Respiratory Inductive Plethysmography Research Articles

Effect of High-Flow Nasal Cannula on Thoraco-Abdominal Synchrony in Pediatric Subjects After Cardiac Surgery.

We previously reported the effects of high-flow nasal cannula (HFNC) oxygen therapy on thoraco-abdominal synchrony. This study was designed to clarify the effect of HFNC on thoraco-abdominal synchrony in pediatric subjects after cardiac surgery and to investigate HFNC optimal flow in this population. Thoraco-abdominal synchrony was evaluated with respiratory inductive plethysmography. After extubation, we delivered oxygen via face mask for 30 min to subjects with mild to moderate respiratory failure. Each subject then randomly received either 1 or 2 L/kg/min via HFNC for 30 min, followed by the other flow level via HFNC for 30 min. After HFNC, face mask delivery was resumed. Rib cage and abdominal movement were converted into volumes and 2 quantitative indexes: maximum compartmental amplitude/tidal volume (VT) ratio and phase angle. Ten subjects of median (interquartile range) age 7 (6-14) months and weighing 6.5 (5.3-8.8) kg were enrolled. Compared with the first delivery via face mask, breathing frequency, maximum compartmental amplitude/VT, phase angle, and minute volume significantly decreased at 2 L/kg/min (P < .05 for all) but not at 1 L/kg/min. PaCO2 did not differ among oxygen therapies. None of the measured variables differed between first and second face mask periods. After cardiac surgery, HFNC oxygen therapy at 2 L/kg/min improved thoraco-abdominal synchrony and decreased breathing frequency in pediatric subjects. (Clinical trial registration: UMIN000023426.).

Voluntary Cough and Clinical Swallow Function in Children with Spastic Cerebral Palsy and Healthy Controls.

Dysphagia and resulting pulmonary sequelae are frequently observed in children with spastic cerebral palsy (SCP). However, physiological evidence regarding airway protective behaviors (specifically swallowing and cough function) in these children is sparse. The aim of this investigation was to quantify specific feeding, swallowing, and cough impairments in children with SCP compared to controls. Eleven children with SCP (mean age: 7 ± 2years; GMFCS: I-V; MACS: I-V) and 10 age-matched controls participated. Clinical feeding and swallowing performance was evaluated with the dysphagia disorder survey (DDS) using standardized liquid, puree, and chewable solid consistencies. Suprahyoid muscle activity and respiratory-swallow patterns were assessed with simultaneous surface electromyography and respiratory inductance plethysmography as children swallowed the various consistencies. Voluntary cough airflow measures were also obtained. Nonparametric tests were used for group comparisons and correlational analyses. Compared to controls, children with SCP demonstrated more signs of clinical feeding and swallowing impairment (p < 0.0001, η2 = 0.771), heightened suprahyoid muscle activity for puree (p = 0.014, η2 = 0.305) and chewable solids (p = 0.001, η2 = 0.528), more frequent post-swallow inhalation across liquid (p = 0.005, η2 = 0.401), puree (p = 0.014, η2 = 0.304), and chewable solids (p = 0.035, η2 = 0.223), and lower cough volume acceleration (p = 0.019, η2 = 0.289). Post-swallow inhalation for chewable solids was correlated with the DDS Part 1 (rs = 0.734, p = 0.010), DDS Part 2 (rs = 0.610, p = 0.046) and the DDS Total scores (rs = 0.673, p = 0.023). This study is the first to provide evidence of specific physiological deficits of both swallowing and voluntary cough in children with SCP. Potential hypotheses explaining these deficits and implications for physiologically driven management are explored.

Quantitative Analysis of Thoracoabdominal Asynchrony in Pediatric Polysomnography.

