Impact of flow and temperature on non‐dyspnoeic dogs' tolerance undergoing high‐flow oxygen therapy

Abstract

Objectives To prospectively describe the impact of gas flow rate and temperature on dog's tolerance of high‐flow nasal oxygen therapy during recovery from anaesthesia, hypothesizing that higher flow rates and temperatures will decrease tolerance. Materials and Methods Twelve non‐dyspnoeic client‐owned dogs recovering from general anaesthesia were included in this study. After extubation, a nasal cannula was positioned and high‐flow nasal oxygen therapy was initiated. Two flow rates (two or four time the theoretical minute ventilation: HF2 and HF4), each of them combined with two temperatures (31 and 37°C: T31 and T37), were randomly applied (four conditions per dog). For each condition, cardiovascular and respiratory parameters (heart rate, respiratory rate, systolic arterial blood pressure and pulse oximeter oxygen saturation), sedation score and tolerance score were recorded at initiation (T0) and after 10 minutes of accommodation (T10). Results Sedation scores were not significantly different between the four conditions. Cardiovascular and respiratory parameters were not significantly different between any condition at both T0 and T10. Tolerance scores were good and not significantly different between any flow rate or temperature (HF2‐T31: 4 (2‐4), HF4‐T31: 4 (2‐4), HF2‐T37: 4 (2‐4), HF4‐T37: 4 (1‐4)). Clinical Significance The gas flow rates and temperatures studied have no impact on tolerance during the recovery period of non‐dyspnoeic dogs, and high‐flow nasal cannula is well tolerated. Further studies are required to confirm these results in dyspnoeic dogs.

Successful treatment of carbon monoxide toxicity with high flow nasal oxygen compared to mechanical ventilation

“…22 In CO toxicity from smoke inhalation or other combustion-based toxicities, neurologic signs can result from cyanide toxicity or methemoglobinemia secondary to inhaled noxious gases from melted plastics. 3,16 There was no evidence of methemoglobinemia or cyanide toxicity on arterial blood gas analysis for either patient.…”

“…10,11 Although nasal oxygen can provide an FiO 2 of 36%-77%, achieving a higher FiO 2 requires flow rates of 200 L/min which delivers cold, dry air that can irritate the oronasal mucosa, cause airway constriction, and trigger inflammation resulting in a low patient tolerance. 9,10,[15][16][17][18] Due to these findings, the nasal oxygen flow rate is often limited to a maximum rate of 4-5 L/min regardless of patient size. 18 While hyperbaric oxygen therapy is available in some institutions, this modality is not accessible in all regions, including at this facility.…”

“…Additionally, patients suffering from mucosal inflammation secondary to smoke inhalation likely would benefit from the superior humidification of HFNO. 3,16 …”

“…[4][5][6][7][8] Additionally, patients suffering from mucosal inflammation secondary to smoke inhalation likely would benefit from the superior humidification of HFNO. 3,16 In this case report, one patient was placed on MV due to the severity of neurologic signs and overall respiratory distress. The second patient would have otherwise been placed on the ventilator had multiple machines been available.…”

“…Oxygen cages can be inefficient and often cannot achieve an FiO 2 > 40%–60%, while flow‐by oxygen and face masks typically provide an FiO 2 of 24%–45% 10,11 . Although nasal oxygen can provide an FiO 2 of 36%–77%, achieving a higher FiO 2 requires flow rates of 200 L/min which delivers cold, dry air that can irritate the oronasal mucosa, cause airway constriction, and trigger inflammation resulting in a low patient tolerance 9,10,15–18 . Due to these findings, the nasal oxygen flow rate is often limited to a maximum rate of 4–5 L/min regardless of patient size 18 …”