Condition category
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Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status
Results overdue

Plain English Summary

Not provided at time of registration

Trial website

Contact information



Primary contact

Dr Christina Alexopoulou


Contact details

Intensive Care Unit
University Hospital of Heraklion

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Sleep quality in critically ill patients on proportional assist ventilation with load-adjustable gain factors (PAV+) vs pressure support (PS) - a randomised controlled cross-over trial


Study hypothesis

Previous studies have repeatedly reported sleep disruption in intensive care unit (ICU) patients with reduced nocturnal sleep efficiency and reduced slow wave and rapid eye movement sleep.Critical illness itself, the ICU environment, medications, and patient-ventilator interactions may all be contributing factors to altered sleep architecture. Alteration of sleep quality and quantity can have significant adverse consequences prolonging mechanical ventilation and ICU stay.

Proportional assist ventilation (PAV) is a mode of support during which the ventilator pressure is proportional to instantaneous flow and volume and hence to pressure generated by the respiratory muscles. The necessity of regular measurements of respiratory system mechanics imposes a major obstacle on the use of this mode. A software has been developed (PAV+) which automatically adjusts the flow assist (cmH2O/L/sec) and volume assist (cmH2O/L) such as to represent always constant fractions of the measured values of resistance and elastance of the respiratory system6 by applying a 300 msec pause maneuver at random intervals at the end of selected inspirations. It was recently shown that these brief end-inspiratory occlusions do not affect sleep quality or sedation requirements in a selected group of critically ill patients.

Parthasarathy and Tobin observed greater sleep fragmentation in critically ill patients during pressure support (PS) than during assist-volume control ventilation with backup rate. Numerous studies have shown that compared to PS, PAV improves the synchrony between patient and ventilator and may thus decrease sleep disruption and improve sleep quality. The aim of this study will be to compare sleep quality under constant conditions in critically ill patients ventilated with PAV+ and PS.

Ethics approval

Ethics Committee, University Hospital of Heraklion Crete, approved on 12/12/2006 (ref: 13449)

Study design

Randomised controlled crossover trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Sleep quality in critically ill patients on mechanical ventilation


Patients will be connected to an ICU ventilator (Puritan-Bennett® 840), able to ventilate them with PS and PAV. Polysomnography will be performed in each patient as previously described for 24 hours starting 10 PM in single rooms in the intensive care unit with the window blinds closed. During the study day patients will be ventilated randomly either on pressure support or on PAV+ mode. The pressure support at which the patient was ventilated before the study will serve as baseline pressure support. With PAV+ the percentage of unloading will be set such as to achieve a mean inspiratory airway pressure similar to that with baseline pressure support. In the 24-h study period patients will be ventilated for six 4-h periods (10PM-2AM, 2AM-6AM, 6AM-10AM, 10AM-2PM, 2PM-6PM, 6PM-10PM), three 4-h periods with PS, and three with PAV+. Each patient will be initially randomised to receive 4 hours of either PS or PAV+ followed by alternating 4-h periods of PS and PAV+.

Intervention type



Not Applicable

Drug names

Primary outcome measure

Effect of PAV and PS in sleep quality.

Secondary outcome measures

Patient - ventilator interaction during sleep. Flow (V’), volume (V), airway pressure (Paw), end-tidal CO2 (PETCO2), the motion of the rib cage and abdomen, inspiratory (TI) and expiratory (TE) time, total respiratory cycle time (TTOT) and peak inspiratory airway pressure (Pawpeak) will be measured on a breath-by breath basis, while coefficient of variation of tidal volume (VT) and TTOT will be calculated.

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

Critically ill patients (>18 years old, both males and females) who are receiving mechanical ventilation for at least 48 hours will be studied. At the time of the study all patients will be haemodynamically stable and ventilated on PS through cuffed endotracheal or tracheostomy tubes with anticipated further mechanical ventilation of at least 24-h duration. All patients must achieve a score of 0 on the Richmond Agitation Sedation Scale (RASS) either with or without intravenous (IV) propofol.

Participant type


Age group




Target number of participants


Participant exclusion criteria

1. Anticipated ICU stay <24 h
2. Premorbid diseases that could confuse interpretation of sleep monitoring including central nervous system (CNS) diseases and sleep disorders
3. Haemodynamic instability (BP <90 mmHg despite therapy)
4. Glasgow Coma Scale <11 and acute physiology score >13
5. General anesthetic, drug overdose, or alcohol intoxication within the preceding 24 h

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

Intensive Care Unit

Sponsor information


Cretan Critical Care Society (Greece)

Sponsor details

Intensive Care Unit
University Hospital of Heraklion

Sponsor type

Research organisation



Funder type

Research organisation

Funder name

Cretan Critical Care Society (Greece)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes