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Biomedical subjects

F G Issa

Publications and source records attributed to F G Issa.

33 records · Page 2Linked to original sources
PubMed1986

The immediate effects of nasal continuous positive airway pressure treatment on sleep pattern in patients with obstructive sleep apnea syndrome.

We studied the immediate effects of continuous positive airway pressure (CPAP) applied nasally on the pattern of sleep in 12 patients, aged 30-58 years, with obstructive sleep apnea syndrome. All patients demonstrated a moderate to severe syndrome on the control night; apnea index ranged 28-83 apneas/h sleep. Nasal CPAP completely abolished all obstructive apneas and allowed apnea-free breathing in all 12 patients. Nasal CPAP had a marked effect on the sleep pattern. It significantly reduced stage I/II non-rapid eye movement (NREM) sleep and markedly increased stage III/IV NREM and REM sleep on the first treatment night. Stage I/II NREM sleep decreased from a control of 62.7 +/- 2.3% to 29.1 +/- 2.3% on the first treatment night. Stage III/IV NREM sleep increased from a control of 6.7 +/- 1.6% to 31.5 +/- 1.6%. The rebound in this sleep stage was especially marked in 3 patients aged 55-58 years. REM sleep increased from a control of 18.4 +/- 2.0% to 30.6 +/- 2.0% on the first treatment night. There was an increase in REM density. All patients were treated for another 2 nights and their sleep pattern analyzed on the third night. All sleep stages were still significantly different to the control night. The possible mechanisms involved are discussed.

Adult↗
PubMed1986

Influence of negative pressure applied to the upper airway on the breathing pattern in unanesthetized awake dogs.

We examined the influence of changes in upper airway pressure on the breathing pattern in 5 unanesthetized awake dogs. The dogs breathed through an endotracheal tube or through a comfortably fitting fiberglass snout mask. With matched resistances and volume of the dead space, the inspiratory duration, tidal volume, and minute ventilation were higher during nasal breathing compared to tracheal breathing. Nasal and tracheal occlusion produced prolongation of inspiration in the first occluded breathing attempt, but the prolongation was more marked in nasal occlusion tests. Augmentation of genioglossus muscle activity occurred on the first occluded breath in nasal but not tracheal occlusion. In another series of experiments, negative pressure was applied to the isolated upper airway while the dog breathed through a tracheostomy tube. Negative pressure caused a prolongation of inspiratory duration which was proportional to the level of the applied pressure. However, the prolongation of inspiratory duration was significantly more marked when application of negative pressure was timed simultaneously with tracheal occlusion. Our results demonstrate that the upper airway has a powerful effect on the control of breathing, which becomes more evident during tracheal occlusion.

Airway Resistance↗
PubMed1986

Upper airway dilating forces during wakefulness and sleep in dogs.

We measured the pressure within an isolated segment of the upper airway in three dogs during wakefulness (W), slow-wave sleep (SWS) and rapid-eye-movement (REM) sleep. Measurements were taken from a segment of the upper airway between the nares and midtrachea while the dog breathed through a tracheostoma. These pressure changes represented the sum of respiratory-related forces generated by all muscles of the upper airway. The mean base-line level of upper airway pressure (Pua) was -0.5 +/- 0.03 cmH2O during W, increased by a mean of 2.1 +/- 0.2 cmH2O during SWS, and was variable during REM sleep. The mean inspiratory-related phasic change in Pua was -1.2 +/- 0.1 cmH2O during wakefulness. During SWS, this phasic change in Pua decreased significantly to a mean of -0.9 +/- 0.1 cmH2O (P less than 0.05). During REM sleep, the phasic activity was extremely variable with periods in which there were no fluctuations in Pua and others with high swings in Pua. These data indicate that in dogs the sum of forces which dilate the upper airway during W decreases during SWS and REM sleep. The consistent coupling between inspiratory drive and upper airway dilatation during wakefulness persists in SWS, but is frequently uncoupled during REM sleep.

