Biomedical subjects

R L Horner

Publications and source records attributed to R L Horner.

At least 55 records · Page 3Linked to original sources

PubMed1990

The persistence of a respiratory 'personality' into stage IV sleep in man.

The characteristic pattern of breathing for an individual when awake at rest may be due to forebrain influences upon breathing. To examine this hypothesis we have studied the breathing pattern in 18 healthy subjects during relaxed wakefulness (W) and during Stage 4 sleep (S4), when forebrain influences upon breathing are absent or minimal. Inspiratory and expiratory times, respiratory frequency, tidal volume, and ventilation were quantified noninvasively by respiratory inductance plethysmography. The stability of respiratory variables between W and S4 sleep was tested within individuals. The results show that (i) individuals breathe differently from each other when awake and when in S4 sleep; the range between individuals during sleep being as large as it is when awake; (ii) differences in breathing pattern between two S4 periods within an individual are relatively small; (iii) the characteristic breathing pattern of an individual when awake tends to be maintained in S4 sleep. This persistence of a respiratory 'personality' into S4 sleep probably indicates that there are individual differences in respiratory rhythm generation in the absence of any forebrain influences upon breathing.

Adult↗

PubMed1990

Effect on breathing of raising end-expiratory lung volume in sleeping laryngectomized man.

In animals, tonic vagal activity from lung receptors provides a means by which changes in end-expiratory lung volume can influence respiratory timing. We wished to examine whether increasing the end-expiratory lung volume within the tidal volume range had a similar effect in man. In order to minimize behavioral influences on breathing, the study was performed in subjects during deep non-rapid eye movement sleep. Five laryngectomized subjects were chosen for the study since their permanent tracheal stomata allow simple, airtight connection to respiratory apparatus and avoided problems with glottic closure. During EEG-documented sleep, end-expiratory volume was increased by up to 350 ml with the addition of expiratory threshold loads of 1 to 10 cm H2O. End-expiratory volume increased linearly with expiratory pressure. Inspiratory and expiratory times (TI and TE) were not affected by increases in end-expiratory volume. Tidal volume (VT) was decreased such that end-inspiratory volume remained unchanged. The decrease in VT may result from a reduction in inspiratory muscle efficiency at a higher lung volume. The results of the study provide no evidence that tonic vagal afferent information from the lungs is important in controlling respiratory rhythm within the tidal volume range in man when behavioral control of breathing is minimized.

Adult↗

PubMed1989

Pharyngeal size and shape during wakefulness and sleep in patients with obstructive sleep apnoea.

Computed tomography has been used to study the pharyngeal airway during tidal breathing in wakefulness and during obstructive apnoeas in Non-REM sleep in patients with obstructive sleep apnoea. In supine subjects, contiguous transverse 10 mm sections were taken perpendicular to the posterior pharyngeal wall with a 2.1 s scan time. Studies during wakefulness showed that the narrowest section of the pharyngeal airspace was in the region posterior to the soft palate and that the minimal airway cross-sectional areas were significantly reduced in the group of patients with obstructive sleep apnoea compared to the group of control subjects without obstructive sleep apnoea. The studies during sleep showed that in all patients, the airspace posterior to the soft palate was a site of obstructive apnoeas. The length of the obstructed segment varied between patients, extending below the level of the soft palate in half the patient group. Airway narrowing and obstruction was due to posterior displacement of the soft palate and the tongue in the majority of patients, although lateral displacement of the pharyngeal walls was also observed. No occlusion was observed in the laryngopharynx although there was narrowing of oro- and laryngopharyngeal apertures below the site of obstruction during obstructive apnoeas. The size of the oropharyngeal airspace during wakefulness did not predict the presence of airway occlusion below the level of the soft palate when asleep. The variability between patients in the site(s) of upper airway obstruction during obstructive apnoeas have important implications for the choice of appropriate treatment in patients with obstructive sleep apnoea.

Adult↗

PubMed1989

Sites and sizes of fat deposits around the pharynx in obese patients with obstructive sleep apnoea and weight matched controls.

