Maximum Breathing Capacity Research Articles

Role of exercise in severe COVID-19 case

Abstract Severe COVID-19 infection can lead to prolonged recovery and troublesome symptoms. The symptoms reported in those patients were dyspnea, fatigue, weakness, anxiety, and activity intolerance. Patients showed limited exercise capacity and interfered with daily activities, as well as the quality of life. We report the role of exercise in improving activity tolerance in a survivor of a COVID-19 severe case. A male patient, 51 years, came to outpatient pulmonary rehabilitation after hospitalization due to a severe case of COVID-19. The patient had a low activity tolerance presented as fatigue, dyspnea, activity-induced oxygen desaturation, and inability to perform exercise testing, in addition to mild anxiety. A set of exercises consisting of breathing, flexibility, muscular, and cardiorespiratory endurance were given for 4 weeks along with psychological counseling. Barthel Index, cardiorespiratory fitness, sit-to-stand test, Fatigue Severity Scale, Medical Research Council Dyspnea Scale, and maximum breathing capacity were recorded as outcome measures. A Zung Self-rating Anxiety Scale and insomnia severity index were also measured. After 4 weeks, the symptoms of activity intolerance decreased. There were improvements in all outcomes except for the insomnia severity scale. Experts recommend that COVID-19 patients should carry out regular daily activities and low to moderate-intensity exercise in the first 6-8 weeks after discharge. Resuming daily physical activities as early as possible can affect functional recovery. It is also beneficial for general fitness, fatigue, emotional disturbance, and lack of confidence. In this patient, low-intensity exercises as recommended by experts were given to improve activity tolerance.

Assessment of pulmonary function tests among patients with hypothyroidism

Background: The respiratory system involvement in hypothyroidism varies from mild dyspnea to a more severe respiratory failure. This has been reported as reduction in expiratory and inspiratory muscle strength, alveolar hypoventilation along with reduction of hypoxic and hypercapnic ventilatory drives and decreased maximal breathing capacity and decreased diffusion capacity among hypothyroid patients. Material & Methods: The present prospective study was conducted at department of respiratory medicine of our tertiary care hospital. In present study, we enrolled 50 study participants from outdoor and from ward by simple random sampling. Clearance from Institutional Ethics Committee was taken before start of study. Written informed consent was taken from each study participant Results In the present study, majority of patients showed obstructive pattern i.e. 30% which was followed by mixed pattern among 22% patients and 18% of patients showed restrictive pattern. 30% of patients showed normal respiratory pattern on pulmonary function test. On the basis of the Spirometry examination finding among case group, the mean value of FEV1 (L) was 1.38±0.68, the man value of FVC(L) was 2.24±0.71. on assessment the mean value of FEV1/FVC proportion (postbronchodilator) was 61.6 ±11.3.

The impact of muscle strength on exercise capacity and symptoms.

The capacity to exercise is a major contributor to functional limitation and is accompanied by increased morbidity and mortality. What are the most important physiological contributors to exercise capacity?Cross-sectional data from consecutive patients referred to the McMaster University Medical Centre exercise laboratory for incremental cardiopulmonary exercise testing from 1988 to 2012 were analysed. Exercise capacity was determined by maximal power output (MPO) in kpm·min−1. The contributions of quadriceps strength (maximal peak force in kg using maximal dynamic voluntary contractions against hydraulic resistance), inspiratory muscle strength (determined using maximal inspiratory pressure (MIP)), maximal breathing capacity (MBC) and gas exchange (carbon monoxide transfer coefficient (KCO)) were determined using regression coefficients in a multiple linear regression model. Dyspnoea and leg fatigue were measured using the modified Borg scale. Contributors to dyspnoea and leg fatigue were assessed using nonlinear regression.A total of 36 389 patients were included (60% male, mean±sd age 53±18 years). Mean±sd MPO, quadriceps strength and MIP achieved were 792±333 kpm·min−1, 46±18 kg and 75±31 cmH2O, respectively. MIP and quadriceps strength accounted for over half the variation in MPO (R2=0.57). Quadriceps strength was a stronger predictor of MPO (standardised regression coefficient, β±se 0.37±0.005) than MBC (β±se 0.16±0.005) and KCO (β±se 0.16±0.004), when adjusted for age, sex, height and weight. The effort required to cycle and breathe at any given power intensified systematically as both respiratory and peripheral muscle strength declined.Muscle weakness causes exercise intolerance and should be routinely assessed in patients presenting with fatigue and dyspnoea, and those with functional limitation both in the presence or absence of disease.

