The American review of respiratory disease
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Am. Rev. Respir. Dis. · Aug 1991
Three-dimensional upper airway computed tomography in obstructive sleep apnea. A prospective study in patients treated by uvulopalatopharyngoplasty.
The success of uvulopalatopharyngoplasty in treating obstructive sleep apnea varies considerably. Some of this variability may be accounted for by differences in the site of upper airway narrowing. To determine whether preoperative awake upper airway and soft tissue volumes predict the response to uvulopalatopharyngoplasty, preoperative awake computed tomograms (CT) of the upper airway were performed on 60 consecutive patients with symptomatic obstructive sleep apnea. ⋯ Patients who had a good response had a smaller oropharyngeal cross-sectional area (p less than 0.01), a smaller upper airway volume (p less than 0.05), a smaller upper airway to tongue volume ratio (p less than 0.01), and a smaller oropharynx to soft palate volume ratio (p less than 0.05). Obese patients with obstructive sleep apnea have larger tongues and smaller upper airways relative to tongue and soft palate size. Patients with smaller upper airways, particularly relative to tongue and soft palate size, have a good response to uvulopalatopharyngoplasty.
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Am. Rev. Respir. Dis. · Jul 1991
The effects of positive end-expiratory pressure on respiratory resistance in patients with the adult respiratory distress syndrome and in normal anesthetized subjects.
We investigated the effects of positive end-expiratory pressure (PEEP) upon respiratory resistance during mechanical ventilation in 21 subjects anesthetized for surgery (normal subjects) and in 11 patients with the adult respiratory distress syndrome (ARDS). We measured tracheal pressure (Ptr) near the end of the endotracheal tube through a 1.5-mm ID catheter and airflow (V) at 0, 5, and 10 cm H2O PEEP (normal subjects) and at 0, 5, 10, 15, and 20 cm H2O PEEP (patients with ARDS). We computed respiratory system static elastance (Estrs), maximal (Rrsmax) and minimal (Rrsmin) inspiratory resistance by the end-inspiratory occlusion method during constant-flow inflation. ⋯ We found that (1) at PEEP 0, expiratory resistances (Rrsexp50: 7.38 +/- 1.92 versus 5.35 +/- 1.97 cm H2O. L-1.s) and DRrs (3.08 +/- 1.9 versus 1.66 +/- 0.77 cm H2O. L-1.s) were significantly higher in the ARDS group than in the normal group.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Jun 1991
Randomized Controlled Trial Clinical TrialDistribution of ventilation and perfusion with different modes of mechanical ventilation.
We compared pulmonary gas exchange during synchronized intermittent mandatory ventilation (SIMV), pressure support ventilation (PSV), and airway pressure release ventilation (APRV). Nine subjects aged 56 to 75 yr were studied from 4 to 19 h after cardiac operations. When subjects were ready to be weaned from mechanical ventilation their ventilation-perfusion distribution was estimated using the multiple inert gas elimination technique during SIMV. ⋯ Minute ventilation was lower during APRV (7.5 +/- 0.07 L/min) than during SIMV (9.4 +/- 0.6 L/min) and PSV (9.0 +/- 0.5 L/min) (p less than 0.05). Hemodynamic variables were similar during all three modes. We conclude that all three modes provide acceptable oxygenation and ventilatory support.
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Am. Rev. Respir. Dis. · Jun 1991
Upper airway collapsibility in snorers and in patients with obstructive hypopnea and apnea.
During sleep, mild reduction in inspiratory airflow is associated with snoring, whereas obstructive hypopneas and apneas are associated with more marked reductions in airflow. We determined whether the degree of inspiratory airflow reduction was associated with differences in the collapsibility of the upper airway during sleep. Upper airway collapsibility was defined by the critical pressure (Pcrit) derived from the relationship between maximal inspiratory airflow and nasal pressure. ⋯ Moreover, higher levels of Pcrit were associated with lower levels of maximal inspiratory airflow during tidal breathing during sleep (p less than 0.005). We conclude that differences in upper airway collapsibility distinguish among groups of normal subjects who snore and patients with periodic hypopneas and apneas. Moreover, the findings suggest that small differences in collapsibility (Pcrit) along a continuum are associated with reduced airflow and altered changes in pattern of breathing.