Comparative bench study evaluation of a modified snorkeling mask used during COVID-19 pandemic and standard interfaces for non-invasive ventilation.

PURPOSE: The aim of this bench study is to compare the standard NIV and nCPAP devices (Helmet, H; Full face mask, FFM) with a modified full face snorkeling mask used during COVID-19 pandemic. METHODS: A mannequin was connected to an active lung simulator. The inspiratory and expiratory variations in airways pressure observed with a high simulated effort, were determined relative to the preset CPAP level. NIV was applied in Pressure Support Mode at two simulated respiratory rates and two cycling-off flow thresholds. During the bench study, we measured the variables defining patient-ventilator interaction and performance. RESULTS: During nCPAP, the tested interfaces did not show significant differences in terms of ∆Pawi and ∆Pawe. During NIV, the snorkeling mask demonstrated a better patient-ventilator interaction compared to FFM, as shown by significantly shorter Pressurization Time and Expiratory Trigger Delay (p < 0.01), but no significant differences were found in terms of Inspiratory Trigger Delay and Time of Synchrony between the interfaces tested. At RR 20sim, the snorkeling mask presented the lower ΔPtrigger (p < 0.01), moreover during all the conditions tested the snorkeling mask showed the longer Pressure Time Product at 200, 300, and 500 ms compared to FFM (p < 0.01). A major limitation of snorkeling mask is that during NIV with this interface it is possible to reach maximum 18 cmH2O of peak inspiratory pressure. CONCLUSIONS: The modified snorkeling mask can be used as an acceptable alternative to other interfaces for both nCPAP and NIV in emergencies.

Comparative Evaluation of Two Different Post-Operative Analgesia after Hallux Valgus Correction in Day Surgery Patients.

INTRODUCTION: The aim of this study was the evaluation of two different techniques on post-operative analgesia and motor recovery after hallux valgus correction in one-day surgery patients. MATERIAL AND METHODS: We enrolled 26 patients scheduled for hallux valgus surgery and treated with the same surgical technique (SCARF osteotomy). After subgluteal sciatic nerve block with a short acting local anaesthetic (Mepivacaine 1.5%, 15ml), each patient received an ultrasound-guided Posterior Tibialis Nerve Block (PTNB) with Levobupivacaine 0.5% (7-8ml). We measured the postoperative intensity of pain using a Visual Analogue Scale (VAS), the consumption of oxycodone after operative treatment and the motor recovery. VAS was detected at baseline (time 0, before the surgery) and at 3, 6, 12 and 24 hours after the operative procedure (T1, T2, T3, T4 respectively). Control group of 26 patients were treated with another post-operative analgesia technique: local infiltration (Local Infiltration Anaesthesia, LIA) with Levobupivacaine 0.5% (15ml) performed by the surgeon. RESULTS: PTNB group showed a significant reduction of VAS score from the sixth hour after surgery compared to LIA group (p<0.028 at T2, p<0.05 at T3 and p<0.002 at T4, respectively). Instead, no significant differences were found in terms of post-operative oxycodone consumption and motor recovery after surgery.Conclusions: PTNB resulted in a valid alternative to LIA approach for post-operative pain control due to its better control of post-operative pain along the first 24 hours. In a multimodal pain management according to ERAS protocol, both PTNB and LIA should be considered as clinically effective analgesic techniques.

Exposure to noise during continuous positive airway pressure: influence of interfaces and delivery systems.

BACKGROUND: We measured noise intensity and perceived noisiness during continuous positive airway pressure (CPAP) performed with two interfaces (face-mask, helmet) and four delivery systems. METHODS: Eight healthy volunteers received CPAP in random order with: two systems provided with a flow generator using the Venturi effect and a mechanical expiratory valve (A: Venturi, Starmed; B: Whisperflow-2, Caradyne Ltd); one 'free-flow' system provided with high flow O(2) and air flowmeters, an inspiratory gas reservoir, and a water valve (C: CF800, Drägerwerk, AG); and a standard mechanical ventilator (Servoventilator 300, Siemens-Elema). Systems A, B, and C were tested with a face-mask and a helmet at a CPAP value of 10 cm H(2)O; the mechanical ventilator was only tested with the face mask. Noise intensity was measured with a sound-level meter. After each test, participants scored noisiness on a visual analog scale (VAS). RESULTS: The noise levels measured ranged from 57+/-11 dBA (mechanical ventilator plus mask) to 93+/-1 and 94+/-2 dBA (systems A and B plus helmet) and were significantly affected by CPAP systems (A and B noisier than C and D) and interfaces (helmet CPAP noisier than mask CPAP). Subjective evaluation showed that systems A and B plus helmet were perceived as noisier than system C plus mask or helmet. CONCLUSIONS: Maximum noise levels observed in this study may potentially cause patient discomfort. Less noisy CPAP systems (not using Venturi effect) and interfaces (facial mask better than helmet) should be preferred, particularly for long or nocturnal treatments.

Bench comparative evaluation of a new generation and standard helmet for delivering non-invasive ventilation.