Objective measurements of thoracoabdominal asynchrony (TAA), such as average phase angle (θavg), can quantify airway obstruction. This study demonstrates and evaluates use of θavg for predicting obstructive sleep apnea (OSA) in pediatric polysomnography (PSG). This prospective observational study recruited otherwise healthy 3- to 8-year-old children presenting for PSG due to snoring, behavioral problems, difficulty sleeping, and/or enlarged tonsils. Respiratory inductance plethysmography (RIP) was directly monitored and data were collected during each PSG. θavg and average labored breathing index (LBIavg) were calculated for earliest acceptable 5-minute periods of stage N3 sleep and stage R sleep. Associations between θavg and obstructive apnea index (OAI) and obstructive apnea-hypopnea index (OAHI), as well as between LBIavg and OAI and OAHI, were examined. Forty patients undergoing PSG were analyzed. Thirty percent of patients had OSA, 57.5% had enlarged tonsils, and 17.5% were obese. θavg during stage N3 sleep and stage R sleep had significant positive correlations with OAI (Spearman r = .35 [P = .03] and .40 [P = .01], respectively) and θavg during stage N3 sleep with OAHI (r = .35 [P = .03]). LBIavg showed lower correlations. Median θavg during stage R sleep (33.1) was significantly greater than during stage N3 sleep (13.7, P = .0005). Association of θavg with OAI and OAHI shows that θavg reflects airway obstruction and has potential use as a quantitative indicator of OSA. RIP provides valuable information that is readily available in PSG. The significant difference between θavg in stage N3 sleep and stage R sleep confirms the clinical observation that there is more asynchrony during rapid eye movement sleep than non-rapid eye movement sleep.

Measures of respiratory inductance plethysmography (RIP) in children with neuromuscular disease.

Pulmonary function testing (PFT) is essential for the clinical assessment of respiratory problems. Respiratory inductance plethysmography (RIP) is a non-invasive method of PFT requiring minimal patient cooperation. RIP measures the volumetric change in the ribcage and abdomen, from which work of breathing (WOB) indices are derived. WOB indices include: phase angle (Ф), percent ribcage (RC%), respiratory rate (RR), and labored breathing index (LBI). Heart rate (HR) is collected separately. The goal of this study was to assess the utility of a newly developed RIP system, the pneuRIP, in an outpatient clinic setting in children with neuromuscular (NM) disease. The pneuRIP system measures and displays the WOB indices in real-time on an iPad display. Forty-three subjects, 22 NM patients and 21 healthy children (ages: 5-18 years) were enrolled. Patients' means showed an increase of 119.8% for Ф, 15.7% for LBI, and 19.9% for HR compared with healthy subjects, when adjusted for age and gender. The study found significant differences between the mean values of the healthy subjects and patients in Ф (P = 0.000), LBI (P = 0.001), and HR (P = 0.001). No differences were noted for RC% and RR between groups. Data for Ф in NM patients were diffusely distributed as compared with healthy subjects based on analysis of histograms. Non-invasive pneuRIP testing provided instantaneous PFT results. As compared to healthy subjects, NM patients showed abnormal results with increased markers of thoracoabdominal asynchrony, WOB indices, and biphasic breathing patterns likely resulting from NM weakness.

Tolerability of a comprehensive cardiorespiratory monitoring protocol in an epilepsy monitoring unit

BackgroundRecent reports of fatal or near-fatal events in epilepsy monitoring units (EMUs) and an increasing awareness of the effects of seizures on breathing have stimulated interest in cardiorespiratory monitoring for patients undergoing video-electroencephalography (EEG) recording. Patient and provider acceptance of these extra recording devices has not previously been studied and may represent a barrier to widespread adoption. MethodsWe queried EMU subjects regarding their experiences with a monitoring protocol that included the continuous measurement of oral/nasal airflow, respiratory effort (chest and abdominal respiratory inductance plethysmography), oxygen saturation, and transcutaneous CO2. Surveys were returned by 71.4% (100/140) of eligible subjects. ResultsOverall, 73% of participants reported being moderately to highly satisfied with the monitoring, and 82% reported moderate to strong agreement that advance knowledge of the monitoring would not have changed their decision to proceed with the video-EEG study. Except for nasal airflow, none of the additional monitoring devices caused more discomfort than EEG electrodes. ConclusionPatient acceptance of an EMU comprehensive cardiorespiratory monitoring protocol is high. The information obtained from “multimodality recording” should help clinicians and investigators understand the effect of seizures on both cardiac and respiratory physiology, may enhance safety in the EMU, and may aid in the identification of biomarkers for sudden unexpected death in epilepsy (SUDEP).

