Oral airway resistance during wakefulness in patients with obstructive sleep apnoea. (1/93)

BACKGROUND: Patients with obstructive sleep apnoea (OSA) have a number of upper airway structural abnormalities which may influence the resistance of the oral airway to airflow. There have been no systematic studies of the flow dynamics of the oral cavity in such patients. METHODS: Inspiratory oral airway resistance to airflow (RO) was measured in 13 awake patients with OSA in both the upright and supine positions (neck position constant). Each subject breathed via a mouthpiece while the nasal airway was occluded with a nasal mask. RESULTS: In the upright position the mean (SE) RO was 1.26 (0. 19) cm H2O/l/s (at 0.4 l/s) which increased to 2.01 (0.43) cm H2O/l/s when supine (p<0.05, paired t test). The magnitude of this change correlated negatively with the respiratory disturbance index (r = -0.60, p = 0.03). CONCLUSION: In awake patients with OSA RO is normal when upright but abnormally raised when in the supine position.  (+info)

Longitudinal distribution of chlorine absorption in human airways: comparison of nasal and oral quiet breathing. (2/93)

The fraction of an inspired chlorine (Cl2) bolus absorbed during a single breath (Lambda) was measured as a function of bolus penetration (VP) into the respiratory system of five male and five female nonsmokers during both nasal and oral breathing at a quiet respiratory flow of 250 ml/s. The correspondence between VP and specific anatomic landmarks was found for each subject by a combination of acoustic reflection and nitrogen washout measurements. For both nasal and oral breathing, Lambda reached approximately 0. 95 at the distal end of the upper airways and reached 1.00 within the lower conducting airways. The values of a regional mass transfer parameter computed from the Lambda-VP data indicated that the resistance to Cl2 diffusion in the airway mucosa was negligible compared with the diffusion resistance in the respired gas. Changing the peak inhaled Cl2 concentration from 0.5 to 3.0 parts/million did not significantly affect the distribution of Cl2 absorption, suggesting that the underlying mass transport and chemical reaction processes were linear with respect to Cl2 concentration.  (+info)

Effect of mouth leak on effectiveness of nasal bilevel ventilatory assistance and sleep architecture. (3/93)

Mouth leak is common during nasal ventilatory assistance, but its effects on ventilatory support and on sleep architecture are unknown. The acute effect of sealing the mouth on sleep architecture and transcutaneous carbon dioxide tension (Ptc,CO2) was tested in 9 patients (7 hypercapnic) on longterm nasal bilevel ventilation with symptomatic mouth leak. Patients slept with nasal bilevel ventilation at their usual settings on two nights in random order. On one night, the mouth was taped closed. Leak was measured with a pneumotachograph. Median leak fell from 0.35+/-0.07 (mean +/- SEM) L x s(-1) untaped to 0.06+/-0.03 L x s(-1) taped. Ptc,CO2 fell in 8/9, including all hypercapnic patients. Across all patients, the mean Ptc,CO2 fell by 1.02+/-0.28 kPa (7.7+/-2.1 mm Hg) with taping (p = 0.007). Arousal index fell in every patient. Mean arousal index fell from 35.0+/-3.0 to 13.9+/-1.2 h(-1) (p<0.0001), and rapid eye movement (REM) sleep increased from 12.9+/-1.5% to 21.1+/-1.8% sleep time (p = 0.0016). Slow wave sleep changed inconsistently, from a mean of 13.1+/-1.6% to 19.5+/-2.2% of sleep (p = 0.09). Sleep latency and efficiency were unchanged. In four healthy volunteers ventilator-induced awake hypopharyngeal pressure swing during timed bilevel ventilation fell by 35+/-5% L(-1) x s(-1) of voluntary mouth leak (p<0.0001). Mouth leak reduces effective nasal bilevel ventilatory support, increases transcutaneous carbon dioxide tension, and disrupts sleep architecture.  (+info)

Influence of posture and breathing route on neural drive to upper airway dilator muscles during exercise. (4/93)

Our purpose was to determine the influence of posture and breathing route on electromyographic (EMG) activities of nasal dilator (NDM) and genioglossus (GG) muscles during exercise. Nasal and oral airflow rates and EMG activities of the NDM and GG were recorded in 10 subjects at rest and during upright and supine incremental cycling exercise to exhaustion. EMG activities immediately before and after the switch from nasal to oronasal breathing were also determined for those subjects who demonstrated a clear switch point (n = 7). NDM and GG EMG activities were significantly correlated with increases in nasal, oral, and total ventilatory rates during exercise, and these relationships were not altered by posture. In both upright and supine exercise, NDM activity rose more sharply as a function of nasal inspired ventilation compared with total or oral inspired ventilation (P < 0.01), but GG activity showed no significant breathing-route dependence. Peak NDM integrated EMG activity decreased (P = 0.008), and peak GG integrated EMG activity increased (P = 0.032) coincident with the switch from nasal to oronasal breathing. In conclusion, 1) neural drive to NDM and GG increases as a function of exercise intensity, but the increase is unaltered by posture; 2) NDM activity is breathing-route dependent in steady-state exercise, but GG activity is not; and 3) drive to both muscles changes significantly at the switch point, but the change in GG activity is more variable and is often transient. This suggests that factors other than the breathing route dominate drive to the GG soon after the initial changes in the configuration of the oronasal airway are made.  (+info)

