Involuntary cough is superior to voluntary cough for identifying stress urinary incontinence.

INTRODUCTION: Voluntary cough (VC) and the laryngeal expiration reflex (LER) provoke stress urinary incontinence (SUI). The aim of this article is to analyze the effectiveness of these stimuli on the timing of urinary leaks. MATERIAL AND METHODS: Urodynamic testing using pressure catheters was performed on 123 subjects with history of SUI. The LER was triggered using the induced reflex cough test (iRCT). Each subject was tested with VC and LER and leaked with one or both stimuli. The occurrence and timing of leaks were recorded. RESULTS: The peak and average intra-abdominal pressures were 16-19% greater for LER compared to VC. Of the 123 subjects, LER caused leak in 118 (96%), VC in 71 (58%) and both in 66 (54%). For LER compared to VC, leak was more likely to occur during or immediately after the first expiratory effort. The electromyogram for VC and LER were similar. CONCLUSIONS: The iRCT reliably initiated the LER and triggered SUI more effectively than VC. During VC, the smooth muscle of the internal urethral sphincter (IUS) starts to contract during inspiration, and constriction of the IUS continues into the expiratory phase; this increased urethral tonicity would lessen the likelihood of SUI. We refer to this as the inspiration closure reflex (ICR). With LER the inspiration would not take place, and the first expiratory effort would be against a non-constricted IUS, making leak more likely. Our findings disprove the pressure transmission theory. The internal and external urethral sphincters may both increase urethral closure pressure and resistance.

Inspiration closure reflex: the effect of respiration on intrinsic sphincters.

INTRODUCTION: The functions of the lower esophageal sphincter (LES) and internal urethral sphincter (IUS) have not been reported during voluntary and involuntary respiratory maneuvers. METHODS: In this study we performed a prospective barium videofluoroscopy study (BSV) of the LES on 4 healthy adult men during voluntary cough (VC), laryngeal expiration reflex (LER), breath-hold maneuvers, and normal inspiration. One subject had fiber-optic pressure catheters placed in the LES and IUS, and electromyographic recording of the right T7-8 intercostals during respiration. RESULTS: BSV showed closure and relaxation of the LES corresponding to the inspiration and expiration of VC. The LES was patent during the LER. There was closure of the LES during the deep inspiration/breath-hold event. Pressure catheters in the LES and IUS showed increased pressure during inspiration. CONCLUSIONS: These observations suggest that pulmonary inspiration afferents elicit a patterned reflex motor response in the LES and IUS, referred to as the inspiration closure reflex (ICR).

Voluntary and reflex cough and the expiration reflex; implications for aspiration after stroke.

Aspiration is a common result of stroke, and may lead to lung infections and pneumonia. Cough may prevent this aspiration and thus prevent the pneumonia. We review the four types of cough usually used to assess aspiration risk: voluntary cough (VC), reflex cough (RC), the laryngeal expiration reflex (LER), and cough on swallow (CoS). VC is easy to test but starts with an inspiration that may cause aspiration, and is controlled by cortico-brainstem pathways that may not be involved in influencing aspiration. RC also starts with an inspiration, and requires instrumental intervention, but is more relevant to protecting the lungs. The LER starts with an expiration, so is 'anti-aspiration', and is easy to test, but its neural mechanisms have not been fully analysed. CoS can be tested at the same time as direct observations of aspiration, but little is known about its neural mechanisms. Each method has its advocates, and the purpose of the review is to discuss how each may be applied and how the information from each may be assessed and valued.

Intra-abdominal pressures during voluntary and reflex cough.

