Slow Inspiration Research Articles

Effect of the Inspiratory Method and Timing of Voluntary Cough on Peak Cough Flow.

To define the effect of the inspiratory method and cough timing on peak cough flow (PCF). We investigated the effect of measurement conditions on PCF in healthy subjects (n=10). We then compared obstructive and restrictive pulmonary diseases (n=20) to assess for similar results in respiratory diseases. The PCF was measured under four conditions: before coughing, without maneuver 1 or with maneuver 2 a temporary respiratory pause (4-6 seconds) after rapid inspiration, and without maneuver 3 or with maneuver 4 a temporary respiratory pause after slow inspiration. After the measurements were completed, the PCF between the four conditions was compared for each subject group, and the effect size was calculated. PCF of maneuvers 1 and 3 were significantly higher than maneuver 4 in healthy subjects (476.34±102.05 L/min and 463.44±107.14 L/min vs. 429.54±116.83 L/min, p<0.01 and p<0.05, respectively) and patients with restrictive pulmonary disease (381.96±145.31 L/min, 354.60±157.36 L/min vs. 296.94±137.49 L/min, p<0.01 and p<0.05, respectively). In obstructive pulmonary disease, maneuver 1 was significantly higher than maneuver 4 (327.42±154.73 L/min vs. 279.48±141.10 L/min, p<0.05). The largest effect sizes were shown by maneuvers 4 and 1. PCF depends on changes in inspiratory speed before coughing and on temporary respiratory pauses after maximal inspiration. It will become necessary to unify the measurement methods for coughing strength and present appropriate coughing methods.

Effect of Various Pranayama Practices in Competitive Swimmers: A Review

Pranayama (yogic breathing) an essential component of Yoga, is said to influence both physiological and psychological aspects of humans. But its effectiveness in the field of sports especially in swimmers are less explored. The online databases were searched for the citations with “Pranayama, Yogic Breathing, competitive swimmers, competitive swimming, nadishudi pranayama, bhastrika pranayama, ujjayi pranayama, Bhramari Pranayama and Kapalabhathi” as keywords from the date of inception of the databases till October 2020. Experimental papers in English, revealing the effects of yogic breathing in competitive swimmers, effects of yogic breathing in lung capacity, lung function and psychological system and also papers showing the effect of pranayama on metabolic pathway were included in the review. The studies that had used yogic breathing in combination with other Yoga practices, studies in languages other than English, and whose abstracts were unavailable were excluded from the review. From the data gathered it was evident that pranayama has positive health effect and performance enhancement in competitive swimmers. Regular practice provides physiological and psychological wellbeing. Pranayama or yogic breathing act as a physiological stimulation. It has a multi-systemic effect in the human body. The rhythmic, slow and forceful inspiration and expiration in pranayama strengthen respiratory muscles, improve the expiratory power, and decrease resistance to the airflow in the lungs and increase voluntary breath holding time. Moreover, it brings sympathetic and parasympathetic nervous system into balance. This paper intends to explore the effect of a set of pranayama practice in competitive swimmers.

The prevalence and character of crackles (rales) in young women without significant lung disease.

Although some investigators have reported that crackles are present only in persons with lung disease, others say they also occur in normal persons. In order to clarify this difference of opinion, we determined the prevalence of crackles in 56 women without significant lung disease. The subjects ranged from 19 to 33 yr of age (mean, 21.3). They all had a FVC greater than 80% predicted and a FEV1/FVC ratio greater than 75%. None had a history of acute or chronic lung disease. During slow inspirations from residual volume, midinspiratory fine crackles were heard at the anterior bases in 35 of 56 subjects by a physician using an acoustic stethoscope, whereas a bioengineer using an 800 Hertz high pass filtered stethoscope heard crackles in 53 subjects. Crackles during tidal breathing were heard in 2 subjects. It is postulated that the crackles noted after expiration to residual volume are nonpathologic, and occur when basilar airways, which close at the end of a forced expiration, suddenly open during inspiration. Examination of the quality, timing, and anatomic distribution of the crackles in apparently normal subjects suggests that they can often be distinguished from those resulting from diseases such as bronchitis, interstitial fibrosis, and congestive heart failure.

