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PubMed1999

Relationship between resting hypercapnia and physiologic parameters before and after lung volume reduction surgery in severe chronic obstructive pulmonary disease.

Patients with severe chronic obstructive pulmonary disease (COPD) have varying degrees of hypercapnia. Recent studies have demonstrated inconsistent effects of lung volume reduction surgery (LVRS) on PaCO2; however, most series have excluded patients with moderate to severe hypercapnia. In addition, no study has examined the mechanisms responsible for the reduction in PaCO2 post-LVRS. We obtained spirometry, body plethysmography, diffusion capacity, respiratory muscle strength, 6-min walk test, and incremental symptom-limited maximal exercise data in 33 consecutive patients pre- and 3 to 6 mo post-LVRS, and explored the relationship between changes in PaCO2 and changes in the measured physiologic variables. All patients underwent bilateral LVRS via median sternotomy and stapling resection by the same cardiothoracic surgeon. Patients were 57 +/- 8 yr of age with severe COPD, hyperinflation, and air trapping (FEV1, 0.73 +/- 0.2 L; TLC, 7.3 +/- 1.6 L; residual volume [RV], 4.8 +/- 1.4 L), and moderate resting hypercapnia (PaCO2, 44 +/- 7 mm Hg; range, 32 to 56 mm Hg). Post-LVRS, PaCO2 decreased by 4% (PaCO2 pre 44 +/- 7 mm Hg, PaCO2 post 42 +/- 5 mm Hg; p = 0.003). Patients with higher baseline values of PaCO2 had the greatest reduction in PaCO2 post-LVRS (r = -0.61, p < 0.001). Significant correlations existed between reduction in PaCO2 and changes in FEV1 (r = -0.56; p = 0.0007), maximal inspiratory pressure (PImax) (r = -0.46; p = 0.009), diffusing capacity of the lungs for carbon monoxide (DLCO) (r = -0.47; p = 0.008), and RV/TLC (r = 0.41; p = 0. 02). Correlation existed also between reduction in PaCO2 and breathing pattern at maximal exercise: maximal minute ventilation (V Emax) (r = -0.47; p = 0.009), and tidal volume (VT) (r = -0.40; p = 0.02). The changes in PaCO2 post-LVRS showed marked intersubject variability. We conclude that LVRS, by reducing hyperinflation, air trapping, and improving respiratory muscle function, enables the lung and chest wall to act more effectively as a pump, thereby increasing alveolar ventilation and reducing baseline resting PaCO2. In addition, patients with higher baseline levels of PaCO2 demonstrate the greatest reduction in PaCO2 post-LVRS, and should not be excluded from receiving LVRS.

Aged↗

PubMed1996

Diaphragm function in patients with cervical cord injury or prior poliomyelitis infection.

Diaphragm function was evaluated in cervical cord injury patients (CCI), 1-3 years after injury (CCI(1-3)) and 10 years or more after injury (CCI(> or = 10)), as well as in a group of prior poliomyelitis infection patients (PPI), requiring intermittent positive pressure ventilation (IPPV) for about 6 h per night. Measurements included transdiaphragmatic pressure swings (delta Pdi) at rest, during maximal inspiratory efforts against closed airways (delta Pdi(max)) and during sniff manoeuvres (ie maximal inhalation through the nose, delta Pdi(sniff)), vital capacity normalized to age and height (VC(%pred)), tidal volume (Vt), relative inspiratory time (Ti/Ttot), breathing frequency (f(b)), and the tension-time index of the diaphragm (TTdi = delta Pdi/delta Pdi(max) x Ti/Ttot). The median VC(%pred) was 50% in the CCI(1-3) group and 57% in the CCI (> or = 10) group, but only 28% in the PPI group. Delta Pdi(max) values were similar for the CCI(1-3) (11.8 kPa) and CCI(> or = 10) (11.9 kPa) groups but were lower (71. kPa) in the PPI group. Due to the reduction in delta Pdi(max), the PPI group had higher delta Pdi/delta Pdi(max) values than the CCI groups, however, the TTdi was similar amongst the different groups studied. A submaximal exercise test in five cervical cord injury patients and in five polio patients with similar delta Pdi(max), delta Pdi(sniff) and TTdi values at rest revealed clear group differences with respect to force development, in that CCI patients showed significant increases in TTdi, while PPI demonstrated only minor changes. In CCI patients, an increase in ventilation was accompanied by an increase in delta Pdi/delta Pdi(max) while in contrast, the PPI patients showed no increase in delta Pdi/delta Pdi(max). We conclude that CCI patients, both recently and previously injured, have a similar maximal inspiratory force and are less impaired than the PPI patients. The TTdi at rest is similar in all groups, but the PPI patients react to inspiratory loads with little increases in TTdi, while the CCI patients increase their TTdi above fatiguing (0.15) levels. The different behaviours may be linked to loss of sensory pathways in the CCI patients.

