phenylephrine-hydrochloride and Hypercapnia

The use of positive-pressure nasal ventilation in combination with LTOT in stable COPD patients with hypercapnic respiratory failure controls hypoventilation and improves daytime ABGs, sleep, and quality of life. Nasal ventilation in COPD is unlikely to produce benefit unless used with supplemental oxygen therapy at night. The patients who show the greatest reduction in overnight PaCO2 with ventilation are the patients most likely to benefit from long-term ventilatory support. Although there is now evidence for short-term benefit from NPPV in hypercapnic COPD, large multicenter studies with survival, exacerbations, and hospital admissions as the primary end points are required to evaluate longer-term effects of this potentially important intervention.

Topics: Bronchiectasis; Cystic Fibrosis; Home Care Services; Humans; Hypercapnia; Long-Term Care; Lung Diseases, Obstructive; Nose; Oxygen Inhalation Therapy; Positive-Pressure Respiration; Respiratory Mechanics; Ventilators, Negative-Pressure

The upper airways are a complex structure with multiple functions; many of the muscles participate in the act of respiration. The neural control of upper airway muscles is distinct from that of chest wall muscles under a variety of circumstances. Coordinated activation of upper airway muscles, both regionally and inter-regionally, results in changes in upper airway size and resistance, alterations in the route of airflow, and increases in the ability of the airways to resist collapse. Several disorders have now been described in which neuromuscular drive abnormalities and/or mechanical dysfunction of the upper airways occur, resulting in clinical disease.

Topics: Afferent Pathways; Behavior; Blood Pressure; Bronchial Spasm; Humans; Hypercapnia; Hypoxia; Laryngeal Diseases; Larynx; Lip; Mechanoreceptors; Muscles; Neuromuscular Diseases; Nose; Palate, Soft; Pharynx; Pulmonary Stretch Receptors; Reflex; Respiration; Respiratory Physiological Phenomena; Respiratory System; Sleep Apnea Syndromes; Vagus Nerve; Vocal Cords

Hypercapnia is associated with worse clinical outcomes in exacerbations of COPD. The present study aimed to determine the effects of nasal high flow (NHF) therapy on transcutaneous partial pressure of carbon dioxide (PtCO. In a single-blind randomized controlled cross-over trial, 48 participants with COPD were allocated in random order to all of four 20 min interventions: NHF at 15 L/min, 30 L/min and 45 L/min or breathing room air with each intervention followed by a washout period of 15 min. The primary outcome measure was PtCO. NHF results in a small flow-dependent reduction in PtCO

Topics: Aged; Aged, 80 and over; Blood Gas Monitoring, Transcutaneous; Carbon Dioxide; Cross-Over Studies; Female; Humans; Hypercapnia; Male; Middle Aged; Nose; Oxygen Inhalation Therapy; Partial Pressure; Pulmonary Disease, Chronic Obstructive; Respiratory Rate; Single-Blind Method

Nasal Highflow (NHF) delivers a humidified and heated airflow via nasal prongs. Current data provide evidence for efficacy of NHF in patients with hypoxemic respiratory failure. Preliminary data suggest that NHF may decrease hypercapnia in hypercapnic respiratory failure. The aim of this study was to evaluate the mechanism of NHF mediated PCO. In 36 hypercapnic COPD patients (PCO. This study demonstrates effective PCO. Clinical Trials: NCT02504814; First posted July 22, 2015.

Topics: Aged; Blood Gas Analysis; Cannula; Carbon Dioxide; Female; Humans; Hypercapnia; Male; Middle Aged; Noninvasive Ventilation; Nose; Partial Pressure; Prospective Studies; Pulmonary Disease, Chronic Obstructive

This study examined the usefulness of nasal Duo positive airway pressure (DuoPAP) in the treatment of very low birth weight preterm infants with neonatal respiratory distress syndrome (NRDS).. Eighty-five very low birth weight preterm infants with NRDS were randomly divided into two groups. Forty-five infants were treated with DuoPAP, while 40 infants were treated using nasal continuous positive airway pressure (nCPAP). The study outcomes were pH, PaCO, PaO₂, oxygenation index (PaO₂/FiO₂), and the number of failure cases at 1, 12, and 24 hours after non-invasive respiratory support.. At all studied time points, after non-invasive respiratory support, PaCO₂, PaO₂ and oxygenation index were significantly (p < 0.05) better in the nasal DuoPAP group compared with nasal CPAP group. In addition, rates of failure of assisted ventilation (respectively, 4.44% vs. 22.50%) and the occurrence of apnea (13.33% vs. 32.50%) were significantly (p < 0.05) better in the nasal DuoPAP group. Other parameters (such as duration of noninvasive ventilation, number of retinopathies of premature children, intraventricular hemorrhages, or periventricular leukomalacias) were comparable between both non-invasive regimen.. Nasal DuoPAP better improves oxygenation, reduces CO₂ retention, and diminishes the need for invasive mechanical ventilation and complications in the treatment of NRDS.

Topics: Blood Gas Analysis; Continuous Positive Airway Pressure; Female; Humans; Hypercapnia; Infant, Newborn; Infant, Premature; Infant, Premature, Diseases; Infant, Very Low Birth Weight; Male; Nose; Respiratory Distress Syndrome, Newborn; Treatment Outcome

To evaluate the short-term physiologic effects of two settings of nasal pressure-support ventilation (NPSV) in stable COPD patients with chronic hypercapnia.. Randomized controlled physiologic study.. Lung function units and outpatient clinic of two affiliated pulmonary rehabilitation centers.. Twenty-three patients receiving domiciliary nocturnal NPSV for a mean (+/- SD) duration of 31 +/- 20 months.. Evaluation of arterial blood gases, breathing pattern, respiratory muscles, and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn) during both unassisted and assisted ventilation. Two settings of NPSV were randomly applied for 30 min each: (1) usual setting (U), the setting of NPSV actually used by the individual patient at home; and (2) physiologic setting (PHY), the level of inspiratory pressure support (IPS) and external positive end-expiratory pressure (PEEPe) tailored to patient according to invasive evaluation of respiratory muscular function and mechanics.. All patients tolerated NPSV well throughout the procedure. Mean U was IPS, 16 +/- 3 cm H(2)O and PEEPe, 3.6 +/- 1.4 cm H(2)O; mean PHY was IPS, 15 +/- 3 cm H(2)O and PEEPe, 3.1 +/- 1.6 cm H(2)O. NPSV was able to significantly (p < 0.01) improve arterial blood gases independent of the setting applied. When compared with spontaneous breathing, both settings induced a significant increase in minute ventilation (p < 0.01). Both settings were able to reduce the diaphragmatic pressure-time product, but the reduction was significantly greater with PHY (by 64%; p < 0.01) than with U (56%; p < 0.05). Eleven of 23 patients (48%) with U and 7 of 23 patients (30%) with PHY showed ineffective efforts (IE); the prevalence of IE (20 +/- 39% vs 6 +/- 11% of their respiratory rate with U and PHY, respectively) was statistically different (p < 0.05).. In COPD patients with chronic hypercapnia, NPSV is effective in improving arterial blood gases and in unloading inspiratory muscles independent of whether it is set on the basis of patient comfort and improvement in arterial blood gases or tailored to a patient's respiratory muscle effort and mechanics. However, setting of inspiratory assistance and PEEPe by the invasive evaluation of lung mechanics and respiratory muscle function may result in reduction in ineffective inspiratory efforts. These short-term results must be confirmed in the long-term clinical setting.

