Autor
M.J. Kampelmacher, MD, PhD
M.A. Gaytant, MD, PhD
E.J.A. Westermann, MD
Centre for Home Mechanical Ventilation, University Medical Centre Utrecht, Utrecht, The Netherlands
Introduction
In the Netherlands, home mechanical ventilation (HMV) was initiated more than 40 years ago, primarily in patients with neuromuscular diseases. In those days HMV was performed by a cuirass or tracheostomy. The slow growing number of candidates for HMV marked the establishment of the first two Centres for HMV in Groningen and Utrecht, after several years to be followed by the Centres for HMV in Rotterdam and Maastricht. The introduction of non-invasive positive pressure ventilation (NPPV) around 1988 explains the rapid growth of the number of HMV-patients from then on. This was further increased by the familiarity of chest physicians with continuous positive airway pressure (CPAP), the autonomy of patients, the growing complexity of patients on the intensive care unit (ICU) and by the internet.
For a long time the Centres for HMV directed their attention mainly towards support of the inspiratory muscles by applying HMV. Following a chest infection, tracheostomy still had to be performed quite often, both in patients who had not been ventilated yet and in patients who had been using NPPV for months or even years. In the latter, invasive ventilation was also instituted if the number of hours on the ventilator became 15 or more. Following a visit of one of the authors (MJK) to the USA techniques for support of the expiratory muscles, like air stacking and mechanical in- and exsufflation, were introduced in 2001. From then on continuous non-invasive ventilatory support became a real possibility in the Netherlands.
Pathophysiology
In several, but not all, neuromuscular diseases the respiratory muscles may be affected, either directly, as in a range of congenital myopathies and muscular dystrophies, or indirectly due to problems in the motor neurons (amyotrophic lateral sclerosis), the peripheral nerves (hereditary motor and sensor neuropathies) or the neuromuscular transmission (myasthenic syndromes). A diminished capacity of the inspiratory muscles may lead to a decrease in vital capacity (VC), inspiratory mouth pressure (MIP) and sniff nasal inspiratory pressure (SNIP). Often the capacity of the expiratory muscles is simultaneously reduced, which may lead to a lower peak cough flow (PCF).
With progression of the disease, first REM-related and later also non-REM-related sleep disordered breathing may ensue. Although (obstructive) sleep apnea is more frequently seen in patients with neuromuscular diseases than in the general population, the sleep disordered breathing is foremost characterized by alveolar hypoventilation. For detection of the latter, demonstration of nocturnal hypercapnia is much more reliable than pulsoximetry, as the latter may be normal, even in patients with severe alveolar hypoventilation. The resulting nocturnal hypercapnia leads to vasodilatation in the brain, causes brain edema, and disturbed sleep architecture, resulting in a decreased sleep quality and efficiency. Nocturnal hypercapnia may result in retention of sodium bicarbonate and a slight metabolic alkalosis, which may be demonstrated during daytime. Further progression will eventually result in chronic respiratory insufficiency, type II, with hypercapnia (PaCO2 > 45 mmHg or 8,0 kPa during daytime), usually accompanied by some hypoxemia (PaO2 < 75 mmHg or 10,0 kPa). Without treatment patients will eventually die due to progressive hypercapnia ending in a hypercapnic coma and/or progressive hypoxemia, resulting from hypoventilation, atelectasis and pulmonary secretions, ending in heart failure.
Finally, chest infections, which may develop any time due to alveolar hypoventilation and a reduced PCF, may have a great influence on the development of acute (on chronic) respiratory failure and outcome.