CON: Persistent Central Sleep Apnea/Hunter-Cheyne-Stokes Breathing, Despite Best Guideline-Based Therapy of Heart Failure With Reduced Ejection Fraction, Is Not a Compensatory Mechanism and Should Be Suppressed.

CON: Persistent Central Sleep Apnea/Hunter-Cheyne-Stokes Breathing, Despite Best Guideline-Based Therapy of Heart Failure With Reduced Ejection Fraction, Is Not a Compensatory Mechanism and Should Be Suppressed.

Characterization of Respiratory Events in Obstructive Sleep Apnea Using Suprasternal Pressure Monitoring.

In obstructive sleep apnea (OSA) esophageal pressure (Pes) is the gold standard for measurement of respiratory effort, and respiratory inductance plethysmography (RIP) is considered an accepted measurement technique. However, the use of RIP could lead to limited accuracy in certain cases and therefore suprasternal pressure (SSP) monitoring might improve the reliability of OSA diagnosis. We aimed to use SSP for the visual characterization of respiratory events in adults and compared results to those obtained by RIP from polysomnography (PSG). In patients with OSA, a 1-night SSP recording using the PneaVoX sensor (Cidelec, Sainte-Gemmes-sur-Loire, France) was done. In parallel, PSG was performed according to American Academy of Sleep Medicine criteria. A subgroup of patients agreed to have Pes measurement in addition. Characterizations of apneas as obstructive, central, and mixed as well as hypopneas as central and obstructive were done by visual evaluation of SSP, RIP, and Pes in random order by two independent scores (S1 and S2). The sensitivity and specificity of characterization by SSP compared to RIP and to Pes were calculated. Synchronous recordings of SSP and PSG were analyzed from n = 34 patients with OSA (AHI 34.1 ± 24.2 events/h); 9 of them had synchronized Pes monitoring as well. Interscorer agreement for apnea characterization as obstructive, central, and mixed based on SSP, RIP, and Pes were found, with R2 values from 0.91-0.99. The sensitivity of SSP in apnea characterization with reference to RIP (S1/S2) was 91.5%/92.3% for obstructive, 82.7%/76.2% for central, and 87.4%/79.9% for mixed. The sensitivity of SSP in apnea characterization with reference to Pes was (S1/S2) 93.1%/92.1% for obstructive, 80.8%/81.6% for central, and 91.7%/90.8% for mixed. Hypopnea was only classified for the nine patients with Pes. This study demonstrated a good agreement in the detection of respiratory effort with the SSP signal using the PneaVoX sensor compared to the RIP belts signals as well as to the Pes signal. These findings were consistently found by two independent scorers. In summary, results suggest that SSP is a reliable signal for the classification of respiratory events and could be used as an additional tool for OSA characterization in clinical practice.

Development and validation of an algorithm for the study of sleep using a biometric shirt in young healthy adults.

Portable polysomnography is often too complex and encumbering for recording sleep at home. We recorded sleep using a biometric shirt (electrocardiogram sensors, respiratory inductance plethysmography bands and an accelerometer) in 21 healthy young adults recorded in a sleep laboratory for two consecutive nights, together with standard polysomnography. Polysomnographic recordings were scored using standard methods. An algorithm was developed to classify the biometric shirt recordings into rapid eye movement sleep, non-rapid eye movement sleep and wake. The algorithm was based on breathing rate and heart rate variability, body movement, and included a correction for sleep onset and offset. The overall mean percentage of agreement between the two sets of recordings was 77.4%; when non-rapid eye movement and rapid eye movement sleep epochs were grouped together, it increased to 90.8%. The overall kappa coefficient was 0.53. Five of the seven sleep variables were significantly correlated. The findings of this pilot study indicate that this simple portable system could be used to estimate the general sleep pattern of young healthy adults.

