Randomised Control Trial to Study the Role of Non-invasive Ventilation Using Pressure Support Ventilation Versus Adaptive Support Ventilation With Intellisync Mode in Patients With Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Acute exacerbation of chronic obstructive pulmonary disease are periods of acute worsening during the course of illness which increase hospital admission and mortality. Intensive care unit admission and mortality are higher among elderly and those with co-morbidities(9).

Non-invasive methods of ventilation can be used in mild to moderate exacerbation of COPD. They prevent most of the complications of invasive mechanical ventilation and has also reduces mortality in acute exacerbations of COPD. In mild to moderate COPD exacerbations(pH-7.25 to 7.35), non-invasive ventilation (NIV) failure rate is found to be 15% to 20%. In severe COPD exacerbations, NIV failure rate approaches upto 52% to 62%(9).

Adaptive support ventilation (ASV) and pressure support ventilation (PSV) are among the non-invasive modes of ventilation used in COPD exacerbations.

Adaptive support ventilation:

Adaptive support ventilation is a closed loop ventilation in which it provides both pressure support and pressure controlled ventilation as per the patient needs(10). The mode was first described by Hewlett in 1977 in form of mandatory minute ventilation with adaptive pressure control(11). Later Dr. fleur T Tehrani invented this mode, which was later introduced in Galileo ventilator(11). This mode supports patient with pressure support when patient has spontaneous breath and when target ventilation is not reached it delivers pressure control breath to achieve adequate ventilation. In this mode, minute volume is controlled via Vt/RR combination based on respiratory mechanics of the patient to keep the work of breathing at minimum(10). This mode calculates the tidal volume and respiratory rate to be delivered by otis equation in its algorithm after %minute volume being set by the clinician to ensure effective ventilation at the alveolar level. The inputs provided by the clinician in this mode is %minute volume based on ideal body weight, ETS, flow trigger, maximum pressure limit(12). The mode after being initiated will deliver a series of 5 pressure limited breaths and deliver a inspiratory pressure15 cm h2o above the baseline pressure during which it calculates dynamic compliance, RCe, tidal volume and respiratory rate. These measurements are used to determine the initial targets of breath rate and tidal volume(12). After which based on respiratory rate and effort of the patient, inspiratory pressure, mandatory breath are adjusted automatically to meet the set %minute volume. ASV mode can be used as initiation, maintenance and weaning phases of mechanical ventilation and it provides full, partial or minimal ventilator support during any of these phases(12). The number of manual ventilatory adjustments are less compared to conventional mode of ventilation in ASV(13). Some randomized controlled trials performed in Non-COPD suggest shorter weaning time with ASV mode of ventilation. Shorter weaning is attributed to automated inspiratory pressure change according to patient efforts, thereby reducing ventilator patient dysynchrony and frequency of manual manipulation. In a randomized control study done by c. kirakli et. Al found out that in COPD patients ASV mode of ventilation(24 hours) has shorter weaning duration compared to pressure support mode of ventilation(72 hours) (p-value 0.041). But, this study has not found any difference in the duration of mechanical ventilation, length of stay in ICU, weaning failures when ASV and PSV mode were compared(p-value>0.05)(10) A randomized controlled trial conducted among 80 patients by Bialais et. al comparing safety, efficacy and workload of intellivent- ASV and conventional mode of ventilation (pressure assist mode and pressure support mode) found out that tidal volume delivery and spo2 were most of the time in the optimal range (6-10ml/kg IBW, spo2-92 to 96% for normal lung/ ARDS and 95-99% for brain injury) for intellivent-ASV compared to conventional mode of ventilation(p-value-0.001 and 0.005). However it was found that Pmax (maximum inspiratory pressure measured) was higher (24±5 versus 22±6) with intellivent-ASV mode than conventional ventilation(p-value-0.042). There was no significant difference between intellivent-ASV and conventional mode of ventilation in terms of time spent in optimal range of parameters like respiratory rate, PETCO2, PEEP, minute ventilation, FIO2 , RCexp. There was also no difference in length of mechanical ventilation, length of ICU stay, length of hospital stay, ICU mortality, hospital mortality and total mortality. There was comparative less need for ventilator adjustment with intellivent-ASV mode compared with conventional mode of ventilation(14).