Diaphragmatic amplitude and accessory inspiratory muscle activity in nasal and mouth-breathing adults: A cross-sectional study

The purpose of this study was to evaluate the electromyographic activity of the accessory inspiratory muscles and the diaphragmatic amplitude (DA) in nasal and mouth-breathing adults. The study evaluated 38 mouth-breathing (MB group) and 38 nasal-breathing (NB group) adults, from 18 to 30years old and both sexes. Surface electromyography (sEMG) was used to evaluate the amplitude and symmetry (POC%) of the sternocleidomastoid (SCM) and upper trapezius (UT) muscles at rest, during nasal slow inspiration at Lung Total Capacity (LTC) and, during rapid and abrupt inspiration: Sniff, Peak Nasal Inspiratory Flow (PNIF) and Maximum Inspiratory Pressure (MIP). M-mode ultrasonography assessed the right diaphragm muscle amplitude in three different nasal inspirations: at tidal volume (TV), Sniff and inspiration at LTC. The SCM activity was significantly lower in the MB group during Sniff, PNIF (p<0.01, Mann–Whitney test) and MIP (p<0.01, t-test). The groups did not differ during rest and inspiration at LTC, regarding sEMG amplitude and POC%. DA was significantly lower in the MB group at TV (p<0.01, Mann–Whitney) and TLC (p=0.03, t-test). Mouth breathing reflected on lower recruitment of the accessory inspiratory muscles during fast inspiration and lower diaphragmatic amplitude, compared to nasal breathing.

Utility of the physical examination in detecting pulmonary hypertension. A mixed methods study.

IntroductionPatients with pulmonary hypertension (PH) often present with a variety of physical findings reflecting a volume or pressure overloaded right ventricle (RV). However, there is no consensus regarding the diagnostic utility of the physical examination in PH.MethodsWe conducted a systematic review of publications that evaluated the clinical examination and diagnosis of PH using MEDLINE (1946–2013) and EMBASE (1947–2013). We also prospectively evaluated the diagnostic utility of the physical examination findings. Patients who underwent right cardiac catheterization for any reason were recruited. After informed consent, participants were examined by 6 physicians (3 “specialists” and 3 “generalists”) who were unaware of the results of the patient's hemodynamics. Each examiner independently assessed patients for the presence of a RV lift, loud P2, jugular venous distension (JVD), tricuspid insufficiency murmur and right-sided 4th heart sound at rest and during a slow inspiration. A global rating (scale of 1–5) of the likelihood that the patient had pulmonary hypertension was provided by each examiner.Results31 articles that assessed the physical examination in PH were included in the final analysis. There was heterogeneity amongst the studies and many did not include control data. The sign most associated with PH in the literature was a loud pulmonic component of the second heart sound (P2). In our prospective study physical examination was performed on 52 subjects (25 met criteria for PH; mPAP ≥25 mmHg). The physical sign with the highest likelihood ratio (LR) was a loud P2 on inspiration with a LR +ve 1.9, 95% CrI [1.2, 3.1] when data from all examiners was analyzed together. Results from the specialist examiners had higher diagnostic utility; a loud P2 on inspiration was associated with a positive LR of 3.2, 95% CrI [1.5, 6.2] and a right sided S4 on inspiration had a LR +ve 4.7, 95% CI [1.0, 15.6]. No aspect of the physical exam, could consistently rule out PH (negative LRs 0.7–1.3).ConclusionsThe presence of a loud P2 or audible right-sided 4th heart sound are associated with PH. However the physical examination is unreliable for determining the presence of PH.

The classical Starling resistor model often does not predict inspiratory airflow patterns in the human upper airway.

