phenylephrine-hydrochloride and Hyperventilation

We have recently observed obstructive apneas during nasal intermittent positive-pressure ventilation (nIPPV) and suggested that they were due to hypocapnia-induced glottic closure. To confirm this hypothesis, we studied seven healthy subjects and submitted them to nIPPV while their glottis was continuously monitored through a fiber-optic bronchoscope. During wakefulness, we measured breath by breath the widest inspiratory angle formed by the vocal cords at the anterior commissure along with several other indexes. Mechanical ventilation was progressively increased up to 30 l/min. In the absence of diaphragmatic activity, increases in delivered minute ventilation resulted in progressive narrowing of the vocal cords, with an increase in inspiratory resistance and a progressive reduction in the percentage of the delivered tidal volume effectively reaching the lungs. Adding CO2 to the inspired gas led to partial widening of the glottis in two of three subjects. Moreover, activation of the diaphragmatic muscle was always associated with a significant inspiratory abduction of the vocal cords. Sporadically, complete adduction of the vocal cords was directly responsible for obstructive laryngeal apneas and cyclic changes in the glottic aperture resulted in waxing and waning of tidal volume. We conclude that in awake humans passive ventilation with nIPPV results in vocal cord adduction that depends partly on hypocapnia, but our results suggest that other factors may also influence glottic width.

Topics: Adult; Diaphragm; Female; Glottis; Humans; Hypercapnia; Hyperventilation; Male; Nose; Positive-Pressure Respiration; Reference Values

We have previously observed that, in normal awake subjects passively hyperventilated with intermittent positive-pressure ventilation delivered through nasal access (nIPPV), the glottis could interfere with the ventilation. We report on data obtained in the same subjects during stable sleep. In all cases, the glottis was continuously observed through a fiber-optic bronchoscope, and other indexes were also continuously recorded. Mechanical ventilation was progressively increased up to 30 l/min. We have observed during passive nIPPV in stable sleep that increases in delivered minute ventilation (VEd) resulted in progressive narrowing of the glottic aperture, with increases in inspiratory resistance and progressive reductions in the percentage of the delivered tidal volume effectively reaching the lungs. For a given level of VEd, comparisons showed that the glottis was significantly narrower during sleep than during wakefulness and that the glottis was significantly narrower during stage 2 than during stages 3/4 non-rapid-eye-movement sleep. Moreover, when CO2 is added to the inspired air, glottic aperture increased in five of nine trials without changes in sleep stage. We also observed a significant negative correlation between glottic width and the VED, independent of the CO2 level. We conclude that during nIPPV glottis narrowing results in a decrease in the proportion of the delivered tidal volume reaching the lungs.

Topics: Adult; Apnea; Carbon Dioxide; Female; Glottis; Humans; Hypercapnia; Hyperventilation; Male; Nose; Positive-Pressure Respiration; Reference Values; Respiration; Sleep; Sleep Stages; Tidal Volume; Wakefulness

A mathematical model of the airways is developed which focuses on the dynamic exchange characteristics of heat, water and soluble gas. A typical airway segment is divided radially into three regions: the airway lumen, a thin mucous layer of variable thickness coating the airway wall, and an underlying nonperfused tissue layer. A bronchial circulation capillary bed lies beyond the nonperfused tissue layer. The simultaneous exchange of water, heat and soluble gas is dealt with using the model of Tsu et al. (Ann. Biomed. Eng. 16:547-571, 1988). In the case of excretion of ingested ethyl alcohol from the bronchial and pulmonary circulations, the model predicts that during inspiration, because of the alcohol flux from the airway mucosa, a concentration of alcohol in equilibrium with mucus is achieved in the inspired air before the respiratory bronchioles are reached. During exhalation, much of this alcohol redeposits on the airway surface. The net flux of alcohol from the airway surface exceeds the flux of alcohol from the mouth in the exhaled gas indicating that the exhaled alcohol comes from the airways and bronchial circulation rather than from the alveoli and the pulmonary circulation. Alcohol flux moves farther into the airways with oral breathing compared to nasal breathing. Increased ventilation shifts the alcohol flux more alveolarward. Changes in inspired air temperature and humidity have almost no effect on the distribution of alcohol flux in the airways.

