Efficacy of an alveolar recruitment maneuver for improving gas exchange and pulmonary mechanics in anesthetized horses ventilated with oxygen or a helium-oxygen mixture

Abstract

OBJECTIVE To evaluate efficacy of an alveolar recruitment maneuver (ARM) with positive end-expiratory pressures (PEEPs) in anesthetized horses ventilated with oxygen or heliox (70% helium and 30% oxygen). ANIMALS 6 healthy adult horses. PROCEDURES In a randomized crossover study, horses were anesthetized and positioned in dorsal recumbency. Volume-controlled ventilation was performed with heliox or oxygen (fraction of inspired oxygen [Fio2] > 90%). Sixty minutes after mechanical ventilation commenced, an ARM with PEEP (0 to 30 cm H2O in steps of 5 cm H2O every 5 minutes, followed by incremental steps back to 0 cm H2O) was performed. Peak inspiratory pressure, dynamic lung compliance (Cdyn), and Pao2 were measured during each PEEP. Indices of pulmonary oxygen exchange and alveolar dead space were calculated. Variables were compared with baseline values (PEEP, 0 cm H2O) and between ventilation gases by use of repeated-measures ANOVAs. RESULTS For both ventilation gases, ARM significantly increased pulmonary oxygen exchange indices and Cdyn. Mean ± SD Cdyn (506 ± 35 mL/cm H2O) and Pao2-to-Fio2 ratio (439 ± 36) were significantly higher and alveolar-arterial difference in Pao2 (38 ± 11 mm Hg) was significantly lower for heliox, compared with values for oxygen (357 ± 50 mL/cm H2O, 380 ± 92, and 266 ± 88 mm Hg, respectively). CONCLUSIONS AND CLINICAL RELEVANCE An ARM in isoflurane-anesthetized horses ventilated with heliox significantly improved pulmonary oxygen exchange and respiratory mechanics by decreasing resistive properties of the respiratory system and reducing turbulent gas flow in small airways.

Evaluation of the Effect of the Inspired Oxygen Fraction on Blood Oxygenation during Inhalant Anaesthesia in Horses: A Systematic Review with Meta-Analysis

“…Fourteen studies were excluded after critically evaluating them: one review [ 29 ]; five due to missing control/intervention allocation of the animals [ 30 , 31 , 32 , 33 , 34 ]; two studies [ 20 , 35 ] because injectable agents were used for the maintenance of anaesthesia; one with an FIO 2 of the interventional group above our pre-defined threshold of 0.6 [ 36 ]; and one retrospective study with an average FIO 2 of the control group below our threshold of 0.8 [ 37 ]. Furthermore, three more studies were excluded as other gases than nitrogen were used to decrease the FIO 2 : in two studies [ 21 , 38 ] the intervention group received a mixture of oxygen with helium, and in one study [ 39 ] the inspired mixture consisted of oxygen and nitrous oxide. Finally, one study [ 40 ] had an unorthodox study design: 24 animals were used to compare the influence of a delivered oxygen fraction (FdO 2 ) of 1.0 and 0.6 during isoflurane anaesthesia.…”

“…Moreover, we excluded studies where the inspired gas mixture consisted of gas other than oxygen with medical air or nitrogen. For instance, we excluded two studies with helium in the inspired mixture [ 21 , 38 ], because of the specific physical properties of helium. Interestingly, in both studies, PaO 2 and P( a -a)O 2 were higher (P( a -a)O 2 (non-significantly in [ 38 ]) with a high F i O 2 , whereas the PaO 2 /F i O 2 ratio was lower.…”

“…For instance, we excluded two studies with helium in the inspired mixture [ 21 , 38 ], because of the specific physical properties of helium. Interestingly, in both studies, PaO 2 and P( a -a)O 2 were higher (P( a -a)O 2 (non-significantly in [ 38 ]) with a high F i O 2 , whereas the PaO 2 /F i O 2 ratio was lower. Moreover, we excluded another study [ 39 ] with N 2 O in the mixture, an agent with special anaesthetic and analgesic properties, which may have affected pulmonary function.…”

Efficacy of using helium-oxygen mixture in the intensive care of pneumonia in adult patients: a systematic review and meta-analysis

“…Лечение дыхательной недо статочности при пневмонии, вызванной новой коронавирусной инфек цией COVID-19, -пока еще нере шенная проблема, требующая комплексного подхода и разработки новых методов, расширяющих диапазон возможнос тей современной терапии. Благодаря своим физическим свой ствам КГС может улучшить оксигенацию, работу дыхания и, возможно, избежать необходимости интубации и ИВЛ у пациентов с дыхательной недостаточностью [2,6,13]. Следует отметить, что проблема использования КГС при лечении взрослых пациентов с вирусной и бактериальной пневмо нией освещена недостаточно.…”

Continuous measurement of arterial oxygenation in mechanically ventilated horses

“…7,8 Ventilatory strategies including the application of positive end-expiratory pressure (PEEP) and alveolar recruitment manoeuvres can be used to reduce atelectasis and improve V ̇/Q ̇ matching, potentially minimising hypoxaemia in anaesthetised horses. [9][10][11] However, the treatment of hypoxaemia in the anaesthetised horse can be extremely challenging and unsuccessful. 12 Intermittent arterial blood sampling for the spot analysis of arterial partial pressure of oxygen (PaO 2 ) is the current clinical standard to monitor arterial oxygenation in horses under GA.…”