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Biomedical subjects

A Tully

Publications and source records attributed to A Tully.

At least 19 recordsLinked to original sources
PubMed2006

Objective assessment of gynecologic laparoscopic skills using the LapSimGyn virtual reality simulator.

BACKGROUND: Safe realistic training and unbiased quantitative assessment of technical skills are required for laparoscopy. Virtual reality (VR) simulators may be useful tools for training and assessing basic and advanced surgical skills and procedures. This study aimed to investigate the construct validity of the LapSimGyn VR simulator, and to determine the learning curves of gynecologists with different levels of experience. METHODS: For this study, 32 gynecologic trainees and consultants (juniors or seniors) were allocated into three groups: novices (0 advanced laparoscopic procedures), intermediate level (>20 and <60 procedures), and experts (>100 procedures). All performed 10 sets of simulations consisting of three basic skill tasks and an ectopic pregnancy program. The simulations were carried out on 3 days within a maximum period of 2 weeks. Assessment of skills was based on time, economy of movement, and error parameters measured by the simulator. RESULTS: The data showed that expert gynecologists performed significantly and consistently better than intermediate and novice gynecologists. The learning curves differed significantly between the groups, showing that experts start at a higher level and more rapidly reach the plateau of their learning curve than do intermediate and novice groups of surgeons. CONCLUSION: The LapSimGyn VR simulator package demonstrates construct validity on both the basic skills module and the procedural gynecologic module for ectopic pregnancy. Learning curves can be obtained, but to reach the maximum performance for the more complex tasks, 10 repetitions do not seem sufficient at the given task level and settings. LapSimGyn also seems to be flexible and widely accepted by the users.

Clinical Competence↗
PubMed2006

Virtual reality simulation training can improve technical skills during laparoscopic salpingectomy for ectopic pregnancy.

OBJECTIVES: To assess the first commercially available virtual reality (VR) simulator to incorporate procedural modules for training of inexperienced gynaecological surgeons to perform laparoscopic salpingectomy for ectopic pregnancy. DESIGN: Prospective cohort study. SETTING: Departments of surgery and gynaecology in central London teaching hospitals. SAMPLE: Thirty gynaecological surgeons were recruited to the study, and were divided into novice (<10 laparoscopic procedures), intermediate (20-50) and experienced (>100) groups. METHODS: All subjects were orientated to the VR simulator with a basic skills task, followed by performing ten repetitions of the virtual ectopic pregnancy module, in a distributed manner. MAIN OUTCOME MEASURES: Operative performance was assessed by the time taken to perform surgery, blood loss and total instrument path length. RESULTS: There were significant differences between the groups at the second repetition of the ectopic module for time taken (median 551.1 versus 401.2 versus 249.2 seconds, P = 0.001), total blood loss (median 304.2 versus 187.4 versus 123.3 ml, P = 0.031) and total instrument path length (median 17.8 versus 8.3 versus 6.8 m, P = 0.023). The learning curves of the experienced operators plateaued at the second session, although greater numbers of sessions were necessary for intermediate (seven) and novice (nine) surgeons to achieve similar levels of skill. CONCLUSIONS: Gynaecological surgeons with minimal laparoscopic experience can improve their skills during short-phase training on a VR procedural module. In contrast, experienced operators showed nonsignificant improvements. Thus, VR simulation may be useful for the early part of the learning curve for surgeons who wish to learn to perform laparoscopic salpingectomy for ectopic pregnancy.

Clinical Competence↗
PubMed2004

Stress, sources of stress and ways of coping among psychiatric nursing students.

This study measured levels of distress, sources of stress and ways of coping of a convenience sample of psychiatric nursing students (n = 35). Instruments used were the 30-item General Health Questionnaire, the Jones and Johnson (1997) Student Nurse Stress Index, Parkes (1985) Ways of Coping Questionnaire and a demographic questionnaire. Findings revealed that all students were significantly distressed, exceeding a conventional cut-off score of 5 on the 30-item General Health Questionnaire. Students were found to have limited coping skills. Preparing to become a nurse in this setting was found to be significantly emotionally stressful and a possible risk to the well-being of students. This study provides a baseline from which to address the problem of stress among diplomate psychiatric nursing students.