Towards estimation of respiratory muscle effort with respiratory inductance plethysmography signals and complementary ensemble empirical mode decomposition

Respiratory inductance plethysmography (RIP) sensor is an inexpensive, non-invasive, easy-to-use transducer for collecting respiratory movement data. Studies have reported that the RIP signal's amplitude and frequency can be used to discriminate respiratory diseases. However, with the conventional approach of RIP data analysis, respiratory muscle effort cannot be estimated. In this paper, the estimation of the respiratory muscle effort through RIP signal was proposed. A complementary ensemble empirical mode decomposition method was used, to extract hidden signals from the RIP signals based on the frequency bands of the activities of different respiratory muscles. To validate the proposed method, an experiment to collect subjects' RIP signal under thoracic breathing (TB) and abdominal breathing (AB) was conducted. The experimental results for both the TB and AB indicate that the proposed method can be used to loosely estimate the activities of thoracic muscles, abdominal muscles, and diaphragm. Graphical abstract ᅟ.

Apnea characterization by means of suprasternal pressure, respiratory inductance plethysmography and oesophageal pressure: a comparative study

Apnea characterization by means of suprasternal pressure, respiratory inductance plethysmography and oesophageal pressure: a comparative study

Classifying Apnea of Prematurity by Transcutaneous Electromyography of the Diaphragm

Background: Treatment of apnea is highly dependent on the type of apnea. Chest impedance (CI) has inaccuracies in monitoring respiration, which compromises accurate apnea classification. Electrical activity of the diaphragm measured by transcutaneous electromyography (EMG) is feasible in preterm infants and might improve the accuracy of apnea classification. Objectives: To compare the accuracy of apnea classification based on diaphragmatic EMG (dEMG) and CI tracings in preterm infants. Methods: Fifteen cases of central apnea, 5 of obstructive apnea, and 10 of mixed apnea were selected from recordings containing synchronized continuous tracings of respiratory inductive plethysmography (RIP), airway flow, heart rate (HR), oxygen saturation (SpO₂), and breathing activity measured by dEMG and CI. Twenty-two assessors (neonatologists, pediatricians-in-training, and nurses) classified each apnea twice; once based on dEMG, HR, and SpO₂ tracings, and once based on CI, HR, and SpO₂. The assessors were blinded to the type of respiratory tracing (dEMG or CI) and to the RIP and flow tracings. Results: In total 1,320 assessments were performed, and in 71.1% the apnea was classified correctly. Subgroup analysis based on respiratory tracing showed that 74.8% of the dEMG tracings were classified correctly compared to 67.3% of the CI tracings (p < 0.001). This improved apnea classification based on dEMG was present for central (86.7 vs. 80.3%, p < 0.02) and obstructive (56.4 vs. 32.7%, p < 0.001) apnea. The improved apnea classification based on dEMG tracing was independent of the type of assessor. Conclusion: Transcutaneous dEMG improves the accuracy of apnea classification when compared to CI in preterm infants, making this technique a promising candidate for future monitoring systems.

Development of a Multisensory Wearable System for Monitoring Cigarette Smoking Behavior in Free-Living Conditions.

This paper presents the development and validation of a novel multi-sensory wearable system (Personal Automatic Cigarette Tracker v2 or PACT2.0) for monitoring of cigarette smoking in free-living conditions. The contributions of the PACT2.0 system are: (1) the implementation of a complete sensor suite for monitoring of all major behavioral manifestations of cigarette smoking (lighting events, hand-to-mouth gestures, and smoke inhalations); (2) a miniaturization of the sensor hardware to enable its applicability in naturalistic settings; and (3) an introduction of new sensor modalities that may provide additional insight into smoking behavior e.g., Global Positioning System (GPS), pedometer and Electrocardiogram(ECG) or provide an easy-to-use alternative (e.g., bio-impedance respiration sensor) to traditional sensors. PACT2.0 consists of three custom-built devices: an instrumented lighter, a hand module, and a chest module. The instrumented lighter is capable of recording the time and duration of all lighting events. The hand module integrates Inertial Measurement Unit (IMU) and a Radio Frequency (RF) transmitter to track the hand-to-mouth gestures. The module also operates as a pedometer. The chest module monitors the breathing (smoke inhalation) patterns (inductive and bio-impedance respiratory sensors), cardiac activity (ECG sensor), chest movement (three-axis accelerometer), hand-to-mouth proximity (RF receiver), and captures the geo-position of the subject (GPS receiver). The accuracy of PACT2.0 sensors was evaluated in bench tests and laboratory experiments. Use of PACT2.0 for data collection in the community was validated in a 24 h study on 40 smokers. Of 943 h of recorded data, 98.6% of the data was found usable for computer analysis. The recorded information included 549 lighting events, 522/504 consumed cigarettes (from lighter data/self-registered data, respectively), 20,158/22,207 hand-to-mouth gestures (from hand IMU/proximity sensor, respectively) and 114,217/112,175 breaths (from the respiratory inductive plethysmograph (RIP)/bio-impedance sensor, respectively). The proposed system scored 8.3 ± 0.31 out of 10 on a post-study acceptability survey. The results suggest that PACT2.0 presents a reliable platform for studying of smoking behavior at the community level.

