At present there is no alternative to the use of a demand valve and pressurised oxygen for emergency ventilation in large animal field anaesthesia, therefore we aimed at providing a proof-of-principle of a small (2.5l) commercial foot pump to provide emergency intermittent positive pressure ventilation (IPPV) in large animals. The study was performed during elective field anaesthesia for castration of 5 Haflinger stallions. Horses were premedicated with acepromazine i.m. after catheterisation of the jugular vein, further sedation was obtained with detomidine and butorphanol i.v. Anaesthesia was induced with ketamine and midazolam i.v. and maintained with a constant rate infusion of midazolam, ketamine and xylazine. After endotracheal intubation the foot pump, modified with a manually operated expiratory valve, was connected to the endotracheal tube and oxygen (6l/min) was supplied. Anaesthesia was monitored using spirometry, respiratory gas analysis, pulse oximetry and arterial blood gas analysis. When arterial partial pressure of carbon dioxide (PaCO2) exceeded 6.65kPa, IPPV was provided by 2-4 consecutive compressions of the pump aiming at a tidal volume of 10ml/kg bwt. The PaCO2 was maintained at 6.18 +/- 3.06kPa (mean +/- s.d.) with a respiratory rate of 4-10 breaths/min. The tidal volume was 2678-8300ml with a peak inspiratory pressure of 24 +/- 6.6cmH(2)O and a mean minute volume of 68.5 +/- 13l/min. Inspired oxygen concentration ranged from 26-46% (36 +/- 7%) and arterial partial pressure of oxygen from 8.38-11.03kPa (10.1 +/- 0.93kPa). The modified foot pump enables the practitioner to provide IPPV to large animals in emergency situations.