Nitric oxide from the human respiratory tract efficiently quantified by standardized single breath measurements

Högman, Marieann; Stromberg, Sarah E.; Schedin, Ulla; Frostell, Claes; Hedenstierna, Göran; Gustafsson, Lars E.

doi:10.1046/j.1365-201x.1997.00101.x

Cited by 83 publications

(88 citation statements)

References 5 publications

(6 reference statements)

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“…This observation is in good agreement with both Högman et al (11) and Kroesbergen et al (10) who used similar target flow rates as we did. Silkoff et al suggested that the transfer rate of NO from the bronchial wall to the lumen is dependent on the concentration gradient between these two compartments and the diffusion capacity of NO (15).…”

Section: Discussionsupporting

confidence: 82%

Evaluation of Exhaled Nitric Oxide in Schoolchildren at Different Exhalation Flow Rates

Pedroletti

2002

Pediatric Research

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Nitric oxide (NO) in exhaled air is believed to reflect allergic inflammation in the airways. Measured levels of exhaled NO vary with the exhaled flow rate, which therefore must be standardized. The aim of this study was to estimate the optimal exhalation flow rate when measuring NO in exhaled air. We studied 15 asthmatic children (8-18 y) with elevated NO levels and 15 age-matched controls and focused on how the quality of the NO curve profile, the discriminatory power, and the reproducibility were influenced by the exhalation flow rate. We used an on-line system for NO measurements at six different exhalation flow rates in the interval of 11-382 mL/s. The fraction of exhaled nitric oxide (FENO) was highly flow-dependent as was expected. Intermediate flow rates yielded a flat and stable NO plateau and were considerably easier to interpret than those obtained at the highest and lowest flow rates. The ratio of FENO between asthmatics and controls was lower at higher flow rates and a considerable overlap in NO values was demonstrated at all flow rates except 50 mL/s. The reproducibility was much lower at more extreme flow rates and was best at 50 mL/s. We conclude that a target exhalation flow rate of approximately 50 mL/s is to be preferred using the single-breath method for on-line NO measurements in schoolchildren. The presence of nitric oxide (NO) in exhaled air was first reported in 1991 (1) and soon after, it was discovered that asthmatics have higher levels of exhaled NO compared with controls (2, 3). These findings have evoked great interest because monitoring the fraction of expired NO (FENO) may be useful in the management of asthma (4), especially in children, for whom noninvasive methods are preferable (5).It has been shown that NO is mainly synthesized in the epithelial layer in the conducting airways (6 -8). This being the case, the concentration of NO in exhaled air will be highly dependent on exhalation flow rate (9 -11). Thus, there is a need to standardize the NO measurements, particular with respect to flow rate. However, previous (4) and current (12) recommendations on exhalation flow rate have not been based on experimental data, but are compromises based on practical/technical issues.We therefore investigated the quality of the exhaled NO curve profile, the reproducibility, and the discriminatory power of the NO values at six different exhalation flow rates in a sample of asthmatic schoolchildren with elevated levels of NO and age-matched controls. MATERIALS AND METHODS Subjects.Fifteen children (aged 8 -18, mean 14 y), three girls and twelve boys, with asthma and elevated NO levels (Ͼ10 ppb at exhalation flow rate 150 mL/s) were recruited from the Allergy clinic at Astrid Lindgren Children's Hospital, Karolinska Hospital.Thirteen of these children had atopic asthma and were sensitized to furred pets, pollen, or house dust mite. Atopy was evaluated by skin prick testing. Five subjects were steroidnaive. Mean dose of inhaled steroids was 305 g/d in steroidtreated patients. A brief structured i...

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Section: Discussionsupporting

confidence: 82%

Evaluation of Exhaled Nitric Oxide in Schoolchildren at Different Exhalation Flow Rates

Pedroletti

2002

Pediatric Research

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“…NO concentration in exhaled breath is dependent on exhalation flow rate (19,25). A two-compartment model explains the exhalation flow rate dependence of NO concentration.…”