Adult↗

PubMed1983

Phrenic activity and intercostal muscle emg during inspiratory loading in newborn kittens.

The effects of airway occlusions at functional residual capacity (FRC) on both "integrated" phrenic activity (Phr) and intercostal muscle electromyogram (intEMG) were studied in intact and vagotomized spontaneously breathing kittens during the 1st wk of life. Animals were anesthetized im with a mixture of ketamine (30 mg/kg) and acepromazine (1.1 mg/kg). In the intact kittens, inspiratory loading led to a significant increase in peak amplitudes of both Phr and intEMG and prolongation of inspiratory (TI) and expiratory (TE) times. Mean values of rate of rise of Phr and intEMG measured at 200 ms (intEMG200) from the onset of inspiration were unaffected. The results indicated that in newborns the vagal component of the load compensation is of great importance. Following vagotomy, airway occlusion produced a significant increase in mean values of TI and intEMG only. These small but significant changes suggest that most of the load compensation reflex is dependent on prolongation of TI. Increased intEMG200 during loading in the vagotomized kittens, observed during several trials, implies that the intercostal fusion-alpha interaction may operate in newborns.

Airway Obstruction↗

PubMed1998

Exercise performance during inspiratory resistance breathing under exhaustive constant load work.

The purpose of this study was to determine the effects of different inspiratory resistances on exercise performance and to describe physiological and subjective responses during constant load work of an intensity that elicits the maximum sensitivity to respiratory factors of respirator wear. Nine subjects (mean age 25.8 +/- 4.8 years) performed exhaustive treadmill exercise during constant load work of 80% of maximal aerobic capacity while inspiring against one of five randomly assigned inspiratory resistance conditions. For inspiratory resistances of 0.20 kPa (R1), 0.29 kPa (R2), 0.39 kPa (R3), and 0.49 kPa (R4), measured at a steady air flow rate of 85 L min-1, average performance times were 84, 75, 54, and 30% of the control condition. Performance time reductions were significant for R3 and R4 trials. Results also indicated a significantly reduced mean respiration rate, minute ventilation, and oxygen ventilatory equivalent (VE/VO2) for the R4 condition at exercise breakpoint compared to control. For resistances R1-R4, mean VE/VO2 were significantly reduced from control by approximately 12, 17, 19, and 31%. At breakpoint, mean ratings of perceived exertion were similar for control, R1, R2, and R3 conditions but were significantly lower for R4 versus control. Breathing comfort did not differ significantly between resistances below the R3 level, but discomfort was significantly greater for conditions R3 and R4. These findings suggest that the impact of the respiratory limitations of respirators can be diminished by employing respirators with inspiratory resistances below the R3 level.

Adult↗

PubMed1997

Immediate postoperative enteral feeding results in impaired respiratory mechanics and decreased mobility.

