Category - Part 2
Influence of Two Different Interfaces for Noninvasive Ventilation Compared to Invasive Ventilation on the Mechanical Properties and Performance of a Respiratory System
Noninvasive ventilation (NIV) is increasingly used ’ in the treatment of acute and chronic respiratory failure and during weaning from invasive ventilation. NIV has been applied in patients with acute hypoxemic respiratory failure, severe cardiogenic pulmonary edema, or acute exacerbation of COPD in order to decrease the need and the complications of endotracheal intubation. other
Noninvasive respiratory support can be applied either as continuous positive airway pressure (CPAP) alone or as NIV with inspiratory pressure support (NPSV) by means of a nasal or face mask. Problems with the widely used face masks result partially from air leakage,- discomfort of the patient, and pressure-related ulcerations of the nose.’ These problems may limit the duration of use and account for a large proportion of NIV failures. In an attempt to improve NIV tolerance, a helmet was developed that has been successfully used in different clinical situ-ations.”
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The Lack of Effect of Routine Magnesium Administration on Respiratory Function in Mechanically Ventilated Patients: Finally
The role of worsening diaphragmatic weakness as an acute cause of failure to wean from mechanical ventilation is not well defined. Several reviews have concluded that inspiratory muscle weakness may predispose to acute respiratory failure or complicate weaning from mechanical ventilation. The corollary of this would be that treatment aimed at improving respiratory muscle strength should help to hasten weaning from mechanical ventilation. We did not specifically test whether magnesium infusion would shorten the time to successful weaning but rather tested whether magnesium infusion improved respiratory muscle performance. We did, however, find that those patients who increased VC most following magnesium infusion (ie, change in VC greater than 0) tended to be more rapidly weaned from mechanical ventilation (5 ±2 days) compared with those patients who did not demonstrate an increase in VC (9 ±8 days). This, however, may merely reflect the tautology that patients wean when they improve.
The Lack of Effect of Routine Magnesium Administration on Respiratory Function in Mechanically Ventilated Patients: Conclusion
The unknown extent of carryover of the effects of magnesium, therefore, limited the application of the crossover design in our data analysis. We therefore only analyzed our results from the period before infusion to that immediately following infusion of magnesium. Using this analysis, if we reject the hypothesis of a subgroup of patients and accept the normal distribution for Pimax and VC, the p-error in rejecting an effect of treatment can be calculated. Assuming a positive treatment effect of 30 percent and a onetailed a of 0.05, the P-error for VC and Pimax were 0.09 and 0.04, respectively. Thus, we are confident that our study did not reject the presence of a true magnesium effect and that other causes of respiratory muscle weakness played a more prominent role. canadian pharmacy generic viagra
As a group, our patients suffered from respiratory muscle weakness as demonstrated by their baseline values of inspiratory and expiratory muscle strength. Their mean values of Pimax and PEmax were similar to those described by Rochester in patients suffering from nutritional and nonnutritional myopathies. Along with the respiratory muscle weakness, those patients also demonstrated a restrictive pattern on lung function testing. Our subjects were similar in having reduced VCs along with reductions in Pimax and PEmax. We therefore reasoned that if magnesium did improve respiratory muscle strength, there should also be concomitant increases in VC. We did not detect a subgroup with changes in VC consistent with improved respiratory muscle strength.