Adaptation, Psychological↗
PubMed1998

Cardiac versus noncardiac limits to exercise after heart transplantation.

BACKGROUND: To determine whether the reduced exercise capacity of patients after heart transplantation is primarily a result of decreased cardiac or peripheral vascular factors, we examined the cardiac output (CO) and right atrial pressure (Pra) relation during graded cycle ergometry. METHODS AND RESULTS: We studied 12 male patients (51.2+/-15.3 years [mean+/-SD]) 35.3+/-12.5 weeks after heart transplantation and 6 young healthy men. Patients had a normal increase in CO with increasing oxygen uptake (VO2) (CO = 0.00597 VO2 + 4.4, r = 0.83). Mean (+/-SEM) heart rate increased from 97.0+/-5.0 beats/min at rest to 146.9+/-6.9 beats/min at peak effort compared with the increase of 67.2+/-1.9 beats/min to 187.2+/-2.5 beats/min in the normal group. Pra in patients increased from 1.6+/-1.0 mm Hg at rest to 8.9+/-1.6 mm Hg during mild exercise but did not increase further at the highest work rates, even though CO continued to increase. In the normal group there was an initial increase in Pra from rest to exercise transition but little further change in Pra with increasing CO. Aerobic capacity (peak VO2) did not increase when cardiac function was increased with dobutamine during exercise in two patients. CONCLUSIONS: The steep increase in CO relative to Pra during severe exercise in patients who undergo heart transplantation argues against the heart as the sole limiting factor during maximal effort.

Atrial Function, Right↗
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↗
PubMed1995

Thyroid cartilage movements during breathing.

We measured lateral (outward) thyroid cartilage displacement (TCD) of the larynx in six supine anesthetized (intravenous chloralose) dogs. Combined left and right TCDs were measured with linear transducers attached by a thread to the thyroid alae. During tidal breathing via a tracheostomy, phasic inspiratory TCD occurred in all dogs [0.66 +/- 0.2 mm (mean +/- SE)] together with phasic inspiratory electromyographic activity in the cricothyroid (CT) and posterior cricoarytenoid (PCA) muscles. During brief tracheal occlusions, TCD increased significantly to 1.27 +/- 0.2 mm (P = 0.001), accompanied by an increase of 95-115% in the peak CT and PCA electromyograms. Bilateral supramaximal electrical stimulation of the external branches of the superior laryngeal nerve (ExSLN) produced a TCD of 9.9 +/- 0.8 mm; however, similar stimulation of the recurrent laryngeal nerve (RLN) produced a TCD of only 1.33 +/- 0.1 mm (P = 0.0001). Furthermore, bilateral section of the ExSLN in five dogs significantly reduced tidal TCD by 48.7 +/- 24.4% (P < 0.05), and bilateral section of both the ExSLN and RLN resulted in slight phasic inward TCD (-0.06 +/- 0.05 mm). Thus, it appears that the activities of both the CT and RLN-innervated muscles (probably the PCA muscle) contribute to tidal breathing TCD. These findings suggest that inspiratory dilation of the hypopharynx is mediated by contractions of CT and PCA muscles.

Anesthesia↗
PubMed1993

Cardiorespiratory consequences of expiratory chest wall compression during mechanical ventilation and severe hyperinflation.