Section: Discussionmentioning

confidence: 99%

Nitric oxide and cardiopulmonary hemodynamics in Tibetan highlanders

Hoit

Dalton

Erzurum³

et al. 2005

Journal of Applied Physiology

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When O 2 availability is reduced unavoidably, as it is at high altitude, a potential mechanism to improve O 2 delivery to tissues is an increase in blood flow. Nitric oxide (NO) regulates blood vessel diameter and can influence blood flow. This field study of intrapopulation variation at high altitude tested the hypothesis that the level of exhaled NO (a summary measure of pulmonary synthesis, consumption, and transfer from cells in the airway) is directly proportional to pulmonary, and thus systemic, blood flow. Twenty Tibetan male and 37 female healthy, nonsmoking, native residents at 4,200 m (13,900 ft), with an average O 2 saturation of hemoglobin of 85%, participated in the study. The geometric mean partial pressure of NO exhaled at a flow of 17 ml/s was 23.4 nmHg, significantly lower than that of a sea-level reference group. However, the rate of NO transfer out of the airway wall was seven times higher than at sea level, which implied the potential for vasodilation of the pulmonary blood vessels. Mean pulmonary blood flow (measured by cardiac index) was 2.7 Ϯ 0.1 (SE) l/min, and mean pulmonary artery systolic pressure was 31.4 Ϯ 0.9 (SE) mmHg. Higher exhaled NO was associated with higher pulmonary blood flow; yet there was no associated increase in pulmonary artery systolic pressure. The results suggest that NO in the lung may play a key beneficial role in allowing Tibetans at 4,200 m to compensate for ambient hypoxia with higher pulmonary blood flow and O 2 delivery without the consequences of higher pulmonary arterial pressure. high altitude; oxygen delivery; oxygen availability; hypoxia WHEN OXYGEN AVAILABILITY is reduced, as it is at high altitude, an increased blood flow could potentially improve O 2 delivery to tissues. However, the pulmonary vasoconstriction response to hypoxia decreases blood flow in the lung, the first point of contact with the circulation. This response probably evolved at sea level to maintain gas exchange by redistribution of blood flow from temporarily small, poorly oxygenated to betteroxygenated areas of the lung (17, 32). At high altitude, the entire lung is always hypoxic, and the resulting general vasoconstriction does not redistribute blood flow; instead, it increases pulmonary arterial pressure, sometimes causing pathological remodeling of the heart and lungs (30). However, many people live at high altitude without pulmonary hypertension or cardiac hypertrophy, which suggests that another factor may intervene to maintain blood flow when the blood carries less O 2 and the usual vasoconstriction response increases pulmonary resistance. That factor may be nitric oxide (NO), a vasodilator found in high concentrations in the lungs of high-altitude natives, particularly among Tibetans (5).A wealth of studies support a key role for NO in determining basal pulmonary vascular tone at sea level and in effecting the hypoxic vasoconstriction response. An animal study using NO synthase gene transfer to the airway demonstrates elegantly that increasing NO decreases hypoxic pulmonary v...

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“…Exhaled and nasal NO are markedly flow-dependent, and a significant reduction in NO concentrations has been reported when sampling or exhalation flow rates increase [5,10,13,31,39,40]. The probable reason for the reduction in NO concentration with increased expiratory or sampling flow is that the same amount of NO will be dispersed in a different exhaled or sample volume.…”

Section: Exhalation Parametersmentioning

confidence: 99%

“…The mouthpiece should have an internal restrictor (D) in the breathing circuit to allow exhalation with a low positive pressure 5-20 cmH 2 O. The back-pressure created by expiration against this resistance (as low as 5 cmH 2 O) is already sufficient to keep the soft palate closed [31], so that the nasal cavities are partitioned from the remainder of the respiratory tract, preventing the contamination of exhaled air with nasal NO. As it is difficult for some subjects to maintain Time s 0 ciated instrumentation and computing within a single system.…”

Section: Equipment Requirementsmentioning

confidence: 99%

Exhaled and nasal nitric oxide measurements: recommendations. The European Respiratory Society Task Force

Kharitonov¹,

Alving²,

Barnes³

1997

Eur Respir J

633

528

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Nitric oxide from the human respiratory tract efficiently quantified by standardized single breath measurements

Cited by 83 publications

References 5 publications

Evaluation of Exhaled Nitric Oxide in Schoolchildren at Different Exhalation Flow Rates

Evaluation of Exhaled Nitric Oxide in Schoolchildren at Different Exhalation Flow Rates

Nitric oxide and cardiopulmonary hemodynamics in Tibetan highlanders

Exhaled and nasal nitric oxide measurements: recommendations. The European Respiratory Society Task Force

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