Katarina Bodén

Pharyngeal function and airway protection during subhypnotic concentrations of propofol, isoflurane, and sevoflurane: volunteers examined by pharyngeal videoradiography and simultaneous manometry

Background Anesthetic agents alter pharyngeal function with risk of impaired airway protection and aspiration. This study was performed to evaluate pharyngeal function during subhypnotic concentrations of propofol, isoflurane, and sevoflurane and to compare the drugs for possible differences in this respect. Methods Forty-five healthy volunteers were randomized to receive propofol, isoflurane, or sevoflurane. During series of liquid contrast bolus swallowing, fluoroscopy and simultaneous solid state videomanometry was used to study the incidence of pharyngeal dysfunction, the initiation of swallowing, and the bolus transit time. Pressure changes were recorded at the back of the tongue, the pharyngeal constrictor muscles, and the upper esophageal sphincter. After control recordings, the anesthetic was delivered, and measurements were made at 0.50 and 0.25 predicted blood propotol concentration (Cp50asleep) for propofol and 0.50 and 0.25 minimum alveolar concentration (MAC)awake for the inhalational agents. Final recordings were made 20 min after the end of anesthetic delivery. Results All anesthetics caused an increased incidence of pharyngeal dysfunction with laryngeal bolus penetration. Propofol increased the incidence from 8 to 58%, isoflurane from 4 to 36%, and sevoflurane from 6 to 35%. Propofol in 0.50 and 0.25 Cp50asleep had the most extensive effect on the pharyngeal contraction patterns (P < 0.05). The upper esophageal sphincter resting tone was markedly reduced from 83 ± 36 to 39 ± 19 mmHg by propofol (P < 0.001), which differed from isoflurane (P = 0.03). Sevoflurane also reduced the upper esophageal sphincter resting tone from 65 ± 16 to 45 ± 18 mmHg at 0.50 MACawake (P = 0.008). All agents caused a reduced upper esophageal sphincter peak contraction amplitude (P < 0.05), and the reduction was greatest in the propofol group (P = 0.002). Conclusion Subhypnotic concentrations of propofol, isoflurane, and sevoflurane cause an increased incidence of pharyngeal dysfunction with penetration of bolus to the larynx. The effect on the pharyngeal contraction pattern was most pronounced in the propofol group, with markedly reduced contraction forces.

Co-ordination of spontaneous swallowing with respiratory airflow and diaphragmatic and abdominal muscle activity in healthy adult humans

Co‐ordination of breathing and swallowing is essential for normal pharyngeal function and to protect the airway. To allow for safe passage of a bolus through the pharynx, respiration is interrupted (swallowing apnoea); however, the control of airflow and diaphragmatic activity during swallowing and swallowing apnoea are not fully understood. Here, we validated a new airflow discriminator for detection of respiratory airflow and used it together with diaphragmatic and abdominal electromyography (EMG), spirometry and pharyngeal and oesophageal manometry. Co‐ordination of breathing and spontaneous swallowing was examined in six healthy volunteers at rest, during hypercapnia and when breathing at 30 breaths min–1. The airflow discriminator proved highly reliable and enabled us to determine timing of respiratory airflow unambiguously in relation to pharyngeal and diaphragmatic activity. During swallowing apnoea, the passive expiration of the diaphragm was interrupted by static activity, i.e. an ‘active breath holding’, which preserved respiratory volume for expiration after swallowing. Abdominal EMG increased throughout pre‐ and post‐swallowing expiration, more so during hyper‐ than normocapnia, possibly to assist expiratory airflow. In these six volunteers, swallowing was always preceded by expiration, and 93 and 85% of swallows were also followed by expiration in normo‐ and hypercapnia, respectively, indicating that, in man, swallowing during the expiratory phase of breathing may be even more predominant than previously believed. This co‐ordinated pattern of breathing and swallowing potentially reduces the risk for aspiration. Insights from these measurements in healthy volunteers and the airflow discriminator will be used for future studies on airway protection and effects of disease, drugs and ageing.

Effects of three different swallow maneuvers analyzed by videomanometry

Purpose: To evaluate the manometric effects of three different swallow maneuvers on healthy volunteers. Material and Methods: Ten healthy volunteers with no history of swallowing complaints were evaluated with simultaneous videoradiography and pharyngeal manometry (videomanometry). Three different swallow maneuvers were evaluated (supraglottic swallow, super-supraglottic swallow, and Mendelsohns maneuver) and seven manometric and two videoradiographic variables were analyzed. Results: The supraglottic swallow showed a significantly weaker peak contraction of the upper esophageal sphincter (UES). The super-supraglottic swallow had a significantly higher UES relaxation pressure and the Mendelsohn maneuver a significantly higher UES peak contraction. With the Mendelsohn maneuver, there was also a significantly longer duration of the pharyngeal contraction and a significantly weaker UES peak contraction. Both the super-supraglottic and the Mendelsohn maneuver had a significantly longer bolus transit time. Conclusion: Our study did not show any significant difference in the relaxation duration of any of the swallowing maneuvers compared to a control swallow. With the Mendelsohn maneuver, we found that both the pharyngeal peak contraction and contraction duration were increased, which might result in an improved propulsion of bolus into the esophagus.