EVALUATION OF THE MITOCHONDRIA RESPIROMETRIC FUNCTION IN THE CONDITIONS OF PATHOLOGIES OF VARIOUS GENESES

The aim of the paper is to assess the change in the mitochondrial respirometric function under conditions of various pathologies.Materials and methods. The study was performed on male Wistar rats. Experimental focal cerebral ischemia, traumatic brain injury, coronary occlusive myocardial infarction and muscle dysfunction were used as pathological models. Focal ischemia was reproduced by the method of irreversible thermocoagulation of the middle cerebral artery. Traumatic brain injury was modeled by the method of free fall of the load. Experimental myocardial infarction was reproduced by ligating the descending branch of the left coronary artery. Muscle dysfunction was modeled by the method of «forced swimming with a 20% burden». The respiratory function of mitochondria was assessed by the method of respirometry by the change in oxygen consumption when introducing mitochondrial respiration into the medium: Oligomycin, Rotenone and FCCP. Additionally, we evaluated the intensity of the glycolysis process and the activity of respiratory complexes I, II, IV and V. In order to comprehensively assess the respiratory function, an ELISA study was conducted to determine the concentration of ATP, mitochondrial ATP synthetase, cytochrome C oxidase and NADP-Oxidase 4.Results. In the course of the study it was established that under conditions of experimental cerebral ischemia, traumatic brain injury, myocardial infarction and muscle dysfunction, the ATP-generating ability of mitochondria the maximum breathing and respiratory capacity deteriorated, herby the decrease in overall respiratory function was accompanied by an increase in glycolysis, which was uncompensated, as well as dysfunction of mitochondrial complexes I, II, IV and V, confirmed by an increase in NADPH oxidase 4 activity and a decrease in cytochrome C oxidases and ATP synthetase. As a result, the observed changes in mitochondrial respiration function contributed to a decrease in ATP concentration under conditions of cerebral ischemia - by 3.2 times (p <0.05), traumatic brain injury – by 2.6 times (p <0.05), myocardial infarction – by 1.8 times (p <0.05) and muscle dysfunction – by 4 times (p <0.05).Conclusion. Basing on the data obtained, we can assume that in conditions of cerebral ischemia, traumatic brain injury, myocardial infarction and muscle dysfunction, there is deterioration of the mitochondrial respirometric function with inhibition of ATP synthesis and increased glycolysis.

INDICATORS OF THE RESPIRATORY SYSTEM FUNCTIONAL CONDITION IN STUDENTS OF THE NORTHERN HIGHER EDUCATION INSTITUTION

A spirographic study of 80 students from 1-3 courses of Surgut State Pedagogical University at the age of 18-20 years old, born and residing in the North has been carried out. The aim of the work was to study the peculiarities of the respiratory system of the university students. Measurement of respiratory function was carried out by means of Program Apparatus Complex "Spiro-Spectrum". Results were analyzed by standard methods of mathematical statistics. All surveyed belonged to 1 and 2 health groups. Students with chronic and acute diseases of the respiratory system were excluded from surveyed group. It was found out that needed respiratory minute volume at rest in students-smokers was achieved by increase in respiratory rate and not by respiratory volume which was more energy-consuming. Reduce of maximum expiratory flow from 50 % and 75 % of forced vital capacity (FVC) and forced expiratory flow rate from 25-75 % FVC in students-smokers were reflection of respiratory failure and a high risk of obstructive disorders development. Lower rates of maximum breathing capacity in smokers compared to proper values show decrease in the frontier of external breathing.

