Phrenic nerve stimulated respiration in the anesthetized horse: A comparison with intermittent positive pressure ventilation

Bilateral percutaneous cervical phrenic nerve stimulation (PNS) was used as a method of ventilation in twenty horses under general anesthesia. PONS wa s maintained for 30 minutes at a rate of 10 breaths per minute. Ten horses were allowed to recover from general anesthesia immediately after the cessa tion of PNS and the return to spontaneous respiration. In the remaining ten horses cardiovascular and respiratory parameters were compared with thirty minutes of intermittent positive pressure ventilation (IPPV). PNS effectiv ely enabled controlled ventilation, allowing adjustment of rate and tidal v oulme. Heart rate, mean arterial pressure, systolic and diastolic pressure did not change significantly during PNS. In all horses, end tidal and arter ial carbon dioxide diminished significantly (p<0.0001) within 15 minutes fr om the initiation of PNS and remained low throughout the period of PNS. Car diac output decreased significantly during PNS. There was no significantly during PNS. There was no significant difference in the decrease in cardiac output during PNS versus the decrease during the IPPV. In conclusion, the t echnique of PNS as a method of ventilation was not inferior to IPPV as far as cardiovascular parameters were concerned.