BACKGROUND: Involuntary coughing such as that evoked from the larynx, the laryngeal cough reflex (LCR), triggers a coordinated contraction of the thoracic, abdominal and pelvic muscles, which increases intra-abdominal pressure (IAP), displaces the diaphragm upwards and generates the expiratory force for cough and airway clearance. Changes in the IAP during voluntary cough (VC) and the LCR can be measured via a pressure catheter in the bladder. This study evaluated the physiological characteristics of IAP generated during VC and the LCR including peak and mean pressures and calculations of the area under the curve (AUC) values during the time of the cough event or epoch. METHODS: Eleven female subjects between the ages of 18 and 75 underwent standard urodynamic assessment with placement of an intravesicular catheter with a fiberoptic strain gauge pressure transducer. The bladder was filled with 200 ml of sterile water and IAP recordings were obtained with VC and the induced reflex cough test (RCT) using nebulized inhaled 20% tartaric acid to induce the LCR. IAP values were used to calculate the area under the curve (AUC) by the numerical integration of intravesicular pressure over time (cm H2O.s). RESULTS: The mean (+/- SEM) AUC values for VC and the LCR were 349.6 +/- 55.2 and 986.6 +/- 116.8 cm H2O.s (p < 0.01). The mean IAP values were 45.6 +/- 4.65 and 44.5 +/- 9.31 cm H2O (NS = .052), and the peak IAP values were 139.5 +/- 14.2 and 164.9 +/- 15.8 cm H2O (p = 0.07) for VC and LCR, respectively. CONCLUSION: The induced LCR is the involuntary rapid and repeated synchronous expiratory muscle activation that causes and sustains an elevated IAP over time, sufficient for airway protection. VC and LCR have different neurophysiological functions. Quantification of the LCR using AUC values and mean or peak IAP values may be useful as a clinical tool for determining neurophysiological airway protection status and provide a quantitative assessment of changes in a patient's functional recovery or decline.

Effect of stroke location on the laryngeal cough reflex and pneumonia risk.

BACKGROUND: The purpose of this study was to evaluate the risk of developing pneumonia in acute stroke patients comparing the early anatomical stroke location and laryngeal cough reflex (LCR) testing. METHODS: A prospective study of 818 consecutive acute stroke patients utilizing a reflex cough test (RCT), which assesses the neurological status of the LCR compared to magnetic resonance imaging or computerized tomography for stroke location and subsequent pneumonia outcome. Stroke diagnosis and stroke location were made by a neurologist and clinical radiologist, respectively; both were blinded to the RCT results. RESULTS: Brainstem (p-value < .007) and cerebral strokes (p-value < .005) correlated with the RCT results and pneumonia outcome. Of the 818 patients, 35 (4.3%) developed pneumonia. Of the 736 (90%) patients who had a normal RCT, 26 (3.5%) developed pneumonia, and of the 82 (10%) patients with an abnormal RCT, 9 (11%) developed pneumonia despite preventive interventions (p-value < .005). The RCT had no serious adverse events. CONCLUSION: The RCT acted as a reflex hammer or percussor of the LCR and neurological airway protection and indicated pneumonia risk. Despite stroke location, patients may exhibit "brainstem shock," a global neurological condition involving a transient or permanent impairment of respiratory drive, reticular activating system or LCR. Recovery of these functions may indicate emergence from brainstem shock, and help predict morbidity and mortality outcome.

Electrophysiologic latency to the external obliques of the laryngeal cough expiration reflex in humans.

OBJECTIVE: The purpose of this study was to trigger the laryngeal cough expiration reflex using inhaled tartaric acid aerosol and to record the latency between the time of initiation of the laryngeal cough expiration reflex component of the laryngeal cough reflex and the onset of electromyographically recorded responses in the external abdominal oblique in humans. DESIGN: Five male subjects were tested in the seated position, and four latencies were recorded for each subject. The latencies were recorded from laryngeal stimulation to an electromyogram in the muscle belly of the left external abdominal oblique. The time line was activated by a microswitch attached to a breath-activated nebulizer. Data were analyzed using SPSS for mean latency and standard deviation. RESULTS: The mean (standard deviation) latency to the external abdominal oblique muscle was 17.6 +/- 10.6 msec. No adverse events to inhalation were reported. CONCLUSION: SIn humans, nebulized tartaric acid stimulates primarily rapid adapting receptors in the supraglottic larynx rather than C-fiber receptors. This receptor location in humans evolved neurologically to protect the airway during speech and swallowing, making the laryngeal cough expiration reflex an inseparable component of the laryngeal cough reflex, thus making it clinically significant when assessing airway protection.