FEATURES OF EXTERNAL BREATH SYSTEM REACTION (RESPONSE) TO LOCAL COOLING OF HAND AND FOOT SKIN IN YOUNG ABLE-BODIED PERSONS

Changes of static and dynamic indicators of the external breath function during local cooling of the hand and foot skin in 30 young men and 30 girls aged 18-24 years which were born and constantly lived in the European North of Russia has been studied. The study was carried out with the ergospirometry system Oxycon Pro. At the initial stage, the indicators of functional state of external breath were estimated with the spirography. The following stage consisted of carrying out local cooling of the hand skin. The examinee put down a hand for 1 minute in a vessel with water which temperature successively was 24° С, 15° С and 8° С. Right after cooling repeated spirography was performed. The restoration interval between the tests was 25-30 minutes. In the same sequence, cooling of feet was carried out, and spirography was performed. It has been established that local cooling significantly influenced some indicators of external breath. Thus during cold impact on the skin peripheral thermoreceptors both of the hands and feet of the girls, a statistically significant increase in the respiratory minute volume (RMV) and respiratory rate (RR) indicators was observed, and in the young men, similar reactions were revealed only during feet cooling. During cooling of the young men's hands, only the RR value increased significantly, while the maximal breathing capacity (MBC) values and the breathing reserve (BR) values significantly decreased. Besides, a decrease in the RR indicators during cold impact on the foot skin in the young men was observed.

High-flux dialysis improves pulmonary ventilation function in uremic patients

Lung injury commonly accompanies uremia caused by renal failure. Uremia is typically treated using hemodialysis (dialysis) to restore electrolyte and fluid balance. A more recent, less commonly used method, high-flux dialysis, has not yet been investigated for its potential benefit to lung function. The aim of the present study was to determine whether high‑flux dialysis affects pulmonary function. We assessed various pulmonary function parameters in patients with uremia before and after routine or high‑flux dialysis. Pulmonary function was assessed via determination of the forced vital capacity (FVC), maximum breathing capacity (MBC), forced expiratory volume in 1sec (FEV1), peak expiratory flow (PEF), maximal midexpiratory flow (MMEF) curve, maximal expiratory flow in 25% vital capacity (V25) and diffusion capacity of the lungs for carbon monoxide (DLco) in 42patients with uremia and 24healthy individuals. Patients with uremia were divided into two groups; the high‑flux group (treated with high-flux dialysis; n=21) and the routine group (treated with conventional dialysis; n=21). Lung function was reassessed in the two groups after 3months of dialysis. The two groups of patients with uremia exhibited reduced lung function parameters compared with healthy individuals (all P<0.05), indicating the presence of impaired lung function secondary to uremia. Following dialysis, the FEV1, PEF, MMEF and V25 values increased significantly compared with their respective baseline values prior to treatment for each group (ANOVA, P<0.05). Furthermore, increases were more marked in patients treated with high-flux dialysis compared with those treated using routine dialysis (P<0.05). Thus, lung injury caused by uremia was shown to be improved following dialysis, with high-flux dialysis offering a greater benefit than routine dialysis.

