Biomedical subjects

T C Amis

Publications and source records attributed to T C Amis.

At least 19 recordsLinked to original sources

PubMed2004

Older individuals have increased oro-nasal breathing during sleep.

Breathing route during sleep has been studied very little, however, it has potential importance in the pathophysiology of sleep disordered breathing. Using overnight polysomnography, with separate nasal and oral thermocouple probes, data were obtained from 41 subjects (snorers and nonsnorers; 25 male and 16 female; aged 20-66 yrs). Awake, upright, inspiratory nasal resistance (Rn) was measured using posterior rhinomanometry. Each 30-s sleep epoch (not affected by apnoeas/hypopnoeas) was scored for presence of nasal and/or oral breathing. Overnight, seven subjects breathed nasally, one subject oro-nasally and the remainder switched between nasal and oro-nasal breathing. Oral-only breathing rarely occurred. Nasal breathing epochs were 55.79 (69.78) per cent of total sleep epochs (%TSE; median (interquartile range)), a value not significantly different to that for oro-nasal (TSE: 44.21 (68.66)%). Oro-nasal breathing was not related to snoring, sleep stage, posture, body mass index, height, weight, Rn (2.19 (1.77) cm H2O x L(-1) x sec(-1)) or sex, but was positively associated with age. Subjects > or = 40 yrs were approximately six times more likely than younger subjects to spend >50% of sleep epochs utilising oro-nasal breathing. Ageing is associated with an increasing occurrence of oro-nasal breathing during sleep.

Adult↗

PubMed2000

Nasal airflow dynamics: mechanisms and responses associated with an external nasal dilator strip.

The adhesive external nasal dilator strip (ENDS) is widely advocated for prevention of snoring and promotion of nasal breathing during exercise. In the present study, the effects of the ENDS on nasal airflow resistance (Rn) in normal subjects were examined and factors determining individual responses to the ENDS explored. Using posterior rhinomanometry, 20 healthy Caucasian adults (10 males, 10 females; age: 18-56 yrs) were studied during quiet tidal breathing and voluntary hyperpnoea with (ENDS) and without (control) ENDS and with a placebo strip (placebo) before and after application of a topical nasal decongestant (oxymetazoline hydrochloride). During tidal breathing, only nine subjects showed a significantly (p<0.05) decreased inspiratory and/or expiratory Rn with the ENDS ("responders"). During the control, inspiratory Rn (at 0.4 L x s(-1)) was higher in "responders" than "nonresponders" (3.28+/-0.16 versus 2.60+/-0.08 cmH2O x L(-1) x s; p=0.04). The effects of nasal decongestant and the ENDS were additive. During voluntary hyperpnoea, inspiratory Rn (at 1.0 L x s(-1)) and the hysteresis of the inspiratory transnasal pressure/flow curve were decreased with the ENDS in most subjects. It is concluded that the external nasal dilator strip influences nasal airflow dynamics by both dilation of the nasal valve and stabilization of the lateral nasal vestibule walls and may be more effective in subjects with a high resting nasal airflow resistance.

Adolescent↗

PubMed2000

Nasal resistance and flow resistive work of nasal breathing during exercise: effects of a nasal dilator strip.

Using posterior rhinomanometry, we measured nasal airflow resistance (Rn) and flow-resistive work of nasal breathing (WONB), with an external nasal dilator strip (ENDS) and without (control), in 15 healthy adults (6 men, 9 women) during exclusive nasal breathing and graded (50-230 W) exercise on a cycle ergometer. ENDS decreased resting inspiratory and/or expiratory Rn (at 0.4 l/s) by >0.5 cmH(2)O. l(-1). s in 11 subjects ("responders"). Inspired ventilation (VI) increased with external work rate, but tended to be greater with ENDS. Inspiratory and expiratory Rn (at 0.4 l/s) decreased as VI increased but, in responders, tended to remain lower with ENDS. Inspiratory (but not expiratory) Rn at peak nasal airflow (Vn) increased as VI increased but, again, was lower with ENDS. At a VI of approximately 35 l/min, ENDS decreased flow limitation and hysteresis of the inspiratory transnasal pressure-flow curve. In responders, ENDS reduced inspiratory WONB per breath and inspiratory nasal power values during exercise. We conclude that ENDS stiffens the lateral nasal vestibule walls and, in responders, may reduce the energy required for nasal ventilation during exercise.

