Assisted ventilation at home: is it worth considering?

[Domiciliary ventilation in patients with COPD]

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) has become one of the main indications for domiciliary ventilation, which is usually non-invasive (NIV). This review focuses on the pathophysiology processes and clinical trial data that underlie current guidelines from international societies.

STATE OF THE ART

To date most published studies about domiciliary ventilation in COPD have been short-term and their message is complicated by the presence of significant methodological problems. The two controlled studies of > or =12 months-duration both found that survival was not improved by long-term NIV. Domiciliary ventilation may be considered when long-term oxygen therapy is unsuccessful and when failed with a progressive deterioration in clinical respiratory status with recurrent episodes of acute hypercapnic respiratory failure. A diurnal PaCO(2) > or =55 mmHg (7.3 kPa) is a necessary but not sufficient condition to consider domiciliary ventilation.

CONCLUSION

Domiciliary ventilation should only be initiated in selected patients on the basis of clinical symptoms and exacerbation frequency. Until further characterization of patients who are likely to respond, the response to treatment should be assessed regularly.

Noninvasive ventilation and obstructive lung diseases

The key role of noninvasive positive pressure ventilation (NPPV) is well documented in chronic obstructive pulmonary disease (COPD) patients with acute respiratory failure (ARF) since it may avoid endotrachal intubation in >50% of cases when used as the initial treatment. However, currently only minimal data is available to assess usefulness of NPPV in COPD patients on a long-term basis. Even if such studies are difficult to manage, there is clearly a need for prospective studies comparing long-term oxygen therapy (LTOT) and NPPV in the most severe COPD in a large amount of patients and on a real long-term basis of several years. Two randomized prospective studies are being completed in Europe and the first preliminary results show that NPPV is associated with a reduction of hospitalization for chronic respiratory failure decompensation. The main beneficial effect of long-term mechanical ventilation in COPD patients with chronic respiratory failure implies a correction of nocturnal hypoventilation that could persist beyond the ventilation period because of a temporary improvement in carbon dioxide sensitivity that is often blunted in these patients. A synthesis from the literature suggest to consider NPPV for severe COPD patients who present with chronic hypoxia and hypercapnia and develop an unstable respiratory condition. Instability may be appreciated on a clinical basis and confirmed by a progressive worsening of arterial blood gas tensions, leading to frequent cardiorespiratory decompensations with ominous ARF episodes. NPPV should also be considered after an ARF episode successfully treated by noninvasive ventilation but with the impossibility to wean the patient from the ventilator. Thus, noninvasive positive pressure ventilation could be proposed as a preventive treatment in severe chronic obstructive pulmonary disease patients with unstable respiratory condition associated with fluctuating hypercapnia before, during and after an acute respiratory failure episode, avoiding the need for a tracheotomy. Adjunction of noninvasive ventilation to exercise rehabilitation is under evaluation.

Noninvasive ventilation in neuromuscular disease

The treatment of respiratory failure in patients who have NMD continues to be an evolving process. Negative-pressure ventilation, once prominent in the 1940s and 1950s, gave way to intermittent positive-pressure ventilation with tracheostomy or endotracheal tubes in the 1960s. Now there is a resurgence of noninvasive ventilation, brought about by innovative modes of positive pressure delivered through nasal and facial masks. Although frequently relegated to second-line choices, negative-pressure devices still offer a practical treatment alternative as patient preference still plays a role in selecting a proper mode of ventilation. Studies have shown that noninvasive ventilation can prevent or reverse respiratory failure and improve quality of life and longevity. Despite the seemingly widespread acceptance of noninvasive ventilation in the treatment of respiratory failure, physicians still appear reluctant to use ventilatory assistance in the neuromuscular arena. In 1985, a survey found that respiratory support systems were utilized routinely in only 33% of the 132 responding Muscular Dystrophy Association (MDA) clinics. Bach recently surveyed 273 MDA clinic directors and co-directors from 167 clinics, to evaluate their current use of mechanical ventilation. Ventilatory assistance was recommended and used electively in only 43 (26%) of the 167 clinics. Furthermore, it was the policy in 68 of the clinics to discourage the use of mechanical ventilation. Even more importantly, only 2 physicians who discouraged the use of mechanical ventilation were familiar with the newest noninvasive methods of ventilatory support. Sadly, although our methodologies in the treatment of respiratory failure continue to improve, physician practice has lagged behind. Physicians who treat patients who have NMD need to become cognizant of these new techniques and incorporate them into their present therapeutic armamentarium.

