Effects of a demand valve on pulmonary ventilation in spontaneously breathing, anaesthetised horses

Section: If Necessary Ventilation Can Be Controlled By Administeringmentioning

confidence: 99%

Anaesthetic emergencies and complications: Part 1

Grubb

Muir

2010

“…Ten out of 60 horses developed pulmonary oedema of which three ended fatally (Tidwell et al 2002). Unsuitable or misused equipment may also lead to pulmonary oedema: demand valves that require high inspiratory pressures may increase airway pressure and the risk of pulmonary oedema (Watney et al 1985;Johnson et al 1994).…”

Section: Pulmonary Oedema and Upper Airway Obstructionmentioning

confidence: 99%

Mortality and morbidity in equine anaesthesia

Deutsch

Taylor

2021

Equine peri-anaesthetic mortality and morbidity are of interest to anaesthetists, practitioners, horse owners and insurance companies. The largest prospective study, 'The Confidential Enquiry into Perioperative Equine Fatalities' (CEPEF) was conducted more than 20 years ago. It included over 40,000 horses from multiple centres and reported mortality to be 1.9% that decreased to 0.9% when only elective cases were considered. This is in stark contrast to mortality rates in small animal (dogs: 0.17%, cats: 0.24%) and human anaesthesia (0.04-7/10,000). In spite of developments in understanding the pathophysiology of equine anaesthesia mortality has not decreased in the intervening years. The main contributors to peri-anaesthetic equine mortality are cardiac arrest, fractures and myopathy or neuropathy. Spinal cord myelopathy and cerebral necrosis are less common. Malignant hyperthermia and hyperkalaemic periodic paralysis are diseases associated with genetic mutations that can be triggered during general anaesthesia and may be fatal if not recognised and treated immediately. Morbidities are reported less frequently, presumably because often they do not cause permanent harm and may resolve within a short period of time. Complications in equine anaesthesia are numerous and include injuries at induction and recovery, damage to the airway associated with orotracheal or nasotracheal intubation, post-anaesthetic myopathy or neuropathy, regurgitation and aspiration of stomach contents, ocular injuries and complications associated with intravascular cannulation. Hypotension, hypoventilation, hypoxaemia, hypothermia and dysrhythmias may occur both during the maintenance phase of anaesthesia but also in recovery. Airway obstruction during recovery has repeatedly been reported over the years as causing pulmonary oedema, which is often fatal if the airway is not restored extremely quickly. This review summarises the literature on the risk of mortality and morbidity. Information has been gathered from single case reports as well as larger research studies.

“…Demand valves can be used during spontaneous breathing (SB), where the horse opens the valve by creating a negative pressure during inspiration. However, this is likely to result in increased resistance to inspiration, which would drastically increase the work of breathing (Watney et al 1985). Additionally, the horse's spontaneous inspiratory flow may potentially be greater than the demand valve's flow.…”

Section: Demand Valvementioning

confidence: 99%

“…However, this is likely to result in increased resistance to inspiration, which would drastically increase the work of breathing (Watney et al . 1985). Additionally, the horse's spontaneous inspiratory flow may potentially be greater than the demand valve's flow.…”

Section: Classification Of Ventilatorsmentioning

confidence: 99%

Controlled mechanical ventilation in equine anaesthesia: Classification of ventilators and practical considerations (Part 2)

Moreno-Martinez

Senior

Mosing

2021

Summary Controlled mechanical ventilation (CMV) is routinely used in equine anaesthesia, with many different options available to facilitate the delivery of mechanical breaths. The complexity of equine respiratory pathophysiology and the wide range of devices available is described in the two parts of this scoping review. The second part of this review provides an overview of commercially available and hand‐made devices that can be used to deliver CMV in large animals. A short overview of basic physics for mechanical ventilation is given. Working principles are discussed and, where relevant, connected to the pathophysiological background of equine ventilation. The objective of this review is to demystify ventilation modes and ventilators used in equine anaesthesia over the last two decades. In addition, this review aims to provide a practical guide to what the anaesthetist needs to consider before using CMV, how CMV can be delivered and monitored, and which principles need to be applied are included. Comparison of the clinical effects between spontaneous breathing and CMV is included.