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At least 415 records · Page 23Linked to original sources
PubMed1998

Occult nitric oxide inhalation improves oxygenation in mechanically ventilated children.

OBJECTIVES: Auto-inhalation of nitric oxide (NO) produced in the upper airways may have physiologic effects on lung function. For intubated patients, the upper airway source of NO is eliminated, but the hospital compressed air source from the environment is contaminated with varying levels of NO, creating an "occult" form of NO therapy. We examined the physiologic significance of occult inhaled NO in ventilator-dependent pediatric patients. We hypothesized that very low levels of NO contamination in inspired gas improve PaO2 in ventilator-dependent children. STUDY DESIGN: Inspired NO levels at the mouth were measured by chemiluminescence in 4 pediatric subjects with normal lungs and 3 with parenchymal lung disease. Subjects were sequentially ventilated with first standard hospital gas (H1), switched to pure nitrogen-oxygen at a similar FIO2 but with no NO contamination (A2), hospital gas again (H2), the nitrogen-oxygen (A2) to control for time and sequence, and finally the nitrogen-oxygen mixture with supplemental NO in an amount equal to the NO previously measured in hospital gas (A2 + NO). Inhaled NO levels and PaO2 were recorded 15 minutes into each of the 5 steps. Two patients were studied a second time, remote from their first examination. RESULTS: NO levels in inhaled hospital gas mixtures ranged from 13 to 79 ppb (mean H1 = 53.3 +/- 23.7 ppb, mean H2 = 53.2 +/- 20.7 ppb, mean A2 + NO = 45 +/- 15.3 ppb; P < .0001). Removing NO from ventilator gas decreased PaO2 in all subjects, whereas replacing NO in artificial gas restored PaO2 to baseline values (P < .0001). CONCLUSION: Concentrations of NO in hospital compressed air are variable and have physiologic effects. The long-term implications of these findings remain to be defined.

Child↗
PubMed1987

Somatosensory evoked potentials elicited by air-puff stimuli generated by a new high-speed air control system.

Sharp-fronted air-puffs (a rise-time of 1 msec) generated by the new high-speed air control system were used for eliciting SEPs. This system employs a rotating disk driven by a synchronous electric motor for high-speed control of air flow from a compressed air source. The air-puff is reproducible and its pressure wave form can be varied. SEPs to air-puffs or electrical stimulations of the right hand recorded from the contralateral parietal scalp had similar wave forms, but SEPs to air-puffs showed longer latencies (1-4 msec) and smaller amplitudes than those to electrical stimuli. The amplitude of early components in air-puff SEPs was on average 30% of that in electrical SEPs, but later components reached up to about 90%.

Adolescent↗
PubMed1992

Human temperature regulation during narcosis induced by inhalation of 30% nitrous oxide.

The study investigated the effect of inhalation of 30% nitrous oxide (N2O) on temperature regulation in humans. Seven male subjects were immersed to the neck in 28 degrees C water on two separate occasions. They exercised at a rate equivalent to 50% of their maximum work rate on an underwater cycle ergometer for 20 min and remained immersed for an additional 100 min after the exercise. In one trial (AIR) the subjects inspired compressed air, and in the other trial (N2O) they inspired a gas mixture containing N2O (20.93% O2-30% N2O-49.07% N2). Sweating, measured at the forehead, and shivering thermogenesis, as reflected by O2 uptake, were monitored throughout the 100-min recovery period. The threshold core temperatures at which sweating was extinguished and shivering was initiated were established relative to resting preexercise levels. Neither the magnitude of the sweating response nor the core threshold at which it was extinguished was significantly affected by the inhalation of N2O. In contrast, shivering thermogenesis was both significantly reduced during the N2O condition and initiated at significantly lower core temperatures [change in esophageal temperature (delta T(es)) = -0.98 +/- 0.33 degrees C and change in rectal temperature (delta T(re)) = -1.26 degrees C] during the N2O than during the AIR condition (delta T(es) = -0.36 +/- 0.31 degrees C and delta T(re) = -0.44 +/- 0.22 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Effect of alpha-adrenergic blockade on exercise-induced asthma and conditioned cold air.