Effect of Savitri pranayama on respiratory parameters in healthy individuals

Background: Yoga makes the mind calm & relaxed, strengthens & tunes the body, brings them into harmony with each other. Pranayama have been shown to reduce the resting respiratory rate, further they increase the vital capacity, timed vital capacity, Maximum voluntary ventilation, Breath holding time, Maximum expiratory pressure. Savitri pranayama is one of the unique pranayama techniques which involves slow, rhythmic, and deep breathing. This pranayama has an added advantage that it is effective even if it is done in lying down position .So it can be practiced by non-ambulatory patients too. Aims & Objective: To compare changes in respiratory parameters in the subjects practicing Savitri Pranayama and with that of subjects not practicing any type of Pranayama. Material and Methods: New entrants in yoga class of shivanand ashram, Ahmedabad were selected as subjects for this study & compared with control group- not performing any type of exercise or yoga. The test group were trained by a qualified instructor & then practiced savitri pranayama for 6 days in a week for 12 weeks. Peak Expiratory Flow Rate, Maximum Breathing Capacity, Expiratory pressure,40mm endurance test, Breath holding time were recorded twice in test group - before starting pranayama & after 12 weeks. Readings of control group were taken in both phases too. Results: First phase recording showed no significant differences in any of the tested parameters between Test and Control groups. Second phase recordings showed significant differences in all the tested parameters between Test and Control groups. Conclusion: In the test group there is statistically significant increase in PEFR, MBC, EP, 40mm endurance test & BHT. So it is concluded that a practice of Savitri Pranayama has beneficial respiratory effects. This pranayam can be practiced by bedridden & physically handicap persons. It has psychological effect for relaxing the patients so can be practiced for mental well-being.

ADAPTIVE RESPONSES OF EXTERNAL RESPIRATION IN HEALTHY STUDENTS ANNUAL CYCLE IN EUROPEAN NORTH

In dynamics of the annual cycle of young men and women aged 18-22 years, static and dynamic lung volumes have been studied. It has been shown that in both groups, respiratory and minute volume, vital capacity and maximum breathing capacity were maximum in autumn - winter.

Pulmonary gas exchange in diving

Diving-related pulmonary effects are due mostly to increased gas density, immersion-related increase in pulmonary blood volume, and (usually) a higher inspired Po(2). Higher gas density produces an increase in airways resistance and work of breathing, and a reduced maximum breathing capacity. An additional mechanical load is due to immersion, which can impose a static transrespiratory pressure load as well as a decrease in pulmonary compliance. The combination of resistive and elastic loads is largely responsible for the reduction in ventilation during underwater exercise. Additionally, there is a density-related increase in dead space/tidal volume ratio (Vd/Vt), possibly due to impairment of intrapulmonary gas phase diffusion and distribution of ventilation. The net result of relative hypoventilation and increased Vd/Vt is hypercapnia. The effect of high inspired Po(2) and inert gas narcosis on respiratory drive appear to be minimal. Exchange of oxygen by the lung is not impaired, at least up to a gas density of 25 g/l. There are few effects of pressure per se, other than a reduction in the P50 of hemoglobin, probably due to either a conformational change or an effect of inert gas binding.

A 53-year-old woman with muscular atrophy showing hypersomnia and respiratory failure

A 53-year-old female patient noticed weakness and wasting of limb muscles at age 30 years.Over the following years, the sternocleidomastoid muscles became atrophic and wasted, with frontal baldness. At age 43, her eyesight began to fail because of bilateral cataracts. She had experienced increasing sleepiness since adolescence. She was always very apt to drop off to sleep and always had difficulty in getting up in the morning. Examination at age 45 years revealed a hatchet face with frontal baldness,bilateral ptosis, grasp and percussion myotonia, and muscular atrophy of the four limbs, greater distally, and at the sternocleidomastoid. Pulmonary function tests revealed ventilatory insufficiency of a restrictive type with reduction of vital capacity (1800 mL, 55% of predicted), total lung capacity (2500 mL) and maximum breathing capacity (24 I/min, 25% of predicted).The ratio of the forced expiratory volume in 1 second to the forced vital capacity was 80%, showing no sign of airway obstruction. Arterial gas analysis values at rest while awake showed marked hypercapnea and hypoxia with respiratory acidosis (PaO2 40 mmHg; PaCO2 68 mmHg; pH 7.29). The maximum inspiratory and expiratory pressure (71.3 cmH2O and 83.2 cmH2O) and the diffusion capacity for CO (15.3 mL/min/ mmHg) revealed no abnormality.The ventilatory response to CO2 inhalation was markedly impaired. However, voluntary hyperventilation lowered the CO2 by 23 mmHg. Mental changes such as inattention, apathy and memory defect, which were not noticed in her childhood, were observed. Her IQ was 48. Brain CT scan disclosed enlargement of the lateral ventricles. At age 46, the patient experienced sudden respiratory insufficiency caused by local anesthesia for a cataract operation.She died of acute pneumonia at 53 years of age.

