Effect of increased inspiratory muscle work on blood flow to inactive and active limbs during submaximal dynamic exercise.

NEW FINDINGS: What is the central question of this study? Increased respiratory muscle activation is associated with neural and cardiovascular consequences via the respiratory muscle metaboreflex. Does increased sympathetic vasoconstriction originating from the respiratory musculature elicit a reduction in blood flow to an inactive limb in order to maintain blood flow to an active limb? What is the main finding and its importance? Arm blood flow was reduced whereas leg blood flow was preserved during mild leg exercise with inspiratory resistance. Blood flow to the active limb is maintained via sympathetic control of blood flow redistribution when the respiratory muscle-induced metaboreflex is activated. ABSTRACT: The purpose of this study was to elucidate the effect of increasing inspiratory muscle work on blood flow to inactive and active limbs. Healthy young men (n = 10, 20 ± 2 years of age) performed two bilateral dynamic knee-extension and knee-flexion exercise tests at 40% peak oxygen uptake for 10 min. The trials consisted of spontaneous breathing for 5 min followed by voluntary hyperventilation either with or without inspiratory resistance for 5 min (40% of maximal inspiratory mouth pressure, inspiratory duty cycle of 50% and a breathing frequency of 40 breaths min-1 ). Mean arterial blood pressure was acquired using finger photoplethysmography. Blood flow in the brachial artery (inactive limb) and in the femoral artery (active limb) were monitored using Doppler ultrasound. Mean arterial blood pressure during exercise was higher (P < 0.05) with inspiratory resistance (121 ± 7 mmHg) than without resistance (99 ± 5 mmHg). Brachial artery blood flow increased during exercise without inspiratory resistance (120 ± 31 ml min-1 ) compared with the resting level, whereas it was attenuated with inspiratory resistance (65 ± 43 ml min-1 ). Femoral artery blood flow increased at the onset of exercise and was maintained throughout exercise without inspiratory resistance (2576 ± 640 ml min-1 ) and was unchanged when inspiratory resistance was added (2634 ± 659 ml min-1 ; P > 0.05). These results suggest that sympathetic control of blood redistribution to active limbs is facilitated, in part, by the respiratory muscle-induced metaboreflex.

Functional training of the inspiratory muscles improves load carriage performance.

Inspiratory Muscle Training (IMT) whilst adopting body positions that mimic exercise (functional IMT; IMTF) improves running performance above traditional IMT methods in unloaded exercise. We investigated the effect of IMTF during load carriage tasks. Seventeen males completed 60 min walking at 6.5 km·h-1 followed by a 2.4 km load carriage time-trial (LCTT) whilst wearing a 25 kg backpack. Trials were completed at baseline; post 4 weeks IMT (consisting of 30 breaths twice daily at 50% of maximum inspiratory pressure) and again following either 4 weeks IMTF (comprising four inspiratory loaded core exercises) or maintenance IMT (IMTCON). Baseline LCTT was 15.93 ± 2.30 min and was reduced to 14.73 ± 2.40 min (mean reduction 1.19 ± 0.83 min, p < 0.01) after IMT. Following phase two, LCTT increased in IMTF only (13.59 ± 2.33 min, p < 0.05) and was unchanged in post-IMTCON. Performance was increased following IMTF, providing an additional ergogenic effect beyond IMT alone. Practitioner Summary: We confirmed the ergogenic benefit of Inspiratory Muscle Training (IMT) upon load carriage performance. Furthermore, we demonstrate that functional IMT methods provide a greater performance benefit during exercise with thoracic loads. Abbreviations: [Lac-]B: blood lactate; FEV1: forced expiratory volume in one second; FEV1/FVC: forced expiratory volume in one second/forced vital capacity ratio; FVC: forced vital capacity; HR: heart rate; IMT: inspiratory muscle training; IMTCON: inspiratory muscle training maintenance; IMTF: functional inspiratory muscle training; LC: load carriage; LCTT: load carriage time trial; Pdi: transdiaphragmatic pressure; PEF: peak expiratory flow; PEmax: maximum expiratory mouth pressure; PImax: maximum inspiratory mouth pressure; RPE: rating of perceived exertion; RPEbreating: rating of perceived exertion for the breathing; RPEleg: rating of perceived exertion for the legs; SEPT: sport-specific endurance plank test; V̇ O2: oxygen consumption; V̇ O2peak: peak oxygen consumption.