OBJECTIVE: The authors set out to determine whether immediate enteral feeding minimizes early postoperative decreases in handgrip and respiratory muscle strength. SUMMARY BACKGROUND DATA: Muscle strength decreases considerably after major surgical procedures. Enteral feeding has been shown to restore strength rapidly in other clinical settings. METHODS: A randomized, controlled, nonblinded clinical trial was conducted in patients undergoing esophagectomy or pancreatoduodenectomy who received immediate postoperative enteral feeding via jejunostomy (fed, n = 13), or no enteral feeding during the first 6 postoperative days (unfed, n = 15). Handgrip strength, vital capacity, forced expiratory volume in one second (FEV1), and maximal inspiratory pressure (MIP) were measured before surgery and on postoperative days 2, 4, and 6. Fatigue and vigor were evaluated before surgery and on postoperative day 6. Mobility was assessed daily after surgery using a standardized descriptive scale. Postoperative urine biochemistry was evaluated in daily 24-hour collections. RESULTS: Postoperative vital capacity (p < 0.05) and FEV1 (p = 0.07) were consistently lower (18%-29%) in the fed group than in the unfed group, whereas grip strength and maximal inspiratory pressure were not significantly different. Postoperative mobility also was lower in the fed patients (p < 0.05) and tended to recover less rapidly (p = 0.07). Fatigue increased and vigor decreased after surgery (both p < or = 0.001), but changes were similar in the fed and unfed groups. Intensive care unit and postoperative hospital stay did not differ between groups. CONCLUSIONS: Immediate postoperative jejunal feeding was associated with impaired respiratory mechanics and postoperative mobility and did not influence the loss of muscle strength or the increase in fatigue, which occurred after major surgery. Immediate postoperative enteral feeding should not be routine in well-nourished patients at low risk of nutrition-related complications.

Age Factors↗

PubMed1991

Continuous positive pressure breathing without and with inspiratory pressure support in acute respiratory failure when mean airway pressure is constant.

OBJECTIVE: Mean airway pressure (Pawm) may be a major factor for PaO2, functional residual capacity, and cardiac output in acute respiratory failure (ARF). To clarify effects of inspiratory pressure support (IPS) as a ventilatory mode in ARF, we studied patients in ARF either using IPS or continuous positive pressure breathing (CPAP) at the same level of Pawm, measuring respiratory and circulatory parameters. METHODS: After consent, 10 patients in ARF of moderate severity (PaO2:FiO2 205 +/- 108 at positive end expiratory pressure (PEEP) 8.7 +/- 3.1 cmH2O; mean +/- SD) were investigated. Measurements were on day 7.4 +/- 8.4 after onset of ARF. IPS was 13.5 +/- 3.9 cmH2O above PEEP. To result in constant Pawm, PEEP was reduced for IPS (Pawm IPS 11.1 +/- 3.6 vs. Pawm CPAP 9.9 +/- 3.3 cmH2O, ns; PEEP IPS 8.7 +/- 3.1 vs. PEEP CPAP 10.6 +/- 4.3 cmH2O, p = 0.04). Inspired concentration of oxygen (FiO2) and the ventilator (Siemens 900 C) were not changed for the individual patient. RESULTS: For IPS, tidal volume (VT) increased by +31% and respiratory frequency (RF) decreased by -19% (VT IPS 608 +/- 179 vs. VT CPAP 465 +/- 141 ml, p = 0.01; RF IPS 21.6 +/- 7.6 vs. RF CPAP 26.7 +/- 8.3 breaths per minute, p = 0.02). Also, PaCO2 showed a tendency to be lower for IPS, not reaching significance (PaCO2 IPS 44.3 +/- 5 vs. PaCO2 CPAP 47.4 +/- 4.9 mmHg, p = 0.1). All other parameters were unchanged (expiratory minute volume, PaO2, pH, intravascular pressures, cardiac index, stroke volume index (n = 6), systemic and pulmonary vascular resistances, venous admixture, deadspace (n = 3), oxygen consumption and oxygen delivery). WE CONCLUDE: When Pawm remained constant, IPS added to CPAP improved VT and RF without improving oxygenation or deteriorating circulation in patients with ARF of moderate severity. IPS mainly supports the ability to breathe spontaneously in ARF.

Acute Disease↗

PubMed1985

Collateral ventilation during high-frequency oscillation in dogs.

