Vincent Jounieaux

Trigeminal nasal receptors related to respiration and to various stimuli in cats

In twenty adult cats of either sex under nembutal anaesthesia, we aimed at delineating the sensitive territory of trigeminal nerves innervating the nasal mucosa. The different trigeminal nerves (anterior ethmoidal, posterior nasal and infraorbital nerves) were dissected in the orbit. Activity of these nerves was recorded during spontaneous nasal and tracheal breathing and in response to various stimuli: mechanical (manual probing and air jets) and irritants (ammonia vapours). Multiple and unitary activity recorded in nerve filaments enabled a classification of the receptors on the basis of their discharge pattern as rapidly-, intermediately- or slowly adapting receptors, and as drive or non-drive nasal receptors depending on whether or not the respiratory modulation was preserved during tracheal breathing.

Utility of blood cultures in community-acquired pneumonia requiring hospitalization: influence of antibiotic treatment before admission

It has been previously shown that antibiotics given before hospitalization significantly reduce the proportion of positive blood cultures in community-acquired pneumonia (CAP). The aim of this prospective study was to compare the utility and cost-benefits of blood cultures in patients, hospitalized for moderate CAP, who had or had not received antibiotic therapy prior to admission. During 1 year, 53 patients were included and separated into two groups: group 1 patients had not received antibiotic treatment prior to admission (n = 30), whereas group 2 patients had been treated with antibiotics (n = 23). Within the first 48 hours, a set of blood cultures was collected if the body temperature was higher than 38.5 degrees C or in the case of shaking chills. A total of 136 blood cultures was collected; 74 in group 1 and 62 in group 2. Bacteraemia was significantly more frequent in group 1 than in group 2, 5/30 patients vs. 0/23, respectively (P < 0.05). The cost of negative blood cultures was valued at 13,939.2 FF in group 1 and 13,164.8 FF in group 2, respectively 464.6 +/- 244.3 FF and 569.3 +/- 233.4 FF per patient (n.s.). Moreover, blood cultures were the method of diagnosis in only one of the five patients with bacteraemia and in no case did a positive blood-culture result influence the initial therapeutic regime. Thus, our results suggest a reduced clinical utility and cost-benefit of blood cultures in patients hospitalized for moderate CAP who have received an antibiotic treatment prior to admission.

Influence of trigeminal nasal afferents on bulbar respiratory neuronal activity.

This study examined the influence of nasal trigeminal afferents, the anterior ethmoidal nerve (AEN) and posterior nasal nerves (PNN) on the spike discharges of respiratory-related neurons recorded in the ventral respiratory group (VRG) (2.6-3.5 mm lateral to the midline, from 1 mm rostral to 3 mm caudal to the obex and at depth of 2-4 mm below the dorsal surface). Electrical stimulations to the AEN and PNN were administered to 10 pentobarbital anaesthetized cats and to 8 ketamine anaesthetized, vagotomized, curarized and ventilated cats. Single shock stimulations of either nerve evoked transient and total inhibition of inspiratory activities. Expiratory-related neurons of the VRG presented three patterns of activity in response to stimulation:excitation, inhibition or inhibition followed by excitation. More generally, expiratory units are activated with a short latency. In the course of repetitive stimulation of the AEN and PNN we observed a prolongation of the spontaneous inspiratory discharge which presented transient, short inhibition in response to each shock. Most expiratory units presented a short activation which was synchronous with the transient inhibition of inspiratory activities. When repetitive stimulation provoked a sneeze-like response, we observed a progressive increase in the duration of transient inspiratory inhibition first, associated with a progressive reinforcement of transient expiratory activation. Secondarily, just before the expiratory thrust, we noted a stronger inhibition of the inspiratory activity which preceded a high-frequency (400 Hz) expiratory discharge. Nasal afferents exert a forceful excitatory effect on bulbospinal (BS) and non-bulbospinal-non-vagal (NBS-NV) expiratory cells of the VRG. The effects due to vagotomy and curarization are discussed.

Trigeminal afferences implied in the triggering or inhibition of sneezing in cats

The aim of this study was to precise the role of the different trigeminal nerve branches involved in innervation of the nostril in triggering the sneeze reflex. Electrical stimulation of the anterior ethmoidal, posterior nasal and infraorbital nerves was performed in anaesthetized cats. Stimulation of these 3 nerves produced sneezing identical to that induced by mechanical stimulation. Our results emphasize inhibition of the sneeze reflex related to stimulation of the anterior ethmoidal or the posterior nasal nerves by stimulation of the infraorbital nerve.

Oxygen consumption and PEEPe in ventilated COPD patients.

The intrinsic positive-end-expiratory pressure (PEEPi) increases the inspiratory load, the cost of breathing and thus oxygen consumption (V(O2)). It has been shown that applying an extrinsic positive-end-expiratory pressure (PEEPe) reduces the inspiratory threshold load but the optimal PEEPe level is still in debate. We hypothesize that the best level of PEEPe could induce a decrease in V(O2) by reducing the V(O2) demands from PEEPi. Nine mechanically ventilated COPD patients were included. The level of PEEPe was determined in accordance with the static PEEPi. V(O2) was measured using an automatic gas analyser during synchronized intermittent mandatory ventilation (SIMV): without PEEPe, with a PEEPe equal to 50% of static PEEPi and with a PEEPe equal to 100% of static PEEPi. Static PEEPi appeared to be significantly correlated with the degree of airflow obstruction (FEV1) (P<0.05). Applying a PEEPe equal to static PEEPi resulted in a significant decrease in V(O2) (P<0.05) whereas the change in V(O2) proved to be unpredictable for a PEEPe level of 50% of static PEEPi. In conclusion, V(O2) decreases progressively when increasing PEEPe up to a level equal to 100% of static PEEPi. Thus, in mechanically ventilated COPD patients with a FEV1 < or = 1000 ml, applying a PEEPe of 5 cmH2O should be recommended.