Adult↗

PubMed1999

Oral airway flow dynamics in healthy humans.

1. Oral airway resistance (RO) is an important determinant of oro-nasal partitioning of airflow (e.g. during exercise and sleep); however, little is known of factors influencing its magnitude and measurement. 2. We developed a non-invasive standardized technique for measuring RO (based on a modification of posterior rhinomanometry) and examined inspiratory RO in 17 healthy male subjects (age, 36 +/- 2 years (mean +/- s.e.m.); height, 177 +/- 2 cm; weight, 83 +/- 3 kg). 3. Inspiratory RO (at 0.4 l s-1) was 0.86 +/- 0.23 cmH2O l-1 s-1 during resting mouthpiece breathing in the upright posture. RO was unaffected by assumption of the supine posture, tended to decrease with head and neck extension and increased to 1.22 +/- 0.19 cmH2O l-1 s-1 (n = 10 subjects, P < 0.01) with 40-45 deg of head and neck flexion. When breathing via a mouth-mask RO was 2.98 +/- 0.42 cmH2O l-1 s-1 (n = 7) and not significantly different from nasal airway resistance. 4. Thus, in awake healthy male subjects with constant jaw position, RO is unaffected by body posture but increases with modest degrees of head and neck flexion. This influence on upper airway patency may be important when oral route breathing is associated with alterations in head and neck position, e.g. during sleep.

Adult↗

PubMed1999

Nasal dilator strips increase maximum inspiratory flow via nasal wall stabilization.

OBJECTIVE: Inspiratory flow limitation associated with collapse of the nasal vestibular walls is a feature of nasal breathing at high ventilatory levels. We examined whether an external nasal dilator strip (ENDS) device (Breathe Right, CNS Inc., Chanhassen, MN) influences maximum inspiratory and expiratory flow rates. STUDY DESIGN: Prospective, randomized. METHODS: We studied 20 Caucasian subjects (13 female, 7 male; age range, 16-49 y) performing maximum-effort nasal flow-volume loop studies with (ENDS) and without ENDS (control) and following topical nasal decongestant (oxymetazoline hydrochloride, 0.2 mg per nostril). RESULTS: ENDS increased peak inspiratory flow from 2.55+/-0.24 L/s (mean+/-standard error [SE]) to 2.86+/-0.25 L/s and forced inspiratory flow at 50% of vital capacity from 2.23+/-0.24 L/s to 2.53+/-0.24 L/s (both, P<.0001), but had no effect on maximum expiratory flows. Nasal decongestant increased the forced expiratory volume in 1 second from 3.39+/-0.22 L/s to 3.59+/-0.22 L/s and the average forced expiratory flow over 25% to 75% of vital capacity from 3.31+/-0.31 L/s to 3.61+/-0.28 L/s (both, P< or = .008), but had no effect on maximum inspiratory flows. The combination of decongestant and ENDS increased both inspiratory and expiratory maximum flows. CONCLUSION: Since ENDS selectively increases maximum nasal inspiratory flow rates, we conclude that ENDS increases inspiratory nasal patency during maximum inspiratory efforts through the nose by supporting the lateral nasal vestibular walls and making them more resistant to collapse.

Adolescent↗

PubMed1999

Oral airway resistance during wakefulness in patients with obstructive sleep apnoea.

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.

Airway Resistance↗

PubMed1999

Nasal dilator strips delay the onset of oral route breathing during exercise.

