Pressure reign over Inverse Ratio ...

Pressure reign over Inverse Ratio Ventilation as a course to Reduce Peak Inspiratory influence and Provide Adequate Ventilation and Oxygenation (*1)

A major question at issue in the management of the ventilator-dependent patient with fiercely reduced lung compliance and hypoxemia is the maintenance of adequate oxygenation while minimizing the risk of complications resulting from high PIP, high of the same heights of PEEP, and increased [FIO.sub.2]. [1-3] These complications are associated with the one and the other the ARDS and severe pneumonia requiring mechanical ventilation.

compressing control with inverse ratio ventilation has been advocated for use in ARDS. [4-7] This fashion of ventilation. PcIRV, was accomplished in this report by means of use of the Siemens Servo 900 C ventilator. The PcIRV is a pressure-rather than volume-controll accident of delivering Vt. The Vt with PcIRV is generated at a constant crushing throughout the inspiratory time. The inspiratory follow decelerates once the PIP is reached. The PIP is controll by means of setting the pressure on the ventilator. The PIP, f and inspiratory time are the ventilator settings which together will determine the VE delivered to the patient. [89 This terminates in pressure ventilation rather than conventional whirl ventilation.

The PcIRV has been demonstrated to improve oxygenation, possibly resulting from increase Paw and from a more level distribution of gas. [10] The PcIRV has been shown to be clinically useful in the mechanical ventilation of patients with bitter bilateral pneumonia and ARDS. [4-6] We report 19 patients previously ventilated with IPPV and favorably changed to PcIRV in an attempt to provide improved oxygenation and ventilation.

METHOD

The patient clump consisted of 19 patients admitted to our Medical, Surgical, Trauma ICU between August 1985 and May 1986 Twelve of these patients had ARDS defined as acute lung injury resulting in diffuse bilateral radiographic infiltrates, relentless refractory hypoxemia, pulmonary capillary wedge press less than 16 cm [Hsub2O] uncorrected for pule and a marked reduction in pulmonary compliance. This diagnosis was made from clinical and roentgenographic characteristics. Seven of the patients had pneumonia. In this retrospective analysis these patients, their diagnoses, clinical course, and treatment were restoreed from patient records. (Table 1) These patients were fix uponed for PcIRV because of their diagnosis and worsening clinical condition characterized by way of failure to adequately ventilate with IPPV. The mean age of the collection was 53 years old with a range of 17 to 76 years. There were 11 females and eight males. A Siemens 900 C ventilator was used to ventilate all 19 patients. A General Electric oscilloscope, example 46-203461G1A, was interfaced with the ventilator to perceive the gas flow patterns. All patients had an indwelling arterial cannula and 11 had pulmonary artery catheters.

Consideration for switching a patient from conventional IPPV to PcIRV was given when PIP was [is greater than]50 cm [Hsub2O] [FIO.sub.2] was [is greater than]0.6, and cry [is greater than]10 cm [Hsub2O] with worsening hypoxemia. Since this was not a prospective cogitation there was some variation in these criteria to be paid to physician preference and individual clinical presentation. However, it is the intent of this report to not past nor future the findings in 19 patients ventilated with PcIRV and to compare those physiological parameters upon IPPV prior to switching to PcIRV.

Prior to institution of PcIRV, 14 patients were ventilated with assist-control, and five with synchronized intermittent mandatory ventilation (both will be referr to as IPPV). The indications for changing from IPPV to PcIRV were inadequate oxygenation as characterized from a [PaO.sub.2] of less than 60 mm Hg with worsening lung compliance in the face of increasing PIP, cry and [FIo.sub.2]. At this point, clinical discernment suggested that increases in chirp and [FIo.sub.2] would be necessary to continue to maintain adequate oxygenation and might be detrimental to the redemption of these patients. The PcIRV was implemented in an attempt to improve oxygenation without further increasing PIP, [FIo.sub.2] or cry All patients were given diazepam (Valium) or morphine or a combination of one as well as the other with institution of PcIRV. A small in number patients required pancuronium bromide (Pavulon) for ventilatory have the direction of Several patients did appear more comofrtable upon PcIRV and followed the settle ventilatory pattern without sedation or paralysis.

Respiratory monitoring of PIP, cry f, Vt, PeTCO.sub.2], proximal Paw (as read from digital display onward the 900 C), Ve, arterial kindred gases, and pulse oximetry were performed. Cardiac function was monitored on heart rate, blood pressure, cardiac output and pulmonary wedge influence in those patients with pulmonary artery catheters in place. These values were compared with those of the same patients while ventilated upon PcIRV as opposed to their last recorded measurements upon IPPV.