The upper airway is often modeled as a classical Starling resistor, featuring a constant inspiratory airflow, or plateau, over a range of downstream pressures. However, airflow tracings from clinical sleep studies often show an initial peak before the plateau. To conform to the Starling model, the initial peak must be of small magnitude or dismissed as a transient. We developed a method to simulate fast or slow inspirations through the human upper airway, to test the hypothesis that this initial peak is a transient. Eight subjects [4 obstructive sleep apnea (OSA), 4 controls] slept in an "iron lung" and wore a nasal mask connected to a continuous/bilevel positive airway pressure machine. Downstream pressure was measured using an epiglottic catheter. During non-rapid eye movement (NREM) sleep, subjects were hyperventilated to produce a central apnea, then extrathoracic pressure was decreased slowly (∼2-4 s) or abruptly (<0.5 s) to lower downstream pressure and create inspiratory airflow. Pressure-flow curves were constructed for flow-limited breaths, and slow vs. fast reductions in downstream pressure were compared. All subjects exhibited an initial peak and then a decrease in flow with more negative pressures, demonstrating negative effort dependence (NED). The rate of change in downstream pressure did not affect the peak to plateau airflow ratio: %NED 22 ± 13% (slow) vs. 20 ± 5% (fast), P = not significant. We conclude that the initial peak in inspiratory airflow is not a transient but rather a distinct mechanical property of the upper airway. In contrast to the classical Starling resistor model, the upper airway exhibits marked NED in some subjects.

Pain modulation induced by respiration: Phase and frequency effects

The voluntary control of respiration is used as a common means to regulate pain and emotions and is fundamental to various relaxation and meditation techniques. The aim of the present study was to examine how breathing frequency and phase affect pain perception, spinal nociceptive activity (RIII-reflex) and brain activity (scalp somatosensory-evoked potentials – SEP’s). In 20 healthy volunteers, painful electric shocks individually adjusted to 120% of the RIII-reflex threshold were delivered to the sural nerve near the end of inspiration or expiration phases, during three cued-breathing conditions: (1) slow breathing (0.1Hz) with slow (4s) inspiration (0.1Hz-SlowIns), (2) slow breathing (0.1Hz) with fast (2s) inspiration (0.1Hz-FastIns), and (3) normal breathing (0.2Hz) with fast (2s) inspiration (0.2Hz). Pain ratings were not affected by breathing patterns (p=0.3), but were significantly lower during inspiration compared with expiration (p=0.02). This phase effect was also observed on the N100 component of SEP’s, but only in the 0.1-Hz-FastIns condition (p=0.03). In contrast, RIII-reflex amplitude was greater during inspiration compared with expiration (p=0.02). It was also decreased in the 0.1-Hz-SlowIns compared with the 0.2-Hz condition (p=0.01). Slow breathing also increased the amplitude of respiratory sinus arrhythmia (RSA), although these changes were not significantly associated with changes in pain responses. In conclusion, this study shows that pain and pain-related brain activity may be reduced during inspiration but these changes are dissociated from spinal nociceptive transmission. The small amplitude of these effects suggests that factors other than respiration contribute to the analgesic effects of relaxation and meditation techniques.