Sex differences in the cardiovascular consequences of the inspiratory muscle metaboreflex.

It is currently unknown whether sex differences exist in the cardiovascular consequences of the inspiratory muscle metaboreflex. We hypothesized that the activation of the inspiratory muscle metaboreflex will lead to less of an increase in mean arterial pressure (MAP) and limb vascular resistance (LVR) and less of a decrease in limb blood flow (Q̇L) in women compared with men. Twenty healthy men (n = 10, 23 ± 2 yr) and women (n = 10, 22 ± 3 yr) were recruited for this study. Subjects performed inspiratory resistive breathing tasks (IRBTs) at 2% or 65% of their maximal inspiratory mouth pressure (PIMAX). During the IRBTs, the breathing frequency was 20 breaths/min with a 50% duty cycle. At rest and during the IRBTs, MAP was measured via automated oscillometry, Q̇L was measured via Doppler ultrasound, and LVR was calculated. EMG was recorded on the leg to ensure no muscle contraction occurred. The 65% IRBT led to attenuated increases (P < 0.01) from baseline in women compared with men for MAP (W: 7.3 ± 2.0 mmHg; M: 11.1 ± 5.0 mmHg) and LVR (W: 17.7% ± 14.0%; M: 47.9 ± 21.0%), as well as less of a decrease (P < 0.01) in Q̇L (W: -7.5 ± 9.9%; M: -23.3 ± 10.2%). These sex differences in MAP, Q̇L, and LVR were still present in a subset of subjects matched for PIMAX The 2% IRBT resulted in no significant changes in MAP, Q̇L, or LVR across time or between men and women. These data indicate premenopausal women exhibit an attenuated inspiratory muscle metaboreflex compared with age-matched men.

An electromyographic evaluation of dual role breathing and upper body muscles in response to front crawl swimming.

The upper body trunk musculature is key in supporting breathing, propulsion, and stabilization during front crawl swimming. The aim of this study was to determine if the latissimus dorsi, pectoralis major, and serratus anterior contributed to the development of inspiratory muscle fatigue observed following front crawl swimming. Fourteen trained swimmers completed a 200-m front crawl swim at 90% of race pace. Maximal inspiratory and expiratory mouth pressures (PImax and PEmax) were assessed before (baseline) and after each swim, and electromyography was recorded from the three muscles. Post-swim PImax fell by 11% (P < 0.001, d = 0.57) and the median frequency (MDF: a measure of fatigue) of the latissimus dorsi, pectoralis major, and serratus anterior fell to 90% (P = 0.001, d = 1.57), 87% (P = 0.001, r = -0.60) and 89% (P = 0.018, d = 1.04) of baseline, respectively. The fall in serratus anterior MDF was correlated with breathing frequency (r = 0.675, P = 0.008) and stroke rate (r = 0.639, P = 0.014). The results suggest that the occurrence of inspiratory muscle fatigue was partly caused by fatigue of these muscles, and that breathing frequency and stroke rate particularly affect the serratus anterior.

Change in the Upper Airway of Patients With Obstructive Sleep Apnea Syndrome Using Computational Fluid Dynamics Analysis: Conventional Maxillomandibular Advancement Versus Modified Maxillomandibular Advancement With Anterior Segmental Setback Osteotomy.

