SMALL BLOOD-SAMPLES FROM EAR-LOBE PUNCTURE: A SUBSTITUTE FOR ARTERIAL PUNCTURE

Optical sensor for remote estimation of CO2 concentration in the blood stream

Speckle pattern analysis become a widespread method for remote sensing of various biomedical parameters. This technique is based on tracking the secondary speckle patterns reflected from a human skin illuminated by a laser beam. Speckle pattern variations can be translated into the corresponding partial carbon dioxide (CO₂) state (High or Normal) in the bloodstream. We present a novel approach for remote sensing of human blood carbon dioxide partial pressure (PCO₂) based on speckle pattern analyses combined with machine learning approach. The blood CO₂ partial pressure is an important indicative parameter for a variety of malfunctions in the human body.

Oxygenated hemoglobin as prognostic marker among patients with systemic sclerosis screened for pulmonary hypertension

Oxygenated hemoglobin (OxyHem) in arterial blood may reflect disease severity in patients with systemic sclerosis (SSc). The aim of this study was to analyze the predictive value of OxyHem in SSc patients screened for pulmonary hypertension (PH). OxyHem (g/dl) was measured by multiplying the concentration of hemoglobin with fractional oxygen saturation in arterialized capillary blood. Prognostic power was compared with known prognostic parameters in SSc using uni- and multivariable analysis. A total of 280 SSc patients were screened, 267 were included in the analysis. No signs of pulmonary vascular disease were found in 126 patients, while 141 patients presented with mean pulmonary arterial pressure ≥ 21 mmHg. Interstitial lung disease (ILD) was identified in 70 patients. Low OxyHem ≤ 12.5 g/dl at baseline was significantly associated with worse survival (P = 0.046). In the multivariable analysis presence of ILD, age ≥ 60 years and diffusion capacity for carbon monoxide (DLCO) ≤ 65% were negatively associated with survival. The combination of low DLCO and low OxyHem at baseline could predict PH at baseline (sensitivity 76.1%). This study detected for the first time OxyHem ≤ 12.5 g/dl as a prognostic predictor in SSc patients. Further studies are needed to confirm these results.

Clinical characterization and possible pathophysiological causes of the Deventilation Syndrome in COPD

In daily routine, many COPD patients report early onset augmented dyspnea following use of NIV (Deventilation Syndrome, DVS) as a negative side-effect. The aim of this study is the clinical characterization and concrete definition of DVS. This monocenter prospective observational study collected demographic, physiologic and symptomatic data from 67 in-patients with severe COPD Gold III–IV and chronic hypercapnic failure before, during and after use of an established NIV. During their inpatient follow-up, we examined patients during the first hour after termination of nocturnal NIV. DVS was defined by the authors as an increase of ≥ 2 points on the Borg scale during the first 30 min in patients who reported repeated dyspnea after the use of NIV. We monitored cardiovascular and respiratory data and measured diaphragm excursion. Subjective dyspnea was documented by use of the Borg scale and questionnaires. In addition, respirator and demographic data were collected. DVS occurred in 58% of our COPD patient collective, showing predominant emphysema phenotype. Patients with DVS were more severely ill than non-DVS concerning bronchial obstruction (FEV1 0.6 vs. 0.8 l, p < 0.05) and hypercapnia during spontaneous breathing (pre NIV pCO₂: 54.5 vs. 49.3 mmHg, p < 0.02). DVS patients showed significantly higher respiratory rates (RR) (20.1 vs. 18.1/min p < 0.05) after termination of NIV. This trial characterizes and defines early onset augmented dyspnea after the use of NIV, referred to as DVS. It is hereby brought to attention as a frequent side effect of long-term home ventilation and possible pathophysiologic mechanisms are elucidated.

Prognostic Value of Oxygenated Hemoglobin Assessed during Acute Exacerbations of Chronic Pulmonary Disease

BACKGROUND

Oxygenated hemoglobin(OxyHem) is a simple-to-measure marker of oxygen content capable of predicting all-cause mortality in stable chronic obstructive pulmonary disease (COPD).

OBJECTIVES

We aimed to analyze its predictive value during acute exacerbations of COPD (AECOPD).

METHODS

In this retrospective study, data from 227 patients discharged after severe AECOPD at RoMed Clinical Center Rosenheim, Germany, between January 2012 and March 2018, was analyzed. OxyHem (hemoglobin concentration [Hb] × fractional SpO2, g/dL) was calculated from oxygen saturation measured by pulse oximetry and hemoglobin assessed within 24 h after admission. The follow-up (1.7 ± 1.5 years) covered all-cause mortality, including readmissions for severe AECOPD.