Topics: Aged; Carbon Dioxide; Chronic Disease; Diaphragm; Female; Follow-Up Studies; Home Care Services; Humans; Hypercapnia; Inhalation; Lung; Lung Diseases, Obstructive; Male; Maximal Voluntary Ventilation; Nose; Oxygen; Positive-Pressure Respiration; Positive-Pressure Respiration, Intrinsic; Pressure; Respiration; Respiratory Mechanics; Respiratory Muscles

Respiratory failure is the commonest cause of death in patients with Duchenne muscular dystrophy (DMD). Life expectancy is less than one year once diurnal hypercapnia develops. This study examines the effects of nasal intermittent positive pressure ventilation (NIPPV) on survival in symptomatic Duchenne patients with established ventilatory failure.. Nocturnal NIPPV was applied in 23 consecutive patients with DMD of mean (SD) age 20.3 (3.4) years who presented with diurnal and nocturnal hypercapnia.. One year and five year survival rates were 85% (95% CI 69 to 100) and 73% (95% CI 53 to 94), respectively. Early changes in arterial blood gas tensions following NIPPV occurred with mean (SD) PO2 increasing from 7.6 (2.1) kPa to 10.8 (1.3) kPa and mean (SD) PCO2 falling from 10.3 (4.5) kPa to 6.1 (1.0) kPa. Improvements in arterial blood gas tensions were maintained over five years. Health perception and social aspects of SF-36 health related quality of life index were reported as equivalent to other groups with nonprogressive disorders using NIPPV.. Nasal ventilation is likely to increase survival in hypercapnic patients with Duchenne muscular dystrophy and should be considered as a treatment option when ventilatory failure develops.

Topics: Adolescent; Adult; Carbon Dioxide; Follow-Up Studies; Home Care Services; Humans; Hypercapnia; Intermittent Positive-Pressure Ventilation; Male; Muscular Dystrophies; Nose; Oxygen; Partial Pressure; Quality of Life; Respiratory Insufficiency

Non-invasive ventilation has been used in chronic respiratory failure due to chronic obstructive pulmonary disease (COPD), but the effect of the addition of nasal positive-pressure ventilation to long-term oxygen therapy (LTOT) has not been determined. We report a randomized crossover study of the effect of the combination of nasal pressure support ventilation (NPSV) and domiciliary LTOT as compared with LTOT alone in stable hypercapnic COPD. Fourteen patients were studied, with values (mean +/- SD) of Pao2 of 45.3 +/- 5.7 mm Hg, PaCO2 of 55.8 +/- 3.6 mm Hg, and FEV1 of 0.86 +/- 0.32 L. A 4 wk run-in period (on usual therapy) was followed by consecutive 3-mo periods of: (1) oxygen therapy alone, and (2) oxygen plus NPSV in randomized order. Assessments were made during run-in and at the end of each study period. There were significant improvements in daytime arterial PaO2 and PaCO2, total sleep time, sleep efficiency, and overnight PaCO2 following 3 mo of oxygen plus NPSV as compared with run-in and oxygen alone. Quality of life with oxygen plus NPSV was significantly better than with oxygen alone. The degree of improvement in daytime PaCO2 was correlated with the improvement in mean overnight PaCO2. Nasal positive-pressure ventilation may be a useful addition to LTOT in stable hypercapnic COPD.

Topics: Aged; Carbon Dioxide; Cross-Over Studies; Exercise Test; Female; Follow-Up Studies; Forced Expiratory Volume; Humans; Hypercapnia; Hypoxia; Lung Diseases, Obstructive; Male; Middle Aged; Nose; Oxygen; Oxygen Inhalation Therapy; Positive-Pressure Respiration; Quality of Life; Respiratory Insufficiency; Sleep; Vital Capacity

Topics: Adult; Female; Functional Residual Capacity; Humans; Hypercapnia; Hypoxia; Intubation, Intratracheal; Male; Middle Aged; Mouth; Nose; Oxygen; Oxygen Inhalation Therapy; Oxygenators

Topics: Humans; Hypercapnia; Noninvasive Ventilation; Nose; Pulmonary Disease, Chronic Obstructive; Respiratory Insufficiency

Topics: Humans; Hypercapnia; Noninvasive Ventilation; Nose; Pulmonary Disease, Chronic Obstructive; Respiratory Insufficiency

To determine whether the presence of nasal flaring is a clinical sign of respiratory acidosis in patients attending emergency departments for acute dyspnea.. Single-center, prospective, observational study of patients aged over 15 requiring urgent attention for dyspnea, classified as level II or III according to the Andorran Triage Program and who underwent arterial blood gas test on arrival at the emergency department. The presence of nasal flaring was evaluated by two observers. Demographic and clinical variables, signs of respiratory difficulty, vital signs, arterial blood gases and clinical outcome (hospitalization and mortality) were recorded. Bivariate and multivariate analyses were performed using logistic regression models.. The sample comprised 212 patients, mean age 78years (SD=12.8), of whom 49.5% were women. Acidosis was recorded in 21.2%. Factors significantly associated with the presence of acidosis in the bivariate analysis were the need for pre-hospital medical care, triage level II, signs of respiratory distress, presence of nasal flaring, poor oxygenation, hypercapnia, low bicarbonates and greater need for noninvasive ventilation. Nasal flaring had a positive likelihood ratio for acidosis of 4.6 (95% CI 2.9-7.4). In the multivariate analysis, triage level II (aOR 5.16; 95% CI: 1.91 to 13.98), the need for oxygen therapy (aOR 2.60; 95% CI: 1.13-5.96) and presence of nasal flaring (aOR 6.32; 95% CI: 2.78-14.41) were maintained as factors independently associated with acidosis.. Nasal flaring is a clinical sign of severity in patients requiring urgent care for acute dyspnea, which has a strong association with acidosis and hypercapnia.