Cooling and drying of the intrapulmonary airways have been shown to be important stimuli for the development of bronchospasm induced by exercise and isocapnic cold air hyperventilation. It has also been suggested that alpha-adrenergic receptor activity is increased at lower temperatures. To evaluate the role of alpha-adrenergic activity in the development of bronchoconstriction during airway cooling, we examined the effects of alpha-adrenergic blockade with phentolamine on bronchospasm induced by exercise and isocapnic cold air hyperventilation in 8 asthmatics. Exercise consisted of 6 min of steady-state exercise at 90% predicted maximal heart rate breathing compressed air at 0% humidity and 21 +/- 1 degrees C (mean +/- SD). During baseline exercise studies, FEV1 fell 41.6 +/- 15.8%, but only 12.8 +/- 8.5% during alpha-adrenergic blockade (p less than 0.001). Isocapnic cold air challenge consisted of breathing compressed cold air (0% humidity, -17 +/- 4 degrees C) for 3-min periods, with stepwise increases in minute ventilation (Ve) until the FEV1 fell at least 20%. During baseline cold air challenges, FEV1 fell 20% (PD20 FEV1) at a Ve of 48.8 +/- 21 L/min. However, during alpha-adrenergic blockade 6 asthmatics were able to achieve much higher levels of VE (86.6 +/- 22.7 L/min) before FEV1 fell 20% (p less than 0.01), and 2 asthmatics did not decrease their FEV1 by 20%, despite reaching maximal levels of ventilation of 132 and 108 L/min, respectively. Alpha-adrenergic blockade did not affect airways responses to histamine or ragweed antigen (p greater than 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed2004

The effect of dehydration on quantitative light-induced fluorescence analysis of early enamel demineralization.

The purpose of this study was to determine the effect of hydration [distilled water (DH2O) and saliva] on lesions of varying severity and determine an optimal drying method to obtain reliable quantitative light-induced fluorescence (QLF) readings. Ten previously extracted molars were placed into a demineralizing solution for 7, 14 and 21 days. Between each demineralizing cycle the teeth were removed. To test for in vitro reliability the teeth were rinsed in DH2O for 1 min and then QLF images were taken every 10 s (control cycle with no drying employed - bench drying only). This was repeated following (i). compressed air drying for 30 s or 15 s and (ii). 30 s cotton wool roll application (CWR). To test for in vivo reliability the experiment was repeated using whole human saliva in place of DH2O. Control groups demonstrated the effect of hydration on QLF reliability; at 7 days reliable results were obtained after 370.4 s (DH2O) and 432.3 s (saliva). Air drying of both DH2O and saliva-rinsed teeth reduced reliability time to 2.1 (+/-6.0) and 3.2 s (+/-7.6), respectively. Cotton wool roll application produced reliable results in 89 s with DH2O and 110 s with saliva. As lesion severity increased [14 days mean deltaQ 115 (+/-90.2), 21 days mean deltaQ 168.0 (+/-120.7)] time to reach reliability significantly increased under control drying and CWR (P > 0.05). Time taken for compressed air-dried teeth to produce reliable results was not significantly different across the groups. Compressed air-drying for 15 s produces reliable results with both DH2O and saliva-hydrated lesions. Future in vivo experiments will be required to determine if the air-drying can be reduced further in a clinical situation.

Dental Caries↗
PubMed2001

Effectiveness of HVAC duct cleaning procedures in improving indoor air quality.