OBJECTIVE: The aim of the study was to compare the effect of conventional maxillomandibular advancement (MMA) and modified MMA with anterior segmental setback osteotomy (MMA-ASSO) on the airway changes in patients with obstructive sleep apnea syndrome (OSAS) using three-dimensional computational fluid dynamics (3D-CFD) analysis. METHODS: Two adult male patients with Class I malocclusion, lip protrusion, acute nasolabial angle, and OSAS were treated with conventional MMA (Case 1) and modified MMA-ASSO (Case 2). Individualized 3D airway models were fabricated using computed tomography data obtained 1 month before (T0) and at least 6 months after surgery (T1). A total of 7 cross-sectional areas of the airway were established, starting just above the hard palate (plane 1) with interval of 1 mm caudally. Airflow velocity and negative pressure were investigated using CFD analysis, and polysomnography studies were performed at T0 and T1. RESULTS: There were improvement of apnea-hypoapnea index and the lowest O2 level (T0 versus T1; 43.2 versus 15.2, 79% versus 90% in Case 1; 61.0 versus 6, 89% versus 92% in Case 2). At plane 2 (retropalatal area) in Cases 1 and 2, there were increase in the smallest cross-sectional areas (57.9% versus 28.4%), decrease in the airflow velocity and increase in the negative pressure at the peak of expiration (49.5% versus 31.7%; 88.4% versus 54.3%), end after expiration (53.2% versus 32.2%; 83.2% versus 47.9%), and peak of inspiration (53.1% versus 29.2%; 75.3% versus 48.2%). CONCLUSION: Modified MMA-ASSO method might be an effective treatment option for OSAS patients with improvement of airway problems and esthetic facial profile.

Measurement of oxygen concentration delivered via nasal cannulae by tracheal sampling.

BACKGROUND AND OBJECTIVE: Oxygen is used in many clinical scenarios, however the variable performance of nasal cannulae makes determining the precise fraction of inspired oxygen (FiO2 ) difficult. We developed a novel method for measurement of the tracheal FiO2 using a catheter placed via bronchoscopy. We investigate the effects of oxygen delivery, respiratory rate, mouth position and estimated minute ventilation (VE ) on the FiO2 delivered by nasal cannulae. METHODS: The catheter was placed in 20 subjects. Tracheal gas concentrations were analysed during six 5-min treatments controlling for oxygen delivery rate, respiratory rate and mouth position. Ventilation was monitored with respiratory inductive plethysmography (RIP). The FiO2 delivered by nasal cannulae was compared between treatments, and we investigated the relationships among the FiO2 , alveolar partial pressure of oxygen (PA O2 ) and VE . RESULTS: The FiO2 increased by 0.038/L/min of oxygen. Respiratory rate had a significant effect on the FiO2 . A normal respiratory rate of 15 breaths/min and oxygen supplementation via nasal cannula at 2 L/min resulted in an FiO2 of 0.296; however, FiO2 decreased by 0.012 at 20 breaths/min and 0.004 at 10 breaths/min. The mean FiO2 decreased by 0.024 with the mouth open. The FiO2 and PA O2 were observed to decrease with increasing VE . CONCLUSIONS: Continuous measurement of the FiO2 using a transtracheal catheter provides detailed insight into inspiratory changes of the FiO2 delivered by nasal cannulae. Our study confirms that respiratory rate, VE and mouth position significantly influence the inspired oxygen concentration. These parameters should be accounted for when prescribing oxygen.

Reliability and acceptability of measuring sniff nasal inspiratory pressure (SNIP) and peak inspiratory flow (PIF) to assess respiratory muscle strength in older adults: a preliminary study.

BACKGROUND: Sniff nasal inspiratory pressure (SNIP) and peak oral inspiratory flow (PIF) are portable, relatively new methods for indirect measurement of respiratory muscle strength. The reliability and acceptability of these measures were investigated in older adults. METHODS: The study included 21 self-reported healthy adults, aged 65-84 years (mean 73.5; SD 6.4 years). Participants were tested in a sitting position on two occasions, 1 week apart. The best of three attempts for PIF measured through the mouth, and five for each nostril for SNIP were recorded. Reliability was tested using intra-class correlation coefficient (ICC), standard error of measurement, minimal detectable change (MDC) and Bland and Altman analysis. Feedback on the measures in relation to ease of completion and preference was obtained using a semi-structured interview. RESULTS: Between-day reliability of SNIP and PIF were ICC3,1 0.76 (95 % CI 0.49-0.9) and 0.92 (0.81-0.97), respectively. Standard error of measurement for SNIP (11.94 cmH2O) and MDC (33.10 cmH2O) were at the least 61 % higher than for PIF. The participants reported difficulties in performing SNIP, rating it as being less easy and uncomfortable to perform than PIF, with a higher rate of missing data for SNIP due to participants' dislike of the test. CONCLUSIONS: The wide range of SNIP readings, lower ICC value and negative user feedback are suggestive of a less robust and unacceptable clinical measure. PIF showed excellent reliability and acceptability and is therefore recommended for assessing inspiratory muscle strength in older people without known obstructive lung disease.