Mechanics of collateral channels during high-frequency oscillatory ventilation (HFOV) were assessed in eight anesthetized dogs, using a modification of Hilpert's technique. Base-line functional residual capacity was measured with a body plethysmograph, with inspiratory efforts induced by phrenic nerve stimulation. The resistance (Rcoll) and time constant (Tcoll) of collateral channels at five lung volumes were measured during HFOV and positive end-expiratory pressure (PEEP). Rcoll and Tcoll were significantly higher during HFOV (P less than 0.001); the differences did not correlate with resting lung volumes. The calculated static compliance of the wedged segment was similar during HFOV and PEEP (P greater than 0.005). Mean pressures measured in small airways during HFOV corresponded to the midline between the inflation and deflation limbs of the static pressure-volume curves, indicating similar pressure-volume characteristics of the respiratory system during HFOV and static conditions. We conclude that HFOV increases resistance to gas flow through collateral channels but that this pathway may still be important in gas exchange.

Animals↗

PubMed1996

Effects of fenoterol on inspiratory effort sensation and fatigue during inspiratory threshold loading.

We studied the effects of a single dose of fenoterol on the relationship between inspiratory effort sensation (IES) and inspiratory muscle fatigue induced by inspiratory threshold loading in healthy subjects. The magnitude of the threshold was 60% of maximal static inspiratory mouth pressure (PI,mmax) at functional residual capacity, and the duty cycle was 0.5. Subjects continued the threshold loaded breathing until the target mouth pressure could no longer be maintained (endurance time). The intensity of the IES was scored with a modified Borg scale. Either fenoterol (5 mg) or a placebo was given orally 2 h before loading in a randomized double-blind crossover protocol. The endurance time with fenoterol (34.4 +/- 8.6 min) was longer than that with the placebo (22.2 +/- 7.1 min; P < 0.05). The ratio of high- to low-frequency power of the diaphragmatic electromyogram (EMGdi) decreased during loading; the decrease was less with fenoterol (P < 0.05). The EMGdi also decreased with loading; the decrease was greater on fenoterol treatment (P < 0.01). The PI,mmax and maximal transdiaphragmatic pressure (Pdi) were similarly decreased after loading on either treatment. The intensity of the IES rose with time during loading in both groups but was lower with fenoterol than with the placebo (P < 0.05). The ratio of Pdi to integrated activity of the EMGdi increased with fenoterol (P < 0.05). Fenoterol treatment increased both superimposed Pdi twitch and Pdi twitch of relaxed diaphragm and decreased the value of (1-superimposed Pdi twitch/Pdi twitch of relaxed diaphragm). Thus we conclude that in normal subjects fenoterol reduces diaphragmatic fatigue and decreases the motor command to the diaphragm, resulting in a decrease in IES during inspiratory threshold loading and a prolongation of endurance.

Adult↗

PubMed2000

Serial changes in spirometry during an ascent to 5,300 m in the Nepalese Himalayas.

The aims of the present study were to determine the changes in forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1) and peak expiratory flow (PEF), during an ascent to 5,300 m in the Nepalese Himalayas, and to correlate the changes with arterial oxygen saturation measured by pulse oximetry (SpO2) and symptoms of acute mountain sickness (AMS). Forty-six subjects were studied twice daily during an ascent from 2,800 m (mean barometric pressure 550.6 mmHg) to 5,300 m (mean barometric pressure 404.3 mmHg) during a period of between 10 and 16 days. Measurements of FVC, FEV1, PEF, SpO2, and AMS were recorded. AMS was assessed using a standardized scoring system. FVC fell with altitude, by a mean of 4% from sea level values [95% confidence intervals (CI) 0.9% to 7.4%] at 2,800 m, and 8.6% (95% CI 5.8 to 11.4%) at 5,300 m. FEV1 did not change with increasing altitude. PEF increased with altitude by a mean of 8.9% (95% CI 2.7 to 15.1%) at 2,800 m, and 16% (95% CI 9 to 23%) at 5,300 m. These changes were not significantly related to SpO2 or AMS scores. These results confirm a progressive fall in FVC and increase in PEF with increasing hypobaric hypoxia while FEV1 remains unchanged. The increase in PEF is less than would be predicted from the change in gas density. The fall in FVC may be due to reduced inspiratory force producing a reduction in total lung capacity; subclinical pulmonary edema; an increase in pulmonary blood volume, or changes in airway closure. The absence of a correlation between the spirometric changes and SpO2 or AMS may simply reflect that these measurements of pulmonary function are not sufficiently sensitive indicators of altitude-related disease. Further studies are required to clarify the effects of hypobaric hypoxia on lung volumes and flows in an attempt to obtain a unifying explanation for these changes.