The external nasal dilator strip (ENDS) device (Breathe Right, CNS Inc., Chanhassen, MN, USA) has been adopted by athletes to promote nasal route breathing during exercise. We studied the influence of ENDS on the switching point from nasal-only to oro-nasal breathing during exercise in 4 healthy men (age 25 +/- 2 yrs, mean +/- SEM) and 5 women (age 30 +/- 5 yrs). Resting inspiratory nasal airflow resistance decreased from 0.33 +/- 0.02 kPa/L/s without ENDS to 0.22 +/- 0.01 kPa/L/s with ENDS (p < 0.01). ENDS delayed the onset of oro-nasal breathing such that the time from commencement of exercise to switching increased by 15.2%, and maximum levels of inspiratory nasal airflow and ventilation achieved prior to switching increased by 14.9% and 14.3%, respectively (all p < 0.05). We conclude that, in normal healthy subjects, ENDS does promote nasal route breathing during exercise, but any delay in the onset of oral route breathing during a progressive exercise task appears relatively small.

Adult↗

PubMed1999

Soft palate muscle responses to negative upper airway pressure.

The afferent pathways and upper airway receptor locations involved in negative upper airway pressure (NUAP) augmentation of soft palate muscle activity have not been defined. We studied the electromyographic (EMG) response to NUAP for the palatinus, tensor veli palatini, and levator veli palatini muscles in 11 adult, supine, tracheostomized, anesthetized dogs. NUAP was applied to the nasal or laryngeal end of the isolated upper airway in six dogs and to four to six serial upper airway sites from the nasal cavity to the subglottis in five dogs. When NUAP was applied at the larynx, peak inspiratory EMG activity for the palatinus and tensor increased significantly (P < 0.05) and plateaued at a NUAP of -10 cmH2O. Laryngeal NUAP failed to increase levator activity consistently. Nasal NUAP did not increase EMG activity for any muscle. Consistent NUAP reflex recruitment of soft palate muscle activity only occurred when the larynx was exposed to the stimulus and, furthermore, was abolished by bilateral section of the internal branches of the superior laryngeal nerves. We conclude that soft palate muscle activity may be selectively modulated by afferent activity originating in the laryngeal and hypopharyngeal airway.

Animals↗

PubMed1999

Nasal vestibule wall elasticity: interactions with a nasal dilator strip.

We studied the effect of an adhesive external nasal dilator strip (ENDS) on external nasal geometry in 20 healthy Caucasian adults (10 men, 10 women; age 21-45 yr). The recoil force exerted by ENDS was estimated by bending the device (n = 10) with known weights. In the horizontal direction, a small/medium-sized ENDS in situ exerted a unilateral recoil force of 21.4-22.6 g. Application of ENDS resulted in a displacement of the lateral nasal vestibule walls that had both anterosuperior and horizontal components and that was maintained over an 8-h period. The resultant unilateral nasal vestibule wall displacement at the tip of the device was at 47.6 +/- 2.0 degrees to the horizontal (as related to the plane of the device when in situ) and had a magnitude of 3.5 +/- 0.1 mm. ENDS increased external nasal cross-sectional area by 23.0-65.3 mm2. Nasal vestibule wall compliance was estimated at 0.05-0.16 mm/g. Thus ENDS applies a relatively constant abducting force irrespective of nasal width. Variable responsiveness to ENDS may be related to differences in elastic properties of the nasal vestibule wall.

Adult↗

PubMed1999

Route of breathing in patients with asthma.