Topics: Acidosis, Respiratory; Aged; Aged, 80 and over; Blood Gas Analysis; Case-Control Studies; Dyspnea; Emergency Service, Hospital; Female; Humans; Hypercapnia; Logistic Models; Male; Middle Aged; Multivariate Analysis; Noninvasive Ventilation; Nose; Oxygen Inhalation Therapy; Physical Examination; Prospective Studies; Severity of Illness Index; Triage

High flow nasal cannulas (HFNCs) provide humidified oxygen at higher flow rates and higher FiO2s than conventional delivery devices and are typically used in special care units. There is limited information on their use in general hospital settings.. The medical records of all patients who were treated with HFNC during the calendar year 2014 were retrospectively reviewed to collect information on age, sex, indications, arterial blood gases when available, O2 saturations and outcomes.. One hundred six patients received oxygen supplementation by HFNC in their hospital in 2014. The average age was 61.6 ± 16.2 years; 62 patients were men. The indications for HFNC included dyspnea (1 patient), hypoxemic respiratory failure (101 patients) and hypercapneic respiratory failure (4 patients). The PaO2 increased from 68.2 ± 16.3 mm Hg to 83.1 ± 32.2 mm Hg (N = 32, P = 0.02) with the change to HFNC. The O2 saturation increased from 93.1 ± 4.5% to 95.1 ± 3.0% (N = 106, P = 0.00015). The mean duration of use was 4.3 ± 3.7 days. Sixty-five patients did not require intubation or noninvasive ventilation (NIV). Sixteen required NIV, 16 required intubation and 9 required both. The overall mortality was 15%.. HFNC oxygen therapy is used relatively frequently in their hospital on surgical and medical services. PaO2s and O2 saturations improved when patients were switched to this mode of oxygenation, but some patients subsequently required NIV and/or intubation. Patients on HFNC need careful monitoring for deterioration in their respiratory status.

Topics: Adult; Aged; Aged, 80 and over; Catheters; Female; Humans; Hypercapnia; Male; Middle Aged; Noninvasive Ventilation; Nose; Oxygen; Oxygen Inhalation Therapy; Positive-Pressure Respiration; Respiratory Insufficiency; Retrospective Studies; Tertiary Healthcare

The traditional method used to evaluate escape masks has been to examine the composition of the inspired gas, although arterial carbon dioxide (CO2) and oxygen (O2) would be more relevant physiological parameters. The recent development of reliable, fast-responding transcutaneous CO2 detectors makes it possible to evaluate arterial CO2 and O2 saturation. The CAPS 2000 escape mask was designed to protect the head and respiratory system from chemical or biological attack. The question arises of whether there might be a risk of dangerous hypoxia-hypercapnia in rebreathing from the mask because of leakage of the expired gas from the nose-cup into the hood, although theoretical considerations rule this out. We studied a worst case scenario.. Nine subjects wore the CAPS 2000 for 15 minutes after removal of the inspiratory valves. A mass spectrometer and transcutaneous sensor were used to measure O2 and CO2, arterial O2 saturation, and arterial partial pressure of CO2 (PCO2).. Blood oxygen saturation decreased from an initial value of 98.4% to 96.2% at 2 minutes, subsequently rising and stabilizing at a level similar to control. Subcutaneous PCO2 rose from the control level of 36 to 43 torr after 5 minutes, then decreased to 42 torr and stabilized at that level. Inspired PO2 dropped from 21% to 16% at 3 to 4 minutes, rose to 17% at 8 minutes, and stabilized thereafter. Inspired PCO2 rose to 3% in the first minute and continued to rise to 3.5% at 3 minutes, after which it slowly decreased to 3% and stabilized at that level.. The transcutaneous CO2 detector provided a true indication of the physiological state of the subject, and these parameters are sufficient on their own for the evaluation of breathing masks. CO2 and O2 did not reach dangerous levels with the inspiratory valves removed from the CAPS 2000 mask.

Topics: Adult; Aged; Blood Gas Analysis; Carbon Dioxide; Equipment Design; Female; Humans; Hypercapnia; Male; Masks; Middle Aged; Military Medicine; Military Personnel; Nose; Oxygen; Pulmonary Gas Exchange; Respiration; Young Adult

To determine the optimal level of nasal continuous positive airway pressure (nCPAP) in infants with severe hypercapnic viral bronchiolitis as assessed by the maximal unloading of the respiratory muscles and improvement of breathing pattern and gas exchange.. A prospective physiological study in a tertiary paediatric intensive care unit (PICU). Breathing pattern, gas exchange, intrinsic end expiratory pressure (PEEPi) and respiratory muscle effort were measured in ten infants with severe hypercapnic viral bronchiolitis during spontaneous breathing (SB) and three increasing levels of nCPAP.. During SB, median PEEPi was 6 cmH(2)O (range 3.9-9.2 cmH(2)O), median respiratory rate was 78 breaths/min (range 41-96), median inspiratory time/total duty cycle (T (i)/T (tot)) was 0.45 (range 0.40-0.48) and transcutaneous carbon dioxide pressure (P (tc)CO(2)) was 61.5 mmHg (range 50-78). In all the infants, an nCPAP level of 7 cmH(2)O was associated with the greatest reduction in respiratory effort with a mean reduction in oesophageal and diaphragmatic pressure swings of 48 and 46%, respectively, and of the oesophageal and diaphragmatic pressure time product of 49 and 56%, respectively. During nCPAP, median respiratory rate decreased to 56 breaths/min (range 39-108, p < 0.05), median T (i)/T (tot) decreased to 0.40 (range 0.34-0.44, p < 0.50) and P (tc)CO(2) decreased to 49 mmHg (range 35-65, p < 0.05). Only one infant with associated bacterial pneumonia required intubation and all the infants were discharged alive from the PICU after a median stay of 5.5 (range 3-27 days).. In infants with hypercapnic respiratory failure due to acute viral bronchiolitis, an nCPAP level of 7 cmH(2)O is associated with the greatest unloading of the respiratory muscles and improvement of breathing pattern, as well as a favourable short-term clinical outcome.