OBJECTIVES: To measure and compare the effects of manual expiratory compression of either the rib cage or abdomen on cardiac output, end-expiratory lung volume, and other cardiorespiratory variables in an animal model that mimics the severe pulmonary hyperinflation and hemodynamic impairment occurring in patients with severe acute asthma during mechanical ventilation. DESIGN: Prospective, randomized, crossover trial. SETTING: Research laboratory. SUBJECTS: Seven cross-bred, anesthetized, supine dogs. INTERVENTIONS: The following sequence was employed: a) spontaneous breathing without pulmonary hyperinflation; b) positive-pressure ventilation with severe pulmonary hyperinflation (produced by an external variable expiratory flow resistor); c) approximately 7 mins of manual expiratory compression of either the rib cage or abdomen during positive-pressure ventilation-hyperinflation. This sequence was then repeated, incorporating the alternative type of expiratory compression. MEASUREMENTS AND MAIN RESULTS: Cardiac output (measured by thermodilution), aortic pressure, pleural (esophageal) pressure, and changes in end-expiratory lung volume were measured. The decrease in cardiac output due to mechanical ventilation with pulmonary hyperinflation was exacerbated by rib cage compression (p < .001; spontaneous breathing 2.9 +/- 0.2 L/min, hyperinflation 1.5 +/- 0.1 L/min, and rib cage compression 1.0 +/- 0.1 [SEM] L/min). However, the positive-pressure ventilation-hyperinflation-induced decrease in cardiac output was attenuated by abdominal compression (p < .001; spontaneous breathing 3.3 +/- 0.2 L/min, hyperinflation 1.4 +/- 0.1 L/min, and abdominal compression 2.1 +/- 0.1 L/min). Mean aortic pressure returned to prehyperinflation levels during abdominal compression (p < .001; spontaneous breathing 126 +/- 2 mm Hg, hyperinflation 75 +/- 5 mm Hg, and abdominal compression 120 +/- 3 mm Hg). Both types of compression were similarly effective (p > .75) in increasing mean expiratory pleural pressure, so that end-expiratory lung volume was similarly (p > .25) reduced (0.45 +/- 0.05 and 0.40 +/- 0.05 L for rib cage and abdominal compressions, respectively) in this non-air flow, limiting animal model. CONCLUSIONS: The cardiorespiratory effects of manually compressing the rib cage or abdomen during expiration in this animal study suggest that these techniques should be carefully evaluated in mechanically ventilated patients with severe acute asthma.

Abdomen↗
PubMed1992

Women's perceptions of cesarean and vaginal delivery: another look.

Perception of the birth experience was examined in a sample of 106 women who had unplanned cesarean deliveries, 113 who had planned cesarean deliveries, and 254 who had vaginal deliveries. Vaginally delivered women had more positive perceptions than their unplanned cesarean counterparts (p < .001). There were no differences in perceptions between the unplanned and planned cesarean groups, or between the planned cesarean and vaginal groups. General anesthesia for cesarean delivery was associated with more negative perceptions than regional anesthesia, and regional anesthesia for vaginal delivery was associated with more negative perceptions than no or local anesthesia. Pain intensity and physical distress were negatively correlated with perceptions.

Anesthesia, Obstetrical↗
PubMed1992

Effects of cricothyroid muscle contraction on upper airway flow dynamics in dogs.

We studied the effects of cricothyroid muscle (CT) contraction on upper airway flow dynamics in eight prone open-mouth anesthetized dogs. Animals were mechanically ventilated via a tracheostomy while a constant airflow (Vuaw) passed through the isolated upper airway. Nasal airflow (Vn) was monitored using a nasal mask and pneumotachograph. Bilateral CT contraction was induced by electrical stimulation of the external branches of the superior laryngeal nerves. During CT contraction with Vuaw of 100-443 ml/s in the inspiratory direction, total upper airway resistance (Ruaw) fell by 49.1 +/- 5.4% (SE) while supraglottic resistance fell by 63.6 +/- 3.6%; simultaneously Vn fell by 55.3 +/- 3.8% and Vuaw increased by 7.2 +/- 1.7%. Similar results were obtained when Vuaw was in the expiratory direction. In three dogs in which the attachments of the CT to either the thyroid or cricoid cartilage were severed, superior laryngeal nerve stimulation had no systematic effect on Ruaw. Because visual assessment during CT contraction consistently revealed dilation of the piriform recesses, we suggest that CT contraction is associated with pharyngeal dilation, which in open-mouth dogs (with overlapping soft palate and epiglottis) redistributes flow to the oral route with a net reduction in Ruaw. Thus the CT may have a respiratory role as a pharyngeal dilator.