STUDY OBJECTIVES: To measure route of breathing in chronic asthmatic patients during and after an acute severe exacerbation. PATIENTS OR PARTICIPANTS: Thirteen asthmatic patients were studied during hospital admission for acute asthma and, in 9 patients, again when asymptomatic. Nine healthy subjects were also studied. INTERVENTIONS: Spontaneous route of breathing was qualitatively assessed using oral and nasal thermistor probes, and was then quantified using a dual compartment face mask with attached pneumotachographs. MEASUREMENTS AND RESULTS: All asthmatic patients had severe bronchoconstriction initially (FEV(1), 46 +/- 3% of predicted) that had resolved at follow-up (FEV(1), 91 +/- 6% of predicted). No healthy subject had evidence of bronchoconstriction (FEV(1), 102 +/- 5% of predicted). During acute asthma, 11 asthmatics were spontaneously breathing oronasally, as assessed using thermistor probes, while all 13 breathed oronasally via face mask. When assessed using thermistor probes, seven of nine asymptomatic asthmatic patients studied were breathing exclusively via the nose; however, all breathed oronasally via face mask. In contrast, while eight of nine healthy subjects were also breathing exclusively via the nose when assessed using thermistor probes, all breathed nasally only via face mask. CONCLUSIONS: Thus, when asymptomatic and at rest, asthmatic patients breathe exclusively via the nose. However, during acute exacerbations of asthma, these patients switch to oronasal breathing. Unlike healthy subjects, chronic asthmatic patients also switch to oronasal breathing when wearing a face mask, irrespective of the degree of bronchoconstriction. We speculate that asthmatics may have an increased tendency to switch to oral breathing, a factor that may contribute to the pathogenesis of their asthma.

Adult↗

PubMed1998

Epiglottic movements during breathing in humans.

1. Using X-ray fluoroscopy we measured antero-posterior (A-P) and cranio-caudal (C-C) displacements of the epiglottic tip (ET), corniculate cartilage and hyoid bone in seven seated, normal human subjects (age 34 +/- 3 years; mean +/- S.E.M.; 4 males, 3 females) breathing via a nasal mask or mouthpiece with (RL) and without (UB) a fixed resistive load. 2. During UB, via either mouth or nose, there were no significant A-P ET movements. During RL via the nose the ET at peak expiratory flow was 2.6 +/- 1.3 mm cranial to its position at peak inspiratory flow (P < 0.05, ANOVA). C-C movements of the ET correlated strongly with C-C movements of the corniculate cartilage and hyoid bone. 3. The ET, corniculate cartilage and hyoid bone (at zero airflow) were situated more caudally during oral UB than for any other condition. 4. When present, epiglottic movements during breathing do not appear to be independent of those of the larynx and hyoid. Furthermore, epiglottic position may be related to the level of upper airway resistance.

Adult↗

PubMed1998

Mechanical properties of the upper airway.

Abnormalities of upper airway mechanical properties are a well-recognized and important feature of the pathophysiology of the obstructive sleep apnea hypopnea syndrome (OSAHS). Recently, investigations enhanced our understanding of the factors that promote upper airway obstruction. In patients with OSAHS, anatomic narrowing of the pharyngeal airway, particularly in the lateral dimension with thickening of the lateral pharyngeal walls, is present. In addition, the passive upper airway (absent muscle activity) demonstrates increased collapsibility, which is modulated by caudal tracheal traction, mucosal surface forces, route of breathing, and the balance of intraluminal airway and extraluminal tissue pressures. In patients with OSAHS, pharyngeal dilator muscles (including the genioglossus and soft palate muscles) demonstrate a coordinated pattern of increased muscle activity while awake compared with normals. This is thought to represent a neuromuscular compensatory mechanism for the anatomically narrow, more collapsible upper airway. With the onset of sleep, the reflexes that drive this muscular compensation are diminished, leading to reduced muscle activity and predisposing the OSAHS patient to pharyngeal collapse. Better understanding of the mechanical properties of the upper airway in normals and patients with OSAHS should help in the development of new therapeutic strategies.

Airway Obstruction↗

PubMed1996

Electromyographic activity of the hyoepiglotticus muscle in dogs.