Effect of tartaric acid-induced cough on pulmonary function in normal and asthmatic humans.

OBJECTIVE: The laryngeal cough reflex and the laryngeal cough expiratory reflex are brainstem reflexes that protect the upper airway from significant aspiration. The purpose of this investigation was to examine the effects of tartaric acid-induced cough on pulmonary function in normal healthy and asthmatic individuals. DESIGN: Twenty healthy and 20 asymptomatic, medicated, asthmatic volunteers engaged in a two-part evaluation of pulmonary function testing. All 40 subjects were nonsmokers. The reflex cough test, a 20% solution of prescription-grade L-tartaric acid dissolved in 0.15 M NaCl solution, initiated the laryngeal cough expiratory reflex/laryngeal cough reflex. The solution was placed in a Bennett Twin nebulizer and inhaled as a microaerosol. Pulmonary function testing was with a Spiromate AS-600. Baseline pulmonary function testing was initially performed, followed by two separate inhalations of the reflex cough test. The pulmonary function testing was repeated 5 min after the second reflex cough test. RESULTS: Statistically significant changes seen after the reflex cough test included increases in the peak inspiratory flow in normal subjects (P = 0.004) and in the peak expiratory flow in asthmatic subjects (P = 0.014). No respiratory adverse events occurred after the reflex cough test. CONCLUSIONS: Explanations for these findings include the possibility that tartaric acid-induced cough produces central nervous system-mediated bronchodilatation, through the cough itself or by secondary mechanisms.

Effect of acute unilateral middle cerebral artery infarcts on voluntary cough and the laryngeal cough reflex.

OBJECTIVE: The purpose of this study was to assess the effect of acute unilateral middle cerebral artery (MCA) infarctions in right-handed subjects on their ability to elicit voluntary cough (VC), and separately to assess the laryngeal cough reflex using the reflex cough test. DESIGN: This prospective, clinical study involved 30 right-handed, alert subjects with no previous history of stroke or asthma and with an infarction of the MCA distribution as seen on computed tomographic or magnetic resonance images. Subjects could follow verbal commands. A total of 16 subjects had right MCA infarcts and 14 had left MCA infarcts. VC responses and reflex cough test results were compared with the side of the infarct. The reflex cough test used nebulized tartaric acid. RESULTS: The laryngeal cough reflex was normal in all 30 subjects, irrespective of side of MCA infarction, and none developed aspiration pneumonia. Eleven of the 14 subjects who had a left MCA infarct had an abnormal VC (78.6%) and showed cough apraxia. All 16 subjects with right infarcts produced a VC. Subjects with left infarcts were more likely to have an abnormal VC than those subjects with right lesions (P < 0.001). CONCLUSIONS: VC is of limited use in screening subjects for aspiration pneumonia risk. A normal laryngeal cough reflex indicated a neurologically protected airway.

Joining together to combat poverty.