Inspiratory muscle fatigue affects latissimus dorsi but not pectoralis major activity during arms only front crawl sprinting.

The purpose of this study was to determine whether inspiratory muscle fatigue (IMF) affects the muscle activity of the latissimus dorsi and pectoralis major during maximal arms only front crawl swimming. Eight collegiate swimmers were recruited to perform 2 maximal 20-second arms only front crawl sprints in a swimming flume. Both sprints were performed on the same day, and IMF was induced 30 minutes after the first (control) sprint. Maximal inspiratory and expiratory mouth pressures (PImax and PEmax, respectively) were measured before and after each sprint. The median frequency (MDF) of the electromyographic signal burst was recorded from the latissimus dorsi and pectoralis major during each 20-second sprint along with stroke rate and breathing frequency. Median frequency was assessed in absolute units (Hz) and then referenced to the start of the control sprint for normalization. After IMF inducement, stroke rate increased from 56 ± 4 to 59 ± 5 cycles per minute, and latissimus dorsi MDF fell from 67 ± 11 Hz at the start of the sprint to 61 ± 9 Hz at the end. No change was observed in the MDF of the latissimus dorsi during the control sprint. Conversely, the MDF of the pectoralis major shifted to lower frequencies during both sprints but was unaffected by IMF. As the latter induced fatigue in the latissimus dorsi, which was not otherwise apparent during maximal arms only control sprinting, the presence of IMF affects the activity of the latissimus dorsi during front crawl sprinting.

Sonographic assessment of changes in diaphragmatic kinetics induced by inspiratory resistive loading.

BACKGROUND AND OBJECTIVE: Diaphragmatic breathing patterns under resistive loading remain poorly documented. To our knowledge, this is the first study assessing diaphragmatic motion under conditions of inspiratory resistive loading with the use of sonography. METHODS: We assessed diaphragmatic motion during inspiratory resistive loading in 40 healthy volunteers using M-mode sonography. In phase I of the study, sonography was performed during normal quiet breathing without respiratory loading. In phase II, sonography was performed after application of a nose clip and connection of the subjects to a pneumotachograph through a mouth piece. In phase III, the participants were assessed while subjected to inspiratory resistive loading of 50 cm H(2)O/L/s. RESULTS: Compared with baseline, the application of a mouth piece and nose clip induced a significant increase in diaphragmatic excursion (from 1.7 to 2.3 cm, P < 0.001) and a decrease in respiratory rate (from 13.4 to 12.2, P < 0.01). Inspiratory resistive loading induced a further decrease in respiratory rate (from 12.2 to 8.0, P < 0.01) and a decrease in diaphragmatic velocity contraction (from 1.2 to 0.8 cm/s, P < 0.01), and also an increase in tidal volume (from 795 to 904 mL, P < 0.01); diaphragmatic excursion, however, did not change significantly. CONCLUSIONS: Inspiratory resistive loading induced significant changes in diaphragmatic contraction pattern, which mainly consisted of decreased velocity of diaphragmatic displacement with no change in diaphragmatic excursion. Tidal volume, increased significantly; the increase in tidal volume, along with the unchanged diaphragmatic excursion, provides sonographic evidence of increased recruitment of extradiaphragmatic muscles under inspiratory resistive loading.

Effects of body positions on respiratory muscle activation during maximal inspiratory maneuvers.

