We believe mechanical ventilation can and should be more natural. Our PAV+™ software is a breath type that better manages work of breathing in spontaneously breathing patients and promotes natural breathing compared to conventional mechanical ventilation.^††,([FOOTNOTE=Pohlman MC, et al. Excessive tidal volume from breath stacking during lung-protective ventilation for acute lung injury. Crit Care Med. 2008;36(11):3019-3023.],[ANCHOR=],[LINK=]) PAV+™ software manages the patient’s work of breathing differently than other traditional modes of mechanical ventilation†† in the following ways.([FOOTNOTE=Puritan Bennett™ 980 Ventilator Operator's Manual],[ANCHOR=],[LINK=])

With PAV+™ Breath Type, the Patient Defines Rate, Depth, and Timing

• Flow is an indicator of demand. It tells us when the patient wants to begin inspiration, how deep the breath should be, when to end the breath and how often to breathe.([FOOTNOTE=Wilkins RL, Stoller JK, Scanlan CL. Egan’s Fundamentals of Respiratory Care. 8th ed. Louis, MO: Mosby; 2003.],[ANCHOR=],[LINK=])
• The PAV+™ software continuously monitors patient demand by measuring flow and volume every 5 milliseconds and by knowing the % Support set.
• As patient demand changes, PAV+™ software can change support pressure within the same breath. 

When the % Support is set, the patient and the ventilator are sharing the work of breathing as defined by the clinician.

• Work of breathing can be calculated using the equation of motion.([FOOTNOTE=Younes M, et al. Proportional Assist Ventilation. In: Tobin MJ. Principles And Practice of Mechanical Ventilation, Third Edition. McGraw Hill Professional; 2012.315-346.],[ANCHOR=],[LINK=])
• When R and C are known, it’s possible to calculate patient-generated pressure (P_MUS) and work of breathing in real time using the equation of motion.([FOOTNOTE=Younes M, et al. Proportional Assist Ventilation. In: Tobin MJ. Principles And Practice of Mechanical Ventilation, Third Edition. McGraw Hill Professional; 2012.315-346.],[ANCHOR=],[LINK=])^,([FOOTNOTE=Bosma K, Ferreyra G, Ambrogio C, et al. Patient-ventilator interaction and sleep in mechanically ventilated patients: pressure support versus proportional assist ventilation. Crit Care Med. 2007;35(4):1048-1054.],[ANCHOR=],[LINK=])^,([FOOTNOTE=Younes M, Webster K, Kun J, Roberts D, Masiowski B. A method for measuring passive elastance during proportional assist ventilation. Am J Respir Crit Care Med. 2001;164(1):50-60.],[ANCHOR=],[LINK=])^,([FOOTNOTE=Grasso S, Ranieri WM, Brochard L, et al. Closed loop proportional assist ventilation (PAV): Results of a phase II multicenter trial. Am J Respir Crit Care Med. 2001, 163:A303.],[ANCHOR=],[LINK=])^,([FOOTNOTE=Younes M, Riddle W, Polacheck J. A model for the relationship between respiratory neural and mechanical outputs: III. Validation. J Appl Physiol. 1981;51(4):990-1001.],[ANCHOR=],[LINK=])

P_MUS + P_VENT = (flow x resistance) + (volume ÷ compliance)

• PAV+™ software measures resistance and compliance every 4-10 breaths.
• Once % Support is set, clinicians can use the work of breathing (WOB) bar for real-time feedback on how much work the patient is doing.
• The work of breathing bar displays both total work of breathing (WOBTOT) and the patient work of breathing (WOBPT).
• Adjust the % Support setting to maintain the patient’s WOB (WOBPT) within the green zone.
• Associated fatigue values for work of breathing are shown as being outside the green zone.

The work of breathing bar, when coupled with good clinical assessment, can help take the guesswork out of determining the appropriate level of mechanical ventilation support. Providing real-time feedback on work of breathing helps the clinician keep the patient at a sustainable level of work—reducing the risk for respiratory muscle atrophy, but off-loading enough work to avoid fatigue.([FOOTNOTE=Hermans G. Increased duration of mechanical ventilation is associated with decreased diaphragmatic force: a prospective observational study. Crit Care. 2010;14:R127.],[ANCHOR=],[LINK=])^,([FOOTNOTE=Anzueto A, Peters JI, Tobin MJ, et al. Effects of prolonged controlled mechanical ventilation on diaphragmatic function in healthy adult baboons. Crit Care Med. 1997;25(7):1187-1190.],[ANCHOR=],[LINK=])^,([FOOTNOTE=Haitsma JJ. Diaphragmatic dysfunction in mechanical ventilation. Curr Opin Anaesthesiol. 2011;24(2):214-218.],[ANCHOR=],[LINK=])