The use of labeled microspheres to determine blood flow in the dog's nasal mucosa

Assessment of Upper Respiratory Tract and Ocular Irritative Effects of Volatile Chemicals in Humans

Accurate assessment of upper respiratory tract and ocular irritation is critical for identifying and remedying problems related to overexposure to volatile chemicals, as well as for establishing parameters of irritation useful for regulatory purposes. This article (a) describes the basic anatomy and physiology of the human upper respiratory tract and ocular mucosae, (b) discusses how airborne chemicals induce irritative sensations, and (c) reviews practical means employed for assessing such phenomena, including psychophysical (e.g., threshold and suprathreshold perceptual measures), physiological (e.g., cardiovascular responses), electrophysiological (e.g., event-related potentials), and imaging (e.g., magnetic resonance imaging) techniques. Although traditionally animal models have been used as the first step in assessing such irritation, they are not addressed here since (a) there are numerous reviews available on this topic and (b) many rodents and rabbits are obligate nose breathers whose nasal passages differ considerably from those of humans, potentially limiting generalization of animal-based data to humans. A major goal of this compendium is to inform the reader of procedures for assessing irritation in humans and to provide information of value in the continued interpretation and development of empirical databases upon which future reasoned regulatory health decisions can be made.

Sympathetic control of blood flow to AVAs and capillaries in nasal and facial tissues supplied by the internal maxillary artery in dogs

Total blood flow and perfusion pressure (PP) of the internal maxillary artery (IMA) were recorded bilaterally during electrical stimulation (8 V, 2ms) of the right cervical sympathetic nerve at frequencies (f) of 0.3, 0.5, 1.0 and 3.0 Hz in anesthetized, paralyzed and artificially ventilated dogs. Distribution of IMA-FLOW to precapillaries (CAP-FLOW) and arteriovenous anastomoses (AVA-FLOW) was determined by the tracer microspheres technique. During electrical stimulation (ES) IMA-FLOW was affected only unilaterally and decreased in a hyperbola-like fashion with the increase of f, while contralateral IMA-FLOW remained unchanged. Systemic blood pressure as well as PP of both IMA remained unchanged while heart rate was only increased during ES at maximal f. The reduction of IMA-FLOW was mainly due to marked vasoconstrictor responses of the AVAs, which were already attained at low f while significant vasoconstrictor responses of precapillaries occurred at higher f and were less pronounced. The early response of AVAs to increasing sympathetic activation enables IMA-FLOW to be adjusted in a physiological range of sympathetic activities, before CAP-FLOW is substantially reduced. The predominance of AVA-FLOW in blood flow control of the IMA was also supported by the conformity in their hyperbolic relationship with maxillary resistance at rest and during enhanced levels of sympathetic vasoconstrictor activity.

Arterial supply, venous drainage and collateral circulation in the nose of the anaesthetized dog

1. In pentobarbitone-anaesthetized dogs, nasal blood flows were measured with electromagnetic flow sensors. 2. The terminal internal maxillary artery was found to supply 22 +/- 2.2 ml min-1 (one side) to the nasal mucosa via the sphenopalatine and major palatine branches; the artery was found to receive multiple supply routes from common carotid, vertebral and subclavian arteries. 3. Nasal mucosa was found to receive collateral flow from contralateral terminal internal maxillary artery (about 5 to 10% of normal flow) and branches of subclavian arteries (about 36% of normal flow). 4. Nasal mucosa was found to have two venous systems: the low-flow (12 +/- 1.0 ml min-1; both sides) and low-pressure (7 +/- 0.6 mmHg) sphenopalatine veins draining the posterior nasal cavity and the high-flow (30 +/- 1.4 ml min-1; both sides) and high-pressure (17 +/- 1.0 mmHg) dorsal nasal veins draining the anterior nasal cavity. 5. PO2 of nasal venous blood was found to range from 62 +/- 2.9 mmHg to 65 +/- 3.4 mmHg. During nitrogen challenge to the nose, the sphenopalatine venous PO2 dropped to 35 +/- 3.0 mmHg while the dorsal nasal venous PO2 remained unchanged, suggesting that the sphenopalatine veins were responsible for draining capillary flow and dorsal nasal veins arteriovenous anastomotic flow as well. 6. Microscopic examination of the vascular casts confirmed that arteriovenous anastomoses were located only in the anterior nasal cavity.

Effects of exercise on nasal resistance and nasal blood flow

Nasal resistance and nasal blood flow were measured consecutively before exercise, immediately after exercise, 5, 10, 15, 20, 25, and 30 minutes after exercise in 11 normal subjects and 18 patients with perennial allergic rhinitis. Nasal resistance was measured by Nihon-Koden Rhinorheograph MRP 2100, and nasal blood flow was measured by Periflux PF2, a laser doppler flowmeter. 77% of unilateral nasal cavities in normal subjects and 75% of unilateral cavities in patients with allergic rhinitis showed a decrease of both nasal resistance and nasal blood flow immediately after exercise. However, rates of changes in nasal resistance and in nasal blood flow were not correlated with each other. In the latter period after exercise, there was a discrepancy between nasal resistance and nasal blood flow. A laser doppler flowmeter is considered to measure blood flow in the superficial part of the nasal mucosa. Based upon our results, an intensive stimulus such as exercise seems to induce vasoconstriction in the superficial part as well as in the deeper part of the nasal mucosa. However, it is also suggested that the vessels in the various parts of the nasal mucosa don't always respond in the same way.