We evaluated the maximal mouth inspiratory pressure and the EMG patterns of major respiratory and accessory muscles used in the generation of voluntary inspiratory maneuvers during different body positions. Ten healthy subjects (F/M-4/6), the mean age 22.000B10.6 years, participated in the study. The maximal inspiratory mouth pressure (MIP) during Müller's maneuver was measured from residual volume in the standing, sitting, right-sided (RSL) and left-sided lying (LSL), supine, and head-down-tilt (HDT) (3000B0; relatively horizon) positions. EMG of the diaphragmatic (D), parasternal (PS), sternocleidomastoid (SM), and genioglossus (GG) muscles were assessed in each body position. The baseline MIP was 105.3 00B1; 12.0 in men and 59.9 00B110.1 cmH(2)O in women in the standing position and did not appreciable differ in the other positions, except the HDT where it was lower by 23 and 27% in men and women, respectively (P003C0.05). During Müllers maneuver, diaphragmatic EMG activity also was similar in all the body positions, but it was significantly enhanced in the HDT. In contrast, PS EMG showed the highest level of activation in the standing position, taken as the control, reference level, and was lower in the HDT. Activation of SM during the maneuver was near the control in the sitting position, lower in the supine (79%), RSL (85%), LSL (80%), and HDT (72%) positions (P 003C0.05). GG EMG was significantly greater during maximal inspiratory effort in the supine and HDT positions (125and 130%, respectively), while it was lower in the sitting, LRS, and LLS positions (76, 57, and 43%) compared with standing (P 003C; 0.05). We conclude that the inspiratory pressure generated during Muller maneuver is a reflection of complex interactions between several muscle groups during changes in body positions.

Improvement of nasal airway ventilation after rapid maxillary expansion evaluated with computational fluid dynamics.

INTRODUCTION: Rapid maxillary expansion is known to improve nasal airway ventilation. However, it is difficult to precisely evaluate this improvement with conventional methods. The purpose of this longitudinal study was to use computational fluid dynamics to estimate the effect of rapid maxillary expansion. METHODS: Twenty-three subjects (9 boys, 14 girls; mean ages, 9.74 ± 1.29 years before rapid maxillary expansion and 10.87 ± 1.18 years after rapid maxillary expansion) who required rapid maxillary expansion as part of their orthodontic treatment had cone-beam computed tomography images taken before and after rapid maxillary expansion. The computed tomography data were used to reconstruct the 3-dimensional shape of the nasal cavity. Two measures of nasal airflow function (pressure and velocity) were simulated by using computational fluid dynamics. RESULTS: The pressure after rapid maxillary expansion (80.55 Pa) was significantly lower than before rapid maxillary expansion (147.70 Pa), and the velocity after rapid maxillary expansion (9.63 m/sec) was slower than before rapid maxillary expansion (13.46 m/sec). CONCLUSIONS: Improvement of nasal airway ventilation by rapid maxillary expansion was detected by computational fluid dynamics.

Prefrontal cortex activation during incremental inspiratory loading in healthy participants.

We aimed to investigate whether changes in prefrontal cortex (PFC) oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) associates with inspiratory muscle effort during inspiratory threshold loading (ITL) in healthy participants. Participants performed an incremental ITL. Breathing pattern, partial pressure of end-tidal CO2 (PETCO2), mouth pressure and O2Hb and HHb over the right dorsolateral PFC, sternocleidomastoid (SCM), and diaphragm/intercostals (Dia/IC) were monitored. Fourteen healthy participants (8 men; 29 ± 5 years) completed testing. Dyspnea was higher post- than pre-ITL (5 ± 1 vs. 0 ± 1, respectively; P<0.05). PFC O2Hb increased (P < 0.001) and HHb decreased (P = 0.001) at low loads but remained stable with increasing ITL intensities. PFC total hemoglobin increased at task failure compared to rest. SCM HHb increased throughout increasing intensities. SCM and Dia/IC total hemoglobin increased in the at task failure compared to rest. PETCO2 did not change (P = 0.528). PFC is activated early during the ITL but does not show central fatigue at task failure despite greater dyspnea and an imbalance of SCM oxygen demand and delivery.

Monitoring of breathing phases using a bioacoustic method in healthy awake subjects.