Topics: Computer Simulation; Ethanol; Humans; Hyperventilation; Mouth Breathing; Mucous Membrane; Nose; Pulmonary Gas Exchange; Respiration; Solubility; Temperature

We compared the changes in nasal and pharyngeal resistance induced by modifications in the central respiratory drive in 8 patients with sleep apnea syndrome (SAS) with the results of 10 normal men. Upper airway pressures were measured with two low-bias flow catheters; one was placed at the tip of the epiglottis and the other above the uvula. Nasal and pharyngeal resistances were calculated at isoflow. During CO2 rebreathing and during the 2 min after maximal voluntary hyperventilation, we continuously recorded upper airway pressures, airflow, end-tidal CO2, and the mean inspiratory flow (VT/TI); inspiratory pressure generated at 0.1 s after the onset of inspiration (P0.1) was measured every 15-20 s. In both groups upper airway resistance decreased as P0.1 increased during CO2 rebreathing. When P0.1 increased by 500%, pharyngeal resistance decreased to 17.8 +/- 3.1% of base-line values in SAS patients and to 34.9 +/- 3.4% in normal subjects (mean +/- SE). During the posthyperventilation period the VT/TI fell below the base-line level in seven SAS patients and in seven normal subjects. The decrease in VT/TI was accompanied by an increase in upper airway resistance. When the VT/TI decreased by 30% of its base-line level, pharyngeal resistance increased to 319.1 +/- 50.9% in SAS and 138.5 +/- 4.7% in normal subjects (P less than 0.05). We conclude that 1) in SAS patients, as in normal subjects, the activation of upper airway dilators is reflected by indexes that quantify the central inspiratory drive and 2) the pharyngeal patency is more sensitive to the decrease of the central respiratory drive in SAS patients than in normal subjects.

Topics: Adult; Airway Resistance; Carbon Dioxide; Humans; Hyperventilation; Male; Middle Aged; Nose; Pharynx; Respiration; Respiratory Muscles; Sleep Apnea Syndromes

This investigation was undertaken to demonstrate the contributions of dynamic vestibular and mucosal components to nasal air-flow resistance in healthy human adults. The studies were made by video recording of alar movement, electromyography of alar muscle activity, and by computer-assisted plethysmographic measurement of nasal air-flow resistance. Inspiratory approximation of the alae toward the septum from their expiratory position averaged only 0.6 mm at the high nasal ventilation of 35 L/min; it was less at lower ventilation and absent during voluntary mouth breathing. Inspiratory electromyographic activity also was directly related to the extent of nasal ventilation and was absent during voluntary mouth breathing. The activity was consistent with phasic muscular restraint of vestibular compliance with inspiratory transnasal pressures. Physiologic nasal air-flow resistance changes associated with posture, the nasal cycle, exercise, and hyperventilation persisted despite immobilization of the alae by splinting the vestibule widely open. These changes were abolished by topical decongestant, even in the unsplinted nose, and are therefore vascular.

Topics: Adult; Aged; Airway Resistance; Electromyography; Female; Humans; Hyperventilation; Male; Middle Aged; Movement; Nasal Mucosa; Nose; Physical Exertion; Plethysmography; Respiration; Video Recording

In experiments on animals, airflow through the nasal cavity elicits rhythmic synchronized activity that can trigger and/or elicit epileptic electrographic activities in the limbic structures of the brain. This could be demonstrated in studies of lower vertebrates (frogs and turtles). In the turtle the elicited paroxysmal activity often had the shape of regular high-voltage activity in the theta-frequency range (average frequency, 4.1 Hz). It was further proven in clinical experiments that nasal deep breathing with a closed mouth effectively activates epileptic electrographic phenomena of a temporal (limbic) origin. The activating effect was more pronounced on the side ipsilateral to the ventilated nasal meatus. It could also be evoked by air insufflation into the nasal cavity. This effect was suppressed by anesthesia of the mucous membrane in the upper nasal meatus. Possible mechanisms of this, probably reflex, phenomenon are discussed.

Topics: Animals; Electroencephalography; Epilepsy; Humans; Hyperventilation; Mouth Breathing; Nose; Rana temporaria; Reflex; Respiration; Turtles

Topics: Abnormalities, Multiple; Child; Electroencephalography; Female; Humans; Hyperventilation; Intellectual Disability; Macrostomia; Male; Nose; Osteoarthropathy, Secondary Hypertrophic; Syndrome

Blind nasotracheal intubation has been attempted in 72 patients under light general anaesthesia with propanidid in a one-dose or two-dose technique which provides conditions for up to six attempts. Nasotracheal intubation was achieved in 49 patients with a one-dose technique, and in a further 15 patients with the supplementary dose. It is suggested that this technique with propanidid is safer than other techniques using non-anasthetic respiratory stimulants with their attendant dangers, and that the success rate with propanidid is similar to that using these other techniques.

Topics: Adolescent; Adult; Air Movements; Anesthesia, Intravenous; Child; Cocaine; Evaluation Studies as Topic; Female; Humans; Hyperventilation; Injections, Intravenous; Intubation, Intratracheal; Male; Middle Aged; Nose; Posture; Propanidid

Topics: Humans; Hyperventilation; Intubation, Intratracheal; Nose; Propanidid; Succinylcholine

Topics: Adult; Electrocardiography; Female; Heart Rate; Humans; Hyperventilation; Male; Nose; Physical Exertion; Respiratory Physiological Phenomena; Respiratory System

Topics: Cell Respiration; Crying; Humans; Hydrogen-Ion Concentration; Hyperventilation; Infant; Nose; Respiration