High flow nasal cannula: an alternative to continuous positive airway pressure in cats

Dear Editors,

We read with great interest the study by Di Bella et al published in JFMS, which describes the use of continuous positive airway pressure (CPAP) by a helmet in healthy cats under general anaesthesia. ¹ We agree with the authors that non-invasive ventilation is useful to prevent and treat respiratory dysfunctions in animals. Di Bella et al provided encouraging results on the use of CPAP in cats. However, the equipment used to deliver CPAP with a helmet interface was complex and evaluated on cats under general anaesthesia, raising questions on the safety of its use in cats with respiratory failure.

High flow nasal cannula (HFNC) therapy is increasingly used in human medicine, especially in infants, and it is trending towards replacing nasal CPAP as primary support in mild to moderate respiratory failure. ² HFNC is a device that allows the delivery of a humidified and heated gas with a higher flow than the inspiratory flow of the patient. ³ This technique presents several physiological benefits. It provides an oxygen reserve by making a washout of the pharyngeal cavity, and it can deliver a positive expiratory pressure (PEP) (Figure 1). In preterm infants, the level of PEP was estimated to be between 2 and 6 cmH₂O depending on the flow rate. ⁴ In dogs, Jagodich et al ⁵ showed that a CPAP level of around 5 cm H₂O was achieved by HFNC at a flow rate of 2 l/kg/min, with an improvement in oxygenation. These CPAP levels are in the same range as those used by Di Bella et al. ¹

We have been using HFNC as a primary respiratory support device for acute respiratory failure in both dogs and cats for 2 years in our intensive care unit. In a pilot study, we demonstrated that HFNC improves oxygenation parameters and is well tolerated in dyspnoeic dogs. ⁶ Our initial experiences in cats show that adequate placement of the nasal cannula does require sedation, but this technique is then well tolerated by the cat and does not necessitate further heavy sedation. Although these findings need to be confirmed by prospective studies, HFNC appears to be an interesting alternative to CPAP delivered by a helmet as it is usable in awake animals and does not limit access to the upper airway during respiratory support (Figure 1).

Figure 1

Physiological effect of high flow nasal cannula and an example of its use in a cat with moderate respiratory failure due to cardiogenic pulmonary oedema

Florent Baudin^1,2Céline Pouzot-Nevoret^2,3Leila Hocine^2,3Bernard Allaouchiche^2,41Service de réanimation pédiatrique, Hospices Civils de Lyon, Hôpital Femme Mère Enfant, France²Agressions Pulmonaires et Circulatoires dans le Sepsis (APCSe), VetAgro Sup, Université de Lyon, France³Intensive Care Unit (SIAMU), VetAgro Sup, Université de Lyon, France⁴Service de Réanimation, Hospices Civils de Lyon, Centre Hospitalier Lyon-Sud, France