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Objective: To evaluate the effect of 5 cm H 2 O of continuous positive airway pressure (CPAP) on laryngeal size in spontaneously breathing anesthetized dogs via computed tomography (CT)., Design: Prospective, randomized, cross-over clinical study., Setting: University teaching hospital and referral private practice., Animals: Eight healthy client-owned dogs undergoing CT., Interventions: Dogs were sedated with acepromazine 20 μg/kg IM and induced with fentanyl 2 μg/kg and propofol 3-5 mg/kg IV before being maintained on fentanyl (5 μg/kg/h) and propofol (0.3 mg/kg/min) constant rate infusion. Dogs received an air/oxygen mixture with (CPAP) and without (NO-CPAP) 5 cm H 2 O of CPAP in a random order. Each study step lasted 15 minutes., Measurements and Main Results: Ten minutes after the beginning of each study period, a CT scan of the laryngeal region was obtained at end-expiration. CT images were analyzed to determine the laryngeal cross-sectional area (CSA; cm 2 ), total volume (V TOT ; cm 3 ), and laterolateral and dorsoventral diameters (D LL and D DV , respectively; cm). Differences between the 2 treatments were analyzed with t-test for paired data (P < 0.05). Compared to the NO-CPAP, during CPAP the CSA increased by 53.3 ± 23.1% (ie, from 3.3 ± 0.8 to 5.1 ± 1.3 cm 2 , P = 0.0004), V TOT increased by 52.4 ± 13.6% (from 6.2 ± 1.7 to 9.4 ± 2.4 cm 3 , P < 0.0001), and D LL and D DV were 55.5 ± 13.3% (3.6 ± 0.8 vs 2.4 ± 0.5 cm, P = 0.006) and 20.3 ± 8.8% larger (3.2 ± 0.7 vs 2.7 ± 0.6 cm, P = 0.0002), respectively., Conclusions: Laryngeal volume and cross sectional area increased during the application of 5 cm H 2 O of helmet CPAP in spontaneously breathing anesthetized dogs., (© Veterinary Emergency and Critical Care Society 2020.)

Objective: To evaluate the effects of positive end-expiratory pressure (PEEP) alone and PEEP preceded by lung recruitment manoeuvre (LRM) on lung volumes and respiratory system mechanics in healthy horses undergoing general anaesthesia., Study Design: Controlled, prospective clinical study., Animals: A group of 15 horses undergoing arthroscopy., Methods: Following anaesthetic induction, initial ventilatory settings were: tidal volume 15 mL kg -1 , inspiratory:expiratory ratio 1:2, respiratory rate to maintain end-tidal CO 2 between 5.3-6.6 kPa (40-50 mmHg). The following settings were implemented sequentially: zero PEEP (ZEEP); PEEP 10 cmH 2 O (PEEP); LRM (50 cmH 2 O for 20 seconds) followed by 10 cmH 2 O of PEEP (LRM + PEEP). Static compliance (C st ), driving pressure, delta end-expiratory (ΔEELV) and recruited lung volumes (RLV) were obtained 30 minutes after initiating each ventilatory strategy. Data were analyzed with paired t test or analysis of variance followed by Tukey's post hoc test. Data are shown as mean ± standard deviation; p < 0.05 was considered significant., Results: PEEP induced ΔEELV of 6.68 ± 3.36 mL kg -1 ; ΔEELV during LRM + PEEP was 14.28 ± 5.59 mL kg -1 (p < 0.0001). The RLV was greater during the LRM + PEEP phase (12.30 ± 5.85 mL kg -1 ) than during PEEP (4.47 ± 3.97 mL kg -1 ; p < 0.0001). The C st was unchanged from ZEEP to PEEP (0.75 ± 0.21 and 0.85 ± 0.22 mL cmH 2 O -1 kg -1 , respectively, p = 0.36) but increased using LRM + PEEP (1.11 ± 0.25 mL cmH 2 O -1 kg -1 , p = 0.0004). Driving pressure was lower during LRM + PEEP than during PEEP and ZEEP (16 ± 2, 19 ± 2 and 21 ± 4 cmH 2 O, respectively, p < 0.0001)., Conclusions and Clinical Relevance: Unlike PEEP alone, PEEP preceded by LRM increased RLV and C st and reduced driving pressure in horses under