respiratory drive and inspiratory effort in covid-19 associated ards

Conditions: ARDS, Human; COVID-19 Respiratory Infection; COVID-19 Acute Respiratory Distress Syndrome; Respiratory Effort-Related Arousal; Weaning Failure; Mechanical Ventilation Complication; Acute Hypoxic Respiratory Failure

Summary: data comparing respiratory drive and effort in critically ill patients with acute respiratory distress syndrome associated to different severity of covid-19 penumonia (cards) and to other risk factors are lacking. objectives: to assess respiratory drive and effort of cards patients at the first transition from controlled to assisted spontaneous breathing. the second aim was the rate of a composite outcome including the need 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.

Eligibility criteria:
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

Keywords: ards covid-19 weaning from mechanical ventilation respiratory drive inspiratory effort respiratory monitoring