OBJECTIVE: To test the ability of a microphone recording system, located distal to the respiratory outflow tract, to track the timing of the inspiratory and expiratory phases of breathing in awake healthy subjects. METHODS: Fifteen subjects participated. Breath sounds were recorded using a microphone embedded in a face frame in a fixed location in relation to the nostrils and mouth, while simultaneously recording respiratory movements by respiratory inductance plethysmography (RIP). Subjects were studied while supine and were instructed to breathe normally for 2 min: through their noses only (nasal breathing), during the first min, and through their mouths only (oral breathing) during the second min. Five subjects (test group) were chosen randomly to extract features from their acoustic data. Ten breaths (5 nasal and 5 oral breaths) from each subject were studied. Inspiratory and expiratory segments of breath sounds were determined and extracted from the acoustic data by comparing it to the RIP trace. Subsequently, the frequency spectrum of each phase was then determined. Spectral variables derived from the 5 test subjects were applied prospectively to detect breathing phases in the remaining 10 subjects (validation group). RESULTS: Test group data showed that the mean of all inspiratory spectra peaked between 30 and 270 Hz, flattened between 300 and 1,100 Hz, and peaked again with a center frequency of 1,400 Hz. The expiratory spectra peaked between 30 and 180 Hz and its power dropped off exponentially after that. Accordingly, the bands ratio (BR) of frequency magnitudes between 500 and 2500 Hz to frequency magnitudes between 0 and 500 Hz was chosen as a feature to distinguish between breathing phases. BR for the mean inspiratory spectrum was 2.27 and for the mean expiratory spectrum was 0.15. The route of breathing did not affect the BR ratio within the same phase. When this BR was applied to 436 breathing phases in the validation group, 424 (97%) were correctly identified (Kappa = 0.96, P < 0.001) indicating strong agreement between the acoustic method and the RIP. CONCLUSION: Frequency spectra of breathing sounds recorded from a face-frame, reliably identified the inspiratory and expiratory phases of breathing. This technique may have various applications for respiratory monitoring and analysis.

Inspiratory muscle fatigue significantly affects breathing frequency, stroke rate, and stroke length during 200-m front-crawl swimming.

The aim of the current study was to assess the impact of inspiratory muscle fatigue (IMF) on total breaths taken (f(tot)), breaths per minute (f(b)), stroke count (SC), stroke rate (SR), and stroke length (SL) during constant velocity front-crawl swimming. Eight collegiate swimmers undertook a 200-m front-crawl swim on 2 separate occasions. On 1 occasion, IMF was induced immediately before the swim (IMF trial), and on the other occasion, the swim was undertaken in the absence of IMF (control trial). Trials were administered using a randomized crossover design and at a swimming velocity equivalent to 85% of race pace: Pilot testing identified this as being the fastest pace, which did not induce IMF. Maximal inspiratory mouth pressure, which was measured at the mouth and from residual volume, fell by 17% (p < 0.05) in response to IMF but was unchanged in response to the swim itself (p < 0.05). When compared to the control trial, f(tot), f(b), SC, and SR increased (p < 0.05) and SL decreased (p < 0.05) in response to IMF. These data suggest that the increase in f(tot) and f(b) in the presence of IMF occurred, in part, in an attempt to alleviate dyspnea. As a result, SL decreased and SR and SC increased, although variability in the SR and SC response did occur. However, as a number of identical muscles are recruited during deep inspirations and the front-crawl arm stroke, the possibility that arm coordination was changed, in part, to compensate for a reduced force-generating capacity per arm stroke should not be overlooked.

The Borg dyspnoea score: a relevant clinical marker of inspiratory muscle weakness in amyotrophic lateral sclerosis.

The aim of the study was to determine whether the Borg dyspnoea scale could be a useful and simple marker to predict respiratory muscle weakness in amyotrophic lateral sclerosis (ALS). From April 1997 to 2001, respiratory function was perfomed in 72 patients together with the Borg score in both the upright (uBorg) and supine (sBorg) positions. Mean upright vital capacity (VC) was 81+/-24% predicted, sniff nasal inspiratory pressure (SNIP) was 55+/-26% pred, maximal inspiratory pressure (P(I,max)) was 57+/-26% pred and arterial carbon dioxide tension (P(a,CO(2))) was 41+/-6 mmHg. The mean Borg scores in the upright and supine positions were 1.7+/-1.5 and 2.2+/-2, respectively. A significant relationship between SNIP and uBorg (r = 0.4; p = 0.0007) and SNIP and sBorg (r = 0.58; p<0.0001) was observed. Upright VC, DeltaVC (measured as the supine fall in VC as a percentage of seated VC), P(I,max) and P(a,CO(2)) were significantly correlated with SNIP. A cut-off value of 3 on the sBorg scale provided the best sensitivity (80%) and specificity (78%) (area under the curve 0.8) to predict a SNIP < or =40 cmH(2)O, indicating severe inspiratory muscle weakness. Patients with a sBorg score > or =3 also exhibited significantly lower VC, P(I,max) and twitch mouth pressure during cervical magnetic stimulation, and slightly higher P(a,CO(2)) (43.7+/-7 versus 39.2+/-5 mmHg; p = 0.05). The Borg dyspnoea scale is a valuable noninvasive test for the prediction of inspiratory muscle weakness in ALS patients.