Disability and Breathlessness in Asthmatic Patients—A Scoring Method by Repetitive Inspiratory Effort

Measurement of disability and breathlessness in asthma is important to guide treatment. Using an incentive spirometer, Triflo II (Tyco Healthcare, Mansfield, MA, USA), we developed a three-minute respiratory exercise test (3-MRET) to score the maximal breathing capacity (MBC) and perception of dyspnea (POD) index by means of repetitive inspiratory efforts achieved within 3 minutes. POD index was calculated based on the ratio of breathlessness on visual analogue scale over MBC score. In 175 normal healthy subjects and 158 asthmatic patients of mild (n = 26), moderate (n = 78), and severe (n = 54), severity, the mean (95% CI) MBC scores in mild, moderate, and severe asthma patients were 168 (145–192), 153 (136–169), and 125 (109–142) respectively, and 202 (191–214) in normal subjects (p < 0.001). The mean POD index in mild, moderate, and severe asthma patients was 16 (9–23), 25 (14–37), and 57 (14–100), respectively, and 6 (4–7) in normal subjects (p < 0.001). Intraclass correlation coefficients for MBC score and POD index in 17 asthmatic and 20 normal subjects were high. In 14 asthmatic patients randomized to receiving nebulized β2-agonist or saline in a cross-over, double-blind study, % forced expiratory volume in one second (FEV1) change correlated with % change in MBC score [rs = 0.49, p < 0.01] and POD index [rs−0.46, p = 0.012]. In 21 asthmatic and 26 normal subjects, the MBC score and POD index correlated with the walking distance and walking POD index of the six-minute walking test (6MWT). We conclude that 3MRET is discriminative between asthmatic patients of varying severity and normal subjects, is reproducible, is responsive to bronchodilator effect, and is comparable with 6MWT. Taken together, it has the potential to score disability and POD in asthma simply and effectively.

Preoperative assessment of the thoracic surgery patient: pulmonary function testing.

Tests of pulmonary function before thoracic surgery can help to assess the risk of perioperative morbidity and mortality, and are the basis for estimating remaining lung function after resection of lung tissue. Testing has evolved over the past 50 years from reliance on the maximum breathing capacity to a range of studies including spirometry, and measurement of lung volume, diffusing capacity, and arterial blood gases, and the interpretation of these in conjunction with radionuclide scanning. The surgeon must consider both the early postoperative decrement in function and the level to which the patient is expected to recover. Although it is difficult to establish absolute limiting values, and current surgical techniques are blurring the boundary further, the reported experience underlying current guidelines is reviewed.

Does the respiratory system limit the aerobic working capacity of humans?

The question concerning respiratory function reserves among the factors determining the maximal power of muscular work is considered. Even in strenuous physical exercise, pulmonary ventilation does not exceed a rather constant level for every individual. Studies conducted using the programmed isocapnic hyperpnea method developed by the authors demonstrated that this level precisely reflects the functional respiratory reserve that is one of the factors limiting maximal work performance intensity. Under normal conditions, the functional respiratory reserve is 20 to 40% less than the so-called maximal breathing capacity (MBC) determined in a test, which requires voluntarily forcing respiratory efforts and exorbitant energy expenditure for the respiratory muscles performance. Therefore, the MBC should be regarded only as a parameter of ventilatory forced capacity used in extreme situations such as competitive athletic loading or in more resistive breathing when decreased respiratory system reserves become a leading factor rigidly limiting aerobic working capacity. A scheme is given that illustrates the ambiguous role of the respiratory system in this aspect.

Assessment of abdominal muscle contractility, strength, and fatigue.