The most important goal of HMV is to improve the quality of life by reducing complaints and symptoms of respiratory failure and increasing patient independence, exercise tolerance and communication. In addition, HMV is aimed at improving sleep quality and efficiency, preventing secondary (pulmonary) morbidity and improving life expectancy. To achieve these aims, reduction of (nocturnal) hypercapnia is mandatory and a goal on itself. The mechanisms of action for reaching these goals are, as yet, unclear. Resetting of the respiratory centre in the brain is believed to be one of the most important points of action. In addition, resting of the respiratory muscles and improvement of thoracic and pulmonary compliance may play a role. To reach the latter not only HMV but also lung volume recruitment techniques (LVR) seem to be essential. Improvement of sleep quality and efficiency seem to be important as well. Finally, improvement of cardiorenal hemodynamics by reducing PCO2 and improving PO2 may be relevant to reach the goals of HMV. In the past 30 years the tremendous effectiveness of HMV has been demonstrated repeatedly. Particularly in slowly progressive diseases, like poliomyelitis and Pompe’s disease, HMV has been shown to be able to prolong life rather with decades than years. Even in more progressive diseases, like Duchenne’s muscular dystrophy, life may nowadays be extended well beyond the age of 40. Given the overall success of HMV, and particularly NPPV, HMV is increasingly being applied in patients with rapidly progressive diseases, like amyothrophic lateral sclerosis (ALS), albeit with moderate effectiveness. If started on time, NPPV may prolong life in ALS-patients on average with 6-9 months compared to palliative care without HMV. Invasive ventilation by a tracheal cannula (TPPV) may increase life expectancy with 3 years on average, but in most patients with ALS the profit in years is counteracted by the progressive loss of quality of life. For this reason, all four centres for HMV in the Netherlands do have a negative attitude towards TPPV in ALS.
Indications and prerequisites
Formally, HMV is only indicated when there is scientific evidence of effectiveness and the aims of HMV can be met. Consequently, patients on an ICU who cannot be weaned off the ventilator are not automatically candidates for HMV. In clinical practice, however, HMV may also be prescribed in individual patients, even on a temporary basis, for reasons of comfort and efficiency, even without scientific evidence (yet). Setting the indication for HMV is typically the responsibility of a Centre for HMV. Any patient with a neuromuscular disease, which may affect the respiratory muscles, is a potential candidate for HMV, irrespective of age and lung function. Instead, the indication for HMV is much more determined by complaints of nocturnal hypoventilation or respiratory insufficiency, and by the severity of respiratory insufficiency in terms of (nocturnal) PCO2. In general, HMV is indicated once nocturnal hypoventilation has developed. In addition, there are several prerequisites before HMV may become a reality. The most important of these are: the possibility of ventilating the patient with a ventilator which is suitable for the home setting; a possibility to communicate with the patient; a safe home setting; full cooperation and motivation of the patient; absence of a poor prognosis; and absence of medical futility. To qualify for HMV ICU-patients should be clinically stable, optimally weaned from the ventilator and there should be no other options (medication, oxygen therapy or CPAP) for improving the clinical condition of the patient. Although there are no formal contra-indications for HMV, the latter should not be initiated when the goals cannot be met. Thus, in the Netherlands a negative advice is usually given for patients in a comatose state, patients with a locked-in syndrome and patients with a very poor prognosis (expected survival to be less than three months).
Referral of patients
In order to reach the goals of HMV, to keep away TPPV and to prevent secondary complications of respiratory insufficiency, patients should preferably be referred early and before they have become respiratory insufficient (PCO2 >45 mmHg or 6,0 kPa during daytime). Ideally, patients are referred before they have developed nocturnal hypoventilation. To facilitate the referral of patients, the four Centres for HMV have produced a small card with referral criteria, which was sent to all neurologists, pulmonary physicians and rehabilitation physicians in the Netherlands in May 2010. In addition, these criteria are displayed on the websites of the VSCA (www.vsca.nl) and the four Centres for HMV. The most important reasons to refer a patient to a Centre for HMV are (suspected) complaints of (nocturnal) hypoventilation, pulmonary restriction (VC <50%), (nocturnal) hypercapnia (PCO2 > 45 mmHg or 6,0 kPa), nocturnal desaturations, and the desire to receive information about HMV. Although patients may be announced by phone, they must be referred in writing.