Topics: Bronchiolitis, Viral; Continuous Positive Airway Pressure; Female; France; Humans; Hypercapnia; Infant; Intensive Care Units, Pediatric; Male; Nose; Prospective Studies; Pulmonary Gas Exchange; Respiration; Respiratory Syncytial Virus Infections; Respiratory Syncytial Viruses; Severity of Illness Index

This study was aimed to examine the short- and long-term effects of nasal continuous positive airway pressure (CPAP) on the chemosensitivity to hypoxia and hypercapnia in the patients with obstructive sleep apnea (OSA). Awake ventilatory responses to hypoxia and hypercapnia were examined in 28 patients (3 female) with moderate to severe OSA. All these tests were examined before and after 2 weeks of nasal CPAP. In 10 patients these tests were repeated after 3-6 months of nasal CPAP. All were also tested for spirometry and arterial blood gas analysis. Patients were middle-aged (48.9 +/- 9.9 years) and their mean apnea-hypopnea index was 58.3 +/- 20.4/hour. After 2 week of nasal CPAP, PaO2 significantly increased (77.7 +/- 11.8 vs. 84.6 +/- 9.8 mmHg) and PaCO2 significantly decreased (44.9 +/- 3.8 vs. 42.3 +/- 3.7 mmHg). The ventilatory response to hypoxia significantly decreased (0.80 +/- 0.51 vs. 0.61 +/- 0.51 liter/min/%) whereas the ventilatory response to hypercapnia significantly increased after 2 weeks (1.47 +/- 0.73 vs. 1.80 +/- 0.76 liter/min/mmHg). Similar findings were also observed after 3-6 months of nasal CPAP in 10 OSA patients. Nasal CPAP treatment can alter the ventilatory responses in patients with OSA.

Topics: Blood Gas Analysis; Female; Forced Expiratory Volume; Humans; Hypercapnia; Hypoxia; Male; Middle Aged; Nose; Positive-Pressure Respiration; Pulmonary Ventilation; Sleep Apnea, Obstructive; Spirometry

Exercise (Ex) and hypercapnia (HC) both lead to increases in ventilation and upper airway muscle (UAM) activity. To determine whether different breathing routes (nasal vs. oral) or stimuli produced differential UAM activation, electromyographic (EMG) activity of the alae nasi (AN) and genioglossus (GG) were measured in seven normal subjects seated on a bicycle ergometer. Subjects performed paired runs during both progressive Ex and HC while breathing through the nose alone (N) or the mouth alone (O). During hyperpnea, AN EMG was greater when the subjects were breathing via N [81 +/- 6% maximum (HC) and 69 +/- 7% maximum (Ex)] than when they were breathing via O [30 +/- 5% maximum (HC) and 27 +/- 5% maximum (Ex); both P < 0.01], whereas the GG EMG did not differ between N and O. Both AN and GG EMG were similar for Ex and HC when the subjects were breathing via the same route. We conclude that UAM activation was independent of the nature of the stimulus. However, the AN muscle but not the GG muscle demonstrated breathing-route dependence of activity.

Topics: Adult; Ergometry; Humans; Hypercapnia; Male; Mouth; Muscles; Nose; Oxygen Consumption; Physical Exertion; Pulmonary Ventilation; Respiration

An effective treatment of advanced states of chronic obstructive pulmonary disease (COPD) has yet to be established. We report the case of a COPD patient with severe hypoxemia (pO2 = 32.0 mm Hg) and hypercapnia (pCO2 = 90.0 mm Hg) who was successfully treated for 8 months with nasal intermittent positive-pressure ventilation (NIPPV) plus supplemental O2 in a domiciliary treatment. The reduction of hypoxemia parallel to the alleviation of hypercapnia reversed the patient's continuously declining condition.

Topics: Blood Gas Analysis; Home Care Services; Humans; Hypercapnia; Intermittent Positive-Pressure Ventilation; Lung Diseases, Obstructive; Male; Middle Aged; Nose; Oxygen Inhalation Therapy

Long-term oxygen therapy improves survival in patients with chronic obstructive pulmonary disease (COPD), though the addition of assisted ventilation may control the nocturnal hypoventilation and correct blood gases. Although early experiences with ventilation in COPD was disappointing, the introduction of nasal positive pressure ventilation has been shown to improve blood gases, sleep quality and quality of life. The improvement in blood gases was related to the reduction of overnight Pa,CO2 with ventilation. Compliance with nasal ventilation was increased, compared to that with earlier modes of ventilation. Nasal ventilation is beneficial in carefully selected patients with hypercapnic COPD.

Topics: Humans; Hypercapnia; Lung Diseases, Obstructive; Masks; Nose; Positive-Pressure Respiration; Treatment Outcome

We have recently observed obstructive apneas during nasal intermittent positive-pressure ventilation (nIPPV) and suggested that they were due to hypocapnia-induced glottic closure. To confirm this hypothesis, we studied seven healthy subjects and submitted them to nIPPV while their glottis was continuously monitored through a fiber-optic bronchoscope. During wakefulness, we measured breath by breath the widest inspiratory angle formed by the vocal cords at the anterior commissure along with several other indexes. Mechanical ventilation was progressively increased up to 30 l/min. In the absence of diaphragmatic activity, increases in delivered minute ventilation resulted in progressive narrowing of the vocal cords, with an increase in inspiratory resistance and a progressive reduction in the percentage of the delivered tidal volume effectively reaching the lungs. Adding CO2 to the inspired gas led to partial widening of the glottis in two of three subjects. Moreover, activation of the diaphragmatic muscle was always associated with a significant inspiratory abduction of the vocal cords. Sporadically, complete adduction of the vocal cords was directly responsible for obstructive laryngeal apneas and cyclic changes in the glottic aperture resulted in waxing and waning of tidal volume. We conclude that in awake humans passive ventilation with nIPPV results in vocal cord adduction that depends partly on hypocapnia, but our results suggest that other factors may also influence glottic width.

