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Biomedical subjects

O Polo

Publications and source records attributed to O Polo.

At least 55 records · Page 3Linked to original sources
PubMed1996

Effect of different levels of hyperoxia on breathing in healthy subjects.

We have recently shown that breathing 50% O2 markedly stimulates ventilation in healthy subjects if end-tidal PCO2 (PETCO2) is maintained. The aim of this study was to investigate a possible dose-dependent stimulation of ventilation by O2 and to examine possible mechanisms of hyperoxic hyperventilation. In eight normal subjects ventilation was measured while they were breathing 30 and 75% O2 for 30 min, with PETCO2 being held constant. Acute hypercapnic ventilatory responses were also tested in these subjects. The 75% O2 experiment was repeated without controlling PETCO2 in 14 subjects, and in 6 subjects arterial blood gases were taken at baseline and at the end of the hyperoxia period. Minute ventilation (VI) increased by 21 and 115% with 30 and 75% isocapnic hyperoxia, respectively. The 75% O2 without any control on PETCO2 led to 16% increase in VI, but PETCO2 decreased by 3.6 Torr (9%). There was a linear correlation (r = 0.83) between the hypercapnic and the hyperoxic ventilatory response. In conclusion, isocapnic hyperoxia stimulates ventilation in a dose-dependent way, with VI more than doubling after 30 min of 75% O2. If isocapnia is not maintained, hyperventilation is attenuated by a decrease in arterial PCO2. There is a correlation between hyperoxic and hypercapnic ventilatory responses. On the basis of data from the literature, we concluded that the Haldane effect seems to be the major cause of hyperventilation during both isocapnic and poikilocapnic hyperoxia.

Adult↗
PubMed1996

Upper airway size and collapsibility in snorers: evaluation with digital fluoroscopy.

This study addressed the question of whether there are any differences in the size and collapsibility of the upper airway measured by digital fluoroscopy, between snorers and controls whilst they were awake and breathing normally; and whether there are any correlations between these measurements and other clinical data. The dynamic changes of the upper airway size were evaluated using digital fluoroscopy in 33 patients and 16 normal controls. The measurements were compared with findings in an overnight sleep study, including a static-charge-sensitive bed (SCSB) and oximeter recordings. The minimum anteroposterior dimension at the velopharyngeal level was smaller in patients with partial upper airway obstruction than in controls (p<0.005); patients with complete obstruction did not differ from the controls. The velopharyngeal airways were also more collapsible in patients with severe partial obstruction (p<0.01) than in controls. At the oropharyngeal and hypopharyngeal levels, the dimensions and the collapsibilities were similar in patients and controls. The velopharyngeal collapsibility correlated with body mass index (p<O.001), whereas the airway size did not. The velopharyngeal collapsibility was more pronounced in patients with frequent episodes of arterial oxyhaemoglobin desaturation during sleep. Velopharyngeal collapsibility associated with high body mass index was the important determinant of nocturnal breathing disturbances. Digital fluoroscopy displays the dynamic changes of the upper airways throughout the respiratory cycle.

Adult↗
PubMed1996

Respiratory challenge induces high frequency spiking on the static charge sensitive bed (SCSB).

The static charge sensitive bed (SCSB) is a simple and noninvasive device used for the detection of sleep apnoea. In addition to episodes of apnoea or hypopnoea, heavy snorers commonly present with episodes of high frequency spiking on the SCSB. These spiking episodes have been claimed to represent partial upper airway obstruction during sleep, but the mechanism of their appearance is not known. We studied the SCSB spiking phenomenon in awake subjects during experimental respiratory challenge. One female and five male volunteers were studied whilst breathing freely, during hypoxia, hypercapnia and inspiratory and expiratory loading. Oxygen saturation, end-tidal carbon dioxide tension, minute ventilation, oesophageal pressure, electrocardiographic activity (ECG), blood pressure and the SCSB signals were monitored. During free breathing, the SCSB high frequency signal consisted of low amplitude complexes with close time relationship to the cardiac cycle. During respiratory challenge, spiking occurred. These spikes showed no time relationship to the cardiac cycle, but were time-linked to the onset of inspiration or expiration. Spike amplitude correlated with breathing frequency (r2 = 0.59; p < 0.005) and variation in oesophageal pressure (r2 = 0.57; p < 0.005). We conclude that during quiet, unobstructed breathing the static charge sensitive bed high frequency signal represents cardiac activity (ballistocardiogram), whereas during high-drive breathing high frequency spikes are produced. These spikes are respiratory in origin and are likely to represent fast components of respiratory movements. Our results support the use of static charge sensitive bed spiking as a noninvasive measure of breathing stimulation.