Assessment of nasal spray deposition pattern in a silicone human nose model using a color-based method.

PURPOSE: To develop a simple and inexpensive method to visualize and quantify droplet deposition patterns. METHODS: Deposition pattern was determined by uniformly coating the nose model with Sar-Gel (a paste that changes from white to purple on contact with water) and subsequently discharging sprays into the nose model. The color change was captured using a digital camera and analyzed using Adobe Photoshop. Several tests were conducted to validate the method. Deposition patterns of different nasal sprays (Ayr, Afrin, and Zicam) and different nasal drug delivery devices (Afrin nasal spray and PARI Sinustar nasal nebulizer) were compared. We also used the method to evaluate the effect of inhaled flow rate on nasal spray deposition. RESULTS: There was a significant difference in the deposition area for Ayr, Afrin, and Zicam. The deposition areas of Afrin nasal spray and PARI Sinustar nasal nebulizer (2 min and 5 min) were significantly different. Inhaled flow rate did not have a significant effect on the deposition pattern. CONCLUSIONS: Lower viscosity formulations (Ayr, Afrin) provided greater coverage than the higher viscosity formulation (Zicam). The nebulizer covered a greater surface area than the spray pump we evaluated. Aerosol deposition in the nose model was not affected by air flow conditions.

Mouth and nasal inspiratory pressure: learning effect and reproducibility in healthy adults.

BACKGROUND: Inspiratory muscle strength measurements have become a cornerstone in monitoring neuromuscular disorders. Usually, sniff nasal inspiratory pressure (SNIP) and maximal inspiratory pressure (MIP) are performed. To our knowledge the session-to-session learning effect has rarely been evaluated for MIP performance and has never been done for SNIP performance. OBJECTIVES: We hypothesized that the sniff manoeuvre was natural and did not need to be learned, whereas the Muller manoeuvre, used for MIP measurement, was an isometric contraction which needed to be learned because it is rarely performed in real life conditions. This hypothesis suggests that from the first session and continuing through a subsequent one, the maximal SNIP value and the number of sniff trials necessary to attain it are more reproducible than the maximal MIP value and the number of Muller manoeuvre trials necessary to attain it. METHODS: Seventy-one healthy subjects were included. SNIP and MIP manoeuvres were repeated 12 and 6 times, respectively, per week during 2 sessions a week apart. RESULTS: We observed a session effect on MIP but not on SNIP. Maximal value for MIP was higher during the second session, whereas SNIP maximal value did not increase during the second session. The number of trials needed to obtain the maximal value for MIP was lower during the second session whereas it was not different for SNIP. CONCLUSIONS: SNIP is less sensitive to a learning effect than is MIP. It requires only a routine warm-up. We suggest that SNIP is preferable to MIP for repeated measurement of inspiratory muscle performance.

Experimental investigation of the concept of a 'breathing zone' using a mannequin exposed to a point source of inertial/sedimenting particles emitted with momentum.