Procedural Aspects and Physiologic Mechanisms of the Deep Inspiratory Maneuver

Sir, we have read the paper by S. Preau et al. “Hemodynamic changes during a deep inspiration maneuver predict fluid responsiveness in spontaneously breathing patients” with great interest. Based on the fundamental ideas of dynamic hemodynamic monitoring, inducing cardiac preload variations and monitoring corresponding pulse pressure variations [1], the paper presents a novel technique of varying cardiac preload in spontaneously breathing (SB) patients that does not necessitate specialised equipment apart from routine clinical monitoring. The paper is indeed relevant because it is, to our knowledge, the first to present the feasibility of a deep breathing method (deep inspiratory maneuver, DIM) for inducing preload changes. For the purpose of better understanding the presented technique, we wish to pose the following questions for the authors. Concerning compliance and applicability in terms of intention-to-treat: it is not clear which proportion of SB patients with acute circulatory failure was able to comply with the DIM. Can compliance be expected to be as high as 87% (26 of 30) for this generally defined patient group? Concerning the calculations: DIM-induced changes are defined by the authors as. DIM-induced changes = (maximal value during DIM − minimal value during quiet SB prior to DIM)/((maximal value during DIM − minimal value during quiet SB prior to DIM)/2). How large was the time window when estimating the minimal value during quiet SB prior to DIM? Did the time window vary or was it fixed? The maximal value during DIM was found in either phase 2 or phase 4 of the DIM. In which phase was the maximal value typically found? Were the maximal values during the two phases generally of the same magnitude? Instructing the patients to perform the DIM: this is important should the technique be validated by other study groups and in turn gain widespread use. Did the authors in any way evaluate if the slow continuous inspiration strain was associated with a more or less constant inspiratory flow or was most air generally inspired in the first phase of inspiration, perhaps amplifying maximal value during DIM phase 2? How were instructions given on inspiratory flow rate? Did you make any instructions to the patients (directly or indirectly) what tidal volume should be during DIM? Did they inspire to, for example, maximal or convenient lung volume? Concerning the physiological mechanisms: did you experience any patients with significant heart rate variability (HRV)? The respiratory part of HRV (with its subsequent varying passive filling time of the ventricles) could be another mechanism inducing preload variations and as such it could confound results obtained with the DIM technique. On the other hand, HRV is known to be significantly reduced during sepsis [2]. We also have a few comments and suggestions to the proposed physiological mechanisms. The decrease in left ventricular stroke volume during DIM phase 1 is suggested to be induced by increasing ventricular afterload. However, we think that another and perhaps more important mechanism is the reduced intrathoracic pressure reducing left ventricular preload during the initial phase of inspiration—until the increasing right ventricular stroke volume with the delay of pulmonary transit time again increases left ventricular preload substantially. In line with this suggestion, but as a “reversed mechanism,” we also believe that the increasing intrathoracic pressure during passive expiration (DIM phase 4) contributes somewhat to the increasing left ventricular (preload and) stroke volume in DIM phase 4 in addition to the suggested overall increase in intrathoracic blood volume. As a last comment, we would like to suggest that the DIM phases 2 and 4 could potentially disclose right ventricular failure: a large maximal value during DIM phase 2 relies on biventricular preload responsiveness whereas a large value in DIM phase 4 relies mostly, if not fully, on left ventricular preload responsiveness. Even though the authors did not encounter any cases of preload unresponsiveness associated with high ΔPPdim (specificity was 100%) low phase 2 values associated with high phase 4 values could theoretically disclose right ventricular failure—even when taking interventricular dependence into account.

Manual hyperinflation of intubated and mechanically ventilated patients in Dutch intensive care units—A survey into current practice and knowledge

In the daily bedside routine of the intensive care, potentially hazardous interventions that lack evidence need critical consideration. Therefore we examined current practice and knowledge of basic principles of manual hyperinflation (MH) in intubated and mechanically ventilated patients among intensive care unit nurses in the Netherlands. A written survey method was used, questionnaires were sent to ICU nurses specialised in mechanical ventilation in 115 Dutch hospitals. The questions related to following domains: (1) demographics; (2) use of MH; (3) presumed benefits; (4) essential elements of the MH procedure; (5) equipment and safety. The response rate was 77%. From responding ICUs the majority (96%) stated they performed MH; 27% as a daily routine procedure, 69% performed MH on indication only. MH was mainly performed by ICU nurses. Half of ICUs reported to have a MH guideline available. Improved oxygenation and better removal of sputum were presumed benefits of MH. While slow inspiration and rapid expiration are considered to be essential elements of MH procedures, the majority of respondents stated to use rapid inspiration and slow expiration. This survey indicates that MH is widely used as an important item of airway management. Importantly, there is no uniformity in the performance of the procedure. Before definitive research can be developed, standards for the MH procedure should be established.