We evaluated abdominal muscle contractility and fatigue by measuring twitch gastric pressure (Pgat) after percutaneous supramaximal electrical stimulation of the abdominal wall before and after sit-ups to task failure. Mouth pressures during maximal voluntary expulsive maneuvers (PEmax) at TLC and FRC with superimposed twitches, and maximum voluntary ventilation (MVV) were also assessed. Mean fresh Pgat was 36.1 +/- 3.0 cm H2O with a coefficient of variation that ranged between 3.0 to 4.8%. Pgat decreased by 25% (p < 0.001) and 37% (p < 0.001) at 1 and 30 min after sit-ups. During maximal voluntary contraction twitch occlusion never occurred. PEmax at TLC and FRC decreased by 15% (p < 0.001) and 11% (p < 0.017) at 1 min, and 8% (p < 0.036) and 9% (p < 0.030) at 30 min after sit-ups, respectively. Despite the abdominal muscle fatigue, MVV values at 1 and 30 min after sit-ups were not significantly different from the value obtained before the sit-ups. We conclude that (1) Pgat is a useful objective indicator of abdominal muscle contractility and fatigue; (2) during maximal voluntary expulsive maneuvers the abdominal muscles are never fully activated; (3) sit-ups lead to substantial low-frequency fatigue but little high-frequency fatigue of the abdominal muscles, which has little effect on maximal breathing capacity.

Relationship between external resistances, lung function changes and maximal exercise capacity.

In upper airway obstruction (UAO) the relationship between the degree of obstruction, exercise limitation and lung function indices is not well established. Therefore, we investigated in nine healthy subjects (age 36+/-9 yrs) the effects of two added resistances at the mouth (R1 = added resistance with 7.8 mm diameter; R2 = 5.7 mm) on forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), airway resistance (Raw) and maximal breathing capacity (measured during 15 s = measured maximum breathing capacity (MBCm); calculated as FEV1x37.5 = calculated maximum breathing capacity (MBCc)) on the one hand, and maximum exercise capacity (W'max), minute ventilation (V'E) and CO2 elimination (V'CO2) on the other. We found that R1 had almost no influence on FEV1 but decreased PEF by approximately 35% and increased Raw by almost 300%; it decreased W'max by merely approximately 10% while maximal exercise ventilation (V'Emax) was only 65% of control and only reached approximately 40% MBCc and approximately 70% MBCm; yet V'E and V'CO2 were significantly reduced at high exercise levels indicating hypoventilation. With R2, FEV1 was reduced by 25% and PEF by 55%, and Raw was increased by 600%; W'max was approximately 60% of control, V'Emax was only 35% of control and reached approximately 30% MBCc and approximately 60% MBCm, V'E was already reduced at moderate exercise levels. We conclude that: 1) an upper airway obstruction of 6 mm diameter (but not of 8 mm) had a marked influence on maximum exercise capacity due to hypoventilation; 2) calculated maximum breathing capacity markedly overestimated measured maximum breathing capacity because the forced expiratory volume in one second is an insensitive index of upper airway obstruction and because it does not take inspiratory flow limitation into account; and 3) a 10% decrease in maximum exercise capacity was linearly related with a 7% decrease in the forced expiratory volume in one second and a 150% increase in airway resistance. A 10% decrease in maximal exercise ventilation was related to a 8.5% decrease in peak expiratory flow and 9% decrease in measured maximum breathing capacity.

The birth and development of the forced expiratory manoeuvre: a tribute to Robert Tiffeneau (1910-1961).

The forced expiratory manoeuvre was first described by Tiffeneau and Pinelli working in Paris (France), in December 1947, who proposed measurement of the "pulmonary capacity usable on exercise" (capacité pulmonaire utilisable à l'effort) (CPUE), the maximal volume expelled in one second after a deep inspiration. It was intended to replace the measurement of the maximum breathing capacity, a difficult and tiring manoeuvre. A similar approach was later followed in the USA by Gaensler, who proposed the "timed vital capacity" in 1951. The name CPUE was changed to "volume expiratoire maximum seconde" (VEMS) by a group of European experts, who met in Paris on February 13, 1954, whereas the expression "forced expiratory volume" was adopted by the British Thoracic Society in 1957. Despite numerous attempts to examine the forced expiration in a different manner, the VEMS and/or forced expiratory volume in one second (FEV1) remain, after 50 yrs the main variables used daily by the respiratory physician. Although primarily a pharmacologist, Robert Tiffeneau (1910-1961) undoubtedly deserves to figure among the pioneers of respiratory medicine.

