Data comparing respiratory drive and effort in critically ill patients with acuterespiratory distress syndrome associated to different severity of COVID-19 penumonia(CARDS) and to other risk factors are lacking. Objectives: To assess respiratory driveand effort of CARDS patients at the first transition from controlled to assistedspontaneous breathing. The second aim was the rate of a composite outcome including theneed of higher level of sedation
Multicenter cohort study in four Italian ICU including adults with moderate and severe
CARDS (PaO2/FiO2 <100 mmHg) at ICU admission. An historical cohort of patients with ARDS
from various etiologies used for comparison. Respiratory drive (P0.1), diaphragm
electrical activity (EAdi), inspiratory effort derived from EAdi (∆PmusEAdi) and from
deflection in airway pressure occluded (ΔPocc) (PmusΔPocc), dynamic transpulmonary
driving pressure (ΔPL,dyn, the difference between peak and end-expiratory transpulmonary
pressure) measured under assisted ventilation.
The main ventilatory pattern variables:
- Airway Occlusion Pressure (P0.1): Measurement of the decrease in airway pressure
during an end-expiratory occlusion.
- Pmus-EAdi-derived (∆Pmus, EAdi): Measurement of the pressure generated by the
respiratory muscles during inspiration derived by electrical activity of the
diaphragm measurements.
- Transpulmonary pressure EAdi-derived (∆Plung,dyn): difference between peak and
end-expiratory transpulmonary pressure .
- Occlusive Pressure Difference (∆Pocc): Evaluation of the pressure difference between
the initial and final airway opening during inspiration.
- Pmus-∆Pocc-derived (∆Pmus, ∆Pocc): Measurement of the pressure generated by the
respiratory muscles during inspiration derived by ∆Pocc (∆Pocc*0.75)
- Transpulmonary driving pressure ∆Pocc derived (∆Plung, ∆Pocc): calculated as (Peak
airway pressure -PEEP) - 2/3 * ∆Pocc
- Diaphragmatic Electrical Activity (EAdi): Recording of the electrical activity of
the diaphragm.
- Peak EAdi (EAdiPEAK): Determination of the highest recorded value of diaphragmatic
electrical activity.
- Pressure time product of the trans-diaphragmatic pressure per breath and per
minute(PTP/min): the integral of Pmusc-EAdi-derived during inspiration per breath.
- Inspiratory Delay (ID): Assessment of the time delay between the start of neural
inspiration and the onset of mechanical ventilation.
- Neuro-ventilatory Efficiency (NVE): Measurement of the efficiency of the neural
drive to the respiratory muscles.
- Peak Airway Opening Pressure (PawPEAK): Measurement of the peak pressure in the
airway during inspiration.
- Inspiratory Pressure-Time Product (PmusEAdi/b): Calculation of the work of breathing
by integrating the product of diaphragmatic electrical activity and the change in
airway pressure during inspiration.
- Tidal Volume (VT): Measurement of the volume of air inspired and expired during each
breath.
- Respiratory Rate: Calculation of the number of breaths per minute delivered by the
mechanical ventilator.
- Inspiratory and Expiratory Time (Ti,MECH and Te,MECH): Determination of the duration
of mechanical inspiration and expiration.
- Inspiratory Duty Cycle (TI/TTOT-neur): Calculation of the ratio of inspiratory time
to total respiratory cycle time based on neural inspiration.
Other: Respiratory drive and effort assessment
The use of a neurally-adjusted ventilatory assist catheter, the measurement of electrical
activity of the diaphragm, ∆Pocc, P0.1, and other ventilatory parameters to assess
respiratory drive and effort in three cohorts of patients
Inclusion Criteria:
- Patients with a diagnosis of acute respiratory distress syndrome based on the Berlin
criteria.
- Patients with ARDS due to confirmed COVID-19 through real-time RT-PCR on
nasopharyngeal swabs or lower respiratory tract aspirates.
- Patients who had received invasive mechanical ventilation for more than 72 hours.
- Patients who were candidates for assisted ventilation.
Readiness for assisted ventilation, which was defined by the following criteria:
1. Improvement of the condition leading to acute respiratory failure.
2. Positive end-expiratory pressure lower than 10 cmH2O and inspiratory oxygen fraction
lower than 0.5.
3. Richmond agitation sedation scale score between 0 and -3.
4. Ability to trigger the ventilator, i.e., decrease pressure airway opening by more
than 3-4 cmH2O during a brief (5-10 seconds) end-expiratory occlusion test.
- Hemodynamic stability without vasopressor or inotropes, except for dobutamine
and norepinephrine infusion below certain thresholds (dobutamine <5
gamma/Kg/min and norepinephrine <0.3 gamma/Kg/min).
- Normothermia.
Exclusion Criteria:
- Patients affected by neurological or neuromuscular pathology and/or known phrenic
nerve dysfunction.
- Patients with any contraindication to the insertion of a nasogastric tube, such as
recent upper gastrointestinal surgery or esophageal varices.
- Patients < 18 years old
S.C. Anestesia e Rianimazione 1U A.O.U.- Città della Salute e della Scienza, P.O. Molinette Corso Bramante 88-90
Turin 3165524, Italy
Vito Fanelli, MD, PhD, Principal Investigator
University of Turin, Italy