Clinical Study of Respiratory Mechanic in Horses Undergoing Volume Controlled Ventilation During Artroscopic Surgery

Abstract

During inhalation anesthesia and dorsal recumbence, horses often develop hypoxemia due to impairment of pulmonary gas exchange. The main cause of respiratory dysfunction in this species is attributed to postural changes associated with anesthesia, resulting in decreased functional residual capacity, imbalances in the ventilation/perfusion and atelectasis. The alveolar recruitment maneuvers (RM) are able to reverse the atelectasis, however, the maintenance of this effect depends on the institution of adequate positive end-expiratory pressure (PEEP), whose appropriate value has not been elucidated in this species. Therefore, the aim of this randomized and clinical study is to compare three values of PEEP after RM in 24 horses, of 350-550 kg, with the relationship between the partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2/FiO2) <300 during anesthesia with isoflurane. The animals are mechanically ventilated with an inspiration:expiration ratio of 1:3, tidal volume of 10-15 mL / kg and respiratory rate of 6-10 mpm, adjusted to maintain normocapnia. After the RM by increasing PEEP of 5 cmH2O at 5 every 3 breaths until PEEP of 20 cmH20, a PEEP of 15 cm H2O (PEEP Group 15, n = 8), 10 cmH2O (PEEP Group 10; n = 8) or 5 cmH2O (Group PEEP 5, n = 8) will be maintained until the end of anesthesia. Will be collected blood samples for arterial blood gas parameters and will be recorded cardiovascular and respiratory mechanics parameters before RM (baseline) and every 20 minutes after RM and institution of maintenance PEEP.