Reproducibility of twitch and sniff transdiaphragmatic pressures

doi:10.1016/S1569-9048(02)00115-5

Respiratory Physiology & Neurobiology

Volume 132, Issue 3, 4 September 2002, Pages 301-306

https://doi.org/10.1016/S1569-9048(02)00115-5 Get rights and content

Abstract

Twitch transdiaphragmatic pressure (Tw Pdi) measured with magnetic stimulation of the phrenic nerve is used to follow up patients and to assess the effect of clinical treatments on diaphragm function. However the reproducibility of Tw Pdi on different occasions has been little studied. We investigated 32 normal subjects, measuring Tw Pdi elicited by bilateral magnetic stimulation of the phrenic nerves on two to 14 occasions. Sniff transdiaphragmatic pressure (sniff Pdi) was also measured. The mean value of Tw Pdi and sniff Pdi were 28±5 and 134±24 cm H₂O, respectively. The within subjects coefficient of variation was 11% for both Tw Pdi and sniff Pdi. We conclude that there is a variability of Tw Pdi and the variability of Tw Pdi is the same as that of sniff Pdi.

Introduction

Transdiaphragmatic pressure elicited by phrenic nerve stimulation (Tw Pdi) is a non-volitional test and is considered to be a sensitive and reliable technique for assessment of diaphragm function (NHLBI Workshop summary, 1990, Polkey et al., 1995). Tw Pdi has been frequently used to assess diaphragm strength (Aubier et al., 1985, Mier et al., 1989, Similowski et al., 1989) and detect diaphragm fatigue (Hamnegard et al., 1996, Mador et al., 1996, Luo et al., 2001). Recently, Tw Pdi has been used to evaluate the effect of clinical treatments and respiratory muscle training. For example, the effect of lung volume reduction surgery on diaphragm function has been assessed by measuring Tw Pdi before and 3 or 6 months after operation (Criner et al., 1998, Laghi et al., 1998). However, accurate assessment of diaphragm function requires good reproducibility of Tw Pdi not only within occasion but also between occasions. Many studies have shown that Tw Pdi elicited by magnetic stimulation of the phrenic nerves has good reproducibility within occasion (Mador et al., 1996, Criner et al., 1999) but reproducibility between occasions has not been systematically investigated.

Sniff Pdi (Miller et al., 1985) is also often used to assess diaphragm function and to follow up patients. Although it is assumed that Tw Pdi, a non-volitional test, is likely to be more reproducible than Sniff Pdi (Polkey et al., 1995), no study has assessed this. In the present study we investigated repeatability of Tw Pdi and sniff Pdi to determine whether Tw Pdi was more reproducible than sniff Pdi.

Section snippets

Subjects

The results from 32 healthy volunteers studied in our laboratory constitute the data for this study. Most of the subjects were staff of the respiratory muscle laboratories at King's College Hospital or Brompton Hospital. No subject had neuromuscular or respiratory disease. The study was approved by the ethics committee of King's College Hospital and all subjects gave their informed consent.

Bilateral anterolateral magnetic stimulation of the phrenic nerves (BAMPS)

BAMPS was performed using two 43 mm figures of eight coils powered by Magstim 200 stimulators (Magstim,

Result

Reproducibility of Tw Pdi is summarised in Table 1. The mean Tw Pdi for all subjects was 28±5 cm H₂O with a range of 18–42 cm H₂O for all individual occasions. The maximal change of Tw Pdi between occasions was up to 41%. The mean sniff Pdi was 134±24 cm H₂O with a range of 86–195 cm H₂O. The maximal change of sniff Pdi between occasions was up to 40%. The within subjects coefficient of variation was the same for both Tw Pdi and sniff Pdi and was 11%. The agreement in Tw Pdi and sniff Pdi