We examined the respiratory-related electromyographic (EMG) activity of the hyoepiglotticus muscle using fine wire bipolar electrodes, inserted perorally in five anaesthetised (IV chloralose) tracheostomised dogs studied in the prone, mouth open position. The integrated HE EMG was measured in arbitrary units (a.u.) during resting breathing via the upper airway, and on a breath-by-breath basis during progressive increases in respiratory drive induced by infusion of CO2 into the inspired gas. The HE demonstrated inspiratory activity which increased linearly in relation to ventilation (r = 0.85 +/- 0.06, p < 0.001) due to an increase in both phasic (8.8 +/- 1.8 to 32.4 +/- 9.2 a.u.) and tonic (0.2 +/- 0.1 to 26.3 +/- 13.3 a.u.) activity (both p < 0.05). In addition, HE EMG developed substantial phasic expiratory activity (1.3 +/- 1.1 to 13.8 +/- 4.4 a.u., p < 0.05). We conclude that the canine HE exhibits inspiratory and expiratory related activity which is augmented during increased respiratory drive. These findings imply active control of epiglottic position during breathing in dogs.

Animals↗

PubMed1996

Mechanisms of oronasal airflow partitioning in dogs.

We examined the integrated (MTA) electromyographic activity (EMG) of the hyoepiglotticus (HE) muscle and the soft palate muscles (SPM) during CO2 administration in 6 anaesthetised prone, mouth open dogs. As ventilation increased nasal flow (VN) as a percentage of total flow (VT), i.e. VN/VT%, decreased. Breath-by-breath peak inspiratory and peak expiratory HE EMG activity was strongly and inversely correlated with VN/VT% (both r > 0.8, p < 0.001), whereas the correlation between SPM MTA EMG activity and VN/VT% was highly variable. Severing of the HE muscles halved the rate at which VN/VT% was reduced with respect to increasing ventilation while electrical stimulation of HE muscle contraction resulted in a fall in VN/VT% to near zero levels. Active control of epiglottic position appears to be an important mechanism controlling the patency of the epiglottic-soft palate seal and thus the oronasal partitioning of airflow in dogs.

Anesthesia, General↗

PubMed1996

Influence of hyoepiglotticus muscle contraction on canine upper airway geometry.

We examined the effect of hyoepiglotticus (HE) muscle contraction on epiglottic position in 4 anaesthetised (IV choralose, pentobarbitone sodium) tracheostomised, mechanically ventilated dogs studied in the prone mouth open position. Computerised axial tomography (coronal plane) was used to measure the vertical distance between the tip of the epiglottis (E) and (1) the soft palate (SP) (i.e. E-SP distance) and (2) the dorsal wall of the nasopharynx (N) (i.e. E-N distance). Duplicate runs of graded electrical stimulation of the HE muscle, using bilateral bipolar fine wire electrodes, were performed in each animal and resulted in a progressive increase in both the E-SP distance (baseline of 0.5 +/- 0.5 to a maximum of 13.1 +/- 2.3 mm, mean +/- SE) and the E-N distance (29.1 +/- 2.0 to a maximum of 42.2 +/- 2.7 mm, both p < 0.02). We conclude that HE contraction moves the epiglottis ventrally away from the soft palate thus opening and enlarging the oral pathway for airflow.

Animals↗

PubMed1996

Control of epiglottic position in dogs: role of negative upper airway pressure.

We investigated the influence of negative upper airway pressure (NUAP) on hyoepiglotticus and genioglossus muscle electromyographic (EMG) activity in anaesthetised (sodium pentobarbitone/ chloralose) dogs breathing via a tracheostomy. Changes in pressure were not transmitted through the entire upper airway, thus confirming airway occlusion during NUAP. When NUAP was applied at the larynx, peak inspiratory and tonic EMG activity of the genioglossus and HE both increased significantly (p < 0.05) and reached a plateau at NUAP of -10 to -20 cmH2O. Nasal NUAP at any level failed to influence either genioglossus or HE EMG activity. Following bilateral section of the internal branches of the superior laryngeal nerves (SLNin), resting levels of HE and genioglossus EMG activity decreased to virtually zero. Moreover, NUAP applied at the larynx now failed to recruit EMG activity for either muscle. These findings suggest active control of epiglottic position in dogs during NUAP.