Airway Resistance↗
PubMed1992

Pharyngeal dilation associated with cricothyroid muscle contraction in dogs.

The mechanical function of phasic respiratory-related activity of the cricothyroid muscle of the larynx is poorly understood. We studied five adult cross-bred dogs (weight 14-20 kg) deeply anesthetized with pentobarbitone sodium, mechanically ventilated via a tracheostomy, and placed prone with the mouth open. Bilateral cricothyroid muscle contraction was induced by supramaximal electrical stimulation of the external branches of the superior laryngeal nerve. Computerized axial tomography was used to assess effects of cricothyroid muscle contraction. During cricothyroid muscle contraction, oropharyngeal (tip of epiglottis) cross-sectional area increased by 18.0 +/- 3.0% (SE) (P = 0.008), whereas combined left and right piriform recess cross-sectional area increased by 85 +/- 25% (n = 4; P = 0.02) at the midepiglottic level and by 152 +/- 37% (P = 0.01) at the base of the epiglottis. Furthermore, at the base of the epiglottis the maximum horizontal distance between the alae of the thyroid cartilage increased by 21 +/- 8% (P = 0.05). In contrast, lateral glottic diameter decreased by 52 +/- 2% (n = 4; P = 0.01), whereas dorsoventral glottic diameter increased by 18 +/- 5% (n = 4; P less than 0.02). The cricothyroid muscle, therefore, has the capacity to act simultaneously as a pharyngeal dilator and a glottic constrictor and thus may play a role in the control of oropharyngeal as well as laryngeal patency.

Animals↗
PubMed1991

Pressure-diameter relationships of the upper airway in awake supine subjects.

In awake supine normal subjects, dimensional changes of the oropharyngeal airway were measured during exposure to negative intraluminal pressures. The pressure was generated 1) "actively" by subjects inspiring against an externally occluded airway or 2) "passively" by external suction at the mouth during voluntary glottic closure with no inspiratory effort. Airway dimensions were imaged with X-ray fluoroscopy and anteroposterior diameters measured at levels corresponding to cervical vertebra 3 and 4 (C3 and C4). Cephalad axial displacement of the hyoid bone (CDHY) was also measured. During the "active" maneuver, airway diameters and position were maintained at resting levels despite airway pressure up to -15 cmH2O. In contrast, during the passive maneuver at -15 cmH2O, C3 was only 15 +/- 9% and C4 only 47 +/- 8% of control; CDHY was 5.6 +/- 1.8 mm. In three subjects airway wall apposition occurred and persisted until an active inspiratory effort. We conclude that, in the absence of inspiratory effort, negative oropharyngeal airway pressures result in marked narrowing and cephalad displacement of the upper airway, even during wakefulness. Therefore, our data suggest that the complex interaction of upper airway and thoracic muscle activity is critical in determining the effective compliance and patency of the upper airway, which is readily collapsible even in normal subjects.

Adult↗
PubMed1991

Influence of posterior cricoarytenoid muscle activity on pressure-flow relationship of the larynx.

We examined the effect of posterior cricoarytenoid (PCA) muscle activity on the pressure-flow (PV) relationship of the larynx in five anesthetized tracheostomized dogs. The PCA activity was recorded using bipolar fine-wire electrodes, expressed as a percentage of the quiet breathing level and altered by mechanical ventilation, changes in lung volume, and chest wall compression. Subglottic pressure was recorded while a constant flow of air was passed through the upper airway. In the absence of PCA activity the PV relationship was alinear and could be described by a power function (P = K0Va, where K0 and a are constants). The slope of the log P-log V plots in the absence of PCA and thyroarytenoid activity was 1.83 +/- 0.02 (SD), whereas with increasing PCA activity it was 1.88 +/- 0.11. An effective hydraulic diameter (DH) was calculated for 20% increments of PCA activity, and in two dogs glottic diameter (Dg) was calculated from glottic area measurements obtained by fiber-optic laryngoscopy. Both DH and Dg increased linearly with increasing PCA activity. Denervation of the cricothyroid muscle had no systematic effect on laryngeal resistance. The results indicate that the PV relationship of the larynx may be described by a power function with a single exponent, the magnitude of which is independent of glottic dilator muscle activity and consistent with orifice flow. However, laryngeal diameter increases linearly with PCA activity in the range studied.