The International Poverty and Health Network (IPHN) was created in December 1997 following a series of conferences organized by the World Health Organization, with the aim of integrating health into plans to eradicate poverty. Around 1.3 billion people live on less than US$1 per day. Of the 4.4 billion people in developing countries nearly 60% lack access to sanitation, 30% do not have clean water, 20% have no health care, and 20% do not have enough dietary energy and protein. Even among rich nations there are gross socioeconomic inequalities. Many children are robbed of their physical and mental potential through poverty. Expressed in constant 1963 US dollars, an average Croatian family needed the annual income of US$894 to meet the poverty line in 1960 and US$9,027 in 1995. Accordingly, 9-25% of Croatian households were below the poverty line between 1960 and 1995. The increase in the poverty rate after 1991 was compounded by the war that destroyed almost a third of industrial capacity and infrastructure. Dissipation of the communist economy and inadequate privatization have contributed to the increase in unemployment rate, corruption, and other social ills. IPHN invited Croatian Medical Journal to publish this editorial to help push the issue of poverty up political and medical agendas on a global level. We argue that a factor contributing to the failure of most large-scale programs against poverty to date is the excessive emphasis on material and infrastructure assistance at the expense of spiritual, moral, and intellectual development.

Anesthesia for the superior laryngeal nerves and tartaric acid-induced cough.

OBJECTIVE: The internal branch of the superior laryngeal nerve (ibSLN) conveys impulses for the laryngeal cough reflex, which protects the laryngeal aditus and prevents the development of aspiration pneumonia. The purpose of this study was to determine the effect of bilateral anesthesia of the ibSLN on the cough reflex after inhalation of a nebulized chemoirritant solution of tartaric acid. DESIGN: Prospective, clinical investigation. SETTING: Outpatient. PARTICIPANTS: Nine healthy volunteers. INTERVENTIONS: Bilateral injections of 2% lidocaine solution without epinephrine into the paraglottic space containing the ibSLN. MAIN OUTCOME MEASURES: The tidal volume after inhalation of a nebulized 20% tartaric acid solution and forced vital capacity (FVC) were measured before and after injection. Data were analyzed using the Wilcoxon signed ranks, Mann-Whitney, and sign tests. RESULTS: Complete anesthesia of the ibSLN abolished the laryngeal cough reflex. Postinjection tidal volumes were significantly lower than preinjection volumes (p<.01). The decrease in tidal volumes for six subjects with complete bilateral anesthesia was significantly larger than the decrease in tidal volumes for three subjects with partial anesthesia (p<.05). FVC in both the six subjects with complete bilateral anesthesia and the three subjects with partial anesthesia did not significantly change from preinjection to postinjection. None of the subjects in this study had complications or adverse respiratory sequelae. CONCLUSION: Tartaric acid-induced cough may be useful in assessing the integrity of the laryngeal cough reflex after anesthesia or in patients with neurologic injury who are at risk of developing aspiration pneumonia. It may also be useful in making the decision whether to resume oral feeding.

Assessing the laryngeal cough reflex and the risk of developing pneumonia after stroke: an interhospital comparison.

BACKGROUND AND PURPOSE: We sought to evaluate the efficacy of testing the laryngeal cough reflex in identifying pneumonia risk in acute stroke patients. METHODS: We performed a prospective study of 400 consecutive acute stroke patients examined using the reflex cough test (RCT) compared with 204 consecutive acute stroke patients from a sister facility examined without using the RCT. The binary end point for the study outcome was the development of pneumonia. RESULTS: Of the 400 patients examined with the RCT, 5 developed pneumonia. Of the 204 patients examined without the RCT, 27 developed pneumonia (P<0.001). Three of the 27 patients died in the rehabilitation hospital of respiratory failure secondary to pneumonia. Seven others were transferred to the emergency department with acute respiratory distress. Power analysis for this comparison was 0.99. There were no other significant differences between the 2 groups. CONCLUSIONS: A normal RCT after an acute stroke indicates a neurologically intact laryngeal cough reflex, a protected airway, and a low risk for developing aspiration pneumonia with oral feeding. An abnormal RCT indicates risk of an unprotected airway and an increased incidence of aspiration pneumonia. Alternate feeding strategies and preventive measures are necessary with an abnormal RCT. Clinical treatment algorithm and prescription of food, fluids, and medications are discussed on the basis of RCT results.

Anatomy of the internal branch of the superior laryngeal nerve.