Effect of Preceding Inspiratory Speed and End-Inspiratory Pause on Forced Expiratory Manoeuvre in Healthy Subjects and Chronic Obstructive Pulmonary Disease Patients

Background: Lower peak expiratory flow (PEF) and forced expiratory volume in 1 s (FEV₁) have been consistently found after slow inspiration with end-inspiratory pause (EIP). Objectives: It was the aim of this study to establish the respective influence of the speed of preceding inspiration (SPI) and EIP on the parameters obtained from the following expiratory forced vital capacity (FVC) manoeuvre. Methods: In 8 healthy subjects and 12 patients with chronic obstructive pulmonary disease (COPD), a number of inspirations with different SPI and EIP were performed. In the subsequent FVC manoeuvre, maximal expiratory flows, including PEF, and maximal expired volumes at different times, including FEV₁, were measured. For each FVC manoeuvre, peak expiratory time, expired volume at PEF (as % of FVC), flow limitation by the negative expiratory pressure technique and FVC were checked to be sure of achieving a similar expiratory effort and starting inflation lung volume. Results: The highest values of PEF and FEV₁ were found in normal subjects and COPD patients after fastest SPI without EIP (p < 0.001). In normal subjects, no significant PEF and FEV₁ changes during FVC manoeuvre were observed with different SPI, in the absence of EIP. In contrast, inspirations with slower SPI (inspiratory time >2 s) without EIP were followed by lower PEF in COPD patients (p < 0.05). As compared with inspirations without EIP, those with a presence of EIP were invariably followed by lower PEF and FEV₁, both in normal subjects and in COPD patients (p < 0.05). Conclusions: The effect of SPI on subsequent PEF and FEV₁ is irrelevant in healthy subjects as well as in COPD patients, unless SPI is too slow (inspiratory time >2 s), while any EIP decreases these indices in all individuals.

FEV6: a shortcut in spirometry?

During the past 50 yrs, the forced expiratory manoeuvre has formed the basis for the most extensively used lung function test. Although “spirometry” means measurement of breath and, therefore, should include all kinds of measurements related to breathing, it is now almost a convention that spirometry is synonymous with measurements involving a forced vital capacity (FVC). In his historical note, Yernault 1 mentions that Tiffenau and Pinelli published the first results from recording forced expiration manoeuvres in 1947. A couple of years later, the Tiffeneau test was developed, defining the ratio between the forced expiratory volume in one second (FEV1) and the vital capacity (VC). To calculate this ratio, both the FVC and the VC (always measured during expiration) became acceptable. With spirometry, there is a potential ability to diagnose obstructive and restrictive abnormalities. Obstruction is a condition with decreased FEV1/VC, whereas restriction is a condition with decreased total lung capacity (TLC). Therefore, it is important that the VC (or FVC) gives the best possible measure of TLC. A decreased VC may occur due to loss of alveolar space, which decreases TLC. Obstruction may lead to airway closure and a decrease of FVC, but TLC is not decreased. The largest VC is the inspiratory vital capacity (IVC), which is measured during a slow inspiration from residual volume to TLC, and, therefore, IVC was recommended as the denominator in the FEV1/VC ratio 2. As IVC cannot be obtained during the FVC manoeuvre, it requires an extra measurement, and is seldom used outside specialised lung function laboratories. The use of FVC instead is not without problems. In severely obstructed patients, the total exhalation may last for up to 20 s 3, until the current end-of-test standards for accurately measured FVC 4 are met. This may be very …

Hemodynamic Observations on a Yogic Breathing Technique Claimed to Help Eliminate and Prevent Heart Attacks: A Pilot Study