RESULTS

During the follow-up period, 127 patients died, 56 due to AECOPD and 71 due to other reasons. Survivors and non-survivors showed differences in age, FVC % predicted, C-reactive protein, hemoglobin, Cr, Charlson Comorbidity Index (CCI), and OxyHem (p < 0.05 each). Significant independent predictors of survival were BMI, Cr or CCI, FEV1 % predicted or FVC % predicted, Hb, or OxyHem. The predictive value of OxyHem (p = 0.006) was superior to that of Hb or SpO2 and independent of oxygen supply during blood gas analysis. OxyHem was also predictive when using a cutoff value of 12.1 g/dL identified via receiver operating characteristic curves in analyses including either the CCI (hazard ratio 1.85; 95% CI 1.20, 2.84; p = 0.005) or Cr (2.04; 95% CI 1.35, 3.10; p = 0.001) as covariates.

CONCLUSION

The concentration of OxyHem provides independent, easy-to-assess information on long-term mortality risk in COPD, even if measured during acute exacerbations. It therefore seems worth to be considered for broader clinical use.

Associations of oxygenated hemoglobin with disease burden and prognosis in stable COPD: Results from COSYCONET

We studied whether in patients with stable COPD blood gases (BG), especially oxygenated hemoglobin (OxyHem) as a novel biomarker confer information on disease burden and prognosis and how this adds to the information provided by the comorbidity pattern and systemic inflammation. Data from 2137 patients (GOLD grades 1–4) of the baseline dataset of the COSYCONET COPD cohort were used. The associations with dyspnea, exacerbation history, BODE-Index (cut-off ≤2) and all-cause mortality over 3 years of follow-up were determined by logistic and Cox regression analyses, with sex, age, BMI and pack years as covariates. Predictive values were evaluated by ROC curves. Capillary blood gases included SaO₂, PaO₂, PaCO₂, pH, BE and the concentration of OxyHem [haemoglobin (Hb) x fractional SaO₂, g/dL] as a simple-to-measure correlate of oxygen content. Inflammatory markers were WBC, CRP, IL-6 and -8, TNF-alpha and fibrinogen, and comorbidities comprised a broad panel including cardiac and metabolic disorders. Among BG, OxyHem was associated with dyspnoea, exacerbation history, BODE-Index and mortality. Among inflammatory markers and comorbidities, only WBC and heart failure were consistently related to all outcomes. ROC analyses indicated that OxyHem provided information of a magnitude comparable to that of WBC, with optimal cut-off values of 12.5 g/dL and 8000/µL, respectively. Regarding mortality, OxyHem also carried independent, additional information, showing a hazard ratio of 2.77 (95% CI: 1.85–4.15, p < 0.0001) for values <12.5 g/dL. For comparison, the hazard ratio for WBC > 8000/µL was 2.33 (95% CI: 1.60–3.39, p < 0.0001). In stable COPD, the concentration of oxygenated hemoglobin provided additional information on disease state, especially mortality risk. OxyHem can be calculated from hemoglobin concentration and oxygen saturation without the need for the measurement of PaO₂. It thus appears well suited for clinical use with minimal equipment, especially for GPs.

Improving the sampling technique of arterialized capillary samples to obtain more accurate PaO2 measurements

Arterialized earlobe capillary blood samples (ELCS) have been used as a measurement of blood gas status for over 20 years. There is general acceptance that there is a strong correlation and limits of agreement between arterial and arterialized blood samples with respect to pH and PaCO2. Although the correlation between the arterial and arterialized PaO2 is good, the limits of agreement poor. Our aim was to improve the accuracy of this technique in the measurement of PaO2 by simultaneously monitoring the oxygen saturation by pulse oximetry whilst taking an ELCS. We hypothesize that significant discrepancies between the SaO2 and SpO2 highlight either a poorly arterialized sample or an over aerated sample from air bubbles. We compared the SpO2 with the SaO2 of an arterial sample from 27 inpatients. We used the limits of agreement between these samples to define the degree of discordance we would accept between SaO2 and SpO2 before repeat ELCS. Subsequently, 252 consecutive patients attending our respiratory physiology unit over a six-month period had an ELCS and simultaneous SpO2.If there was a discrepancy between SaO2 and SPO2 of > 2% the ELCS was repeated. There was a good correlation and limits of agreement between the SPO2 and arterial SaO2 (r = 0.97, mean difference + 95% limits of agreement: 0.34 + 2.68). A difference of more than 2% between arterialized SaO2 and SpO2 was identified in 21 patients out of 252 (8.3%) with SaO2 higher in two and lower in 19 (r = 0.96, mean difference +95% limits of agreement: 0.66 + 3.1). Repeat ELCS of these 21 samples reduced this discrepancy improving the concordance of the measurements (r = 0.98, mean difference + 95% limits of agreement: 0.47 + 1.0). In one case a difference of 3% remained between the saturations. We conclude that the addition of simultaneous pulse oximetry with ELCS will identify rogue measurements in about 8% of cases highlighting the need for repeat samples and thus increasing the accuracy of the measurement of PaO2 by ELCS.