Nasal blood flow and airway resistance. Canine study

Nasal blood flow was measured in anesthetized dogs by an electromagnetic flow sensor placed around the terminal branch of the internal maxillary artery, the major arterial supply to the nasal mucosa. Nasal airway resistance was monitored simultaneously by recording the transnasal pressure when airflow through the nasal cavity was maintained constant. Phenylephrine decreased nasal blood flow and airway resistance while albuterol (salbutamol) did the opposite. Prostaglandin E1 increased nasal blood flow but decreased airway resistance. The present study demonstrates that nasal vascular and airway resistance may change in parallel or opposite directions, implying that nasal airway resistance cannot be used to assess the vascular situation in the nose.

Control of nasal vasculature and airflow resistance in the dog

Nasal vascular and airflow resistances have been measured in dogs, simultaneously on both sides separately. Vascular resistance was measured either by constant flow perfusion of the terminal branch of the maxillary artery (which supplies, via the sphenopalatine artery, the nasal septum, most of the turbinates and the nasal sinuses) or by measuring blood flow through this artery, maintained by the dog's own blood pressure. Airflow resistance was assessed by inserting balloon-tipped endotracheal catheters into the back of each nasal cavity via the nasopharynx, and measuring transnasal pressure at constant airflow through each side of the nose simultaneously. Preliminary experiments indicated that there was 5-10% collateral anastomosis between the two sides. Close-arterial injection of drugs showed different patterns of response. Adrenaline, phenylephrine, chlorpheniramine and low doses of prostaglandin F2 alpha increased vascular resistance and lowered airway resistance. Salbutamol, methacholine and histamine lowered vascular resistance and increased airway resistance. Dobutamine decreased airway resistance with a small increase in vascular resistance. Prostaglandins E1, E2 and F2 alpha (high dose) decreased both vascular and airway resistances. Substance P, eledoisin-related peptide and vasoactive intestinal polypeptide lowered vascular resistance with little change in airway resistance. The results are interpreted in terms of possible drug actions on precapillary resistance vessels, sinusoids and venules, and arteriovenous anastomoses. It is concluded that nasal airway resistance cannot be correlated with vascular resistance or blood flow, since the latter has a complex and ill-defined relationship with nasal vascular blood volume.

Measurement of blood flow to human nasal mucosa in normal and pathological conditions by the use of the 133Xe clearance technique

The blood flow to nasal mucosa in normal subjects and in allergic rhinitis, vasomotor rhinitis and laryngectomized patients was measured using the 133Xe clearance technique. The results were statistically compared and correlated with capillary diameter. Compared to the normal group, the blood flow to nasal mucosa increased in allergic and vasomotor rhinitis patients and decreased in laryngectomized patients. There was a statistically significant difference between allergic and vasomotor groups (p less than 0.01), so the present method could be used in the differential diagnosis of rhinitis.

The effect of blood pressure on inner ear blood flow

We investigated the effects of blood pressure on the blood flow in the inner ear as compared with other organs in normotensive rats (NR), spontaneously hypertensive rats (SHR) and renal hypertensive rats (RHR). The cardiac output and the regional blood flow were measured by a radioactive microsphere technique in conscious rats. The haemodynamics of the inner ear and other organs and the effects of a converting-enzyme inhibitor (SA-446) on the regional blood flow were compared among NR, SHR, and RHR, the blood pressure being 107, 152, and 185 mm Hg, respectively. With the exception of the heart, the organ blood flow was lower in SHR than in NR in all organs, including the inner ear. It was also lower in RHR than in SHR. The blood pressure dropped after i.v. injection of SA-446, while the regional blood flow increased. The effect was strongest in RHR, followed by SHR and finally NR.

A method for determination of blood flow with 133Xe in human nasal mucosa

The 133Xe wash-out technique was used as a method for calculation of the blood flow in human nasal mucosa. The disappearance of 133Xe from the nasal mucosa was followed using scintillation detectors. In laryngectomies it was shown that the disappearance of 133Xe from the mucosa depended mainly on the blood flow. Leakage of 133Xe from the mucosa to the nasal air was unimportant. The disappearance rate of 133Xe was decreased by oxymetazoline and increased by histamine, mostly likely due to the effects of these vasoactive drugs on the mucosa blood flow. The 133Xe wash-out technique would seem to be a simple method to study nasal mucosal blood-flow changes in humans.

Bilateral nasal vascular responses to unilateral sympathetic stimulation

Unilateral preganglionic cervical sympathetic stimulation in the anaesthetized cat evoked vasoconstriction in both nasal cavities, dependent on stimulation frequency. Vasoconstriction in the contralateral cavity was 15--20% of that of the stimulated side. Similar findings were obtained on unilateral Vidian nerve stimulation. Vasoconstriction evoked in the sympathectomized nasal cavity by stimulating the opposite cervical chain was reduced but not abolished by sectioning the posterior nasal and ethmoidal nerves of the stimulated side. It is suggested that vasoconstrictor fibres reach the opposite cavity either in these nerves or by way of blood vessels, but more likely that sympathetic fibres from these pathways innervate blood vessels which supply both nasal cavities.