Pathway
Most patients with neuromuscular diseases follow a pathway that is characterized by five steps. First, patients are referred by a neurologist or rehabilitation physician, sometimes following a multidisciplinary outpatient clinic where the patient is first met. Next, patients are informed on the possibilities regarding HMV, either at the Centre for HMV or in the hospital where they have been admitted. Nowadays, patients are informed at home only in exceptional cases. During these talks, which take on average 60-90 minutes, patients are informed on the tasks and operating procedure of the Centre for HMV. In addition, information is given on the possible forms of ventilation (NPPV or TPPV) with formulation of both advantages and drawbacks of each form. While the consequences of each option are clearly stated, the importance of making a choice and framing advanced directives is stressed. Then, patients are seen 1-6 times a year at the Centre for HMV to determine the optimal moment for initiating HMV. The frequency depends both on the progression of the disease and the probability of nocturnal hypoventilation. During these visits lung function, peak cough flow and blood gases are measured, patients are questioned and examined with regard to possible nocturnal hypoventilation and there is room for questions with regard to chest infections, feeding (PEG-catheter) and travelling, and with regard to prospective HMV. Once nocturnal hypoventilation is suspected, patients will undergo analysis for nocturnal hypercapnia. This may be performed at home by measurement of end-tidal CO2 or clinically by measuring blood gases, usually by means of an arterial line on a special care unit. Once nocturnal hypoventilation is demonstrated the next step is to initiate HMV by determining the optimal ventilator, settings and interface for a particular patient. If nocturnal hypoventilation can not be demonstrated after 3-5 nights of deep sleep the patient will mostly return to the outpatient department of the Centre for HMV. However, in patients with severe complaints of nocturnal hypoventilation but without nocturnal hypercapnia, like patients with ALS, HMV may be started for three months on trial. As nocturnal normocapnia is no goal in these patients, clinical effectiveness is largely determined by the reduction of complaints. Finally, patients are discharged to their home (home, living congregation or nursing home) once their safety can be guaranteed. Besides a safe environment (alarms) and sufficient care this implies training of family members, volunteers and professionals, in particular. Once at home, patients are visited by nurses of the Centre for HMV, both on a regular and an as needed basis. In addition, patients are asked to visit the outpatient clinic once or twice a year. Every working day one of the nurses gives consultations by phone, there is continuous accessibility and availability of a nurse, physician and technician of the Centre for HMV and of a technician of the company which provided the equipment. Furthermore, the effectiveness of HMV is measured at least twice a year at home by pulsoximetry and capnometry.
Role of the Centres for Home Mechanical Ventilation
Compared to other (European) countries the care for patients with HMV in the Netherlands is much more organised. The initiation of HMV is more or less restricted to the four Centres for HMV, which are recognized as such. Probably as a result of this, the prevalence of patients on HMV in the Netherlands is significantly lower than in many other countries, like France, Germany and Sweden. Moreover, while in Europe the proportion of patients with lung diseases, neuromuscular diseases and chest wall deformities is equal (33% each) the situation in the Netherlands is quite different. On January 1, 2010 54% of patients had a neuromuscular disease, 21% a chest wall deformity and only 12% a lung disease. Although the Centres for HMV in the Netherlands function as a spider in a web, their facilities are minimal and, thus, their role is primarily advisory. Consequently, other physicians are principally responsible for the overall care of these patients. At home this is taken care of by the general practitioner, in the hospital by the supervising physician of the ward and in the nursing home by the nursing home physician. The Centres for HMV may always be consulted for problems related to the HMV of these patients. Apart from informing patients, nurses, physicians and other carers, the Centres take care of indicating patients for HMV, initiating HMV (on their ‘own’ ward or somewhere else) and, in particular, supporting these patients in their home setting. In addition, the Centres coordinate each link of the HMV-chain and provide education for both voluntary aids and professionals. Finally, the Centres are actively involved in innovation and scientific research to improve the care for patients in (potential) need of HMV.
