Comparison of the effect of oxygen supplementation using flow-by or a face mask on the partial pressure of arterial oxygen in sedated dogs

Oxygen Reserve Index as a Tool to Monitor Four Techniques of Oxygen Supplementation at Different Flow Rates in Dogs Sedated with Dexmedetomidine and an Opioid

Respiratory dysfunction often decreases arterial oxygen content. Four common oxygen delivery techniques-flow-by, nasal prongs, a tight-vented mask, and a tight mask connected to a Venturi valve-were evaluated for their effectiveness in increasing the oxygen reserve index (ORi), a dimensionless index of oxygen content that provides additional information compared to traditional pulse oximetry (SpO2) during hyperoxia (PaO2 100-200 mmHg), and that ranges from 0 to 1. Thirty-two dogs sedated with dexmedetomidine and an opioid were evenly divided into four groups based on the technique for oxygen administration. Each dog received oxygen at 1, 2, and 3 L/min by a single technique, and the amount of inhaled oxygen (FiO2) was measured at the level of the cervical trachea. At each flow rate, ORi and SpO2 were recorded. The flow-by method minimally increased the FiO2, and ORi reached its highest value only in 3 out of 8 dogs at the maximum flow rate. Other methods exhibited direct correlations between the oxygen flow rate and ORi (p < 0.001). These methods effectively increased FiO2 and ORi, with over half of the values exceeding 40% and 0.4, respectively. The tight-vented mask showed variable increases in FiO2, ranging between 22 and 90%. Despite method-dependent variations, all devices increased SpO2 > 98% as the FiO2 increased (p = 0.002). In conclusion, nasal prongs and the mask connected to the Venturi valve showed the highest correlation between the oxygen flow rate and the ORi. These results suggest that using these two techniques in conjunction with ORI can help in optimizing oxygen therapy.

Oxygen delivery by mask improves the PaO2 of pregnant ewes during short term anaesthesia for caesarean delivery of preterm lambs

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Pregnant sheep are a common model for research focused on the preterm foetus.

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In some studies prompt caesarean delivery of the foetus is performed and maternal anaesthesia is managed to facilitate rapid delivery.

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As a result oxygen may not be provided to the ewe during anaesthesia.

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A simple and effective approach is to provide oxygen by facemask.

The aim of this study was to determine if oxygen supplementation improved the PaO₂ of pregnant ewes during short anaesthesia, when compared to a previous study where oxygen was not provided (Musk and Kemp, 2018). Twenty-six pregnant Merino cross ewes at 121–123 days of gestation were anaesthetised with intravenous midazolam and ketamine for subarachnoid administration of 60 mg of lignocaine and caesarean delivery of the preterm lamb. 100% oxygen was administered to the ewe by a face mask. Arterial blood samples were collected from the ewe immediately after delivery of the foetus. The ewes weighed 60.7 ± 5.5 kg and received 0.51 (0.47–0.58) mg/kg of midazolam and 10.3 (9.4–11.6) mg/kg of ketamine intravenously. The PaO₂ of ewes receiving oxygen by face mask was higher than previously reported [92.6 ± 44.0 mmHg compared to 45.2 ± 11.8 mmHg (Musk and Kemp, 2018) (p = 0.0007)]. Oxygen delivery by mask improved the PaO₂ of pregnant ewes during short term anaesthesia.

Comparison of CPAP and oxygen therapy for treatment of postoperative hypoxaemia in dogs

OBJECTIVE

To compare 5 cmH₂ O of continuous positive airway pressure with oxygen therapy in dogs recovering from general anaesthesia with low SpO₂ values. continuous positive airway pressure is more effective than oxygen therapy in restoring normoxaemia (SpO₂ ≥95%).

MATERIALS AND METHODS

Prospectively, dogs recovering from anaesthesia, with SpO₂ <95% after extubation (T0), were randomised and treated with continuous positive airway pressure (FiO₂ 0.21) or oxygen (O₂ ; FiO₂ 0.35-0.40) therapy. Dogs were monitored with SpO₂ every 15 minutes for 1 hour (T15, T30, T45, T60). Data from normoxaemic dogs (SpO₂ >95%) were used as control (CTR).

RESULTS

Of the 42 dogs enrolled, 34 completed the study. Eleven dogs were treated with O₂ , 10 with continuous positive airway pressure and 13 were CTR. The SpO₂ values at T0 were similar in the continuous positive airway pressure and O₂ groups and were lower than in the CTR group. At T15, T30, T45 and T60, the SpO₂ values in the continuous positive airway pressure group were higher than at T0; these were similar to those of the CTR group at the same time-points. In the O₂ group, SpO₂ values were significantly higher at T45 and T60 than at T0; 45.5% of dogs became normoxaemic at T45 and the remaining dogs became normoxaemic at T60. The average time to reach normoxaemia in the O₂ group (53.1±7.3 minutes) was longer than in the continuous positive airway pressure group (15.0±0.0 minutes).

CLINICAL SIGNIFICANCE

In dogs recovering from general anaesthesia with pulmonary gas exchange impairment, normoxaemia is restored more effectively and rapidly by using continuous positive airway pressure than by oxygen therapy.

Respiratory Emergencies

Respiratory distress is commonly seen in dogs and cats presenting to the emergency room. Rapid identification of respiratory difficulty with strategic stabilization and diagnostic efforts are warranted to maximize patient outcome. This article focuses on the relevant anatomy and physiology of the respiratory system and the clinical recognition, stabilization, and initial diagnostic planning for small animal patients that present for respiratory emergencies.