VersaMed's iVent201[TM] ventilator system: a revisit.

Although we reviewed this ventilator a year and a half ago VersaMed has made a significant addition to the iVent201[TM], capabilities which warrants another look. We also note that we took one of these ventilators to Vietnam and China during last year's "Counsel of Six" educational program. The ventilator traveled through three countries on 7 different airlines. Additionally it was transported in not too gentle or smooth vans and autos. Despite not being well padded and with unsure handling at airport and airline baggage and security stations the iVent worked perfectly at each use. This was a good if unintended test of durability for transport situations.

The VersaMed iVent201[TM] ventilator system with the intensive care package is intended for use with critical care, transport or home care patients who weigh 10 kg or more. The flow delivery system is a turbine unit consisting of a variable speed DC motor and a rotary compressor. Oxygen may be added using a high pressure or low pressure gas source. Depending on the ventilator settings the internal battery lasts for one to two hours and charges automatically whenever the unit is connected to an external power supply. The unit weighs approximately 22 pounds and has a relatively small footprint--about the size of an original Macintosh computer. The iVent201[TM] can be used with either a single or dual breathing circuit. A dual breathing circuit was used to bench test ventilator operation in this evaluation. The circuit incorporates a fixed orifice differential pressure transducer at the patient wye and requires a one-way valve within the inspiratory limb. All modes and options were examined except for the use of a low pressure oxygen source (an adaptor was unavailable).

Modes on the iVent201[TM] are volume or pressure limited assist/control, volume or pressure limited SIMV, pressure support and CPAP. Although the option 'easy exhale', accessed through Advanced Settings in the menu, rapidly dumps pressure at the initiation of exhalation, the exhalation valve is not open as defined In previous ventilator reviews. Also, no volume-targeted pressure control or volume-targeted pressure support modes are available on the iVent201[TM]. The iVent201[TM] does have adjustable rise time, adaptive (demand) flow, parameters preset according to the patient's body weight, 100% oxygen suction, apnea ventilation, graphics, sigh breaths and both pressure and/or flow triggering capabilities. There are hard keys below the display screen for Silence, 100% [O.sub.2], Manual Breath, Hold (which was not active), and Clear to minimize alarm pop-up boxes and to mute the audible alarm for 30 seconds.

Above the hard keys the color display screen measures 8.4 inches (diagonal) and most of the displayed ventilator values are large enough to be viewed easily. One of three formats may be selected for the display screen: main, monitoring and home care. When the home care display option is selected, the mode, tidal volume and total rate are clearly visible against a black background. The monitoring screen displays additional information including waveforms and allows access to ventilator settings via menu options in the lower right-hand corner for mode, parameters, alarms, and "browse". Browse is a feature for the graphics display that allows the user to move a bar along the waveform to view actual parameter values at any point in time.

Screen navigation for the main display is accomplished by rotating a dial knob that sequentially highlights the various parameter options. Pressing the knob opens a window from which desired values are selected and set with another click of the knob. The windows format was acceptable except in the case of an accidental click on the knob that would close all the windows and bring back the main display. This seemed to be more of a problem in the alarm limits window where six alarms, each with high and low values had to be scrolled through, highlighted and clicked on to change, and then clicked on to confirm. If one hurried the process and clicked at the wrong time, the window closed. Any changes in alarm limits made prior to the accidental click, however, were retained and took effect immediately.

Aside from the navigational issues of a windows format, the most impressive feature of the iVent201T[TM] was the responsiveness and power of the turbine generated flow delivery system. The turbine flow delivery was smooth and the demand valve accommodating, allowing flow rates up to 180 LPM for spontaneous breaths and there was no noticeable difference in flow delivery when a high pressure source gas was not used. The 'idle' or pre-inspiratory speed of the turbine can be adjusted to low, mid, high, max or auto under Rise Time in the Advanced Settings option found in the Menu. The higher the idle speed, the shorter the rise time, since the higher turbine speed is able to generate a higher initial flow rate, and therefore, a sharper rise in pressure. The auto setting is recommended by the manufacturers.

Under Advanced Settings is the option to set the Adaptive Flow on high, mid, low or off. In a volume controlled mode the peak flow rate may be manually set or the flow pop-up window can be set to adaptive flow. Adaptive flow allows the patient flow on demand until the set volume is delivered in a volume limited mode. Another feature of adaptive flow is active in the volume control SIMV mode when the flow rate during a mandatory breath automatically increases to match the flow pattern of the patient's spontaneous breath. Adaptive flow is always operational in the SIMV mode even when a manual peak flow is set.

A new, excellent addition to the unit's versatility is VersaMed's Adaptive Bi-Level mode of ventilation. Adaptive Bi-Level mode is intended for non-invasive positive pressure ventilation. Described by VersaMed as a combination of pressure control and pressure support, adaptive bi-level breaths may be time, pressure or flow triggered and flow or time cycled. Time triggering occurs by setting a backup respiratory rate. Inspirations are flow cycled unless the adjustable flow cycle (% of peak flow) is set too low in which case the operator-set inspiratory time will terminate the breath. If the set inspiratory time limit displayed along the bottom edge of the main screen is flashing, inspiration was terminated by the inspiratory time limit. If flow cycling occurs, the inspiratory time limit does not flash. The inspiratory pressure (P-High) and baseline pressure (P-Low) are also adjustable from the same screen that allows the operator to set rise time (in seconds), flow/pressure triggers, inspiratory time limit, and the flow cycle setting as a % of the peak flow (peak flow % termination). The ability to adjust rise time, flow cycling and inspiratory time is what makes VersaMed's bi-level mode "adaptive".

The adaptive bi-level mode performed as advertised in our laboratory when the iVent201[TM] was connected to a test lung under a wide range of leak conditions. After adjustment of the flow trigger (turned OFF at high leak rates) and the flow cycle threshold (set on 70%), ventilation was accomplished for simulated mask breathing with leaks from 3.5 LPM up to 44 LPM. A pressure trigger of minus 0.5 cm H2O captured 80% of the inspiratory efforts simulated with the test under the highest leak rates. The estimated leak in LPM displayed on the iVent201[TM] was very close to the leak measured by the RT 200 calibration instrument. Although 44 LPM for a leak may be a tad excessive, it's nice to know that the turbine flow delivery system of the iVent201[TM] kept up with the flow demand. The other alternative to high leak situations is to set the respiratory rate as close as possible to the patient's respiratory rate. As mentioned earlier, respiratory rate can also be set in the adaptive bi-level mode.

From the main screen the high pressure in volume controlled ventilation can be set as an alarm and as a pressure limit. Inspiration will end in volume control when the inspiratory pressure equals the high pressure limit. There will be a message warning that the tidal volume is too low. The low tidal volume alarm is adjustable from 15%-85% of the set tidal volume and may be turned off completely. In pressure controlled ventilation a volume limit can be set. Although pressure controlled ventilation is not volume-targeted as stated above, it is volume limited in that a high tidal volume limit can be set. A warning message appears if the volume limit is exceeded.

Another feature worth a special mention is the graphics. The main screen displays two waveforms with access to loops, trends, or mechanics through the menu button in the lower right corner. The waveforms have remarkable clarity considering their small size.

Overall, the iVent201[TM] was found to have exceptional flow delivery capabilities without need of a high pressure source gas. Modes and options on the iVent201[TM] would appear to meet most patient's needs, particularly in terms of demand flow capabilities. Its portability is also a plus.