Animals↗
PubMed1986

Reversal of central sleep apnea using nasal CPAP.

Based on the theory that obstructive (OSA) and central (CSA) sleep apneas share common pathophysiologic mechanisms, we attempted to treat eight patients with predominantly CSA by continuous positive airway pressure (CPAP). All patients exhibited repetitive episodes of CSA and mixed sleep apneas (MSA) in the supine position with a mean duration of 23.7 +/- 0.7 s and 34.5 +/- 1.3 s, respectively. The pattern of apnea changed when the subject lay in the lateral position. Five patients were observed to develop OSA in the lateral position with a mean duration of 27.2 +/- 1.5 s, while the other three patients snored continuously. High levels of CPAP (range 9.0 to 16.5 cm H2O) prevented all CSA and MSA and resulted in quiet breathing in all eight patients. Intermediate levels of CPAP produced firstly MSA, then purely OSA and/or continuous snoring. Low levels of nasal CPAP also prevented OSA and snoring occurring in the lateral posture in all subjects (range 2.0 to 8.3 cm H2O). Three patients are currently on home CPAP therapy for a range of four to 36 months. We conclude that upper airway collapse in the supine posture has a key role in the induction of CSA. We suggest that a reflex inhibition of respiration through activation of supraglottic mucosal receptors during passive oropharyngeal airway closure caused CSA in these patients.

Adult↗
PubMed1985

Respiratory muscle activity and thoracoabdominal motion during acute episodes of asthma during sleep.

To understand the mechanisms of respiratory system compensation to internal loading during sleep, all-night sleep studies were performed in 10 patients with chronic stable asthma. We used noninvasive measurements to identify the onset of increased airway resistance in sleep. In each sleep study, we recorded arterial oxygen saturation (SaO2) and an array of electromyograms (diaphragm, external intercostal and sternomastoid) as well as thoracoabdominal motion. Only 4 patients developed acute asthma during sleep. A total of 6 such attacks were recorded. The attacks were detected by audible wheeze, augmentation of diaphragm, external intercostal and sternomastoid activity, associated with distinctive changes in thoracoabdominal motion. The duration of these acute asthmatic attacks ranged between 20 and 140 min. One attack started in stage I/II non-rapid-eye-movement (NREM) sleep, 3 in stage III/IV NREM sleep, and 2 in rapid-eye-movement (REM) sleep. Acute asthma in NREM sleep resulted in a paradoxical inward displacement of the abdomen during early inspiration. Attacks occurring during REM sleep resulted in rib cage inward displacement during inspiration. Attacks occurring during REM sleep resulted in rib cage inward displacement during inspiration. Attacks occurring in both NREM and REM sleep did not result in a significant fall in SaO2. We conclude that acute internal respiratory loading during sleep can provoke different compensatory mechanisms in order to provide adequate ventilation in adult asthmatics.

Abdominal Muscles↗
PubMed1985

Obstructive sleep apnea.

This chapter provides an account of obstructive sleep apnea that is designed for clinicians. Current ideas about the mechanism of upper airway obstruction are reviewed, and the clinical features are discussed in a manner intended to facilitate the clinical assessment of such patients. Various forms of treatment are reviewed, with major emphasis given to the use of nasal positive airway pressure, a form of therapy developed by the authors.

Airway Obstruction↗
PubMed1984

Upper airway closing pressures in obstructive sleep apnea.

