HIGH FLOW NASAL OXYGEN VERSUS BILEVEL POSITIVE AIRWAY PRESSURE VENTILATION IN PREECLAMPTIC PATIENTS WITH ACUTE HYPOXAEMIC RESPIRATORY FAILURE

Patients in group I will receive HFNO by AIRVO™ (Fisher & Paykel Healthcare Ltd., Auckland, New Zealand). The initial flow rate will be 50L/min and will eventually be diminished in case of intolerance. Humidification chamber temperature will be set at 37 °C and will eventually be diminished in case of intolerance. FiO2 will be 100% and then gradually reduced to 50% when pulse oximetry values are acceptable. Patients in the group II will receive oxygen therapy via intermittent non- invasive positive pressure ventilation, BiPAP mode Dräger Savina ventilator, and a face mask will be used. P (low) of 5 cm H2O to 10 cm H2O and an inspiratory pressure P (high) of 10-20 cm H2O above PEEP. FiO2 will be 100% and then gradually reduced to 50 % when pulse oximetry values are acceptable. Respiratory rate will be from 10-12. It will be applied for 30 minutes every hour with 30 minutes rest, and will be applied continuously for 6-8 hours at night. The size of the face mask will be chosen to optimize subject comfort while minimizing air leaks. If the patient cannot tolerate the treatment, she will be excluded from the study. Patients will be assessed for treatment weaning then interruption when they meet the following criteria:

• Respiratory rate ≤24 breaths/min
• No recruitment of accessory muscles of respiration during calm breathing.
• Haemodynamic stability (heart rate <110/min; mean blood pressure between 60 and 90 mmHg and no Haemodynamically significant arrhythmias.
• SpO2 > 95 % on FIO2 ≤30.
• Improvement of blood gases.

Criteria for treatment failure and the need for intubation:

• Respiratory rate > 25 breaths/min
• The use of accessory muscles of respiration.
• Haemodynamic instability (heart rate >110/min; mean blood pressure below 90 or significant arrhythmias.
• Failure to achieve SpO2 above 91.
• PaO2/ FiO2 ratio <150, PaCO2 >45 or PH <7.30.