Discussion

In the present study we found that twitch Pdi and sniff Pdi have similar variability between occasions. Previous investigators have studied the reproducibility of Tw Pdi elicited by electrical stimulation (Aubier et al., 1985, Mier et al., 1989, Eastwood et al., 1995, Mills et al., 1995). It is difficult for electric stimulation to maximally activate the phrenic nerve (Bellemare and Bigland-Ritchie, 1987, Laghi et al., 1996). Furthermore, twitch potentiation can increase twitch Pdi (Wragg et

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2020, Contemporary Clinical Trials
Citation Excerpt :
This provides a measure of diaphragm strength, although the stimulation is not sufficient for maximal activation and therefore is not directly measuring PiMax [23,29]. Although twitch stimulation has been applied in a limited capacity in young children, it has high variability and limited reproducibility [30–35]. The measurement of PiMax can provide insight into respiratory muscle function.
Lung Protective Mechanical Ventilation (MV) of critically ill adults and children is lifesaving but it may decrease diaphragm contraction and promote Ventilator Induced Diaphragm Dysfunction (VIDD). An ideal MV strategy would balance lung and diaphragm protection. Building off a Phase I pilot study, we are conducting a Phase II controlled clinical trial that seeks to understand the evolution of VIDD in critically ill children and test whether a novel computer-based approach (Real-time Effort Driven ventilator management (REDvent)) can balance lung and diaphragm protective ventilation to reduce time on MV. REDvent systematically adjusts PEEP, FiO₂, inspiratory pressure, tidal volume and rate, and uses real-time measures from esophageal manometry to target normal levels of patient effort of breathing. This trial targets 276 children with pulmonary parenchymal disease. Patients are randomized to REDvent vs. usual care for the acute phase of MV (intubation to first Spontaneous Breathing Trial (SBT)). Patients in either group who fail their first SBT will be randomized to REDvent vs usual care for weaning phase management (interval from first SBT to passing SBT). The primary clinical outcome is length of weaning, with several mechanistic outcomes. Upon completion, this study will provide important information on the pathogenesis and timing of VIDD during MV in children and whether this computerized protocol targeting lung and diaphragm protection can lead to improvement in intermediate clinical outcomes. This will form the basis for a larger, Phase III multi-center study, powered for key clinical outcomes such as 28-day ventilator free days.
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Transdiapragmatic pressure and contractile properties of the diaphragm following magnetic stimulation
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Twitch Pdi following CEMS provides non-volitional measures of diaphragm strength and fatigue which can be monitored during patient follow-up (Gibson et al., 2002). Several studies applied twPdi recordings, mostly after CEMS of the phrenic nerves in small cohorts, (Similowski et al., 1989; Wragg et al., 1994a; Mier et al., 1989a; Luo et al., 2002) and transcranial, or cortical, MS (COMS) of the diaphragm has also been utilised. Resulting electrical muscle activity can be recorded bilaterally using surface electrodes placed at the lower costal margins, referred to as diaphragm motor evoked potentials following COMS, and diaphragm compound muscle action potentials following CEMS.
Insufficient normal values exist regarding twitch transdiaphragmatic pressure (twPdi) derived from standardized cervical and cortical magnetic stimulation (MS) of the diaphragm.
Therefore, 63 subjects (24 men, 39 women; 34 ± 13 years) underwent transcortical and posterior cervical MS of the diaphragm with simultaneous recording of twitch oesophageal and gastric pressures (twPes, twPgas).
Following cortical MS at functional residual capacity, twPdi amplitudes showed high intra-individual variability which was markedly reduced when an inspiratory pressure trigger was applied. Lower limit of the 95% confidence interval computed around the mean value (LLN) was 12 cmH₂O, independent of gender or age. Following cervical MS of the phrenic nerves, twPdi amplitudes were well reproducible and unaffected by gender, but age-dependent (age 18–30: LLN 23 cmH₂O; age ≥ 30: LLN 16 cmH₂O; p < 0.05).
The inspiratory pathway can be assessed using cervical MS of the phrenic nerves. If transcranial motor cortex stimulation of the diaphragm is also applied, a standardized inspiratory pressure trigger is recommended. Dynamics of diaphragm contraction appear to be age-dependent.
Diaphragm Dysfunction in Critical Illness
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The diaphragm is the major muscle of inspiration, and its function is critical for optimal respiration. Diaphragmatic failure has long been recognized as a major contributor to death in a variety of systemic neuromuscular disorders. More recently, it is increasingly apparent that diaphragm dysfunction is present in a high percentage of critically ill patients and is associated with increased morbidity and mortality. In these patients, diaphragm weakness is thought to develop from disuse secondary to ventilator-induced diaphragm inactivity and as a consequence of the effects of systemic inflammation, including sepsis. This form of critical illness-acquired diaphragm dysfunction impairs the ability of the respiratory pump to compensate for an increased respiratory workload due to lung injury and fluid overload, leading to sustained respiratory failure and death. This review examines the presentation, causes, consequences, diagnosis, and treatment of disorders that result in acquired diaphragm dysfunction during critical illness.