We studied 18 patients with obstructive sleep apnea (OSA). Each subject slept while breathing through the nose with a specially designed valveless breathing circuit. Low levels of continuous positive airway pressure (CPAP) applied through the nose (2.5-15.0 cmH2O) prevented OSA and allowed long periods of stable stage III/IV sleep and rapid-eye-movement (REM) sleep. Externally applied complete nasal occlusion while the upper airway was patent resulted in upper airway closure during inspiration which was identified by a sudden deviation of nasal pressure from tracheal or esophageal pressure. The level of upper airway closing pressure (UACP) did not change throughout the occlusion test, suggesting that upper airway dilator muscles do not respond to asphyxia during sleep. The upper airway was more collapsible during stage I/II non-rapid-eye-movement (NREM) and REM sleep compared with stage III/IV NREM sleep. The pooled mean UACP was 3.1 +/- 0.4 cmH2O in stage I/II NREM, 4.2 +/- 0.2 cmH2O in stage III/IV NREM, and 2.4 +/- 0.2 cmH2O in REM sleep. Nasal occlusion at successively higher levels of CPAP did not alter the level of UACP in stage I/II NREM and REM sleep but resulted in the upper airway becoming more stable in stage III/IV NREM sleep, suggesting a reflex which augments the tone of upper airway dilator muscles.

Adult↗
PubMed1984

Upper airway closing pressures in snorers.

We studied 14 subjects who were selected to represent the broad range of severity of snoring: group A, four subjects who gave a history of snoring only when provoked by nasal obstruction or alcohol intake; group B, six subjects who typically snored for long periods each night; and group C, four subjects who snored heavily all night and who typically experienced a few episodes of obstructive apnea (mean apnea index 4 apneas/h). Low levels of nasal continuous positive airway pressure (CPAP) (range, 2.0-6.0 cmH2O; mean, 4.0 cmH2O) prevented snoring. Nasal occlusion caused upper airway closure during inspiratory efforts in all 14 subjects. There was a relationship between the clinical severity of snoring and the upper airway closing pressure (UACP). Upper airway closure occurred at greater suction pressures in group A than in group C but there was overlap between the three categories. The upper airway was consistently more collapsible in rapid-eye-movement sleep than in non-rapid-eye-movement sleep. There was little evidence of breath-by-breath improvement of upper airway stability during sustained asphyxia, the UACP remaining constant despite marked increases in drive to the diaphragm. In five subjects UACP was measured following alcohol intake. Alcohol reduced upper airway stability in all subjects in a dose-dependent manner.

Adult↗
PubMed1983

Arousal and breathing responses to airway occlusion in healthy sleeping adults.

The arousal and breathing responses to total airway occlusion during sleep were measured in 12 normal subjects (7 males and 5 females) aged 25-36 yr. Subjects slept while breathing through a specially designed nosemask, which was glued to the nose with medical-grade silicon rubber. The lips were sealed together with a thin layer of Silastic. The nosemask was attached to a wide-bore (20 mm ID) rigid tube to allow a constant-bias flow of room air from a blower. Total airway occlusion was achieved by simultaneously inflating two rubber balloons fixed in the inspiratory and expiratory pipes. A total of 39 tests were done in stage III/IV nonrapid-eye movement (NREM) sleep in 11 subjects and 10 tests in rapid-eye-movement (REM) sleep in 5 subjects. The duration of total occlusion tolerated before arousal from NREM sleep varied widely (range 0.9-67.0 s) with a mean duration of 20.4 +/- 2.3 (SE) s. The breathing response to occlusion in NREM sleep was characterised by a breath-by-breath progressive increase in suction pressure achieved by an increase in the rate of inspiratory pressure generation during inspiration. In contrast, during REM sleep, arousal invariably occurred after a short duration of airway occlusion (mean duration 6.2 +/- 1.2 s, maximum duration 11.8 s), and the occlusion induced a rapid shallow breathing pattern. Our results indicate that total nasal occlusion during sleep causes arousal with the response during REM sleep being more predictable and with a generally shorter latency than that in NREM sleep.

Adult↗
PubMed1983

Remission of severe obesity-hypoventilation syndrome after short-term treatment during sleep with nasal continuous positive airway pressure.