Indoor air quality has become one of the most serious environmental concerns as an average person spends about 22 hr indoors on a daily basis. The study reported in this article, was conducted to determine the effectiveness of three commercial HVAC (Heating Ventilation Air Conditioning) duct cleaning processes in reducing the level of airborne particulate matter and viable bioaerosols. The three HVAC sanitation processes were: (1) Contact method (use of conventional vacuum cleaning of interior duct surfaces); (2) Air sweep method (use of compressed air to dislodging dirt and debris); (3) Rotary brush method (insertion of a rotary brush into the ductwork to agitate and dislodge the debris). Effectiveness of these sanitation processes was evaluated in terms of airborne particulate and viable bioaerosol concentrations in residential homes. Eight identical homes were selected in the same neighborhood. Two homes were cleaned using each procedure and two were used as controls. It was found that both particle count readings and bioaerosol concentrations were higher when cleaning was being performed than before or after cleaning, which suggests that dirt, debris and other pollutants may become airborne as a result of disturbances caused by the cleaning processes. Particle count readings at 0.3 micron size were found to have increased due to cigarette smoking. Particle counts at 1.0 micron size were reduced due to HVAC duct cleaning. Post-level bioaerosol concentrations, taken two days after cleaning, were found to be lower than the pre-level concentrations suggesting that the cleaning procedures were effective to some extent. Homes cleaned with the Air Sweep procedure showed the highest degree of reduction in bioaerosol concentration among the three procedures investigated.

Aerosols↗
PubMed1976

[A clinical method of testing the humidifying capicity of the human nose (author's transl)].

At the beginning attention is drawn to the fact that there is a lack of suitable clinical tests for the measurement of the humidifying and warming capacity of the nose. The great number of testing methods which have been published so far, have been either too complicated to be applied in routine checks or they were too physically strenous, so that this could not be reasonably demanded of the patients. With the help of the clinical method of testing introduced by us one can find out about norm data for the quantitiy of water needed for humidifying the inspired air in healthy persons, as well as examine the influence of pharmacons on the secretion capacity of the nose. In addition to this, pathological states such as atrophic rhinitis, vasomotoric and allergic rhinitis, patients operated with a partial maxillectomy or with total laryngectomy can also be tested as far as the humidifying and warming capacity of the nose ist concerned. In our testing method extremely dry air streams out of a compressed air cylinder with a flow of 8 1/min through a small silicone catheter at the choanal end of one nasal part and is sucked out of the other nostril with a suction flow of 5 1/min, the air passing through a psychrometer modified by us. The excess flow of 3 1/min streams from the naso- into the oropharynx most effectively preventing the air which is to be measured from mixing with the expiratory air saturated with water-vapor. A gas analyzer sensitive to carbon dioxide measures the error possible in this open system which amounts to only one percent of an average mixture with expiratory air. With the help of a psychrometer-normogramme the absolute humidity is determined from the data of the wet and both the dry thermometers. We were testing 22 healthy persons, average age 34, the norm data were established. The result is that for the hole 10 minute measurement period one nasal part needs 1.58 g water for the humidifying of the inspired air. From this it can be calculated that 456 g of water are necessary for humidifying the inspired air through both nasal parts during 24 hours. Compared with other exact methods, which, however, are not suitable for clinical tests (Ingelstedt et al.) our simple and easily workable method correlate very well.

Adult↗
PubMed1997

Nitric oxide production during exercise in chronic heart failure.