Limited resection of bronchogenic carcinoma in the patient with impaired pulmonary function

Surgical resection is the treatment of choice for non-small cell carcinoma of the lung. In some patients with marked impairment of pulmonary function, cardiac disease, or other medical conditions, the surgeon is faced with performing either a limited resection or carrying out nonoperative therapy. Impaired pulmonary functions are defined as a maximum breathing capacity (MBC) of 35% to 40% of predicted; forced expiratory volume in 1 second (FEV,) of less than 1 L; and a forced expiratory volume 25%–75% (FEV 25–75) of less than 0.6 L. When MBC values are less than 35% of predicted; the FEV 1 is less than 0.6 L; and the FEV 25–75 is less than 0.6 L, elective resection is contraindicated. Useful criteria for indicating an elective limited resection include the following: (1) T1 lesion, (2) peripheral location, (3) margins easily encompassed by resection, and (4) no gross lymph node involvement. In a study of 67 patients, there was 1 postoperative death, with less than an 80% 2-year survival and a 31% 5-year survival. The role of video-assisted thoracoscopy in the management of primary lung cancer remains to be defined. When the high-risk patient can be operated on with attendant low morbidity and mortality, I believe, at the current time, a video-assisted thoracic resection for prirmary lung cancer is not the best option, as the patient will be offered a compromised operation, and I suspect follow-up studies will prove this correct.

Respiratory impedance measurements in a dose-response study of isocapnic hyperventilation with cold air.

Spirometry and impedance of the respiratory system were compared after increasing rates of isocapnic cold air hyperventilation (IHCA) in 10 asthmatics and 11 healthy nonsmokers. In the control group IHCA at 60% of indirect maximum breathing capacity (IMBC) resulted in a significant, equal increase in resistance at lower and higher frequencies, suggesting central airway constriction. In the asthmatics negative frequency dependence of resistance and a significant increase in resonant frequency and decrease in the reactance at 8 Hz were found at 40 and 60% IMBC. These changes suggest an increase in the resistance of the peripheral airways. The frequency dependence of resistance and resonant frequency were found to be the most sensitive measures to differentiate between normals and asthmatics. It is concluded that impedance measurements provide a suited method to assess the response in cold air provocation tests.

Effects of water temperature on pulmonary volumes in immersed human subjects

Pulmonary volumes and capacities have been measured at three water temperatures (Tw = 25, 34, 40 °C) in standing subjects immersed up to the shoulders. The comparison of data obtained in air with those obtained in thermoneutral immersion (Tw = 34 °C) confirms the results previously published in several studies. The comparison of data obtained in immersion at different Tw shows: 1. 1. A significant decrease in vital capacity (VC) with bath temperature (VC 40 °C > VC 34 °C > VC 25 °C). The same decrease is observed in the inspiratory reserve volume (IRV) while the expiratory reserve volume (ERV), the residual volume (RV) and the functional residual capacity (FRC) do not vary. 2. 2. A significant decrease in maximum breathing capacity (MBC) with bath temperature (MBC 40 °C > MBC 25 °C). 3. 3. A significant increase in tidal volume (VT) in cold or hot water compared to thermoneutral water (V t40 °C >V t34 °C; V t34 °C < V t °C) during quiet breathing. Breathing frequency does not change, thus ventilation (V̇) follows the same evolution as V t. The relative abdominal (ABD) contribution to V t, estimated by a double belt inductance plethysmograph, is reduced at T w = 25 °C but unchanged at T w = 40 °C compared to thermoneutral bath. Beside variations in the metabolic state, the variations of the pulmonary volumes as a function of T w are estimated to be mainly due to alterations in respiratory muscles functioning.