Multiple Mechanical Ventilation: historical review and cost analysis

In times of crisis in public health where the resources available in the hospital network are scarce and these must be used to the fullest, innovative ideas arise, which allow multiplying the use of existing resources, as artificial mechanical ventilators can be. These can be used in more than one patient, by attaching a device to distribute the mixture of air and oxygen from the ventilator being used simultaneously (multiple mechanical ventilation). This idea, although innovative, has generated controversy among the medical community, as many fear for the safety of their patients, because attaching such devices to the ventilator loses control over the mechanical ventilation variables of each patient and can only maintain general vigilance over the ventilator. These misgivings about the device have led several researchers to take on the task of verifying the reliability of this flow splitter connector. It is for this reason that this article presents a thorough review of the studies carried out on the subject and additionally shows an analysis of comparative costs between the acquisition of a mechanical ventilator and the flow division system.

Simultaneous ventilation in the Covid-19 pandemic. A bench study

COVID-19 pandemic sets the healthcare system to a shortage of ventilators. We aimed at assessing tidal volume (VT) delivery and air recirculation during expiration when one ventilator is divided into 2 test-lungs. The study was performed in a research laboratory in a medical ICU of a University hospital. An ICU (V500) and a lower-level ventilator (Elisée 350) were attached to two test-lungs (QuickLung) through a dedicated flow-splitter. A 50 mL/cmH2O Compliance (C) and 5 cmH2O/L/s Resistance (R) were set in both A and B test-lungs (A C50R5 / B C50R5, step1), A C50-R20 / B C20-R20 (step 2), A C20-R20 / B C10-R20 (step 3), and A C50-R20 / B C20-R5 (step 4). Each ventilator was set in volume and pressure control mode to deliver 800mL VT. We assessed VT from a pneumotachograph placed immediately before each lung, pendelluft air, and expiratory resistance (circuit and valve). Values are median (1st-3rd quartiles) and compared between ventilators by non-parametric tests. Between Elisée 350 and V500 in volume control VT in A/B test- lungs were 381/387 vs. 412/433 mL in step 1, 501/270 vs. 492/370 mL in step 2, 509/237 vs. 496/332 mL in step 3, and 496/281 vs. 480/329 mL in step 4. In pressure control the corresponding values were 373/336 vs. 430/414 mL, 416/185 vs. 322/234 mL, 193/108 vs. 176/ 92 mL and 422/201 vs. 481/329mL, respectively (P<0.001 between ventilators at each step for each volume). Pendelluft air volume ranged between 0.7 to 37.8 ml and negatively correlated with expiratory resistance in steps 2 and 3. The lower-level ventilator performed closely to the ICU ventilator. In the clinical setting, these findings suggest that, due to dependence of VT to C, pressure control should be preferred to maintain adequate VT at least in one patient when C and/or R changes abruptly and monitoring of VT should be done carefully. Increasing expiratory resistance should reduce pendelluft volume.

Sharing ventilators in the Covid-19 pandemics. A bench study

COVID-19 pandemics sets the healthcare system to a shortage of ventilators. We aimed at assessing tidal volume (VT) delivery and air recirculation during expiration when one ventilator is divided into 2 patients. The study was performed in a research laboratory in a medical ICU of a University hospital. An ICU-dedicated (V500) and a lower-level ventilator (Elisée 350) were attached to two test-lungs (QuickLung) through a dedicated flow-splitter. A 50 mL/cmH2O Compliance (C) and 5 cmH2O/L/s Resistance (R) were set in both A and B lungs (step1), C50R20 in A / C20R20 in B (step 2), C20R20 in A / C10R20 in B (step 3), and C50R20 in A / C20R5 in B (step 4). Each ventilator was set in volume and pressure control mode to deliver 0.8L VT. We assessed VT from a pneumotachograph placed immediately before each lung, rebreathed volume, and expiratory resistance (circuit and valve). Values are median (1st-3rd quartiles) and compared between ventilators by non-parametric tests. Between Elisée 350 and V500 in volume control VT in A/B patients were 0.381/0.387 vs. 0.412/0.433L in step 1, 0.501/0.270 vs. 0.492/0.370L in step 2, 0.509/0.237 vs. 0.496/0.332L in step 3, and 0.496/0.281 vs. 0.480/0.329L in step 4. In pressure control the corresponding values were 0.373/0.336 vs. 0.430/0.414L, 0.416/0.185/0.322/0.234L, 0.193/0.108 vs. 0.176/0.092L and 0.422/0.201 vs. 0.481/0.329L, respectively (P<0.001 between ventilators at each step for each volume). Rebreathed air volume ranged between 0.7 to 37.8 ml and negatively correlated with expiratory resistance in steps 2 and 3. The lower-level ventilator performed closely to the ICU-dedicated ventilator. Due to dependence of VT to C pressure control should be used to maintain adequate VT at least in one patient when C and/or R changes abruptly and monitoring of VT should be done carefully. Increasing expiratory resistance should reduce rebreathed volume.

Full-Scale Fairing Qualification Tests

Production risers as well as drilling risers are often exposed to ocean currents. Vortex-induced vibrations (VIVs) have been observed in the field and can cause fatigue failure and excessive drag on the riser. In order to suppress VIV, fairings are often used. This paper presents qualification tests for two types of fairings: the short-crab claw (SCC) fairings and the AIMS dual flow splitter (ADFS) fairings. The short-crab claw fairing design is a novel design patented by the Norwegian deepwater project (NDP). As will be detailed in this paper, both the SCC and ADFS designs offer very low drag, completely suppress VIV, and are effective even when they are in tandem. A model test campaign was undertaken in the 200-m towing tank facility at the ocean, coastal, and river engineering in St. John's, NF, Canada. A rigid pipe with a diameter of 0.3556 m (14 in) was utilized for the experiments. This corresponds to prototype size for a production riser and a 1:3.8 scaled model for a 1.3716 m (54 in) drilling riser. Given that these tests were conducted at prototype scale, they were used to qualify the fairings for field deployment. Both fairings (SCC and ADFS) were very effective in suppressing VIV and reducing drag. The ADFS fairings are most effective for a span to diameter ratio of 1.75. For all fairing geometries, it was found that a small taper increases the fairing effectiveness considerably.