Topics: Adult; Diaphragm; Female; Glottis; Humans; Hypercapnia; Hyperventilation; Male; Nose; Positive-Pressure Respiration; Reference Values

We have previously observed that, in normal awake subjects passively hyperventilated with intermittent positive-pressure ventilation delivered through nasal access (nIPPV), the glottis could interfere with the ventilation. We report on data obtained in the same subjects during stable sleep. In all cases, the glottis was continuously observed through a fiber-optic bronchoscope, and other indexes were also continuously recorded. Mechanical ventilation was progressively increased up to 30 l/min. We have observed during passive nIPPV in stable sleep that increases in delivered minute ventilation (VEd) resulted in progressive narrowing of the glottic aperture, with increases in inspiratory resistance and progressive reductions in the percentage of the delivered tidal volume effectively reaching the lungs. For a given level of VEd, comparisons showed that the glottis was significantly narrower during sleep than during wakefulness and that the glottis was significantly narrower during stage 2 than during stages 3/4 non-rapid-eye-movement sleep. Moreover, when CO2 is added to the inspired air, glottic aperture increased in five of nine trials without changes in sleep stage. We also observed a significant negative correlation between glottic width and the VED, independent of the CO2 level. We conclude that during nIPPV glottis narrowing results in a decrease in the proportion of the delivered tidal volume reaching the lungs.

Topics: Adult; Apnea; Carbon Dioxide; Female; Glottis; Humans; Hypercapnia; Hyperventilation; Male; Nose; Positive-Pressure Respiration; Reference Values; Respiration; Sleep; Sleep Stages; Tidal Volume; Wakefulness

Laryngeal airway resistance (Rlar) was measured in eight normal adult humans during progressive hyperoxic hypercapnia. In most subjects, the translaryngeal pressure-flow relationship appeared linear under normocapnic conditions. During hypercapnia, the pressure-flow relationship on inspiration and expiration was curvilinear with increasing translaryngeal pressure associated with progressively smaller increments in flow. Translaryngeal pressure-flow relationships at different CO2 levels were compared over their common flow ranges by performing a least-squares linear regression on data throughout inspiration and expiration. During normocapnia, the mean slope, i.e., mean Rlar, was 0.50 +/- 0.21 (SD) cmH2O.l-1.s. A moderately significant decrease in Rlar was present at 9% end-tidal CO2 (P = 0.08). In a separate series of experiments, subjects breathed oxygen- and helium-based gas mixtures through a face mask attached to a pneumotachograph. Data analysis over the flow range present during normocapnia revealed no difference in Rlar between nose and mouth breathing and similar decreases in Rlar under hypercapnic conditions with the oxygen- and helium-based gas mixtures. The decrease in Rlar from normocapnic to hypercapnic conditions found over common, but relatively low, ranges of flow predicts that even greater increases in Rlar would occur at high flow rates in the absence of increasing glottic aperture.

Topics: Adult; Airway Resistance; Female; Humans; Hypercapnia; Larynx; Male; Mouth Breathing; Nose; Pressure; Pulmonary Ventilation; Reference Values; Respiration

To evaluate the efficacy of nasal mechanical ventilation in patients with chronic obstructive pulmonary disease and hypercapnic respiratory failure and to identify predictors of success or failure of nasal mechanical ventilation.. Prospective case series.. Medical intensive care unit in Veterans Administration Medical Center.. Twelve chronic obstructive pulmonary disease patients treated during 14 episodes of hypercapnic respiratory failure.. Nasal mechanical ventilation in addition to conventional therapy to treat hypercapnic respiratory failure. Patients underwent nasal mechanical ventilation for at least 30 mins, or longer if the therapy was tolerated. Responses to therapy and arterial blood gases were monitored.. Half of the episodes were successfully treated with nasal mechanical ventilation. There were no differences in age, prior pulmonary function, baseline arterial blood gases, admission arterial blood gases, or respiratory rate between those patients successfully treated and those patients who failed nasal mechanical ventilation. Unsuccessfully treated patients appeared to have a greater severity of illness than successfully treated patients, as indicated by a higher Acute Physiology and Chronic Health Evaluation II score (mean 21 +/- 4 [SD] vs. 15 +/- 4; p = .02). Unsuccessfully treated patients were edentulous, had pneumonia or excess secretions, and had pursed-lip breathing, factors that prevented adequate mouth seal and contributed to greater mouth leaks than in successfully treated patients (the mean volume of the mouth leak was 314 +/- 107 vs. 100 +/- 70 mL; p < .01). Successfully treated patients were able to adapt more rapidly to the nasal mask and ventilator, with greater and more rapid reduction in PaCO2, correction of pH, and reduction in respiratory rate.. Patients who failed nasal mechanical ventilation appeared to have a greater severity of illness; they were unable to minimize the amount of mouth leak (because of lack of teeth, secretions, or breathing pattern) and were unable to coordinate with the ventilator. These features may allow identification of poor candidates for nasal mechanical ventilation, avoiding unnecessary delays in endotracheal intubation and mechanical ventilation.

Topics: Acute Disease; Aged; Blood Gas Analysis; Female; Forced Expiratory Volume; Humans; Hypercapnia; Lung Diseases, Obstructive; Male; Masks; Nose; Positive-Pressure Respiration; Prospective Studies; Respiration; Respiratory Insufficiency; Severity of Illness Index; Survival Rate; Tidal Volume; Treatment Outcome; Vital Capacity

1. The influence of the upper airway on the ventilatory and arousal responses to hypercapnia in wakefulness and sleep was investigated using a chronic animal model. 2. Experiments were performed in five unrestrained dogs trained to sleep naturally in the laboratory. The animal rebreathed through a chronic tracheostoma (thus excluding the upper airway from the breathing circuit), or through the snout (intact upper airway). Resistance to breathing and volume of dead space during quiet tracheal breathing were matched to those in quiet nasal breathing during wakefulness and sleep. CO2 rebreathing tests were performed during wakefulness, rapid eye movement (REM) and non-REM (NREM) sleep, during nasal and tracheal breathing. 3. The ventilatory response to hypercapnia was significantly lower in nasal breathing compared with tracheal breathing, in all behavioural states. This was due to a smaller tidal volume and lower breathing frequency. 4. The ventilatory response to CO2 was lowest during REM sleep, irrespective of route used for breathing. 5. Alveolar partial pressure of CO2 (PA,CO2) level at arousal was identical in NREM nasal and tracheal rebreathing tests. Differences in PA,CO2 levels at arousal between NREM and REM sleep were not significant in nasal tests and only marginally different during tracheal breathing. 6. We conclude that nasal breathing influences the hypercapnic ventilatory response in wakefulness and sleep, and that the presence of CO2 in the upper airway does not affect arousal in NREM and REM sleep.