This pilot study investigated the hemodynamics of a yogic breathing technique claimed "to help eliminate and prevent heart attacks due to abnormal electrical events to the heart," and to generally "enhance performance of the central nervous system (CNS) and to help eliminate the effects of traumatic shock and stress to the CNS." Parameters for (4) subjects were recorded during a preexercise resting period, a 31-minute exercise period, and a postexercise resting period. Parameters for subjects were recorded in a laboratory at the University of California, San Diego. Parameters for 3 males (ages 44, 45, 67) and 1 female (age 41) were recorded. One (1) subject (male age 45) had extensive training in this technique. This yogic technique is a 1 breath per minute (BPM) respiratory exercise with slow inspiration for 20 seconds, breath retention for 20 seconds, and slow expiration for 20 seconds, for 31 consecutive minutes. Fourteen beat-to-beat parameters were measured noninvasively and calculated for body surface area to yield: stroke index (SI), heart rate (HR), cardiac index, end diastolic index, peak flow, ejection fraction, thoracic fluid index, index of contractility, ejection ratio, systolic time ratio, acceleration index, and systolic, diastolic, and mean arterial pressures (MAPs). Left stroke work index (LSWI) and stroke systemic vascular resistance index (SSVRI) were calculated. We report on SI, HR, MAP, LSWI, and SSVRI and how they can help to describe hemodynamicstate changes. This technique induces dramatic shifts in all hemodynamic variables during the 1 BPM exercise and can produce unique changes in the postexercise resting period after long-term practice that appears to have a unique effect on the brain stem cardiorespiratory center regulating the Mayer wave (0.1-0.01 Hz) patterns of the cardiovascular system. Preclinical studies are warranted to examine the possible long-term effects of this technique that appear to reset a cardiorespiratory brain-stem pacemaker. We postulate that this effect may be the basis for the purported yogic health claim.

Bronchodilation test in COPD: effect of inspiratory manoeuvre preceding forced expiration.

The effects of an inspiratory manoeuvre preceding forced expiration on functional tests performed under routine conditions before and after inhalation of a bronchodilator drug (salbutamol) were assessed on 150 consecutive chronic obstructive pulmonary disease outpatients. The patients performed forced vital capacity manoeuvres either immediately after a rapid inspiration (manoeuvre no. 1) or after a slow inspiration with a 4-6 s pause (manoeuvre no. 2). Under baseline conditions, forced expiratory volume in one second (FEV1) values were 8% (% control) larger with manoeuvre no. 1 than no. 2. FEV1 values increased with salbutamol administration by approximately 8% and were, on average, still 7% larger with manoeuvre no. 1 than no. 2. The incidence of reversibility, assessed according to American Thoracic Society criteria, was 76% when manoeuvre no. 2 was selected to represent baseline conditions and manoeuvre no. 1 was chosen to represent the effects of bronchodilator administration, whereas the lowest incidence (2%) was found when manoeuvre no. 1 was selected to represent baseline conditions and manoeuvre no. 2 was chosen to represent the effects of bronchodilator administration. These results indicate that the time dependence of the forced vital capacity manoeuvre has an important impact on the assessment of routine lung function in a clinical setting and supports the notion that the time course of the inspiration preceding the forced vital capacity manoeuvre should be standardised.

Targeted delivery of inhaled drugs: current challenges and future goals.

Past success of topical delivery to the lung stems more from the therapeutic nature of drugs used rather than the delivery device. Both the pressurized metered dose inhaler (pMDI) and the dry powder inhaler (DPI) are inefficient, placing a small fraction of the dose at the site of action. Most of the drug deposits in the mouth and is swallowed. Modifications to the pMDI may redress this by improving the coordination of dose generation and inspiration, or by the use of spacers. The DPI can be improved by the use of special excipients. Nevertheless, fundamental weaknesses that limit improvements in targeting drugs to the lung remain. Ideally, a stationary or slow-moving cloud of a selected particle size distribution should be generated at the source by the device. The rate of cloud generation should be such that a patient can accommodate it during a slow inspiration. Many new devices are in development, harnessing one or more of these principles. Respimat (Boehringer Ingelheim, Ingelheim am Rhein, Germany), a soft mist inhaler, shows particular promise. It generates a fine slow-moving cloud over a period exceeding 1 second and incorporates many design features to win patient acceptance.

Respiratory pathophysiologic responses: The efficacy of slow versus faster inhalation of cromolyn sodium in protecting against allergen challenge in patients with asthma