In chronic heart failure (CHF), the ventilatory response is increased compared with normal. This response is, in part, caused by reduced perfusion to ventilated lung. Nitric oxide (NO) is a potent vasodilator and may have an important role in pulmonary vasodilatation during exercise. NO is present in exhaled air. The amount of NO in exhaled air, when breathing NO-free compressed air, is known to increase in normal subjects during exercise. In this study, we quantified NO output in exhaled air in patients with CHF during exercise. Six patients with CHF (New York Heart Association Class II and III; two with dilated cardiomyopathy, three with ischemic heart disease, and one with hypertensive heart disease) and six normal subjects were studied with a symptom-limited incremental exercise test on a cycle ergometer. Oxygen uptake (VO2), carbon dioxide output (VCO2), and minute ventilation (VE) were measured breath by breath with a mass spectrometer, flow meter, and computer. The NO concentration was continuously measured in mixed expired air by chemiluminescence. Peak exercise work rate was lower in patients with CHF than in normal subjects (71.3 +/- 41.6 W vs 257.0 +/- 49.7 W; p < 0.01). Patients with CHF showed a higher VE/VCO2 level at peak exercise than normal subjects (CHF, 47.0 +/- 10.7; normal subjects, 35.6 +/- 5.2; p < 0.01). NO concentration of exhaled air at rest was lower in CHF patients than in normal subjects (4.0 +/- 2.2 ppb vs 10.5 +/- 6.2 ppb, respectively; p < 0.05). NO output from the respiratory tract (VNO) was significantly lower in patients with CHF compared with normal subjects at rest (45.3 +/- 24.3 nl/min, 117.5 +/- 60.1 nl/min, respectively, p < 0.05), and although it increased during exercise, it did not increase in patients with CHF as much as in normal subjects (75.3 +/- 43.4 nl/min vs 512.9 +/- 253.6 nl/min, respectively; p < 0.01). The increase above rest (exercise/rest) was smaller in patients with CHF than in normal subjects (2.10 +/- 1.92 vs 4.81 +/- 2.67, p < 0.05). These data support the concept that the smaller increase in NO production (VNO) during exercise may be responsible for a blunted vasodilation in patients with CHF, resulting in a smaller reduction in dead space/tidal volume and VE/VCO2 at the lactic acidosis threshold than normal. This finding may play a role in the abnormally high ventilatory response to exercise in patients with CHF.

Adult↗
PubMed2003

[Subcutaneous emphysema and pneumomediastinum after dental drilling].

Subcutaneous emphysema and pneumomediastinum is a rare complication of dental treatment. Our case report describes a case secondary to dental drilling with a high-speed air drill, and diffusion of the compressed air. Our case had the classical clinical features of sudden subcutaneous emphysema starting in the face, and subsequently extending into the neck and thorax, accompanied by severe pain and dyspnoea. Rapid medical treatment for this emergency avoided the surgical decompression.

Adult↗
PubMed1984

[A transportation vehicle for laparoscopically obtained follicular specimens].

Structure, function and first results with a vehicle for transportation were described. This apparatus allows to store laparoscopic harvested follicular fluids for a while in constant temperature and in air condition with 5% CO2 in compressed air. Simultaneously the follicular fluids were transported in this vehicle from operating theatre to the laboratory.

Female↗
PubMed1993

Mechanics of the occlusive arm cuff and its application as a volume sensor.

Although a common medical instrument, the mechanical function of an occlusive arm cuff has not been fully described in an engineering sense. The occlusive arm cuff is examined here using a mathematical mechanics model and experimental measurements. Cuff stretch was modeled by a nonlinear pressure-volume function. Air compression was represented by Boyle's law. An apparatus was developed to measure pressure due to the air volume pumped into the cuff for fixed arm volume. Data were obtained for two different cuff designs, and reveal a nonlinear cuff pressure-volume relationship that could be represented accurately by the mathematical model. Calibration constants are provided for the two types of occlusive cuff. Thus, the cuff pressure was found to consist of a balance between that produced by stretch of the elastic cuff bladder and that of the compression of the air contained within the bladder. The use of the gas law alone was found to be inadequate to represent the cuff mechanics. When applying the cuff to measure change in arm volume, such as during plethysmography or oscillometry, it cannot be assumed that the cuff sensitivity is constant. More precisely, it was found that the occlusive cuff is a transducer with a volume sensitivity that increases with cuff pressure and volume until it becomes nearly constant at high levels of cuff pressure (150 mmHg). A hypothetical case of a linear elastic artery with constant pulse pressure was used as input to the cuff model to illustrate the change in cuff pressure oscillations that occurs while cuff pressure is released.(ABSTRACT TRUNCATED AT 250 WORDS)

Arm↗
PubMed1994

Influence of hyperbaric oxygen on left ventricular contractility, total coronary blood flow, and myocardial oxygen consumption in the conscious dog.

