Effect Of Different Ventilatory Modes On Haemodynamics, Gas Exhange And Oxygen Transport In Mechanically Ventilated Icu Patient With Acute Respiratory Failure

ventilation (IRV) with its two types (pressure and volume controlled) represents an altenlative ventilatory strategy in hypoxaemic acute respiratory failure. PCIRV is associated with a lower peak airway pressure thus reducing the incidence of lung injury. VCIRV maintains a constant tidal volume and minute ventilation in spite of variations in respiratory mechanics.We studied thirty patients whose age (mean ± SD) was 55.6 ± 11.6 years, 50% of them were females. Patients were first ventilated using VCV and applying PEEP of 5 CmH20 and a period of 30 minutes were allowed for stabilization then all the parameters were measured and repeated every hour for 6 hours. Then the ventilator was switched to PCV and applying PEEP of 5 CmH20 and a period of 30 minutes were allowed for stabilization then all the parameters were measured and repeated every one hour for 6 hours. The ventilator was then switched to VCIRV with I : E ratio of 2 : 1 and the parameters were measured after 30 minutes and every one hour for 6 hours. The ventilator was then switched to PCIRV with I : E ratio of 2 : 1 and all parameters were measured 30 minutes later and every one hour for 6 hours.The parameters measured were :* Haemodynamics : cardiac output, cardiac index, stroke volume, stroke index, left ventricular stroke work index, right ventricular stroke work index, systemic vascular resistance, pulmonary vascular resistance, pulmonary capillary wedge pressure, central venous pressure, pulmonary artery pressure. They were measured through pulmonary artery (Swan Ganz) catheter. Arterial blood pressure was measured invasively through radial artery. Pulse rate was taken from the ECG.Respiratory mechanics: Mean aIrway pressure, static and dynamic compliance.Gas exchange:Arterial Oz tension. Arterial COz tension. Arterial Oz saturation. Arterial Oz content.Alveolar-arterial Oz tension difference. Oxygenation index.Shunt fraction.PaCOz-ETCOz•Oxygen consumption. Carbon dioxide production.We found that PCrRV was associated ’with improvement in most of gas exchange parameters as reflected by increased Pa02, Sa02, O2 content, oxygenation index and decreased PaC02. Shunt fraction was surprisingly increased.Considering haemodynamics, most of the parameters were associated with a significant decrease reflecting a deleterious effect of perRV on haemodynamics.Considering respiratory mechanics, PCrRV was associated with significant increase in mean airway pressure and a significant decrease in static and dynamic compliance.So we recommend the application of PCrRV for ventilating patients with acute hypoxaemic respiratory failure with close observation and monitoring of haemodynamic parameters and the use of cardiac support measures when indicated.