Topics: Animals; Arousal; Dogs; Electroencephalography; Hypercapnia; Nose; Oxygen; Regression Analysis; Respiration; Respiratory Mechanics; Sleep; Sleep, REM; Trachea

This paper describes the use of a nasal mask to deliver intermittent positive pressure ventilation to treat chronic respiratory failure in one patient with severe kyphoscoliosis. After two months of overnight nasal ventilation at home the patient achieved normal blood gases, showed improved inspiratory muscle strength, effort tolerance and was able to return to work. Intermittent nasal ventilation is a safe and effective ventilatory support modality for some patients with hypercapnic respiratory failure.

Topics: Adult; Chronic Disease; Follow-Up Studies; Humans; Hypercapnia; Inspiratory Capacity; Lung; Male; Masks; Nose; Positive-Pressure Respiration; Pressure; Respiratory Insufficiency; Respiratory Mechanics; Tidal Volume

We reviewed the Mayo Clinic experience with nocturnal nasal ventilation (NNV) and retrospectively assessed the clinical benefits, patient compliance, and complications. NNV had been instituted in 26 patients with daytime hypercapnia and nocturnal hypoventilation due to neuromuscular diseases or chronic obstructive pulmonary disease. After initiation of NNV, 21 of 26 patients continued to use this treatment regularly (81% compliance rate) and considered their life-style improved. In this subset of patients, the arterial partial pressure of carbon dioxide during unassisted breathing decreased from 64 +/- 13 to 51 +/- 7 mm Hg, and the arterial partial pressure of oxygen increased from 58 +/- 12 to 68 +/- 8 mm Hg. No significant change was noted in the forced vital capacity or maximal respiratory pressures. Four of the five patients in whom NNV had been discontinued cited discomfort related to the mask or severity and poor prognosis of the underlying illness as reasons for cessation of treatment. We conclude that NNV is well tolerated by most patients and may improve alveolar ventilation and arterial oxygenation in patients with chronic respiratory failure.

Topics: Adolescent; Adult; Aged; Carbon Dioxide; Chronic Disease; Female; Humans; Hypercapnia; Lung Diseases, Obstructive; Male; Middle Aged; Nose; Oxygen; Patient Compliance; Positive-Pressure Respiration; Pulmonary Gas Exchange; Respiratory Insufficiency; Respiratory Muscles; Retrospective Studies

Topics: Equipment Design; Humans; Hypercapnia; Nose; Respiration, Artificial; Respiratory Insufficiency; Ventilators, Mechanical

Topics: Female; Humans; Hypercapnia; Lung Diseases, Obstructive; Nose; Oxygen Inhalation Therapy

Nineteen subjects with the obstructive sleep apnea syndrome (10 with daytime arterial CO2 tension 44 mm Hg or higher) were treated with long-term nocturnal continuous positive airway pressure. The ventilatory response to CO2 (Read's method) was measured in triplicate prior to treatment and after 1, 2, 3, 7, and 14 or more nights of therapy. Seven subjects were tested on at least 4 occasions. For each test, slope of the response line and position of the response line (ventilation at a PCO2 of 60 mm Hg) were calculated. The subjects with initial high daytime CO2 showed no change in slope of response with treatment but showed a progressive increase in ventilation at any given degree of PCO2. Ventilation at a PCO2 of 60 mm Hg increased from a mean of 20.0 +/- 1.3 SEM L/min by 8.0 +/- 2.5 SEM L/min after 2 nights of therapy (p less than 0.05, two-way analysis of variance), and by 16.2 +/- 1.9 L/min after 2 wk or more (p less than 0.01). On average, there was no significant change in either slope or position of response in the subjects with initially normal daytime PCO2. We conclude that airway obstruction in sleep (in obstructive sleep apnea syndrome) leads in some subjects to respiratory failure in the daytime, with a left shift in the ventilatory response to CO2, and that this changes is usually reversible during the next several days.

Topics: Blood Gas Analysis; Carbon Dioxide; Humans; Hypercapnia; Masks; Nose; Partial Pressure; Positive-Pressure Respiration; Respiration; Sleep Apnea Syndromes; Sleep, REM; Time Factors

Severe nocturnal hypoxemia may occur in patients with respiratory muscle weakness caused by neuromuscular disorders. Negative pressure ventilators may be partially effective in these patients but can cause upper airway obstructive apneas. We examined the effectiveness of positive pressure ventilation through a nose mask in preventing nocturnal hypoxemia and compared it with negative pressure systems. We reasoned that nasal positive pressure would provide stability for the upper airway. Five patients with neuromuscular disorders underwent a series of all-night sleep studies under control conditions, negative pressure ventilation, and positive pressure ventilation through a comfortable nose mask. Sleep staging and respiratory variables were monitored during all studies. Daytime awake lung function, respiratory muscle strength, and arterial blood gases were also measured. The severe hypoxemia and hypercapnia that occurred under control conditions were prevented by positive pressure ventilation through a nose mask. Negative pressure ventilation improved NREM ventilation in all patients, but did not prevent severe oxyhemoglobin desaturation, which occurred during REM sleep. Negative pressure ventilation appears to contribute to upper airways obstruction during REM sleep as evidenced by cessation of air flow, reduced chest wall movements, falls in arterial oxyhemoglobin saturation, and hypercapnia. With treatment, daytime PaO2 improved from a mean of 70 to 83 mm Hg, and PaCO2 decreased from a mean of 61 to 46 mm Hg. We conclude that nasally applied positive pressure ventilation is a highly effective method of providing nocturnal assisted ventilation because it stabilizes the oropharyngeal airway.

Topics: Evaluation Studies as Topic; Humans; Hypercapnia; Hypoxia; Masks; Neuromuscular Diseases; Nose; Positive-Pressure Respiration; Respiratory Insufficiency; Sleep Apnea Syndromes; Sleep, REM

The relationship between the electrical and mechanical activity of the nasal dilator muscle was assessed in 8 pentobarbital-anesthetized, tracheostomized, supine dogs. Alae nasi electromyograms (EMGs) were recorded with bipolar fine wire electrodes, and respiratory changes in muscle length were recorded contralaterally using sonomicrometry. During both resting and stimulated breathing, the intrabreath pattern of muscle shortening closely paralleled the intrabreath pattern of EMG activity. Increases in both alae nasi EMG and alae nasi inspiratory shortening occurred in response to single-breath airway occlusions, brief periods of asphyxia, progressive hyperoxic hypercapnia, and intravenous nicotine sulfate administration. With all interventions, the increases in mechanical activation of the alae nasi paralleled the increases in alae nasi electrical activity. These results indicate that alae nasi EMGs, closely reflect respiratory changes in alae nasi length under conditions in which no mechanical load is placed in the nasal muscle.