Survival and long-term follow-up of tracheostomized patients with COPD treated by home mechanical ventilation. A multicenter French study in 259 patients. French Cooperative Study Group

To define more clearly the value of home mechanical ventilation by tracheostomy (HMVT) in patients with advanced COPD, a retrospective French multicenter study group analyzed the prognostic factors and long-term survival of 259 patients with severe COPD, who were tracheostomized for at least 1 year. Seventy-eight percent of the patients died by the end of the observation period. The actuarial survival rate for the overall study population was, therefore, 70 percent at 2 years, 44 percent at 5 years, and 20 percent at 10 years. These results appear to be better than those of the major published series and compare to the prognosis of COPD patients treated by long-term oxygen therapy (LTO) 15 hr/24 hr. The parameters most closely correlated with a survival for more than 5 years were age < 65 years, use of an uncuffed cannula, and a PaO2 > 55 mm Hg in room air during the 3 months after tracheostomy (p < 0.01). This study, therefore, confirmed the feasibility of HMVT in COPD and should lead to a review of the place of permanent tracheostomy in the long-term prognosis of severe COPD patients.

Quality of life of patients treated by home mechanical ventilation due to restrictive ventilatory disorders

The quality of life of patients with hypoventilation and home mechanical ventilation (HMV) has not been well described. Modern quality of life assessment techniques were therefore introduced in a cross-sectional study of patients treated with HMV. The aim was to study various aspects of the patient's quality of life and relate them to the underlying diseases, blood gases and the type of ventilatory connection. The study comprised 39 patients, most of them ventilated only during the night (n = 35). Nasal ventilation predominated (n = 29). Patients treated with HMV reported satisfactory levels of both psychosocial functioning and mental well-being that compared well with a general population group. Their quality of sleep was generally good. The quality of life measures were mainly influenced by the patients' underlying disease. Patients with scoliosis expressed in almost all instances the best quality of life. The quality of life of patients with ventilation by tracheostomy was reported to be at least as good as that of patients with nasal ventilation. The global quality of life estimation was mainly determined by the mental state of the patients and their sleep quality and only to a minor extent by physical handicaps. In conclusion, the patients treated with HMV reported good psychosocial functioning and mental well-being, in spite of severe physical limitations and dependence on regular nocturnal ventilation.

Pulmonary rehabilitation in chronic respiratory insufficiency. 5. Home mechanical ventilation

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Using ventilators for speaking and swallowing

An inflated cuff, although commonly thought to be required for the ventilator-dependent patient with a tracheostomy cannula, precludes speaking and has adverse implications for swallowing. Clinical trials with five ventilator-dependent, cognitively intact individuals with glottic control document that a deflated cuff is compatible with ventilation, preserves oral communication, and restores safe alimentation by mouth.

Assisted ventilation. 5. Non-invasive and domiciliary ventilation: negative pressure techniques

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Respiratory pump failure and its treatment

The activity of the nervous system determines the respiratory pattern, although the degree of alveolar ventilation also depends on the mechanical properties of the chest wall and lungs. Failure to ventilate the lungs adequately may be due to defects in respiratory control or the respiratory muscles or to an increase in the work that the muscles have to perform. The selection of the best method of treatment of respiratory pump failure requires an exact knowledge of its cause. Phrenic nerve stimulation or mechanical assistance by positive and negative pressure ventilators or by a rocking bed, can be very effective. Each of these methods has a place in the long-term management of ventilatory failure.

Ventilator-dependent children

The issue of the ventilator-dependent child is a relatively-new one in Australia. Ventilator-dependent children pose complex and unique ethical, medical, economic and psychological problems. The experience of two Australian centres that are involved with the care of ventilator-dependent children is reported. Most of these children now are being cared for at home. Aspects of home care are outlined. After the initial period, the technical aspects are not a problem for most parents for whom the major issues are the provision and funding of nursing support. The complex ethical issues that are involved are discussed. It is concluded that undergoing ventilation at home rather than in a hospital appears to make the best of an otherwise almost-intolerable situation for ventilator-dependent children, but that much more information is required about the outcome for these children and the long-term psychosocial impact of this treatment.

Intermittent positive pressure ventilation by nasal mask: technique and applications

Intermittent positive pressure ventilation delivered non-invasively through a well-fitting nasal mask has been used to control nocturnal hypoventilation in three patients with severe, combined cardiorespiratory and skeletal disease. The advantages of this approach to domiciliary ventilation are described and the requirements of the ventilator are defined.