Adult↗
PubMed1996

The static-charge-sensitive bed in the monitoring of respiration during sleep in infants and young children.

The performance of the static-charge-sensitive bed (SCSB) in the monitoring of nocturnal breathing was studied in 22 infants and young children at the mean age of 24 weeks (SD 24, range 1-79 weeks). The conventional polysomnogram (PSG) was used as a reference method. Episodes of central apnoea were detected with high sensitivity by the SCSB. Episodes of obstructive apnoea and obstructive parts of mixed apnoea were not identified. When the SCSB recordings were scored with the airflow signal some mixed events were identified, but the detection of obstructive apnoea episodes remained poor. Partial upper airway obstruction increased the amount of SCSB spiking (high-frequency components of breathing), which may have diagnostic value. In conclusion, the SCSB enables simple, non-invasive detection of central apnoea episodes, periodic breathing and the behavioural state of the child.

Analysis of Variance↗
PubMed1995

Nocturnal hyperventilation in pregnancy--reversal with nasal continuous positive airway pressure.

A 41-year-old mother with a twin pregnancy had disabling hyperventilation with severe nocturnal symptoms at 25 weeks' gestation. The nocturnal attacks were relieved with nasal continuous positive airway pressure, which she successfully used throughout the rest of the pregnancy. Nasal continuous positive airway pressure could be an option to control severe pregnancy-induced hyperventilation.

Adult↗
PubMed1995

Nocturnal breathing abnormalities in acromegaly after adenomectomy.

OBJECTIVE: The incidence of sleep apnoea is increased in acromegaly. The aim of the study was to determine the occurrence of nocturnal breathing abnormalities and upper airway morphology in acromegalic patients some years after adenomectomy. DESIGN: A case-control study. PATIENTS: Eleven patients with treated acromegaly and two control groups: (1) sleep studies: 197 subjects randomly selected from the population, (2) cephalometry: 27 healthy subjects and 17 patients with obstructive sleep apnoea. MEASUREMENTS: Nocturnal breathing was monitored with a static charge-sensitive bed. The upper airway soft tissues and bone morphology were assessed by cephalometric X-ray photography. The upper airway collapsibility was investigated with dynamic nasopharyngoscopy. Endocrinological investigations were also performed. RESULTS: Nocturnal breathing abnormalities were present in all but one acromegalic patient (91%), which was far more frequent than in the general population (29.4%, P < 0.0001). Treated acromegaly was the most powerful predictor of breathing abnormalities, independent of the other significant predictors, age and body mass index. The predominant breathing abnormality was periodic breathing with symmetrically waxing and waning respiratory effort without a major body movement component. Episodes of complete obstruction with repetitive arousals were rare. Except for the longer soft palate, the cephalometric findings were similar to normal. In comparison to obstructive sleep apnoea, the treated acromegalic patients had rather prognathic than retrognathic mandibles. Fibreoptic endoscopy in the acromegalic patients revealed collapsible upper airways at the level of the soft palate, whereas at the base of the tongue little, if any, dynamic narrowing was observed. CONCLUSION: Our study confirms that nocturnal breathing abnormalities are common in treated acromegaly, and may persist years after the removal of the GH secreting tumour. The breathing abnormalities and the upper airway morphology in acromegalic patients after adenomectomy are different from those observed in primary obstructive sleep apnoea, suggesting a different pathophysiology of the airway obstruction.

Acromegaly↗
PubMed1995

Ventilatory response to isocapnic hyperoxia.

Breathing O2 for up to 1 h has been shown to either not influence or slightly increase (6-13%) minute ventilation. However, end-tidal PCO2 was not kept constant in these experiments. In nine healthy men, we studied the ventilatory, blood pressure, and heart rate responses to 30 min of normobaric hyperoxia (50% O2) at isocapnic conditions. Hyperoxia led to a 60% increase in mean minute ventilation (P = 0.002), largely due to an increase in mean tidal volume from 0.66 +/- 0.04 (SE) to 0.88 +/- 0.05 liter (P = 0.007). Fifteen minutes after the termination of hyperoxia, minute ventilation was still increased (P = 0.02) compared with baseline, although it was reduced compared with hyperoxia (P = 0.02). Arterial blood gas analyses in six subjects before and during hyperoxia showed an increase in arterial PO2 and O2 saturation but no change in arterial PCO2 or pH. Hyperoxia induced no changes in arterial blood pressure or heart rate. We conclude that 1) isocapnic hyperoxia stimulates respiration markedly, an effect that is approximately five times higher than previously measured; 2) the increase in ventilation induced by hyperoxia does not affect arterial blood pressure and heart rate; and 3) in experiments using hyperoxia, its effect on breathing and subsequently on PCO2 has to be taken into account.

