Effects of High Flow Nasal Cannula Oxygen Therapy on Oxygenation in Dogs undergoing Diagnostic Bronchoscopy

Abstract

Hypoxaemia is a common complication in dogs undergoing bronchoscopy, and the options for adequate oxygen supplementation are often limited, particularly in small veterinary patients. High Flow Oxygen Therapy (HFOT) has been used successfully in human hypoxaemic patients to improve oxygenation in various settings, including during diagnostic and therapeutic bronchoscopy. The aim of this study was to evaluate the effect of HFOT on oxygenation in dogs undergoing bronchoscopy compared to a traditional oxygen supplementation method. Additionally, the study aimed to assess if HFOT is a safe method to use during bronchoscopy and to determine if complications would occur. Twenty privately owned dogs presented for diagnostic bronchoscopy were included in the study. Age and weight ranged from 1 to 13 years and 4.4 to 47.8 kg, respectively. All dogs were randomly assigned to receive either HFOT or traditional oxygen therapy (TOT) using nasal cannulas during the procedure. Arterial blood gas analyses were obtained for each patient at seven different predetermined time points: at baseline, after preoxygenation, after induction of anaesthesia, before and after bronchoalveolar lavage, at the end of the procedure, and one hour after the end of oxygen supplementation. In addition, thoracic radiographs were performed for each patient before and immediately after the bronchoscopy to assess the occurrence of complications such as air leak syndrome or aerophagia. Parametric and non-parametric statistical tests were used depending on data distribution to compare the partial pressure of oxygen at all time points between the group. Additionally, tracheal FiO2, calculated oxygen indices, and trend analysis of paO2 over time were evaluated. Finally, the occurrence and frequency of adverse effects were assessed using a Chi-square test. Overall, HFOT led to higher values of PaO2 in nearly all patients throughout the procedure, with fewer episodes of desaturation occurring compared to the TOT group. Statistical significance could be achieved for values obtained after preoxygenation and at the end of the procedure. Values obtained after BAL barely missed the statistically significant cut-off (P< 0.05). However, only one patient in the HFOT group experienced desaturation below 80 mmHg, and the lowest PaO2 experienced in the remaining dogs within the group was 117 mmHg. In comparison, five dogs in the HFOT group experienced hypoxaemia at least once during the procedure despite oxygen supplementation. Furthermore, a comparison of mean PaO2 values from preoxygenation to the end of the procedure showed a statistically significant difference between the groups. Visual graphical analysis also indicates an overall better performance of HFOT than TOT regarding oxygenation. Additionally, HFOT achieved statistically significantly higher tracheal FiO2 values than TOT. There were no serious adverse events related to HFOT, although several dogs in both groups experienced aerophagia to various degrees. However, none of the dogs required medical intervention to alleviate gaseous distension. In conclusion, HFOT is a safe oxygen supplementation method and can improve oxygenation in dogs undergoing bronchoscopy compared to traditional oxygen supplementation methods. HFOT can thus reduce and even prevent occurrences of life-threatening periods of hypoxaemia even during bronchoalveolar lavage sampling compared to TOT.