It is known that hyperbaric oxygenation (HBO) decreases total coronary blood flow (TCBF) and cardiac output (CO). To determine whether this is related to an alteration in myocardial contractility, 10 chronically instrumented conscious dogs were studied during pharmacologic autonomic blockade. Left ventricular (LV) volume was measured with ultrasonic transducers, LV transmural pressure with micromanometers, TCBF with Doppler-flow probes, and coronary AVO2 difference (A-CSO2) was calculated from direct LV and coronary sinus (CS) sampling. To evaluate the effect of increased oxygenation, data were obtained during resting control conditions and during dynamic vena caval occlusions (VCO), at 1 atmosphere of pressure, while breathing air (1 bar/0.21); at 3 atmospheres, breathing compressed air (3 bar/0.21), and at 3 atmospheres breathing 100% oxygen (3 bar/1.0). Because of autonomic blockade, heart rate (HR) was not statistically different in the three conditions. With increasing oxygenation, arterial oxygen tension (PaO2) increased from 85 +/- 5 mmHg (mean +/- SD) at 1 bar/0.21, to 1374 +/- 201 mmHg at 3 bar/1.0 whereas arterial carbon dioxide tension (PaCO2) and pH values were not statistically different. Arterial oxygen content (AO2 content) and CSO2 content increased significantly (both P < 0.05) with increasing PaO2. LV stroke volume (SV), CO, coronary blood flow, and myocardial oxygen consumption (MVO2) were all significantly reduced (P < 0.05) with increasing levels of oxygenation. Intrinsic myocardial function, as measured by the stroke-work/end-diastolic volume relationship was unchanged from 1 bar/0.21 to 3 bar/0.21, and to 3 bar/1.0 (P < 0.20). Thus, the diminished TCBF, CO, and MVO2 associated with HBO do not seem to be associated with a primary alteration in myocardial contractility, but rather may result from a physiologic autoregulation of the myocardium to increasing levels of PaO2.

Animals↗
PubMed2004

Development of respiratory function in the American locust Schistocerca americana. II. Within-instar effects.

We hypothesized that oxygen delivery becomes more difficult for insects and tracheate arthropods as they progress throughout an intermolt period. During this time, body mass can more than double, yet the major tracheae and spiracles cannot be increased in size until molting. Also, tissue growth could compress air sacs used for convective gas exchange. To test these possibilities, we investigated the effect of within-instar growth on respiratory parameters, including CO(2) emission rate, ventilation frequency, tidal volume and critical oxygen partial pressure (P(O2)) for first-, third- and fifth-instar juveniles and adults of the American locust Schistocerca americana. We found that late-stage grasshoppers tended to have 40% higher total CO(2) emission rates but 15% lower mass-specific CO(2) emission rates and 35% higher ventilation frequencies than early-stage animals. Maximal tracheal system conductance decreased by 20-33% at the end of an instar, possibly due to compression of air sacs. In addition, animals nearing the end of an instar had higher critical P(O2) values for abdominal pumping, and late-stage adults had 50% lower tidal volumes, suggesting that increases in tissue mass throughout an instar may hinder the ability of animals to breathe deeply. Late-stage adults had lower critical P(O2) values for CO(2) emission, although this pattern was not found in any juvenile instars, indicating that late-stage juveniles compensate for decreased conductance by increasing ventilation frequency or the use of diffusive gas exchange. Our data suggest that late-stage arthropods are more vulnerable to hypoxia and may have reduced aerobic capacities and lower tissue P(O2)s than early-stage arthropods.

Animals↗
PubMed1987

Preoperative assessment of tracheoesophageal speech.

Air insufflation testing of tracheoesophageal (TE) puncture candidates as currently practiced lacks objectivity and relies on subjective evaluation of the sound produced. Intraesophageal pressure measurements were obtained from 21 consecutive laryngectomized patients during air insufflation by either experienced examiners or a compressed air source at 1 liter or 3 liters per minute. Postoperatively, three levels of TE speech fluency were identified. Preoperative intraesophageal pressure measurements were associated with a specific post-TE puncture speech fluency result. Intraesophageal pressure measurements may offer a reliable objective preoperative assessment of post-TE puncture speech fluency and identify patients who would benefit from pharyngeal myotomy at the time of TE puncture.

Aged↗