An inhaling mannequin, CALTOOL, was used in a specially ventilated room to compare the concentrations inhaled with those sampled by samplers mounted across the breathing zone. The CALTOOL is made from metal sheets and consists of a cylindrical torso (42 x 24 x 54 cm) with a circular cylinder as head. A circular nozzle simulates the mouth. This nozzle is part of a cassette that holds a filter. The inhalation rate is not periodic but kept constant at nominally 20 l min(-1). The CALTOOL was placed in a horizontal air stream ( approximately 10 cm s(-1)) either facing or back to the wind. In front of the lower chest of the CALTOOL, a particle source was mounted which emitted particles with a momentum directed upwards at an angle of 45 degrees towards the CALTOOL. Five monodisperse aluminium oxide powders were used as test aerosols. The mass median aerodynamic diameters of the test aerosols ranged approximately 10 to 95 mum. Six conically shaped aerosol samplers were mounted horizontally and over the breathing zone of the CALTOOL, one on each shoulder, three across the upper torso, and one at the lower torso centre. Four to six runs per test aerosol and CALTOOL orientation in the airflow were conducted. The samples were analysed gravimetrically. The concentration ratio aerosol sampler to the CALTOOL cassette was determined for the investigated mounting positions. The results showed that when the CALTOOL was exposed to particles emitted with momentum from a point source in front of the lower chest, the variation in concentration over the breathing zone was large. The ratio of the concentration sampled by an aerosol sampler mounted somewhere within the breathing zone to the CALTOOL cassette concentration, would, for specific particle sizes, easily differ by a factor of 3, but may extend up to 10-100, depending on the particular conditions. The basic concept of a breathing zone consisting of a hemisphere of radius 25-30 cm is therefore not well suited for workers handling a point source emitting large particles. For such sampling situations, it is suggested that the radius of the breathing zone is reduced to 10 cm, which may be achieved by a head-mounted sampler.

Asymmetric control of inspiratory and expiratory phases by excitability in the respiratory network of neonatal mice in vitro.

Rhythmic motor behaviours consist of alternating movements, e.g. swing-stance in stepping, jaw opening and closing during chewing, and inspiration-expiration in breathing, which must be labile in frequency, and in some cases, in the duration of individual phases, to adjust to physiological demands. These movements are the expression of underlying neural circuits whose organization governs the properties of the motor behaviour. To determine if the ability to operate over a broad range of frequencies in respiration is expressed in the rhythm generator, we isolated the kernel of essential respiratory circuits using rhythmically active in vitro slices from neonatal mice. We show respiratory motor output in these slices at very low frequencies (0.008 Hz), well below the typical frequency in vitro (approximately 0.2 Hz) and in most intact normothermic mammals. Across this broad range of frequencies, inspiratory motor output bursts remained remarkably constant in pattern, i.e. duration, peak amplitude and area. The change in frequency was instead attributable to increased interburst interval, and was largely unaffected by removal of fast inhibitory transmission. Modulation of the frequency was primarily achieved by manipulating extracellular potassium, which significantly affects neuronal excitability. When excitability was lowered to slow down, or in some cases stop, spontaneous rhythm, brief stimulation of the respiratory network with a glutamatergic agonist could evoke (rhythmic) motor output. In slices with slow (<0.02 Hz) spontaneous rhythms, evoked motor output could follow a spontaneous burst at short (60 s. We observed during inspiration a large magnitude (approximately 0.6 nA) outward current generated by Na(+)/K(+) ATPase that deactivated in 25-100 ms and thus could contribute to burst termination and the latency of evoked bursts but is unlikely to control the interburst interval. We propose that the respiratory network functions over a broad range of frequencies by engaging distinct mechanisms from those controlling inspiratory duration and pattern that specifically govern the interburst interval.

Alterations in maximal inspiratory mouth pressure during a 400-m maximum effort front-crawl swimming trial.

AIM: The aim of this study was to examine the changes of maximal inspiratory mouth pressure (PImax) during a 400-m front crawl swimming trial. METHODS: Eleven well-trained competitive swimmers (age: 17.6+/-0.8 years, mean+/-SE) performed a 400-m front-crawl trial with maximum effort (296.2+/-4.76 s). Then, on different days they swam a 300-m, 200-m and 100-m trials at a velocity corresponding to the 400-m trial. Measurements of PImax from residual volume at upright body position before and immediately after each trial were conducted using a portable mouth pressure meter. RESULTS: Maximal inspiratory mouth pressure did not change significantly after the 100-m and 200-m trial compared to baseline (131.8+/-9.7 and 123.7+/-10.3 vs. 140.9+/-8.9 cmH(2)O, P>0.05). However, PImax was significantly lower after the 300-m (118.8+/-7 cmH(2)O, P=0.02) and 400-m trials (118.1+/-9.9 cmH(2)O, P=0.01). CONCLUSIONS: These results indicate that during a maximum effort of 400-m front crawl, the reduction of inspiratory muscle strength occurs after 300-m. This should be considered for competitive swimming training by implementing swim race distance-specific respiratory muscle training.