The purpose of this study was to determine the length and distribution of the branches of the internal branch of the superior laryngeal nerve (ibSLN) and describe the initial afferent pathway for the laryngeal cough reflex (LCR). On 25 sides of 19 cadaver specimens, the ibSLN and its branches were dissected from the greater cornu of the hyoid to the mucosa of the larynx and laryngopharynx. The location of these terminal fibers were confirmed by direct observation and fiberoptic laryngoscopy. In 21 specimens, the ibSLN coursed 6.95+/-3.71 mm before piercing the thyrohyoid membrane and splitting into superior, middle, and inferior rami. Four specimens split proximal to the thyrohyoid membrane. The superior ramus distributed to the mucosa of the piriform recess. In this study the large, middle ramus was a new finding and distributed branches to the mucosa of the vestibule of the larynx, specifically the quadrangular membrane. The length of the ibSLN from the greater cornu to the end of the middle ramus at quadrangular membrane was 28.52+/-4.61 mm. The termination of these fibers were confirmed by observation and direct laryngoscopy. The middle ramus probably conveyed the afferent component of the laryngeal cough reflex. The inferior ramus did not distribute to the vestibular mucosa.

Assessing the laryngeal cough reflex and the risk of developing pneumonia after stroke.

OBJECTIVE: To determine the effectiveness of a new reflex cough test, using nebulized tartaric acid, in the evaluation of the laryngeal cough reflex and the development of aspiration pneumonia. STUDY DESIGN: In this two-phase study, the cough test assessed the cough reflex in 161 stroke subjects. Phase 1 was a double-blinded prospective study of 40 subjects scheduled to have both modified barium swallow and the reflex cough test. Phase 1 subjects with an abnormal cough test showed an increased pneumonia incidence, and therefore, phase 2 was not blinded. In phase 2, 121 subjects were evaluated using the cough test; 38 received a modified barium swallow. Test results were compared using the Fisher exact test. RESULTS: A total of 131 subjects from both phases had a normal reflex cough test; none developed pneumonia (p < .01). Thirty subjects from both phases had abnormal reflex cough test results; 5 developed pneumonia. Modified barium swallow findings did not reliably indicate the risk for developing pneumonia. Specificity of a normal reflex cough test was 100%. CONCLUSION: The reflex cough test reliably evaluated the laryngeal cough reflex and the associated risk of developing aspiration pneumonia in stroke patients. Testing the laryngeal cough reflex may significantly reduce morbidity, mortality, and costs in stroke patients.

Tartaric acid-induced cough and the superior laryngeal nerve evoked potential.

The purpose of this study was to stimulate the laryngeal cough reflex using a nebulized, mild chemical irritant and to record an associated laryngeal evoked potential from the internal branch of the superior laryngeal nerve. The laryngeal evoked potential was obtained on ten normal subjects from the right internal branch of the superior laryngeal nerve. The electrodiagnostic setup included an active electrode placed just below the hyoid bone with a 4-cm separation and distal reference. A ground electrode was placed between the active and reference electrodes. The receptors and internal branch of the superior laryngeal nerve were stimulated by inhalation of a nebulized 20% solution of tartaric acid and normal saline. The time line was triggered by a pneumatic switch on initial inspiration of the nebulized tartaric acid. The electrodiagnostic settings were set at a sweep speed of 1 ms/division, a gain of 10 to 20 microV/division, and 20 to 2,000 filters. There were 132 variables recorded from the internal branch of the superior laryngeal nerve of the ten subjects. The mean peak distal latency was 1.66+/-0.42 ms with a 1.6 median, 1.6 mode, and 0.17 variance. The duration was 0.41 ms, and amplitude was 5.19+/-2.91 microV. In conclusion, the laryngeal evoked potential, the afferent component of the involuntary cough reflex, can be recorded from the internal branch of the superior laryngeal nerve after inhalation of tartaric acid-induced cough.