[Monitoring of pCO2 during ventilation]

Respiratory insufficiency type 2 (ventilatory failure) is characterized by hypercapnia due to alveolar hypoventilation. Therefore, the monitoring of pCO2 is essential for diagnostic and surveillance purposes. Various techniques which differ in the way of measurement (e.g., invasive/noninvasive, continuous/noncontinuous) and their indication are available. Arterial blood gas analysis (ABG) as an invasive procedure is the gold standard procedure and is mostly used in emergency medicine or intensive care units (ICUs). Another method to evaluate pCO2 is capillary blood gas analysis (CBG). Furthermore, endtidal pCO2-(PetCO2) and transcutaneous CO2-measurement (PtcCO2) are able to continuously and noninvasively monitor pCO2. PetCO2 is mostly used in the field of anesthesiology during general anesthesia and is integrated in many ventilators, also in ICUs. However, PetCO2 is limited in monitoring pCO2 in patients with lung disease and it is only reasonably usable in invasively ventilated patients. Transcutaneous pCO2 (PtcCO2) is available as an alternative, especially in chronic respiratory failure and to diagnose hypoventilation in sleep-related breathing disorders, and it has substantial advantages in these indications compared to discontinuous measurements, e.g., blood gas analysis. The various methods to monitor pCO2 are generally used synergistically in clinical practice.

Arterialised earlobe capillary blood gases in the COPD population

Arterialised ear lobe capillary blood (ELCB) gas sampling is a widely used clinical procedure undertaken across both primary and secondary care settings. The prevalence of this sampling method has grown among health professionals, coupled with a growing demand for domiciliary oxygen therapy in the UK, in particular for those who have chronic obstructive pulmonary disease (COPD). Research studies supporting arterialised ELCB gas sampling show inconsistencies in technique, and a survey of respiratory nurses' current practice demonstrated wider inconsistencies. In the absence of national clinical guidelines to direct this practice, and an acknowledged and accepted under-calculation of partial pressure of oxygen, this article investigates the sampling method used to obtain arterialised ELCB gas sampling and consequently questions its reliability in practice.

Prediction of arterial blood gas values from arterialized earlobe blood gas values in patients treated with mechanical ventilation

Background/Objective:

Arterial blood gas (ABG) analysis is useful in evaluation of the clinical condition of critically ill patients; however, arterial puncture or insertion of an arterial catheter may sometimes be difficult and cause many complications. Arterialized ear lobe blood samples have been described as adequate to gauge gas exchange in acute and chronically ill pediatric patients.

Purpose:

This study evaluates whether pH, partial pressure of oxygen (PO₂), partial pressure of carbon dioxide (PCO₂), base excess (BE), and bicarbonate (HCO₃) values of arterialized earlobe blood samples could accurately predict their arterial blood gas analogs for adult patients treated by mechanical ventilation in an intensive care unit (ICU).

Setting:

A prospective descriptive study

Methods:

Sixty-seven patients who were admitted to ICU and treated with mechanical ventilation were included in this study. Blood samples were drawn simultaneously from the radial artery and arterialized earlobe of each patient.