Adult↗
PubMed1994

Asymmetry of instructed motor response to auditory stimuli during sleep.

Previous studies have demonstrated that motor activity during sleep is lateralized to the nondominant hand. There are two basic theories concerning this phenomenon: 1) The nondominant hemisphere is nonspecifically more alert or responsive than the dominant one, and 2) the lateralization to the nondominant side is task specific, reflecting the spatially oriented mode of information processing that is responsible for movements during sleep. We examined the motor responses to auditory stimuli during waking and sleep of 10 right-handed healthy subjects, who were instructed to switch off a tone stimulus by pressing a transducer that was attached to each hand. Sleep stage scoring was performed according to Rechtschaffen and Kales's criteria. During wakefulness and in all stages of sleep, with and without alpha activity occurring after stimulus onset, the dominant hand was used more, but during nonrapid eye movement S1 sleep the difference was not statistically significant. When alpha activity was present in the electroencephalogram after stimulus onset, the responses were significantly more lateralized to the right hand than when there was no alpha activity. During an actimetric home recording of both wrists of the subjects, there was an excess of left-sided movements during sleep as compared to waking. The results do not support the idea that the right hemisphere is generally more responsive than the left during sleep. They are, however, in accordance with the hypothesis that spatial information processing is a crucial factor in the nondominant lateralization of spontaneous sleep movements.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1994

Upper airway obstruction in hypothyroidism.

OBJECTIVES: To determine the occurrence and frequency of nocturnal upper airway obstruction in hypothyroidism. DESIGN: A case-control study of patients with newly diagnosed hypothyreosis and euthyroid subjects who had been selected from the population register. The subjects underwent sleep recordings with a static-charge-sensitive bed (SCSB). SETTING: Turku University Hospital and Research and Development Unit, Social Insurance Institution, Turku, Finland. SUBJECTS: Twenty six consecutive patients underwent sleep recordings with SCSB and a pulse oximeter. One hundred and eighty-eight euthyroid subjects who were previously studied with the SCSB were used as controls. MAIN OUTCOME MEASURES: In a multivariate analysis, hypothyroidism, gender, age, and body mass index (BMI) were considered as predictors for the occurrence of nocturnal breathing abnormalities. RESULTS: Nocturnal breathing abnormalities were frequent in both groups. Fifty per cent of the hypothyroid patients and 29.3% of the control subjects had at least some episodes of partial or complete upper airway obstruction (P = 0.04). Severe obstruction with episodes of repetitive apnoea was present in 7.7% of the patients and in 1.5% of the controls. The multivariate analysis revealed that the presence of hypothyroidism did not significantly (P = 0.06), and independently of age, BMI or gender, predict nocturnal breathing abnormalities, whereas obesity (P < 0.0001) and male gender (P = 0.0001) were independent and significant predictors. CONCLUSIONS: The incidence of nocturnal upper airway obstruction is increased in hypothyroidism, but is related to obesity and male gender rather than to hypothyroidism per se.

Adult↗
PubMed1993

Pharyngeal CT studies in patients with mild or severe upper airway obstruction during sleep.

The upper airway cross-sectional areas were studied with pharyngeal computed tomography (CT) at the nasopharyngeal, velopharyngeal, tongue base and hyoid bone levels in 119 consecutively investigated patients with a snoring complaint. According to their findings in an all-night static charge sensitive bed (SCSB) recording, the subjects were divided into four equally sized groups with increasing severity of nocturnal breathing disturbance. The body mass index (BMI) increased and the minimal cross-sectional area at the velopharyngeal level decreased consistently as a function of the severity of nocturnal breathing disturbance. The minimal cross-sectional area at the hyoid bone level showed a biphasic trend, with an initial decrease but a final increase, as the degree of nocturnal breathing disturbance aggravated. The results contradict the idea of gradually increasing anatomical narrowing of the upper airways in general as the nocturnal breathing disturbance exacerbates and support the concept of two anatomically determined entities of partial and complete upper airway obstruction during sleep.

Airway Obstruction↗
PubMed1992

Sleep quality in preeclampsia.