Pharyngeal Function and Breathing Pattern during Partial Neuromuscular Block in the Elderly: Effects on Airway Protection.

Background:Intact pharyngeal function and coordination of breathing and swallowing are essential for airway protection and to avoid respiratory complications. Postoperative pulmonary complications caused by residual effects of neuromuscular-blocking agents occur more frequently in the elderly. Moreover, elderly have altered pharyngeal function which is associated with increased risk of aspiration. The purpose of this study was to evaluate effects of partial neuromuscular block on pharyngeal function, coordination of breathing and swallowing, and airway protection in individuals older than 65 yr. Methods:Pharyngeal function and coordination of breathing and swallowing were assessed by manometry and videoradiography in 17 volunteers, mean age 73.5 yr. After control recordings, rocuronium was administered to obtain steady-state train-of-four ratios of 0.70 and 0.80 followed by spontaneous recovery to greater than 0.90. Results:Pharyngeal dysfunction increased significantly at train-of-four ratios 0.70 and 0.80 to 67 and 71%, respectively, compared with 37% at control recordings, and swallowing showed a more severe degree of dysfunction during partial neuromuscular block. After recovery to train-of-four ratio of greater than 0.90, pharyngeal dysfunction was not significantly different from the control state. Resting pressure in the upper esophageal sphincter was lower at all levels of partial neuromuscular block compared with control recordings. The authors were unable to demonstrate impaired coordination of breathing and swallowing. Conclusion:Partial neuromuscular block in healthy elderly individuals causes an increased incidence of pharyngeal dysfunction from 37 to 71%, with impaired ability to protect the airway; however, the authors were unable to detect an effect of partial neuromuscular block on coordination of breathing and swallowing.

Swallowing and respiratory pattern in young healthy individuals recorded with high temporal resolution

Abstract  The coordination of swallowing and respiration is essential for a safe swallow. Swallowing consists of several subsecond events. To study this, it is important to use modalities with high temporal resolution. In this study, we have examined young healthy individuals with simultaneous videofluoroscopy, videomanometry and respiratory recording, all with high temporal resolution. The onset of 13 predetermined swallowing and respiratory events and the surrounding respiratory phase pattern were studied in different body positions and during different respiratory drives. An increased respiratory drive was induced by breathing 5% CO2. The results demonstrated a highly repeatable and fixed temporal coordination of the swallowing pattern despite body position and respiratory drive. Previous studies have demonstrated a period of centrally controlled apnoea during swallowing. This apnoea period has a variable length, varying from 1 to 5 s. During increased respiratory drive, we could demonstrate a significantly shorter period of apnoea during swallowing, mainly due to an earlier resumption of respiration. The high temporal recordings in this study have revealed that swallowing during expiration is present basically in all healthy individuals. This swallowing respiratory pattern seems to be appropriate for a safe swallow. This knowledge will be used as a reference for future studies on how swallowing and respiratory coordination might be altered due to ageing and diseases.

Breathing and swallowing in normal man – effects of changes in body position, bolus types, and respiratory drive

Background  Coordination of breathing and swallowing is essential for airway protection and dyscoordination may cause morbidity and mortality.

Effects of Morphine and Midazolam on Pharyngeal Function, Airway Protection, and Coordination of Breathing and Swallowing in Healthy Adults.

Background:Drugs used for sedation in anesthesia and intensive care may cause pharyngeal dysfunction and increased risk for aspiration. In this study, the authors investigate the impact of sedative doses of morphine and midazolam on pharyngeal function during swallowing and coordination of breathing and swallowing. Methods:Pharyngeal function, coordination of breathing and swallowing, and level of sedation were assessed by manometry, videoradiography, measurements of respiratory airflow, and a visual analog scale in 32 healthy volunteers (age 19 to 35 yr). After baseline recordings, morphine (0.1 mg/kg) or midazolam (0.05 mg/kg) was administered intravenously for 20 min, followed by recordings at 10 and 30 min after the end of infusion. Results:Pharyngeal dysfunction, seen as misdirected or incomplete swallowing or penetration of bolus to the airway, increased after morphine infusion to 42 and 44% of swallows compared with 17% in baseline recordings. Midazolam markedly increased incidence of pharyngeal dysfunction from 16 to 48% and 59%. Morphine prolonged apnea before swallowing, and midazolam increased the number of swallows followed by inspiration. Conclusion:Morphine and midazolam in dosages that produce sedation are associated with increased incidence of pharyngeal dysfunction and discoordinated breathing and swallowing, a combination impairing airway protection and potentially increasing the risk for pulmonary aspirations.