anaesthesia., (Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Purpose: High-flow oxygen therapy delivered through nasal cannulae improves oxygenation and decreases work of breathing in critically ill patients. Little is known of the physiological effects of high-flow oxygen therapy applied to the tracheostomy cannula (T-HF). In this study, we compared the effects of T-HF or conventional low-flow oxygen therapy (conventional O 2 ) on neuro-ventilatory drive, work of breathing, respiratory rate (RR) and gas exchange, in a mixed population of tracheostomized patients at high risk of weaning failure., Methods: This was a single-center, unblinded, cross-over study on fourteen patients. After disconnection from the ventilator, each patient received two 1-h periods of T-HF (T-HF1 and T-HF2) alternated with 1 h of conventional O 2 . The inspiratory oxygen fraction was titrated to achieve an arterial O 2 saturation target of 94-98% (88-92% in COPD patients). We recorded neuro-ventilatory drive (electrical diaphragmatic activity, EAdi), work of breathing (inspiratory muscular pressure-time product per breath and per minute, PTP musc/b and PTP musc/min , respectively) respiratory rate and arterial blood gases., Results: The EAdi peak remained unchanged (mean ± SD) in the T-HF1, conventional O 2 and T-HF2 study periods (8.8 ± 4.3 μV vs 8.9 ± 4.8 μV vs 9.0 ± 4.1 μV, respectively, p = 0.99). Similarly, PTP musc/b and PTP musc/min , RR and gas exchange remained unchanged., Conclusions: In tracheostomized patients at high risk of weaning failure from mechanical ventilation, T-HF did not improve neuro-ventilatory drive, work of breathing, respiratory rate and gas exchange compared with conventional O 2 after disconnection from the ventilator. The present findings might suggest that physiological effects of high-flow therapy through tracheostomy substantially differ from nasal high flow.

Background: The physiological effects of high-flow nasal cannula O 2 therapy (HFNC) have been evaluated mainly in patients with hypoxemic respiratory failure. In this study, we compared the effects of HFNC and conventional low-flow O 2 therapy on the neuroventilatory drive and work of breathing postextubation in patients with a background of chronic obstructive pulmonary disease (COPD) who had received mechanical ventilation for hypercapnic respiratory failure., Methods: This was a single center, unblinded, cross-over study on 14 postextubation COPD patients who were recovering from an episode of acute hypercapnic respiratory failure of various etiologies. After extubation, each patient received two 1-h periods of HFNC (HFNC1 and HFNC2) alternated with 1 h of conventional low-flow O 2 therapy via a face mask. The inspiratory fraction of oxygen was titrated to achieve an arterial O 2 saturation target of 88-92%. Gas exchange, breathing pattern, neuroventilatory drive (electrical diaphragmatic activity (EAdi)) and work of breathing (inspiratory trans-diaphragmatic pressure-time product per minute (PTP DI/min )) were recorded., Results: EAdi peak increased from a mean (±SD) of 15.4 ± 6.4 to 23.6 ± 10.5 μV switching from HFNC1 to conventional O 2 , and then returned to 15.2 ± 6.4 μV during HFNC2 (conventional O 2 : p < 0.05 versus HFNC1 and HFNC2). Similarly, the PTP DI/min increased from 135 ± 60 to 211 ± 70 cmH 2 O/s/min, and then decreased again during HFNC2 to 132 ± 56 (conventional O 2 : p < 0.05 versus HFNC1 and HFNC2)., Conclusions: In patients with COPD, the application of HFNC postextubation significantly decreased the neuroventilatory drive and work of breathing compared with conventional O 2 therapy.