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The Lack of Effect of Routine Magnesium Administration on Respiratory Function in Mechanically Ventilated Patients: Discussion
Molloy and associates had evaluated the effects of hypomagnesemia on respiratory muscle strength in 11 patients admitted to the hospital for treatment of alcohol withdrawal and in 6 patients with chronic obstructive pulmonary disease. They found that infusion of 6 g of magnesium increased PEmax by 24 percent and Pimax by 46 percent. Fiaccadori and associates studied the correlation between muscle magnesium levels and serum magnesium levels in patients with chronic obstructive pulmonary disease admitted to their ICU and found that serum magnesium was a poor indicator of tissue magnesium levels. They concluded that 47 percent of their patients with normal serum magnesium levels had evidence of tissue magnesium deficiency and therefore measuring serum magnesium was not useful to detect tissue magnesium deficiency. Since the routine measurement of serum magnesium is not a sensitive method of detecting tissue magnesium deficiency, we decided to test whether the routine infusion of magnesium to ventilated patients with respiratory failure might improve respiratory function. The time course of action of magnesium in the ICU setting has not been fully described. Aikawa and associates have previously studied the kinetics of magnesium distribution in normal subjects and in patients with diabetes or hepatic disease. They found in both normal subjects and patients that infused magnesium exchanged slowly between plasma and muscle requiring greater than 18 h to begin to equilibrate. We therefore decided that the most conservative approach to analyze our data would be to compare only the values obtained immediately following magnesium infusion with those preceding the infusion in order to assess whether the magnesium infusion had any effects. canadianneighborpharmacy.com
The Lack of Effect of Routine Magnesium Administration on Respiratory Function in Mechanically Ventilated Patients: Results
We completed 21 separate studies on a total of 20 patients admitted to our ICU. One patient was included twice for two separate episodes of respiratory failure. The average age was 59 years (range, 22 to 84 years) and there were 14 men and 6 women. The admitting diagnoses to ICU were as follows: eight chronic obstructive pulmonary disease in exacerbation, four postoperative (bowel obstruction, motor vehicle accident, coronary artery bypass, and biliary peritonitis), three pneumonia, two sepsis, and one each of the myeloblastic leukemia, idiopathic pulmonary fibrosis, tuberculosis, and squamous cell carcinoma. We noted that 8 patients had received aminoglycosides, 12 had received diuretics, 3 had a history of diabetes, and 1 had a history of alcohol abuse. Of these, four patients had at least two risk factors (aminoglycosides plus diuretics) with one of the four also abusing alcohol. Table 1 shows the values of electrolytes in the patients receiving magnesium on day 1 and day 2. There was a transient elevation of serum magnesium level following magnesium infusion and this returned to baseline values within 28 h following the infusion. There were other significant differences in any other values of biochemical variables over the course of the study. canadian pharmacy mall
The Lack of Effect of Routine Magnesium Administration on Respiratory Function in Mechanically Ventilated Patients: Materials and Methods
Subjects
We studied 20 patients admitted to our medical-surgical ICU. All patients requiring mechanical ventilation for more than 3 days were eligible for study. Exclusion criteria included the following: (1) hemodynamic instability’; (2) chest wall instability; (3) preexisting renal failure (creatinine >200 mmol/L); (4) atrioventricular conduction defects; and (5) inability to give informed consent. Patients were also screened to ensure that their baseline levels of serum magnesium were not outside the normal range for our institution (normal values, 0.7 to 1.05 mmol/L). my canadian pharmacy online
Study Design
The study was approved by our University Ethics Committee and we obtained informed consent from each subject. We obtained demographic data (age, sex, race), medication history, and a medical history. We specifically reviewed the medical history for known risks for magnesium deficiency. These included prior diuretic use, alcohol abuse,” recent aminoglycoside administration, and severe diabetes. Figure 1 outlines our experimental protocol. We measured serum concentrations of magnesium along with values for serum potassium, sodium, creatinine, ionized calcium, albumin, total protein, and phosphate. Prior to performing tests of respiratory function, patients were ventilated with 100 percent 02 for 5 min. We then measured values of vital capacity (VC), maximal inspiratory’ pressure at residual volume (Pimax), and maximal expiratory pressure at total lung capacity (PEmax). All measurements were obtained in a seated position and all patients had been at rest, receiving mechanical ventilation for at least 1 h preceding the tests. The VC was measured by a portable spirometer connected to the end of the endotracheal tube.
The Lack of Effect of Routine Magnesium Administration on Respiratory Function in Mechanically Ventilated Patients
Therapy directed toward improving respiratory muscle strength has been advocated for patients with respiratory muscle weakness and respiratory failure once their conditions have been stabilized by initiation of mechanical ventilation. Along with malnutrition, hypomagnesemia is a recognized cause of both skeletal muscle weakness and of respiratory muscle weakness. Patients with chronic obstructive pulmonary disease admitted to an ICU have been found to have reductions of intracellular magnesium levels when compared with control subjects. Although hypomagnesemia is frequent in patients admitted to ICUs, serum magnesium levels do not accurately reflect tissue magnesium levels. A prolonged course of mechanical ventilation has been found in patients with low intracellular magnesium levels despite normal serum levels. Finally, magnesium repletion has been shown to improve parameters of respiratory muscle strength in patients with hypomagnesemia.