Background: Approximately one third of patients with allergy-induced asthma who are treated with aerosolized cromolyn sodium (CS) fail to achieve a full therapeutic effect. This lack of effectiveness could involve nonhomogeneous distribution of drug in the lung as a result of high inspiratory flow rates. Objective: We sought to determine the efficacy of slow versus faster inhalation of CS in protecting against allergen challenge in patients with asthma. Methods: Eight patients with asthma underwent two allergen challenges 30 minutes after pretreatment with CS that was inhaled from a large holding chamber at ~30 L/min or ~70 L/min. Percent decreases in FEV 1 at a common dose of allergen on the two challenge days were compared. Values of skew (an indicator of aerosol distribution homogeneity) obtained from gamma camera lung images after slow and faster inhalation of radiolabeled CS were also compared. Results: Mean (± SD) allergen-induced decrease in FEV 1 was 5.4% ± 4.2% after slow inspiration of CS, which was significantly less than the allergen-induced decrease in FEV 1 after faster inhalation of CS with 12.6% ± 11% ( p < 0.05). Mean skew values were also significantly decreased after slow inspiration of CS, and differences in decreases in allergen FEV 1 and skew values for the two breathing maneuvers were significantly correlated. Conclusion: These data indicate that protection against allergen-induced asthma can be optimized by slowly inspiring CS from a large holding chamber compared with faster inhalation of the drug. These results appear to be related to enhanced distribution homogeneity of CS within the lungs.

Dependence of forced vital capacity manoeuvre on time course of preceding inspiration in patients with restrictive lung disease

In normal subjects and patients with airway obstruction, flows during a forced vital capacity (FVC) manoeuvre are higher after a fast inspiration without an end-inspiratory pause (manoeuvre 1) as compared to a slow inspiration with an end-expiratory pause of approximately 5 s (manoeuvre 2). In this study, we investigated the influence of these manoeuvres on maximal expiratory volume-time and flow-volume curves in patients with restrictive lung disease. Eleven patients with restrictive lung disease were studied. Their average (+/-SD) lung function test results were: FVC=55+/-12% predicted value, forced expiratory volume in one second (FEV1) 52+/-20% pred, FEV1/FVC 85+/-6%, total lung capacity 55+/-8% pred, and carbon monoxide transfer factor 47+/-18% pred. The patients performed the two FVC manoeuvres in random order. We compared the ensuing spirograms and maximal expiratory flow-volume curves from which peak expiratory flow, FEV1, FEV1/FVC, maximal mid-expiratory flow, and maximal flows were computed. All spirometric indices were significantly higher with manoeuvre 1 than 2. Maximal expiratory flows at the same lung volume were also significantly higher with manoeuvre 1 than 2, in all patients. Routine spirometric indices, obtained during a forced vital capacity manoeuvre depend on the time course of the preceding inspiration in patients with restrictive lung disease. Therefore, the forced vital capacity manoeuvre should be standardized if used in clinical, epidemiological and research studies.

Effect of Different Inspiratory Maneuvers on FEV1 in Patients With Cystic Fibrosis

The time course of inspiration has been shown to have a significant influence on the subsequent maximal expiratory flows and timed forced expiratory volumes in healthy adults and those with COPD. The purpose of this study was to evaluate the effect of two different inspiratory maneuvers on the spirogram in 15 patients with cystic fibrosis, aged 13 to 35 years, who had mild to moderate airway obstruction. Patients performed a forced expiratory maneuver either after a rapid inspiration without an end-inspiratory pause or after a slow inspiration with a 4-s end-inspiratory pause. Flow-time and volume-time curves were measured by a pneumotachograph. The mean values of FVC, FEV1, and peak expiratory flow were significantly larger by 11%, 13%, and 26%, respectively, after the rapid inspiration without an end-inspiratory pause compared to the slow inspiration with the end-inspiratory pause. This discrepancy probably reflects differences in effective elastic recoil pressure between the two maneuvers. Although the nature of this phenomenon is not fully understood, our results show that for spirometry in patients with cystic fibrosis, the preceding inspiratory maneuver influences the results. An important corollary is that this inspiratory maneuver should be standardized.

The effect of inspiratory maneuvers on expiratory flow rates in health and asthma: influence of lung elastic recoil.

