Noninvasive Ventilation

Kyphoscoliosis with different aetiologies and post-tuberculosis syndrome are the most common conditions causing restrictive thoracic disorders that predispose patients to the risk of developing chronic hypercapnic respiratory failure. Noninvasive positive pressure ventilation using face masks has become the standard means of treating chronic hypercapnic respiratory failure that arises from restrictive thoracic disorders. Thereby, noninvasive positive pressure ventilation has been shown to improve physiological parameters, most importantly blood gases, and also pulmonary haemodynamics and sleep architecture. In addition, noninvasive positive pressure ventilation is also strongly suggested to improve important outcome parameters such as long-term survival, health-related quality of life, hospitalisation and exercise ability. Therefore, patients with chronic hypercapnic respiratory failure due to restrictive thoracic disorders should be regularly offered long-term noninvasive positive pressure ventilation.

Dyspnoea is the most common symptom of patients with chronic obstructive pulmonary disease (COPD). Exercise training can improve dyspnoea and exercise tolerance in these patients in whom higher intensity levels may be prevented by extreme breathlessness and/or peripheral muscle fatigue. As mechanical loading and inspiratory muscle dysfunction contribute to dyspnoea in COPD, assisted ventilation should provide a symptomatic benefit by unloading and assisting such overburdened ventilatory muscles.

Continuous positive airway pressure and different modalities of noninvasive positive pressure ventilation (NPPV) applied during exercise resulted in improvement of dyspnoea and exercise tolerance. Inspiratory muscle unloading and reduction in intrinsic positive end-expiratory pressure have been considered among mechanisms underlying these effects in COPD patients. Nevertheless, the role of NPPV in pulmonary rehabilitation, if any, is still controversial. The addition of nocturnal domiciliary NPPV during a day-time exercise programme in patients with severe COPD resulted in an improvement in exercise tolerance and quality of life.

As pulmonary physicians, especially those dealing with mechanical ventilation, we are facing the problem of withholding and withdrawing life support in terminally ill patients affected by acute or chronic respiratory disorders every day.

The overall incidence of these practices in Europe is only partially known and, even more importantly, it has been shown that there are important differences between countries or regions, reflecting the absence of a common strategy even within the European Community.

The “shared decision” taken together by physicians, nurses and the patient's family may be the best approach to these decisions. There is good evidence that noninvasive ventilation (NIV) may be used in terminally ill patients with different objectives, such as: 1) life support with no preset limitations on life-sustaining treatment; 2) life support when the patients decided to forego intubation (DNI); and 3) a "pure" palliative measure. Up to 30% of end-stage chronic respiratory patients are receiving NIV in the last days of life, solely to relieve dyspnoea, and this "ceiling" practice has also been applied to end-stage cancer patients. About 50% of DNI patients with acute respiratory failure may also be successfully treated and discharged from the hospital, mainly if affected by chronic obstructive pulmonary disease or chronic heart failure. The success of NIV is strictly dependent on the experience of the staff involved, and the patients should be allowed to withdraw from the treatment in every instance.

Negative pressure ventilation (NPV) was the first reported form of noninvasive ventilation (NIV) to be widely applied to chronic respiratory failure (CRF). However, during the past decades, NPV has gradually lost its former impact and, apart from in a few centres, has been almost completely replaced by positive pressure ventilation (PPV) modes.

The existing plethora of terminology describing NIV modes can sometimes be confusing, especially with respect to ventilators. Pressure-targeted ventilation (PTV) and volume-targeted ventilation (VTV) are the main modes of NIV; Both types can be used in an assisted or controlled setting.

PTV has surpassed VTV in recent years as the treatment option for CRF. Both modes have been successfully applied to NIV in CRF. However, PTV has become the preferred mode due to the higher comfort level for the patient, as well as the lower costs and the compensation it provides for mild-to-moderate mask or mouth leaks. Recently, hybrid modes of PTV and VTV were introduced.

The choice of ventilator and its setting should address different pathophysiological aspects of the underlying disease, of which is variable amongst CRF patients; in patients with COPD, the expiration time should be set at a higher level to avoid air trapping, while higher pressures may be useful to achieve a sufficient tidal volume. Furthermore, the addition of an positive end-expiratory pressure (PEEP) may be helpful to offset intrinsic PEEP in these patients. Various studies have shown that a controlled mode of ventilation is useful and well tolerated by all patients, irrespective of the underlying disease. When a controlled mode of ventilation is favoured, an assist-controlled mode is suggested to increase the patients' subjective tolerance. However, an individualised approach to each patient is beneficial and further studies investigating ventilator settings are needed to continually improve recommendations.

The interface between patient and ventilator is crucial for the success of NIV. In various studies, different interfaces have been used with success. However, despite its high clinical impact, the choice of different interfaces has received little scientific attention. A variety of masks are now available, and manufacturers continue to improve mask design. The majority of interfaces is represented by commercial or custom-made nasal masks and oronasal masks. In special indications, nasal pillows or mouthpieces are used. It is suggested that nasal masks should be used prior to oronasal masks in CRF, since there are fewer limitations and communication with the patients is more convenient. In contrast, if patients are mouth breathers, an oronasal mask is favoured. In patients using nasal masks, leaks can occur through an open mouth, especially during night; these leaks can lead to NIV insufficiency, where both the quality of ventilation and sleep may be reduced. In this case, changing the interface to an oronasal mask should be considered. In general, mechanical ventilation can lead to dryness of the upper airway. Therefore, nasal resistance may be an important reason for reduced compliance, which may be compensated by additional humidification.

The present chapter first reiterates the different mechanisms underlying ventilatory changes occurring during sleep and the capability of noninvasive ventilation (NIV) in correcting abnormal respiratory events and improving sleep quality in different diseases. In order to ensure long-term NIV efficiency, appropriate strategies for monitoring ventilation and sleep, during NIV treatment, are proposed. Different tools, allowing monitoring of chronic respiratory failure patients treated using long-term home NIV, and their respective interests and limitations are successively reviewed. Tools only aiming to recognise the consequences of residual events, such as oxygen desaturations or increases in nocturnal transcutaneous carbon dioxide tension are distinguished compared with more complex strategies, such as respiratory polygraphy and polysomnography. Finally, specific software, designed by ventilator manufacturers for at-home monitoring, and the use of flow signals included in NIV devices, are remarked upon. These data may provide useful information for clinicians.

The expansion of home mechanical ventilation (HMV) in the last 15 yrs was stimulated by the introduction of noninvasive mask ventilation and the recognition that more patient groups could benefit.

In the management of healthcare resources, cost-analysis currently represents a method for evaluation of the expenditure due to the effects on health of a new (or specific) intervention and for assessing it in the economic perspective. Disability-adjusted life-yrs, healthy-yr equivalents and quality-adjusted life-yrs are all time-based measures of health that include the impact of interventions on years of life lost due to premature mortality and years of life lived with a nonfatal health outcome, weighted by the severity of that outcome.

Although the effectiveness of noninvasive HMV has been addressed, the impact of this treatment on the overall costs has not been clearly reported or demonstrated and very few data based on a true economic analysis in patients under noninvasive HMV have been published. Direct and (partially) indirect cost calculations have been observed and reported, especially in chronic obstructive pulmonary disease patients under noninvasive HMV. The most recent data underline the large impact of noninvasive HMV on both patient outcome (reduction of recurrent admissions and increase in quality of life) and family burden (unemployment, financial and social issues), thus prompting further studies with appropriate cost-effectiveness and/or cost-utility analysis.