Article

Lung volume and collapsibility of the passive pharynx in patients with sleep-disordered breathing

The University of Calgary, Calgary, Alberta, Canada
Journal of Applied Physiology (Impact Factor: 3.43). 11/2007; 103(4):1379-85. DOI: 10.1152/japplphysiol.00026.2007
Source: PubMed

ABSTRACT Lung volume dependence of pharyngeal airway patency suggests involvement of lung volume in pathogenesis of obstructive sleep apnea. We examined the structural interaction between passive pharyngeal airway and lung volume independent of neuromuscular factors. Static mechanical properties of the passive pharynx were compared before and during lung inflation in eight anesthetized and paralyzed patients with sleep-disordered breathing. The respiratory system volume was increased by applying negative extrathoracic pressure, thereby leaving the transpharyngeal pressure unchanged. Application of -50-cmH(2)O negative extrathoracic pressure produced an increase in lung volume of 0.72 (0.63-0.91) liter [median (25-75 percentile)], resulting in a significant reduction of velopharyngeal closing pressure of 1.22 (0.14-2.03) cmH(2)O without significantly changing collapsibility of the oropharyngeal airway. Improvement of the velopharyngeal closing pressure was directly associated with body mass index. We conclude that increase in lung volume structurally improves velopharyngeal collapsibility particularly in obese patients with sleep-disordered breathing.

0 Followers
 · 
74 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Neuromuscular blocking agents are used to facilitate tracheal intubation in patients undergoing ambulatory surgery. The use of high-dose neuromuscular blocking agents to achieve muscle paralysis throughout the case carries an increased risk of residual post-operative neuromuscular blockade, which is associated with increased respiratory morbidity. Visually monitoring the train-of-four (TOF) fade is not sensitive enough to detect a TOF fade between 0.4 and 0.9. A ratio <0.9 indicates inadequate recovery. Quantitative neuromuscular transmission monitoring (e.g., acceleromyography) should be used to exclude residual neuromuscular blockade at the end of the case. Residual neuromuscular blockade needs to be reversed with neostigmine, but it's use must be guided by TOF monitoring results since deep block cannot be reversed, and neostigmine administration after complete recovery of the TOF-ratio can induce muscle weakness. The development and use of new selectively binding reversal agents (sugammadex and calabadion) warrants reevaluation of this area of clinical practice.
    12/2014; 4(4):290-302. DOI:10.1007/s40140-014-0073-6
  • [Show abstract] [Hide abstract]
    ABSTRACT: Caudal tracheal displacement (TD) leads to improvements in upper airway (UA) function and decreased collapsibility. To better understand the mechanisms underlying these changes, we examined effects of TD on peri-pharyngeal tissue stress distributions (i.e. extra-luminal tissue pressure, ETP), deformation of its topographical surface (UA lumen geometry) and hyoid bone position. We studied thirteen supine, anaesthetized, tracheostomized, spontaneously breathing, adult male New Zealand white rabbits. Graded TD was applied to the cranial tracheal segment from 0 to ~10 mm. ETP was measured at six locations distributed around/along the length of the UA covering three regions: tongue, hyoid and epiglottis. Axial images of the UA (nasal choanae to glottis) were acquired with computed tomography and used to measure lumen geometry (UA length; regional cross-sectional area, CSA) and hyoid bone displacement. TD resulted in non-uniform decreases in ETP (generally greatest at tongue region), ranging from -0.07(-0.11 to -0.03) [linear mixed-effects model slope(95%CI)] to -0.27(-0.31 to -0.23) cmH2O per mm of TD across all sites. UA length increased by 1.6(1.5 to 1.8) %/mm accompanied by non-uniform increases in CSA (greatest at hyoid region) ranging from 2.8(1.7 to 3.9) to 4.9(3.8 to 6.0) %/mm. The hyoid bone was displaced caudally by 0.22(0.18 to 0.25) mm/mm of TD. In summary, TD imposes a load on the UA that results in heterogeneous changes in peri-pharyngeal tissue stress distributions and resultant lumen geometry. The hyoid bone may play a pivotal role in redistributing applied caudal tracheal loads, thus modifying tissue deformation distributions and determining resultant UA geometry outcomes.
    Journal of Applied Physiology 02/2014; 116(7):746-756. DOI:10.1152/japplphysiol.01245.2013 · 3.43 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Intraoperative recruitment manoeuvres (RMs) combined with PEEP reverse the decrease in functional residual capacity (FRC) associated with anaesthesia and improve intraoperative oxygenation. Whether these benefits persist after operation remains unknown. We tested the hypothesis that intraoperative RMs associated with PEEP improve postoperative spirometry including FRC and reduce the incidence of postoperative hypoxaemia in morbidly obese (MO) patients undergoing laparoscopic gastric bypass. After IRB approval and informed consent, 50 MO patients undergoing laparoscopic gastric bypass under volume-controlled ventilation (tidal volume 6 ml kg(-1) of IBW) were randomly ventilated with either 10 cm H2O PEEP or with 10 cm H2O PEEP and one RM carried out after induction of pneumoperitoneum, and another after exsufflation. Anaesthesia and analgesia were standardized. Spirometry was assessed before operation and 24 h after surgery. Postoperative oxygenation and the apnoea-hypopnoea index (AHI) were recorded during the first postoperative night. Age, BMI, and STOP BANG score were similar in both groups. FRC decrease after surgery was minimal [0.15 (0.14) litre in control and 0.38 (0.19) litre in the RM group] and similar between the groups (P=0.35). FVC, FEV1, mean [Formula: see text], percentage of time spent with [Formula: see text] below 90%, and AHI did not differ significantly between the groups. This study demonstrates that when added to a protective mechanical ventilation combining low tidal volume and high PEEP, two RMs do not improve postoperative lung function including FRC, arterial oxygenation, and the incidence of obstructive apnoea in MO patients after laparoscopic upper abdominal surgery. EudraCT 2011-000999-33.
    BJA British Journal of Anaesthesia 05/2014; 113(3). DOI:10.1093/bja/aeu101 · 4.35 Impact Factor