Distinct Patterns of Hyperpnea During Cheyne-Stokes Respiration: Implication for Cardiac Function in Patients With Heart Failure.

In heart failure (HF), we observed two patterns of hyperpnea during Cheyne-Stokes respiration with central sleep apnea (CSR-CSA): a positive pattern where end-expiratory lung volume remains at or above functional residual capacity, and a negative pattern where it falls below functional residual capacity. We hypothesized the negative pattern is associated with worse HF. Patients with HF underwent polysomnography. During CSR-CSA, hyperpnea, apnea-hyperpnea cycle, and lung to finger circulation times (LFCT) were measured. Plasma N-terminal prohormone of brain natriuretic peptide (NT-proBNP) concentration and left ventricular ejection fraction (LVEF) were assessed. Of 33 patients with CSR-CSA (31 men, mean age 68 years), 9 had a negative hyperpnea pattern. There was no difference in age, body mass index, and apnea-hypopnea index between groups. Patients with a negative pattern had longer hyperpnea time (39.5 ± 6.4 versus 25.8 ± 5.9 seconds, P < .01), longer cycle time (67.8 ± 15.9 versus 51.7 ± 9.9 seconds, P < .01), higher NT-proBNP concentrations (2740 [6769] versus 570 [864] pg/ml, P = .01), and worse New York Heart Association class (P = .02) than those with a positive pattern. LFCT and LVEF did not differ between groups. Patients with HF and a negative CSR-CSA pattern have evidence of worse cardiac function than those with a positive pattern. Greater positive expiratory pressure during hyperpnea is likely generated during the negative pattern and might support stroke volume in patients with worse cardiac function. A commentary on this article appears in this issue on page 1227. The trial is registered with Current Controlled Trials (www.controlled-trials.com; ISRCTN67500535) and Clinical Trials (www.clinicaltrials.gov; NCT01128816).

Breath detection by transcutaneous electromyography of the diaphragm and the Graseby capsule in preterm infants.

To compare triggering, breath detection and delay time of the Graseby capsule (GC) and transcutaneous electromyography of the diaphragm (dEMG) in spontaneous breathing preterm infants. In this observational study, a 30 minutes respiration measurement was conducted by respiratory inductance plethysmography (RIP), the GC, and dEMG in stable preterm infants. Triggering was investigated with an in vitro set-up using the Infant Flow® SiPAPTM system. The possibility to optimize breath detection was tested by developing new algorithms with the abdominal RIP band (RIPAB ) as gold standard. In a subset of breaths, the delay time was calculated between the inspiratory onset in the RIPAB signal and in the GC and dEMG signal. Fifteen preterm infants with a mean gestational age of 28 ± 2 weeks and a mean birth weight of 1086 ± 317 g were included. In total, 14 773 breaths were analyzed. Based on the GC and dEMG signal, the Infant Flow® SiPAP™ system, respectively, triggered 67.8% and 62.6% of the breaths. Breath detection was improved to 99.9% for the GC and 113.4% for dEMG in new algorithms. In 1492 stable breaths, the median delay time of inspiratory onset detection was +154 ms (IQR +118 to +164) in the GC and -50 ms (IQR -90 to -22) in the dEMG signal. Breath detection using the GC can be improved by optimizing the algorithm. Transcutaneous dEMG provides similar breath detection but with the advantage of detecting the onset of inspiration earlier than the GC.