OBJECTIVE: Our goal was to study the sleep quality in women with preeclampsia with a special reference to nocturnal body movement activity. STUDY DESIGN: Sleep quality was evaluated in nine women with preeclampsia and eight women with normal term pregnancy by means of questionnaires and by recording the nocturnal body movement activity with the static charge-sensitive bed. RESULTS: Subjective sleep complaints were similar in both groups. The total movement time and the total frequency of body movements in bed were, however, significantly increased in the preeclamptic group. CONCLUSION: The study suggests that sleep is impaired in preeclamptic subjects.

Adult↗
PubMed1992

Partial upper airway obstruction during sleep. Studies with the static charge-sensitive bed (SCSB).

Nocturnal respiration, the ballistocardiogram, and body movement activity were studied with the static charge-sensitive bed (SCSB) in snorers who represented a wide range of severity of sleep-related upper airway obstruction. The emphasis was to evaluate the performance of the SCSB as a noninvasive tool for assessing nocturnal breathing disturbances. The results show that periodic episodes of obstructive apnea or hypopnea can reliably be monitored with the method. Additional breathing abnormalities suggesting the presence of increased respiratory resistance and increased body motility were frequently observed not only in OSAS patients but also in snorers without apnea. Permanent morphological abnormalities of the upper airways were observed in pharyngeal CT in patients with OSAS but also in subjects with severe partial obstruction without apnea. The findings in the SCSB recordings clearly illustrate that there is a functional continuum from partial to complete upper airway obstruction during sleep. However, the structural differences of the upper airways observed between subjects with partial airway obstruction and with OSAS suggest that partial obstruction without apnea cannot always be considered as heralding the development of the OSAS, but rather as a separate entity, which may produce the same clinical signs and symptoms as in the OSAS. The SCSB turned out to be a simple but sensitive method to detect complete and partial upper airway obstruction during sleep. The SCSB may optimally yield information beyond reach of more complex recording systems. Nonapneic SCSB findings may have particular significance for the evaluation of preclinical stages of sleep-related upper airway obstruction.

Airway Obstruction↗
PubMed1992

Respiratory variation of the ballistocardiogram during increased respiratory load and voluntary central apnoea.

Heavy snoring is associated with increased respiratory variation of the ballistocardiogram (BCG). The cause for this association is not known. Although the BCG is a sensitive method to measure myocardial performance, the validity of the signal as a marker of snoring-related haemodynamic changes has not been tested. The aim of this study was to investigate whether ballistocardiographic respiratory variation (BRV) correlates with intrathoracic pressure variation (IPV). The BRV and the IPV were measured in five healthy, normal-weight, awake adults during normal breathing, during breath-holding with constant intrathoracic pressure, and during breathing against increased respiratory resistance (high IPV). The BCG was recorded with the static charge-sensitive bed (SCSB) and the intrathoracic pressure with an oesophageal balloon. The mean BRV was significantly lower during central apnoea than during free breathing (8.2 versus 29.4% p less than 0.0001). When breathing against increased respiratory load, the BRV increased in a linear manner as function of the IPV (r = 0.68, p less than 0.01). There was significant interindividual variation in the response. We conclude that changes in the BRV reflect changes in the IPV. Further studies are needed to evaluate whether the BCG could be used as a noninvasive alternative to the oesophageal balloon in monitoring changes of respiratory resistance during heavy snoring.

Adult↗
PubMed1989

Partial upper airway obstruction in sleep after uvulopalatopharyngoplasty.

Uvulopalatopharyngoplasty is the treatment of choice for selected patients with obstructive sleep apnea, although the response to surgery is variable. We measured, in addition to obstructive apnea, the frequency of sleep-related partial upper airway obstruction in 11 patients with the obstructive sleep apnea syndrome both before and after uvulopalatopharyngoplasty. Partial obstruction was detected indirectly by recording the secondary hemodynamic changes and respiratory stimulation with the static charge sensitive bed. The frequency of obstructive apnea episodes was reduced from 56.3% to 18.4% by the operation, while the episodes of increased respiratory resistance rose from 3.6% to 20.4%. The various breathing anomalies decreased significantly, although they were still present during 75.6% of the recording time. The results suggest that uvulopalatopharyngoplasty substantially reduces the frequency of obstructive apnea, some of which persists as partial obstruction. The persistent partial obstruction may be the key factor contributing to further pharyngeal narrowing and a recurrence of obstructive sleep apnea syndrome.

Airway Obstruction↗