Airway Resistance↗
PubMed1991

Blood flow distribution within the rib cage muscles.

We used 15-microns radiolabeled microspheres to study the regional distribution of blood flow (Q) among parasternal (PS), transversus thoracis, and external (EI) and internal intercostal muscles (II) in nine anesthetized supine mongrel dogs. We measured Q (ml.min-1.100 g-1) in each intercostal space (ICS) during spontaneous breathing, inspiratory resistive loading, and mechanical ventilation following paralysis. At necropsy the EI, II, and PS were excised and sampled separately for each ICS. During paralysis there was no consistent gradient in Q among the PS, II, and EI muscles. During spontaneous breathing, Q to PS increased linearly by 125% between the first and fourth to sixth ICS, Q to EI decreased progressively from the first/second ICS to the fifth/sixth ICS, whereas Q to the II was uniform. During inspiratory resistive loading, in which mouth pressures of -16 +/- 4 cmH2O were generated, the PS gradient was similar to that during spontaneous breathing. Also, Q to the EI increased in the cranial interspaces (P less than 0.02), whereas Q to the II of the seventh/eighth ICS was greater than that of the first/second ICS (P less than 0.001). Furthermore, with loading, ventrodorsal gradients in Q appeared within both EI and II interspaces. There was no consistent gradient in Q within the transversus thoracis muscle during any of the interventions. Our results demonstrate nonuniform Q within PS, EI, and II during both spontaneous and inspiratory resistive loaded breathing. On the assumption that changes in Q reflect changes in activation, our results suggest systematic topographical patterns of recruitment of rib cage respiratory muscles.

Animals↗
PubMed1991

Regional distribution of blood flow within the diaphragm.

We investigated the regional distribution of blood flow (Q) within the costal and crural portions of the diaphragm in a total of eight anesthetized supine mongrel dogs. Q was measured with 15-microns microspheres, radiolabeled with three different isotopes, injected into the left ventricle during spontaneous breathing (SB), inspiratory resistive loading (IR), and mechanical ventilation after paralysis (P). At necropsy, the costal and crural portions of each hemidiaphragm were arbitrarily subdivided along a sagittal plane into five to seven and three sections, respectively. During P, there was a dorsoventral Q gradient within the costal part of the diaphragm. During SB there was a fourfold increase in the gradient of Q. Furthermore, during IR, in which mouth pressures of -16 +/- 4 cmH2O were generated, there was a further increase in the gradient of Q. During both SB and IR, Q to the most ventral portion of the costal diaphragm was 26 +/- 6% less than the peak value. In two dogs, studied prone and supine, there was no difference in the Q gradients between the two postures. Over the dorsal 80% of the costal diaphragm there was also a dorsoventral gradient of muscle thickness, such that the most dorsal part was 54 +/- 2% (n = 5) that of the ventral portion. In contrast, there was no consistent gradient of Q or muscle thickness within the crural diaphragm. Our results demonstrate a topographical gravity-independent distribution of Q in the costal, but not the crural, diaphragm.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1990

Relationship between thyroarytenoid activity and laryngeal resistance.