Maximal Inspiratory Pressure: Does the Choice of Reference Values Actually Matter?
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Citation Excerpt :
As mentioned, results were interpreted while taking into consideration robust clinical and physiologic predictors of weakness.3,18,21,22 However, we acknowledge that the lack of criterion tests of nonvolitional strength30,32 precluded any inference regarding the diagnostic accuracy of individual reference values. It should also be recognized that MIP tends to overdiagnose weakness and combination of tests increase diagnostic precision.
Single-point measurements of maximal inspiratory pressure (MIP) are frequently used to suggest muscle weakness in clinical practice. Although there is a large variability in “mean” predicted MIP depending on the chosen reference values, it remains unclear whether those discrepancies actually impact on the prevalence of weakness, that is, MIP below the lower limit of normal.
A total of 1,729 subjects (50.1% men, aged 20 to 94 years) who underwent MIP measurements in a clinical laboratory comprised the study group. MIP was predicted according to the most frequently cited regression equations as of August 2015. Pretest probability of weakness was defined by a cluster of clinical and physiologic variables.
Prevalence of weakness ranged from 33.4 to 66.9%. Set 2 equations agreed well in indicating weakness (κ [95% CI] ranging from 0.81 [0.79-0.83] to 0.83 [0.81-0.85]; P < .01). There was closer agreement between higher pretest probability of weakness and low MIP according to set 2 equations compared with set 1 equations. Thus, a significant fraction of subjects with abnormal MIP according to set 1 equations but preserved MIP according to set 2 equations had higher pretest probability of weakness (P < .05).
The choice of MIP reference values strongly impacts on the prevalence of weakness. Some specific equations relate better to clinical and physiologic indicators of weakness, suggesting that they might be particularly useful to screen subjects for advanced respiratory neuromuscular assessment.
Evaluation of an early exercise intervention after thoracotomy for non-small cell lung cancer (NSCLC), effects on quality of life, muscle strength and exercise tolerance: Randomised controlled trial
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Deterioration in exercise tolerance and impairment in quality of life (QoL) are common consequences of lobectomy. This study evaluates additional exercise and strength training after lung resection on QoL, exercise tolerance and muscle strength. Fifty-three (28 male) patients attending thoracotomy for lung cancer, mean age, range 64 (32–82) years; mean pack years (SD) 31.9 (26.8); BMI 25.6 (4.2); FEV1 2.0 (0.7) l were randomised to control (usual care) or intervention (twice daily training plus usual care). After discharge the intervention group received monthly home visits and weekly telephone calls, the control group received monthly telephone calls up to 12 weeks. Assessment pre-operatively, 5 day and 12 weeks post-operatively consisted of quadriceps strength using magnetic stimulation, 6 Minute Walking Distance (6MWD) and QoL-EORTC-QLQ-LC13. QoL was unchanged over 12 weeks; 6MWD showed significant deterioration at 5 days post-operatively compared with pre-operatively, mean difference (SD)−131.6 (101.8) m and −128.0 (90.7) m in active and control groups respectively (p = 0.89 between groups) which returned to pre-operative levels by 12 weeks in both groups. Quadriceps strength over the 5 day in-patient period showed a decrease of −8.3 (11.3) kg in the control group compared to increase of 4.0 (21.2) kg in the intervention group (p = 0.04 between groups). Strength training after thoracotomy successfully prevented the fall in quadriceps strength seen in controls, however, there was no effect on 6MWD or QoL. 6MWD returned to pre-operative levels by 12 weeks regardless of additional support offered.
Neural drive during continuous positive airway pressure (CPAP) and pressure relief CPAP
2009, Sleep Medicine
Citation Excerpt :
The diaphragm EMG signals were amplified and band-pass filtered between 20 Hz and 1 kHz. Pes and Pga were recorded using balloon catheters which were positioned in the lower oesophagus and stomach [13,14] containing 0.8 ml and 2 ml of air, respectively, connected to differential pressure transducers. Mask pressure was measured from the port provided for the administration of supplemental oxygen in a similar fashion; these traces were not analysed by the investigators until the codes were broken by Respironics who had supplied the blinded machines (see below).
Pressure release continuous positive airway pressure (CPAP) is an evolution of CPAP that has been reported to improve patient comfort. We hypothesised the pressure release would lead to unloading of the inspiratory muscles and therefore conducted a prospective double-blind cross-over physiological study of autotitrating CPAP (APAP) against autotitrating pressure relief CPAP (PR-APAP).
Eleven patients with severe obstructive sleep apnoea (OSA; mean AHI 74.5 ± 14.4/h) were studied. We assessed neural drive by recording the oesophageal pressure, gastric pressure, transdiaphragmatic pressure and the diaphragm EMG during overnight polysomnography.
Both APAP and PR-APAP significantly reduced neural respiratory drive. Transdiaphragmatic pressure swings during apnoea (30.2 ± 11.5 cm H₂O) before treatment decreased to 9.1 ± 5.3 cm H₂O for PR-APAP and 8.5 ± 3.7 cm H₂O for APAP. The transdiaphragmatic pressure and the diaphragm EMG did not differ significantly between APAP and PR-APAP. The gastric pressure swing at expiration phase disappeared during both APAP and PR-APAP when sleep respiratory events were eliminated.
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Reproducibility of twitch and sniff transdiaphragmatic pressures