Results:

Regression equations and mean percentage-difference equations were derived to predict arterial pH, PCO₂, PO₂, BE, and HCO₃-values from their earlobe analogs. pH, PCO₂, BE, and HCO₃ all significantly correlated in ABG and earlobe values. In spite of a highly significant correlation, the limits of agreement between the two methods were wide for PO₂. Regression equations for prediction of pH, PCO₂, BE, and HCO3- values were: arterial pH (pHa) = 1.81+ 0.76 × earlobe pH (pHe) [r = 0.791, P < 0.001]; PaCO₂ = 1.224+ 1.058 × earlobePCO₂ (PeCO₂) [r = 0.956, P < 0.001]; arterial BE (BEa) = 1.14+ 0.95 × earlobe BE (BEe) [r= 0.894, P < 0.001], and arterial HCO₃- (HCO₃-a) = 1.41+ earlobe HCO₃(HCO₃-e) [r = 0.874, P < 0.001]. The predicted ABG values from the mean percentage-difference equations were derived as follows: pHa = pHe × 1.001; PaCO₂ = PeCO₂ × 0.33; BEa = BEe × 0.57; and HCO₃-a = HCO₃-e × 1.06.

Conclusions:

Arterialized earlobe blood gas can accurately predict the ABG values of pH, PCO₂, BE, and HCO₃- for patients who do not require regular continuous blood pressure measurements and close monitoring of arterial PO₂ measurements.

Comparison of fingertip to arterial blood samples at rest and during exercise

OBJECTIVE

The purpose was to determine whether arterialized fingertip blood-gas samples are comparable to arterial samples at rest and at exercise.

DESIGN

Repeated measures, with subjects serving as their own controls.

SETTING

Department of Anesthesia, Montreal General Hospital, Montreal, Quebec, Canada, (January to April 2004).

PARTICIPANTS

Fifteen healthy men (age = 25 +/- 4 y; weight = 76.4 +/- 11.4 kg; height = 180.7 +/- 8.0 cm; peak oxygen uptake or VO2peak = 46.0 +/- 9.0 mL . kg . min).

MAIN OUTCOME MEASURES

Arterial blood gases, metabolites, electrolytes.

RESULTS

Blood sampled simultaneously from the radial artery and warmed fingertip at rest and during 2 levels of exercise (vigorous 181 W or 70% VO2peak; maximal 261 W or 100% VO2peak) on a electronically braked ergometer. Arterial partial pressure of oxygen in blood combining rest and the 2 exercise levels was on average 13.6 +/- 9.0 mm Hg higher than arterialized fingertip samples, with the largest difference occurring at rest (18.8 +/- 6.5 mm Hg; 95% CI = 15.5, 22.1) and the smallest difference occurring at the highest level of exercise (8.3 +/- 9.2 mm Hg; 95% CI = 3.6, 13.0; P < 0.05). The pattern for oxyhemoglobin saturation was the same, showing statistical differences between the sampling sites with the differences reduced at the highest exercise intensity. In contrast, there was no difference in arterial and arterialized partial pressure of carbon dioxide in blood (-1.0 +/- 1.5 mm Hg; 95% CI = -1.4, -0.6), or plasma lactate, glucose, pH, hemoglobin, and electrolytes between both sampling sites at rest or at the 2 exercise levels.

CONCLUSION

Arterialized fingertip blood samples at rest and during exercise can predict arterial carbon dioxide pressure, and can predict arterial plasma lactate, glucose, pH, hemoglobin, and electrolytes; but not arterial oxyhemoglobin saturation or arterial oxygen pressure.

The clinical utility of arterialized earlobe capillary blood in the assessment of patients for long-term oxygen therapy

The prescription of long-term oxygen (LTOT) is underpinned by the measurement of arterial PO2, generally obtained by radial artery puncture. This test is commonly associated with patient discomfort and a test that is reliable, well-tolerated and non-invasive would be advantageous. Cutaneous oximetry has not proved sufficiently accurate. Arterialized earlobe capillary sampling has been proposed, with some authors stating that it is under-utilized. However, to date studies have yielded conflicting results and the clinical utility remains uncertain. Our regional oxygen service based at a specialist respiratory hospital undertook a prospective study of consecutive patients with chronic respiratory disease undergoing assessment for LTOT. Simultaneous radial artery and arterialized earlobe sampling was performed. Rigorous steps were taken to ensure optimal arterialization of the earlobe samples. Agreement between arterial and arterialized PO2 and PCO2 was compared using the Bland-Altman method. One hundred patients were studied. Procedural difficulties (insufficient sample or air in sample) were similar for both procedures, however clotting occurred more frequently in arterialized earlobe samples. Sixty-four sample pairs were available for comparison. The bias and limits of agreement between arterialized and arterial PO2 were wide, mean (+/- 2 SD), -048 (-2.05-1.09) kPa. The bias and limits of agreement for PCO2 were smaller. Using the absolute criterion (arterial PO2 < 7.3 kPa), 9/55 (16%) patients would receive oxygen inappropriately based on the arterialized earlobe sample. Conversely, no patients would have been denied LTOT. Radial artery puncture gave rise to significantly greater discomfort (P < 0.0001) and level of concern (P < 0.0001). Patient preference strongly favoured arterialized earlobe sampling. However, despite rigorous attention to arterialization earlobe sampling was insufficiently accurate to replace radial artery puncture in the prescription of LTOT.

