**5. Selection of optimal ventilator and mode of NPPV**

NPPV is broadly classified into volume preset and pressure preset devices, early studies of long-term domiciliary NPPV mainly concern patients on volume preset ventilators, whereas in the last 5-10 years pressure preset machines, particularly bilevel pressure support equipment has become more prominent.

**Volume preset** machines gives the adjusted tidal volume regardless of mechanics of respiratory system (i.e. compliance, resistance and active inspiration) and if there is a leak from mask or mouth, patient cannot deliver the adjusted tidal volume.

On the contrary **pressure preset** machines gives the adjusted pressure according to respiratory system mechanics by changing the flow and compensates the mask leaks. However pressure preset machines may not to be sufficient in patients who need high inspiratory pressure. Pressure support ventilators on a first line basis, especially with pressure support mode, is easier to adjust and to synchronise with the patient. CPAP and BPAP are the pressure support

patients who also show continued sleep disruption or worsening hypercapnia and nocturnal hypoventilation despite oxygen therapy should be further investigated probably with polysomnography to rule out other sleep related breathing disorders. Finally we need to define optimal NPPV and interface design and settings in hopes of improving compliance of long-term therapy for all types of appropriate patients, who are likely to benefit from NPPV.

Another potential application of NPPV in patients with severe stable COPD is to enhance exercise training during rehabilitation. It has been shown that when delivered during cycle ergometry, CPAP, pressure-support ventilation, and proportional-assist ventilation all reduce inspiratory effort and dyspnea in hypercapnic COPD patients (Petrof, Calderini, & Gottfried 1990; Bianchi et al. 1998). Recent studies in patients with severe COPD in a 6-week exercise training program has reported that, NPPV alone was more effective than supplemental oxygen alone as adjunct to physical exercise in improving submaximal exercise tolerance and health related quality of life (HRQOL) (Borghi-Silva et al. 2010). These studies demonstrated that NPPV can be used to increase or prolong the intensity of exercise

Any patient on NPPV is classified as receiving Critical Care Level 2 care, defined as ''Patients requiring more detailed observation or intervention including support for a single failed organ system''. This suggest NPPV should be administered in an intensive care unit (ICU) or high dependency unit (HDU) setting, but it has been widely recognised that NPPV can be successfully used outside the ICU and HDU with dedicated NPPV team able to provide 24/7 care. This is however only feasible in large units with many trained staff (Manuel, Russell, & Jones. 2010). NPPV is more frequently used outside the ICU, in HDU, respiratory wards and emergency departments (EDs) (Brochard, Mancebo, & Elliott 2002; Hill 2004). It has been suggested that each hospital should have a specific designed area with experienced staff, where patients requiring NPPV can be transferred with the

NPPV is broadly classified into volume preset and pressure preset devices, early studies of long-term domiciliary NPPV mainly concern patients on volume preset ventilators, whereas in the last 5-10 years pressure preset machines, particularly bilevel pressure support

**Volume preset** machines gives the adjusted tidal volume regardless of mechanics of respiratory system (i.e. compliance, resistance and active inspiration) and if there is a leak

On the contrary **pressure preset** machines gives the adjusted pressure according to respiratory system mechanics by changing the flow and compensates the mask leaks. However pressure preset machines may not to be sufficient in patients who need high inspiratory pressure. Pressure support ventilators on a first line basis, especially with pressure support mode, is easier to adjust and to synchronise with the patient. CPAP and BPAP are the pressure support

minimum delay (British Thoracic Society Standards of Care Committee 2002).

**5. Selection of optimal ventilator and mode of NPPV** 

from mask or mouth, patient cannot deliver the adjusted tidal volume.

**3.10 Adjunct to exercise training in pulmonary rehabilitation programs** 

training sessions in patients with severe COPD.

**4. Where to administer NPPV?** 

equipment has become more prominent.

ventilators. CPAP as the name implies, requires the airway pressure not to change between inspiration and expiration. However BPAP therapy was originally conceived with the idea of varying the administered pressure between the inspiratory and expiratory cycles. BPAP is the commonly used pressure preset method. BPAP devices deliver separately adjustable inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP). The IPAP and EPAP levels are adjusted to maintain upper airway patency, and the pressure support (PS=IPAP-EPAP), which augments ventilation.

Three modes of NPPV were also defined according to principles of cycling of inspiration. NPPV devices can be used in the 1) **spontaneous mode** (the patient cycles the device from EPAP to IPAP), 2) the **spontaneous timed (ST)**/assisted-controlled (AC) mode (a backup rate is available to deliver IPAP for the set inspiratory time if the patient does not trigger an IPAP/EPAP cycle within a set time window otherwise patient the device from EPAP to IPAP), 3) the **timed (T)** /pressure controlled (PC) mode (patient cannot trigger and cycle the inspiration- inspiratory time and respiratory rate are fixed).

**Volume assured pressure support / volume target BPAP (VT-BPAP)** which is a hybrid mode of volume preset and pressure support ventilation was available by the end of the 1990s. Release of dual portable ventilators providing either pressure support ventilation or volume preset ventilation opened the way for new potent turbine pressure support ventilators able to deliver real volume ventilation with the average volume assured pressure support ventilation mode which represents a flexible way for managing the most difficult patients (Storre et al. 2006). Patient delivers the target tidal volume by the support of adjusted pressure support range. VT-BPAP has been developed in which the IPAP-EPAP difference is automatically adjusted to deliver a target tidal volume (Storre et al. 2006; Ambrogio et al. 2009; Janssens, Metzger, & Sforza 2009; Jaye et al. 2009)

**Proportional Assist Ventilation** is another mode still under investigation. It provides a level of ventilatory assistance which is proportional to the patient's respiratory effort throughout the respiratory cycle. Some studies reported better comfort and tolerance with proportional assist ventilation but found no differences in rates of mortality or intubation (Fernandez-Vivas et al. 2003; Gay, Hess, & Hill 2001). Guidelines make no recommendation about the use of proportional assist ventilation versus pressure support ventilation in patients who are receiving NPPV for ARF, due to lack of sufficient evidence.