Topics: Animals; Asphyxia; Dogs; Electromyography; Hypercapnia; Muscle Contraction; Nicotine; Nose; Respiration

Previous studies have shown that the arousal threshold to hypoxia, hypercapnia, and tracheal occlusions is greatly depressed in rapid-eye-movement (REM) sleep compared with slow-wave sleep (SWS). The aim of this study was to compare the arousal thresholds in SWS and REM sleep in response to an upper airway pressure stimulus. We compared the waking responses to tracheal (T) vs. nasal (N) occlusion in four unanesthetized, naturally sleeping dogs. The dogs either breathed through a tracheal fistula or through the snout using a fiberglass mask. A total of 295 T and 160 N occlusion tests were performed in SWS and REM sleep. The mean time to arousal during N and T tests was variable in the same dog and among the dogs. The mean time to arousal in SWS-tracheal occlusion was longer than that in N tests in only two of the four dogs. The total number of tests inducing arousal within the first 15 s of SWS-nasal occlusion tests was significantly more than that of T tests (N: 47%; T: 27%). There was a marked depression of arousal within the initial 15 s of REM sleep in T tests compared with N tests (N: 21%; T: 0%). The frequency of early arousals in REM tests was less than that of SWS for both N and T tests. The early arousal in N occlusion is in sharp contrast to the well-described depressed arousal responses to hypoxia, hypercapnia, and asphyxia. This pattern of arousal suggests that the upper airway mechanoreceptors may play an important role in the induction of an early arousal from nasal occlusion.

Topics: Airway Obstruction; Animals; Arousal; Asphyxia; Dogs; Hypercapnia; Hypoxia; Nose; Sleep; Sleep, REM; Trachea

Respiratory-related changes in length of the nasal dilator muscle, the alae nasi muscle, were measured using sonomicrometry in ten anesthetized (pentobarbital), tracheostomized, spontaneously breathing dogs. Piezoelectric crystals were inserted 7-25 mm apart along the direction of the alae nasi muscle fibers, and the effects of progressive hyperoxic hypercapnia and a peripheral and central chemoreceptor stimulant, nicotine (10-500 micrograms intravenously), were ascertained. The alae nasi shortened during inspiration in all animals, started to lengthen again towards the end of inspiration, returned to resting length during the first portion of expiration (Te-1), and remained at resting length for the remainder of expiration (Te-2). The amount of alae nasi inspiratory shortening was increased by occluding the airway for a single breath. Progressive hypercapnia caused progressive increases in the amount and velocity of nasal muscle inspiratory shortening during both unoccluded and occluded breaths; similar stimulatory effects on inspiratory shortening were seen following nicotine administration. Furthermore, both chemoreceptor stimulants caused a delay in the return of the muscle to its resting length during expiration, resulting in a significant increase in Te-1 relative to Te (Te-1/Te), and a greater amount of nasal muscle shortening to be present during Te-1. In some animals these agents also caused tonic shortening of the alae nasi, so that the muscle never returned to its resting length. These results suggest that inspiratory shortening of the alae nasi is inhibited by vagal inputs, but that chemoreceptor activation increases the amount of muscle shortening during both inspiration and early expiration.

Topics: Animals; Carbon Dioxide; Chemoreceptor Cells; Dogs; Hypercapnia; Muscles; Nicotine; Nose; Pulmonary Ventilation; Stimulation, Chemical; Tidal Volume

Carotid body-denervated (CBD) ponies have a less than normal increase in arterial PCO2 (PaCO2) when inspired CO2 (PICO2) is increased, even when pulmonary ventilation (VE) and breathing frequency (f) are normal. We studied six tracheostomized ponies to determine whether this change 1) might be due to increased alveolar ventilation (VA) secondary to a reduction in upper airway dead space (VD) or 2) is dependent on an upper airway sensory mechanism. Three normal and three chronic CBD ponies were studied while they were breathing room air and at 14, 28, and 42 Torr PICO2. While the ponies were breathing room air, physiological VD was 483 and 255 ml during nares breathing (NBr) and tracheostomy breathing (TBr), respectively. However, at elevated PICO2, mixed expired PCO2 often exceeded PaCO2; thus we were unable to calculate physiological VD using the Bohr equation. At all PICO2 in normal ponies, PaCO2 was approximately 0.3 Torr greater during NBr than during TBr (P less than 0.05). In CBD ponies this NBr-TBr difference was only evident while breathing room air and at 28 Torr PICO2. At each elevated PICO2 during both NBr and TBr, the increase in PaCO2 above control was always less in CBD ponies than in normal ponies (P less than 0.01). The VE-PaCO2, f-PaCO2, and tidal volume-PaCO2 relationships did not differ between NBr and TBr (P greater than 0.10) nor did they differ between normal and CBD ponies (P greater than 0.10). We conclude that the attenuated increase in PaCO2 during CO2 inhalation after CBD is not due to a relative increase in VA secondary to reducing upper airway VD.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arteries; Carbon Dioxide; Carotid Body; Denervation; Horses; Hypercapnia; Nose; Partial Pressure; Respiration; Respiratory Dead Space; Tracheotomy

We examined the electromyographic activity of the posterior cricoarytenoid (PCA) simultaneously with the alae nasi (AN) in response to increasing chemical drive in 5 normal, awake human subjects. During progressive isocapnic hypoxia the peak of the integrated PCA activity (EPCA) increased as a function of tidal volume (VT), and in 3 of the 5 subjects the residual variance of an exponential fit (of the form EPCA = A - Be-KVT, where A, B and K are constants) was significantly less than that of a linear regression. In the other 2 subjects the data were too noisy to detect a difference although a positive relationship was present. In contrast, during progressive hyperoxic hypercapnia we found a linear relationship between EPCA and VT (r = 0.84 +/- 0.14) in all subjects over a comparable ventilatory range. The peak of the integrated AN activity (EAN) increased linearly with increasing VT during both hypoxia (r = 0.90 +/- 0.08) and hypercapnia (r = 0.89 +/- 0.12). Tonic EPCA also increased as a function of VT during both hypoxia and hypercapnia and at a VT of 1.6 L constituted 26 +/- 6% and 24 +/- 8% of the respective maximal peak EPCA. During hypoxia the relative increase in tonic EPCA occurred at a lower VT than during hypercapnia. Our results suggest that there are qualitative differences in the response of the PCA to increased chemical drive between hypoxia and hypercapnia. This is consistent with differing inputs to some upper airway motoneurones from central and peripheral chemoreceptors.

