subjects were either kept in the control group or replaced: mean response with hyperreactive subjects replaced was 11.5 ±1.9, p=0.024).
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Persistence of Airway Obstruction and Hyperresponsiveness in Subjects With Asthma Remission: Results
Results were similar whether the five hyperreactive subjects were replaced or not, except for bronchodilator response, as commented in this section. Therefore, the results presented are those of the 30 ex-asthmatics in comparison to the 30 initial controls, including these 5 hyperreactive subjects.
Our subjects reported no symptom attributed to asthma or any need for antiasthma medication for periods of 2 to 25 years (mean [±SEM], 9.6 ±1.3). Age at the onset of asthma was from 0 to 33 years (mean, 10.5 ±1.8) and duration of symptomatic asthma was from 2 to 33 years (mean, 12.4±1.7). Remission of asthma had occurred in childhood in 12 subjects and followed cessation of a specific antigenic exposure to house pets in 9 subjects and after moving to another country in 2 others. Ten exasthmatics and two controls had past immunotherapy. Eleven asthmatics “in remission and 10 controls had a family history of asthma and, respectively, 16 and 21 subjects had a family history of atopy (Table 1).
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