3D detection of the central sleep apnoea syndrome

Abstract In polysomnography, an oronasal thermal airflow sensor and respiratory inductance plethysmography (RIP) belts at thorax and abdomen are used to detect central sleep apnoea. These sensors are uncomfortable to wear, can disturb the patient’s sleep, and data quality can be significantly di-minished if a sensor slips off the patient. Contactless meas-urements would be a desirable alternative. We utilized a 3D time-of-flight sensor to monitor respiratory-related chest movements to decipher epochs of normal breathing and ap-noea in ten adult patients with a total of 467 apnoea events. Time-synchronized comparisons of 3D measurements of chest movements due to respiration to polysomnography signals from rip belts and nasal airflow proved that the 3D sensor provided largely equivalent results. This new tech-nique could support the diagnosis of central sleep apnoea and Cheyne-Stokes respiration.

The Impact of Glottal Configuration on Speech Breathing

The purpose of this study was to examine whether changes in respiratory patterns occurred in response to volitional changes in glottal configuration. Twelve vocally healthy participants read a passage while wearing the Inductotrace respiratory inductive plethysmograph, which measures the excursions of the rib cage and abdomen. Participants read the passage 5 times in a typical speaking voice (baseline phase), 10 times in an experimental voice, which was similar to a breathy vocal quality (experimental phase), and 5 times again in a typical speaking voice (return phase). Kinematic estimates of lung volume (LV) initiation, LV termination, and LV excursion were collected for each speech breath. Participants spoke with larger LV excursions during the experimental phase, characterized by increased LV initiation and decreased LV termination compared with the baseline phase. In response to volitional changes in glottal configuration, healthy individuals spoke with increased LV excursion. They both responded to changes (decreasing LV termination) and planned for more efficient future utterances (increasing LV initiation) during the experimental phase. This study demonstrated that respiratory patterns change in response to changes in glottal configuration; future work will examine these patterns in individuals with voice disorders.

Maturation Modulates Pharyngeal-Stimulus Provoked Pharyngeal and Respiratory Rhythms in Human Infants.

Pharyngeal-provocation induced aerodigestive symptoms in infants remain an enigma. Sources of pharyngeal provocation can be anterograde as with feeding, and retrograde as in gastroesophageal reflux. We determined maturational and dose-response effects of targeted pharyngeal-stimulus on frequency, stability, and magnitude of pharyngeal and respiratory waveforms during multiple pharyngeal swallowing responses in preterm-born infants when they were of full-term postmenstrual age (PMA). Eighteen infants (11 male) were studied longitudinally at 39.8±4.8 weeks PMA (time-1) and 44.1±5.8 weeks PMA (time-2). Infants underwent concurrent pharyngo-esophageal manometry, respiratory inductance plethysmography, and nasal airflow thermistor methods to test sensory-motor interactions between the pharynx, esophagus, and airway. Linear mixed models were used and data presented as mean±SEM or %. Overall, responses to 250 stimuli were analyzed. Of the multiple pharyngeal swallowing responses (n=160), with maturation (a) deglutition apnea duration decreases (p<0.01), (b) number of pharyngeal waveform peaks and duration decreases for initial responses (p<0.01), and subsequent responses have lesser variation and greater stability (p<0.01). With increment in stimulus volumes we noted (a) increased prevalence (%) of pharyngeal responses (p<0.05), (b) increased number of pharyngeal peaks (p<0.05), yet pharyngeal frequency (Hz), variability, and stability remain unaffected (p>0.05), and (c) respiratory changes were unaffected (p>0.05). Initial and subsequent pharyngeal responses and respiratory rhythm interactions become more distinct with maturation. Interval oromotor experiences and volume-dependent increase in adaptive responses may be contributory. These mechanisms may be important in modulating and restoring respiratory rhythm normalcy.