Comparison of arterial and venous blood gas values in the initial emergency department evaluation of patients with diabetic ketoacidosis

STUDY OBJECTIVE

To determine whether venous blood gas values can replace arterial gas values in the initial emergency department evaluation of patients with suspected diabetic ketoacidosis.

METHODS

This prospective comparison was performed in an adult university teaching hospital ED. Samples for arterial and venous blood gas analysis were obtained during initial ED evaluations. The venous gas samples were collected with samples for other blood tests at the time of intravenous line insertion. Both arterial and venous samples were obtained before the initiation of treatment.

RESULT

Data from 44 episodes of diabetic ketoacidosis in 38 patients were analyzed. Laboratory findings of those patients with diabetic ketoacidosis were as follows (mean +/- SD): arterial pH, 7.20 +/- 14; venous pH, 7.17 +/- 13; serum glucose, 33.8 +/- 16 mmol/L (609 +/- 288 mg/dL); arterial HCO3-, 11.0 +/- 6.0 mmol; venous HCO3-, 12.8 +/- 5.5 mmol/L; serum CO2, 11.8 +/- 5.0 mmol/L; and anion gap, 26.7 +/- 7.6 mmol/L. The mean difference between arterial and venous pH values was 0.03 (range 0.0 to 0.11). Arterial and venous pH results (r = .9689) and arterial and venous HCO3- results (r = .9543) were highly correlated and showed a high measure of agreement.

CONCLUSION

Venous blood gas measurements accurately demonstrate the degree of acidosis of adult ED patients presenting with diabetic ketoacidosis.

Continuous monitoring of lactate during exercise in humans using subcutaneous and transcutaneous microdialysis

We have evaluated the possibility of monitoring the plasma lactate concentration in human volunteers during cycle ergometer exercise using subcutaneous and transcutaneous microdialysis. In transcutaneous microdialysis, the relative increase in dialysate lactate concentration exceeded that of plasma lactate concentration by a factor of 6 during exercise due to exercise-induced lactate secretion in sweat. During exercise the subcutaneous microdialysis dialysate lactate concentration underestimated the plasma lactate concentration possibly due to diffusion limitation or adipose tissue lactate production. While it was demonstrated that microdialysis can be used for on-line lactate monitoring, neither subcutaneous nor transcutaneous dialysate lactate concentration were linearly related to the plasma lactate concentration during exercise, and it was found therefore that it was not possible to monitor directly plasma lactate concentration during exercise.

Arterialised earlobe blood gas analysis: an underused technique

BACKGROUND

Techniques for sampling arterialised capillary blood from the finger pulp and the earlobe were first described over two decades ago but, although close agreement between arterial values and earlobe samples has been demonstrated in normal subjects, this technique is not in common usage.

METHODS

Forty patients with chronic lung disease and a wide range of arterial blood gas values were studied. Simultaneous earlobe and arterial samples were drawn with the patient at rest and analysed in the same blood gas analyser. The respiratory function laboratory staff in 50 UK hospitals with a respiratory department were telephoned and asked whether the technique was used in their hospital and the reasons, if known, for not adopting it.

RESULTS

Earlobe and arterial blood gas tensions agreed closely over a wide range of values of arterial pH, PCO2 (mean difference 0.21, 95% confidence intervals -0.24 to +0.67 kPa) and PO2 (mean difference -0.17, 95% confidence intervals -1.09 to +0.75 kPa), especially at arterial PO2 values lower than 8 kPa. Of 50 UK centres surveyed 18% used the arterialised earlobe technique and 4% had plans to introduce it. Reasons for not using it were lack of knowledge in 64%, no blood gas analyser in 6%, the technique was considered inaccurate in 4%, and insufficient staff in 4%.

