Diego DĂaz Internal Medicine Resident
Introduction • High-frequency oscillatory ventilation – Patients’ lungs are held inflated • to maintain oxygenation • carbon dioxide is cleared by small volumes of gas • moved in and out of the respiratory system at 3 to 15 Hz. • minimize the atelectotrauma
• the increasing use of HFOV – absence of good evidence of effectiveness led to develop a study to determine it´s effectiveness
Methods • Study Design – randomized, controlled trial – HFOV compared conventional MV – Patients were recruited • 29 hospitals England, Wales, and Scotland.
Methods • Patients – Undergoing MV – PAFI 200 or less • While receiving PEEP 5 or greater
– bilateral pulmonary infiltrates without left atrial hypertension – expected to require at least 2 more days of MV
Methods • PATIENTS – Excluded • • • •
had undergone MV 7 or more days < 16 years weighed less than 35 kg lung disease characterized by airway narrowing or air trapping • recent lung surgery.
Methods • randomization to either
– HFOV or – conventional mechanical ventilation • 1:1 ratio
– Stratified
• study center • Pao2 :Fio2 ratio – ≤113 or >113
• Age
– ≤55 or > 55 years
• Sex
• Each center had one HFOV ventilator
Methods • Study Treatments – HFOV group • Novalung R100 ventilator – until the start of weaning – initial settings » ventilation frequency of 10 Hz » mean airway pressure of 5 cm of water over plateau » flow rate 20 lt / min » cycle volume of 100 ml » Fio2 of 1 » a fixed » 1:1 inspiratory:expiratory time ratio.
Methods • Paco2 was controlled to maintain ph >7.25 – increasing the cycle volume – If this was insufficient • frequency was reduced by 1 Hz
– If 5 Hz was reached • Clinician would suggest other measures – To control Paco2
Methods • The Pao2 was maintained 60 – 75 mm hg – Hypoxemia was treated • increasing the mean airway pressure • increasing the Fio2
– If a patient reached • a mean airway pressure 24 cm of water and • Fio2 level of 0.4 or less + Pao2> 60 for 12 Hours – Patient was switched to pressure controled ventilation
• Patients could be restarted HFOV up to 2 days after start weaning
Methods • conventional-ventilation group – treated according to local practice – encouraged to use pressure-controlled ventilation • At 6-8 ml per kg of idela body weight • Use PEEP and Fio2 used ARDS network study
Methods • Data Collection – demographic characteristics, ventilation before enrollment – Data to calculate APACHE II – coexisting medical conditions – the use of sedatives and muscle relaxants – ventilator settings
• each day recorded data – Antibiotics use, sedatives, muscle relaxants
Methods • Data regarding support for – respiratory and cardiovascular organ systems • Were recorded daily
• Vital status at 30 days was recorded – obtained from hospital records – Verified national database – causes of death were not recorded
Methods • Outcomes – Primary • vital status at 30 days,
– Secondary • all-cause mortality at the time of discharge ICU and hospital • duration of MV • use of – antimicrobial, sedative, vasoactive – neuromuscular-blocking drugs
Methods • Statistical Analysis – 401 patients TO provide a power of 80% • to identify a change of 10 percentage points • estimated rate of death of 45% in control group
• Analyses : intentionto-treat basis
Methods • chi-square tests used to – compare between group rates of death • at 30 days • Among patients in ICU and hospital settings
• They performed logistic regression – analysis of mortality after adjustment • study center, sex, Pao2 :Fio2 ratio • APACHE II
Results â&#x20AC;˘ Patients recruitment â&#x20AC;&#x201C; From December 7, 2007 to July 2012
Results â&#x20AC;˘ HFOV used for median 3 days in 388 patients â&#x20AC;&#x201C; Longest duration 24 days
Results • Neuromuscular-blocking drugs were used • a mean (±SD) of 2.0±3.4 days conventional ventilation group • for 2.5±3.5 days in the HFOV group (P=0.02).
• Sedative drugs • 8.5±6.9 days in the conventional • 9.4±7.2 days in the HFOV group (P=0.07)
• 17.6±8.8 ventilator-free days conventional • 17.1±8.6 ventilator-free days in HFOV
OUTCOMES • primary outcome – 166 of 398 patients (41.7%) in HFOV group – 163 of 397 patients (41.1%) in conventional group • absolute difference – 0.6 percentage points ([CI], −6.1 to 7.5).
OUTCOMES • After adjustment for study – center, sex, APACHE II score, – Pao2 Fio2 ratio
• the odds ratio for survival conventional ventilation group compared with HFOV – OR 1.03 (95% CI, 0.75 to 1.40; P=0.87)
OUTCOMES • rates of death – first discharge from ICU • 42.1% in the conventional GROUP • 44.1% in the HFOV group – absolute difference of 2.0 percentage points (P=0.57)
– first hospital discharge • 48.4% of patients in the conventional • 50.1% in the HFOV – difference of 1.7 percentage points (P=0.62).
OUTCOMES • There was no significant difference – patients received inotropic agents or pressor infusions – received antimicrobial drugs – The total duration of ICU stay – total durations of hospital stay
Discussion • THEY found – no significant between-group difference in mortality up to 30 days after randomization.
• The average Pao2 :Fio2 ratio identical to that reported in the recent systematic review of HFOV – Results are different if compared with that metanalysis • Wich showed reduced risk of death – risk ratio, 0.77; 95% CI, 0.61 to 0.98
Discussion • This study recruited more than twice the number of patients • Adding the OSCAR´S results to metanalysis – changes the estimated risk ratio • to 0.90 (95% CI, 0.76 to 1.07)
Discussion • In OSCAR Novalung R100 ventilator was used – SensorMedics 3100B ventilator was used in other studies • Is possible that this finding may produce differences
• There was no loss to follow-up • crossovers were minimal • study recruited 99.1% of the planned sample size
• In conclusion – a large effectiveness study – They din´t find any benefit or harm • From the use of HFOV in adult patients with ARDS