Two patients with the Pickwickian syndrome and with life-threatening sleep hypoxemia were treated with continuous positive airway pressure (CPAP) applied through the nares only during sleep periods. Each patient presented with severe daytime somnolence, disturbed sleep, nocturnal confusion, and daytime awake cardiorespiratory failure (PaCO2, 63 and 55 mmHg). Both patients demonstrated grossly abnormal breathing during sleep with severe sleep hypoxemia, the arterial oxyhemoglobin saturation (SaO2%) falling repetitively to levels below 50%. One patient had a hypoxemic convulsion during the initial sleep evaluation. Low levels (3.5 and 8.0 cm H2O) of continuous positive airway pressure, when applied via a comfortable nose mask, prevented occlusive apnea and obstructive hypopnea during sleep in both patients and maintained steady levels of arterial oxyhemoglobin saturation. There was rapid recovery of mental function and loss of cardiorespiratory failure within 3 days of treatment. After short-term treatment with nocturnal CPAP therapy (23 days and 35 days) both patients were able to sleep, unaided, without sleep-induced upper airway occlusion with arterial oxyhemoglobin levels sustained above 80%. We conclude that nasal CPAP therapy during sleep is an effective noninvasive therapy for patients with the Pickwickian syndrome, and may lead to a stable remission of the underlying severe disordered breathing in sleep.

Aged↗
PubMed1982

Alcohol, snoring and sleep apnea.

We studied the effect of alcohol ingestion on sleep-induced breathing abnormalities and arterial oxyhaemoglobin saturation in seven patients with a range of sleep-induced upper airway occlusion. The characteristics of each patient's sleep-induced breathing abnormality was established on one or more control all-night studies, and then a further all-night study was done immediately following alcohol ingestion. Alcohol increased the duration and frequency of the occlusive episodes in five patients with obstructive sleep apnoea, and resulted in a marked increase in the degree of hypoxaemia in the first hour of sleep. In two patients with benign chronic snoring, alcohol induced frank obstructive sleep apnoea during the first hour of sleep. We suggest that the increased tendency to develop obstructive apnoea after alcohol is the result of alcohol-induced oropharyngeal muscle hypotonia, while the increased duration of obstructive apnea is the result of alcohol-induced depression of arousal mechanisms.

Adult↗
PubMed1981

Reversal of obstructive sleep apnoea by continuous positive airway pressure applied through the nares.

Five patients with severe obstructive sleep apnoea were treated with continuous positive airway pressure (CPAP) applied via a comfortable nose mask through the nares. Low levels of pressure (range 4.5-10 cm H2O) completely prevented upper airway occlusion during sleep in each patient and allowed an entire night of uninterrupted sleep. Continuous positive airway pressure applied in this manner provides a pneumatic splint for the nasopharyngeal airway and is a safe, simple treatment for the obstructive sleep apnoea syndrome.

Adolescent↗
PubMedDate not supplied

Home treatment of obstructive sleep apnoea with continuous positive airway pressure applied through a nose-mask.

Continuous positive airway pressure (CPAP) applied through the nose completely prevented obstructive apnoea during all night testing in 50 patients with severe obstructive apnoea. In early 1981, we began a home treatment trial of nasal CPAP. Patients were treated in hospital for 3 to 5 nights, a period in which they were trained to fit the custom made nose-mask used to provide nasal CPAP. Patients subsequently continued treatment at home. Daytime somnolence resolved within days of starting therapy, and did not recur while the nasal CPAP unit was used on a regular basis. At present, we have 35 patients who have been on therapy for periods ranging between 3 and 30 months. Although each patient has displayed a reduction of severity of the underlying sleep apnoea when tested without nasal CPAP, the majority continue to require regular nightly nasal CPAP. In a few patients, treatment with nasal CPAP appeared to help in weight control such that obstructive apnoea and snoring have resolved. Nasal CPAP is a safe, fully effective therapy for obstructive apnoea, and can be used indefinitely by the patient at home.

Adolescent↗