Non-invasive ventilation
Since the introduction of NPPV in the Netherlands around 1990 the proportion of patients using NPPV has increased. On January 1, 2010 77% of a total of 1807 patients on HMV were using NPPV. Nowadays NPPV is the first choice in HMV. NPPV may be admitted by a nasal mask, nasal pillows, an oronasal mask, a total face mask, mouth mask with lip seal or a mouthpiece. The wide range of interfaces and the mouthpiece for HMV during daytime in particular, has enabled the option of continuous NPPV without a tracheostomy. NPPV is a relatively simple technique which can be used at home for most patients. Although patients may need help with LVR-techniques while using NPPV, the amount of care needed is usually much less in comparison to TPPV. A potential drawback of NPPV is the inability to effectively ventilate patients due to obstruction or leakage of air under the mask or through the mouth. In addition patients may experience dyspnea, aerophagia and decubitus of the skin of the nasal bridge. Most of the problems can be solved quite easily. The adaptation to NPPV may take some patients as long as several months, however.
Invasive ventilation
Nowadays, elective tracheotomy has been largely displaced by NPPV. Elective TPPV might still be considered, however, if patients do not accept or tolerate NPPV, if NPPV is not effective (anymore), if coughing is insufficient despite LVR-techniques and in case of aspiration. Most patients with TPPV have been tracheotomized while on the ICU following endotracheal intubation for an acute (on chronic) respiratory insufficiency. Once stabile, the TPPV may be changed to NPPV with closing of the tracheostomy.
Lung volume recruitment techniques
In the Netherlands, techniques for support of the expiratory muscles, like air stacking and mechanical in- and exsufflation, were introduced in 2001. The aim of these techniques is to keep the airways open by improving cough. This is achieved by lung volume recruitment (LVR): the insufflation of the lungs with the maximum volume of air that the lungs can contain. In addition to expand the intrathoracic gasvolume, LVR aims to stretch the expiratory muscles, thereby increasing their preload, to increase the compliance of the lungs and thoracic wall, and to improve clearance of airway secretions. For the latter, a minimum PCF of 160 L/min is needed. In healthy adults the PCF should be more than 600 L/min. By combining LVR-techniques with simultaneous manual compression, the PCF can be further increased. Air stacking above maximal inspiration may be achieved by insufflation with a resuscitator balloon or a volume controlled ventilator. Following maximal inspiration, the patient should hold his breath by closing the vocal cords. Without expiring, extra air is insufflated by a mouthpiece or a full face mask, in synchrony with the next inspiration. This is repeated several times until the maximum insufflation capacity (MIC) is reached. Notwithstanding progressive weakness of the respiratory muscles and a declining VC, the MIC may increase by training. In case of bulbar weakness it is, however, impossible to increase the MIC above the VC. Air stacking may result in a MIC which is three times the VC and a PCF that is double the spontaneous PCF. To maintain these improvements, it is essential to stack air at least three times per day. For many patients and their carers this might be a problem, however, due to poor motivation and endurance. During chest infections air stacking may be used more often, up to six times an hour, for several days. Air stacking should be considered when PCF becomes <300 L/min, particularly with recurrent chest infections or retention of airway secretions. In our practice, air stacking is routinely recommended and instructed with a VC <50%. Coughing may be resembled by a machine, which first applies a positive pressure in the airways followed by a negative pressure. As insufflation is directly followed by exsufflation, airway secretions may be mobilized and expectorated. Mechanical in- and exsufflation (MI-E) may be applied non-invasively by a full face mask and invasively by an endotracheal tube or a tracheal cannula. To be effective a pressure gradient of =80 cm H2O between in- and exsufflation is needed. The patient should be asked to cough during exsufflation. MI-E may be applied several times per day on a routine basis. During chest infections, however, MI-E should be applied as often as necessary. Frequencies of 6 or more per hour during several days are not unusual. MI-E should be continued until all secretions have been mobilized or pulsoximetry shows a saturation of =94% during inspiration of room air. MI-E may increase PCF, improve survival and reduce hospitalization if combined with other LVR-techniques. In addition, MI-E may avoid endotracheal intubation for acute respiratory insufficiency due to chest infections. However, randomized studies into the effect of MI-E only with respect to hospitalization, survival and the prevention of chest infections, are, as yet, lacking. MI-E may be considered when the PCF becomes <160 L/min or when other LVR-techniques are unsuccessful in clearing the airways. Given the reported risk of airway obstruction, in the Netherlands MI-E is only applied clinically yet. To assess the safety of MI-E in the home setting clinical studies are urgently needed.