OBJECTIVE: To evaluate the performance of a new helmet (NH) recently introduced into clinical use relative to that of the standard helmet (SH) in terms of delivering non-invasive continuous positive airway pressure (nCPAP) and pressure support ventilation (nPSV). DESIGN: This was a bench study using a mannequin connected to an active lung simulator. The SH was fastened to the mannequin by armpit braces, which are not needed to secure the NH. MEASUREMENTS: The inspiratory and expiratory variations in nCPAP delivered with two different simulated efforts (Pmus), were determined relative to the preset CPAP level. nPSV was applied at two simulated respiratory rates (RR) and two cycling-off flow thresholds. We measured inspiratory trigger delay (Delay trinsp), expiratory trigger delay (Delay trexp), time of synchrony (Time sync), trigger pressure drop (ΔP trigger), airway pressure-time product during the triggering phase (PTPt), the initial 200 ms from the onset of the ventilator pressurization (PTP 200), and the initial 300 and 500 ms from the onset of the simulated effort; this two latter parameters were expressed as the percentage of the area of ideal pressurization (PTP 300-index and PTP 500-index, respectively). RESULTS: In nCPAP, at both Pmus, the differences between the two interfaces at both Pmus were small and clinically irrelevant. In nPSV, regardless of the setting, NH resulted in significantly smaller trigger delays, ΔP trigger, and PTPt. Time sync, PTP 200, PTP 300-index, and PTP 500-index were also significantly higher with the NH compared to the SH, irrespective of the setting. CONCLUSIONS: Compared to the SH, the NH is equally effective in delivering nCPAP and more effective in delivering nPSV, and it is used to avoid the need for armpit braces.

A physiologic comparison of proportional assist ventilation with load-adjustable gain factors (PAV+) versus pressure support ventilation (PSV).

PURPOSE: To compare patient-ventilator interaction during PSV and PAV+ in patients that are difficult to wean. METHODS: This was a physiologic study involving 11 patients. During three consecutive trials (PSV first trial--PSV1, followed by PAV+, followed by a second PSV trial--PSV2, with the same settings as PSV1) we evaluated mechanical and patient respiratory pattern; inspiratory effort from excursion Pdi (swing(Pdi)), and pressure-time products of the transdiaphragmatic (PTPdi) pressures. Inspiratory (delay(trinsp)) and expiratory (delay(trexp)) trigger delays, time of synchrony (time(syn)), and asynchrony index (AI) were assessed. RESULTS: Compared to PAV+, during PSV trials, the mechanical inspiratory time (Ti(flow)) was significantly longer than patient inspiratory time (Ti(pat)) (p < 0.05); Ti(pat) showed a prolongation between PSV1 and PAV+, significant comparing PAV+ and PSV2 (p < 0.05). PAV+ significantly reduced delay(trexp) (p < 0.001). The portion of tidal volume (VT) delivered in phase with Ti(pat) (VT(pat)/VT(mecc)) was significantly higher during PAV+ (p < 0.01). The time of synchrony was significantly longer during PAV+ than during PSV (p < 0.001). During PSV 5 patients out of 11 showed an AI greater than 10%, whereas the AI was nil during PAV+. CONCLUSION: PAV+ improves patient-ventilator interaction, significantly reducing the incidence of end-expiratory asynchrony and increasing the time of synchrony.

Influence of ventilator settings on patient-ventilator synchrony during pressure support ventilation with different interfaces.

OBJECTIVE: To evaluate patient-ventilator interaction during pressure support ventilation (PSV) delivered with three interfaces [endotracheal tube (ET), face mask (FM), and helmet (H)] at different pressurization times (Time(press)), cycling-off flow thresholds (Tr(exp)), and respiratory rates (RR) in a bench study, and with FM and H in a healthy volunteers study. DESIGN: Bench study using a mannequin connected to an active lung simulator, and human study including eight healthy volunteers. MEASUREMENTS: PSV was delivered through the three interfaces with three different RR in the bench study, and through FM and H at two different RR in the human study. The mechanical and the neural RR, Ti, Te, inspiratory trigger delay (Delay(trinsp)), pressurization time, and expiratory trigger delay were randomly evaluated at various ventilator settings (Time(press)/Tr(exp): 50%/25%, default setting; 20%/5%, slow setting; 80%/60%, fast setting). RESULTS: Bench study: patient-ventilator synchrony was significantly better with ET, with lower Delay(trinsp) and higher time of assistance (P < 0.001); the combination Time(press)/Tr(exp) 20%/5% at RR 30 produced the worst interaction, with higher rate of wasted efforts (WE) compared with Time(press)/Tr(exp) 80%/60% (20%, 40%, and 50% of WE versus 0%, 16%, and 26% of all spontaneous breaths, with ET, FM, and H, respectively; P < 0.01). In both studies, compared with H, FM resulted in better synchrony. CONCLUSION: Patient-ventilator synchrony was significantly better with ET during the bench study; in the human study, FM outperformed H.