Adult↗

PubMedDate not supplied

Using an evidence-based protocol to guide rehabilitation and weaning of ventilator-dependent cervical spinal cord injury patients.

An evidence-based clinical protocol was developed to improve ventilatory muscle strength and endurance of ventilator-dependent cervical spinal cord injury (SCI) patients. The goal was to help these patients discontinue mechanical ventilation. The protocol, based on findings from other studies in the literature, consisted of pretraining optimization, as well as progressive resistance and endurance training. Following the protocol, mean maximal inspiratory pressure for low tetraplegic patients improved 75 percent, mean maximal expiratory pressure improved 71 percent, mean vital capacity increased 59 percent, mean on-vent endurance time increased 91.6 percent, and mean off-vent breathing time increased 76.7 percent. Both high and low tetraplegic patients achieved gains in inspiratory and expiratory muscle strength, vital capacity, on-vent endurance, and off-vent breathing times. High tetraplegic patients improved their ability to spontaneously ventilate for short periods in case of accidental disconnection from the ventilator, while low tetraplegic patients were able to discontinue mechanical ventilation, which was the desired clinical outcome for this preliminary study.

Adult↗

PubMed1993

Physiological effect of endobronchial radiotherapy in patients with major airway occlusion by carcinoma.

BACKGROUND: Endobronchial radiotherapy by a high dose rate remote after-loading technique (high dose rate brachytherapy) has become an established treatment for major airway occlusion by inoperable carcinoma of the bronchus. Only limited objective data on its effect on pulmonary physiology and on radiographic and bronchoscopic appearances are available. The aim of this study was to make a detailed assessment of patients before and after high dose rate brachytherapy to determine which investigations were useful and to generate data for comparing this with other methods of treatment. METHODS: Twenty patients with major airway obstruction by inoperable lung cancer underwent a detailed assessment before receiving endobronchial radiotherapy (15 Gy at 1 cm in a single fraction) and six weeks after treatment. This included chest radiography, computed tomography of the thorax, bronchoscopy including an obstruction index, five minute walking tests, isotope ventilation and perfusion lung scanning, and full lung function tests with maximum inspiratory and expiratory flow-volume loops. RESULTS: Nineteen patients (mean age 69 years) completed the study. Symptomatic improvement occurred in 17 patients. A collapsed lobe or lung, seen on the chest radiograph in 13, reexpanded in nine. Bronchoscopic appearances improved in 18, the mean obstruction index decreasing from 6.2 to 2.8. The isotope scans showed significant increases in the percentage of total lung ventilation (V) and perfusion (Q) measured over the abnormal lung (V 17.7% to 27.7%, Q 15.1 to 21.9%). Five minute walking distance (305 to 329 m), forced expiratory volume in one second (FEV1 1.45 to 1.61 l), forced vital capacity (FVC 2.17 to 2.48 l) and ratio of forced expiratory to forced inspiratory flow rate at 50% vital capacity (FEF50/FIF50 0.58 to 0.88) all increased significantly. CONCLUSIONS: Endobronchial radiotherapy led to subjective benefit in most cases in terms of symptoms and bronchoscopic and radiological appearances. There was objective improvement in spirometric indices and in exercise tolerance with increased pulmonary ventilation and perfusion and evidence of decreased intrathoracic airway obstruction.

Aged↗

PubMed2005

The effect of lung inflation on the inspiratory action of the canine parasternal intercostals.