Effects of intermaxillary fixation during orthognathic surgery on respiratory function after general anesthesia. (5/93)

I examined the relationship between preoperative breathing route (nasal and/or oral) and respiratory status in 29 patients who underwent orthognathic surgery and intermaxillary fixation (IMF) with general anesthesia and in 14 healthy, adult control volunteers who received IMF without surgery or anesthesia. The tidal volume (VT), minute respiratory volume (MV), respiratory rate, and end-tidal carbon dioxide concentration were measured for both nasal and oral breathing before and after IMF. Pulse oximetry recordings were also taken. There was no significant effect of IMF on any parameter in the volunteers. Fifteen patients engaged in nasal breathing only both before and after surgery with IMF (group pN), and 7 patients had combined nasal and oral breathing before but only nasal breathing after IMF (group pNO). VT and MV decreased (536-357 mL and 7.84-5.40 L, respectively) in group pNO after IMF. These results suggest that assessment of the preoperative breathing status is helpful in predicting postoperative respiratory function after IMF and indicate that patients with preoperative mouth breathing require greater respiratory care after general anesthesia with IMF.  (+info)

Cleft lip and palate: a review for dentists. (6/93)

The goals of primary closure of cleft lip and palate include not only re-establishing normal insertions for all of the nasolabial muscles but also restoring the normal position of all the other soft tissues, including the mucocutaneous elements. Conventional surgical wisdom, which recommends waiting until growth is complete before undertaking surgical correction of the postoperative sequelae of primary cheiloplasty, carries with it many disadvantages. If, after primary surgery of the lip, orolabial dysfunctions remain, they will exert their nefarious influences during growth and will themselves lead to long term dentofacial imbalances. These imbalances can significantly influence facial harmony. Unless accurate, symmetric and functional reconstruction of the nasolabial muscles is achieved during the primary surgery, not only will the existing dentoskeletal imbalances be exaggerated, but other deformities will be caused during subsequent growth, among which the most important are nasal obstruction and mouth breathing, reduced translation of the maxilla, dysymmetry of the nose and inability of the patient to symmetrically project the upper lip  (+info)

Lip seal study of Japanese adults with malocclusion. (7/93)

The purpose of this study to clarify the factors an effecting lip seal in Japanese adults with malocclusion. Sixty-three malocclusion patients aged 20 to 27 years were randomly selected and compared with fourteen normal occlusion controls aged 22 to 26 years old. The subjects were divided into a good seal group and a poor lip seal group by observing the distance between the upper and lower lip at rest. Results of this adult study were as follows; There were no poor lip seals in normal occlusion subjects. Significant differences were observed for tongue thrust (p < 0.05) and mouth breathing (p < 0.05) between the good lip seal group and poor lip seal group of malocclusion subjects. Adults with poor lip seal should be treated for their malocclusion prior to be other functional approaches to improving their lip seal.  (+info)

Partitioning of inhaled ventilation between the nasal and oral routes during sleep in normal subjects. (8/93)

The oral and nasal contributions to inhaled ventilation were simultaneously quantified during sleep in 10 healthy subjects (5 men, 5 women) aged 43 +/- 5 yr, with normal nasal resistance (mean 2.0 +/- 0.3 cmH(2)O. l(-1). s(-1)) by use of a divided oral and nasal mask. Minute ventilation awake (5.9 +/- 0.3 l/min) was higher than that during sleep (5.2 +/- 0.3 l/min; P < 0.0001), but there was no significant difference in minute ventilation between different sleep stages (P = 0.44): stage 2 5.3 +/- 0.3, slow-wave 5.2 +/- 0.2, and rapid-eye-movement sleep 5.2 +/- 0.2 l/min. The oral fraction of inhaled ventilation during wakefulness (7.6 +/- 4%) was not significantly different from that during sleep (4.3 +/- 2%; mean difference 3.3%, 95% confidence interval -2.1-8.8%, P = 0.19), and no significant difference (P = 0.14) in oral fraction was observed between different sleep stages: stage two 5.1 +/- 2.8, slow-wave 4.2 +/- 1.8, rapid-eye-movement 3.1 +/- 1.7%. Thus the inhaled oral fraction in normal subjects is small and does not change significantly with sleep stage.  (+info)