The Impact of Deep Muscle Training on the Quality of Posture and Breathing

ABSTRACTPostural control and breathing are mechanically and neuromuscularly interdependent. Both systems– of spinal stability and respiration– involve the diaphragm, transversus abdominis, intercostal muscles, internal oblique muscles and pelvic floor muscles. The aim of the study was to evaluate the effect of exercises activating deep stabilizer muscles on postural control and quality of breathing movements. Eighteen volunteers (25,7 ± 3,5) were recruited from the general population. All the subjects implemented an exercise program activating deep muscles. Head, pelvic and trunk positions in the sagittal and frontal planes were assessed with the photogrammetric method. Breathing movements were estimated with the respiratory inductive plethysmography. The results indicate that the use of deep muscle training contributed to a significant change in the position of the body in the sagittal plane (p = 0.008) and the increase in the amplitude of breathing (p = 0.001).

Risk Factors for Pediatric Extubation Failure: The Importance of Respiratory Muscle Strength.

Respiratory muscle weakness frequently develops during mechanical ventilation, although in children there are limited data about its prevalence and whether it is associated with extubation outcomes. We sought to identify risk factors for pediatric extubation failure, with specific attention to respiratory muscle strength. Secondary analysis of prospectively collected data. Tertiary care PICU. Four hundred nine mechanically ventilated children. Respiratory measurements using esophageal manometry and respiratory inductance plethysmography were made preextubation during airway occlusion and on continuous positive airway pressure of 5 and pressure support of 10 above positive end-expiratory pressure 5 cm H2O, as well as 5 and 60 minutes postextubation. Thirty-four patients (8.3%) were reintubated within 48 hours of extubation. Reintubation risk factors included lower maximum airway pressure during airway occlusion (aPiMax) preextubation, longer length of ventilation, postextubation upper airway obstruction, high respiratory effort postextubation (pressure rate product, pressure time product, tension time index), and high postextubation phase angle. Nearly 35% of children had diminished respiratory muscle strength (aPiMax ≤ 30 cm H2O) at the time of extubation, and were nearly three times more likely to be reintubated than those with preserved strength (aPiMax > 30 cm H2O; 14% vs 5.5%; p = 0.006). Reintubation rates exceeded 20% when children with low aPiMax had moderately elevated effort after extubation (pressure rate product > 500), whereas children with preserved aPiMax had reintubation rates greater than 20% only when postextubation effort was very high (pressure rate product > 1,000). When children developed postextubation upper airway obstruction, reintubation rates were 47.4% for those with low aPiMax compared to 15.4% for those with preserved aPiMax (p = 0.02). Multivariable risk factors for reintubation included acute neurologic disease, lower aPiMax, postextubation upper airway obstruction, higher preextubation positive end-expiratory pressure, higher postextubation pressure rate product, and lower height. Neuromuscular weakness at the time of extubation was common in children and was independently associated with reintubation, particularly when postextubation effort was high.

Defining a Ventilation Strategy for Flexible Bronchoscopy on Mechanically Ventilated Patients in the Medical Intensive Care Unit

Flexible bronchoscopy (FB) in intubated patients on mechanical ventilation increases airway resistance. During FB, two ventilatory strategies are possible: maintaining tidal volume (VT) while maintaining baseline CO2 or allowing reduction of VT. The former strategy carries risk of hyperinflation due to expiratory flow limitation with FB. The aim of the authors was too study end expiratory lung volume (EELV) during FB of intubated subjects while limiting VT. We studied 16 subjects who were intubated on mechanical ventilation and required FB. Changes in EELV were measured by respiratory inductance plethysmography. Ventilator mechanics, EELV, and arterial blood gases, were measured. FB insertions decreased EELV in 64% of cases (-325±371 mL) and increased it in 32% of cases (65±59 mL). Suctioning decreased EELV in 76% of cases (-120±104 mL) and increased it in 16% of cases (29±33 mL). Respiratory mechanics were unchanged. Pre-FB and post-FB, PaO2 decreased by 61±96 mm Hg and PaCO2 increased by 15±7 mm Hg. There was no clinically significant increase in EELV in any subject during FB. Decreases in EELV coincided with FB-suctioning maneuvers. Peak pressure limiting ventilation protected the subject against hyperinflation with a consequent, well-tolerated reduction in VT, and hypercapnea. Suctioning should be limited, especially in patients vulnerable to derecruitment effect.