We examined the relationship between subglottic pressure (P), flow (V), and thyroarytenoid (TA) muscle activity in six anesthetized tracheostomized dogs while a constant flow (0.05-1.2 l/s) of warmed humidified air was passed through the upper airway in an expiratory direction. The TA activity was recorded by fine bipolar wire electrodes and was reflexly altered by changes in lung volume and chest wall compression. The integrated muscle activity was expressed as a percentage of a maximal peak integrated TA activity (%max). In the absence of TA activity the pressure-flow relationship was alinear and could be described by a power function. Log-log P-V plots at varying levels of TA activity were linear, with a slope a of 1.84 +/- 0.07 (SD). When TA activity increased, laryngeal resistance increased exponentially. An effective hydraulic diameter was calculated for increments in %max TA and decreased linearly with %max TA. In three dogs the glottic diameter was computed from glottic area measured by fiber-optic laryngoscopy, and it also decreased linearly as TA increased. Sectioning of the external motor branch of the superior laryngeal nerve to the cricothyroid muscle demonstrated no consistent effect on laryngeal resistance over a range of TA activity. The results indicate that laryngeal dimensions decrease linearly with TA activity. However, the P-V relationship of the larynx may be described by a power function, with a single exponent consistent with an orifice flow regimen. Spontaneous activity of the cricothyroid muscle does not measurably influence this relationship.

Airway Resistance↗
PubMed1989

Postural changes in spontaneous and evoked regional diaphragmatic activity in dogs.

We addressed the question whether gravity-dependent differences in passive tension and length of the diaphragm are associated with differences in its regional activation. By using intramuscular electrodes, we measured the electromyographic activity of different parts of the diaphragm (Edi) during quiet breathing in several postures in 13 anesthetized mongrel dogs. The Edi of the left and right costal hemi-diaphragm was compared between the left and right lateral decubitus postures, whereas that from the substernal and crural regions was compared between the supine and prone positions. On changing posture, the Edi of the dependent part of the diaphragm decreased in both cases, whereas that of the non-dependent part increased. The results were consistent with reflex modulation of regional diaphragm activation in response to postural changes in local resting length. However, these changes in Edi persisted after bilateral vagotomy, cordotomy (C7-T1) and dorsal rhizotomy of the C5-C7 roots. Compound muscle action potentials, recorded in different regions of the diaphragm and evoked by supramaximal stimulation of the phrenic nerves, were altered with changes in posture in the same direction as Edi. Because the stimuli were supramaximal, these changes reflected systematic changes in the recording conditions with posture, possibly because of a combination of 1) changes in the electrical environment surrounding the intramuscular electrodes and 2) passive changes in muscle length. Our results demonstrate systematic, reproducible, posture-dependent changes in regional Edi that may not be due to different neural drive.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1987

Effect of expiratory glottic constriction on lung volume and pattern of breathing in adult dogs.

We examined the effect of laryngeal constriction on the pattern of breathing in 4 anaesthetized adult mongrel dogs. By means of a T-shaped tracheostomy tube the larynx could be repeatedly excluded or included in the breathing circuit. Marked expiratory activity of the thyroarytenoid muscle (TA), the main glottic constrictor, was induced by injection of 100-400 ml of air into the pleural space or by inhalation of histamine aerosol (2 dogs) which resulted in rapid shallow breathing. In 21 pairs of runs in the 4 dogs switching from tracheostomy breathing to oral breathing decreased mid-expiratory flow and frequency by 85 +/- 2% (P less than 0.001) and 48 +/- 4% (P less than 0.001), respectively. Although expiratory duration (TE) increased, end-expiratory lung volume also increased by 40 +/- 8 ml or 21 +/- 4% of the tidal volume (VT) during tracheostomy breathing (P less than 0.001). In contrast, VT remained unchanged (P = 0.9). Instantaneous ventilation decreased due to both the prolongation of TE and an increase in inspiratory duration. Our results indicate that laryngeal braking can be recruited in adult dogs and interacts with reflex mechanisms that modulate respiratory timing, thereby significantly influencing end-expiratory lung volume, ventilation and the pattern of breathing. Simulation of the laryngeal mechanism by expiratory resistive loading at the tracheostomy below the larynx points to a non-reflex mechanical effect of the larynx as a resistance in series.

Aerosols↗