Domiciliary ventilatory support: an analysis of outcome

Prolonged ventilatory support has been used to treat 51 patients with respiratory failure secondary to skeletal (22) or neuromuscular (29) disease. Symptomatic relief was achieved in five patients with rapidly progressive neurological disease who died within 27 months. The remaining 46 patients, aged 11-69 years at presentation, have been followed for more than two and a half years. All but 10 were treated with negative pressure ventilation from the outset, intermittent positive pressure ventilation being used initially in the others and continued at home in three. Nocturnal negative pressure ventilation has been used at home by 39 patients. A permanent tracheostomy has been maintained in 14, to facilitate positive pressure ventilation in three and to circumvent upper airway obstruction during sleep in 11. Sustained improvement in symptoms and arterial blood gas tensions has been maintained, independence and the capacity for gainful employment have been regained in those of an appropriate age, and the incidence of subsequent hospital admissions has been low. Neither the mode of presentation nor the aetiology of the restrictive ventilatory defect influenced outcome in patients with stable or only slowly progressive primary disease.

Assisting ventilation in respiratory failure by negative pressure ventilation and by rocking bed

The present study was undertaken to evaluate the effectiveness of acute ventilation by rocking bed (RB) and by negative-pressure ventilator (NPV) on arterial oxygenation and carbon dioxide tension in seven patients in whom respiratory failure (PaCO2 [+/- SD], 64 +/- 4 mm Hg; PaO2, 54 +/- 10 mm Hg) was consequent on nonobstructive ventilatory impairment. The increase in SaO2 (percent above baseline, 5 percent RB and 6 percent NPV) was similar for both methods, but a greater fall in PCO2 (percentage change in PCO2, 3 percent RB; 15 percent NPV; p less than 0.05) was observed during NPV. Diaphragmatic and accessory muscle electrical activity was markedly reduced during NPV but remained unchanged or increased on RB. Asynchronous breathing was frequently observed with RB but only rarely with NPV. These preliminary results suggest that effective mechanical ventilatory support could be achieved with either RB or NPV. However, their long-term effects as compared with those of positive-pressure ventilation remain to be explored.

Late sequelae of pulmonary tuberculosis treated by thoracoplasty

With the help of information provided by the Office of Population, Censuses and Surveys the survival up to 1 July 1985 of the 171 patients treated for pulmonary tuberculosis by thoracoplasty at Papworth from 1951 to 1953 was determined. Thirteen (8%) could not be traced, 65 (38%) had died, and 93 (54%) were alive. For those who were traced the survival at 10, 20, and 30 years from the date of operation was 93%, 79%, and 65%. This represents a significantly greater mortality rate than that predicted from the Registrar General's review of deaths in England and Wales (1841-1984). Nineteen patients died from cardiorespiratory failure. Eight of the survivors are known to have developed respiratory failure, five having enjoyed apparently good health before this was precipitated by intercurrent illness or drugs. A stepwise logistic regression analysis using information from the 124 patients for whom full details were available showed significant associations between the development of cardiorespiratory or respiratory failure and a preoperative contralateral artificial pneumothorax, older age at operation, the presence of cavities before operation, and male sex. In a questionnaire 50 of the survivors (57% of those who replied) reported cough, 45 (51%) breathlessness, 41 (47%) wheeze, and 24 (27%) ankle swelling. Nineteen (22%) smoke and the same number now attend a chest clinic. Many patients treated for tuberculosis by thoracoplasty have respiratory symptoms and some are at risk of respiratory failure. There are grounds for considering that they should be reviewed periodically by a chest physician.

Importance of airflow obstruction after thoracoplasty

Thirty six patients previously treated for pulmonary tuberculosis by thoracoplasty were studied to determine the prevalence and effect of airflow obstruction. The mean (SD) FEV1 was 1.3 (0.65) 1 and the mean forced expiratory ratio (FER) 64% (12%). FEV1 was less than predicted in every patient whereas FER was less than predicted in 30, being below the lower 98th percentile in 15 (42%). In the 18 patients who complained of breathlessness the means of the standardised residuals (SR) for FEV1, peak expiratory flow (PEF), and FER were significantly lower and that for residual volume/total lung capacity (RV/TLC) significantly higher than those for the 18 patients who were not breathless (all p less than 0.0001). There was no difference in the smoking history of the two groups. Only three of the 23 patients in whom reversibility of airflow obstruction was assessed showed a greater than 25% increase in PEF. None showed an increase in FEV1 of greater than 15%. The 18 who were breathless had significantly lower values of arterial oxygen tension (PaO2) and higher values of arterial carbon dioxide tension (PaCO2) (p less than 0.0001). Thirteen of these patients were in chronic respiratory failure (PaO2 less than 8.0 kPa or PaCO2 greater than 5.9 kPa, or both) compared with only one of the 18 who were not breathless. The indices correlating best with PaO2 and PaCO2 were SR FEV1 and SR PEF respectively. SR FEV1 accounted for 34% of the variance in PaO2 and SR PEF for 29% of the variance in PaCO2. Airflow obstruction has been found to be common in patients with a thoracoplasty and to be associated with hypoxia and hypercapnia.