Inflation induces a marked decrease in the lung-expanding ability of the diaphragm, but its effect on the parasternal intercostal muscles is uncertain. To assess this effect, the phrenic nerves and the external intercostals were severed in anesthetized, vagotomized dogs, such that the parasternal intercostals were the only muscles active during inspiration, and the endotracheal tube was occluded at different lung volumes. Although the inspiratory electromyographic activity recorded from the muscles was constant, the change in airway opening pressure decreased with inflation from -7.2+/-0.6 cmH2O at functional residual capacity to -2.2+/-0.2 cmH2O at 20-cmH2O transrespiratory pressure (P<0.001). The inspiratory cranial displacement of the ribs remained virtually unchanged, and the inspiratory caudal displacement of the sternum decreased moderately. However, the inspiratory outward rib displacement decreased markedly and continuously; at 20 cmH2O, this displacement was only 23+/-2% of the value at functional residual capacity. Calculations based on this alteration yielded substantial decreases in the change in airway opening pressure. It is concluded that, in the dog, 1) inflation affects adversely the lung-expanding actions of both the parasternal intercostals and the diaphragm; and 2) the adverse effect of inflation on the parasternal intercostals is primarily related to the alteration in the kinematics of the ribs. As a corollary, it is likely that hyperinflation also has a negative impact on the parasternal intercostals in patients with chronic obstructive pulmonary disease.

Animals↗

PubMed2005

Exercise flow-volume loops in prepubescent aerobically trained children.

We studied mechanical ventilatory constraints in 13 aerobically trained (Tr) and 11 untrained (UT) prepubescent children by plotting the exercise flow-volume (F-V) loops within the maximal F-V loop (MFVL) measured at rest. The MFVL allowed to determine forced vital capacity (FVC) and maximal expiratory flows. Expiratory and inspiratory reserve volumes relative to FVC (ERV/FVC and IRV/FVC, respectively) were measured during a progressive exercise test until exhaustion. Breathing reserve (BR) and expiratory flow limitation (expFL), expressed in percentage of tidal volume (V(T)) and defined as the part of the tidal breath meeting the boundary of the MFVL, were measured. Higher FVC and maximal expiratory flows were found in Tr than UT (P < 0.05) at rest. Our results have shown that during exercise, excepting one subject, all Tr regulated their V(T) within FVC similarly during exercise, by breathing at low lung volume at the beginning of exercise followed breathing at high lung volume at strenuous exercise. In UT, ERV/FVC and IRV/FVC were regulated during exercise in many ways. The proportion of children who presented an expFL was nearly the same in both groups (approximately 70% with a range of 14 to 65% of V(T)), and no significant difference was found during exercise concerning expFL. However, higher ventilation (V(E)), ERV/FVC, and dyspnea associated with lower BR, IRV/FVC, and SaO2 were reported at peak power in Tr than UT (P < 0.05). These results suggest that, because of their higher Ve level, trained children presented higher ventilatory constraints than untrained. These may influence negatively the SaO2 level and dyspnea during strenuous exercise.

Child↗

PubMed1979

Ventilation response and drive during hypoxia in adult patients with asthma.

We studied ventilation and inspiratory muscle activity during progressive isocapnic hypoxia in adult asthmatic patients to determine whether the decreased hypoxic ventilatory response previously identified is due to the mechanical abnormalities of the respiratory system or to low respiratory center output. The mouth pressure produced by inspiratory muscle activity, a reflection of respiratory center output, was measured at 100 msec of inspiration against an occluded airway at functional residual capacity. At end-tidal oxygen tension (PETO2) of 80 mm Hg, inspiratory muscle activity was greater in asthmatic patients than in normal subjects for the same level of ventilation, but at PETO2 of 40 mm Hg, both inspiratory muscle activity and ventilation were lower in asthmatic patients. Consequently, the changes in inspiratory muscle activity and ventilation per mm Hg change in PETO2 were lower in the asthmatic patients. To generate the same ventilation during progressive hypoxia, more inspiratory muscle activity was needed by asthmatic patients. We concluded that the decreased hypoxic ventilation in asthmatic patients resulted from both decreased respiratory center output and from mechanical abnormalities of the respiratory system.

Adolescent↗

PubMed1983

Respiratory muscle dysfunction in systemic lupus erythematosus.

An assessment of pulmonary mechanics revealed weakness of inspiratory and expiratory muscles as cause of the restrictive ventilatory defect (vital capacity: 47 +/- 10 percent predicted) in seven (ages 33 to 62 years) out of 26 consecutive patients with systemic lupus erythematosus (SLE). Maximal inspiratory transdiaphragmatic pressures were reduced mainly due to the markedly increased (more positive) esophageal pressures. During maximal expiratory efforts, esophageal and gastric pressures were grossly decreased. These abnormalities probably may be considered part of a more generalized, yet subclinical muscle disorder due to the SLE with, however, predominant involvement of the respiratory muscles. The abnormalities were not related to the use of corticosteroids or generalized inanition. The static expiratory lung compliance was reduced in all patients (55 +/- 18 percent predicted), but normalized immediately following passive inflation of the lungs to transpulmonary pressures of more than 30 cm H2O in two of the three subjects tested. The volume restriction was not progressive over a period of 38.5 patient-years.