We studied the effect of breath holding and inspiratory speed on airflow during the FVC maneuver in seven healthy subjects and eight patients with asthma. The purpose of the study was to determine whether the effects of inspiratory speed and breath holding on expiratory flow were greater in patients with asthma than in healthy individuals; whether these effects were lessened by inhalation of aerosolized bronchodilator in the patients with asthma; and whether were was a relationship between the lung elastic recoil pressure and the expiratory flow achieved during four different maneuvers. We found that peak expiratory flow rate (PEFR) was significantly lower after both a slow inspiration and a breath hold than after a fast inspiration without a breath hold. In addition, a breath hold was associated with a significantly lower FEV1. The effects of inspiratory speed and breath holding in the patients with asthma were not significantly different from those observed in the healthy subjects. There was a significant relationship between lung elastic recoil pressure at the point of onset of the FVC maneuvers (Pel Blow) and expiratory flow in both healthy and asthmatic subjects. Also, the decrease in Pel Blow with equivalent breath-hold time was greater in asthmatic subjects, which is consistent with an increase in viscoelastic elements in the lung. These findings corroborate previous suggestions that inspiratory speed and the duration of breath holding have significant implications in the performance of spirometry and peak flow measurements, and indicate the importance of standardization of the preceding inspiration when determining FEV1 and PEFR.

Dependence of maximal flow-volume curves on time course of preceding inspiration in patients with chronic obstruction pulmonary disease.

Thirteen patients with chronic obstructive pulmonary disease (COPD) performed forced vital capacity (FVC) maneuvers either immediately after a rapid inspiration (maneuver 1) or after a slow inspiration with a 4- to 6-s end-inspiratory pause (maneuver 2). Seated in a body plethysmograph, they breathed through a pneumotachograph. Inspirations were initiated from resting end-expiratory lung volume. Abdominal muscle activity was recorded by means of surface electrodes. With maneuver 1: (1) expiratory flows were 20 to 40% larger in the volume range 10 to 95% FVC; (2) peak expiratory flow was on average 30% higher; and (3) FEV1, expressed as percent of FVC, increased by about 8%. No substantial differences in the pattern of abdominal muscle activity occurred between maneuvers. The dependence of maximal flow-volume curves on the time course of the preceding inspiration is probably related in part to the viscoelastic elements present within the respiratory system, which, stretched during rapid inspirations, increase the effective elastic recoil during the FVC maneuver 1. This cannot occur with maneuver 2, because of stress relaxation of the viscoelastic elements during the 4- to 6-s breathhold preceding the FVC maneuver. Other factors (e.g., time constant inequality) might also be involved. In any case, the results imply that the inspiratory maneuver prior to FVC must be standardized.

What do pediatricians in training know about the correct use of inhalers and spacer devices?

Most patients with asthma in the United States are cared for by nonspecialist physicians. Because inhaled medications are the mainstay of asthma therapy and their successful use requires both practical skills and theoretic knowledge, we wondered how much nonspecialist physicians know about the use of metered-dose inhalers and spacer devices. Fifty pediatricians in training were interviewed individually. Practical knowledge was assessed by asking each to demonstrate correct use of a placebo inhaler and a spacer device (Inspirease [Key Pharmaceuticals, Inc., Miami, Fla.] and Aerochamber with mask [Monaghan Medical Corp., Plattsburgh, N.Y.]). Of the seven recommended steps for use of metered-dose inhalers, the residents demonstrated an average of 3.8 steps correctly. The most common errors included not shaking the metered-dose inhaler before use (18% of residents correct) and insufficient breath holding (28% correct). In testing spacer use, the most common errors included not shaking the canister (16% correct) and incorrect number of activations and inhalations (12% correct). Many residents were not familiar with correct assembly of the spacer (48% correct). Theoretic knowledge of metered-dose inhaler and spacer use was evaluated by a written questionnaire. The most common deficiencies in theoretic knowledge related to the purpose of slow inspiration and breath holding. Most of the participants had been treating children with asthma and had prescribed metered-dose inhalers (45 of 50, 90%) and spacer devices (76%) in the past. The results suggest that, despite substantial involvement in asthma management, pediatricians in training have significant inadequacies in knowledge of the practical and theoretic aspects of metered-dose inhaler and spacer use. Asthma specialists may need to take a leading role in the development and implementation of educational programs about inhaled therapy.