CONCLUSIONS

Although earlobe blood gas analysis is sufficiently accurate to be reliably substituted for arterial sampling in routine clinical practice, most centres in the UK do not use the technique. The main reasons for this appear to be lack of knowledge of its existence and uncertainty over its accuracy.

A comparison of arterial and non-arterialized capillary blood gases in diabetic ketoacidosis

The results of acid-base and blood gas estimations in arterial and non-arterialized capillary blood have been compared in samples obtained simultaneously from patients presenting with diabetic ketoacidosis. Highly significant correlations were obtained for pH, pCO2 and bicarbonate measurements. Small but significant differences were observed with capillary pH slightly lower and capillary pCO2 and bicarbonate slightly higher than arterial values. These differences were of no clinical significance. Non-arterialized capillary samples are a reliable indicator of acid-base status in this form of metabolic acidosis and are preferable to repeated arterial puncture.

Changes in red blood cell oxygen transport in diabetic pregnancy

Parameters of red cell oxygen transport were studied in 23 nonsmoking, insulin-dependent diabetic women and 20 nonsmoking healthy women late during pregnancy. In the pregnant diabetic women, arterial oxygen saturation (SAT) and arterial oxygen tension were significantly decreased. SAT correlated inversely with hemoglobin Alc (Hb Alc) (diabetic women: r = -0.43, p less than 0.05; total material: r = 0.66, p less than 0.001). Red blood cell 2,3-diphosphoglycerate (2,3-DPG) was significantly increased in the pregnant diabetic women (p less than 0.01), but the 2,3-DPG-induced change in hemoglobin-oxygen affinity was impaired. P50 (oxygen affinity, i.e., Po2 at 50% oxygen saturation) at actual pH correlated inversely with Hb Alc of the diabetic women (r = -0.45, p less than 0.05). The suggestion is made that, in diabetic pregnancy, particularly in poorly regulated cases, fetal hypoxia may be an important factor of the increased risk of intrauterine fetal death.

A two-compartment model of blood acid-base state at constant or variable temperature

Information available in the literature on the acid-base properties of oxygenated mammalian blood at a constant or variable temperature was put together into a synthetic model; this also aimed at reconciling the single compartment descriptions of acid-base vs temperature relationships in closed ('anaerobic') conditions with the standard dual compartment analysis of isothermal titrations. Experimental values for the concentrations of blood constituents, buffer dissociation constants, etc. were introduced into the set of physicochemical equations governing the steady-state distribution of CO2, electrolytes and water between plasma and red cells. Design of the model was such as to permit monitoring of all variables (e.g. concentrations) throughout any simulated acid-base transformation. A fairly good fit was obtained between model predictions and experimentally-determined relationships or quantities not introduced into the model from the start. Applications to variable temperature titration and to the effects of changes in blood composition or osmolality are presented. The latter underline the implicit assumptions made by neglecting such variables in current presentations of blood acid-base state.

Comparison of cardiorespiratory effects of terbutaline and salbutamol aerosols in patients with reversible airways obstruction

Harris, L. (1973).Thorax, 28, 592-595. Comparison of cardiorespiratory effects of terbutaline and salbutamol aerosols in patients with reversible airways obstruction. The effects of pressurized aerosol administration of terbutaline were compared with those of salbutamol in 14 patients with at least 20% reversibility of airways obstruction. The two drugs were found to be equipotent bronchodilators in the dosage used. Salbutamol was found to produce significant increases in minute ventilation, physiological dead space/tidal volume ratio, and ventilatory equivalent for oxygen, with significant falls in arterial oxygen tension and heart rate. Terbutaline did not induce significant changes in any of these variables. These results suggest that terbutaline is less likely than salbutamol to have an adverse effect upon ventilation-perfusion relationships.

Effects of isoprenaline plus phenylephrine by pressurized aerosol on blood gases, ventilation, and perfusion in chronic obstructive lung disease

The effects of a combined isoprenaline-phenylephrine inhalant in chronic obstructive lung disease were assessed in 23 patients. Significant changes occurred in blood gas tensions after inhalation, together with an overall improvement in ventilation/perfusion ratios. Cardiac output and physiological shunt were not significantly increased. Hence the addition of phenylephrine probably prevents the increase of hypoxaemia which may result from the disproportionate ventilation/perfusion ratio produced by sympathomimetics or xanthines used alone. The combination aerosol has a satisfactory bronchodilator effect, and is additionally safe if used by a severely hypoxic patient unaware of the seriousness of his condition.