Abstract

Introduction

Section snippets

Subjects

Bilateral anterolateral magnetic stimulation of the phrenic nerves (BAMPS)

Result

Discussion

Respir. Physiol.

Respir. Physiol.

Bilateral phrenic stimulation: a simple technique to assess diaphragmatic fatigue in humans

J. Appl. Physiol.

Central components of diaphragmatic fatigue assessed by phrenic nerve stimulation

J. Appl. Physiol.

Statistical methods for assessing agreement between two methods of clinical measurement

Lancet

Twitch transdiaphragmatic pressure depends critically on thoracoabdominal configuration

J. Appl. Physiol.

Effect of lung volume reduction surgery on diaphragm strength

Am. J. Respir. Crit. Care Med.

Application of a cervical stimulating apparatus for bilateral transcutaneous phrenic nerve stimulation

J. Appl. Physiol.

Diaphragm fatigue following maximal ventilation in man

Eur. Respir. J.

Transdiaphragmatic twitch pressure: effect of lung volume and chest wall shape

Am. Rev. Respir. Dis.

Comparison of magnetic and electrical phrenic nerve stimulation in assessment of diaphragmatic contractility

J. Appl. Physiol.

Effect of lung volume reduction surgery on neuromechanical coupling of the diaphragm

Am. J. Respir. Crit. Care Med.

Diaphragm electromyogram measured with unilateral magnetic stimulation

Eur. Respir. J.