Emergencies
For emergencies related directly or indirectly to HMV the Centres for HMV are continuously accessible and available. However, in the home setting the general practitioner (GP) caries primary responsibility for overall care and in the clinical setting the physician in charge. The Centres for HMV can only be held responsible for HMV-related care. Thus, in case of medical emergencies not directly related to HMV, like chest infections or dyspnea, the GP should be contacted first. The GP may consult a nurse or physician of the Centre for HMV. If a patient needs further assessment the GP should refer the patient to the most nearby hospital. As most Centres for HMV do not have facilities for acute care, transferring a patient to the Centre for HMV is only seldom indicated. Specialists for the local hospital may always contact a physician of the Centre for HMV for further assistance. Even medical emergencies which might be related to HMV should be dealt with locally. The Centres for HMV do not function as ‘fire brigades’ and the distance between the Centre and the patient is often too large to deliver immediate service. If a patient can not wait 1-2 hours before a nurse of the Centre for HMV arrives, the patient must call 112 or should be seen by the GP and, possibly, be referred to the local hospital. Most technical emergencies are dealt with by the equipment contractors. These home care companies not only take care of servicing all HMV-equipment but may also be called directly in case of (suspected) equipment failure. Usually, a response time of 4 hours is arranged by contract. If the equipment can not be repaired on the spot, it may be changed for reserve equipment. For reasons of safety, patients who are ventilated for 16 hours or more per day are supplied with two ventilators, usually one bedside and one mounted on the wheelchair. The home care company may contact the HMV-nurse or -technician in certain situations. The latter is in charge of the quality control procedures and may warn other Centres for HMV in the event of (possible) systematic equipment malfunction.
Organization and reimbursement
Since 2001 all four Centres for HMV have their own region. The Centre for HMV in charge is determined by the postal code of the patient’s residence. Thus, new patients should be referred to the Centre for HMV that eventually will take care of the patient, even if that patient is temporarily hospitalized out of his/her region. The regions and corresponding postal codes are displayed on the websites of the VSCA (www.vsca.nl) and the four Centres for HMV. Patients may opt for a Centre for HMV serving a different region, but this should always be arranged by the mutual Centres. Until present reimbursement is arranged by an all-in contract, which is more or less restricted to the four Centres for HMV. All equipment is owned by the university hospital where the Centre for HMV is based. The contract provides for all personnel costs, travel expenses, acquisition, service and repair of equipment, and for all disposables. In the near future the financial organization of the Centres for HMV might be changed. In advance, the four Centres have formulated nine products, which might be used once the new reimbursement system becomes operational. Given the changes in HMV in the last 35 years, and the last decennium in particular, funding of HMV hopefully becomes adequate and adapted to the present standard of care.
Conclusion
By 2010 HMV has been applied in the Netherlands HMV for more than 40 years. Particularly in the last decennium major changes have taken place, both with respect to the organization as to the execution of HMV. The Netherlands are one of the very few countries where a very high standard of true home care is offered by the Centres for HMV in terms of the nursing, medical, technical and administrative services delivered. However, due to the enormous success of HMV and the consequent growth of the Centres for HMV the facilities of the Centres for HMV have become too meagre, which starts to cause more and more problems within the chain of care. Hopefully, changes in reimbursement with the introduction of DRG’s will have a positive influence on the role the Centres keep playing in the future. Huge improvements in equipment – both ventilators and interfaces – have made NPPV even more popular than it already was. As a result, elective tracheostomy is performed less and less. The latter is also the consequence of the introduction of LVR-techniques, like air stacking and mechanical in- and exsufflation. Through all these improvements NPPV is nowadays regarded as the primary means of HMV in the Netherlands and continuous (24/7) non-invasive ventilatory support has become a real possibility.
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