It has been suggested that deposition of fat in the soft tissues surrounding the upper airway may be an important factor in the pathogenesis of obstructive sleep apnoea (OSA) in obese subjects. We have used magnetic resonance imaging to determine the site(s) and size(s) of fat deposits around the upper airway in six obese patients with OSA (116-153% of ideal body weight) and five weight-matched controls without OSA (107-152% of ideal body weight). In all subjects, large deposits of fat were present postero-lateral to the oropharyngeal airspace at the level of the soft palate. Significantly more fat was present in these regions in the patients with OSA (p = 0.03). Fat deposits in the soft palate were observed in 4 of the 6 patients with OSA but none of the controls. Fatty streaks were observed in the tongue in 2 of the 5 controls and 3 of the 6 patients with OSA. Fat deposits were observed anterior to the laryngopharyngeal airspace, in submental regions, in all obese subjects. This study shows that more fat is present in those areas surrounding the collapsable segment of the pharynx in patients with OSA, compared to equally obese control subjects without OSA.

Adipose Tissue↗

PubMed1988

The effect of human heart-lung transplantation upon breathing at rest and during sleep.

We have assessed the contribution of intrathoracic pulmonary nerves to the control of breathing in humans. During relaxed wakefulness and during sleep the level, pattern and variability of breathing have been quantified in 8 healthy patients 1 month to 2 years after combined heart--lung transplantation. These data have been compared with similar data from both of 2 matched control groups; either healthy normal controls, or healthy patients after heart transplantation alone. We found no significant differences in the mean levels of respiratory variables between the 3 groups either during relaxed wakefulness or sleep. There were no significant differences between groups (other than would be expected by chance alone) either in the variability of breathing, or in the shapes of the frequency distributions of respiratory variables during these states. There were no respiratory disorders associated with sleep nor any disturbances in blood gases in any group. We conclude that in man breathing is remarkably normal, during relaxed wakefulness and during sleep, after chronic pulmonary denervation. When the ventilatory demands are minimal the human ventilation system functions normally in the absence of a control loop involving pulmonary proprioceptors and the medullary respiratory centres.

Adolescent↗

PubMed1988

The effect of lung inflation on breathing in man during wakefulness and sleep.

To determine whether the Hering-Breuer inflation reflex could be demonstrated in the presence and absence of behavioral influences on breathing, lung inflation was performed via the tracheal stoma in eleven laryngectomized subjects: seven seated at rest with their eyes closed and six recumbent during their deepest non-rapid eye movement sleep. Laryngectomized subjects were chosen for study since their permanent tracheal stoma and absence of a glottis abolished the sensation of inflation in the upper airways, avoided problems with glottic closure and allowed simple, airtight connection to respiratory apparatus. At rest awake, inflation volumes of 500-3050 ml caused no reproducible apnea. During EEG-documented sleep, the inflation reflex was tested on 75 occasions using inflation volumes of 540-2100 ml. On the 66 occasions not associated with subject arousal inflations exceeding approximately 1 L produced apnea terminated by inspiration; greater volumes gave longer apneas. At the end of the study the subjects were woken and retested; no reproducible apnea was found. We conclude that the Hering-Breuer inflation reflex can be demonstrated above the resting tidal volume range in adult man in the absence of the behavioral control of breathing.

Humans↗

PubMed1978

Medical and surgical importance of the arterial blood supply of the thumb.

The arterial supply of the thumb was studied in 50 cadaver hands. In 80% the princeps pollicis artery was the first palmar metacarpal artery, a major branch of the deep radial arch. In 50% of the specimens the princeps pollicis artery also supplied the proper radial digital artery to the index finger. Variations of the thumb arterial patterns were present in 25%. In 75% there was a single end-arterial blood supply to the thumb. The anatomic findings are correlated with problems of radial artery injections, thrombosis, and surgical injury to illustrate the clinical importance of the princeps pollicis artery.

Adult↗

PubMed1974