Airway Obstruction↗

PubMed1996

Influence of upper airway pressure oscillations on soft palate muscle electromyographic activity.

Snoring is characterized by high-frequency (30-50 Hz) pressure oscillations (HFPO) in the upper airway (UA). The soft palate is a major oscillating structure during snoring, and soft palate muscle (SPM) activity is an important determinant of velopharyngeal patency. Consequently, we examined the effect of artificial HFPO applied to the UA on the integrated electromyographic (EMG) activity of the SPMs in 11 supine mouth-closed anesthetized (pentobarbital sodium/chloralose) dogs breathing spontaneously via a tracheostomy. The EMGs of the palatinus (Pal; n = 11), levator veli palatini (LP; n = 9), and tensor veli palatini (TP; n = 8) were monitored with intramuscular fine-wire electrodes. Peak inspiratory and peak expiratory EMG activity was measured in arbitrary units (au) as the mean of five consecutive breaths. HFPO [+/- 4.5 +/- 0.4 (SE) cmH2O; 30 Hz] applied at the laryngeal end of the isolated UA increased peak inspiratory EMG from 3.3 +/- 2.0 to 8.4 +/- 1.7 au (P < 0.05) for Pal and from 2.0 +/- 1.1 to 7.3 +/- 2.7 au (P < 0.05) for LP. For the TP, increases were evident in four dogs, but mean values for the group did not change (5.8 +/- 2.4 to 11.0 +/- 4.1 au, P = 0.5). The peak expiratory EMG did not change for any SPM (all P > 0.3). Thus HFPO applied to the UA augments inspiratory SPM activity. Reflex augmentation of SPM activity by HFPO may serve to dilate the retropalatal airway and/or stiffen the soft palate during inspiration in an attempt to stabilize UA geometry during snoring.

Animals↗

PubMed1996

Supraglottic airway pressure-flow relationships during oronasal airflow partitioning in dogs.

We studied pressure-flow relationships in the supraglottic airway of eight prone mouth-open anesthetized (intravenous chloralose or pentobarbital sodium) crossbred dogs (weight 15-26 kg) during increasing respiratory drive (CO2 administration; n = 4) and during graded-voltage electrical stimulation (SV; n = 4) of the soft palate muscles. During increased respiratory drive, inspiratory airflow occurred via both the nose (Vn) and mouth (Vm), with the ratio of Vn to Vm [%(Vn/Vm)] decreasing maximally from 16.0 +/- 7.0 (SD) to 2.4 +/- 1.6% (P < 0.05). Simultaneously, oral airway resistance at peak inspiratory flow decreased from 2.1 +/- 1.0 to 0.4 +/- 0.4 cmH2O (P < 0.05), whereas nasal airway resistance did not change (14.4 +/- 7.2 to 13.1 +/- 5.4 cmH2O; P = 0.29). Inspiratory pressure-flow plots of the oral airway were inversely curvilinear or more complex in nature. Nasal pathway plots, however, demonstrated a positive linear relationship in all animals (r = 0.87 +/- 0.11; all P < 0.001). During electrical stimulation of soft palate muscle contraction accompanied by graded constant-inspiratory airflows of 45-385 ml/s through an isolated upper airway, %(Vn/Vm) decreased from 69 +/- 50 to 10 +/- 13% at a SV of 84 +/- 3% of maximal SV (P < 0.001). At a SV of 85 +/- 1% of maximum, normalized oral airway resistance (expressed as percent baseline) fell to 5 +/- 3%, whereas normalized nasal resistance was 80 +/- 9% (both P < 0.03). Thus control of oronasal airflow partitioning in dogs appears mediated more by alterations in oral route geometry than by closure of the nasopharyngeal airway.

Air Pressure↗