Adult↗

PubMed2006

Pulmonary function assessment in an infant with Barnes syndrome: proactive evaluation for surgical intervention.

Our aim for this study was to report pulmonary mechanics in a neonate with a severe case of Barnes syndrome, a rare form of thoracolaryngopelvic dysplasia, and to use these data to guide ventilatory support and serve as a presurgical screening tool. A comprehensive pulmonary function evaluation was performed on a 36-day-old patient with Barnes syndrome who was being mechanically ventilated because of severe pulmonary distress secondary to thoracic dystrophy. The measurements consisted of respiratory volumes including functional residual capacity, ventilatory mechanics including compliance and resistance, and thoracoabdominal synchrony. Chest wall compliance was 64% below normal, and the thoracoabdominal motion was indicative of predominantly abdominal displacement during inspiratory breaths. The lungs were functioning at a low functional residual capacity, resulting in low lung compliance and increased pulmonary resistance. As a result of the evaluation, the patient was recommended for lateral thoracic expansion surgery and the ventilatory management was adjusted to focus on end-distending pressure support.

Abnormalities, Multiple↗

PubMed1988

Effect of laryngeal anesthesia on pulmonary function testing in normal subjects.

Pulmonary function tests (PFT) were performed on 11 normal subjects before and after topical anesthesia of the larynx. The PFT consisted of flow volume loops and body box determinations of functional residual capacity and airway resistance, each performed in triplicate. After the first set of tests, cotton pledgets soaked in 4% lidocaine were held in the pyriform sinuses for 2 min to block the superior laryngeal nerves. In addition, 1.5 ml of 10% cocaine was dropped on the vocal cords via indirect laryngoscopy. PFT were repeated 5 min after anesthesia. Besides routine analysis of the flow volume loops, areas under the inspiratory (Area I) and expiratory (Area E) portions of the loops were calculated by planimetry. Area I, peak inspiratory flow (PIF), as well as forced inspiratory flow at 25, 50, and 75% forced vital capacity (FVC), decreased after anesthesia. Peak expiratory flow decreased after anesthesia, but Area E and forced expiratory flow at 25, 50, and 75% FVC were unchanged. This protocol also was performed in 12 normal subjects with isotonic saline being substituted for the lidocaine and cocaine. In this group, no significant differences were observed when flow volume loop parameters were compared before and after topical application of saline. In 5 spontaneously breathing anesthetized dogs, posterior cricoarytenoid muscle and afferent superior laryngeal nerve activity were recorded before and after laryngeal anesthesia performed with the same procedure used in the human subjects. Laryngeal anesthesia resulted in a substantial decrease or a complete disappearance of afferent SLN activity recorded during unobstructed and obstructed respiration. The data suggest that laryngeal receptors help modulate upper airway patency in man.

Adult↗

PubMed1975

The effect of artificial ventilation on functional residual capacity and arterial oxygenation. II. Comparison of spontaneous respiration and artificial ventilation at similar arterial carbon dioxide tensions, tidal volumes and inspiratory gas flow rates.

We have compared cardiac output, gas exchange and pulmonary mechanics during spontaneous breathing and artificial ventilaton under conditions which kept PaCO2 within the normal range and maintained constant tidal volume and inspired gas flow rate. In dogs anaesthetized with pentobarbitone and ventilated with air, artificial ventilation increased VD/VT but did not reduce Q angstrom, FRC, or CL. PaO2 increased and A-aDO2 decreased during aritificial ventilation, perhaps because of a small increase in Q angstrom and a small decrease in oxygen consumption. It appears that many of the reported deleterious effects of artificial ventilation may be due to the use of other anaesthetic agents and patterns of ventilation, and to changes in PaCO2.

Anesthesia↗