Topics: Adult; Electromyography; Humans; Hypercapnia; Hypoxia; Laryngeal Muscles; Male; Middle Aged; Muscles; Nose; Respiration; Rest; Tidal Volume

To define the relationship between central control of upper airway muscles and respiratory muscle function, the electromyographic responses of the dilator nares muscles to stimulation of chemoreceptors and pulmonary receptors were studied in six anesthetized dogs. Only at maximal levels of hypoxia was the inspiratory activity of the dilator nares significantly increased. Hypercapnic stimulation increased the inspiratory activity with each incremental increase in CO2. Pulmonary stretch receptor stimulation produced by lung inflation inhibited dilator nares activity. Pulmonary irritant receptor stimulation by intravenously administered histamine increased dilator nares activity, as did pulmonary J receptor stimulation by the intravenous administration of capsaicin.

Topics: Animals; Capsaicin; Carbon Dioxide; Chemoreceptor Cells; Dogs; Electromyography; Facial Muscles; Histamine; Hypercapnia; Hypoxia; Mechanoreceptors; Nose; Pulmonary Stretch Receptors; Stimulation, Chemical

The effect of augmented breaths on the electrical activity of upper airway (UAW) muscles was studied in fourteen spontaneously breathing anesthetized dogs. Moving average traces of the electrical activity recorded from the genioglossus (GG), the posterior cricoarytenoid (PCA), and the alar portion of the nasalis muscle (AN) were compared to tracings of diaphragm electrical activity. During augmented breaths the electrical activity of the diaphragm showed the characteristic biphasic pattern previously described: an initial phase following the contour of a normal breath (phase I) and an augmented phase arising near the crest of the initial phase (phase II). During all augmented breaths, the GG, PCA and AN showed the same biphasic pattern as the diaphragm. The normally rounded shape of UAW muscle EMG activity during control breaths changed to a more sharply peaked form during the second phase of the augmented breath. Onset of activity of all UAW muscles studied preceded that of the diaphragm; during control breaths, the average interval was 0.29 sec for the PCA, 0.25 sec for the GG and 0.14 sec for the AN (P less than 0.05). The amount of pre-activation was decreased to less than 0.10 sec during the second phase of the augmented breath. The slopes and amplitudes of phase I were similar to that of control breaths. The peak EMG activity of the augmented breath was 214% of the control breaths for the diaphragm, 247% for the GG, 168% for the AN and 161% for the PCA (P less than 0.005 for GG, P less than 0.001 for the others). During hyperoxic hypercapnia the slopes and amplitudes of phase II remained nearly constant for all four muscles, whereas the slopes and amplitudes of phase I changed with the chemical drive just as in control breaths. UAW resistance, recorded in five additional spontaneously breathing anesthetized dogs, was 32% less during inspiration than expiration during control breaths, and 31% less during phase I of augmented breaths; there was a further 18% decrease during phase II of augmented breaths (P less than 0.001). The results suggest that mechanisms responsible for augmented breaths act similarly on upper airway muscles and the diaphragm.

Topics: Airway Resistance; Animals; Diaphragm; Dogs; Electromyography; Hypercapnia; Laryngeal Muscles; Mouth; Muscle Contraction; Muscles; Nose; Respiration

A coordinated activation of upper airway and chest wall muscles may be crucial in maintaining airway patency and ventilation. The alae nasi (AN) and diaphragm (DIA) electromyograms (EMG) were recorded with surface electrodes in 17 unsedated healthy preterm infants during both active (AS) and quiet sleep (QS). Airflow was measured via a nasal mask pneumotachograph and integrated to obtain tidal volume. Studies were performed during inhalation of room air and mixtures of 2 and 4% CO2 in air. In room air, phasic AN EMG accompanied 45 +/- 7% of breaths during AS compared with 14 +/- 5% of breaths during QS (P less than 0.001); however, with inhalation of 4% CO2 the incidence of AN EMG increased to comparable levels in both sleep states. During room air breathing onset of AN EMG preceded that of the DIA EMG and inspiratory airflow by 41 +/- 8 ms (P less than 0.01) and 114 +/- 29 ms (P less than 0.05), respectively. Peak AN activity preceded peak DIA activity by 191 +/- 36 ms (P less than 0.01). Alteration in sleep state or increasing chemical drive did not significantly alter these temporal relationships. Nevertheless, with each increase in end-tidal CO2, peak DIA EMG and tidal volume increased while peak AN EMG only showed a consistent increase during 4% CO2 inhalation. We conclude that although there exists a mechanism that temporally coordinates AN and DIA activation, the amount of AN EMG activity with each breath is not clearly correlated with DIA activation, which may contribute to the high incidence of respiratory dysrhythmias in preterm neonates.

Topics: Diaphragm; Electromyography; Female; Humans; Hypercapnia; Infant; Infant, Newborn; Infant, Premature; Male; Nose; Pulmonary Ventilation; Sleep Stages; Time Factors

Nasal obstruction is associated with abnormal breathing during sleep. To investigate this we measured ventilation and isocapnic hypoxic and rebreathing hypercapnic ventilatory responses in 9 awake normal men, with and without artificial nasal occlusion. Resting breathing frequency was lower (P less than 0.05) with mouth (12.5 +/- 1.0 [SEM]) than with nose (15.1 +/- 1.3 b/min) breathing, due to prolongation (P less than 0.05) of expiratory time with mouth breathing (mouth 3.25 +/- 0.35, nasal breathing 2.41 +/- 0.37 sec). Resting tidal volume was similar for both routes, thus minute ventilation was lower (P less than 0.01) mouth breathing (8.43 +/- 0.44) compared with nose breathing (9.37 +/- 0.47 L/min). Ventilatory responses were greater with mouth than nose breathing both for hypercapnia (mouth 2.29 +/- 0.21, nose 1.58 +/- 0.18 L/min/mm Hg CO2; P less than 0.01) and for hypoxia (mouth 1.08 +/-0.16, nose 0.91 +/- 0.21 L/min/% SaO2; P = 0.10). In 6 subjects measurements were repeated before and after upper airway lignocaine anaesthesia, which abolished the differences in respiratory timing and drive between the breathing routes. It is suggested that there may be upper airway flow receptors which influence respiratory timing.

Topics: Adult; Humans; Hypercapnia; Hypoxia; Male; Mouth Breathing; Nose; Respiration