Respiratory muscle insufficiency in acute respiratory failure of subjects with severe COPD: treatment with intermittent negative pressure ventilation

Abstract

Nine subjects with severe chronic obstructive pulmonary disease (COPD) in acute respiratory failure (ARF) and with marked weakness of the respiratory muscles (Group A) underwent intermittent negative pressure ventilation by means of an iron lung (8 h daily for 7 days). Seven subjects with COPD in stabilized chronic respiratory failure (Group B) were studied as controls and submitted to the same medical therapy without ventilator treatment. Functional respiratory tests were performed before and after 7 days of treatment. After ventilatory treatment, Group A showed an increase of maximum inspiratory pressure (PImax), maximum expiratory pressure (PEmax), vital capacity (VC), arterial oxygen tension (PaO2), pH and a decrease of residual volume (RV), total lung capacity of (TLC) and arterial carbon dioxide tension (PaCO2) (all statistically significant). No improvement was ascertained in the functional parameters of Group B. The expiratory muscles seem to play a determining role in ARF. We conclude that the iron lung is a useful therapeutic defence in removing muscular fatigue and in restoring a good level of respiratory compensation of ARF in severe COPD.

Domiciliary nocturnal nasal intermittent positive pressure ventilation in COPD: mechanisms underlying changes in arterial blood gas tensions

“…Intennittent mechanical ventilation, using negative or positive pressure devices, results in improved arterial blood gas tensions during spontaneous ventilation in patients with respiratory failure due to chest wall defonnity and neuromuscular disease [1][2][3][4][5]. Similar results have been reported in hospital for patients with cluonic obstructive pulmonary disease (COPD) but studies have involved relatively short periods of ventilation, during the day, using negative pressure devices (6)(7)(8)(9)(10)(11). The improvement in arterial blood gas tensions in COPD has usually been attributed to improved respiratory muscle strength secondary to the relief of chronic fatigue [6][7][8][9][10].…”

Respiratory Muscle Function in Patients With Neuromuscular Disorders and Cardiopulmonary Diseases

“…The first intervention must be to rest the respiratory muscles either by partially unloading them, e.g. through the use of bronchodilators and the clearance of bronchial secretions, or by placing them on complete rest through assisted ventilation for at least 24 hours and probably longer 9,91,92 . Treatment of respiratory muscle weakness should also be directed at improving alveolar ventilation, delivering adequately oxygenated blood to the respiratory muscles, and preventing hypoxia and hypercapnia.…”

“…Long‐term nocturnal support by negative pressure ventilation (NPV) applied to the chest wall has been shown to improve respiratory muscle function, alveolar ventilation and quality of life in some patients with COPD, 9,91 but the studies were uncontrolled and the number of patients investigated was small. Shapiro et al 98 conducted a randomised, controlled, double‐blind clinical trial of inspiratory muscle rest produced by NPV in a much larger group of patients (n=184) with severe COPD.…”

“…In COPD complicated by chronic respiratory insufficiency, the inspiratory muscles become progressively weaker because of hyperinflation secondary to airflow obstruction and reduced energy supply due to chronic hypoxia and hypercapnia 9 . PI max in patients with COPD is approximately 56‐73% predicted, 8,9,12 and in stage III COPD, PI max and PE max may be very low (46 ± 25.1 and 72 ± 31.1 cm H 2 O respectively), indicating a marked reduction in respiratory muscle strength 9 . Furthermore, TwPdi response to bilateral phrenic nerve stimulation at functional residual capacity (FRC) is reduced in patients with COPD compared with controls (16.9 vs 26.2 cm H 2 O) 11,50 .…”

“…Respiratory muscle weakness is a common feature of several neuromuscular diseases, 1‐6 and is associated with a higher morbidity and mortality 2,3 . There is increasing awareness that respiratory muscle weakness can be a confounding factor in many diseases, such as malnutrition, 7 chronic obstructive pulmonary disease (COPD), 8‐12 congestive heart failure (CHF) 13‐16 and sepsis, 17 and it is a complication of many metabolic diseases, endocrine disorders, 18 electrolyte imbalance, 19 and steroid therapy 20 . All these conditions may co‐exist or be encountered in critically ill patients.…”